Author(s) ID,Title,Year,DOI,Link,Abstract
"6701681289;7004109472;","Simulation of east African precipitation patterns with the regional climate model CLM",2008,"10.1127/0941-2948/2008/0299","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049115411&doi=10.1127%2f0941-2948%2f2008%2f0299&partnerID=40&md5=c3b1d447f22df667f8632fe37ea0fe39","Climate simulations for East Africa have been performed with the regional climate model CLM. Here we evaluate the quality of simulated precipitation by comparing it with observations. Different schemes for convection and cloud ice have been tested in order to determine the configuration with best representation of precipitation patterns for the region. The simulated seasonal behaviour of precipitation is reasonable in all configurations, whereas absolute values are strongly influenced by the selected schemes. Best agreement with observations is achieved with the Tiedtke mass-flux convection scheme in combination with a two-category cloud ice scheme, that considers cloud ice as an additional solid form of water. With the Kain-Fritsch convection scheme the model generally overestimates precipitation. Regional differences are discussed. © by Gebrüder Borntraeger 2008."
"11939918300;57198857563;7003748648;","Towards climate simulations at cloud-resolving scales",2008,"10.1127/0941-2948/2008/0303","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049106433&doi=10.1127%2f0941-2948%2f2008%2f0303&partnerID=40&md5=e78fbb5d5049688eff436784c1be1187","This study explores the potential added-value of applying cloud-resolving resolution to climate simulations. A month-long (July 2006) integration is performed with the CCLM on a convection-resolving grid of 2.2-km (0.02°) mesh size spanning the whole Alpine region. The initial and lateral boundary conditions stem from a coarser-resolution 25-krn (0.22°) CCLM integration. Comparison to observations indicates that the cloud-resolving simulation is able to capture the overall precipitation distribution and evolution. With respect to its driving lower-resolution integration, the cloud-resolving resolution yields a more accurate spatial localization of the precipitation maxima, reduces the cold bias, and especially reproduces a better timing of the convective diurnal cycle. The explicit resolution delays the onset of convective precipitation by about 2 h, shifts the time of peak precipitation by a similar period, and slows down the decay of convective activity in the afternoon. In return, the integration shows a tendency to underestimate the afternoon convective rainfalls, particularly under weak synoptic and/or orographic forcing. This latter effect might be improved by modifying the treatment of subgrid-scale clouds in the model. © by Gebrüder Borntraeger 2008."
"7006038622;6602803020;22939073500;6506604391;6506126977;","Quality of a climate reconstruction for the CADSES regions",2008,"10.1127/0941-2948/2008/0318","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049123108&doi=10.1127%2f0941-2948%2f2008%2f0318&partnerID=40&md5=cb4dc52edb02a641d0007d0aee488c60","We used the regional climate model CCLM 4 to reconstruct the climate over the CADSES regions for the period 1961-2000. This most recent model version is currently still in a test phase. The simulation quality for this part of the entire simulation area is exemplarily analyzed by using a small but representative subset of model variables. Mean sea level pressure is chosen as an indicator for the behavior of the near-surface dynamics. Furthermore, the two regional variables 2 m temperature and precipitation are evaluated, which are of relevance for hydrological applications. For additional analyses to identify sources of uncertainty, we used soil moisture and cloudiness. Altogether, the accuracy of the simulation results can be judged as being in good agreement with the results of similar simulations by other regional climate models over Europe. Area-averaged monthly mean 2 m temperatures during winter show a cold bias of about -2 K. The simulated mean sea level pressure is with a bias of about 2 hPa slightly too high compared to the used reference data set. Although cloud cover evaluation hints at insufficiencies in the corresponding parameterization, further analyses are required to unambiguously identify the causes for this cold bias. During summer, higher 2 m temperatures linked to reduced precipitation are identified in nearly identical regions over southern and southeastern Europe. Further analyses of soil moisture evolution and cloud cover give evidence for a source of uncertainty in the surface hydrological scheme. Altogether, the detected differences do not exceed the typical ranges of uncertainty in comparable regional climate simulations over Europe. For input in hydrological applications, however, the uncertainties produced by the CCLM simulation described here have to be reduced in the medium term. © by Gebrüder Borntraeger 2008."
"6603566552;7202313091;","Formation mechanism of an intensified cold air mass in the middle troposphere over East Siberia in December 2005 using a regional climate model",2008,"10.2151/jmsj.86.773","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049110143&doi=10.2151%2fjmsj.86.773&partnerID=40&md5=8ed8af4c299adfcb640f2d5e2a981e31","The formation mechanism of an intensified cold air mass around East Siberia in December 2005, which brought a heavy amount of snow over northern Japan, is investigated using a regional climate model. The strong cold air mass is simulated by the CTL run with full diabatic processes. However, the experiment with the adiabatic process (ADIABATIC run), which is conducted to investigate the effects of the atmospheric response and the advection of large-scale atmospheric circulation from the outside of the calculation domain, does not simulate the intensified cold air mass below 235 K at 500 hPa. Another sensitivity experiment with diabatic heating processes, except for surface heat fluxes (NO-SFH run), reproduces the intensified cold air mass due to the diabatic heating process in the middle to upper troposphere. The intensification and maintenance of the cold low in the typical events cannot be reproduced by the experiment without radiation process (NO-RAD-R run), while the NO-SFH run can simulate those important features of the cold low. These results indicate that the radiation process in the middle to upper troposphere is indispensable to intensify the cold air mass below 235 K at 500 hPa. From the satellite images, it is evident that the formation of clouds is accompanied by a cold low in the middle troposphere. It is speculated that the clouds are the source of the cooling due to the infrared cooling process, which may intensify the cold low. Therefore, the infrared cooling of the clouds is supposed to be the primary process in the intensification of the cold air mass in December 2005. ©2008, Meteorological Society of Japan."
"7006575272;6602948135;7202119915;","The diurnal cycle of clouds and precipitation along the Sierra Madre Occidental observed during NAME-2004: Implications for warm season precipitation estimation in complex terrain",2008,"10.1175/2008JHM939.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649108150&doi=10.1175%2f2008JHM939.1&partnerID=40&md5=9c742464ee5ca597bce9ef04ad16ac92","This study examines the spatial and temporal variability in the diurnal cycle of clouds and precipitation tied to topography within the North American Monsoon Experiment (NAME) tier-I domain during the 2004 NAME enhanced observing period (EOP, July-August), with a focus on the implications for high-resolution precipitation estimation within the core of the monsoon. Ground-based precipitation retrievals from the NAME Event Rain Gauge Network (NERN) and Colorado State University-National Center for Atmospheric Research (CSU-NCAR) version 2 radar composites over the southern NAME tier-I domain are compared with satellite rainfall estimates from the NOAA Climate Prediction Center Morphing technique (CMORPH) and Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks (PERSIANN) operational and Tropical Rainfall Measuring Mission (TRMM) 3B42 research satellite estimates along the western slopes of the Sierra Madre Occidental (SMO). The rainfall estimates are examined alongside hourly images of high-resolution Geostationary Operational Environmental Satellite (GOES) 11-μm brightness temperatures. An abrupt shallow to deep convective transition is found over the SMO, with the development of shallow convective systems just before noon on average over the SMO high peaks, with deep convection not developing until after 1500 local time on the SMO western slopes. This transition is shown to be contemporaneous with a relative underestimation (overestimation) of precipitation during the period of shallow (deep) convection from both IR and microwave precipitation algorithms due to changes in the depth and vigor of shallow clouds and mixed-phase cloud depths. This characteristic life cycle in cloud structure and microphysics has important implications for ice-scattering microwave and infrared precipitation estimates, and thus hydrological applications using high-resolution precipitation data, as well as the study of the dynamics of convective systems in complex terrain. © 2008 American Meteorological Society."
"12138847300;6602736210;","The effect of changes of urban surfaces on rainfall phenomenon as determined by a non-hydrostatic mesoscale model",2008,"10.2151/jmsj.86.733","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049120778&doi=10.2151%2fjmsj.86.733&partnerID=40&md5=9de65c1fe801c0d6d4b298346eae7a12","A non-hydrostatic, mesoscale model, LOCALS, is used to investigate the effect of land surface changes on precipitation in an urban area. The horizontal mesh used in the model is approximately 5 km and the domain includes Tokyo and central Japan. Land surfaces identified as pavement or urban are transformed into forested land and model simulations are performed for both the current urban land surface and the hypothetical forested land surface. Detailed analysis is performed for two sample cases. On 5 August 2003, increased heating by the urban surfaces increases the height of the urban boundary layer resulting in much more rainfall. On 25 July 2001, air that is advected over Tokyo but forms a precipitating cloud away from the urban core carries less moisture and therefore produces less rainfall. These case studies suggest that changes to land surface types in urban areas may increase or decrease rainfall in the urban area and further research is necessary before it is possible to generalize these results. ©2008, Meteorological Society of Japan."
"23088693800;36992169200;7003942283;","Ice nucleation activity of bacteria isolated from snow compared with organic and inorganic substrates",2008,"10.1071/EN08055","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57849131260&doi=10.1071%2fEN08055&partnerID=40&md5=6d4968b71128a5d55ed94cf26a68c589","Environmental context. Biological ice nucleators have been found to freeze water at very warm temperatures. The potential of bio-aerosols to greatly influence cloud chemistry and microphysics is becoming increasingly apparent, yet detailed knowledge of their actual role in atmospheric processes is lacking. The formation of ice in the atmosphere has significant local, regional and global influence, ranging from precipitation to cloud nucleation and thus climate. Ice nucleation tests on bacteria isolated from snow and laboratory-grown bacteria, in comparison with those of known organic and inorganic aerosols, shed light on this issue. Abstract. Ice nucleation experiments on bacteria isolated from snow as well as grown in the laboratory, in comparison with those of known organic and inorganic aerosols, examined the importance of bio-aerosols on cloud processes. Snow samples were collected from urban and suburban sites in the greater Montreal region in Canada (4528′N, 7345′W). Among many snow bacterial isolates, eight types of bacterial species, none belonging to known effective ice nucleators such as Pseudomonas or Erwinia genera, were identified to show an intermediate range of ice nucleation activity (12.9 1.3C to 17.5 2.8C). Comparable results were also obtained for molten snow samples and inorganic suspensions (kaolin and montmorillonite) of buffered water solutions. The presence of organic molecules (oxalic, malonic and succinic acids) had minimal effect (<2C) on ice nucleation. Considering experimental limitations, and drawing from observation in snow samples of a variety of bacterial populations with variable ice-nucleation ability, a shift in airborne-species population may significantly alter glaciation processes in clouds. © CSIRO 2008."
"6701404949;15729555500;7102638371;8550634300;","Interannual variability of the coastal fog at Fray Jorge relict forests in semiarid Chile",2008,"10.1029/2008JG000709","https://www.scopus.com/inward/record.uri?eid=2-s2.0-61749095362&doi=10.1029%2f2008JG000709&partnerID=40&md5=f2e3e8649c5b34326f26b6bee46fed21","The coastal mountains of semiarid Chile are punctuated by patches of fog-dependent evergreen forests. Fog episodes often occur when the prominent coastal topography intercepts a well developed deck of stratocumulus (Sc) off north central Chile. A 22-year record of ground-based fog observations at Fray Jorge Biosphere Reserve (FJBR, 30°S), atmospheric reanalysis and satellite derived low cloud amount are used to document the annual cycle and interannual variability of fog frequency there. The number of foggy days minimizes during austral winter and then increases rapidly to reach a maximum in spring (the growing season of FJBR trees). The mean annual cycle of the fog-frequency follows closely the annual cycle of the nearby marine Sc amount and lower tropospheric stability (LTS). The springtime fog frequency, nearby marine cloud amount and LTS are also well correlated at interannual timescales. Colder than normal sea surface temperatures and warmer than normal air temperatures aloft near 30°S strengthen the temperature inversion and lead to a more persistent cloud deck and higher than normal fog frequency at FJBR. La Niña years produce temperature anomalies very similar to the pattern described before and consequently they are associated with higher than normal springtime fog frequency at FJBR. Conversely, El Niño years are associated with less foggy conditions at FJBR. Interestingly, El Niño-Southern Oscillation (ENSO) related rainfall anomalies in north central Chile are opposite to ENSO-related anomalies in fog-frequency. We discuss the overall impact of ENSO in FJBR ecosystems as well as the prospects of FJBR in future climate scenarios driven by increased greenhouse gases. Copyright 2008 by the American Geophysical Union."
"57206531303;23095654600;8636656300;7103245428;7101791974;57217768706;55474691000;57205497429;","Remote sensing data assimilation for a prognostic phenology model",2008,"10.1029/2008JG000781","https://www.scopus.com/inward/record.uri?eid=2-s2.0-61749102353&doi=10.1029%2f2008JG000781&partnerID=40&md5=d970d929a302b1a3eebabdf2de63e361","Predicting the global carbon and water cycle requires a realistic representation of vegetation phenology in climate models. However most prognostic phenology models are not yet suited for global applications, and diagnostic satellite data can be uncertain and lack predictive power. We present a framework for data assimilation of Fraction of Photosynthetically Active Radiation absorbed by vegetation (FPAR) and Leaf Area Index (LAI) from the MODerate Resolution Imaging Spectroradiometer (MODIS) to constrain empirical temperature, light, moisture and structural vegetation parameters of a prognostic phenology model. We find that data assimilation better constrains structural vegetation parameters than climate control parameters. Improvements are largest for drought-deciduous ecosystems where correlation of predicted versus satellite-observed FPAR and LAI increases from negative to 0.7-0.8. Data assimilation effectively overcomes the cloud- and aerosol-related deficiencies of satellite data sets in tropical areas. Validation with a 49-year-long phenology data set reveals that the temperature-driven start of season (SOS) is light limited in warm years. The model has substantial skill (R = 0.73) to reproduce SOS inter-annual and decadal variability. Predicted SOS shows a higher inter-annual variability with a negative bias of 5-20 days compared to species-level SOS. It is however accurate to within 1-2 days compared to SOS derived from net ecosystem exchange (NEE) measurements at a FLUXNET tower. The model only has weak skill to predict end of season (EOS). Use of remote sensing data assimilation for phenology model development is encouraged but validation should be extended with phenology data sets covering mediterranean, tropical and arctic ecosystems. Copyright 2008 by the American Geophysical Union."
"26321034100;26321054100;57206531303;7102627515;16444695600;6602371284;56549649300;6603954179;","Quantitative phenological observations of a mixed beech forest in northern Switzerland with digital photography",2008,"10.1029/2007JG000650","https://www.scopus.com/inward/record.uri?eid=2-s2.0-61749104490&doi=10.1029%2f2007JG000650&partnerID=40&md5=aac1b18d343f2535e0025d16a31fdd2a","Vegetation phenology has a strong influence on the timing and phase of global terrestrial carbon and water exchanges and is an important indicator of climate change and variability. In this study we tested the application of inexpensive digital visible-light cameras in monitoring phenology. A standard digital camera was mounted on a 45 m tall flux tower at the Lägeren FLUXNET/CarboEuropeIP site (Switzerland), providing hourly images of a mixed beech forest. Image analysis was conducted separately on a set of regions of interest representing two different tree species during spring in 2005 and 2006. We estimated the date of leaf emergence based on the levels of the extracted red, green and blue colors. Comparisons with validation data were in accordance with the phenology of the observed trees. The mean error of observed leaf unfolding dates compared with validation data was 3 days in 2005 and 3.6 days in 2006. An uncertainty analysis was performed and demonstrated moderate impacts on color values of changing illumination conditions due to clouds and illumination angles. We conclude that digital visible-light cameras could provide inexpensive, spatially representative and objective information with the required temporal resolution for phenological studies. Copyright 2008 by the American Geophysical Union."
"25941200000;","Representing cloud overlap with an effective decorrelation length: An assessment using CloudSat and CALIPSO data",2008,"10.1029/2008JD010391","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62149088871&doi=10.1029%2f2008JD010391&partnerID=40&md5=fd69f64964a16fa35cc6a8144543a7b2","This study commenced testing the hypothesis that a vertically constant, effective, decorrelation length L<inf>cf</inf>* can be used to represent overlap of cloud for the purpose of performing radiative transfer calculations in global climate models. It was assumed that total cloud fraction C resulting from multiple layers of overlapping fractional cloudcan be described as a linear combination of maximum and random overlap, with the weight defined by exp(-Δz/L<inf>cf</inf>*) where Δz is distance between layers. Cloud masks and water contents (CWC) obtained from CloudSat and CALIPSO satellite data, for January 2007, were used to solve for L<inf>cf</inf>*. Benchmark shortwave (SW) and longwave (LW) broadband flux profiles were computed for 500-kM-long retrieved cross-sections via the independent column approximation (ICA). Then L<inf>cf</inf>* was found and used, along with corresponding profiles of cloud fraction and CWCs, in a stochastic cloud generator suitable for use in global climate models (GCMs), and ICA fluxes computed for the generated fields. When clouds were homogenized horizontally, zonal mean bias errors for SW cloud radiative effect (CRE) at the top of atmosphere (TOA) were generally <±3 W m-2, with LW counterparts <2 W m-2, similar to changing cloud particle size by ∼15%. For inhomogeneous clouds, SW CRE biases jumped to typically -5 W m-2 partly because of limitations with the generator. When L<inf>cf</inf>* = 2 km (near global median) was used ubiquitously in the generator, C was overestimated slightly, mostly by clouds above ∼10 km, and CRE errors grew by just ∼10% to 20%. Exposing too much high cloud to space produced local SW heating rate biases of ∼15%. While optimal effective decorrelation lengths differ for SW and LW radiation, which in turn generally differ from L<inf>cf</inf>*, it appears that use of L<inf>cf</inf>* will suffice for both bands. The impact of using L<inf>cf</inf>* in GCMs remains to be seen."
"35454141800;24451351900;7202079615;55495496100;7202149369;35515569200;55537009700;57203180094;7102665424;7404243086;","Vertical cloud properties in the tropical western Pacific Ocean: Validation of the CCSR/NIES/FRCGC GCM by shipborne radar and lidar",2008,"10.1029/2008JD009812","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62149083340&doi=10.1029%2f2008JD009812&partnerID=40&md5=d9582d98b5952695b055fbeb4a83c27d","This study examined the vertical cloud structure over the tropical western Pacific Ocean using 95-GHz radar and lidar data observed from September to December 2001 during the MR01-K05 cruise of the research vessel Mirai. The cloud vertical structure was homogeneous between 6 and 10 km, and the maximum cloud occurrence was 20% and located at 12 km. The mean precipitation occurrence was 11.5% at 1 km. The cloud fraction, radar reflectivity factor, and lidar backscattering coefficient were simulated along the Mirai cruise track using the output from the Center for Climate System Research, University of Tokyo; National Institute for Environmental Studies; and Frontier Research Center for Global Change (CCSR/NIES/FRCGC) general circulation model (GCM). The original output showed the maximum cloud fraction at 15 km; however, after considering attenuation and the minimum sensitivity of the radar, the maximum shifted to 12 km. The model overestimated the cloud fraction above 8 km, with the simulated fraction more than twice as large as the observed fraction. The model overpredicted the frequency of deep convection reaching the upper atmosphere above 12 km. Further, it overestimated precipitation frequency. Simulated radar reflectivity was underestimated throughout the entire altitude range, whereas simulated and observed lidar backscattering were in good agreement above 12 km with subgrid-scale treatment. The ice effective radius of 40 μm and ice water content were reasonable in thin clouds, but the radius was underestimated in other regions. The simulated liquid water content was overestimated. Copyright 2008 by the American Geophysical Union."
"57185381300;7005387538;7003644704;","Glacier melt, air temperature, and energy balance in different climates: The Bolivian Tropics, the French Alps, and northern Sweden",2008,"10.1029/2008JD010406","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62149117560&doi=10.1029%2f2008JD010406&partnerID=40&md5=f7fdcc9f624dda89c1fb55069abc4f5a","This study investigates the physical basis of temperature-index models for three glaciers in contrasting climates: Zongo (16°S, 5050 m, Bolivian Tropics), St Sorlin (45°N, 2760 m, French Alps), and Storglaciären (67°N, 1370 m, northern Sweden). The daily energy fluxes were computed during melt seasons and correlated with each other and with air temperature on and outside the glacier. The relative contribution of each flux to the correlations between temperature and melt energy was assessed. At Zongo, net short-wave radiation controls the variability of the energy balance and is poorly correlated to temperature. On tropical glaciers, temperature remains low and varies little, melt energy is poorly correlated to temperature, and degree-day models are not appropriate to simulate daily melting. At the yearly scale, the temperature is better correlated to the mass balance because it integrates the ablation and the accumulation processes over a long time period. At Sorlin, the turbulent sensible heat flux is greater because of higher temperatures, but melt variability is still controlled by short-wave radiation. Temperature correlates well with melt energy mainly through short-wave radiation, probably because of diurnal advection of warm air from the valley. At Storglaciären, high correlations between temperature and melt energy result from substantial variability of the sensible and latent heat fluxes (which both supply energy to the glacier), and their good correlations with temperature. In the three climates, long-wave irradiance is the main source of energy, but its variability is small and poorly correlated to the temperature mainly because cloud emissions dominate its variability. Copyright 2008 by the American Geophysical Union."
"56071122400;36917387900;7408418196;","Effects of multicumulus convective ensemble on East Asian summer monsson rainfall simulation",2008,"10.1029/2008JD009847","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62149099517&doi=10.1029%2f2008JD009847&partnerID=40&md5=0dc8c119c755f02f02f2b76ee338a150","Simulating the Asian summer monsoon is one of the most challenging tasks in climate modeling. In particular, monsoon simulations strongly depend on the cumulus parameterization scheme being used, as attested by many modeling studies. In this paper, the performances of a ""unified multicumulus convective ensemble scheme"" (or unified scheme), Kuo, simplified Arakawa-Schubert, Zhang and McFarlane convective parameterization schemes and moist convective adjustment in simulating the East Asian summer monsoon in a coupled General Circulation Model (GCM) are assessed. In the unified scheme, the latter four individual parameterizations are run in parallel without any modification. Simple average of outputs from each parameterization is then incorporated to the atmospheric model at every time step. Simulations based on these convection schemes during the boreal summer season are compared with observations, focusing on the formation and seasonal evolution of the Meiyu-Changma-Baiu rainband. It is found that the East Asian summer monsoon evolution in the GCM is sensitive to the convective parameterization being used. While the Kuo scheme is able to capture a reasonably strong subtropical front, its mean onset time is about two to three pentads earlier than the observed. Simulations based on the simplified Arakawa-Schubert scheme give a more realistic onset date. However, the model subtropical rainband tends to be confined over land near the coastal region of East Asia. The unified scheme is able to reproduce a prominent East Asian subtropical rainband. Moreover, the seasonal evolution of the rainband is also well captured in the unified scheme simulations. Further diagnostics are carried out to elucidate the role of various circulation elements in the Meiyu-Changma-Baiu front formation. In the western part of the front over land regions, there is robust precursor signal in incoming shortwave radiation before monsoon onset in observations as well as model simulations. Comparison between performances of different convective parameterizations suggests that sensitivity to low-level vorticity can be crucial for the northward migration of the subtropical front and its extension into the open ocean east of southern Japan. Copyright 2008 by the American Geophysical Union."
"24340241400;15726335100;6602806333;","Evaluation of cloud-phase retrieval methods for SEVIRI on Meteosat-8 using ground-based lidar and cloud radar data",2008,"10.1175/2007JAMC1591.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40449096085&doi=10.1175%2f2007JAMC1591.1&partnerID=40&md5=e8ddbd0a0a709ef2eb462d5494c87d64","Three cloud-phase determination algorithms from passive satellite imagers are explored to assess their suitability for climate monitoring purposes in midlatitude coastal climate zones. The algorithms are the Moderate Resolution Imaging Spectroradiometer (MODIS)-like thermal infrared cloud-phase method, the Satellite Application Facility on Climate Monitoring (CM-SAF) method, and an International Satellite Cloud Climatology Project (ISCCP)-like method. Using one year (May 2004-April 2005) of data from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on the first Meteosat Second Generation satellite (Meteosat-8), retrievals of the methods are compared with collocated and synchronized ground-based cloud-phase retrievals obtained from cloud radar and lidar observations at Cabauw, Netherlands. Three aspects of the satellite retrievals are evaluated: 1) instantaneous cloud-phase retrievals, 2) monthly-averaged water and ice cloud occurrence frequency, and 3) diurnal cycle of cloud phase for May-August 2004. For the instantaneous cases, all methods have a very small bias for thick water and ice cloud retrievals (∼5%). The ISCCP-like method has a larger bias for pure water clouds (∼10%), which is likely due to the 260-K threshold leading to misdetection of water clouds existing at lower temperatures. For the monthly-averaged water and ice cloud occurrence, the CM-SAF method is best capable of reproducing the annual cycle, mainly for the water cloud occurrence frequency, for which an almost constant positive bias of ∼8% was found. The ISCCP- and MODIS-like methods have more problems in detecting the annual cycle, especially during the winter months. The difference in annual cycle detection among the three methods is most probably related to the use of visible/near-infrared reflectances that enable a more direct observation of cloud phase. The diurnal cycle in cloud phase is reproduced well by all methods. The MODIS-like method reproduces the diurnal cycle best, with correlations of 0.89 and 0.86 for water and ice cloud occurrence frequency, respectively. © 2008 American Meteorological Society."
"7003875148;24472110700;7003663305;","How well do regional climate models reproduce radiation and clouds in the arctic? An evaluation of ARCMIP simulations",2008,"10.1175/2008JAMC1845.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57649165200&doi=10.1175%2f2008JAMC1845.1&partnerID=40&md5=202a8b28a9dac40acb45e2f82b7e8e7f","Downwelling radiation in six regional models from the Arctic Regional Climate Model Intercomparison (ARCMIP) project is systematically biased negative in comparison with observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment, although the correlations with observations are relatively good. In this paper, links between model errors and the representation of clouds in these models are investigated. Although some modeled cloud properties, such as the cloud water paths, are reasonable in a climatological sense, the temporal correlation of model cloud properties with observations is poor. The vertical distribution of cloud water is distinctly different among the different models; some common features also appear. Most models underestimate the presence of high clouds, and, although the observed preference for low clouds in the Arctic is present in most of the models, the modeled low clouds are too thin and are displaced downward. Practically all models show a preference to locate the lowest cloud base at the lowest model grid point. In some models this happens also to be where the observations show the highest occurrence of the lowest cloud base; it is not possible to determine if this result is just a coincidence. Different factors contribute to model surface radiation errors. For longwave radiation in summer, a negative bias is present both for cloudy and clear conditions, and intermodel differences are smaller when clouds are present. There is a clear relationship between errors in cloud-base temperature and radiation errors. In winter, in contrast, clear-sky cases are modeled reasonably well, but cloudy cases show a very large inter-model scatter with a significant bias in all models. This bias likely results from a complete failure in all of the models to retain liquid water in cold winter clouds. All models overestimate the cloud attenuation of summer solar radiation for thin and intermediate clouds, and some models maintain this behavior also for thick clouds. © 2008 American Meteorological Society."
"7102965584;7202340838;7403931916;6507693951;7005920812;7004547261;","The vertical profile of liquid and ice water content in midlatitude mixed-phase altocumulus clouds",2008,"10.1175/2008JAMC1885.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57649227382&doi=10.1175%2f2008JAMC1885.1&partnerID=40&md5=ebf838467394c65e546ff14dc0d9453e","The microphysical properties of mixed-phase altocumulus clouds are investigated using in situ airborne measurements acquired during the ninth Cloud Layer Experiment (CLEX-9) over a midlatitude location. Approximately 2/3 of the sampled profiles are supercooled liquid-topped altocumulus clouds characterized by mixed-phase conditions. The coexistence of measurable liquid water droplets and ice crystals begins at or within tens of meters of cloud top and extends down to cloud base. Ice virga is found below cloud base. Peak liquid water contents occur at or near cloud top while peak ice water contents occur in the lower half of the cloud or in virga. The estimation of ice water content from particle size data requires that an assumption be made regarding the particle mass-dimensional relation, resulting in potential error on the order of tens of percent. The highest proportion of liquid is typically found in the coldest (top) part of the cloud profile. This feature of the microphysical structure for the midlatitude mixed-phase altocumulus clouds is similar to that reported for mixed-phase clouds over the Arctic region. The results obtained for limited cases of midlatitude mixed-phase clouds observed during CLEX-9 may have an implication for the study of mixed-phase cloud microphysics, satellite remote sensing applications, and the parameterization of mixed-phase cloud radiative properties in climate models. © 2008 American Meteorological Society."
"12040335900;7404653593;57200530823;7102687667;7401895830;","The impact of aerosols on the summer rainfall frequency in China",2008,"10.1175/2007JAMC1745.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51349094850&doi=10.1175%2f2007JAMC1745.1&partnerID=40&md5=5416b98ccd474990f748dd814c25e38f","The authors investigate the short-term relationship between aerosol concentrations and summer rainfall frequency in China using the daily surface observations of particulate matters with a diameter of less than 10 μm (PM10) mass concentration, rainfall, and satellite-observed cloud properties. Results in this study reveal that on the time scale of a few days aerosol concentration is positively correlated with the frequency of moderate-rainfall (10-20mm day-1) days but is negatively correlated with the frequency of light-rainfall (&lt;5 mm day-1) days. Satellite observations of cloud properties show that higher aerosol concentrations are positively correlated with the increase in mixed cloud amount, cloud effective radius, cloud optical depth, and cloud-top heights; this corresponds to the decrease in low-level liquid clouds and the increase in midlevel ice-mixed clouds. Based on this analysis, the authors hypothesize that the increase in aerosol concentration results in the increase in summer rainfall frequency in China via enhanced ice nucleation in the midtroposphere. However, over the past few decades, observations show an increasing long-term trend in aerosol concentration but decreasing trends in summer rainfall frequency and relative humidity (RH) in China. Despite the short-term positive relationship between summer rainfall frequency and aerosol concentration found in this study, the long-term variations in summer rainfall frequency in China are mainly determined by other factors including RH variation possibly caused by global and regional climate changes. A continuous decrease in RH resulting in less summer rainfall frequency may further enhance aerosol concentrations in the future in conjunction with the increase in the anthropogenic emissions. © 2008 American Meteorological Society."
"7201884355;8348260700;57148737800;6603025849;57208346904;","Sensitivity of surface ozone simulation to cumulus parameterization",2008,"10.1175/2007JAMC1780.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57649155197&doi=10.1175%2f2007JAMC1780.1&partnerID=40&md5=ceec86922e479ac4965c2b881e79cdd9","Different cumulus schemes cause significant discrepancies in simulated precipitation, cloud cover, and temperature, which in turn lead to remarkable differences in simulated biogenic volatile organic compound (BVOC) emissions and surface ozone concentrations. As part of an effort to investigate the impact (and its uncertainty) of climate changes on U.S. air quality, this study evaluates the sensitivity of BVOC emissions and surface ozone concentrations to the Grell (GR) and Kain-Fritsch (KF) cumulus parameterizations. Overall, using the KF scheme yields less cloud cover, larger incident solar radiation, warmer surface temperature, and higher boundary layer height and hence generates more BVOC emissions than those using the GR scheme. As a result, the KF (versus GR) scheme produces more than 10 ppb of summer mean daily maximum 8-h ozone concentration over broad regions, resulting in a doubling of the number of high-ozone occurrences. The contributions of meteorological conditions versus BVOC emissions on regional ozone sensitivities to the choice of the cumulus scheme largely offset each other in the California and Texas regions, but the contrast in BVOC emissions dominates over that in the meteorological conditions for ozone differences in the Midwest and Northeast regions. The result demonstrates the necessity of considering the uncertainty of future ozone projections that are identified with alternative model physics configurations. © 2008 American Meteorological Society."
"7007026915;7005050002;25925237700;25925498600;","Composite atmospheric environments of jet contrail outbreaks for the United States",2008,"10.1175/2007JAMC1481.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57649213656&doi=10.1175%2f2007JAMC1481.1&partnerID=40&md5=a01c7c97f462f83a73123cae4432be18","The cirrus-level ""condensation trails"" (contrails) produced by jet aircraft are considered to influence surface climate and its recent changes. To reveal the synoptic atmospheric environments typically associated with multiple co-occurrences of contrails occurring in otherwise clear or partly cloudy skies (outbreaks) for the United States, and ultimately to assist in forecasting these events, a composite (i.e., multicase average) ""synoptic climatology"" at regional scales is developed for the midseason months (January, April, July, October) of 2000-02. The NCEP-NCAR reanalysis data that emphasize upper-troposphere (UT) variables are allied with manually identified outbreaks appearing on satellite Advanced Very High Resolution Radiometer digital data, using a geographic information system. The highest frequencies of outbreaks by far occur in the Midwest (32.6% of all-U.S. total), followed by the Northeast (17.6%) and Southeast (17.2%). In these regions, all of which have a high density of jet air traffic, an additional 2% cirrus cloud coverage from outbreak-related contrails is inferred. Large interannual and interseasonal variations in contrail outbreak frequencies support the role of meteorological variations. For most regions, the outbreak-associated synoptic circulation composite conditions involve UT ridging and a higher and colder tropopause than the climatological average; meridionally enhanced gradients of the UT vertical motion, located between sinking air to the east (in the ridge) and rising air to the west, in advance of a trough; similarly strong gradients of mid-upper-troposphere humidity, comprising dry air located to the east and moist air to the west; and horizontal speed shear ahead of an advancing jet stream. Notwithstanding, there is a geography (i.e., areal differentiation) to contrail outbreak environments: composites for the Northeast suggest an influence of land-sea contrasts on synoptic systems and, therefore, on contrail outbreaks. For the Northwest, there is evident a greater impact of horizontal wind shear contrasted with other regions. The synoptic climatology results are supported by the all-U.S. averages of contrail outbreak UT conditions [climate diagnostics (CDNs)] previously determined for early-mid-September periods of 1995-2001. Moreover, a comparison of these CDNs with those derived for nearby thick natural clouds, including cirrus, helps to clarify their different synoptic associations: the UT conditions typical of thick clouds represent an intensification of those associated with contrail outbreaks and include the greater upward vertical motion, moister air, and stronger westerly winds characteristic of a trough. Given the location of most contrail outbreaks downstream of multilayered cloud systems, contrails may help to extend the ""natural"" cirrus and cirro-stratus spatial coverage. © 2008 American Meteorological Society."
"7006303509;7402888333;7006423931;7403931916;","Understanding ice supersaturation, particle growth, and number concentration in cirrus clouds",2008,"10.1029/2008JD010332","https://www.scopus.com/inward/record.uri?eid=2-s2.0-59749089594&doi=10.1029%2f2008JD010332&partnerID=40&md5=3b9aa71a6f1130eefa531d726fae2538","Many factors control the ice supersaturation and microphysical properties in cirrus clouds. We explore the effects of dynamic forcing, ice nucleation mechanisms, and ice crystal growth rate on the evolution and distribution of water vapor and cloud properties in nighttime cirrus clouds using a one-dimensional cloud model with bin microphysics and remote sensing measurements obtained at the Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility located near Lamont, OK. We forced the model using both large-scale vertical ascent and, for the first time, mean mesoscale velocity derived from radar Doppler velocity measurements. Both heterogeneous and homogeneous nucleation processes are explored, where a classical theory heterogeneous scheme is compared with empirical representations. We evaluated model simulations by examining both bulk cloud properties and distributions of measured radar reflectivity, lidar extinction, and water vapor profiles, as well as retrieved cloud microphysical properties. Our results suggest that mesoscale variability is the primary mechanism needed to reproduce observed quantities. Model sensitivity to the ice growth rate is also investigated. The most realistic simulations as compared with observations are forced using mesoscale waves, include fast ice crystal growth, and initiate ice by either homogeneous or heterogeneous nucleation. Simulated ice crystal number concentrations (tens to hundreds particles per liter) are typically two orders of magnitude smaller than previously published results based on aircraft measurements in cirrus clouds, although higher concentrations are possible in isolated pockets within the nucleation zone. Copyright 2008 by the American Geophysical Union."
"55113736500;","Short-term effects of agriculture on air pollution and climate in California",2008,"10.1029/2008JD010689","https://www.scopus.com/inward/record.uri?eid=2-s2.0-59749087528&doi=10.1029%2f2008JD010689&partnerID=40&md5=4c4835464c06a2bde1a9fe1c679abbe4","This paper discusses the short-term effects of irrigation and albedo differences due to agriculture on California and Los Angeles air pollution and climate. High-resolution irrigation, land use, soil, albedo, and emission data were applied at the subgrid scale in the nested global-through-urban GATOR-GCMOM model to examine these issues following a comparison of baseline model results with data. In August, irrigation alone was found to increase soil moisture, thereby increasing nighttime but decreasing daytime ground temperatures more, causing a net ground cooling in California and Los Angeles. Agriculture was calculated to increase the albedo of the northern Central Valley but decrease that of the southern valley more relative to nonagricultural land today, offsetting part of the cooling due to irrigation alone. The spatial maximum day-night average August cooling in the Central Valley due to irrigation plus albedo differences from a culture was 0.9 K at 30 m height and 2.3 K at the ground, in range of an historic 0.74-2.4 K cooling at 2 m attributed to heavily irrigated agriculture in an independent data study. When averaged over all model cells containing >0% irrigation, irrigation alone and irrigation plus albedo differences decreased day-night average 2-m temperatures by 0.44 K and 0.16 K, respectively, indicating greater local than regional effects of agriculture. In the Central Valley, irrigation increased the relative humidity, cloud water, and precipitation, shifting aerosol and soluble gas mass to clouds and rain. In the valley and Los Angeles, agriculture stabilized air, decreasing wind speeds and turbulence, increasing pollution in the absence of rain. Thus, when enhancing clouds and precipitation, agriculture decreased pollution; otherwise, agriculture increased pollution. Agriculture in parts of the polluted eastern Los Angeles basin increased fine particulate matter by ∼2% and ozone by ∼0.1%. All results wete robust to a change in the simulation date, although further evaluation is needed to better quantify effects of agriculture on climate and air quality. Copyright 2008 by the American Geophysical Union."
"56158622800;7006783796;7408611903;55494568400;7406683894;56325104100;8833356300;8280879000;","Long-range transport and vertical structure of Asian dust from CALIPSO and surface measurements during PACDEX",2008,"10.1029/2008JD010620","https://www.scopus.com/inward/record.uri?eid=2-s2.0-59749102939&doi=10.1029%2f2008JD010620&partnerID=40&md5=03b120e421a180dca1ff05f5ac5224d5","Knowledge of long-range transport and vertical distribution of Asian dust aerosols in the free troposphere is important for estimating their impact on climate. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), surface micropulse lidar (MPL), and standard surface measurements are used to directly observe the long-range transport and vertical distribution of Asian dust aerosols in the free troposphere during the Pacific Dust Experiment (PACDEX). The MPL measurements were made at the Loess Plateau (35.95°N, 104.1°E) near the major dust source regions of the Taklamakan and Gobi deserts. Dust events are more frequent in the Taklamakan, where floating dust dominates, while more intensive, less frequent dust storms are more common in the Gobi region. The vertical distribution of the CALIPSO backscattering/depolarization ratios indicate that nonspherically shaped dust aerosols floated from near the ground to an altitude of approximately 9 km around the source regions. This suggests the possible long-range transport of entrained dust aerosols via upper tropospheric westerly jets. A very distinct large depolarization layer was also identified between 8 and 10 km over eastern China and the western Pacific Ocean corresponding to dust aerosols transported from the Taklamakan and Gobi areas, as confirmed by back trajectory analyses. The combination of these dust sources results in a two-layer or multilayered dust structure over eastern China and the western Pacific Ocean. Copyright 2008 by the American Geophysical Union."
"7102211934;8670472000;","Comparison studies of cloud- and convection-related processes simulated by the canadian regional climate model over the pacific ocean",2008,"10.1175/MWR2494.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57149146329&doi=10.1175%2fMWR2494.1&partnerID=40&md5=a48f901723cd233e3bbeaea5c90ce642","This paper presents results from the Canadian Regional Climate Model (CRCM) contribution to the Global Energy and Water Cycle Experiment (GEWEX) Pacific Cross-section Intercomparison Project. This experiment constitutes a simulation of stratocumulus, trade cumulus, and deep convective transitions along a cross section in the tropical Pacific. The simulated seasonal mean cloud and convection are compared between an original version of CRCM (CRCM4) and a modified version (CRCMM) with refined parameterizations. Results are further compared against available observations and reanalysis data. The specific parameterization refinements touch upon the triggering and closure of shallow convection, the cloud and updraft characteristics of deep convection, the parameterization of large-scale cloud fraction, the calculation of the eddy diffusivity in the boundary layer, and the evaporation of falling large-scale precipitation. CRCMM shows substantial improvement in many aspects of the simulated seasonal mean cloud, convection, and precipitation over the tropical Pacific, CRCMM-simulated total column water vapor, total cloud cover, and precipitation are in better agreement with observations than in the original CRCM4 model. The maximum frequency of the shallow convection shifts from the ITCZ region in CRCM4 to the subtropics in CRCMM; accordingly, excessive cloud in the shallow cumulus region in CRCM4 is greatly diminished. Finally, CRCMM better simulates the vertical structure of relative humidity, cloud cover, and vertical velocity, at least when compared to the 40-yr ECMWF Re-Analysis. Analyses of sensitivity experiments assessing specific effects of individual parameterization changes indicate that the modification to the eddy diffusivity in the boundary layer and changes to deep convection contribute most significantly to the overall model improvements. © 2008 American Meteorological Society."
"7005528529;","Wind erosion of waste impoundments in arid climates and mitigation of dust pollution",2008,"10.1177/0734242X07082027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57149148117&doi=10.1177%2f0734242X07082027&partnerID=40&md5=511734ae4c95d4862dec7730c0e7dcb2","Wind can erode and disperse fine-grained material from an impoundment of mining, industrial or municipal waste that stands above the level of its surroundings. Such dust dispersion can be a serious nuisance as well as a health hazard to inhabitants and animals in nearby settlements. It can also degrade crops, making them less marketable, and pollute soil, surface water and ground water. Wind can seasonally erode waste impoundments in all types of climate, but the erosion intensifies and persists for more of each year as regional aridity increases. As clouds of dust are often observed billowing across the top surfaces of waste impoundments in dry windy weather, there is a common misconception that dust arises from erosion of the top surface of an impoundment, resulting in much effort and money being misspent on top treatments when in fact the sloped sides of the impoundments are the true source of blown dust. This paper offers a brief review of general waste impoundment wind erosion issues and then focuses in more detail on the mechanics of how wind erodes surfaces of waste impoundments. Recommendations are offered for mitigating the effects of wind-eroded dust. © ISWA 2008."
"7005432249;7103337730;8565596200;6701679993;6603698240;7003799892;7004543601;6603313656;7004877677;25824318400;8525956200;25823743300;18134195800;6505971746;56060845000;8860238600;55915046600;","The Canopy and Aerosol Particles Interactions in TOulouse Urban Layer (CAPITOUL) experiment",2008,"10.1007/s00703-008-0289-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58149394854&doi=10.1007%2fs00703-008-0289-4&partnerID=40&md5=62008b4d0e370bf4b2c44efab7ec66c9","The CAPITOUL experiment is a joint experimental effort in urban climate, including the energetic exchanges between the surface and the atmosphere, the dynamics of the boundary layer over the city and its interactions with aerosol chemistry. The campaign took place in the city of Toulouse in southwest France, for one year, from February 2004 to February 2005. This allowed the study of both the day-to-day and seasonal variability of urban climate processes. The observational network included surface stations (meteorology, energy balance, chemistry), profilers and, during intensive observing periods, aircraft and balloons. The urban Surface Energy Balance differs between summer and winter: in summer, the solar heat stored during the previous daytime period is enough to maintain the heat release at night, but in winter, almost all the energy comes from the anthropogenic heat released by space heating. Both processes produce the well known Urban Heat Island (UHI). The cityis shown to impact the entire boundary layer on specific days, when an urban breeze is observed. In wintertime, fog is found to be modified due to the vertical structure of the nocturnal boundary layer above the city (which is slightly unstable and not stable). The measurements of aerosol properties in and downwind the city permitted documentation of the urban aerosol as well as the chemical transformation of these aerosols, in particular the ageing of carbonaceous aerosols during transport. The Toulouse aerosol is mainly composed of carbonaceous particles. There is important seasonal variation in the ratio of black carbon to organic carbon, in the concentration of sulfates and nitrates and in the related radiative aerosol impacts. SF6 was released as a tracer in a suburban area of Toulouse during anticyclonic conditions with weak winds. The tracer measurements show dispersion was mainly driven by the surface sensible heat flux, and was highly sensitive to the urban heat island and also to the transport of boundary layer clouds. Modeling was fully integrated into the campaign. Surface energy balance and urban boundary layer processes have already been used to complement the analyses of the physical processes observed during the campaign. Companion papers detail most of these observation or modeling studies. © Springer-Verlag 2008."
"24485729000;16192856000;","Investigating crater lake warming using ASTER thermal imagery: Case studies at Ruapehu, Poás, Kawah Ijen, and Copahué Volcanoes",2008,"10.1016/j.jvolgeores.2008.06.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55549099303&doi=10.1016%2fj.jvolgeores.2008.06.020&partnerID=40&md5=a3d74d5911275bcb4e084a7a0d6e0805","A two-channel or split-window algorithm designed to correct for atmospheric conditions was applied to thermal images taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) of Lake Yugama on Kusatsu-Shirane volcano in Japan in order to measure the temperature of its crater lake. These temperature calculations were validated using lake water temperatures that were collected on the ground. Overall, the agreement between the temperatures calculated using the split-window method and ground truth is quite good, typically ± 1.5 °C for cloud-free images. Data from fieldwork undertaken in the summer of 2004 at Kusatsu-Shirane allow a comparison of ground-truth data with the radiant temperatures measured using ASTER imagery. Further images were analyzed of Ruapehu, Poás, Kawah Ijen, and Copahué volcanoes to acquire time-series of lake temperatures. A total of 64 images of these 4 volcanoes covering a wide range of geographical locations and climates were analyzed. Results of the split-window algorithm applied to ASTER images are reliable for monitoring thermal changes in active volcanic lakes. These temperature data, when considered in conjunction with traditional volcano monitoring techniques, lead to a better understanding of whether and how thermal changes in crater lakes aid in eruption forecasting. © 2008 Elsevier B.V. All rights reserved."
"6603135083;25959399000;7004192664;22636047600;7003633932;55900158000;","Red coralline algae as a source of marine biogenic dimethylsulphoniopropionate",2008,"10.3354/meps07687","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58249106288&doi=10.3354%2fmeps07687&partnerID=40&md5=bc2494f6d20db1108095b48a93da84a4","The biogenic gas dimethylsulphide (DMS), derived from dimethylsulphoniopropionate (DMSP), plays an important role in the Earth's albedo, and thus climate regulation, through the formation of aerosols and cloud condensation nuclei. It is estimated that biogenic sources of DMS contribute 42% (mean) of the atmospheric sulphur burden and, significantly, &gt;90% of that contribution is derived from marine sources. Phytoplankton, macroalgae and corals are thought to be the main producers of marine biogenic DMSP. Red coralline algae (known as maerl or rhodoliths) cover extensive areas of seabed, yet despite their widespread global distribution, maerl-forming coralline algae have received little or no attention regarding their DMSP productivity. In the present study we report for the first time the occurrence of DMSP in 2 species of maerl. DMSP concentrations were found to average 1914 nmol g-1 for soft tissue and estimated to be 637 μmol m-2 for maerl beds. In incubation experiments, maerl led to a dissolved DMSP (DMSPd) increase at a rate of 57.4 to 767.6 nmol m-2 d-1 in surrounding seawater, indicating that maerl contributes to DMSPd concentrations in the adjacent water column. Results show that maerl beds are a previously undiscovered source of DMSP in the marine environment. Further study is warranted to assess the significance of maerl as a source of DMSP and the role coralline algae may play in the biogenic sulphur cycle. © Inter-Research 2008."
"7005561168;6603639908;8571512400;6602276370;24339339100;6507667894;","Climate of Russia in the 21st century. Part 3. Future climate changes calculated with an ensemble of coupled atmosphere-ocean general circulation CMIP3 models",2008,"10.3103/S106837390809001X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57049178488&doi=10.3103%2fS106837390809001X&partnerID=40&md5=c2bb57efdc54d8dcf45f6db3176b10a9","Probable climate changes in Russia in the 21st century are considered based on the results of global climate simulations with an ensemble of coupled atmosphere-ocean CMIP3 models. The future changes in the surface air temperature, atmospheric pressure, cloud amount, atmospheric precipitation, snow cover, soil water content, and annual runoff in Russia and some of its regions in the early, middle, and late 21st century are analyzed using the A2 scenario of the greenhouse gas and aerosol emission. Future changes in the yearly highest and lowest surface air temperatures and in summer precipitation of high intensity are estimated for Russia. Possible oscillations of the Caspian Sea level associated with the expected global climate warming are estimated. In addition to the estimates of the ensemble mean changes in climatic characteristics, the information about standard deviations and statistical significance of the corresponding climate changes is given. © Allerton Press, Inc. 2008."
"6701324864;7202162685;","Kinetics of cloud drop formation and its parameterization for cloud and climate models",2008,"10.1175/2008JAS2606.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56849110340&doi=10.1175%2f2008JAS2606.1&partnerID=40&md5=0bdb34df821b14d77560ae693c35618c","To study the kinetics of drop nucleation in clouds, the integro-differential equation for integral water supersaturation in cloud is derived and analyzed. Solving the supersaturation equation with an algebraic form of the cloud condensation nuclei (CCN) activity spectrum, analytical expressions are obtained for the time tm of CCN activation process, the maximum supersaturation sm, and droplet concentration Ndr(sm), limited by the total aerosol concentration at high supersaturations. All three quantities are expressed as functions of vertical velocity and characteristics of the CCN size spectra: mean geometric radius, dispersion, and parameters of solubility. A generalized power law for the drop activation, Ndr(sm) = C(sm)smk(sm), is formulated that is similar in form to the Twomey power law, but both the coefficient C(sm) and index k(sm) are functions of supersaturation expressed analytically in terms of vertical velocities and CCN microphysical parameters. A simple and economical numerical solution was developed that describes all of these characteristics without conducting numerous simulations using parcel models. An extended series of numerical experiments was performed, in which the dependencies of tm, sm, Ndr(sm), C(sm), k(sm), and several other important characteristics of activation process were studied as functions of vertical velocity and physicochemical properties of the aerosol. In particular, it is shown that a decrease in the condensation coefficient αc leads to slower CCN activation and higher maximum supersaturation and droplet concentration. Uncertainties in α c may prevent correct estimates of the direct and indirect aerosol effects on climate. The solutions and expressions for the parameters presented here can be used for parameterization of the drop activation process in cloud and climate models. © 2008 American Meteorological Society."
"7410084319;7004539332;13807789500;7404021119;14045744500;13402835300;","PC2: A prognostic cloud fraction and condensation scheme. II: Climate model simulations",2008,"10.1002/qj.332","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049213939&doi=10.1002%2fqj.332&partnerID=40&md5=daae5e9263b5f79dd6fb03622c1b2027","A prognostic cloud fraction and prognostic condensate scheme (PC2) has been developed for the Met Office Unified Model. A companion paper discussed the motivation for a new scheme and described its formulation in detail. In this paper we describe the results of climate model simulations, concentrating on the mechanisms by which the cloud and condensate predicted by the model change between the Control and new scheme. We demonstrate that the detrainment of condensate from the convection scheme directly into the large scale, as parametrized in the PC2 scheme, produces improved simulations of deep tropical cloud. We also show that the unphysical strong link between cloud fraction and condensed water content that is present in the Control scheme has been broken by using PC2, but that it is still challenging to produce optically thin cloud in a large-scale model. Shallow convection proves to be a difficult cloud type to parametrize using a prognostic scheme, although the PC2 scheme performs well. The use of increased vertical resolution, in both the Control and PC2, improved the simulation of cloud when compared to observations. © Crown Copyright 2008."
"57208309414;35473805400;6603431534;22975069200;","Boundary layer, cloud, and drizzle variability in the southeast Pacific stratocumulos regime",2008,"10.1175/2008JCLI2186.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60749087081&doi=10.1175%2f2008JCLI2186.1&partnerID=40&md5=db2db9b7bf3d8e3e6f33f05780cf4582","The southeast Pacific stratocumulus regime is an important component of the earth's climate system because of its substantial impact on albedo. Observational studies of this cloud regime have been limited, but during the past 5 yr, a series of cruises with research vessels equipped with in situ and remote sensing systems have provided unprecedented observations of boundary layer cloud and drizzle structures. These cruises started with the East Pacific Investigation of Climate (EPIC) 2001 field experiment, followed by cruises in a similar area in 2003 and 2004 [Pan-American Climate Studies (PACS) Stratus cruises]. The sampling from these three cruises provides a sufficient dataset to study the variability occurring over this region. This study compares observations from the 2004 cruise with those obtained during the previous two cruises. Observations from the ship provide information about boundary layer structure, fractional cloudiness, cloud depth, and drizzle characteristics. This study indicates more strongly decoupled boundary layers during the 2004 cruise than the well-mixed conditions that dominated the cloud and boundary layer structures during the EPIC cruise, and the highly variable conditions - sharp transitions from a solid stratus deck to broken-cloud and clear-sky periods - encountered during PACS Stratus 2003. Diurnal forcing and synoptic conditions are considered to be factors affecting these variations. A statistical evaluation of the macrophysical boundary layer, cloud, and drizzle properties is performed using the 5-6-day periods for which the research vessels remained stationed at the location of 20°S, 85°W during each cruise. © 2008 American Meteorological Society."
"57203213108;7404243086;38362385200;","Cloud and water vapor feedbacks in a vertrical energy-balance model with maximum entropy production",2008,"10.1175/2008JCLI2349.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60749136548&doi=10.1175%2f2008JCLI2349.1&partnerID=40&md5=1c80c51a22dfdced334d434b3c1d071d","A vertically one-dimensional model is developed with cloud fraction constrained by the maximum entropy production (MEP) principle. The model reasonably reproduces the global mean climate with its surface temperature, radiation and heat fluxes, cloud fraction, and lapse rate. The maximum convection hypothesis in Paltridge's models is related to the MEP principle, and the MEP state of climate is approximately equivalent to that with the maximum lapse rate. The sensitivity investigation about the model assumptions and the prescribed parameters show that the model is considerably robust in simulating the global mean climate. With the MEP constraint, the feedbacks of cloud and water vapor to external forcings, such as changes of CO'2 concentration, solar incidence, and surface albedo, are evaluated. While water vapor always behaves as a strong positive feedback, cloud feedbacks to the different forcings are different, in both magnitude and sign. The modeled feedback of cloud fraction to the forcing resulting from surface albedo variation seems in good agreement with the observed seasonal variation of the global cloud fraction. © 2008 American Meteorological Society."
"7410084319;7004539332;13807789500;7404021119;14045744500;","PC2: A prognostic cloud fraction and condensation scheme. I: Scheme description",2008,"10.1002/qj.333","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049194235&doi=10.1002%2fqj.333&partnerID=40&md5=f8155c017ad14efc2f155ed4289abf66","A prognostic cloud fraction and prognostic condensate scheme has been developed for the Met Office Unified Model. This is designed to replace the scheme currently used in weather forecast and climate simulations, in which cloud fraction and liquid water content are calculated diagnostically. Such a scheme overprescribes links between cloud fraction, condensate and water vapour contents. By contrast, our new prognostic cloud fraction and prognostic condensate scheme (PC2) calculates increments to prognostic variables of liquid, ice and total cloud fractions, water vapour and liquid condensate as a result of each physical process represented in the model. (Ice condensate is already represented prognostically.) This paper provides a summary of the PC2 scheme, describes how it is implemented, and discusses its relationship with other existing cloud schemes. Key aspects of the PC2 formulation are: the consistent derivation of prognostic terms, the reversible nature of the scheme under idealised forcing scenarios, the well-behaved performance in the limit of very low and very high cloud fraction, the inclusion of ice microphysical processes, and the improved representation of cloud erosion processes. A companion paper presents the results from the scheme. © Crown Copyright 2008."
"7202899330;26031402600;","Controls of global-mean precipitation increases in global warming GCM experiments",2008,"10.1175/2008JCLI2144.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60749094247&doi=10.1175%2f2008JCLI2144.1&partnerID=40&md5=8fea54b5a13e99b84dabb7d1d7ad31ae","This paper examines the controls on global precipitation that are evident in the transient experiments conducted using coupled climate models collected for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). The change in precipitation, water vapor clouds, and radiative heating of the atmosphere evident in the 1% increase in carbon dioxide until doubled (1pctto2x) scenario is examined. As noted in other studies, the ensemble-mean changes in water vapor as carbon dioxide is doubled occur at a rate similar to that predicted by the Clausius - Clapeyron relationship. The ratio of global changes in precipitation to global changes in water vapor offers some insight on how readily increased water vapor is converted into precipitation in modeled climate change. This ratio ε is introduced in this paper as, a gross indicator of the global precipitation efficiency under global warming. The main findings of this paper are threefold. First, increases in the global precipitation track increase atmospheric radiative energy loss and the ratio of precipitation sensitivity to water vapor sensitivity is primarily determined by changes to this atmospheric column energy loss. A reference limit to this ratio is introduced as the rate at which the emission of radiation from the clear-sky atmosphere increases as water vapor increases. It is shown that the derived efficiency based on the simple ratio of precipitation to water vapor sensitivities of models in fact closely matches the sensitivity derived from simple energy balance arguments involving changes to water vapor emission alone. Second, although the rate of increase of clear-sky emission is the dominant factor in the change to the energy balance of the atmosphere, there are two important and offsetting processes that contribute to ε in the model simulations studied: One involves a negative feedback through cloud radiative heating that acts to reduce the efficiency; the other is the global reduction in sensible heating that counteracts the effects of the cloud feedback and increases the efficiency. These counteracting feedbacks only apply on the global scale. Third, the negative cloud radiative heating feedback occurs through reductions of cloud amount in the middle troposphere, defined as the layer between 680 and 440 hPa, and by slight global cloud decreases in the lower troposphere. These changes act, in a manner to expose the warmer atmosphere below to high clouds, thus resulting in a net warming of the atmospheric column by clouds and a negative feedback on the precipitation. © 2008 American Meteorological Society."
"6508003871;7005634455;","Atmospheric moisture and cloud cover characteristics forecast by AMPS",2008,"10.1175/2008WAF2006100.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549110157&doi=10.1175%2f2008WAF2006100.1&partnerID=40&md5=809deb7b2fe25470fd007512cf51da4e","Antarctic Mesoscale Prediction System (AMPS) forecasts of atmospheric moisture and cloud fraction (CF) are compared with observations at McMurdo and Amundsen-Scott South Pole station (hereafter, South Pole station) in Antarctica. Overall, it is found that the model produces excessive moisture at both sites in the mid- to upper troposphere because of a weaker vertical decrease of moisture in AMPS than observed. Correlations with observations suggest AMPS does a reasonable job of capturing the low-level moisture variability at McMurdo and the upper-level moisture variability at South Pole station. The model underpredicts the cloud cover at both locations, but changes to the AMPS empirical CF algorithm remove this negative bias by more than doubling the weight given to the cloud ice path. A ""pseudosatellite"" product based on the microphysical quantities of cloud ice and cloud liquid water within AMPS is preliminarily evaluated against Defense Meteorological Satellite Program (DMSP) imagery during summer to examine the broader performance of cloud variability in AMPS. These comparisons reveal that the model predicts high-level cloud cover and movement with fidelity, which explains the good agreement between the modified CF algorithm and the observed CF. However, this product also demonstrates deficiencies in capturing low-level cloudiness over cold ice surfaces primarily related to insufficient supercooled liquid water produced by the microphysics scheme, which also reduces the CF correlation with observations. The results suggest that AMPS predicts the overall CF amount and high cloud variability notably well, making it a reliable tool for longer-term climate studies of these fields in Antarctica. © 2008 American Meteorological Society."
"7404521962;57219300517;","Giant sea-salt aerosols and warm rain formation in marine stratocumulus",2008,"10.1175/2008JAS2617.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549093263&doi=10.1175%2f2008JAS2617.1&partnerID=40&md5=fb4550855217544474fc95d2d452bbc8","The concentrations and sizes of smaller aerosols (radius smaller than 0.5 μm) in the marine atmosphere vary owing to natural and anthropogenic factors. The concentrations and sizes of giant and ultragiant aerosols vary primarily due to wind-speed-dependent wave breaking. In climate models the formation of warm rain from marine stratocumulus clouds is usually parameterized based on the drops that form on the smaller aerosols. The present process study, using a stochastic Monte Carlo cloud model, shows that the variability of giant sea-salt aerosols and the variability of smaller aerosol cloud condensation nuclei are equally important in determining precipitation flux in marine stratocumulus. This strongly suggests that the effects of giant sea-salt aerosols should be included in the parameterization of warm rain formation in climate and other large-scale models. The above results are based on highly detailed calculations of droplet growth in an idealized marine stratocumulus cloud; the authors believe that other marine stratus cloud conditions may change the calculated rain rates but that the conclusions regarding the relative importance of small and giant aerosols are robust. © 2008 American Meteorological Society."
"24398842400;57203053317;55915206300;8728433200;6603452105;","Global simulations of aerosol processing in clouds",2008,"10.5194/acp-8-6939-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57349163493&doi=10.5194%2facp-8-6939-2008&partnerID=40&md5=7ce2370476d13801d94912746c92b71c","An explicit and detailed representation of in-droplet and in-crystal aerosol particles in stratiform clouds has been introduced in the global aerosol-climate model ECHAM5-HAM. The new scheme allows an evaluation of the cloud cycling of aerosols and an estimation of the relative contributions of nucleation and collision scavenging, as opposed to evaporation of hydrometeors in the global aerosol processing by clouds. On average an aerosol particle is cycled through stratiform clouds 0.5 times. The new scheme leads to important changes in the simulated fraction of aerosol scavenged in clouds, and consequently in the aerosol wet deposition. In general, less aerosol is scavenged into clouds with the new prognostic treatment than what is prescribed in standard ECHAM5-HAM. Aerosol concentrations, size distributions, scavenged fractions and cloud droplet concentrations are evaluated and compared to different observations. While the scavenged fraction and the aerosol number concentrations in the marine boundary layer are well represented in the new model, aerosol optical thickness, cloud droplet number concentrations in the marine boundary layer and the aerosol volume in the accumulation and coarse modes over the oceans are overestimated. Sensitivity studies suggest that a better representation of below-cloud scavenging, higher in-cloud collision coefficients, or a reduced water uptake by seasalt aerosols could reduce these biases."
"7003663305;7202043942;7006041988;57203233100;6603431534;7402480218;19337612500;7402934750;6701873414;","A focus on mixed-phase clouds",2008,"10.1175/2008BAMS2378.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60849086477&doi=10.1175%2f2008BAMS2378.1&partnerID=40&md5=8809366460b731a57169cf0da601fc27","The phase composition and microphysical structure of clouds define the manner in which they modulate atmospheric radiation and contribute to the hydrologic cycle. Issues regarding cloud phase partitioning and transformation come to bear directly in mixed-phase clouds, and have been difficult to address within current modeling frameworks. Ground-based, remote-sensing observations of mixed-phase clouds can contribute a significant body of knowledge with which to better understand, and thereby more accurately model, clouds and their phase-defining processes. Utilizing example observations from the Mixed-Phase Arctic Cloud Experiment (MPACE), which occurred at the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program's Climate Research Facility in Barrow, Alaska, during autumn 2004, we review the current status of ground-based observation and retrieval methods used in characterizing the macrophysical, microphysical, radiative, and dynamical properties of stratiform mixed-phase clouds. In general, cloud phase, boundaries, ice properties, liquid water path, optical depth, and vertical velocity are available from a combination of active and passive sensors. Significant deficiencies exist in our ability to vertically characterize the liquid phase, to distinguish ice crystal habits, and to understand aerosol-cloud interactions. Further validation studies are needed to evaluate, improve, and expand our retrieval abilities in mixed-phase clouds. © 2008 American Meteorological Society."
"7004091561;7005002049;13406040100;7004252268;7202180152;6602378790;7403384594;","CMAQ model performance enhanced when in-cloud secondary organic aerosol is included: Comparisons of organic carbon predictions with measurements",2008,"10.1021/es801192n","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57449092717&doi=10.1021%2fes801192n&partnerID=40&md5=0dd35754f44a1fe5e69db26ecd594dbb","Mounting evidence suggests that low-volatility (particle-phase) organic compounds form in the atmosphere through aqueous phase reactions in clouds and aerosols. Although some models have begun including secondary organic aerosol (SOA) formation through cloud processing, validation studies that compare predictions and measurements are needed. In this work, agreement between modeled organic carbon (OC) and aircraft measurements of water soluble OC improved for all 5 of the compared ICARTT NOAA-P3 flights during August when an in-cloud SOA (SIAcld) formation mechanism was added to CMAQ (a regional-scale atmospheric model). The improvement was most dramatic for the August 14th flight, a flight designed specifically to investigate clouds. During this flight, the normalized mean bias for layer-averaged OC was reduced from -64 to -15% and correlation (r) improved from 0.5 to 0.6. Underpredictions of OC aloft by atmospheric models may be explained, in part, by this formation mechanism (SOAcld). OC formation aloft contributes to long-range pollution transport and has implications to radiative forcing, regional air quality and climate. © 2008 American Chemical Society."
"7103271625;7006739521;","Climate modeling",2008,"10.1146/annurev.environ.33.020707.160752","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68049126436&doi=10.1146%2fannurev.environ.33.020707.160752&partnerID=40&md5=19ab5adf914c8e0bd96e260b945e582e","Climate models simulate the atmosphere, given atmospheric composition and energy from the sun, and include explicit modeling of, and exchanges with, the underlying oceans, sea ice, and land. The models are based on physical principles governing momentum, thermodynamics, cloud microphysics, radiative transfer, and turbulence. Climate models are evolving into Earth-system models, which also include chemical and biological processes and afford the prospect of links to studies of human dimensions of climate change. Although the fundamental principles on which climate models are based are robust, computational limits preclude their numerical solution on scales that include many processes important in the climate system. Despite this limitation, which is often dealt with by parameterization, many aspects of past and present climate have been successfully simulated using climate models, and climate models are used extensively to predict future climate change resulting from human activity. © 2008 by Annual Reviews."
"23094223900;25228634000;6701847229;6701571700;7003748648;7003499456;","Analysis of ERA 40-driven CLM simulations for Europe",2008,"10.1127/0941-2948/2008/0301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049101915&doi=10.1127%2f0941-2948%2f2008%2f0301&partnerID=40&md5=7c5da5ba9bfc6e39a2ae82e2dfcd3073","The Climate Local Model (CLM) is a community Regional Climate Model (RCM) based on the COSMO weather forecast model. We present a validation of long-term ERA40-driven CLM simulations performed with differentmodel versions. In particular we analyse three simulations with differences in boundary nudging and horizontal resolution performed for the EU-project ENSEMBLES with the model version 2.4.6, and one with the latest version 4.0. Moreover, we include for comparison a long-term simulation with the RCM CHRM previously used at ETH Zurich. We provide a thorough validation of temperature, precipitation, net radiation, cloud cover, circulation, evaporation and terrestrial water storage for winter and summer. For temperature and precipitation the interannual variability is additionally assessed. While simulations with CLM version 2.4.6 are generally too warm and dry in summer but still within the typical error of PRUDENCE simulations, version 4.0 has an anomalous cold and wet bias. This is partly due to a strong underestimation of the net radiation associated with cloud cover overestimation. Two similar CLM 2.4.6 simulations with different spatial resolutions (0.44° and 0.22°) reveal for the analysed fields no clear benefit of the higher resolution except for better resolved fine-scale structures. While the large-scale circulation is represented more realistically with spectral nudging, temperature and precipitation are not. Overall, CLM performs comparatively to other state-of-the-art RCMs over Europe. © by Gebrüder Borntraeger 2008."
"14037284600;7402642949;","An upper threshold of enhanced global shortwave irradiance in the troposphere derived from field measurements in tropical mountains",2008,"10.1175/2008JAMC1861.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65349187129&doi=10.1175%2f2008JAMC1861.1&partnerID=40&md5=3e50f1dce430dbbc52472715efc27e5f","Extraordinarily high values of global irradiance (up to 1832 W m-22) incident upon a horizontal surface were observed during a 4-yr meteorological field campaign in the southern Ecuadorian Andes Mountains (4°S). The unexpected magnitude gave rise to a thorough revision of the instrumentation and an assessment of the radiation database. Infrastructure at the sites and software were critically examined, and the sensor and datalogger manufacturers were contacted. The observed enhanced irradiance was quantified with a simple clear-sky model for global radiation. The efforts showed that atmospheric conditions and not artifacts had produced the high values. Cloud radiative effects could be singled out as the exclusive source of the ""superirradiance."" Mean (bihourly) maximum enhancement was 119.6% of the potential (clear sky) irradiance; absolute maximum enhancement occasionally reached to over 170%. Thereby, under ideal conditions, the upper threshold of global irradiance is apparently ∼200% of the potential (clear sky) direct radiation [i.e., at the point of observation, downwelling diffuse cloud radiation can (almost) equal the magnitude of its apparent ""source""]. The observations were made between altitudes of 1500 and 3400 m MSL in different climates ranging from perhumid to semiarid (i.e., in very cloudy climates and in less cloudy climates). The conditions that were found to explain the magnitude of the extremely enhanced irradiance are not confined to tropical or mountainous environments only, but rather they can occur at any spot in the troposphere where clouds exist. Therefore, the findings appear to be of general validity. © 2008 American Meteorological Society."
"7403076014;56603352400;57202992636;35209683700;7103098729;","Error reduction and convergence in climate prediction",2008,"10.1175/2008JCLI2112.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60749088614&doi=10.1175%2f2008JCLI2112.1&partnerID=40&md5=2564e25c32d72a34e52a98bdf80bf4c2","Although climate models have steadily improved their ability to reproduce the observed climate, over the years there has been little change to the wide range of sensitivities exhibited by different models to a doubling of atmospheric CO2 concentrations. Stochastic optimization is used to mimic how six independent climate model development efforts might use the same atmospheric general circulation model, set of observational constraints, and model skill criteria to choose different settings for parameters thought to be important sources of uncertainty related to clouds and convection. Each optimized model improved its skill with respect to observations selected as targets of model development. Of particular note were the improvements seen in reproducing observed extreme rainfall rates over the tropical Pacific, which was not specifically targeted during the optimization process. As compared to the default model sensitivity of 2.4°C, the ensemble of optimized model configurations had a larger and narrower range of sensitivities around 3°C but with different regional responses related to the uncertain choice in optimized parameter settings. These results suggest current generation models, if similarly optimized, may become more convergent in their measure of global sensitivity to greenhouse gas forcing. However, this exploration of the possible sources of modeling and observational uncertainty is not exhaustive. The optimization process illustrates an objective means for selecting an ensemble of plausible climate model configurations that quantify a portion of the uncertainty in the climate model development process. © 2008 American Meteorological Society."
"19337612500;6603431534;55476479200;7006204393;","A technique for the automatic detection of insect clutter in cloud radar returns",2008,"10.1175/2007JTECHA953.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549127365&doi=10.1175%2f2007JTECHA953.1&partnerID=40&md5=b78730d3e1baa8388c57716458f6816d","The U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program operates 35-GHz millimeter-wavelength cloud radars (MMCRs) in several climatologically distinct regions. The MMCRs, which are centerpiece instruments for the observation of clouds and precipitation, provide continuous, vertically resolved information on all hydrometeors above the ARM Climate Research Facilities (ACRF). However, their ability to observe clouds in the lowest 2-3 km of the atmosphere is often obscured by the presence of strong echoes from insects, especially during the warm months at the continental midlatitude Southern Great Plains (SGP) ACRF. Here, a new automated technique for the detection and elimination of insect-contaminated echoes from the MMCR observations is presented. The technique is based on recorded MMCR Doppler spectra, a feature extractor that conditions insect spectral signatures, and the use of a neural network algorithm for the generation of an insect (clutter) mask. The technique exhibits significant skill in the identification of insect radar returns (more than 92% of insect-induced returns are identified) when the sole input to the classifier is the MMCR Doppler spectrum. The addition of circular polarization observations by the MMCR and ceilometer cloud-base measurements further improve the performance of the technique and form an even more reliable method for the removal of insect radar echoes at the ARM site. Recently, a 94-GHz Doppler polarimetric radar was installed next to the MMCR at the ACRF SGP site. Observations by both radars are used to evaluate the potential of the 94-GHz radar as being insect free and to show that dual wavelength radar reflectivity measurements can be used to identify insect radar returns. © 2008 American Meteorological Society."
"6602858513;23008652200;7006813815;","A multiresolution method for climate system modeling: Application of spherical centroidal Voronoi tessellations",2008,"10.1007/s10236-008-0157-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57849126275&doi=10.1007%2fs10236-008-0157-2&partnerID=40&md5=dd4c8bdbcc46b28e22f8410c0e259b15","During the next decade and beyond, climate system models will be challenged to resolve scales and processes that are far beyond their current scope. Each climate system component has its prototypical example of an unresolved process that may strongly influence the global climate system, ranging from eddy activity within ocean models, to ice streams within ice sheet models, to surface hydrological processes within land system models, to cloud processes within atmosphere models. These new demands will almost certainly result in the develop of multiresolution schemes that are able, at least regionally, to faithfully simulate these fine-scale processes. Spherical centroidal Voronoi tessellations (SCVTs) offer one potential path toward the development of a robust, multiresolution climate system model components. SCVTs allow for the generation of high-quality Voronoi diagrams and Delaunay triangulations through the use of an intuitive, user-defined density function. In each of the examples provided, this method results in high-quality meshes where the quality measures are guaranteed to improve as the number of nodes is increased. Real-world examples are developed for the Greenland ice sheet and the North Atlantic ocean. Idealized examples are developed for ocean-ice shelf interaction and for regional atmospheric modeling. In addition to defining, developing, and exhibiting SCVTs, we pair this mesh generation technique with a previously developed finite-volume method. Our numerical example is based on the nonlinear, shallow-water equations spanning the entire surface of the sphere. This example is used to elucidate both the po tential benefits of this multiresolution method and the challenges ahead. © 2008 Springer-Verlag."
"55207447000;","Uncertainty in climate sensitivity: Causes, consequences, challenges",2008,"10.1039/b810350j","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952402461&doi=10.1039%2fb810350j&partnerID=40&md5=cc73efd9bd03f51d458268f6c6bf8db1","Fossil fuels supply about 85% of the world's primary energy, and future use would not appear limited by availability of reserves, especially of coal. Rather, future use of fossil fuels will likely be limited by controls on the emission of carbon dioxide into the atmosphere that are agreed to by the nations of the world. The increase in atmospheric CO2 over the past 200 years, mainly from fossil fuel combustion, is confidently thought to have increased global temperatures and induced other changes in Earth's climate, with the prospect of much more severe consequences from projected future emissions. Limiting such changes in Earth's climate would place major constraints on the combustion of fossil fuels and/or the emission of CO2 into the atmosphere. Developing effective and cost-effective strategies for limiting CO2 emissions requires the confident ability to project the changes in climate that would result from a given increase in atmospheric CO 2. However, even the change in global mean surface temperature (GMST), the single most important index of climate change, that would result from a given increase in atmospheric CO2 remains uncertain to a factor of 2 or more, largely because of uncertainty in Earth's climate sensitivity, the change in GMST per change in radiative flux. This uncertainty in climate sensitivity, which gives rise to a comparable uncertainty in the shared global resource of the amount of fossil fuel that can be burned consonant with a given increase in global mean surface temperature, greatly limits the ability to effectively formulate strategies to limit climate change while meeting the world's future energy requirements. Key limits on determining climate sensitivity are the small change in downwelling longwave irradiance, less than one percent, that would give rise to changes in climate that reach the level of concern, the complexity of cloud processes and the difficulty of representing them in climate models, and limited understanding of the processes that control the radiative influences of atmospheric aerosols. A recent empirical calculation of Earth's climate sensitivity as the quotient of the relaxation time constant of GMST upon the effective heat capacity characterizing climate change on the multidecadal time scale points to a possible alternative approach to determining Earth's climate sensitivity. While improved knowledge of Earth's climate sensitivity is essential to development of optimal energy strategies, even for climate sensitivity at the low end of the range of present estimates, substantial reductions in CO2 emissions from their present values would be required to avert dangerous anthropogenic interference with the climate system that would otherwise occur well before the end of the present century. © The Royal Society of Chemistry 2008."
"7103016965;25031430500;7102696626;24722339600;7006705919;7103158465;","Midlatitude cyclone compositing to constrain climate model behavior using satellite observations",2008,"10.1175/2008JCLI2235.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60749112093&doi=10.1175%2f2008JCLI2235.1&partnerID=40&md5=615462ba8f137370409d56e52e685f60","Identical composite analysis of midlatitude cyclones over oceanic regions has been carried out on both output from the NCAR Community Atmosphere Model, version 3 (CAM3) and multisensor satellite data. By focusing on mean fields associated with a single phenomenon, the ability of the CAM3 to reproduce realistic midlatitude cyclones is critically appraised. A number of perturbations to the control model were tested against observations, including a candidate new microphysics package for the CAM. The new microphysics removes the temperature-dependent phase determination of the old scheme and introduces representations of microphysical processes to convert from one phase to another and from cloud to precipitation species. By subsampling composite cyclones based on systemwide mean strength (mean wind speed) and systemwide mean moisture the authors believe they are able to make meaningful like-with-like comparisons between observations and model output. All variations of the CAM tested overestimate the optical thickness of high-topped clouds in regions of precipitation. Over a system as a whole, the model can both over- and underestimate total high-topped cloud amounts. However, systemwide mean rainfall rates and composite structure appear to be in broad agreement with satellite estimates. When cyclone strength is taken into account, changes in moisture and rainfall rates from both satellite-derived observations and model output as a function of changes in sea surface temperature are in accordance with the Clausius-Clapeyron equation. The authors find that the proposed new microphysics package shows improvement to composite liquid water path fields and cloud amounts. © 2008 American Meteorological Society."
"8687853700;7404433688;35265615300;55386235300;","Retrieval of liquid water path inside nonprecipitating clouds using TMI measurements",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049209431&partnerID=40&md5=6c792f06614d3d3ef035f2281fb1621b","Quantitative estimates of liquid water path (LWP) in clouds using satellite measurements are critical to understanding of cloud properties and the assessment of global climate change. In this paper, the relationship between microwave brightness temperature (TB) and LWP in the nonprecipitating clouds is studied by using satellite microwave measurements from the TRMM Microwave Imager (TMI) onboard the Tropical Rainfall Measuring Mission (TRMM), together with a radiative transfer model for microwave radiance calculations. Radiative transfer modeling shows that the sensitivity is higher at both 37.0- and 85.5-GHz horizontal polarization channels for the LWP retrievals. Also, the differences between the retrieved values responding to TBs of various channels and the theoretical values are displayed by the model. Based upon above simulations, with taking into account the factor of resolution and retrieval bias for a single channel, a nonprecipitating cloud LWP in the summer subtropical marine environment retrieval algorithm is formulated by the combination of the two TMI horizontal polarization channels, 37.0 and 85.5 GHz. Moreover, by using TMI measurements (1B11), this algorithm is applied to retrieving respectively LWPs for clear sky, nonprecipitating clouds, and typhoon precipitating clouds. In the clear sky case, the LWP changes from -1 to 1 g m-2, and its mean value is about 10-5 g m-2. It indicates that, using this combination retrieval algorithm, there are no obvious systemic deviations when the LWP is low enough. The LWP values varying from 0 to 1000 g m-2 in nonprecipitating clouds are reasonable, and its distribution pattern is very similar to the detected results in the visible channel of Visible and Infrared Scanner (VIRS) on the TRMM. In typhoon precipitating clouds, there is much more proportion of high LWP in the mature phase than the early stage. When surface rainfall rate is lower than 5 mm h-1, the LWP increases with increasing rainfall rate."
"6505569858;6508060859;16241942600;7003930724;7004109472;","Scale-dependent analyses of precipitation forecasts and cloud properties using the Dynamic State Index",2008,"10.1127/0941-2948/2008/0346","https://www.scopus.com/inward/record.uri?eid=2-s2.0-63449103983&doi=10.1127%2f0941-2948%2f2008%2f0346&partnerID=40&md5=313c23d0df624aefe611fae40eaba1fc","The objective of this study is a scale-dependent analysis of precipitation forecasts of the German Weather Service's (DWD) non-hydrostatic Lokal-Modell (LM, COSMO-DE) with regard to dynamical-statistical parameters and cloud properties. We propose a newly designed Dynamic State Index (DSI) to evaluate precipitation processes. The DSI is presented in the context of a case study in the synoptic scale and in a statistical approach. The DSI quantitatively describes the deviation from a stationary, adiabatic and reversible solution of the primitive equations. As demonstrated by the example of the winter storm ""Kyrill"", the analysis of the vertical structure of the DSI gives a relation to the IPV-Thinking, introduced by Hoskins et al. (1985). Furthermore, the DSI-pattern features the characteristic filament-like structure of rainbands with embedded convective cells. In a next step the DSI is not only correlated with modelled precipitation but also with observed precipitation as well as cloud types. The absolute value of the DSI shows moderate correlations with hourly LM and high correlations with hourly COSMO-DE forecast data, based on 24 hour predictions. The statistical analysis of clouds with the index reveals a DSI-threshold, which is used to introduce a novel precipitation activity index of different cloud classes. In conclusion, the results highlight the importance of dynamical processes for the generation of rainfall. © Gebrüder Borntraeger, Berlin, Stuttgart 2008."
"18134393700;56123778400;","A local ensemble prediction system for fog and low clouds: Construction, bayesian model averaging calibration, and validation",2008,"10.1175/2008JAMC1783.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65249103483&doi=10.1175%2f2008JAMC1783.1&partnerID=40&md5=6f20d00d6af69dfa93d11aae83c7fe87","At main international airports, air traffic safety and economic issues related to poor visibility conditions are crucial. Meteorologists face the challenge of supplying airport authorities with accurate forecasts of fog and cloud ceiling. These events are difficult to forecast because conditions evolve on short space and time scales during their life cycle. To obtain accurate forecasts of fog and low clouds, the Code de Brouillard à l'Echelle Locale (the local scale fog code)-Interactions between Soil, Biosphere, and Atmosphere (COBEL-ISBA) local numerical forecast system was implemented at Charles de Gaulle International Airport in Paris. However, even with dedicated observations and initialization, uncertainties remain in both initial conditions and mesoscale forcings. A local ensemble prediction system (LEPS) has been designed around the COBEL-ISBA numerical model and tested to assess the predictability of low visibility procedures events, defined as a visibility less than 600 m and/or a ceiling below 60 m. This work describes and evaluates a local ensemble strategy for the prediction of low visibility procedures. A Bayesian model averaging method has been applied to calibrate the ensemble. The study shows that the use of LEPS for specific local event prediction is well adapted and useful for low visibility prediction in the aeronautic context. Moreover, a wide range of users, especially those with low cost-loss ratios, can expect economic savings with the use of this probabilistic system. © 2008 American Meteorological Society."
"12143775300;56245612500;12143017100;12143985500;","Climatological reproducibility evaluation and future climate projection of extreme precipitation events in the baiu season using a high-resolution non-hydrostatic RCM in comparison with an AGCM",2008,"10.2151/jmsj.86.951","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65749100571&doi=10.2151%2fjmsj.86.951&partnerID=40&md5=2952ece13ab793a26eae8d33d7786b5b","This paper studies an evaluation of climatological reproducibility and one of future climate projections of extreme precipitation in the Baiu season (from mid-May to July) around Japan using data of numerical experiments. The models are a non-hydrostatic cloud-system-resolving atmospheric model with a horizontal grid size of 5 km (5km-NHM) utilized as a regional climate model (RCM), and an atmospheric general circulation model (AGCM) with a horizontal resolution of about 20 km (20km-AGCM) which provided the boundary condition of 5km-NHM. Ten-year runs were performed by the time-slice method. The mean precipitation amount of the three heaviest precipitation events that ranked in order of precipitation amount in every year (PTop3) at each grid point was used as an index to examine quantitatively extreme precipitation within a specific term with various precipitation accumulation periods (APs). The 5km-NHM experiment reproduced PTop3 much better than that of 20km-AGCM, especially for shorter APs. In the projection of PTop3 in the future climate with 5km-NHM, ratio in two climate states of PTop3 for longer APs and that of precipitation amount show the roughly same pattern. The increase areas of those were localized around Kyushu, Japan. In particular, the PTop3 for longer APs was projected to increase 30-70% in the mountainous areas along the Pacific coast of western Japan. This increase was due to a cyclonic circulation of an incremental low-pressure generated on the western side of Kyushu. On the other hand, large increases of PTop3 for shorter APs spread widely with a scattered pattern to the area where precipitation decreases. This characteristic was associated with the intensification of precipitation due to global warming. © 2008, Meteorological Society of Japan."
"7403253358;57201725986;","Responses of tropical deep convective precipitation systems and their associated convective and stratiform regions to the large-scale forcing",2008,"10.1002/qj.331","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049191459&doi=10.1002%2fqj.331&partnerID=40&md5=8bddf02cb11706cff3c9cf2d57ce148d","Responses of convective and stratiform rainfall to large-scale forcing in the tropical deep convective regime are investigated by analysing 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. The imposed large-scale vertical velocity shows that the ascending motion averaged from 22-27 December 1992 is significantly stronger than that averaged from 3-8 January 1993. Thus, the periods of 22-27 December 1992 and 3-8 January 1993 are, respectively, identified as strong-forcing (SF) and weak-forcing (WF) phases. Although the convective rain rates are similar in the two phases, stratiform rain rate is larger in the SF phase than in the WF phase, which leads to larger time and spatial mean surface rain rate in the SF phase. Similar rates of water vapour convergence and vapour condensation and collection of cloud water by rain over water-hydrometeor-dominated convective regions are responsible for similar convective rain rates in the two phases. Water vapour divergence is larger in the WF phase than in the SF phase, which causes smaller vapour condensation and deposition rates in the WF phase. As a result, the collection rate of cloud water by rain and the melting rate of graupel to rain are smaller in the WF phase than in the SF phase, which accounts for the smaller stratiform rain rate in the WF phase. Copyright © 2008 Royal Meteorological Society."
"7003902659;","A rough guide to environmental art",2008,"10.1146/annurev.environ.31.042605.134920","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68049148658&doi=10.1146%2fannurev.environ.31.042605.134920&partnerID=40&md5=537316aab37634f07a1b7623a169d226","To appreciate the beauty or the fragility of our environment and our cultural responses to it, we need to understand how artists have portrayed the environment in the past and how they are continuing to portray it in the present. Environmental art is presented in this paper as a new genre to describe works of art that are not only directly representational of the environment (e.g., Constable's Cloud Series or Monet's London Series) but also works of art that are clearly nonrepresentational and performative, such as Long's A Line Made byWalking or Turrell's Skyspaces. The need for an overarching new genre to describe nonrepresentational performative environmental art is more obvious because there has been a host of labels given to this type of art since the late 1960s, such as land art, earthworks, site-specific art, destination art, ecological art, eco-art, and environmental sculpture. The review is also concerned with the potential of environmental art for communicating climate change. ©2008 by Annual Reviews."
"24322005900;25941200000;8397494800;7003311618;57205867148;","Impact of a new radiation package, McRad, in the ECMWF integrated forecasting system",2008,"10.1175/2008MWR2363.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57349153518&doi=10.1175%2f2008MWR2363.1&partnerID=40&md5=5dfb874e7572098a32b6e9342668241f","A new radiation package, ""McRad,"" has become operational with cycle 32R2 of the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). McRad includes an improved description of the land surface albedo from Moderate Resolution Imaging Spectro-radiometer (MODIS) observations, the Monte Carlo independent column approximation treatment of the radiative transfer in clouds, and the Rapid Radiative Transfer Model shortwave scheme. The impact of McRad on year-long simulations at TL159L91 and higher-resolution 10-day forecasts is then documented. McRad is shown to benefit the representation of most parameters over both shorter and longer time scales, relative to the previous operational version of the radiative transfer schemes. At all resolutions, McRad improves the representation of the cloud-radiation interactions, particularly in the tropical regions, with improved temperature and wind objective scores through a reduction of some systematic errors in the position of tropical convection as a result of a change in the overall distribution of diabatic heating over the vertical plane, inducing a geographical redistribution of the centers of convection. Although smaller, the improvement is also seen in the rmse of geopotential in the Northern and Southern Hemispheres and over Europe. Given the importance of cloudiness in modulating the radiative fluxes, the sensitivity of the model to cloud overlap assumption (COA) is also addressed, with emphasis on the flexibility that is inherent to this new RT approach when dealing with COA. The sensitivity of the forecasts to the space interpolation that is required to efficiently address the high computational cost of the RT parameterization is also revisited. A reduction of the radiation grid for the Ensemble Prediction System is shown to be of little impact on the scores while reducing the computational cost of the radiation computations. McRad is also shown to decrease the cold bias in ocean surface temperature in climate integrations with a coupled ocean system. © 2008 American Meteorological Society."
"57111001300;57030797300;15026371500;","Response of the zonal mean atmospheric circulation to El Niño versus global warming",2008,"10.1175/2008JCLI2200.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48749083954&doi=10.1175%2f2008JCLI2200.1&partnerID=40&md5=81aa4f04909437143a81860702daf7f4","The change in the zonal mean atmospheric circulation under global warming is studied in comparison with the response to El Niño forcing, by examining the model simulations conducted for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. In contrast to the strengthening and contraction of the Hadley cell and the equatorward shift of the' tropospheric zonal jets in response to El Niño, the Hadley cell weakens and expands poleward, and the jets move poleward in a warmed climate, despite the projected ""El Niño-like"" enhanced warming over the equatorial central and eastern Pacific. The hydrological impacts of global warming also exhibit distinct patterns over the subtropics and midlatitudes in comparison to the El Niño. Two feasible mechanisms are proposed for the zonal mean circulation response to global warming: 1) The increase in static stability of the subtropical - and midlatitude troposphere, a robust result of the quasi-moist adiabatic adjustment to the surface warming, may stabilize the baroclinic eddy growth on the equatorward side of the storm tracks and push the eddy activity and the associated eddy-driven wind and subsidence poleward, leading to the poleward expansion of the Hadley cell and the shift of midlatitude jets; 2) the strengthening of the midlatitude wind at the upper troposphere and lower stratosphere, arguably a consequence of increases in the meridional temperature gradient near the tropopause level due to the tropospheric warming and tropopause slope, may increase the eastward propagation of the eddies emanating from the midlatitudes, and thus the subtropical region of wave breaking displaces poleward together with the eddy-driven circulation. Both mechanisms are somewhat, if not completely, distinct from those in response to the El Niño condition. © 2008 American Meteorological Society."
"35513762000;7402974423;","Investigating urban clear islands in fog and low stratus clouds in the San Joaquin Valley of California",2008,"10.2747/0272-3646.29.5.442","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549119759&doi=10.2747%2f0272-3646.29.5.442&partnerID=40&md5=017460f1c797b65132e921fde77f4c77","Urban clear islands (UCI) occur as radiation fog and low stratus clouds preferentially dissipate near large urban areas. In this study, 13 UCI episodes occurring near the urban footprint of Fresno, California, were analyzed to answer basic questions about the phenomenon. The UCI episodes were observed via geostationary satellites. Shape and area analysis was performed with standard geographic information system utilities. The results of the study suggest that UCI's developing in close proximity to the same urban footprint vary markedly in rate of expansion, complexity of shape, and total clear area. Most UCI's developed after the noon hour (local time) and expanded over a 1.5 hour period. At the first observation of clearing above the urban footprint, the total clear area ranged from 4 km2 to 207 km2 across the 13 episodes. Observations 1.5 hours later revealed a clear area ranging from 126 km2 to 692 km2. A shape parameter was calculated for each UCI at three temporal intervals. The UCI boundaries varied in shape complexity and compactness with six of the episodes becoming less compact over the UCI life cycle and seven episodes showing the opposite behavior (becoming more compact/less complex in shape as total clear area expanded). The only surface meteorological parameters significantly associated with total clear area of the Fresno, California, UCI were (1) relative humidity in the urban footprint and (2) the difference in relative humidity between urban and rural observation sites. There was a significant statistical relationship between clear area at first observation and the total clear area at the end of the UCI expansion cycle. Copyright © 2008 by Bellwether Publishing, Ltd. All rights reserved."
"55739389200;7402720392;7403295212;7004800276;","Interpretation of the GRACE-derived mass trend in Enderby Land, Antarctica",2008,"10.1016/j.polar.2008.10.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57849104370&doi=10.1016%2fj.polar.2008.10.001&partnerID=40&md5=bd3fd1a97ac358b46decea03968de560","Monthly gravity solutions of the Gravity Recovery and Climate Experiment (GRACE) reveal three areas in Antarctica with striking interannual mass trends. The positive mass trend in Enderby Land, East Antarctica, is poorly understood because of uncertainties in the surface ice-sheet mass balance, post-glacial rebound (PGR), and processing of GRACE data. In this study, we compare the GRACE mass trends with values estimated from in situ snow-stake measurements, and Ice Cloud and land Elevation Satellite (ICESat) data. The mass trends estimated from ICESat data show a strong correlation with GRACE mass trends. In contrast, the snow-stake data show discrepancies with temporal variations in GRACE mass, especially in 2006. The discrepancies are probably associated with basal ice-sheet outflow, which is difficult to observe using snow stakes. We conclude that the bulk of the GRACE mass trend can be explained by snow accumulation and basal ice-sheet outflow. © 2008 Elsevier B.V. and NIPR."
"6506944086;9740124600;26021826300;57192903033;6603123442;","Correlation of the late eocene‐early Oligocene Izúcar de matamoros evaporites (Cuayuca Formation) in Mexico based on parsimony analysis of endemicity",2008,"10.1080/01916122.2008.9989660","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85008848445&doi=10.1080%2f01916122.2008.9989660&partnerID=40&md5=a28ecc4db0d947453b5b4201f2af0842","Based on the lithology of the Izucar de Matamoros (IzM) sections, and the occurrence of index taxa such as Armería, Cicatricosisporites dorogensis, Corsinipollenites, Eucommia, Momipites coryloides, Momipites tenuipolus, Mutisiapollis, and Ranuculacidites operculatus, a correlation between the IzM sections and the Cuayuca Formation stratotypes is proposed. The IzM sections are Late Eocene‐Early Oligocene, and they are part of the evaporitic member (Mcy) of the Cuayuca Formation. These new data are consistent with the paleoenvironmental interpretations proposed for the formation. It was probably deposited under local xeric conditions in a semiarid climate that allowed the development of grassland (Gramineae with Amaran thaceae‐Chenopodiaceae and Ephedra) and a thorn shrub community with Acacia, other Leguminosae, Linutn, and Plumbaginaceae. The neighboring communities were probably tropical deciduous forests, low tropical deciduous forest, thorn forest, and chaparral. There were also regional temperate vegetations such as a Picea‐Pinus forest, and a cloud forest community. Using parsimony analysis of endemicity, a biogeographic method, a palynofloristic relationship between the Cuayuca Formation and the Pie de Vaca Formation (Late Eocene‐Early Oligocene) is proposed. Both formations are within the Balsas Group, and are correlated with San Gregorio Formation (Oligocene) of southern Baja California. © 2008 Taylor & Francis Group, LLC. All rights reserved."
"14021882100;14021042100;22235963800;23029494800;","Regional yield estimation for winter wheat with MODIS-NDVI data in Shandong, China",2008,"10.1016/j.jag.2007.11.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-54849411536&doi=10.1016%2fj.jag.2007.11.003&partnerID=40&md5=504badb82a14eac21920876f79d5ccd2","The significance of crop yield estimation is well known in agricultural management and policy development at regional and national levels. The primary objective of this study was to test the suitability of the method, depending on predicted crop production, to estimate crop yield with a MODIS-NDVI-based model on a regional scale. In this paper, MODIS-NDVI data, with a 250 m resolution, was used to estimate the winter wheat (Triticum aestivum L.) yield in one of the main winter-wheat-growing regions. Our study region is located in Jining, Shandong Province. In order to improve the quality of remote sensing data and the accuracy of yield prediction, especially to eliminate the cloud-contaminated data and abnormal data in the MODIS-NDVI series, the Savitzky-Golay filter was applied to smooth the 10-day NDVI data. The spatial accumulation of NDVI at the county level was used to test its relationship with winter wheat production in the study area. A linear regressive relationship between the spatial accumulation of NDVI and the production of winter wheat was established using a stepwise regression method. The average yield was derived from predicted production divided by the growing acreage of winter wheat on a county level. Finally, the results were validated by the ground survey data, and the errors were compared with the errors of agro-climate models. The results showed that the relative errors of the predicted yield using MODIS-NDVI are between -4.62% and 5.40% and that whole RMSE was 214.16 kg ha-1 lower than the RMSE (233.35 kg ha-1) of agro-climate models in this study region. A good predicted yield data of winter wheat could be got about 40 days ahead of harvest time, i.e. at the booting-heading stage of winter wheat. The method suggested in this paper was good for predicting regional winter wheat production and yield estimation. © 2007 Elsevier B.V. All rights reserved."
"7005629694;35231062700;16052732300;23101573100;57209089997;24168883500;","Impacts of irrigation and anthropogenic aerosols on the water balance, heat fluxes, and surface temperature in a river basin",2008,"10.1029/2008WR006847","https://www.scopus.com/inward/record.uri?eid=2-s2.0-59749101063&doi=10.1029%2f2008WR006847&partnerID=40&md5=4d7ae46ab4df4bf01da02754a7c8def4","Changes in both land cover and the atmosphere have impacted the heat fluxes of south Asia in ways that may have altered the timing and magnitude of the monsoon. Century-long budgets of water and energy in the Krishna Basin (258,948 km2) in southern India demonstrate that irrigation impacted the sensible heat flux of the land surface (H) as much as or more than did the atmospheric brown cloud (ABC) over 1960-2005. Annual discharge of the Krishna River fell from 226 mm during pre-irrigation land cover (1901-1960) to 64 mm by 1990-2005, when 14-20% of the basin area was irrigated. Over the same period, annual evaporation increased by 166 ± 32 mm (+28%) causing H to decrease by 12.7 ± 2 W m-2 (-18%) compared to a decrease of 11.2 ± 1.8 W m-2 caused by the atmospheric brown cloud (ABC). The rate of change in H during irrigation expansion (1960-1990) was between -3.4 and -5.0 W m-2 per decade (da-1) due to irrigation expansion and -1.8 to -2.3 W m-2 da-1 due to the ABC. The trend in H caused by irrigation was negligible over 1990-2005 as irrigated area and evaporation stabilized. Previous work using the Parallel Climate Model estimated that the ABC decreased the latent heat flux by 2.4 W m-2; this decrease was more than offset by irrigation, resulting in a net increase in the latent heat flux of 12.9 W m-2. The maximum surface air temperature (Tmax) either decreased or remained the same in areas experiencing irrigation expansion but increased in a majority of unirrigated areas during the post-monsoon season. The results provide observational evidence that irrigation changed both the basin-scale sensible heat flux and surface air temperatures. Copyright 2008 by the American Geophysical Union."
"57203492395;","A simple model of coupled synoptic waves in the land surface and atmosphere of the northern Sahel",2008,"10.1002/qj.343","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049209833&doi=10.1002%2fqj.343&partnerID=40&md5=11392aa2945ad4e50e48ff979293fb3b","A simple dynamic model is developed to describe the observed interactions between the atmosphere and the soil moisture patterns of the northern Sahel. In the model, the atmosphere follows quasi-geostrophic dynamics, while land-atmosphere coupling is described by simple linear relationships. Dry surfaces heat the atmospheric boundary layer, while wet surfaces cool the boundary layer, relative to the equilibrium state of the atmosphere and land surface. In turn, cloud processes, which are assumed to maximise in the cool, humid phase of an atmospheric disturbance, cool the land surface through wetting (rainfall) and reduction of the incoming solar flux. These assumptions lead to a linear system which can be solved numerically to obtain modal solutions, and the adjoints (optimal excitation) of these. Moist convective influences on the atmospheric state are not explored in detail. The coupling with the land surface leads to the existence of unstable modes, which do not exist in the atmosphere-only part of the system. Solutions can be easterly or westerly propagating, according to wave number, with the longer waves tending to be easterly. Propagation relies on a favourable configuration between the atmospheric and soil moisture anomalies: easterly propagation requires the surface temperature pattern to be shifted to the east of the atmospheric temperature pattern. In contrast, optimal excitation of the fastest-growing mode occurs when the atmospheric pattern has a thermal anomaly lying to the east of a strong surface temperature (and moisture) anomaly. These results have value for weather prediction, and indicate the usefulness of soil moisture data for forecasters. Copyright © 2008 Royal Meteorological Society."
"7101933257;7005129538;7005809959;7006383649;","Chemical, microphysical and optical properties of primary particles from the combustion of biomass fuels",2008,"10.1021/es800943f","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57449098028&doi=10.1021%2fes800943f&partnerID=40&md5=cb347c4c759ff51eadf195cb4153c490","Biomass fuel combustion for residential energy significantly influences both emissions and the atmospheric burden of aerosols in world regions, i.e., east and south Asia. This study reports measurements of climate-relevant properties of particles emitted from biomass fuels widely used for cooking in south Asia, in laboratory experiments simulating actual cooking in the region. Fuel burn rates of 1-2 kg h-1 for wood species, and 1.5-2 kg h -1 for crop residues and dried cattle dung, influenced PM 2.5 emission factors which were 1.7-2 g kg-1 at low burn rates but 5-9 gkg-1 at higher burn rates. Total carbon accounted for 45-55% and ions and trace elements for 2-12% of PM2.5 mass. The elemental carbon (EC) content was variable and highest (22-35%) in particles emitted from low burn rate combustion (wood and jute stalks) but significantly lower (2-4%) from high burn rate combustion (dried cattle dung and rice straw). The mass absorption cross-section (MAC, m2 g-1) correlated with EC content for strongly absorbing particles. Weakly absorbing particles, from straw and dung combustion, showed absorption that could not be explained by EC content alone. On average, the MAC of biofuel emission particles was significantly higher than reported measurements from forest fires but somewhat lower than those from diesel engines, indicating potential to significantly influence atmospheric absorption. Both for a given fuel and across different fuels, increased burn rates result in higher emission rates of PM2.5, larger organic carbon (OC) content larger average particle sizes, and lower MAC. Larger mean particle size (0.42-1.31 μm MMAD) and organic carbon content, than in emissions from combustion sources like diesels, have potential implications for hygroscopic growth and cloud nucleation behavior of these aerosols. These measurements can be used to refine regional emission inventories and derive optical parametrizations, for climate modeling, representative of regions dominated by primary particles from biomass fuel combustion. © 2008 American Chemical Society."
"24071313700;7101867299;7101600670;7003525439;","A polarimetric radar forward operator for model evaluation",2008,"10.1175/2008JAMC1793.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65249089797&doi=10.1175%2f2008JAMC1793.1&partnerID=40&md5=b7b14d5ea457d54bfda55291b3747f31","A polarimetric radar forward operator has been developed as a tool for the systematic evaluation of microphysical parameterization schemes in high-resolution numerical weather prediction (NWP) models. The application of such a forward operator allows a direct comparison of the model simulations to polarimetric radar observations. While the comparison of observed and synthetic reflectivity gives information on the quality of quantitative precipitation forecasts, the information from the polarimetric quantities allows for a direct evaluation of the capacity of the NWP model to realistically describe the processes involved in the formation and interactions of the hydrometeors and, hence, the performance of the microphysical parameterization scheme. This information is expected to be valuable for detecting systematic model errors and hence improve model physics. This paper summarizes the technical characteristics of the synthetic polarimetric radar (SynPolRad). Different polarimetric radar quantities are computed from model forecasts using a T-matrix scattering code and ice phase hydrometeors are explicitly considered. To do so, the sensitivities of the scattering processes to the microphysical characteristics of different ice hydrometeors are investigated using sensitivity studies. Furthermore, beam propagation effects are considered, including attenuation and beam bending. The performance of SynPolRad and the consistence of the assumptions made in the derivation of the input parameters are illustrated in a case study. The resulting synthetic quantities as well as hydrometeor classification are compared with observations and are shown to be consistent with the model assumptions. © 2008 American Meteorological Society."
"7005703744;35302065900;","Evidence of the cloud lifetime effect from wildfire-induced thunderstorms",2008,"10.1029/2008GL035680","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60149097387&doi=10.1029%2f2008GL035680&partnerID=40&md5=794ee83a3880fd7bfae8fc0750571b13","A case study is presented of pyro-cumulonimbi (pyroCbs) forming over Canadian forest fires. Cloud-top ice effective radius values of these pyroCbs are significantly smaller than are those within surrounding convection. The smoke provides a massive source of cloud condensation nuclei (CCN), resulting in smaller cloud droplets which freeze homogeneously at temperatures around -40°C and produce very small ice crystals. It is also shown that the pyroCb anvils persist 6-12 hours longer than convectively-generated cirrus anvils from nearby convection. This provides evidence for the so-called cloud lifetime effect, an aerosol indirect effect identified by the most recent Intergovernmental Panel on Climate Change (IPCC) report."
"16309604700;7601492669;7401945370;9535769800;25647939800;7801685271;","Global cloud-system-resolving model NICAM successfully simulated the lifecycles of two real tropical cyclones",2008,"10.1029/2008GL036003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60149087760&doi=10.1029%2f2008GL036003&partnerID=40&md5=bc45ebd62d4697ec59bd29c57a7325c0","The increasing capability of high-end computers allows numerical simulations with horizontal resolutions high enough to resolve cloud systems in a global model. In this paper, initial results from the global Nonhydrostatic ICosahedral Atmospheric Model (NICAM) are highlighted to demonstrate the beginning of a potentially new era for weather and climate predictions with global cloud-system-resolving models. The NICAM simulation with a horizontal resolution of about 7 km successfully reproduced the lifecycles of two real tropical cyclones that formed in Indian Ocean in the austral summer 2006. Initialized with the atmospheric conditions 1-2 weeks before the cyclones genesis, the model captured reasonably not only the timing of the observed cyclone geneses but also their motions and mesoscale structures. The model provides a high temporal/spatial resolution dataset for detailed studies of mesoscale aspects of tropical cyclone genesis. These promising results suggest the predictability of tropical cyclones by high-resolution global cloud-system-resolving models. Copyright 2008 by the American Geophysical Union."
"7003875618;16550482700;36518090800;26022799400;26023533600;6602415577;26023119200;7006630889;","Change in ozone air pollution over Chicago associated with global climate change",2008,"10.1029/2007JD009775","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58849092704&doi=10.1029%2f2007JD009775&partnerID=40&md5=3254f419c02770e2ded8f942511edb30","This study uses statistical downscaling to estimate the impact of future climate change on air quality. We employ historical observations of surface ozone (O<inf>3</inf>) over the Chicago area, large-scale climate variables from the National Center for Environmental Protection (NCEP) reanalysis data, and climate projections from three GCMs (GFDL, PCM, and HadCM3), driven by two SRES emission scenarios (AlFI and B1 for GFDL and PCM; A2 and B1 for HadCM3). This approach calculates historic relationships between meteorology and O<inf>3</inf>, and considers how future meteorology would affect ground-level O<inf>3</inf> if these relationships remain constant. Ozone mixing ratios over Chicago are found to be most sensitive to surface temperature, horizontal surface winds, surface relative humidity, incoming solar radiation, and cloud cover. Considering the change in O<inf>3</inf> due to global climate change alone, summertime (June, July, and August) mean mixing ratios over Chicago are projected to increase by 6-17 ppb by the end of the century, depending on assumptions about global economic growth and choice of GCM. Changes are greater under higher climate emissions scenarios and more sensitive climate models (e. g. 24 ppb for GFDL AlFI as compared to 2 ppb for PCM B1). However, this approach does not take into account changes in O<inf>3</inf>-precursor emissions nor changes in local and lake-effect meteorology, which could combine with climate change to either enhance or diminish the projected change in local mixing ratios. Statistical downscaling is performed with the Statistical DownScaling Model (SDSM v. 4.1, a publicly available scientific analysis and decision-support tool. Copyright 2008 by the American Geophysical Union."
"6701518904;","Airborne water vapor lidar measurements",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-56249087252&partnerID=40&md5=6b3de274c2cb53c79ebab9354a0fadab","Airborne water vapor differential absorption lidar (DIAL) is an accurate new method to study a variety of meteorological phenomena such as latent heat fluxes in the convective boundary layer or the variability of upper tropospheric humidity in the tropics. These applications are very sensitive to measurement errors, and careful accuracy evaluations are mandatory. The dataset of the International H2O Project (IHOP_2002) gave a first opportunity for intercomparisons since three airborne lidar systems including the DLR DIAL participated. The overall biases between the lidar water vapor profiles are smaller than 10 % and confirm previous estimates of instrumental accuracies. Latent heat flux profiles in the convective boundary layer were obtained for the first time with this system and a wind lidar, both installed on board the DLR Falcon research aircraft during IHOP_2002 over the U.S. Southern Great Plains. The flux profiles range from 300 to 2500 m above ground and are computed from high spatial resolution (150 m horizontal and vertical) two-dimensional water vapor and vertical wind cross sections using the eddy covariance technique. A maximum of 700 ± 200 W/m2 is found at the boundary layer top, with a pronounced flux divergence indicative of boundary layer drying and consistent with observations by other instruments. The data allow statistical analyses of turbulence properties and a water vapor budget analysis, within the limits of the flux sampling uncertainty (55 %), instrument noise (15 %) and systematic uncertainties (7 %) encountered in that case study. Water vapor measurements in the tropical upper troposphere are a prerequisite to better understand the processes that govern stratospheric water vapor concentrations and trends in the context of a changing climate. They are sparse because of instrumental shortcomings and observational challenges. Therefore, the DLR DIAL participated in the Tropical Convection, Cirrus and Nitrogen Oxides Experiment (TROCCINOX) in 2004 and 2005 in Brazil to perform the first aircraft DIAL measurements in the tropical upper troposphere and the mid-latitudes lower stratosphere. A sensitivity analysis reveals that the DIAL profiles have an accuracy of ~5 % within altitudes of 8 and 16 km, and intercomparisons with in situ instruments confirm this encouraging result. In particular, the DIAL is found to have no altitude- or latitude-dependent bias. The DIAL profiles exhibit a smooth exponential decrease in water vapor mixing ratio in the tropical tropopause layer at altitudes from 11 km up to 16 km where the hygropause is located at a minimum mixing ratio of ∼2.5 μmol/mol. A high-resolution (2 km horizontal, ∼200 m vertical) DIAL cross section through the anvil outflow region of tropical convection shows that the ambient humidity is increased by a factor of three across 100 km. A promising platform for DIAL in the future is a low Earth orbit satellite. Space-borne integrated path differential absorption lidar would allow global observations of carbon dioxide, methane and nitrous oxide, important greenhouse gases whose concentrations are severely influenced by human activities. Measurements in the wings of absorption lines can provide column concentration measurements with a weighting function peaking near the surface. Performance simulations reveal that moderate-size instruments with a telescope aperture of 0.5 - 1.5 m and an average laser power of 0.4 4 W are basically able to fulfill the observational requirements of the scientific community for the analysis of surface greenhouse gas sources and sinks. The resulting measurement accuracy is 0.2 - 0.4 % for carbon dioxide, 0.4 - 0.6 % for methane and 0.3 % for nitrous oxide. A sensitivity analysis investigates various potential sources of systematic errors that amount to 0.08 % for carbon dioxide. Although challenging instrument requirements still exist, spaceborne DIAL can become a reality thanks to the steady improvement of laser accuracy, efficiency, and reliability. The general objective of this thesis is to document the quality of present airborne and future spaceborne DIAL and to highlight examples of meteorological applications."
"36882528600;7003795219;55921755700;6701869931;18634433100;55545860972;7103277028;18635797200;35374156800;18633617600;7202489497;35372923700;","Aerosols and clouds in the upper troposphere-lower stratosphere region detected by GOMOS and ACE: Intercomparison and analysis of the years 2004 and 2005",2008,"10.1016/j.asr.2007.09.027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649092145&doi=10.1016%2fj.asr.2007.09.027&partnerID=40&md5=96c7affe50797af8ed28c68190e3b1e6","Satellite-based limb occultation measurements are well suited for the detection and mapping of polar stratospheric clouds (PSCs) and cirrus clouds. PSCs are of fundamental importance for the formation of the Antarctic ozone hole that occurs every year since the early 1980s in Southern Hemisphere spring. Despite progress in the observation, modeling and understanding of PSCs in recent years, there are still important questions which remain to be resolved, e.g. PSC microphysics, composition, formation mechanisms and long-term changes in occurrence. In addition, it has recently become clear that cirrus clouds significantly affect the global energy balance and climate, due to their influence on atmospheric thermal structure. Since 2002, two major space missions using the occultation method have been put into orbit: the European stellar occultation spectrometer GOMOS on board ENVISAT and the Canadian solar occultation instruments ACE-FTS/MAESTRO on board SCISAT-I. PSCs and cirrus clouds are detected both by ACE and GOMOS. The results of an intercomparison between retrieved aerosol extinction, PSCs and cirrus clouds are the subject of this paper. The cloud data are also used to examine the evolution of PSCs over the Antarctic vortex and the latitudinal variation of tropical cirrus for the years 2004 and 2005. © 2007 COSPAR."
"24737203600;56744278700;","Absorbing aerosols over Asia: A Geophysical Fluid Dynamics Laboratory general circulation model sensitivity study of model response to aerosol optical depth and aerosol absorption",2008,"10.1029/2008JD010140","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58249092830&doi=10.1029%2f2008JD010140&partnerID=40&md5=2bac94bb4706df4085af9eec9155c3cc","Forcing by absorbing atmospheric black carbon (BC) tends to heat the atmosphere, cool the surface, and reduce the surface latent and sensible heat fluxes. BC aerosol can have a large impact on regional climates and the hydrologic cycle. However, significant uncertainties remain concerning the increases in (1) the total amount of all aerosol species and (2) the amount of aerosol absorption that may have occurred over the 1950-1990 period. Focusing on south and east Asia, the sensitivity of a general circulation model's climate response (with prescribed sea surface temperatures and aerosol distributions) to such changes is investigated by considering a range of both aerosol absorption and aerosol extinction optical depth increases. We include direct and semidirect aerosol effects only. Precipitation changes are less sensitive to changes in aerosol absorption optical depth at lower aerosol loadings. At higher-extinction optical depths, low-level convergence and increases in vertical velocity overcome the stabilizing effects of absorbing aerosols and enhance the monsoonal circulation and precipitation in northwestern India. In contrast, the presence of increases in only scattering aerosols weakens the monsoonal circulation and inhibits precipitation here. Cloud amount changes can enhance or counteract surface solar flux reduction depending on the aerosol loading and absorption, with the changes also influencing the surface temperature and the surface energy balance. The results have implications for aerosol reduction strategies in the future that seek to mitigate air pollution concerns. At higher optical depths, if absorbing aerosol is present, reduction of scattering aerosol alone has a reduced effect on precipitation changes, implying that reductions in BC aerosols should be undertaken at the same time as reductions in sulfate aerosols. Copyright 2008 by the American Geophysical Union."
"7202625046;7403232646;7004091067;36962132100;7006029393;","Intercomparison of integrated water vapor retrievals from SSM/I and COSMIC",2008,"10.1029/2008GL035126","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57149134011&doi=10.1029%2f2008GL035126&partnerID=40&md5=a7016932dae09bdd03987a1b7d6f181b","Integrated water vapor (IWV) estimates derived from four different Special Sensor Microwave Imager (SSM/1) algorithms are collocated and compared with IWV retrievals using Global Positioning System radio occultation (GPSRO) soundings from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission. The values exhibit strong overall agreement lending support for the accuracy of both the COSMIC data and the traditional passive microwave IWV products. Differences among the products varying with latitude, cloud liquid water content, rain rate, and wind speed highlight key differences between the SSM/I algorithms. Additional differences related to the coarser COSMIC spatial resolution are also observed but are independent from the other dependencies. The differences appear independent of the bottom altitude of the GPSRO soundings. The results suggest a new method of quantifying the uncertainty in individual IWV retrievals as functions of coincident environmental parameters for application to data assimilation and numerical weather prediction. Copyright 2008 by the American Geophysical Union."
"6602075624;57207511394;8219523500;7003539192;","Trends and interannual variability in surface UVB radiation over 8 to 11 years observed across the United States",2008,"10.1029/2008JD009826","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58249088332&doi=10.1029%2f2008JD009826&partnerID=40&md5=055de3b3d9ba4a9e1351213aa3b8701b","The United States Department of Agriculture UVB Monitoring and Research Program maintains a network of Yankee Environmental Systems surface UVB-1 meters distributed throughout the United States. We analyzed behavior of surface UVB radiation (280-320 nm) over 8 to 10 years measured at eight stations within this network that were selected because of their early deployment (ranging from 1995 to 1997). These eight stations represent different climates, latitudes, and land cover types. We characterized differences in instrument sensitivity and drift through a methodology that utilized regular laboratory calibrations of field instruments and calibration of standard meters to spectroradiometers. From 3-minute observations, we computed mean annual and mean monthly irradiances at each site to study trends and interannual variability in UVB irradiance. Annual irradiance changes ranged from -5% per decade to +2% per decade across the sites. Confidence intervals were computed with a statistical model that included autocorrelation and measurement uncertainty. Resulting 95% confidence intervals were large and included 0, partly as a result of the short time series. We calculated trends at each site for individual months (for January, February, etc.), which are important for assessing effects on human health, crops, and other organisms whose sensitivity to UVB exposure changes seasonally. Positive and negative monthly trends of different magnitudes were measured, although trends in most months at most sites were not statistically significant from 0. The largest absolute changes were generally in spring, summer, and fall, and large relative trends occurred in winter in most locations compared with other seasons. Interannual variability of surface UVB radiation was 2% to 5% of the mean. Our study illustrates that, using a well-calibrated instrument record, the 10 years beginning around 1995 did not show significant trends in surface UVB irradiance at stations across the United States. Our observed range of trends occurred during a period of generally increasing midlatitude colunm ozone, suggesting that changing cloud, aerosol, and snow conditions were responsible for driving surface radiation variability in addition to ozone trends. Copyright 2008 by the American Geophysical Union."
"6602310241;7006443753;7006093018;","The assimilation of cloud-affected infrared satellite radiances for numerical weather prediction",2008,"10.1002/qj.243","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55349143540&doi=10.1002%2fqj.243&partnerID=40&md5=5e44d5031152090d19b4dce8d6526ea0","A practical technique for the assimilation of cloud-affected infrared radiances is presented. The technique is best suited to advanced infrared sounders such as AIRS and IASI. Radiances are first pre-processed by a one-dimensional variational analysis (1D-Var) scheme, where cloud parameters (cloud-top pressure and effective cloud fraction) are retrieved simultaneously with atmospheric profile variables. The retrieved cloud parameters are then passed to a variational data assimilation system, where they are used to constrain the radiative transfer calculation in the assimilation of a reduced set of channels. The channel selection is chosen to reduce the sensitivity to errors in the forward modelling of radiation originating below the cloud top. The performance of this technique is explored by means of a 1D-Var study using simulated measurements. It is demonstrated that the technique has the potential to allow the assimilation of a significant proportion of cloud-affected infrared sounding measurements, possibly bringing valuable benefits to an operational NWP system. © Crown Copyright 2008."
"57218273453;7601492669;56962915800;7402989545;","Sensitivity of the Grid-point Atmospheric Model of IAP LASG (GAMIL1.1.0) climate simulations to cloud droplet effective radius and liquid water path",2008,"10.1007/s00376-008-0529-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55349087930&doi=10.1007%2fs00376-008-0529-z&partnerID=40&md5=7e584b650a5d68fa03f4f23c9ab4dd43","This paper documents a study to examine the sensitivity to cloud droplet effective radius and liquid water path and the alleviation the energy imbalance at the top of the atmosphere and at the surface in the latest version of the Grid-point Atmospheric Model of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP) (GAMIL1.1.0). Considerable negative biases in all flux components, and thus an energy imbalance, are found in GAMIL1.1.0. In order to alleviate the energy imbalance, two modifications, namely an increase in cloud droplet effective radius and a decrease in cloud liquid water path, have been made to the cloud properties used in GAMIL. With the increased cloud droplet effective radius, the single scattering albedo of clouds is reduced, and thus the reflection of solar radiation into space by clouds is reduced and the net solar radiation flux at the top of the atmosphere is increased. With the reduced cloud optical depth, the net surface shortwave radiation flux is increased, causing a net warming over the land surface. This results in an increase in both sensible and latent heat fluxes over the land regions, which is largely balanced by the increased terrestrial radiation fluxes. Consequently, the energy balance at the top of atmosphere and at the surface is achieved with energy flux components consistent with available satellite observations. © Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH 2008."
"9241548900;7103060756;","Empirical estimates of global climate sensitivity: An assessment of strategies using a coupled GCM",2008,"10.1007/s00376-008-0339-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55349118850&doi=10.1007%2fs00376-008-0339-3&partnerID=40&md5=185b43d54a2c1b587c5322948b5bb021","A control integration with the normal solar constant and one with it increased by 2.5% in the National Center for Atmospheric Research (NCAR) coupled atmosphere-ocean Climate System Model were conducted to see how well the actual realized global warming could be predicted just by analysis of the control results. This is a test, within a model context, of proposals that have been advanced to use knowledge of the present day climate to make ""empirical"" estimates of global climate sensitivity. The scaling of the topof-the-atmosphere infrared flux and the planetary albedo as functions of surface temperature was inferred by examining four different temporal and geographical variations of the control simulations. Each of these inferences greatly overestimates the climate sensitivity of the model, largely because of the behavior of the cloud albedo. In each inference the control results suggest that cloudiness and albedo decrease with increasing surface temperature. However, the experiment with the increased solar constant actually has higher albedo and more cloudiness at most latitudes. The increased albedo is a strong negative feedback, and this helps account for the rather weak sensitivity of the climate in the NCAR model. To the extent that these model results apply to the real world, they suggest empirical evaluation of the scaling of global-mean radiative properties with surface temperature in the present day climate provides little useful guidance for estimates of the actual climate sensitivity to global changes. © Science Press 2008."
"7601345593;7501757094;","Diurnal-to-seasonal characteristics of surface energy balance and temperature in East Asian summer monsoon simulations",2008,"10.1007/s00703-008-0009-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56749163353&doi=10.1007%2fs00703-008-0009-0&partnerID=40&md5=1cde11ea6366284895a07cc30f3bbdb9","We used regional climate model simulations of the East Asian Summer Monsoon (EASM) to study diurnal-to-seasonal characteristics of the surface energy balance and temperature, and their relationships to clouds and surface soil moisture. Simulations were performed for the period May through September 1988 and 1989, 2 years with significant differences in observed surface air temperature, radiation, and clouds over the Yangtze-Huai River Valley (YHRV), which are realistically reproduced by the model. Differences in daytime evolutions of the YHRV surface net radiation, heat fluxes, and surface air temperature between 2-year summers result mainly from fluctuation of shortwave cloud radiative forcing. Clouds dominate daily variability of the YHRV surface net solar radiation, surface net radiation, and latent heat, generally accounting for above 80% of the total variances. Consequently, they are more effective in damping the diurnal temperature range by reducing daytime maximum temperature as compared to surface soil moisture. Both clouds and soil moisture exhibit small effects on nighttime minimum temperature, which is largely controlled by the greenhouse effect of the atmospheric water vapor. Surface energy balance components and temperature evolve with the march of EASM, which is quite different between 2 years. The comparative analyses of observations and other available data can generally validate the major conclusions from the simulations. © Springer-Verlag 2008."
"57202891769;7003278104;","An improved parameterization for simulating Arctic cloud amount in the CCSM3 climate model",2008,"10.1175/2008JCLI2299.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649086637&doi=10.1175%2f2008JCLI2299.1&partnerID=40&md5=07bb7d6e56b4ffed704ccaf242f8e55b","A simple alternative parameterization for predicting cloud fraction in the Community Climate System Model, version 3 (CCSM3) global climate model is presented. This formula, dubbed ""freeezedry,"" is designed to alleviate the bias of excessive low clouds during polar winter by reducing the cloud amount under very dry conditions. During winter, freezedry decreases the low cloud amount over the coldest regions in high latitudes by over 50% locally and more than 30% averaged across the Arctic. The cloud reduction causes an Arctic-wide drop of 15 W m-2 in surface cloud radiative forcing (CRF) during winter and about a 50% decrease in mean annual Arctic CRF. Consequently, wintertime surface temperatures fall by up to 4 K on land and 2-8 K over the Arctic Ocean, thus significantly reducing the model's pronounced warm bias. Freezedry also affects CCSM3's sensitivity to greenhouse forcing. In a transient-CO2 experiment, the model version with freezedry warms up to 20% less in the North Polar and South Polar regions (1.5- and 0.5-K-smaller warming, respectively). Paradoxically, the muted high-latitude response occurs despite a much larger increase in cloud amount with freezedry during nonsummer months (when clouds warm the surface), apparently because of the colder modern reference climate. While improving the polar climate simulation in CCSM3, freezedry has virtually no influence outside of very cold regions and has already been implemented in another climate model, the Global Environmental and Ecological Simulation of Ecological Systems, version 1 (GENESIS1). Furthermore, the simplicity of this parameterization allows it to be readily incorporated into other GCMs, many of which also suffer from excessive wintertime polar cloudiness. © 2008 American Meteorological Society."
"56676874900;6602230939;","Potential biases in feedback diagnosis from observational data: A simple model demonstration",2008,"10.1175/2008JCLI2253.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349107460&doi=10.1175%2f2008JCLI2253.1&partnerID=40&md5=4a3d095f97f1c21edebdab0a976064c3","Feedbacks are widely considered to be the largest source of uncertainty in determining the sensitivity of the climate system to increasing anthropogenic greenhouse gas concentrations, yet the ability to diagnose them from observations has remained controversial. Here a simple model is used to demonstrate that any nonfeedback source of top-of-atmosphere radiative flux variations can cause temperature variability, which then results in a positive bias in diagnosed feedbacks. This effect is demonstrated with daily random flux variations, as might be caused by stochastic fluctuations in low cloud cover. The daily noise in radiative flux then causes interannual and decadal temperature variations in the model's 50-m-deep swamp ocean. The amount of bias in the feedbacks diagnosed from time-averaged model output depends upon the size of the nonfeedback flux variability relative to the surface temperature variability, as well as the sign and magnitude of the specified (true) feedback. For model runs producing monthly shortwave flux anomaly and temperature anomaly statistics similar to those measured by satellites, the diagnosed feedbacks have positive biases generally in the range -0.3 to 0.8 W m2 K-61. These results suggest that current observational diagnoses of cloud feedback - and possibly other feedbacks - could be significantly biased in the positive direction. © 2008 American Meteorological Society."
"6506784765;7004164175;16187255400;","Holocene and Last Interglacial cloudiness in eastern Baffin Island, Arctic Canada",2008,"10.1139/E08-053","https://www.scopus.com/inward/record.uri?eid=2-s2.0-59349091694&doi=10.1139%2fE08-053&partnerID=40&md5=caa57024ea205e9d24facc644406a10d","This study presents Last Interglacial and Holocene vegetation and climate changes at Fog Lake (67°11'N, 63°15'W) on eastern Baffin Island, Arctic Canada. The vegetation cover is reported as vegetation structural types (or biomes). July air temperature and sunshine during the growing season (June-July-August-September) were reconstructed from pollen assemblages using the modern analogue technique. The vegetation of the Last Interglacial period evolved from a prostrate dwarf-shrub tundra to a low- and high-shrub tundra vegetation. The succession of four Arctic biomes was distinguished from the Last Interglacial sediments, whereas only one Arctic biome was recorded in the Holocene sediments. From ca. 8300 cal. years BP to present, hemiprostrate dwarf-shrub tundra occupied the soils around Fog Lake. During the Last Interglacial, growing season sunshine was higher than during the Holocene and July air temperature was 4 to 5 °C warmer than present. A principal component analysis helped in assessing relationship between floristic gradients and climate. The major vegetation changes through the Last Interglacial and Holocene were driven by July air temperature variations, whereas the minor, or subtle, vegetation changes seem rather correlated to September sunshine. This study demonstrates that growing season sunshine conditions can be reconstructed from Arctic pollen assemblages, thus providing information on feedbacks associated with cloud cover and summer temperatures, and therefore growing season length. © 2008 NRC."
"7103123474;7101952183;7102363926;","Titan's tropical storms in an evolving atmosphere",2008,"10.1086/593117","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349154003&doi=10.1086%2f593117&partnerID=40&md5=263bd6a5443fb55144244ee9ef65f262","The Huygens probe landed in a damp lake bed fed by fluvial channels, indicative of past rainfall. Such washes, interspersed with vast dunes, are typical of Titan's tropical landscape. Yet, Cassini-Huygens measurements reveal a highly stable tropical atmosphere devoid of deep convective storms, and the formation of washes in dune fields is not understood. Here we examine the effects of seasonal variations in humidity, surface heating, and dynamical forcing on the stability of Titan's troposphere. We find that during the probe landing, the middle troposphere was weakly unstable to convection, consistent with the tenuous cloud detected at 21 km. Yet the tropical atmosphere, at any season, is too stable to produce deep convective storms. Convection in the tropics remains weak and confined to altitudes below ∼30 km, unless the humidity is increased below 9 km altitude. Solar heating is insufficient to significantly humidify the tropical atmosphere. The large polar lakes are seasonably stable, and the methane column abundance measured by Huygens typical of the tropical atmosphere. Our study indicates the presence of distinct polar and equatorial climates. It also suggests that fluvial features in the tropics do not result from recent seasonal rainstorms, and thereby supports other origins such as geological seepage, cryovolcanism, or a wetter climate in the past. © 2008. The American Astronomical Society. All rights reserved."
"6507367907;6603148342;7402530860;","A simplified model to predict diurnal water temperature dynamics in a shallow tropical water pool",2008,"10.1007/s00484-008-0173-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-54349105106&doi=10.1007%2fs00484-008-0173-4&partnerID=40&md5=d19ea0cdf87cc25d8719ad96a1005c52","Water temperature is a critical regulator in the growth and development of malaria mosquito immatures, as they are poikilothermic. Measuring or estimating the diurnal temperature ranges to which these immatures are exposed is of the utmost importance, as these immatures will develop into adults that can transmit malaria. Recent attempts to predict the daily water temperature dynamics in mosquito breeding sites in Kenya have been successful. However, the developed model may be too complex, as the sophisticated equipment that was used for detailed meteorological observations is not widely distributed in Africa, making it difficult to predict the daily water temperature dynamics on a local scale. Therefore, we compared two energy budget models with earlier made observations of the daily water temperature dynamics in a small, shallow and clear water pool (diameter 0.96 m, depth 0.32 m) in Kenya. This paper describes (1) a complex 1-Dimensional model, and (2) a simplified second model, and (3) shows that both models mimic the water temperature dynamics in the water pool accurately. The latter model has the advantage that it only needs common weather data (air temperature, air humidity, wind speed and cloud cover) to estimate the diurnal temperature dynamics in breeding sites of African malaria mosquitoes. © 2008 The Author(s)."
"14064336400;56225227300;56510309600;6507786862;7005470229;","Study of dew water collection in humid tropical islands",2008,"10.1016/j.jhydrol.2008.07.038","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53149126805&doi=10.1016%2fj.jhydrol.2008.07.038&partnerID=40&md5=7ae8b2228639d36cf95d17573cfcb0a8","An assessment of the potential for dew water to serve as a potable water source during a rainless season in a humid tropical climate was carried out in the Pacific islands of French Polynesia. The climate of these islands, in terms of diurnal and seasonal variations, wind and energy balance, is representative of the climate of the tropical Atlantic and Pacific oceans. Measurements were obtained at two characteristic sites of this region; a mountainous island (Punaauia, Tahiti Island) and an atoll (Tikehau, Tuamotu Archipelago). Dew was measured daily on a 30° tilted, 1 m2 plane collector equipped with a thermally insulated radiative foil. In addition, an electronic balance placed at 1 m above the ground with a horizontal 0.16 m2 condensing plate made of PolyTetraFluoroEthylene (Teflon) was used in Tahiti. Dew volume data, taken during the dry season from 16/5/2005 to 14/10/2005, were correlated with air temperature and relative humidity, wind speed, cloud cover and visible plus infrared radiometer measurements. The data were also fitted to a model. Dew formation in such a tropical climate is characterized by high absolute humidity, weak nocturnal temperature drop and strong Trade winds. These winds prevent dew from forming unless protected e.g. by natural vegetal windbreaks. In protected areas, dew can then form with winds as large as 7 m/s. Such strong winds also hamper at night the formation near the ground of a calm and cold air layer with high relative humidity. As the cooling power is lower than in the Mediterranean islands because of the high absolute humidity of the atmosphere, both effects combine to generate modest dew yields. However, dew events are frequent and provide accumulated amounts of water attractive for dew water harvesting. Slight modifications of existing rain collection devices on roofs can enhance dew formation and collection. Dew harvesting thus appears as an attractive possibility to provide the local population with a complementary - but on occasion, essential - water resource. © 2008 Elsevier B.V. All rights reserved."
"55688930000;7004242319;","Modeling aerosol effects on shallow cumulus convection under various meteorological conditions observed over the Indian Ocean and implications for development of mass-flux parameterizations for climate models",2008,"10.1029/2008JD009914","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58149213963&doi=10.1029%2f2008JD009914&partnerID=40&md5=97dbe01b79d7a8a08ec457523997c37f","To determine conditions over the Indian Ocean, under which cloud fields are most susceptible to modification from aerosols, and to study how turbulent activities and shallow cumuli vary for different meteorological scenarios, a three-dimensional large-eddy simulation model was initialized using data collected during the Indian Ocean Experiment (INDOEX). Radiosonde data were used to construct six soundings encompassing the range of temperature and humidity observed. A total of 18 meteorological scenarios were then obtained by adding either an average transition layer (TL), a strong inversion layer (IL), or no stable layer to each sounding. Separate simulations were conducted for each scenario assuming pristine or polluted conditions as observed during INDOEX. For aerosol profiles measured during INDOEX, aerosol semidirect effects always dominated indirect effects, with the positive daytime net indirect forcing (semidirect plus indirect forcings) varying between 0.2 and 4.5 W m-2. Anthropogenic aerosols had a larger net indirect forcing when the environmental relative humidity (RH) was higher and in the absence of the IL and TL. Changes in meteorological factors had larger impacts on the cloud properties than did anthropogenic aerosols, indicating large uncertainties can be introduced when solely using observations to quantify aerosol effects without examining their meteorological context. Because mean lateral detrainment and entrainment rates depended on RH, aerosols, and the presence of stable layers, mass-flux parameterizations in climate models should not use single values for such rates that may not represent the range of conditions observed where trade cumuli form. Copyright 2008 by the American Geophysical Union."
"7003937407;7102652925;","On the sensitivity of cloud-to-ground lightning activity to surface air temperature changes at different timescales in São Paulo, Brazil",2008,"10.1029/2008JD009841","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58149252064&doi=10.1029%2f2008JD009841&partnerID=40&md5=a7ea20986e19802aa67b14f776e97816","This paper presents a study about the sensitivity of cloud-to-ground (CG) lightning activity to changes in surface air temperature at daily, monthly, yearly, and decadal timescales in the city of São Paulo (Brazil). Lightning data collected in the city by the Brazilian Lightning Detection Network (BrasilDat) from 1999 to 2006 and thunderstorm day data obtained ftom 1951 to 2006 were analyzed and compared with surface air temperature data. The lightning activity increases significantly with increasing temperature, with a sensitivity of approximately 40% per 1°C for daily and monthly timescales and approximately 30% per 1°C for decadal timescale. For the yearly timescale, the increase is not statistically significant. The lower sensitivity for the decadal timescale suggests that the lightning sensitivity to changes in surface air temperature decreases for larger timescales, in agreement with what is expected on the basis of convective adjustment. The decadal lightning sensitivity found in this study is in reasonable agreement with the increase in the global lightning activity estimated by most climate models. The study is the first to investigate in detail this relationship in a large urban area inside the tropics and should contribute to the effort to understand the impact of the global warming on lightning activity. Copyright 2008 by the American Geophysical Union."
"7005650812;55915206300;","Contribution of water vapor to observational estimates of longwave cloud radiative forcing",2008,"10.1029/2008JD010053","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58149215825&doi=10.1029%2f2008JD010053&partnerID=40&md5=5fbf6d35d28f44bc9f4c7d0a370cb240","It has been long recognized that cloud-free regions are typically associated with drier air, whereas cloudy regions typically are associated with more moisture. Using Advanced Microwave Scanning Radiometer (AMSR-E) passive microwave observations, we estimated the bias between water vapor path (WVP) of clear-sky and all-sky conditions. Furthermore, we assessed the impact of these biases on longwave cloud radiative forcing (CRF). Results indicate that, in a zonal mean sense, the difference between all-sky and clear-sky WVP estimates is around 2 mm, with highest values in the midlatitudes summer, where differences up to 7 mm occur. The corresponding CRF change forced by these WVP changes is about 2 W m-2 in a zonal mean sense. Highest values occur in the midlatitudes of the northern hemisphere in which a magnitude up to 6 W m-2 is shown. Over the convectively active regions, the WVP contributed CRF appears to be smaller than 5 W M-2, substantially smaller than the CRF contributed by upper tropospheric water vapor only, suggesting that a significant portion of satellite-estimated CRF over the tropics is contributed by the redistribution of water vapor associated with convection development. Copyright 2008 by the American Geophysical Union."
"8571512400;6603639908;7005561168;7006752044;24339339100;","Climate of Russia in the 21st Century. Part 2. Verification of atmosphere - Ocean general circulation models CMIP3 for projections of future climate changes",2008,"10.3103/S1068373908080013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-54149113339&doi=10.3103%2fS1068373908080013&partnerID=40&md5=5da415f4e7f5f8a762f4bce15ab3106d","Results of simulation of radiation, cloud cover, surface air temperature, sea-level pressure, and hydrological regime components for Russia with the help of an ensemble of CMIP3 global climate models is analyzed. Despite a large spread among the models, the CMIP3 AOGCM ensemble simulations of the key characteristics of the observed surface climate agree well with observations, anyway in averaging over areas of vast regions, from watersheds of large rivers to the whole of Russia. These means (ensemble-and area-averaged values) often fall into the range of estimates derived from observations. This suggests the existence of uncertainty in the estimates obtained from simulations as well as from observational data. Comparison of different-generation models demonstrates a gradual improvement of the AOGCM simulation of surface climate characteristics. In general, the averaging over the CMIP3 AOGCM ensemble allows us to state that the ensemble is suitable for estimates of future climate changes. © Allerton Press, Inc. 2008."
"6602118778;6603314018;7401924080;","Origin and significance of loess in late Paleozoic western Pangaea: A record of tropical cold?",2008,"10.1016/j.palaeo.2008.03.050","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53049086669&doi=10.1016%2fj.palaeo.2008.03.050&partnerID=40&md5=12b64caa3a7f6386d90a8efda2287926","Loess is abundant today, primarily in mid- to high-latitude regions, and is well recognized as a high-fidelity archive of terrestrial climate change. Much of this 'Quaternary' loess is linked either directly or indirectly to glacial and associated cold-weathering processes, as such processes are highly effective in generating the silt size so characteristic of loess. Loess deposits have been poorly documented in the pre-Quaternary record, but are increasingly well recognized in the late Paleozoic of western equatorial Pangaea, particularly in and surrounding the region of the Ancestral Rocky Mountains of western North America. Siltstone deposits here range from true 'loessite' to eolian silt that ultimately accumulated in a variety of continental and marine environments. These strata include the thickest 'dust' deposits yet documented in the geologic record. Following the lower to middle Paleozoic record of carbonate deposition that prevailed over much of western equatorial Pangaea, silt first appeared in the latest Devonian, became widespread in the late Carboniferous (Pennsylvanian), and persisted, but with diminishing importance, through the Permian. Atmospheric 'dustiness' clearly varied on a high-frequency scale as well, evinced by, e.g. loessite-paleosol couplets or by variations in silt content of (glacioeustatic) stratigraphic 'cycles' that formed isolated from all but atmospherically derived detrital influx. Silt-rich units of this time interval are well sorted and blanket-like, with a mineralogical and geochemical composition that is, in many regions, characterized by immaturity. Detrital zircon data from several silt-rich (loessitic) accumulations within the Ancestral Rocky Mountains indicate significant first-cycle derivation from Precambrian basement composed of remarkably coarse-grained protoliths. The great volume, mineralogical and geochemical immaturity, basement derivation, and the timing that coincides with pulses of major Gondwanan cold (glacial) episodes are all most readily reconciled with silt genesis via glacial and associated cold-weathering processes, a hypothesis consistent with emerging indications of glacial and cold-weathering phenomena in the low-latitude Ancestral Rocky Mountains region. Such a concentration of loess in the tropics is remarkably nonuniformitarian and, we hypothesize, reflects a tropical climate system that was at times oddly cold and semi-arid. Beyond its importance as a climatic archive, eolian 'dust' also acts as a potentially potent agent of climate change, e.g. through effects on radiative forcing, cloud and storm formation, and through the biogeochemical repercussions of dusting marine and terrestrial ecosystems with such a large volume of highly chemically reactive and nutrient-bearing material. The late Paleozoic interval may well rank as the dustiest in Earth history, and thus yield important insights to the causes and consequences of mineral aerosols on Earth System processes and feedbacks of our most recent pre-Quaternary icehouse. © 2008 Elsevier B.V. All rights reserved."
"25029067300;7201789575;","Julian dates and introduced temporal error in remote sensing vegetation phenology studies",2008,"10.1080/01431160802235829","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52649123829&doi=10.1080%2f01431160802235829&partnerID=40&md5=9a17c6ef30e52a211df5cb4af15ec087","Remote-sensing-based vegetation phenology studies are commonly used to study agriculture, forestry, species distributions, and the effect of climate change on vegetation. These studies utilize annual time series of NDVI data to characterize seasonal growth patterns. The NDVI data for most of these studies have been pre-processed using a maximum value compositing process to minimize contamination from clouds. A side effect of this process is a degradation of temporal data, since NDVI values are assigned to multiday periods rather than the specific date of image capture. In this study, the compositing process is examined to determine if there is a reliable pattern to pixel selection. Also, the magnitude of the introduced error is estimated by comparing vegetation phenology metrics calculated using the temporally degraded data and metrics calculated using the actual date of each pixel. The root mean square errors between these datasets ranged from 9.4 to 10.9 days, much larger than is acceptable for most phenology studies. We conclude that vegetation phenology studies must make use of accurate temporal data to characterize changes in vegetation seasonality."
"57199033967;7004057920;","Retrieving optical depths of optically thin and mixed-phase clouds from MFRSR measurements",2008,"10.1029/2008JD009958","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68149112498&doi=10.1029%2f2008JD009958&partnerID=40&md5=c5ab6917e8ce59c68be03de5d02a3cb0","A new method has been developed to retrieve cloud optical depths for optically thin clouds (τ < 10) from the Multifilter Rotating Shadowband Radiometer (MFRSR). On the basis of simultaneous measurements of direct and diffuse radiation from MFRSR, this method allows partition of water and ice clouds and thus improves cloud optical depth retrievals. The new retrieval algorithm achieves the high consistency of retrieved cloud optical depth from both direct-beam and total radiation: the slope of 0.95 between the two with correlation coefficient of 0.90 and RMS of 1.00. A sensitivity study illustrates that the maximum biases (relative errors) of cloud optical depth within the range of effective radius of clouds are 0.16 (4.7%) and 0.36 (8.3%) for retrievals from direct-beam radiation and from total radiation, respectively. Validation and evaluation from measurements at the Point Reyes site have been conducted, illustrating that the new retrieval algorithm provides not only accurate retrievals of cloud optical depth in terms of radiation closure but also unique mix ratio of cloud water and ice for optically thin clouds under overcast conditions. Because of the importance of thin clouds, this algorithm with unique mix ratio retrievals is important for the climate study. Copyright 2008 by the American Geophysical Union."
"55709582600;7202145115;","Spatial and temporal dependence of clouds and their radiative impacts on the large-scale vertical velocity profile",2008,"10.1029/2007JD009722","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549094044&doi=10.1029%2f2007JD009722&partnerID=40&md5=98d1d4484e8e74a54e1f77771223bd53","The structure of tropical large-scale vertical velocity from the European Centre for Medium-Range Weather Forecasts Re-Analysis is compared with simultaneous satellite measurements of precipitation, top of atmosphere radiation, and clouds from the Tropical Rainfall Measuring Mission (TRMM) on timescales ranging from hours to months. The first two empirical orthogonal functions of the vertical velocity profile represent the traditional deep circulation (PC1) and a shallower circulation (PC2) associated with middle-level divergence. Together they explain 90% of total variance and can distinguish two types of upward and downward motion: ""top heavy"" and ""bottom heavy."" Cloud and radiation budget quantities measured on TRMM have coherent relationships to PC1 and PC2 on all timescales from simultaneous to long-term means. The relative importance of PC2 is greater on short temporal and small spatial scales. ""Top heavy"" ascent is associated with deep cloud systems, more intense precipitation, lower outgoing long-wave radiation, stronger cloud long-wave forcing, and extensive anvils. Cloud short-wave forcing depends primarily on PC1, while the net cloud forcing depends more on PC2. High-thin clouds are less correlated with short-term variations of the vertical velocity. Shallow precipitation measured by TRMM precipitation radar is associated with ""bottom heavy"" upward motion. Temporal compositing with respect to intense precipitating events shows that strong upward motions tend to develop in the lower atmosphere first and then change to the more ""top heavy"" type of upward motion. The associated cloud systems show consistent temporal changes in which high-thick clouds develop first and extensive anvil clouds develop later. These results suggest that the elevated latent heating from stratiform precipitation and the development of ""top heavy"" upward motion profiles in the tropics are related to each other. The coherent relationships shown here between large-scale vertical velocity and independently measured cloud and precipitation data can be used to test the performance of climate models. Copyright 2008 by the American Geophysical Union."
"9249239700;7003278104;9244954000;36097134700;6701431208;7101801476;7401580735;7003406400;7202772927;7201841931;","Comparisons of satellites liquid water esfimates to ECMWF and GMAO analyses, 20th century IPCC AR4 climate simulations, and GCM simulations",2008,"10.1029/2008GL035427","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57749187603&doi=10.1029%2f2008GL035427&partnerID=40&md5=762ba35520a9ef3c687a8a7eb029e851","To assess the fidelity of general circulation models (GCMs) in simulating cloud liquid water, liquid water path (LWP) retrievals from several satellites with passive sensors and the vertically-resolved liquid water content (LWC) from the CloudSat are used. Comparisons are made with ECMWF and MERRA analyses, GCM simulations utilized in the IPCC 4th Assessment, and three GCM simulations. There is considerable disagreement amongst the LWP estimates and amongst the modeled values. The LWP from GCMs are much larger than the observed estimates and the two analyses. The largest values in the CloudSat LWP occur over the boundary-layer stratocumulus regions; this feature is not as evident in the analyses or models. Better agreement is found between the two analyses and CloudSat LWP when cases with surface precipitation are excluded. The upward vertical extent of LWC from the GCMs and analyses is greater than CloudSat estimates. The issues of representing LWC and precipitation consistently between satellite-derived and model values are discussed. Copyright 2008 by the American Geophysical Union."
"6701689811;35577097300;25926681100;6508063123;16686078100;","Climate implications of large warming by elevated aerosol over India",2008,"10.1029/2008GL034944","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57749205583&doi=10.1029%2f2008GL034944&partnerID=40&md5=0a2e34f6562e7f0b97e0e405770db73e","Wide-ranging multi-platform data from a major field campaign conducted over Indian region was used to estimate the energy absorbed in ten layers of the atmosphere. We found that during pre-monsoon season, most of Indian region is characterized by elevated aerosol layers. Three-fold increase in aerosol extinction coefficient was observed at higher atmospheric layers (>2 km) compared to that near the surface and a substantial fraction (as much as 50 to 70%) of aerosol optical depth was found contributed by aerosols above (reflecting) clouds. Consequent absorption and hence strong warming above clouds was found larger by several degrees (K) compared to that near the surface. The aerosol-induced elevated warming was mostly confined below 2 km over northern Indian Ocean while found up to 4 km over central India, thus exhibiting strong meridional gradients (∼4 K) at atmospheric levels above 2 km. Climate implications of the large elevated warming are discussed. Copyright 2008 by the American Geophysical Union."
"7004932211;7004050581;36097134700;","Frequency of severe storms and global warming",2008,"10.1029/2008GL034562","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57749199285&doi=10.1029%2f2008GL034562&partnerID=40&md5=e6efa3b06920369a452f8f3059dd8ebc","We use five years of data from the Atmospheric Infrared Sounder (AIRS) to develop a correlation between the frequency of Deep Convective Clouds (DCC) and the zonal mean tropical surface temperature. AIRS data show that the frequency of DCC in the tropical oceans is very temperature sensitive, increasing 45% per 1 K increase of the zonal mean surface temperature. The combination of the sensitivity of the DCC frequency to temperature indicates that the frequency of DCC, and as a consequence the frequency of severe storms, increases at the rate of 6%/decade with the current +0.13 K/decade rate of global warming. This result is only qualitatively consistent with state-of-the-art climate models, where the frequency of the most intense rain events increases with global warming. Copyright 2008 by the American Geophysical Union."
"55113736500;","Effects of wind-powered hydrogen fuel cell vehicles on stratospheric ozone and global climate",2008,"10.1029/2008GL035102","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57749196709&doi=10.1029%2f2008GL035102&partnerID=40&md5=95ff3bba673a86446472a9701496d3d1","Converting the world's fossil-fuel onroad vehicles (FFOV) to hydrogen fuel cell vehicles (HFCV), where the H2 is produced by wind-powered electrolysis, is estimated to reduce global fossil, biofuel, and biomass-burning emissions of CO2 by ∼13.4%, NOx ∼23.0%, nonmethane organic gases ∼18.9%, black carbon ∼8% H2 ∼3.2% (at 3% leakage), and H2O ∼0.2%. Over 10 years, such reductions were calculated to reduce tropospheric CO ∼5%, NOx, ∼5-13%, most organic gases ∼3-15%, OH ∼4%, ozone ∼6%, and PAN ∼13%, but to increase tropospheric CH4 ∼0.25% due to the lower OH. Lower OH also increased upper tropospheric/lower stratospheric ozone, increasing its global column by ∼0.41%. WHFCV cooled the troposphere and warmed the stratosphere, reduced aerosol and cloud surface areas, and increased precipitation. Other renewable-powered HFCV or battery electric vehicles should have similar impacts. Copyright 2008 by the American Geophysical Union."
"7201858544;7004853382;8412168800;","Retrieval of snow surface microwave emissivity from the advanced microwave sounding unit",2008,"10.1029/2007JD009559","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68149092561&doi=10.1029%2f2007JD009559&partnerID=40&md5=6830143ff8707cae7197bf191e34b82e","Satellite data assimilation in numerical weather prediction systems requires information on microwave snow surface emissivity in a wide wavelength range. However, the existing models perform poorly for stratified snow or aged snow especially at high frequencies such that they are inapplicable for various snow types. The brightness temperatures at the window channels of the advanced microwave sounding unit (AMSU) are characterized strongly by surface emissivity and are thus used in this study to retrieve snow surface emissivity from 23.8 to 150 GHz under both clear and cloudy conditions. This algorithm uses an iteration scheme associated with a two-stream radiative transfer model. The accuracy of the AMSU-retrieved snow emissivity using this algorithm is first assessed against a set of satellite-observed emissivity under clear skies and a set of simulated emissivity under cloudy conditions. The algorithm is then assessed by its application to seven consecutive snow events observed at Hagerstown, Maryland, in February 2003 and to a set of mountainous snowpacks observed at the Local Scale Observation Site of the Cold Land Processes Field Experiment in northern Colorado in February and March of 2002 and 2003. Results show that the AMSU-retrieved snow emissivity spectra are consistent with the snow emissivity model simulations of the snow events in both Maryland and Colorado. Furthermore, the impact of the AMSU-retrieved snow emissivity on global satellite data assimilation systems is investigated by applying the algorithm to the National Centers for Environmental Prediction (NCEP) Gridpoint Statistical Interpolation (GSI) system. Compared to the existing analytic land emissivity model used in the GSI system, the retrieved emissivity significantly improves the use of the AMSU sounding data in the NCEP GSI system. Therefore, the AMSU-based snow emissivity retrieval algorithm has demonstrated its potential use in the global satellite data assimilation systems. Copyright 2008 by the American Geophysical Union."
"16639635900;7004647146;","Glacier changes and regional climate: A mass and energy balance approach",2008,"10.1175/2008JCLI2219.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349154992&doi=10.1175%2f2008JCLI2219.1&partnerID=40&md5=bfc1d68c9c6d567f075a299eb8636b74","The mass balance of a glacier is a complex consequence of the combination of atmospheric variables that control it. However, the understanding of past, present, and future glacier states is often predicated on very simplified representations of the mass balance-climate relationship. Here, a full surface energy and mass balance (SEMB) model is developed to explore the relationship between glacier equilibrium-line altitudes (ELAs) and climate at a regional scale. This model is applied to central Asia because of the diverse climate regimes and glacier history. The model captures the pattern in ELAs well; the seasonal cycle in energy balance terms are comparable to studies on individual glaciers in central Asia, and the proportionality factor relating melt to temperature is within the range of those reported for individual glaciers within the area. In regions where precipitation is low, ablation at the ELA is dominated by sublimation. Conversely, where precipitation is high, ablation at the ELA is dominated by melt and surface runoff. In turn, the sensitivity of the ELA to changes in climate is strongly tied to the dominant ablation process. In particular, ELAs in melt-dominated regions are most sensitive to interannual variability in air temperature, while ELAs in sublimation-dominated regions are most sensitive to interannual variability in precipitation. Glaciers in sublimation-dominated regions are acutely sensitive to even small changes in atmospheric variables. Finally, changes in clouds are shown to be important in all regions through their influence on the shortwave and longwave radiative fluxes, which dominate the surface energy balance at the ELA. © 2008 American Meteorological Society."
"7405527168;56370652400;","Size distributions of elemental carbon in the atmosphere of a coastal urban area in South China: Characteristics, evolution processes, and implications for the mixing state",2008,"10.5194/acp-8-5843-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-54049116729&doi=10.5194%2facp-8-5843-2008&partnerID=40&md5=0f3dd9d0804d4e5720ca4fabc725f9a9","Elemental carbon (EC), as one of the primary light-absorbing components in the atmosphere, has a significant impact on both regional and global climate. The environmental impacts of EC are strongly dependent on its particle size. Little is known about the size distribution characteristics of EC particles in China's ambient environments. We report size distributions of EC particles in the urban area of Shenzhen in Southern China. In our samples, EC was consistently found in two modes, a fine mode and a coarse mode. The majority of EC mass (∼80%) in this coastal metropolitan city resided in particles smaller than 3.2 μm in diameter. The fine mode peaked at around either 0.42 μm or 0.75 μm. While the mode at 0.42 μm could be ascribed to fresh vehicular emissions in the region, the mode at 0.75 μm was likely a result of particle growth from smaller EC particles. We theoretically investigated the particle growth processes that caused the EC particles to grow from 0.42 μm to 0.75 &amp;micro;m in the atmosphere. Our calculations indicate that the EC peak at 0.75 μm was not produced through either coagulation or H 2SO4 condensation; both processes are too slow to lead to significant EC growth. Hygroscopic growth was also determined to be insignificant. Instead, addition of sulfate through in-cloud processing was found to cause significant growth of the EC particles and to explain the EC peak at 0.75 μm. We also estimated the mixing state of EC from the EC size distributions. In the droplet size, at least 45ĝ€""60% of the EC mass in the summer samples and 68% of the EC mass in the winter samples was internally mixed with sulfate as a result of in-cloud processing. This information on EC should be considered in models of the optical properties of aerosols in this region. Our results also suggest that the in-cloud processing of primary EC particles could increase the light absorbing capacities through mixing EC with sulfate."
"8866821900;7201504886;7005808242;57218978147;7402435469;57212416832;7004479957;","Aquaplanets, climate sensitivity, and low clouds",2008,"10.1175/2008JCLI1995.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55849090814&doi=10.1175%2f2008JCLI1995.1&partnerID=40&md5=18f203667ddfd1a1411815c76a91d447","Cloud effects have repeatedly been pointed out as the leading source of uncertainty in projections of future climate, yet clouds remain poorly understood and simulated in climate models. Aquaplanets provide a simplified framework for comparing and understanding cloud effects, and how they are partitioned as a function of regime, in large-scale models. This work uses two climate models to demonstrate that aquaplanets can successfully predict a climate model's sensitivity to an idealized climate change. For both models, aquaplanet climate sensitivity is similar to that of the realistic configuration. Tropical low clouds appear to play a leading role in determining the sensitivity. Regions of large-scale subsidence, which cover much of the tropics, are most directly responsible for the differences between the models. Although cloud effects and climate sensitivity are similar for aquaplanets and realistic configurations, the aquaplanets lack persistent stratocumulus in the tropical atmosphere. This, and an additional analysis of the cloud response in the realistically configured simulations, suggests the representation of shallow (trade wind) cumulus convection, which is ubiquitous in the tropics, is largely responsible for differences in the simulated climate sensitivity of these two models. © 2008 American Meteorological Society."
"25649175400;6602831555;7004194999;7003403778;12804234100;","Contrails, natural clouds, and diurnal temperature range",2008,"10.1175/2008JCLI2255.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349096410&doi=10.1175%2f2008JCLI2255.1&partnerID=40&md5=172e7e17806bc86b020d988cdb0c7db6","The direct impact of aircraft condensation trails (contrails) on surface temperature in regions of high aircraft density has been a matter of recent debate in climate research. Based on data analysis for the 3-day aviation grounding period over the United States, following the terrorists' attack of 11 September 2001, a strong effect of contrails reducing the surface diurnal temperature range (DTR) has been suggested. Simulations with the global climate model ECHAM4 (including a contrail parameterization) and long-term time series of observation-based data are used for an independent cross check with longer data records, which allow statistically more reliable conclusions. The climate model underestimates the overall magnitude of the DTR compared to 40-yr ECMWF Re-Analysis (ERA-40) data and station data, but it captures most features of the DTR global distribution and the correlation between DTR and either cloud amount or cloud forcing. The diurnal cycle of contrail radiative impact is also qualitatively consistent with expectations, both at the surface and at the top of the atmosphere. Nevertheless, there is no DTR response to contrails in a simulation that inhibits a global radiative forcing considerably exceeding the upper limit of contrail radiative impact according to current assessments. Long-term trends of DTR, the level of natural DTR variability, and the specific effect of high clouds on DTR are also analyzed. In both ECHAM4 and ERA-40 data, the correlation of cloud coverage or cloud radiative forcing with the DTR is mainly apparent for low clouds. None of the results herein indicates a significant impact of contrails on reducing the DTR. Hence, it is concluded that the respective hypothesis as derived from the 3-day aviation-free period over the United States lacks the required statistical backing. © 2008 American Meteorological Society."
"7003582587;8882641700;7004479957;","Differences in the lower troposphere in two- and three-dimensional cloud-resolving model simulations of deep convection",2008,"10.1002/qj.315","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57349122930&doi=10.1002%2fqj.315&partnerID=40&md5=5ba3d605875a94187ddd848dba9e2e7f","This short note discusses key deficiencies in two-dimensional (2D) cloud-resolving model (CRM) simulations. Results differ significantly from three-dimensional (3D) simulations in the low-level humidity structure and associated fields. These differences are consistent across two different CRMs that differ substantially in their thermodynamic and microphysical formulations. Our analysis suggests than the near-surface humidity structure depends on moisture transport in clouds, and we suggest that differences in entrainment between 2D and 3D simulations lead to substantial differences in both cloud amount and moisture transport by the clouds at low levels. When compared with 3D, less entrainment in 2D reduces the likelihood that convective updraughts terminate and moisten the lower troposphere. The differences between the 2D and 3D are significant if the CRM is to be used as a reference for comparison against numerical weather prediction (NWP) or climate models. Copyright © 2008 Royal Meteorological Society, Crown Copyright 2008."
"57198616562;6701333444;56520921400;55738957800;19337612500;","Investigation of regional and seasonal variations in marine boundary layer cloud properties from MODIS observations",2008,"10.1175/2008JCLI1974.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349172219&doi=10.1175%2f2008JCLI1974.1&partnerID=40&md5=147238b7430612704b318530913cabd4","To aid in understanding the role that marine boundary layer (MBL) clouds play in climate and assist in improving their representations in general circulation models (GCMs), their long-term microphysical and macroscale characteristics are quantified using observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard the National Aeronautics and Space Administration's (NASA's) Terra satellite. Six years of MODIS pixel-level cloud products are used from oceanic study regions off the west coasts of California, Peru, the Canary Islands, Angola, and Australia where these cloud types are common. Characterizations are given for their organization (macroscale structure), the associated microphysical properties, and the seasonal dependencies of their variations for scales consistent with the size of a GCM grid box (300 km × 300 km). MBL mesoscale structure is quantified using effective cloud diameter CD, which is introduced here as a simplified measure of bulk cloud organization; it is straight-forward to compute and provides descriptive information beyond that offered by cloud fraction. The interrelationships of these characteristics are explored while considering the influences of the MBL state, such as the occurrence of drizzle. Several commonalities emerge for the five study regions. MBL clouds contain the best natural examples of plane-parallel clouds, but overcast clouds occur in only about 25% of the scenes, which emphasizes the importance of representing broken MBL cloud fields in climate models (that are subgrid scale). During the peak months of cloud occurrence, mesoscale organization (larger CD) increases such that the fractions of scenes characterized as ""overcast"" and ""clumped"" increase at the expense of the ""scattered"" scenes. Cloud liquid water path and visible optical depth usually trend strongly with CD, with the largest values occurring for scenes that are drizzling. However, considerable interregional differences exist in these trends, suggesting that different regression functionalities exist for each region. For peak versus off-peak months, the fraction of drizzling scenes (as a function of CD) are similar for California and Angola, which suggests that a single probability distribution function might be used for their drizzle occurrence in climate models. The patterns are strikingly opposite for Peru and Australia; thus, the contrasts among regions may offer a test bed for model simulations of MBL drizzle occurrence. © 2008 American Meteorological Society."
"7004714030;35509639400;","An assessment of the primary sources of spread of global warming estimates from coupled atmosphere-ocean models",2008,"10.1175/2008JCLI2239.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349157052&doi=10.1175%2f2008JCLI2239.1&partnerID=40&md5=ebe86bfc14aec19c2fab3be7fca91add","Climate feedback analysis constitutes a useful framework for comparing the global mean surface temperature responses to an external forcing predicted by general circulation models (GCMs). Nevertheless, the contributions of the different radiative feedbacks to global warming (in equilibrium or transient conditions) and their comparison with the contribution of other processes (e.g., the ocean heat uptake) have not been quantified explicitly. Here these contributions from the classical feedback analysis framework are defined and quantified for an ensemble of 12 third phase of the Coupled Model Intercomparison Project (CMIP3)/ Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) coupled atmosphere-ocean GCMs. In transient simulations, the multimodel mean contributions to global warming associated with the combined water vapor-lapse-rate feedback, cloud feedback, and ocean heat uptake are comparable. However, intermodel differences in cloud feedbacks constitute by far the most primary source of spread of both equilibrium and transient climate responses simulated by GCMs. The spread associated with intermodel differences in cloud feedbacks appears to be roughly 3 times larger than that associated either with the combined water vapor-lapse-rate feedback, the ocean heat uptake, or the radiative forcing. © 2008 American Meteorological Society."
"16027868800;6602911098;6701676517;","Application of a semi-spectral cloud water parameterization to cooling tower plumes simulations",2008,"10.1016/j.atmosres.2008.04.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50249175874&doi=10.1016%2fj.atmosres.2008.04.006&partnerID=40&md5=e9478e597cbd4b563b1a8616f22f2cfe","In order to simulate the plume produced by large natural draft cooling towers, a semi-spectral warm cloud parameterization has been implemented in an anelastic and non-hydrostatic 3D micro-scale meteorological code. The model results are compared to observations from a detailed field experiment carried out in 1980 at Bugey (location of an electrical nuclear power plant in the Rhône valley in East Central France) including airborne dynamical and microphysical measurements. Although we observe a slight overestimation of the liquid-water content, the results are satisfactory for all the 15 different cases simulated, which include different meteorological conditions ranging from low wind speed and convective conditions in clear sky to high wind and very cloudy. Such parameterization, which includes semi-spectral determination for droplet spectra, seems to be promising to describe plume interaction with atmosphere especially for aerosols and cloud droplets. © 2008 Elsevier B.V. All rights reserved."
"56224155200;35497573900;7203062717;7005808242;57204886915;","A moist benchmark calculation for atmospheric general circulation models",2008,"10.1175/2008JCLI1891.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649107443&doi=10.1175%2f2008JCLI1891.1&partnerID=40&md5=cacb5b66543c79f346847d3b5dca60a1","A benchmark calculation is designed to compare the climate and climate sensitivity of atmospheric general circulation models (AGCMs). The experimental setup basically follows that of the aquaplanet experiment (APE) proposed by Neale and Hoskins, but a simple mixed layer ocean is embedded to enable air-sea coupling and the prediction of surface temperature. In calculations with several AGCMs, this idealization produces very strong zonal-mean flow and exaggerated ITCZ strength, but the model simulations remain sufficiently realistic to justify the use of this framework in isolating key differences between models. Because surface temperatures are free to respond to model differences, the simulation of the cloud distribution, especially in the subtropics, affects many other aspects of the simulations. The analysis of the simulated tropical transients highlights the importance of convection inhibition and air-sea coupling as affected by the depth of the mixed layer. These preliminary comparisons demonstrate that this idealized benchmark provides a discriminating framework for understanding the implications of differing physics parameterization in AGCMs. © 2008 American Meteorological Society."
"6602703924;15835601800;22937012600;","Hydrometeorologic, pedologic and vegetation patterns along an elevational transect in the montane forest of the Bolivian Yungas",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-52649166684&partnerID=40&md5=909d1b2481113d9a3f82fbd677bb9e27","The ""Mountain Agenda"" of the World Summit on Sustainable Development 2002 emphasised the global relevance of montane cloud forests for important ecosystem services like water resources and biodiversity hot spots. Serious concern about the fate of tropical mountain forests has recently triggered intensified research on the ecological complexity of these forests. However, in Latin America research was focused on the Caribbean, Costa Rica and Ecuador (DFG Research Unit 816), whereas studies in the Andes of Peru and Bolivia were missing. In the framework of an interdisciplinary project aiming at understanding the relationships between vegetation and abiotic factors in the montane forest belts of the humid Yungas of Bolivia, hydrometeorologic observations and research on the altitudinal change of soils along an elevational gradient were carried out. Results suggest that the floristic change of vegetation belts and the differences in forest stature are influenced by complex interactions of climatic and pedologic variables along an elevational transect from 1,700 to 3,400 m a.s.l."
"7004052136;54406186700;","A fog climatology for Mexico",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-52649103889&partnerID=40&md5=b4939ee5985df3ba55dbd6f302faa5bc","Fog can be defined as a cloud in the vicinity of the earth's surface that affects visibility. It differs from a cloud only in that the base of fog is at the surface of the earth while clouds are further above. Fog plays an important role in the hydrological cycle, mainly in the transport of water from the atmosphere to the earth's surface through wet deposition and interception by trees and vegetation. It is considered also a natural hazard that causes low visibility (according to the international, meteorological definition, fog reduces visibility at the ground below 1 km) and is a particular danger for all varieties of air, land and water transportation. On the other hand, fog can be also considered a potential non-conventional source of water supply when removed by artificial methods for human consumption. Fogs of all types originate when the temperature and the dewpoint of the air coincide. This may occur through cooling of the air to a little beyond its dewpoint, as a result of advection, radiation or upslope movement of the air; or by adding moisture and thereby elevating the dewpoint, thus producing so-called frontal fogs. These synoptic and mesoscale mechanisms are modified by local terrain features, such as topography, land and vegetation cover and, in turn, small-scale circulation. Thus, varied climatic regimes result in different distribution patterns of fog occurrence and development. In spite of its importance, the impacts of fog formation, development and distribution have not yet been properly assessed throughout the world. In particular, in Mexico there are very few specific studies on the topic and there are none of national character known to these authors."
"13402651100;55524267300;7005030035;6602176524;13403304300;","Impact of initial condition uncertainties on the predictability of heavy rainfall in the Mediterranean: A case study",2008,"10.1002/qj.314","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57349186175&doi=10.1002%2fqj.314&partnerID=40&md5=07979876ffd29b7365cdcaba95cc7c49","This study explores the predictability of a heavy rainfall event that struck North Africa on 9 and 10 November 2001. This case is a paradigm of Mediterranean extreme events characterized by the presence of a deep upper-level trough associated with an intense cyclone which developed over the Western Mediterranean basin. Using the French non-hydrostatic mesoscale model MESO-NH, numerical experiments starting from various initial atmospheric states were conducted to assess the impact of initial condition uncertainties on the precipitation and cloud cover forecast. To generate a set of perturbed atmospheric states, a simple date-shifting initialization method was used. Two sets of simulations were run, using lateral boundaries and initial conditions derived from both the French operational global assimilation system Action de Recherche Petite Echelle Grande Echelle (ARPEGE) and the European Centre for Medium-Range Weather Forecasts (ECMWF) system. Initial perturbations applied to the upper-level trough propagated and intensified throughout the simulation, leading to some discrepancy in the forecast of the low-level cyclone. While it was found that the upper-level trough and the surface cyclone controlled the location of the overall precipitation pattern, the predictability of smaller-scale features such as localized heavy rainfall was directly related to specific mesoscale structures. The low-level jet associated with the surface cyclone and the location and the intensity of the surface-low both impact upon the triggering and the sustainment of the convective cells. In consequence, small-scale perturbations of these mesoscale features led to large errors in the precipitation forecast, especially in the Algiers area. Copyright © 2008 Royal Meteorological Society."
"57199438347;57211224269;8839231800;","The SST-forced predictability of the sub-seasonal mode over East Asia with an atmospheric general circulation model",2008,"10.1002/joc.1655","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57849132614&doi=10.1002%2fjoc.1655&partnerID=40&md5=57bc4305adc40f327efb70519a4bc6b5","The sea surface temperature (SST)-forced predictability in precipitation is investigated in terms of the seasonal mean modes (SMMs) for June-July (JJ) and the sub-seasonal mode (SSM) using the 24-year six-member ensembles simulation with an atmospheric general circulation model (AGCM). The SSM was defined as a 20-day window length by an extended empirical orthogonal function (EOF) over the East Asian monsoon region. For the JJ mean rainfall, the first EOF of the model ensemble is considered to be the forced SST mode, with being an El Niño Southern Oscillation (ENSO) related pattern from the regressed SST field. The first mode of model was well correlated with the second mode of the observation in the spatial and temporal variation. In the potential predictability, the analysis of variance (ANOVA) was used for the mean mode and the SSM. The potential predictability for the SMM is improved over the north pf the 30 °N. Compared with JJ mean mode, the SSM has more SST-forced variance and less internal variability. Copyright © 2008 Royal Meteorological Society."
"6507587039;7005035462;","Mitigating the impact of RADCAL beacon contamination on F15 SSM/I ocean retrievals",2008,"10.1029/2008GL034914","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57849128058&doi=10.1029%2f2008GL034914&partnerID=40&md5=ec38dd2b418115319f86741a2559afca","Data from six Special Sensor Microwave/Imagers (SSM/I) have been used to provide a 22-year climate data record of surface wind speed, columnar water vapor, columnar cloud water, and surface rain rate. On 14 August 2006, a radar calibration (RADCAL) beacon was activated on F15, one of the SSM/I. Interference from the beacon caused retrieval biases of roughly -30% for wind and rain and 40% for vapor and cloud. We have developed a simple correction for RADCAL interference, which brings the retrieval biases down to a few percent for cloud and rain, and less than 1% for wind and vapor. The corrected F15 data are of suitable quality for weather research purposes, but we discourage use of F15 retrievals after 14 August 2006 for climate research purposes at present because it appears that RADCAL beacon interference may not be stable in time, but may depend upon the thermal environment of F15. Copyright 2008 by the American Geophysical Union."
"8621420900;57210433660;6603957831;34168252100;","Stable isotope chronology and climate signal calibration in neotropical montane cloud forest trees",2008,"10.1029/2007JG000613","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69549126377&doi=10.1029%2f2007JG000613&partnerID=40&md5=e2b89772b290322916b31cdb7b663d9f","Tropical montane cloud forests are ecosystems intrinsically linked to a narrow range of geographic and meteorological conditions, making them potentially sensitive to small changes in precipitation or temperature. We investigate the potential application of stable isotope analysis to cloud forest dendroclimatology at Monteverde in Costa Rica in order to be able to extract both chronological and paleoclimate information from trees without annual growth rings. High-resolution δ18O measurements are used to identify regular cycles in wood of up to 9%, which are associated with seasonal changes in precipitation and moisture sources. The calculated annual growth rates derived from the isotope time series match those observed from long-term basal growth measurements. Interannual variability in the oxygen isotope ratio of lower forest trees is primarily related to interannual changes in wet season precipitation. Forward modeling independently supports our detection of both annual chronology and a climate signal. The confirmation of annual chronology and sensitivity to interannual climate anomalies suggests that tropical cloud forest dendroclimatology can be used to investigate local and regional hydroclimatic variability and change. Copyright 2008 by the American Geophysical Union."
"7006328089;","Hadley cell bias in climate models linked to extratropical eddy stress",2008,"10.1029/2008GL035084","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57849144809&doi=10.1029%2f2008GL035084&partnerID=40&md5=6fca54ac8eb0a5021f15067ac7d709c7","Recent theoretical and observational work shows that the Reynolds stresses due to large-scale extratropical eddies play a key role in determining Hadley cell strength. This implies that errors in the representation of extratropical eddies in climate models could force a bias in the tropical circulation. Here, this hypothesis is assessed using output from 17 coupled climate models, focusing on Northern Hemisphere winter. Inter-model variability in Hadley cell strength, tropical temperature and tropical humidity is found to be significantly correlated with inter-model differences in stationary eddy stress. Thus, a significant fraction of the tropical climate bias found in current climate models may be forced from the extratropics. Copyright 2008 by the American Geophysical Union."
"35221494300;6603315547;57203053317;7006211890;6602914876;","Orographic cirrus in the global climate model ECHAM5",2008,"10.1029/2007JD009605","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56549109537&doi=10.1029%2f2007JD009605&partnerID=40&md5=cfab0ba5ed90ee7d62fd14b4bfa32232","A comparison of satellite data with simulations from global circulation models shows that there is a lack of cirrus cloud amount in large-scale models above and in the lee of mountains. The formation of orographic.cirrus clouds due to gravity waves is usually not parameterized in large-scale models. To improve the simulation of such orographically excited cirrus clouds a coupling of the gravity wave dynamics and the cloud microphysics has been implemented in the climate model European Centre/Hamburg 5 (ECHAM5). As homogeneous freezing of solution droplets strongly depends on the vertical velocity, an increased vertical velocity due to gravity wave activity in the upper troposphere leads to the formation of cirrus clouds with higher ice crystal number densities. A comparison of the new parameterization with measurements shows a better agreement with observations. Copyright 2008 by the American Geophysical Union."
"36538539800;55496163500;7202048112;8922308700;","Impacts of regional climate change on biogenic emissions and air quality",2008,"10.1029/2008JD009965","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56549088143&doi=10.1029%2f2008JD009965&partnerID=40&md5=4fe39bfd7abc4ec86a3b2f93b5c94702","Regional air quality simulations are conducted at a horizontal grid resolution of 36 km for four summers (2001, 2002, 2051, and 2052) to examine the sensitivity of air quality to potential regional climate change in the United States. In response to the predicted warmer climate in 2051/2052, the emissions of isoprene and terpene increase by 20-92% and 20-56%, respectively, over most of the domain. Surface O<inf>3</inf> increases by up to 19-20%. Such increases are largely driven by changes in temperature, solar radiation, and cloud fraction over most of the domain. PM<inf>2.5</inf>, its compositions, and visibility exhibit an overall negative sensitivity (decrease by up to 40%), resulting from the competition of the negative temperature effect and positive emission/ temperature effects. While the response of dry deposition is governed by the negative sensitivity of surface resistances, that of wet deposition is either, positive or negative, depending on the relative dominancy of changes in PM<inf>2.5</inf> and precipitation. Overall the net climatic effect due to changes in climatic variables alone dominates changes in O<inf>3</inf>, PM<inf>2.5</inf>, and wet and total deposition, and the net biogenic emission effect due to changes in biogenic emissions alone as a result of climate change is important for isoprene, organic matter, visibility, and dry deposition over several regions. Models that do not include secondary organic aerosol formation from isoprene may underestimate by at least 20% of the responses of organic aerosols to future climate changes over many areas of the modeling domain. Both regional climate and air quality exhibit interannual variability, particularly in temperature, isoprene emissions, and PM<inf>2.5</inf> concentrations, indicating a need for long-term simulations to predict future air quality. Compared with results from global models, stronger regional climate change signals may cause projected local impacts of climate change that are stronger or even different in sign. Copyright 2008 by the American Geophysical Union."
"7402480218;7402934750;","A method for continuous estimation of clear-sky downwelling longwave radiative flux developed using ARM surface measurements",2008,"10.1029/2008JD009936","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56549124468&doi=10.1029%2f2008JD009936&partnerID=40&md5=015bfa3926738169fb42ad4b73b5de97","We present an improved self-adaptive methodology for the continuous estimation of downwelling clear-sky longwave (LW) radiative flux based on analysis of surface irradiance, air temperature, and humidity measurements that includes a term to account for near surface optically thin haze. Comparison between our estimations and clear-sky LW measurements for many years of data from the Atmospheric Radiation Measurement (ARM) Climate Research Facility's Southern Great Plains (SGP), Tropical Western Pacific (TWP), and North Slope of Alaska (NSA) sites show agreement at about the 4 W m-2 level, with 75%, 94%, and 68% of the data falling within that range for the SGP, TWP, and NSA sites, respectively. Although there is no exact means of determining the uncertainty associated with the clear-sky LW estimations, our analyses and comparison with detailed radiative transfer (RT) model calculations suggest our estimations on average are no worse than model calculations that require temporally and spatially averaged input information. Our technique exhibits a high degree of repeatability for the downwelling LW cloud effect, with agreement at about the 3 W m-2 level. Applying our technique and that of Long and Ackerman (2000) to 15 years of data from the ARM SGP site shows the maximum all-sky and clear-sky SW and LW occurs during summer, with the greatest year-to-year clear-sky SW variability occurring in fall. The downwelling LW cloud effect is fairly constant across the seasons, but the greatest SW cloud effect occurs in spring. The downwelling net cloud effect is dominated by the SW, with the largest effect occurring in spring (-64 W m-2) and the smallest occurring during winter (-21 W m-2). Copyright 2008 by the American Geophysical Union."
"24832504800;57204346059;6603568514;7405763496;","Comparison of four cloud schemes in simulating the seasonal mean field forced by the observed sea surface temperature",2008,"10.1175/2007MWR2179.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52149089620&doi=10.1175%2f2007MWR2179.1&partnerID=40&md5=4608024b95a4cbad0a06b15d2820cf0e","The impacts of four stratiform cloud parameterizations on seasonal mean fields are investigated using the global version of the Experimental Climate Prediction Center (ECPC) global-to-regional forecast system (G-RSM). The simulated fields are compared with the International Satellite Cloud Climatology Project (ISCCP) data for clouds, the Global Precipitation Climatology Project data for precipitation, the Earth Radiation Budget Experiment and the Surface Radiation Budget data for radiation, and the National Centers for Environmental Prediction (NCEP)-Department of Energy (DOE) Atmospheric Model Intercomparison Project (AMIP-II) Reanalysis (R-2) for temperature. Compared to observations, no stratiform cloud parameterization performed better in simulating all aspects of clouds, temperature, precipitation, and radiation fluxes. There are strong interactions between parameterized stratiform clouds and boundary layer clouds and convection, resulting in changes in low-level cloudiness and precipitation in the simulations. When the simulations are compared with ISCCP cloudiness and cloud water, and the NCEP/DOE R-2 relative humidity, the cloud amounts simulated by all four cloud schemes depend mostly on relative humidity with less dependency on the model's cloud water, while the observed cloud amount is more strongly dependent on cloud water than relative humidity, suggesting that cloud parameterizations and the simulation of cloud water require further improvement. © 2008 American Meteorological Society."
"23012437100;7402029007;7004563980;","Parameterized mesoscale forcing mechanisms for initiating numerically simulated isolated multicellular convection",2008,"10.1175/2007MWR2133.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52149099611&doi=10.1175%2f2007MWR2133.1&partnerID=40&md5=eb7c0200e147522b22650ece05226d91","Two methods designed to parameterize mesoscale ascent in a three-dimensional numerical cloud model via near-surface momentum and heat fluxes are presented and compared to the commonly used technique of an initial perturbation placed within the model initial condition. The flux techniques use a continuously reinforced thermal or convergent low-level wind field to produce upward vertical motion on the order of 10 cm s-1, by which deep, moist convection can be initiated. The sensitivity of the convective response to the type, strength, and size of the forcing is evaluated using numerical simulations of a conditionally unstable environment with weak unidirectional shear. Precipitation-free cloud processes are used to further simplify the model response to the forcing. The three methods tested produce an initial convective response, but only the momentum and heat flux methods are able to produce sustained deep convection that approximately resembles isolated multicellular convection. Cell regeneration periods, defined as the elapsed time between subsequent vertical velocity maxima passing through a constant level in the updraft region above the source, vary from 8 to 25 min, depending on the forcing type, magnitude, and geometry. © 2008 American Meteorological Society."
"8658853400;24831835000;7006148505;24831995200;","The influence of the El Niño-Southern Oscillation on cloud-to-ground lightning activity along the Gulf Coast. Part II: Monthly correlations",2008,"10.1175/2007MWR2228.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52149120490&doi=10.1175%2f2007MWR2228.1&partnerID=40&md5=af2c3c49e852482687771feca8cc8a3b","The El Niño-Southern Oscillation (ENSO) cycle is known to influence weather and climate along the Gulf Coast region, causing anomalously high precipitation during El Niño winters. This region is also known for having the highest lightning flash density in the United States. An 8-yr dataset (1995-2002) of cloud-to-ground (CG) lightning flashes was analyzed to determine if the ENSO cycle influences lighting activity along the Gulf Coast region. Simple Pearson's correlations were computed between concurrent monthly pairings of Niño-3.4 sea surface temperature (SST) and CG lightning flash deviation values from the study area. The correlation results are mapped and analyzed for links to meteorological features. Statistically significant correlation values greater than 0.8 were noted over large swaths of the study area during each winter month. The highest correlations were arranged in banded swaths and associated with regions of low flash densities during December and February. In January, areas of high correlation were spatially coincident with areas of enhanced flash density. Both the enhanced CG flash regions and high correlation values and patterns are indicative of a southerly shift in the midlatitude storm track known to occur during warm ENSO events. During the spring and summer, most of the region has weak correlation with ENSO except for August, which has a large area of negative correlations. These findings indicate that lightning increases during La Niña summers. Correlation patterns in late fall are similar to those of winter. The ENSO-lightning relationship has implications for hazard assessment and can be a useful tool for long-term seasonal planning. © 2008 American Meteorological Society."
"6701324864;7202162685;","Analytical solutions to the stochastic kinetic equation for liquid and ice particle size spectra. Part I: small-size fraction",2008,"10.1175/2007JAS2484.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52049108516&doi=10.1175%2f2007JAS2484.1&partnerID=40&md5=cabf62c2028906523e70b39938f974a2","The kinetic equation of stochastic condensation for cloud drop size spectra is extended to account for crystalline clouds and also to include the accretion-aggregation process. The size spectra are separated into small and large size fractions that correspond to cloud drops (ice) and rain (snow). In Part I of this two-part paper, analytical solutions are derived for the small-size fractions of the spectra that correspond to cloud drops and cloud ice particles that can be identified with cloud liquid water or cloud ice water content, and used in bulk microphysical schemes employed in cloud and climate models. Solutions for the small-size fraction have the form of generalized gamma distributions. Simple analytical expressions are found for parameters of the gamma distributions that are functions of quantities that are available in cloud and climate models: liquid or ice water content and its vertical gradient, mean particle radius or concentration, and supersaturation or vertical velocities. Equations for the gamma distribution parameters provide an explanation of the dependence of the observed spectra on atmospheric dynamics, cloud temperature, and cloud liquid water or ice water content. The results are illustrated with example calculations for a crystalline cloud. The analytical solutions and expressions for the parameters presented here can be used for parameterization of the small-size fraction size spectra in liquid and crystalline clouds and related quantities (e.g., optical properties, lidar, and radar reflectivities). © 2008 American Meteorological Society."
"6603021857;26643036500;","On the climate impact of surface roughness anomalies",2008,"10.1175/2007JAS2509.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52049118118&doi=10.1175%2f2007JAS2509.1&partnerID=40&md5=1aaedfd94157e58b8ed9cac17028a989","Large-scale deployment of wind power may alter climate through alteration of surface roughness. Previous research using GCMs has shown large-scale impacts of surface roughness perturbations but failed to elucidate the dynamic mechanisms that drove the observed responses in surface temperature. Using the NCAR Community Atmosphere Model in both its standard and aquaplanet forms, the authors have explored the impact of isolated surface roughness anomalies on the model climate. A consistent Rossby wave response in the mean winds to roughness anomalies across a range of model implementations is found. This response generates appreciable wind, temperature, and cloudiness anomalies. The interrelationship of these responses is discussed, and it is shown that the magnitude of the responses scales with the horizontal length scale of the roughened region, as well as with the magnitude of the roughness anomaly. These results are further elucidated through comparison with results of a series of shallow-water model experiments. © 2008 American Meteorological Society."
"24491749700;7203001286;7202262257;","Implementing the delta-four-stream approximation for solar radiation computations in an atmosphere general circulation model",2008,"10.1175/2007JAS2526.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48749083552&doi=10.1175%2f2007JAS2526.1&partnerID=40&md5=3e6dc47779b6afc6f4e110649a8ac33e","Proper quantification of the solar radiation budget and its transfer within the atmosphere is of utmost importance in climate modeling. The delta-four-stream (DFS) approximation has been demonstrated to offer a more accurate computational method of quantifying the budget than the simple two-stream approximations widely used in general circulation models (GCMs) for radiative-transfer computations. Based on this method, the relative improvement in the accuracy of solar flux computations is investigated in the simulations of the third-generation Canadian Climate Center atmosphere GCM. Relative to the computations of the DFS-modified radiation scheme, the GCM original-scheme whole-sky fluxes at the top of the atmosphere (TOA) show the largest underestimations at high latitudes of a winter hemisphere on the order of 4%-6% (monthly means), while the largest overestimations of the same order are found over equatorial regions. At the surface, even higher overestimations are found, exceeding 20% at subpolar regions of a winter hemisphere. Flux differences between original and DFS schemes are largest in the tropics and at high latitudes, where the monthly zonal means and their dispersions are within 5 W m-2 at the TOA and 10 W m-2 at the surface in whole sky, but differences may be as large as 20 and -40 W m-2. In clear sky, monthly zonal means and their dispersions remain within 2 W m-2, but may be as large as 25 and -12 W m-2. Such differences are found to be mostly determined by variations in cloud optical depth and solar zenith angle, and by aerosol loading in a clear sky. © 2008 American Meteorological Society."
"7401836526;7402887257;","Scaling laws and regime transitions of macroturbulence in dry atmospheres",2008,"10.1175/2007JAS2616.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52049099905&doi=10.1175%2f2007JAS2616.1&partnerID=40&md5=2a26629a6b29f006131be17d63f630ae","In simulations of a wide range of circulations with an idealized general circulation model, clear scaling laws of dry atmospheric macroturbulence emerge that are consistent with nonlinear eddy-eddy interactions being weak. The simulations span several decades of eddy energies and include Earth-like circulations and circulations with multiple jets and belts of surface westerlies in each hemisphere. In the simulations, the eddy available potential energy and the barotropic and baroclinic eddy kinetic energy scale linearly with each other, with the ratio of the baroclinic eddy kinetic energy to the barotropic eddy kinetic energy and eddy available potential energy decreasing with increasing planetary radius and rotation rate. Mean values of the meridional eddy flux of surface potential temperature and of the vertically integrated convergence of the meridional eddy flux of zonal momentum generally scale with functions of the eddy energies and the energy-containing eddy length scale, with a few exceptions in simulations with statiscally near-neutral or neutral extratropical thermal stratifications. Eddy energies scale with the mean available potentiall energy and with a function of the supercriticality, a measure of the near-surface slope of isentropes. Strongly baroclinic circulations form an extended regime in which eddy energies scale linearly with the mean available potential energy. Mean values of the eddy flux of surface potential temperature and of the vertically integrated eddy momentum flux convergence scale similarly with the mean available potential energy and other mean fields. The scaling laws for the dependence of eddy fields on mean fields exhibit a regime transition between a regime in which the extratropical thermal stratification and tropopause height are controlled by radiation and convection and a regime in which baroclinic entropy fluxes modify the extratropical thermal stratification and tropopause height. At the regime transition, for example, the dependence of the eddy flux of surface potential temperature and the dependence of the vertically integrated eddy momentum flux convergence on mean fields changes - a result with implications for climate stability and for the general circulation of an atmosphere, including its tropical Hadley circulation. © 2008 American Meteorological Society."
"24476800500;7005202019;7006783796;6506582181;","Experiments with cloud properties: Impact on surface radiative fluxes",2008,"10.1175/2007JTECHO546.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51749113326&doi=10.1175%2f2007JTECHO546.1&partnerID=40&md5=f8115b4ab82c64a6dea952e1c9a6b2ff","Solar radiation reaching the earth's surface provides the primary forcing of the climate system, and thus, information on this parameter is needed at a global scale. Several satellite-based estimates of surface radiative fluxes are available, but they differ from each other in many aspects. The focus of this study is to highlight one aspect of such differences, namely, the way satellite-observed radiances are used to derive information on cloud optical properties and the impact this has on derived parameters such as surface radiative fluxes. Frequently, satellite visible radiance in a single channel is used to infer cloud transmission; at times, several spectral channels are utilized to derive cloud optical properties and use these to infer cloud transmission. In this study, an evaluation of these two approaches will he performed in terms of impact on the accuracy in surface radiative fluxes. The University of Maryland Satellite Radiation Budget (UMD/SRB) model is used as a tool to perform such an evaluation over the central United States. The estimated shortwave fluxes are evaluated against ground observations at the Atmospheric Radiation Measurement Program (ARM) Central Facility and at four ARM extended sites. It is shown that the largest differences between these two approaches occur during the winter season when snow is on the ground. © 2008 American Meteorological Society."
"20435752700;35887706900;6602479559;","Humidity impact on the aerosol effect in warm cumulus clouds",2008,"10.1029/2008GL034178","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57049128783&doi=10.1029%2f2008GL034178&partnerID=40&md5=170aaa2cb79711bcacb59635d2ee94c7","The effects of aerosols on clouds are recognized as among the most important factors affecting climate change yet these effects are poorly understood due to the complexity of cloud processes and the strong influence of other environmental conditions. A numerical cloud model is used here to study the combined influence of aerosol concentration and upper level humidity conditions on moderate-sized, coastal, convective clouds. We show that these variables are strongly linked in their effects on clouds and suggest a microphysical variable space in which their influence can be distinguished. Copyright 2008 by the American Geophysical Union."
"7006614696;7401945370;25647939800;","A joint satellite and global cloud-resolving model analysis of a Madden-Julian Oscillation even: Model diagnosis",2008,"10.1029/2008JD009986","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349123871&doi=10.1029%2f2008JD009986&partnerID=40&md5=1f17d9435430664c145ccc3439f9d7c3","In this study, a methodology to diagnose a global cloud-resolving model (GCRM) is explored on the basis of a joint analysis with satellite measurements. The Madden-Julian Oscillation experiment carried out with the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) is used as the test bed. The NICAM output is compared with Tropical Rainfall Measuring Mission (TRMM) and CloudSat measurements in terms of composite analysis, contoured frequency by altitude diagrams (CFADs), and the joint histogram of cloud top and precipitation top heights. It is found in the composite diagram that the GCRM reproduces a slow, eastward migration of a convective envelope well comparable to the satellite measurement. The GCRM CFAD qualitatively reproduces TRMM and CloudSat CFADs, except that the GCRM tends to overly produce snow in deep convection. The joint histograms reveal that, while the overproduction of snow is evident, NICAM-simulated snow is incapable of producing 94-GHz radar echoes higher than 5 dBZ. This deficiency can be mitigated by a modification to microphysical parameterization in the way that a proportion of small particles is enhanced in the snow mass spectrum. Copyright 2008 by the American Geophysical Union."
"24758974300;6602598448;7003627515;56016103100;7003861526;7004426987;","Analysis of clear-sky Antarctic snow albedo using observations and radiative transfer modeling",2008,"10.1029/2007JD009653","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349114042&doi=10.1029%2f2007JD009653&partnerID=40&md5=f4be8dbb699a97ab332d56cd5f6c2185","A radiative transfer model for studying spectral and broadband snow surface albedo has been applied to radiation data (1998-2001) from different climate regimes in Antarctica. The model makes use of the doubling-adding method for radiative transfer, combined with the correlated κ-distribution technique to account for atmospheric gas absorption. Snow layers are described by scattering phase functions for irregular hexagonal plate-shaped ice crystals. Multiple scattering is included, as well as the option to include soot in the snowpack, as well as clouds. Sensitivity experiments show that the model is capable of calculating spectral and broadband albedos as a function of solar zenith angle and effective snow grain radius r<inf>e</inf>, The novel approach of applying the model to multiple-year field data of clear-sky albedo from five locations in Dronning Maud Land, Antarctica, reveals that seasonal clear-sky albedo variations (0.77-0.88) are dominantly caused by strong spatial and temporal variations in r<inf>e</inf> Summer season averages of r<inf>e</inf> range from 22 μm on the Antarctic plateau to 64 μm on the ice shelf. Maximum monthly values of r<inf>e</inf> are 40-150% higher. Other factors influencing clear-sky broadband albedo are the seasonal cycle in solar zenith angle (at most 0.02 difference in summer and spring/autumn albedo) and the spatial variation in optical thickness of the cloudless atmosphere (0.01 difference between ice shelves and plateau). The seasonal cycle in optical thickness of the atmosphere was found to be of minor importance (<0.005 between summer and spring/autumn). Copyright 2008 by the American Geophysical Union."
"55745955800;7004479957;","Mechanisms of low cloud-climate feedback in idealized single-column simulations with the Community Atmospheric Model, version 3 (CAM3)",2008,"10.1175/2008JCLI2237.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349145252&doi=10.1175%2f2008JCLI2237.1&partnerID=40&md5=7f48126372dea20925585865c5cf393d","This study investigates the physical mechanism of low cloud feedback in the Community Atmospheric Model, version 3 (CAM3) through idealized single-column model (SCM) experiments over the subtropical eastern oceans. Negative cloud feedback is simulated from stratus and stratocumulus that is consistent with previous diagnostics of cloud feedbacks in CAM3 and its predecessor versions. The feedback occurs through the interaction of a suite of parameterized processes rather than from any single process. It is caused by the larger amount of in-cloud liquid water in stratus clouds from convective sources, and longer lifetimes of these clouds in a warmer climate through their interaction with boundary layer turbulence. Thermodynamic effects are found to dominate the negative cloud feedback in the model. The dynamic effect of weaker subsidence in a warmer climate also contributes to the negative cloud feedback, but with about one-quarter of the magnitude of the thermodynamic effect, owing to increased low-level convection in a warmer climate. © 2008 American Meteorological Society."
"8643993200;6602974799;7003591311;7006117734;21740390400;8665917700;7005773698;7102422819;57203776263;","The influence of chemical composition and mixing state of Los Angeles urban aerosol on CCN number and cloud properties",2008,"10.5194/acp-8-5649-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53349099570&doi=10.5194%2facp-8-5649-2008&partnerID=40&md5=dda973360c6debe72260a03fb7a9aa89","The relationship between cloud condensation nuclei (CCN) number and the physical and chemical properties of the atmospheric aerosol distribution is explored for a polluted urban data set from the Study of Organic Aerosols at Riverside I (SOAR-1) campaign conducted at Riverside, California, USA during summer 2005. The mixing state and, to a lesser degree, the average chemical composition are shown to be important parameters in determining the activation properties of those particles around the critical activation diameters for atmospherically-realistic supersaturation values. Closure between predictions and measurements of CCN number at several supersaturations is attempted by modeling a number of aerosol chemical composition and mixing state cases of increasing complexity. It is shown that a realistic treatment of the state of mixing of the urban aerosol distribution is critical in order to eliminate model bias. Fresh emissions such as elemental carbon and small organic particles must be treated as non-activating and explicitly accounted for in the model. The relative number concentration of these particles compared to inorganics and oxygenated organic compounds of limited hygroscopicity plays an important role in determining the CCN number. Furthermore, expanding the different composition/mixing state cases to predictions of cloud droplet number concentration in a cloud parcel model highlights the dependence of cloud optical properties on the state of mixing and hygroscopic properties of the different aerosol modes, but shows that the relative differences between the different cases are reduced compared to those from the CCN model."
"13402835300;7003976079;7407104838;","Evaluation of the surface radiation budget in the atmospheric component of the Hadley Centre Global Environmental Model (HadGEM1)",2008,"10.1175/2008JCLI2097.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52949125461&doi=10.1175%2f2008JCLI2097.1&partnerID=40&md5=74f67ed64bc61e747b2d11048b64d510","The partitioning of the earth radiation budget (ERB) between its atmosphere and surface components is of crucial interest in climate studies as it has a significant role in the oceanic and atmospheric general circulation. An analysis of the present-day climate simulation of the surface radiation budget in the atmospheric component of the new Hadley Centre Global Environmental Model version 1 (HadGEM1) is presented, and the simulations are assessed by comparing the results with fluxes derived from satellite data from the International Satellite Cloud Climatology Project (ISCCP) and ground measurements from the Baseline Surface Radiation Network (BSRN). Comparisons against radiative fluxes from satellite and ground observations show that the model tends to overestimate the surface incoming solar radiation (Ss,d). The model simulates Ss,d very well over the polar regions. Consistency in the comparisons against BSRN and ISCCP-FD suggests that the ISCCP-FD database is a good test for the performance of the surface downwelling solar radiation in climate model simulations. Overall, the simulation of downward longwave radiation is closer to observations than its shortwave counterpart. The model underestimates the downward longwave radiation with respect to BSRN measurements by 6.0 W m-2. Comparisons of land surface albedo from the model and estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS) show that HadGEM1 overestimates the land surface albedo over deserts and over midlatitude landmasses in the Northern Hemisphere in January. Analysis of the seasonal cycle of the land surface albedo in different regions shows that the amplitude and phase of the seasonal cycle are not well represented in the model, although a more extensive validation needs to be carried out. Two decades of coupled model simulations of the twentieth-century climate are used to look into the model's simulation of global dimming/ brightening. The model results are in line with the conclusions of the studies that suggest that global dimming is far from being a uniform phenomenon across the globe."
"25226945400;56014511300;","Erroneous relationships among humidity and cloud forcing variables in three global climate models",2008,"10.1175/2008JCLI1969.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649107313&doi=10.1175%2f2008JCLI1969.1&partnerID=40&md5=5b79563aa6f2ccf0b5366913aa855c3f","Links are examined between time-averaged cloud radiative properties, particularly the longwave and shortwave components of cloud radiative forcing (CRF), and properties of the long-term averages of atmospheric soundings, in particular upper-tropospheric humidity (UTH), lower-tropospheric precipitable water (PW), and static stability (SS). The joint distributions of moisture measures and the composite or conditional mean CRF for different moisture and stability combinations are computed. This expands on previous studies that have examined cloud properties versus vertical velocity and surface temperature. These computations are done for satellite observations and for three representative coupled climate models from major modeling centers. Aside from mean biases reported previously, several departures are identified between the modeled and observed joint distributions that are qualitative and significant. Namely, the joint distribution of PW and UTH is very compact in observations but less so in models, cloud forcings are tightly related to PW in the data but to UTH in the models, and strong negative net CRF in marine stratocumulus regions occurs only for high SS and low UTH in the data but violates one or both of these restrictions in each of the models. All three errors are preliminarily interpreted as symptoms of inadequate dependence of model convective development on ambient humidity above the boundary layer. In any case, the character of the errors suggests utility for model testing and future development. A set of scalar metrics for quantifying some of the problems is presented; these metrics can be easily applied to standard model output. Finally, an examination of doubled-CO2 simulations suggests that the errors noted here are significantly affecting cloud feedback in at least some models. For example, in one model a strong negative feedback is found from clouds forming in model conditions that never occur in the observations. © 2008 American Meteorological Society."
"6701656335;7003904922;7201692406;7003396339;7004111620;","Variations in global cloud cover and the fair-weather vertical electric field",2008,"10.1016/j.jastp.2008.07.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51549113776&doi=10.1016%2fj.jastp.2008.07.001&partnerID=40&md5=0d8a0d7e084640fff5c273f4be5c7d1d","Statistically significant (at the 95% significance level) changes in daily cloud cover are found to occur globally over land coincident with extreme increases in 'fair-weather' measurements of vertical electric field (Ez) measured at Vostok, Antarctica. Using global cloud products from the International Satellite Cloud Climatology Project (ISCCP) D1 data series, superposed epoch analyses were made of both increases and decreases in Ez. Field significance testing revealed that, both before and after extreme increases in Ez, significant absolute cloud cover changes (of 13-15%) occur in the tropics and high latitudes. While the linkages in the tropics may reflect changes in the main convective cloud generators of current flow in the global circuit, the linkages at high latitudes appear to represent responses of clouds to the current flow. This linkage offers a possible explanation of a possible solar-terrestrial climate amplification mechanism. © 2008 Elsevier Ltd. All rights reserved."
"7004035832;","Measuring the carbon jungle",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-55349115400&partnerID=40&md5=c99ae882b47ea75153a90e04969c1d67","Yadvinder Malhi along with his researching team will have a project to study the effects of climate on tropical forests. This will cover 18km of forest from 200m above sea level and going deep into the Amazon rainforest as well as 3km up into the high Andes. The Peruvian students monitor numerous 100sq.m plots of forest while using the elevation gradient to know the function of tropical forest ecosystems under varying environmental conditions and its response on a warming climate. This Andean cloud forests as well as the Amazonian lowlands possesses 15% of all plant species which makes them the most biodiverse region on Earth. In addition, the botanist team discovered a few new species and even a new genus of tree but is quite sensitive to climate change."
"25226586000;25226859500;","Simulation of daily variation of suspended particulate matter over Delhi: Relative roles of vehicular emission, dust, and domestic appliances",2008,"10.1175/2008MWR2386.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649087843&doi=10.1175%2f2008MWR2386.1&partnerID=40&md5=50442b1ab16eba76b0dfa0108c88f679","The massive growth in the size and the population of cities over the past few decades has led to serious deterioration in the quality of air. One of the important constituents of airborne pollutants, which is a major health hazard, is suspended particulate matter (SPM). SPM is also an important source of cloud condensation nuclei; accurate simulations of SPM with sufficiently long lead thus have many applications, from issuing health advisories to forecasting fog. One of the biggest challenges in modeling air pollution in general and SPM in particular is to identify and mathematically represent the (location specific) sources and sinks. In this study the authors present a dynamical model for daily values of SPM over Delhi, India. The meteorological parameters are taken from the daily values from NCEP reanalysis. The validation is carried out against observations generated by the Central Pollution Control Board (CPCB) in India for the period 2000-05. Error statistics show that the model can capture a significant part of the observed variability of SPM. An evaluation of the relative contributions of various sources show that while vehicular pollution accounts for a large fraction of the SPM throughout the year, steep increases in the winter and the premonsoon periods are accounted for by fossil fuel burning and wind blown dust, respectively. Simulation with a doubling scenario for traffic congestion shows the effect to have strong seasonality. Such a model can be also interfaced with a seasonal forecast model or a climate model for enhanced scope of seasonal forecasts or for an investigation of the impact of SPM on regional climate change. © 2008 American Meteorological Society."
"7801425389;6602999062;16300591200;6603109490;","Risk assessment of atmospheric emissions using machine learning",2008,"10.5194/nhess-8-991-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52149105987&doi=10.5194%2fnhess-8-991-2008&partnerID=40&md5=b0eeddd7665d2540a6649c1031021a34","Supervised and unsupervised machine learning algorithms are used to perform statistical and logical analysis of several transport and dispersion model runs which simulate emissions from a fixed source under different atmospheric conditions. First, a clustering algorithm is used to automatically group the results of different transport and dispersion simulations according to specific cloud characteristics. Then, a symbolic classification algorithm is employed to find complex non-linear relationships between the meteorological input conditions and each cluster of clouds. The patterns discovered are provided in the form of probabilistic measures of contamination, thus suitable for result interpretation and dissemination. The learned patterns can be used for quick assessment of the areas at risk and of the fate of potentially hazardous contaminants released in the atmosphere."
"13105366200;","Rain height statistics for satellite communication in Malaysia",2008,"10.1016/j.jastp.2008.06.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51549116034&doi=10.1016%2fj.jastp.2008.06.005&partnerID=40&md5=cff9f7f420f18fb9995ad77114611f73","The calculation of fade margin required for 99.99% of the time availability of satellite link requires the knowledge of rain height. There is a shortage of results on rain height over Malaysian equatorial stations. The results on rain height in relation to 0 °C isotherm height (Hi) over four stations are presented. The variations of 0 °C isotherm heights for two monsoon seasons have been studied based on an analysis of radiosonde. The exceedence probability statistics of rain height are compared between the two seasons. © 2008 Elsevier Ltd. All rights reserved."
"8954866200;35561911800;","Ensemble, water isotope-enabled, coupled general circulation modeling insights into the 8.2 ka event",2008,"10.1029/2008PA001610","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65649128931&doi=10.1029%2f2008PA001610&partnerID=40&md5=3eef56e9c097e2d35d3679529caf88fb","Freshwater forcing has long been postulated as a catalyst for abrupt climate change because of its potential to interfere with thermohaline circulation (THC). The most recent example may have occurred about 8.2 ka ago with the sudden drainage of glacial lakes Agassiz and Ojibway into the Hudson Bay. We perform an ensemble of simulations for this freshwater release using the fully coupled atmosphere ocean general circulation model, Goddard Institute for Space Studies ModelE-R. In all cases, simulated effects include reduced ocean heat transport and enhanced atmospheric heat transport in the Atlantic, increased surface albedo (through greater low cloud and sea ice cover), and local cooling of up to 3°C. Our suite of ensemble experiments allows us to examine the importance of the initial ocean state, in particular the presence or absence of Labrador Sea Water, in controlling the magnitude and length of the climate response. Water isotope tracers included in this model provide an improved means for direct comparisons of the modeled tracer response to water isotope-based, climate proxy data. Comparison of model simulations to data implies that there was an abrupt approximate halving of Atlantic THC, hence providing strong support for the hypothesis that the 8.2 ka event was caused by an abrupt release of fresh water into the North Atlantic. Copyright 2008 by the American Geophysical Union."
"6603255804;7402706393;24605315200;","Modeling temporal variations in multipolarized radar scattering from intertidal coastal wetlands",2008,"10.1016/j.isprsjprs.2008.07.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51249114747&doi=10.1016%2fj.isprsjprs.2008.07.003&partnerID=40&md5=ccd3817a1af2c93827273ddc503b31f0","Coastal wetlands form critical ecosystems that are very sensitive to natural and anthropogenic environmental factors. These dynamic environments can exhibit both seasonal and year-to-year variability causing significant temporal variations in remotely sensed data. Understanding these variations is necessary if time series of remotely sensed data are to be used to monitor and manage coastal environments. Coastal areas can also experience persistent cloud cover, thereby making the use of microwave sensors, such as radar, potentially attractive for monitoring. Data acquired by polarimetric Synthetic Aperture Radar (SAR) and Laser Altimeter (LIDAR) sensors are analyzed to evaluate the response of a coastal marsh complex to climatic and tidal processes. The utility of L-band SAR data is investigated for detecting the presence of inundation and quantifying seasonal variations in plant phenology in several wetland environments. A coherent microwave scattering model is used to simulate radar backscatter from the marsh under different phenological and inundation conditions. Coastal marshes can exhibit scattering behavior that is different from other environments, such as forests and inland grasslands, for which scattering phenomena have been more thoroughly studied. Using a high-resolution Digital Elevation Model (DEM) derived from LIDAR data and ancillary measurements of climatic and tidal conditions, changes in the multi-polarization L-band SAR responses over a three-year period are related to specific scattering mechanisms in the marsh. Results indicate that variations in polarization preference of herbaceous marshes are often more pronounced than those observed over upland areas. Succulent halophytic plants in the high marsh respond strongly to inundation but only mildly to climatic factors, such as average daily temperature. Conversely, the response of non-succulent halophytic plants in the low marsh is strongly dependent on climate, which in turn affects their response to inundation. Results indicate that some knowledge of the vegetation phenology is required, along with scattering simulations, for meaningful interpretation of multi-temporal SAR data over coastal wetlands. © 2008 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS)."
"6602999057;56522444900;","Dry-season precipitation in tropical West Africa and its relation to forcing from the extratropics",2008,"10.1175/2008MWR2295.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649085419&doi=10.1175%2f2008MWR2295.1&partnerID=40&md5=8f05e6d2e1b4218c73b2cff72338fa86","Precipitation is a major socioeconomic factor in the Guineo-Soudanian zone of tropical West Africa with its distinct summer rainy season from May to October. Albeit rare, precipitation during the dry season can have substantial impacts on the local hydrology and human activities reaching from the rotting of harvests to improved grazing conditions. This study provides an observationally based synoptic and dynamical analysis of an abundant rainfall event during the dry season of 2003/04 that affected the countries of Nigeria, Benin, Togo, and Ghana. The results point to a forcing of the rainfalls from the extratropics, in the following ways: 1) Upper-level clouds and moisture to the east of a weak, quasi-stationary extratropical disturbance enhance the greenhouse effect over the Sahel and the adjacent Sahara, and thereby cause a net-column warm anomaly and falling surface pressure. 2) One day before the precipitation event, negative pressure tendencies are further enhanced through warm advection and subsidence associated with the penetration of a more intense upper-trough into Algeria. 3) The resulting northward shift and intensification of the weak wintertime heat low allows low-level moist southerlies from the Gulf of Guinea to penetrate into the Soudanian zone. 4) Finally, daytime heating of the land surface and convective dynamics initiate heavy rainfalls. Operational forecasts of this event were promising, pointing to a strong control by the comparatively well-predicted extratropical upper-level circulation. © 2008 American Meteorological Society."
"56284543100;26643250500;6602831555;7003535176;25031430500;","Contrail cirrus supporting areas in model and observations",2008,"10.1029/2008GL034056","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56449125015&doi=10.1029%2f2008GL034056&partnerID=40&md5=d2f9fa4d0db98cc915941c9b35e9c90b","Contrails form and persist dependent on the surrounding moisture, temperature and pressure fields and on fuel and aircraft specific variables. After formation, contrail persistence requires only supersaturation relative to ice. The fractional area in which contrails can form is called potential contrail coverage. We introduce a potential contrail cirrus coverage equivalent to the cloud free supersaturated area. This field, simulated by the ECHAM4 climate model, agrees fairly well with estimates of supersaturation frequency as inferred from aircraft and satellite measurements. In areas where the two potential coverages are different, especially at lower flight levels, potential contrail coverage is not a valid estimate of maximum attainable contrail cirrus coverage. We parameterize both potential coverages consistently with the ECHAM4 cloud cover parameterization. A comparison of the potential contrail coverage with an earlier estimate reveals substantial differences especially at upper height levels in the tropics. Copyright 2008 by the American Geophysical Union."
"56575686800;7201485519;","Dependency of global mean precipitation on surface temperature",2008,"10.1029/2008GL034838","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56449120333&doi=10.1029%2f2008GL034838&partnerID=40&md5=1cc2d3a5a89246229febdb53dce66b3a","We investigate the causes of temperature dependent changes in global precipitation in contemporary General Circulation Models (GCMs) subjected to a doubling of atmospheric CO2 concentration. By analyzing the energy budget of the troposphere, we find that changes are dominated by processes robustly simulated by GCMs. Importantly, shortwave cloud feedbacks, whose uncertainty is largely responsible for the wide range of GCM temperature climate sensitivities, are shown to have little effect. This is because these mainly arise from the scattering of shortwave radiation that has little impact on the tropospheric heating that controls precipitation. Hence, we expect that the range of simulated precipitation sensitivities to temperature will not change greatly in future GCMs, despite the recent suggestion that satellite observations indicate that GCM precipitation changes are significantly in error."
"12143654900;7005548544;","Observed variations in convective precipitation fraction and stratiform area with sea surface temperature",2008,"10.1029/2008JD010064","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56249132174&doi=10.1029%2f2008JD010064&partnerID=40&md5=72918756d3fa3b5cebfab39d0d2c2bfc","This paper focuses on the relation between local sea surface temperature (SST) and convective precipitation fraction and stratiform rainfall area from radar observations of precipitation, using data from the Kwajalein atoll ground-based radar as well as the precipitation radar on board the TRMM satellite. We find that the fraction of convective precipitation increases with SST at a rate of about 6 to 12%/K and the area of stratiform rainfall normalized by total precipitation decreases with SST at rates between -5 and -28%/K. These relations are observed to hold for different regions over the tropical oceans and also for different periods of time. Correlations are robust to outliers and to undersampled precipitation regions. Kwajalein results are relatively insensitive to the parameters in the stratiform-convective classification algorithm. Quantitative differences between the results obtained using the two different radars could be explained by the smoothing in the reflectivity of convective regions due to the relatively large pixel size of the TRMM precipitation radar compared to the size of the convective clouds. Although a dependence on temperature such as the one documented is consistent with an increase in the efficiency of convective precipitation (and therefore consistent with one of the mechanisms invoked to explain the original Iris effect observations) this is but one step in studying the possibility of a climate feedback. Further work is required to clarify the particular mechanism involved. Copyright 2008 by the American Geophysical Union."
"14019342100;7102643810;","Total lightning activity as an indicator of updraft characteristics",2008,"10.1029/2007JD009598","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56249126839&doi=10.1029%2f2007JD009598&partnerID=40&md5=dd0b5bcc2155281db45c9295917ee618","This study investigates the relationship of total lightning activity and updraft characteristics, such as updraft volume and maximum updraft speed, for a number of storms of different types occurring in the High Plains and in Northern Alabama. Ground-based Doppler and dual polarimetric radar observations were used to compute updraft characteristics. Also, ground-based total lightning data were available at both locations. Results show that time series of updraft volume in the charging zone (at temperatures colder than -5°C) with vertical velocities greater than either 5 or 10 m s-1 have clear relationships with total lightning activity (r = 0.93). Furthermore, these relationships between updraft volume and lightning activity for the storm types of the two climate regimes tend to converge when considering only the subfreezing layers of the clouds. Neither the maximum nor the mean updraft speed correlate as well with total lightning activity (r = <0.8) as updraft volume. Through expanded study designed to explore further regime variability (or lack thereof) of updraft volume-lightning flash rate relationships, better or refined parameterizations for the numerical forecasting of lightning and/or detection and prediction of storm intensity could be realized. Copyright 2008 by the American Geophysical Union."
"55742914900;7501627905;7005304841;7102913661;7006705919;","Distribution and direct radiative forcing of carbonaceous and sulfate aerosols in an interactive size-resolving aerosol-climate model",2008,"10.1029/2007JD009756","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56249127188&doi=10.1029%2f2007JD009756&partnerID=40&md5=92e95bb2ed5e844250f04ede48207d25","A multimode, two-moment aerosol model has been incorporated in the NCAR CAM3 to develop an interactive aerosol-climate model and to study the impact of anthropogenic aerosols on the global climate system. Currently, seven aerosol modes, namely three for external sulfate and one each for external black carbon (BC), external organic carbon (OC), sulfate/BC mixture (MBS; with BC core coated by sulfate shell), and sulfate/OC mixture (MOS; a uniform mixture of OC and sulfate) are included in the model. Both mass and number concentrations of each aerosol mode, as well as the mass of carbonaceous species in the mixed modes, are predicted by the model so that the chemical, physical, and radiative processes of various aerosols can be formulated depending on aerosol's size, chemical composition, and mixing state. Comparisons of modeled surface and vertical aerosol concentrations, as well as the optical depth of aerosols with available observations and previous model estimates, are in general agreement. However, some discrepancies do exist, likely caused by the coarse model resolution or the constant rates of anthropogenic emissions used to test the model. Comparing to the widely used mass-only method with prescribed geometric size of particles (one-moment scheme), the use of prognostic size distributions of aerosols based on a two-moment scheme in our model leads to a significant reduction in optical depth and thus the radiative forcing at the top of the atmosphere (TOA) of particularly external sulfate aerosols. The inclusion of two types of mixed aerosols alters the mass partitioning of carbonaceous and sulfate aerosol constituents: about 35.5%, 48.5%, and 32.2% of BC, OC, and sulfate mass, respectively, are found in the mixed aerosols. This also brings in competing effects in aerosol radiative forcing including a reduction in atmospheric abundance of BC and OC due to the shorter lifetime of internal mixtures (cooling), a mass loss of external sulfate to mixtures (warming), and an enhancement in atmospheric heating per BC mass due to the stronger absorption extinction of the MBS than external BC (warming). The combined result of including a prognostic size distribution and the mixed aerosols in the model is a much smaller total negative TOA forcing (-0.12 W m-2) of all carbonaceous and sulfate aerosol compounds compared to the cases using one-moment 2 scheme either excluding or including internal mixtures (-0.42 and -0.71 W m-2, respectively). In addition, the global mean all-sky TOA direct forcing of aerosols is significantly more positive than the clear-sky value due to the existence of low clouds beneath the absorbing (external BC and MBS) aerosol layer, particularly over a dark surface. An emission reduction of about 44% for BC and 38% of primary OC is found to effectively change the TOA radiative forcing of the entire aerosol family by -0.14 W m-2 for clear-sky and -0.29 W m-2 for all-sky. Copyright 2008 by the American Geophysical Union."
"56978385600;7410041005;7406683894;7003865921;7004678728;","A height resolved global view of dust aerosols from the first year CALIPSO lidar measurements",2008,"10.1029/2007JD009776","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56249142811&doi=10.1029%2f2007JD009776&partnerID=40&md5=d5dce9d895ef2e5a43b1068ac5c36459","Based on the first year of CALIPSO lidar measurements under cloud-free conditions, a height-resolved global distribution of dust aerosols is presented for the first time. Results indicate that spring is the most active dust season,, during which ∼20% and ∼12% of areas between 0 and 60°N are influenced by dust at least 10% and 50% of the time, respectively. In summer within 3-6 km, ∼8.3% of area between 0 and 60°N is impacted by dust at least 50% of the time. Strong seasonal cycles of dust layer vertical extent are observed in major source regions, which are similar to the seasonal variation of the thermally driven boundary layer depth. The arid and semiarid areas in North Africa and the Arabian Peninsula are the most persistent and prolific dust sources. African dust is transported across the Atlantic all yearlong with strong seasonal variation in the transport pathways mainly in the free troposphere in summer and at the low altitudes in winter. However, the trans-Atlantic dust is transported at the low altitudes is important for all seasons, especially transported further cross the ocean. The crossing Atlantic dusty zones are shifted southward from summer to winter, which is accompanied by a similar southward shift of dust-generating areas over North Africa. The Taklimakan and Gobi deserts are two major dust sources in East Asia with long-range transport mainly occurring in spring. The large horizontal and vertical coverage of dust aerosols indicate their importance in the climate system through both direct and indirect aerosol effects. Copyright 2008 by the American Geophysical Union."
"55262957100;7006165316;","Space-time variability of equatorial Kelvin waves and intraseasonal oscillations around the tropical tropopause",2008,"10.1029/2007JD009456","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56249097282&doi=10.1029%2f2007JD009456&partnerID=40&md5=cbf1e171259acb02886114e0aa970226","Using the ECMWT 40-year reanalysis data, large-scale variations of temperature and zonal wind around the tropical tropopause are investigated. From the space-time spectral analysis, two dominant spectral regions in the eastward propagating domain are found: one for Kelvin waves and the other for intraseasonal oscillations (ISOs). To investigate activities of Kelvin waves and ISOs we reconstructed the grid data for the two spectral windows and calculated the square amplitude at each grid point. Kelvin wave activities in zonal wind are vigorous during two seasons around February and July in the upper troposphere up to 100 hPa. However, the longitudinal maxima are found in the Eastern Hemisphere at 100 hPa and in the Western Hemisphere at 150 hPa and below. Activities calculated from the outgoing longwave radiation data for the Kelvin wave spectral window are different from those in zonal wind about their maximum longitudes and seasons. As the climatological background zonal wind in the upper troposphere is easterly in the Eastern Hemisphere and westerly in the Western Hemisphere, it seems that the difference of Kelvin wave activities between 100 hPa and 150 hPa is closely related to the background wind field affecting Kelvin wave propagation and dissipation. ISO activities in zonal wind at 100 hPa are vigorous in the western Pacific during northern winter, and we may find relation to those in OLR. This indicates that the eastward moving disturbance with the ISO time scale is coupled with the organized convective system such as the Madden-Julian oscillation. Copyright 2008 by the American Geophysical Union."
"6507305095;7203047936;7403326970;","Tests of an adjoint mesoscale model with explicit moist physics on the cloud scale",2008,"10.1175/2007MWR2259.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-49749118812&doi=10.1175%2f2007MWR2259.1&partnerID=40&md5=1e9b276c3ddcffea1174ec14f111c99a","An adjoint modeling system based upon the Naval Research Laboratory's Coupled Ocean-Atmosphere Mesoscale Prediction System's atmospheric component has been developed. The system includes the adjoint model of the explicit moist physics parameterization, which allows for gradients with respect to the initial hydrometeor concentrations to be calculated. This work focuses on the ability of the system to calculate evolved perturbations and gradients for the hydrometeor variables. Tests of the tangent linear and adjoint models for an idealized convective case at high model rcsolution (4-km horizontal grid spacing) are presented in this study. The tangent linear approximation is shown to be acceptable for all model variables (including the hydrometeors) with sizable perturbations for forecasts of 1 h. The adjoint model was utilized with the same convective case to demonstrate its applicability in four-dimensional variational data assimilation experiments. Identical twin experiments were conducted where the adjoint model produced gradients for all model variables, leading to improved analyses and forecasts. The best agreement between model forecasts and simulated observations occurred when information on all model variables was assimilated. In the case where only conventional data were assimilated, the agreement was not as good in the early forecast period. However, the hydrometeor values spun up quickly, and at later times, the forecast performed almost as well as when all data were assimilated. © 2008 American Meteorological Society."
"7004993886;7005634455;","Development and testing of polar weather research and forecasting (WRF) model. Part I: Greenland ice sheet meteorology",2008,"10.1175/2007MWR2112.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-49749102044&doi=10.1175%2f2007MWR2112.1&partnerID=40&md5=d25b674b8c138bbe2762a49096349127","A polar-optimized version of the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5) was developed to fill climate alid synoptic needs of the polar science community and to achieve an improved regional performance. to continue the goal of enhanced polar mesoscale modeling, polar optimization should now be applied toward the state-of-the-art Weather Research and Forecasting (WRF) Model. Evaluations and optimizations are especially needed for the boundary layer parameterization, cloud physics, snow surface physics, and sea ice treatment. Testing and development work for Polar WRF begins with simulations for ice sheet surface conditions using a Greenland-area domain with 24-km resolution. The winter month December 2002 and the summer month June 2001 are simulated with WRF, version 2.1.1, in a series of 48-h integrations initialized daily at 0000 UTC. The results motivated several improvements to Polar WRF, especially to the Noah land surface model (LSM) and the snowpack treatment. Different physics packages for WRF are evaluated with December 2002 simulations that show variable forecast skill when verified with the automatic weather mation observations. The WRF simulation with the combination of the modified Noah LSM, the Mellor-Yamada-Janjić boundary layer parameterization, and the WRF single-moment microphysics produced results that reach or exceed the success standards of a Polar MM5 simulation for December 2002. For summer simulations of June 2001, WRF simulates an improved surface energy balance, and shows forecast skill nearly equal to that of Polar MM5. © 2008 American Meteorological Society."
"57203378050;7404548584;55476786400;8408994300;","Strategy for studying nocturnal aerosol optical depth using artificial lights",2008,"10.1080/01431160802020528","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48249141407&doi=10.1080%2f01431160802020528&partnerID=40&md5=3288cfe22ee6cb53ff668ded5d7453cc","In this concept study, we develop a strategy for the monitoring of nighttime aerosol particle optical properties over land using artificial lights on the earth's surface. We demonstrate the possibility of detecting significant aerosol events and deriving variations in aerosol optical depth using the operational linescan system (OLS) on defence meteorological satellite program (DMSP) platforms. Since the OLS instruments have no on-board calibration, only a qualitative study of the potential to estimate aerosol and cloud properties using city lights at night is shown in this paper. The technique is demonstrated using China and India as test regions. With the launch of the visible/infrared imager/radiometer suite (VIIRS) instrument on the national polar-orbiting operational environmental satellite system (NPOESS) in the coming decade, fully quantitative retrieval of nighttime aerosol particle optical properties from space observations using such methods will become possible. Such work will benefit aerosol forecasting, safety of navigation, aerosol data assimilation and climate studies."
"6603925960;35509639400;7003865921;6507495053;7004714030;6701607011;","Use of CALIPSO lidar observations to evaluate the cloudiness simulated by a climate model",2008,"10.1029/2008GL034207","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53749095724&doi=10.1029%2f2008GL034207&partnerID=40&md5=73fe79a9596d3b0965e9bfe66e245b0c","New space-borne active sensors make it possible to observe the three-dimensional structure of clouds. Here we use CALIPSO lidar observations together with a lidar simulator to evaluate the cloudiness simulated by a climate model: modeled atmospheric profiles are converted to an ensemble of subgrid-scale attenuated backscatter lidar signals from which a cloud fraction is derived. Except in regions of persistent thick upper-level clouds, the cloud fraction diagnosed through this procedure is close to that actually predicted by the model. A fractional cloudiness is diagnosed consistently from CALIPSO data at a spatio-temporal resolution comparable to that of the model. The comparison of the model's cloudiness with CALIPSO data reveals discrepancies more pronounced than in previous model evaluations based on passive observations. This suggests that space-borne lidar observations constitute a powerful tool for the evaluation of clouds in large-scale models, including marine boundary-layer clouds. Copyright 2008 by the American Geophysical Union."
"36766103800;36852709800;16445036300;55762420600;36887358100;57196110485;","Long-term trends in sunshine duration over Yunnan-Guizhou Plateu in Southwest China for 1961-2005",2008,"10.1029/2008GL034482","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53749089276&doi=10.1029%2f2008GL034482&partnerID=40&md5=ef603885cb4e66dedb7b976bd51315e2","Yunnan-Guizhou Plateau (YGP), a low latitude highland region, covers the two provinces of Yunnan and Guizhou in Southwest China, where a cooling trend in the annual mean surface air temperature since the mid-20th century was reported as a notable phenomenon of regional climate against the global warming. In this study on the regional climate, we applied the data of sunshine duration and cloud amount from 184 stations across the YGP from year 1961 to 2005. It was found that, over this 45 year period, annual sunshine duration decreased mostly north of 24°N on the YGP with the negative trends reaching -11.8% per decade, while during the same period it increased with the positive trends reaching +3.5% per decade at the stations concentrated on the southwestern YGP. An overall decline in annual sunshine duration over the northern YGP dramatically accelerated from the 1970s to 80s with its maximum rate in the 1980s, but has remarkably decelerated since the 1990s so that going into the 21st century the annual sunshine duration has ceased or even reversed its downward tendency. The evolution of annual mean cloud amount on the YGP was shown to be insignificant and even in decline over the 45 years, exerting less of an influence on the decreasing trends in the annual sunshine duration. The consistent patterns of sunshine duration trends and surface temperature changes on the YGP support the hypothesis that aerosol loading in atmosphere could be involved in the surface cooling trend. Copyright 2008 by the American Geophysical Union."
"35494005000;7202652226;","The vertical structure of cloud occurrence and radiative forcing at the SGP ARM site as revealed by 8 years of continuous Data",2008,"10.1175/2007JCLI1987.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48749097295&doi=10.1175%2f2007JCLI1987.1&partnerID=40&md5=30d7f66d38b4f6ef04c42e1521798e84","Data collected at the Atmospheric Radiation Measurement (ARM) Program ground sites allow for the description of the atmospheric thermodynamic state, cloud occurrence, and cloud properties. This information allows for the derivation of estimates of the effects of clouds on the radiation budget of the surface and atmosphere. Herein 8 yr of continuous data collected at the ARM Southern Great Plains (SGP) Climate Research Facility (ACRF) are analyzed, and the influence of clouds on the radiative flux divergence of solar and infrared energy on annual, seasonal, and monthly time scales is documented. Given the uncertainties in derived cloud microphysical properties that result in calculated radiant flux errors, it is demonstrated that the ability to quantitatively resolve all but the largest heating and cooling influences by clouds is marginal for averaging periods less than 1 month. Concentrating on seasonal and monthly averages, it is found that the net column-integrated radiative effect of clouds on the atmosphere is nearly neutral at this middle-latitude location. However, a net heating of the upper troposphere by upper-tropospheric clouds and a cooling of the lower troposphere by boundary layer clouds is documented. The balance evolves over the course of an annual cycle as the troposphere deepens in summer and boundary layer clouds become less frequent relative to upper-tropospheric clouds. Although the top-of-atmosphere IR radiative effect is nearly invariant through the annual cycle, the seasonally varying heating profile is determined largely by the convergence of IR flux because solar heating is offset by IR cooling within the column. © 2008 American Meteorological Society."
"24337227400;7006755089;24339847400;7404448051;57210724003;","Slope, aspect and climate: Spatially explicit and implicit models of topographic microclimate in chalk grassland",2008,"10.1016/j.ecolmodel.2008.04.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45049087751&doi=10.1016%2fj.ecolmodel.2008.04.010&partnerID=40&md5=1c1c1fc89718576ff3c2e994fea1235b","The slope and aspect of a vegetated surface strongly affects the amount of solar radiation intercepted by that surface. Solar radiation is the dominant component of the surface energy balance and influences ecologically critical factors of microclimate, including near-surface temperatures, evaporative demand and soil moisture content. It also determines the exposure of vegetation to photosynthetically active and ultra-violet wavelengths. Spatial variation in slope and aspect is therefore a key determinant of vegetation pattern, species distribution and ecosystem processes in many environments. Slope and aspect angle may vary considerably over distances of a few metres, and fine-scale species' distribution patterns frequently follow these topographic patterns. The availability of suitable microclimate at such scales may be critical for the response of species distributions to climatic change at much larger spatial scales. However, quantifying the relevant microclimatic gradients is not straightforward, as the potential variation in solar radiation flux under clear-sky conditions is modified by local and regional variations in cloud cover, and interacts with long-wave radiation exchange, local meteorology and surface characteristics. We tested simple models of near-surface temperature and potential evapotranspiration driven by meteorological data with the incoming solar radiation flux adjusted for topography against measurements of temperature and soil moisture at two chalk grassland field sites in contrasting regional climates of the United Kingdom. We then estimated the cumulative distribution function of three key ecological variables (monthly temperature sums above 5 and 30 °C, plus potential evapotranspiration) across areas of complex topography at each site using two separate approaches: a spatially explicit and a spatially implicit method. The spatially explicit method uses digital elevation models of the sites to calculate the solar radiation at each grid cell and hence determines the spatial distribution of environmental variables. The second, less computationally intensive, method uses estimated statistical distributions of slope and aspect within the field sites to calculate the proportion of the surface area of each site predicted to exceed a given threshold of temperature sum or potential evapotranspiration. The spatially implicit model reproduces the range of the explicit model reasonably well but is limited by the parameterisation of slope and aspect, underlining the importance of variation in topography in determining the microclimatic conditions of a site. © 2008 Elsevier B.V. All rights reserved."
"7006182491;23990739600;7004296083;6603860503;23393907800;8336962200;6506611295;6602596149;35461255500;23990648900;23991053600;23991019000;23991356100;23991088600;26643041500;","Basic characteristics of atmospheric particles, trace gases and meteorology in a relatively clean Southern African Savannah environment",2008,"10.5194/acp-8-4823-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50049120399&doi=10.5194%2facp-8-4823-2008&partnerID=40&md5=48ec9a01f024e5bf15e479956bb4b81d","We have analyzed one year (July 2006g-July 2007) of measurement data from a relatively clean background site located in dry savannah in South Africa. The annual-median trace gas concentrations were equal to 0.7 ppb for SO2, 1.4 ppb for NOx, 36 ppb for O3 and 105 ppb for CO. The corresponding PM1, PM2.5 and PM10 concentrations were 9.0, 10.5 and 18.8 μg m-3, and the annual median total particle number concentration in the size range 10g-840 nm was 2340 cm-3. During Easterly winds, influence of industrial sources approximately 150 km away from the measurement site was clearly visible, especially in SO2 and NOx concentrations. Of gases, NOx and CO had a clear annual, and SO2, NOx and O3 clear diurnal cycle. Atmospheric new-particle formation was observed to take place in more than 90% of the analyzed days. The days with no new particle formation were cloudy or rainy days. The formation rate of 10 nm particles varied in the range of 0.1g-28 cm-3 s-1 (median 1.9 cm-3 s-1) and nucleation mode particle growth rates were in the range 3g-21 nm h-1 (median 8.5 nm h-1). Due to high formation and growth rates, observed new particle formation gives a significant contribute to the number of cloud condensation nuclei budget, having a potential to affect the regional climate forcing patterns."
"14421017500;7201696569;7401433183;23003667300;8434673400;","Dust aerosols: A possible accelerant for an increasingly arid climate in North China",2008,"10.1016/j.jaridenv.2008.02.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44649095042&doi=10.1016%2fj.jaridenv.2008.02.017&partnerID=40&md5=7e930df931551b3c3f7fa2a507214fb6","Results integrated from several data sources such as the vertical distribution characteristics of dust aerosols detected by aircraft, optical particle counter and Lidar measurements in the troposphere, dust devils, dry heat convection, and cloud parameter characteristics monitored by satellites, allow the identification of a new upwards dust transport mechanism. During non-dust storm periods, fine dust particles can be firstly carried into the atmosphere about 10-200 m by dust devils. Next, they can be carried to the height of the boundary layer at about 1000-6000 m by strong dry heat convection, so that a well-mixed dust layer dominates, which may even develop an elevated dust layer over the desert in the warm and sunny season. These processes lead to high dust aerosol concentrations in the desert troposphere, which results in an increase of condensation nuclei in clouds, a decrease of the effective radius of cloud droplets, and thus the formation of precipitation is suppressed. This paper develops a mechanism of positive feedback, which follows the following sequence: dust aerosol increases-effective radius of cloud droplet decreases-precipitation decreases-arid climate is strengthened. This new mechanism is a distinct factor in the development of an arid climate, especially desert in North China, and gradually becomes one of the most important factors maintaining an arid climate in North China. The positive feedback can accelerate desertification in this area. © 2008 Elsevier Ltd. All rights reserved."
"57190531316;6506679005;7005117153;","The impact of vertical resolution on regional model simulation of the west African summer monsoon",2008,"10.1002/joc.1636","https://www.scopus.com/inward/record.uri?eid=2-s2.0-49549093783&doi=10.1002%2fjoc.1636&partnerID=40&md5=b7febeed62bdfdf6d9af48d8776b9b8a","The RM3 regional climate model is used to simulate the west African summer monsoon for six June-September seasons using NCEP reanalysis data for lateral boundary forcing. The study compares the performance of the previously published 16-level version with a newly tested 28-level version, both running on a horizontal grid with 0.5° spacing, in order to determine what improvements in simulations are achieved by increased vertical resolution. Comparisons between the performances include diagnostics of seasonal mean precipitation rates and circulation, vertical profiles of cumulus heating rates, frequencies of shallow and deep convection and diagnostics related to transient African easterly waves (AEWs). The characteristics of a composite AEW simulated at both vertical resolutions are presented. Results show that the most significant impact of increasing the vertical resolution is stronger circulation, stronger vertical wind shear and higher amplitude AEWs. The simulations with higher vertical resolution also achieve higher peaks of cumulus latent heating rates. Spatial-temporal correlations between simulated daily 700 mb meridional winds versus corresponding NCEP reanalysis data and simulated daily precipitation versus estimates from the Tropical Rainfall Measurement Mission (TRMM) archive were equally high at both vertical resolutions. Copyright © 2007 Royal Meteorological Society."
"7202801743;24473932300;57202301596;7103393061;14032006000;7202973772;7004822209;7003821149;35829589800;","Air-sea interaction over ocean fronts and eddies",2008,"10.1016/j.dynatmoce.2008.01.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39049138051&doi=10.1016%2fj.dynatmoce.2008.01.001&partnerID=40&md5=1201afcfb685cd8e978ec4a27a5fefbc","Air-sea interaction at ocean fronts and eddies exhibits positive correlation between sea surface temperature (SST), wind speed, and heat fluxes out of the ocean, indicating that the ocean is forcing the atmosphere. This contrasts with larger scale climate modes where the negative correlations suggest that the atmosphere is driving the system. This paper examines the physical processes that lie behind the interaction of sharp SST gradients and the overlying marine atmospheric boundary layer and deeper atmosphere, using high resolution satellite data, field data and numerical models. The importance of different physical mechanisms of atmospheric response to SST gradients, such as the effect of surface stability variations on momentum transfer, pressure gradients, secondary circulations and cloud cover will be assessed. The atmospheric response is known to create small-scale wind stress curl and divergence anomalies, and a discussion of the feedback of these features onto the ocean will also be presented. These processes will be compared and contrasted for different regions such as the Equatorial Front in the Eastern Pacific, and oceanic fronts in mid-latitudes such as the Gulf Stream, Kuroshio, and Agulhas Return Current. © 2008 Elsevier B.V. All rights reserved."
"24340294600;57202721532;","Influence of atmospheric heat sources over the Tibetan Plateau and the tropical western North Pacific on the inter-decadal variations of the stratosphere-troposphere exchange of water vapor",2008,"10.1007/s11430-008-0082-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-47949094098&doi=10.1007%2fs11430-008-0082-8&partnerID=40&md5=0ac47068f709d2bebca625bce9ac140b","This study investigates the Stratosphere-Troposphere Exchange (STE) of water vapor, emphasizes its inter-decadal variations over Asia in boreal summer, and discusses the influences of atmospheric heat sources over the Tibetan Plateau and the tropical western North Pacific (WNP) on them by using the Wei method with reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) for the years of 1958 - 2001. The climatology shows that the upward transport of water vapor across the tropopause in boreal summer is the most robust over the joining area of the South Asian Peninsula and Indian-Pacific Oceans (defined as AIPO). The upward transport over there can persistently convey the abundant water vapor into the stratosphere and then influence the distribution and variation of the stratospheric water vapor. The analysis shows that inter-decadal variations of the water vapor exchange over the AIPO are significant, and its abrupt change occurred in the mid-1970s and the early 1990s. In these three periods, as important channels of the water vapor exchange, the effect of Bay of Bengal-East Asia as well as South China Sea was gradually weakening, while the role of the WNP becomes more and more important. Further studies show that atmospheric heat sources over the Tibetan Plateau and the WNP are two main factors in determining the inter-decadal variations of water vapor exchange. The thermal influences over the Tibetan Plateau and the WNP have been greatly adjusted over the pass 44 years. Their synthesis influences the inter-decadal variations of the water vapor exchange by changing the Asian summer monsoon, but their roles vary with time and regions. Especially after 1992, the influence of heat source over the Tibetan Plateau remarkably weakens, while the heat source over the WNP dominates the across-tropopause water vapor exchange. Results have important implications for understanding the transport of other components in the atmosphere and estimating the impact of human activities (emission) on global climate. © Science in China Press and Springer-Verlag GmbH 2008."
"7006031658;7003953689;23666201300;20734998800;24477308100;","Tertiary relict trees in a Mediterranean climate: Abiotic constraints on the persistence of Prunus lusitanica at the eroding edge of its range",2008,"10.1111/j.1365-2699.2008.01898.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-47949088237&doi=10.1111%2fj.1365-2699.2008.01898.x&partnerID=40&md5=b284c4e9775cd7426359dd980e861f15","Aim: To investigate the ecophysiological traits allowing persistence of a subtropical relict tree (Prunus lusitanica L.) under a dry Mediterranean climate at the eroding edge of its range. Location: A glasshouse for the study under controlled conditions and two marginal populations located in riparian forests of central Spain and exposed to summer drought, in contrast to subtropical populations that grow in mountain cloud forests. Methods: Two experiments were conducted to assess tolerance to the abiotic conditions found in riparian habitats. In a glasshouse experiment, gas-exchange and light-use parameters were measured to evaluate seedling responses to a factorial combination of irradiance (60%, 10%, 2% and 0.5% full sun) and moisture (well watered control and drought stress). In a parallel field experiment, irradiance and soil moisture were measured as predictors of seedling survival at two sites in which half the seedlings were subjected to a threefold increase in summer precipitation by adding water every 10 days. Results: Soil moisture strongly determined survival both in the glasshouse and in the two field sites. In the field, periodic addition of water failed to increase survival. Water-use efficiency (WUE) increased with drought. Seedlings did not tolerate deep shade (2-0.5%) and their performance and survival were better when exposed to moderate (10%) or high (60%) irradiance. The effect of water stress on seedling performance was stronger at moderate irradiance, moderate at high irradiance and negligible at very low light. Seedling size (height and number of leaves) attained after 1 month of experimental treatments had a positive effect on survival at the end of the summer, hence greater survival was not achieved at the expense of vertical growth. Main conclusions: While studies in Macaronesia have shown that P. lusitanica occupies a wide range of moisture conditions along mountain slopes, it behaves as an obligate riparian species in dry peripheral populations. Intolerance to deep shade and tolerance to moderate and high irradiance allow the species to grow in small and moist gaps, or in treeless river sections. Despite the species' low range filling in marginal, drought-prone regions, long-term persistence might have been achieved through shifts to riparian habitats serving as local refuges. © 2008 The Authors."
"7004369046;7407016988;","Diurnal cycle of surface flows during 2004 NAME and comparison to model reanalysis",2008,"10.1175/2008JCLI2206.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649096079&doi=10.1175%2f2008JCLI2206.1&partnerID=40&md5=d1703d490b54a1203919984401b187ea","During the North American Monsoon Experiment (NAME), an unprecedented surface dataset was collected over the core monsoon region. Observations from 157 surface sites in this region along with twice-daily Quick Scatterometer (QuikSCAT) oceanic winds were quality, controlled and processed into a gridded dataset covering the domain (15°-40°N, 90°-120°W) at 1-h, 0.25° resolution for the period from 1 July to 15 August. Using this dataset, the mean, temporal variability, and diurnal characteristics of the monsoon surface flow are documented with detail not previously possible. Being independent of model data over land, these objectively analyzed surface products are compared to similar analyses from a special North American Regional Reanlysis for NAME (NARR_NAME) that was produced for the same period. Observed surface fields indicate that a robust land-sea breeze circulation is present over most of the Gulf of California (GoC) region in response to the strong diurnal heating of landmasses on both sides of the gulf. Many details of this land-sea breeze circulation are either missing (e.g., the nighttime/early morning land breeze) or poorly represented in the NARR_NAME. Observations from high elevation sites in the Sierra Madre Occidental (SMO) show weak downslope flows (∼0.5 m s-1), near-saturated conditions, and low cloud bases during nighttime hours. These observations are consistent with the notion that high-terrain nocturnal clouds limit radiational cooling and, thus, nocturnal downslope flows as well. Over land, a cool and dry bias is observed in the NARR_NAME surface fields. This dry bias appears to limit the formation of nighttime cloudiness at high elevations, resulting in stronger radiational cooling at night and slope flows in the NARR_NAME that are 2-3 times stronger than observed. In addition, the daytime transition to surface convergence and rising motion over the western slopes of the SMO occurs about 3 h earlier in the NARR_NAME than observed, which indicates the tendency in the reanalyses to initiate the daily convective cycle too early, similar to that observed in operational forecast models over this region. Following significant rainfall events, increased soil moisture and evapotranspiration due to vegetative green-up result in a smaller diurnal temperature signal over land and weaker slope flowsover the SMO. In response to this weaker heating cycle, the magnitude and offshore extent of the land-sea breeze circulation is observed to diminish as the monsoon progresses. © 2008 American Meteorological Society."
"13402933200;","Modelling of the coupled chemistry-climate system: Projections of stratospheric ozone in the 21st century and impact of shipping on atmospheric composition and climate",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-47549089947&partnerID=40&md5=480f9fab8423edd601c114ab8d2b3d46","A complete understanding of atmospheric composition changes requires the consideration of climate change and its feedback on chemistry. Chemistry-climate models (CCMs) consider those feedbacks and are used in this work in combination with atmospheric observations in two related areas. The first area is stratospheric research, with the main goal to provide reliable projections of future changes in the stratosphere and their impacts on climate through a multi-model approach. The CCMs simulate the observed ozone reduction in the early nineties and predict a global ozone recovery between 2035 and 2050. The second research area is to study how gaseous and particulate emissions from international shipping impact on atmospheric composition und climate. The studies show a high impact of ship emissions on maritime clouds and radiative forcing. In addition, ship emissions cause air quality problems in coastal areas and harbours with heavy traffic."
"8708685100;57203053317;6602890253;7404062492;6602890253;6506058385;6701762451;","Single particle laser mass spectrometry applied to differential ice nucleation experiments at the aida chamber",2008,"10.1080/02786820802339538","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012524007&doi=10.1080%2f02786820802339538&partnerID=40&md5=deee8e6e61b6f7119401034df59c068a","Experiments conducted at the Aerosol Interactions and Dynamics in the Atmosphere (AIDA) chamber located in Karlsruhe, Germany permit investigation of particle properties that affect the nucleation of ice at temperature and water vapor conditions relevant to cloud microphysics and climate issues. Ice clouds were generated by heterogeneous nucleation of Arizona test dust (ATD), illite, and hematite and homogeneous nucleation of sulfuric acid. Ice crystals formed in the chamber were inertially separated from unactivated, or “interstitial” aerosol particles with a pumped counterflow virtual impactor (PCVI), then evaporated. The ice residue (i.e., the aerosol which initiated ice nucleation plus any material which was scavenged from the gas- and/or particle-phase), was chemically characterized at the single particle level using a laser ionization mass spectrometer. In this manner the species that first nucleated ice could be identified out of a mixed aerosol population in the chamber. Bare mineral dust particles were more effective ice nuclei (IN) than similar particles with a coating. Metallic particles from contamination in the chamber initiated ice nucleation before other species but there were few enough that they did not compromise the experiments. Nitrate, sulfate, and organics were often detected on particles and ice residue, evidently from scavenging of trace gas-phase species in the chamber. Hematite was a more effective ice nucleus than illite. Ice residue was frequently larger than unactivated test aerosol due to the formation of aggregates due to scavenging, condensation of contaminant gases, and the predominance of larger aerosol in nucleation. © 2008 Taylor & Francis Group, LLC."
"35887706900;6603081424;7003591311;7004174939;20435752700;","How small is a small cloud?",2008,"10.5194/acp-8-3855-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-47849087461&doi=10.5194%2facp-8-3855-2008&partnerID=40&md5=62c83ffa5451c936cada548d909a6a64","The interplay between clouds and aerosols and their contribution to the radiation budget is one of the largest uncertainties of climate change. Most work to date has separated cloudy and cloud-free areas in order to evaluate the individual radiative forcing of aerosols, clouds, and aerosol effects on clouds. Here we examine the size distribution and the optical properties of small, sparse cumulus clouds and the associated optical properties of what is considered a cloud-free atmosphere within the cloud field. We show that any separation between clouds and cloud free atmosphere will incur errors in the calculated radiative forcing. The nature of small cumulus cloud size distributions suggests that at any resolution, a significant fraction of the clouds are missed, and their optical properties are relegated to the apparent cloud-free optical properties. At the same time, the cloudy portion incorporates significant contribution from non-cloudy pixels. We show that the largest contribution to the total cloud reflectance comes from the smallest clouds and that the spatial resolution changes the apparent energy flux of a broken cloudy scene. When changing the resolution from 30 m to 1 km (Landsat to MODIS) the average ""cloud-free"" reflectance at 1.65 μm increases from 0.0095 to 0.0115 (&amp;gt;20%), the cloud reflectance decreases from 0.13 to 0.066 (∼50%), and the cloud coverage doubles, resulting in an important impact on climate forcing estimations. The apparent aerosol forcing is on the order of 0.5 to 1 Wm-2 per cloud field."
"7006643234;57189585133;24722339600;7006307463;7407116104;7406683894;7202016984;","Quantifying above-cloud aerosol using spaceborne lidar for improved understanding of cloudy-sky direct climate forcing",2008,"10.1029/2007JD009433","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50849143821&doi=10.1029%2f2007JD009433&partnerID=40&md5=253775c8e47c6254371f1a3372485e5a","Estimates of global mean direct climate forcing by absorbing aerosols located above boundary layer clouds are large, uncertain, and almost entirely unconstrained by observations. Spaceborne lidar offers a new opportunity for global constraints. Here we examine techniques for using liquid water clouds as lidar targets, allowing aerosol optical depth and Ångström exponent to be deduced directly from aerosol effects on light transmission. Two such techniques are examined using data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). The first is a previously reported method based on measurements of cloud depolarization ratio (DR) at 532-nm wavelength. The second is a new method using measurements of cloud color ratio (CR), which is the ratio of the signal from the cloud at 1064 nm to that at 532 nm. Optical depth retrievals from these two methods compare favorably over the eastern tropical Atlantic Ocean during August 2006, when biomass burning aerosols are frequently advected over marine stratiform clouds. The CR technique is mainly sensitive to fine-mode aerosols and essentially insensitive to clouds and coarse-mode dust. Because anthropogenic aerosol is predominantly found in the fine mode, the CR technique can be used to help identify situations where anthropogenic cloudy-sky direct radiative forcing is occurring. We demonstrate this capability using 6 months data over the eastern tropical Atlantic Ocean. Copyright 2008 by the American Geophysical Union."
"55017656900;7003591311;7101846027;35264611800;7004885872;7006572336;57196499374;","Statistical comparison of properties of simulated and observed cumulus clouds in the vicinity of Houston during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS)",2008,"10.1029/2007JD009304","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50849142581&doi=10.1029%2f2007JD009304&partnerID=40&md5=7209a6724e9677fb1e579b848bab79cc","We present statistical comparisons of properties of clouds generated by Large Eddy Simulations (LES) with aircraft observations of nonprecipitating, warm cumulus clouds made in the vicinity of Houston, TX during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS), carried out in the summer of 2006. Aircraft data were sampled with the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter airplane. Five flights (days) that are most suitable for studying aerosol-cloud interactions are selected from the 22 flights. The model simulations are initiated with observed environmental profiles. The simulations are used to generate an ensemble of thousands of cumulus clouds for statistically meaningful evaluations. Statistical comparisons focus on the properties of a set of dynamical and thermodynamical variables, sampled either in the cloud or the cloud updraft core. The set of variables includes cloud liquid water content (LWC), number mixing ratio of cloud droplets (N<inf>d</inf>), cloud effective radius (r<inf>e</inf>), updraft velocity (w), and the distribution of cloud sizes. In general, good agreement between the simulated and observed clouds is achieved in the normalized frequency distribution functions, the profiles averaged over the cloudy regions, the cross-cloud averages, and the cloud size distributions, despite big differences in sample size between the model output and the aircraft data. Some unresolved differences in frequency distributions of w and possible differences in cloud fraction are noted. These comparisons suggest that the LES is able to successfully generate the cumulus cloud populations that were present during GoMACCS. The extent to which this is true will depend on the specific application. Copyright 2008 by the American Geophysical Union."
"16639418500;57203053317;","Influence of Giant CCN on warm rain processes in the ECHAM5 GCM",2008,"10.5194/acp-8-3769-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-47549102019&doi=10.5194%2facp-8-3769-2008&partnerID=40&md5=5d76f77b279900265ca561583de19c8c","Increased Cloud Condensation Nuclei (CCN) load due to anthropogenic activity might lead to non-precipitating clouds because the cloud drops become smaller (for a constant liquid water content) and, therefore, less efficient in rain formation (aerosol indirect effect). Adding giant CCN (GCCN) into such a cloud can initiate precipitation (namely, drizzle) and, therefore, might counteract the aerosol indirect effect. The effect of GCCN on global climate on warm clouds and precipitation within the ECHAM5 General Circulation Model (GCM) is investigated. Therefore, the newly introduced prognostic rain scheme (Posselt and Lohmann, 2007) is applied so that GCCN are directly activated into rain drops. The ECHAM5 simulations with incorporated GCCN show that precipitation is affected only locally. On the global scale, the precipitation amount does not change. Cloud properties like total water (liquid + rain water) and cloud drop number show a larger sensitivity to GCCN. Depending on the amount of added GCCN, the reduction of total water and cloud drops account for up to 20% compared to the control run without GCCN. Thus, the incorporation of the GCCN accelerate the hydrological cycle so that clouds precipitate faster (but not more) and less condensed water is accumulated in the atmosphere. An estimate of the anthropogenic aerosol indirect effect on the climate is obtained by comparing simulations for present-day and pre-industrial climate. The introduction of the prognostic rain scheme lowered the anthropogenic aerosol indirect effect significantly compared to the standard ECHAM5 with the diagnostic rain scheme. The incorporation of the GCCN changes the model state, especially the cloud properties like TWP and Nl. The precipitation changes only locally but globally the precipitation is unaffected because it has to equal the global mean evaporation rate. Changing the cloud properties leads to a local reduction of the aerosol indirect effect and, hence, partly compensating for the increased anthropogenic CCN concentrations in that regions. Globally, the aerosol indirect effect is nearly the same for all simulations."
"7003627515;7006743561;25031484700;24758974300;","Surface radiation balance in the ablation zone of the west Greenland ice sheet",2008,"10.1029/2007JD009283","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50849097874&doi=10.1029%2f2007JD009283&partnerID=40&md5=b4f2a9db9a782bbf99bf3d3652044523","We present 4 years of radiation observations and derived cloud properties from the ablation zone of the west Greenland ice sheet (67°N). Data were collected using three automatic weather stations located at 6, 38, and 88 km from the ice sheet margin at elevations of 490, 1020, and 1520 m asl. This part of Greenland is characterized by a ∼150 km wide tundra, a ∼100 km wide ablation zone and an average equilibrium line altitude of ∼1500 in asl. At the lowest station, snow is redistributed by the wind in crevasses and gullies, leading to very little measured winter accumulation. As a result, glacier ice (albedo ≈ 0.55) is at the surface throughout the melting season. At 1020 m asl, the winter snow cover typically disappears in mid to end June. At 1520 m asl, superimposed ice briefly reaches the surface at the end of the ablation season. The combined effect of decreasing surface albedo and increasing cloud optical thickness as summer progresses causes absorbed shortwave radiation to peak in June at low elevations but progressively later at higher elevations. Incoming longwave radiation peaks in August, in response to increased cloud optical thickness and heating of the atmosphere over the snow and ice-free surroundings. The ice sheet margin experiences continuous melting in June, July, and August. This limits the emission of longwave radiation, causing net longwave radiation to peak in August, further enhancing melt. The sum of these effects is that summer net radiation increases sharply toward the ice sheet margin. To resolve this correctly requires high-resolution climate models, in the order of 10 km or better. Copyright 2008 by the American Geophysical Union."
"7102018821;25227357000;7005528388;7004242319;","On the correlation between ice water content and ice crystal size and its application to radiative transfer and general circulation models",2008,"10.1029/2008GL033918","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53749083037&doi=10.1029%2f2008GL033918&partnerID=40&md5=9035c0e0b194282fd4ee33268635ec8d","We performed correlation analysis involving ice water content (IWC) and mean effective ice crystal size (De) intended for application to climate models. For this purpose, ice crystal size distributions obtained from in situ measurements conducted from numerous field campaigns in the tropics, midlatitude, and Arctic regions were used and we show that IWC and De are well-correlated in this regional division. Including temperature classification in midlatitude cases increases this correlation. We applied the correlation results to cloud radiative forcing calculations in terms of IWC, in which De is expressed as a baseline mean and deviation from uncertainty in small ice crystal measurements. The latter deviates from the mean by less than 2 W/m2 in net radiative forcing. Using the correlation results, simulations from the UCLA GCM showed substantial regional deviations in OLR and precipitation patterns from assuming a constant De. Copyright 2008 by the American Geophysical Union."
"55713905400;57200702127;56100900500;56145499000;7404865816;","Increased winter precipitation over the North Pacific from 1984-1994 to 1995-2005 inferred from the Global Precipitation Climatology Project",2008,"10.1029/2008GL034668","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53749093112&doi=10.1029%2f2008GL034668&partnerID=40&md5=d79e5dcaa9f18ab557f72b7063af6a5d","An analysis of the results from the Global Precipitation Climatology Project (GPCP) reveals a trend of increased wintertime precipitation over the North Pacific from 1984 to 2005. The precipitation over the North Pacific increases by about 1.5 mm/year in winter during the period of 1984 to 2005. Statistic analyses are performed to validate the observed precipitation trend, showing the f-test and t-test significances of greater than 99%. A cloud-resolving weather research and forecast (CR-WRF) model with a two-moment bulk microphysical scheme is employed to consider the effects of an increasing Asian pollution outflow on wintertime precipitation over the North Pacific. The CR-WRF simulations demonstrate more precipitation with elevated polluted continental aerosols than that with typical maritime aerosols, reproducing the observed precipitation trend. The results suggest that the increasing Asian pollution outflow represents one of the most plausible explanations for the increased precipitation trend observed in winter over the North Pacific, likely with important climate implications. Copyright 2008 by the American Geophysical Union."
"7003543851;7005808242;57212781009;6701455548;7005513582;7201520140;","Quantifying climate feedbacks using radiative kernels",2008,"10.1175/2007JCLI2110.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44249092520&doi=10.1175%2f2007JCLI2110.1&partnerID=40&md5=1bb29b3b5c9d7835c3b5d5b9873abcbe","The extent to which the climate will change due to an external forcing depends largely on radiative feedbacks, which act to amplify or damp the surface temperature response. There are a variety of issues that complicate the analysis of radiative feedbacks in global climate models, resulting in some confusion regarding their strengths and distributions. In this paper, the authors present a method for quantifying climate feedbacks based on ""radiative kernels"" that describe the differential response of the top-of-atmosphere radiative fluxes to incremental changes in the feedback variables. The use of radiative kernels enables one to decompose the feedback into one factor that depends on the radiative transfer algorithm and the unperturbed climate state and a second factor that arises from the climate response of the feedback variables. Such decomposition facilitates an understanding of the spatial characteristics of the feedbacks and the causes of intermodel differences. This technique provides a simple and accurate way to compare feedbacks across different models using a consistent methodology. Cloud feedbacks cannot be evaluated directly from a cloud radiative kernel because of strong nonlinearities, but they can be estimated from the change in cloud forcing and the difference between the full-sky and clear-sky kernels. The authors construct maps to illustrate the regional structure of the feedbacks and compare results obtained using three different model kernels to demonstrate the robustness of the methodology. The results confirm that models typically generate globally averaged cloud feedbacks that are substantially positive or near neutral, unlike the change in cloud forcing itself, which is as often negative as positive. © 2008 American Meteorological Society."
"57191497381;36891226500;57196598849;12752728500;","Changing climate and endangered high mountain ecosystems in Colombia",2008,"10.1016/j.scitotenv.2008.02.038","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44149108640&doi=10.1016%2fj.scitotenv.2008.02.038&partnerID=40&md5=abdac15b5fbb7159bb59cd5c79be5550","High mountain ecosystems are among the most sensitive environments to changes in climatic conditions occurring on global, regional and local scales. The article describes the changing conditions observed over recent years in the high mountain basin of the Claro River, on the west flank of the Colombian Andean Central mountain range. Local ground truth data gathered at 4150m, regional data available at nearby weather stations, and satellite info were used to analyze changes in the mean and the variance, and significant trends in climatic time series. Records included minimum, mean and maximum temperatures, relative humidity, rainfall, sunshine, and cloud characteristics. In high levels, minimum and maximum temperatures during the coldest days increased at a rate of about 0.6°C/decade, whereas maximum temperatures during the warmest days increased at a rate of about 1.3°C/decade. Rates of increase in maximum, mean and minimum diurnal temperature range reached 0.6, 0.7, and 0.5°C/decade. Maximum, mean and minimum relative humidity records showed reductions of about 1.8, 3.9 and 6.6%/decade. The total number of sunny days per month increased in almost 2.1 days. The headwaters exhibited no changes in rainfall totals, but evidenced an increased occurrence of unusually heavy rainfall events. Reductions in the amount of all cloud types over the area reached 1.9%/decade. In low levels changes in mean monthly temperatures and monthly rainfall totals exceeded + 0.2°C and - 4% per decade, respectively. These striking changes might have contributed to the retreat of glacier icecaps and to the disappearance of high altitude water bodies, as well as to the occurrence and rapid spread of natural and man-induced forest fires. Significant reductions in water supply, important disruptions of the integrity of high mountain ecosystems, and dramatic losses of biodiversity are now a steady menu of the severe climatic conditions experienced by these fragile tropical environments. © 2008 Elsevier B.V. All rights reserved."
"55686667100;","Two regimes of the equatorial warm pool. Part II: Hybrid coupled GCM experiments",2008,"10.1175/2007JCLI2152.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649107310&doi=10.1175%2f2007JCLI2152.1&partnerID=40&md5=ac4a9f06f14a45382abe18f9a08c2c21","In this second of a two-part study, the two regimes in a simple tropical climate model identified in Part I are verified using a hybrid coupled general circulation model (HCM) that can reproduce the observed climatology and the interannual variability reasonably well. Defining a ratio of basin width between the Pacific and Indian Oceans, a series of parameter sweep experiments was conducted with idealized tropical land geometry. Consistent with the simple model, the HCM simulates two distinct states: the split warm pool regime with large vacillation between the two ocean basins and the single warm pool regime representing current climate. The former is suddenly switched to the latter as the Pacific becomes wider than the Indian Ocean. Furthermore, the vacillation in the split regime reveals a preferred transition route that the warm phase in the Pacific follows that in the Indian Ocean. This route occurs due to convectively coupled Kelvin waves that accompany precipitation anomalies over land. Additional experiments show that the inclusion of the idealized Eurasian continent stabilizes the split regime by reducing the Bjerknes feedback in the Indian Ocean, suggesting the atmosphere-ocean-land interaction at work in maintaining the observed warm pool. No difference in cloud feedback was found between two regimes; this feature may, however, be model dependent. Both the simple model and the HCM results suggest that the tropical atmosphere-ocean system inherently involves multiple solutions, which may have an implication on climate modeling as well as on the understanding of the observed mean climate. © 2008 American Meteorological Society."
"55544443300;7005808242;15026371500;57218978981;","The response of the ITCZ to extratropical thermal forcing: Idealized slab-ocean experiments with a GCM",2008,"10.1175/2007JCLI2146.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649089903&doi=10.1175%2f2007JCLI2146.1&partnerID=40&md5=afcf15f21ed6eb57c6c9121b4549214d","Using a comprehensive atmospheric GCM coupled to a slab mixed layer ocean, experiments are performed to study the mechanism by which displacements of the intertropical convergence zone (ITCZ) are forced from the extratropics. The northern extratropics are cooled and the southern extratropics are warmed by an imposed cross-equatorial flux beneath the mixed layer, forcing a southward shift in the ITCZ. The ITCZ displacement can be understood in terms of the degree of compensation between the imposed oceanic flux and the resulting response in the atmospheric energy transport in the tropics. The magnitude of the ITCZ displacement is very sensitive to a parameter in the convection scheme that limits the entrainment into convective plumes. The change in the convection scheme affects the extratropical-tropical interactions in the model primarily by modifying the cloud response. The results raise the possibility that the response of tropical precipitation to extratropical thermal forcing, important for a variety of problems in climate dynamics (such as the response of the tropics to the Northern Hemisphere ice sheets during glacial maxima or to variations in the Atlantic meridional overturning circulation), may be strongly dependent on cloud feedback. The model configuration described here is suggested as a useful benchmark helping to quantify extratropical-tropical interactions in atmospheric models. © 2008 American Meteorological Society."
"26643250500;56284543100;","A cirrus cloud scheme for general circulation models",2008,"10.1002/qj.301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57349140497&doi=10.1002%2fqj.301&partnerID=40&md5=d30ced01b6865158da8d7fe4d3d95ccd","A statistical cloud scheme for non-convective cirrus formed by homogeneous freezing of supercooled aerosols is presented. As large-scale cirrus clouds exhibit metastable thermodynamic states and have long lifetimes, a fully prognostic approach is developed. The scheme is based on separate probability distribution functions of total water representing clear-sky and in-cloud conditions. These distributions are based on in situ observations and have few degrees of freedom so that they can be used in forecast and climate models. Predictive equations are derived for horizontal cloud fraction and mixing ratios of grid-mean water vapour and ice water, in-cloud water vapour and ice crystal number. The scheme allows sub- and supersaturations with respect to ice to occur in cloud-free air and inside cirrus, and produces nucleated ice crystal concentrations and sizes in good agreement with observations, an important prerequisite for an improved treatment of cirrus cloud radiative properties. Implementation in general circulation models, open issues and future research avenues are discussed. Copyright © 2008 Royal Meteorological Society."
"7102266120;8608733900;","Temporal variability of fair-weather cumulus statistics at the ACRF SGP site",2008,"10.1175/2007JCLI2266.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48749113661&doi=10.1175%2f2007JCLI2266.1&partnerID=40&md5=eac6179bf1dd2b31f77f15469d00ea41","Continental fair-weather cumuli exhibit significant diurnal, day-to-day, and year-to-year variability. This study describes the climatology of cloud macroscale properties, over the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) Southern Great Plains (SGP) site. The diurnal cycle of cloud fraction, cloud-base height, cloud-top height, and cloud thickness were well defined. The cloud fraction reached its maximum value near 1400 central standard time. The average cloud-base height increased throughout the day, while the average cloud thickness decreased with time. In contrast to the other cloud properties, the average cloud-chord length remained nearly constant throughout the day. The sensitivity of the cloud properties to the year-to-year variability of precipitation and day-to-day changes in the height of the lifting condensation level (zLCL) and surface fluxes were compared. The cloud-base height was found to be sensitive to both the year, zLCL, and the surface fluxes of heat and moisture; the cloud thickness was found to be more sensitive to the year than to zLCL; the cloud fraction was sensitive to both the low-level moisture and the surface sensible heat flux; and cloud-chord length was sensitive to zLCL. Distributions of the cloud-chord length over the ACRF SGP site were computed and were well fit by an exponential distribution. The contribution to the total cloud fraction by clouds of each cloud-chord length was computed, and it was found that the clouds with a chord length of about 1 km contributed most to the observed cloud fraction. This result is similar to observations made with other remote sensing instruments or in modeling studies, but it is different from aircraft observations of the contribution to the total cloud fraction by clouds of different sizes. © 2008 American Meteorological Society."
"24491749700;7203001286;7202262257;","Direct and indirect shortware radiative effects of sea salt aerosols",2008,"10.1175/2007JCLI2063.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48749083308&doi=10.1175%2f2007JCLI2063.1&partnerID=40&md5=1ebadced87c3f2a2c9f345c906e322cf","Sea salt aerosols play a dual role in affecting the atmospheric radiative balance. Directly, sea salt particles scatter the incoming solar radiation and absorb the outgoing terrestrial radiation. By acting as cloud condensation nuclei, sea salt aerosols indirectly modulate the atmospheric radiative budget through their effective contribution to cloud formation. Using the Canadian Aerosol Module (CAM)-Canadian Centre for Climate Modelling and Analysis (CCCma) GCM, version 3 (GCM3) framework, the direct as well as the indirect shortwave (SW) radiative effects of sea salt aerosols are simulated. The model results herein suggest that sea salt aerosols exert a significant direct radiative effect over oceanic regions, with seasonal means in the range from -2 to -3 W m-2 over the Southern Ocean. Globally, sea salt's SW indirect effect (annual mean -0.38 W m-2) is found to be less than its direct effect (annual mean -0.65 W m-2). However, sea salt's indirect effect is found to be far stronger over the Southern Hemisphere than over the Northern Hemisphere, especially over the Southern Ocean with seasonal means around -4 W m-2, Which exceed its direct effect. The model results herein suggest that sea salt aerosols significantly modulate the atmospheric radiation budget over oceanic regions and need to be accounted for in global climate models. © 2008 American Meteorological Society."
"35461763400;7102084129;","Aerosol-cloud-precipitation interactions. Part 1. The nature and sources of cloud-active aerosols",2008,"10.1016/j.earscirev.2008.03.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44649155674&doi=10.1016%2fj.earscirev.2008.03.001&partnerID=40&md5=0d28fbe48bb0dc387b0442ccaf5b364d","Atmospheric aerosol particles serve as condensation nuclei for the formation of both, cloud droplets and atmospheric ice particles. As a result, they exert a substantial influence on the microphysical properties of water and ice clouds, which in turn affect the processes that lead to the formation of rain, snow, hail, and other forms of precipitation. In recent years, considerable progress has been made in understanding the chemical composition of aerosols, their microphysical properties, and the factors that enable them to act as cloud condensation nuclei (CCN) and ice nuclei (IN). The first part of this review article will focus on the nature and sources of CCN and IN. We discuss the fundamentals of the cloud droplet and ice nucleation processes, and the role that the chemical composition and particle size play in this process. We show that, in many instances, the influence of chemical composition can be represented by a simple parameterization, which leaves particle size as the main variable controlling CCN efficiency. Aerosol particles are produced either directly by anthropogenic and natural sources (dust, sea salt, soot, biological particles, etc.), or they are formed in the atmosphere by condensation of low-volatility compounds (e.g., sulfuric acid or oxidized organic compounds). We discuss the magnitude of these sources, and the CCN and IN characteristics of the particles they produce. In contrast to previous assessments, which focused on the aerosol mass, we are emphasizing the number of particles being produced, as this is the key variable in cloud microphysics. Large uncertainties still exist for many aerosol sources, e.g., the submicron part of the seaspray aerosol, the particles produced by the biosphere, and the secondary organic aerosol. We conclude with a discussion on what particle concentrations may have been in the pristine atmosphere, before the onset on anthropogenic pollution. Model calculations and observations in remote continental regions consistently suggest that CCN concentrations over the pristine continents were similar to those now prevailing over the remote oceans, suggesting that human activities have modified cloud microphysics more than what is reflected in conventional wisdom. The second part of this review will address the effects of changing CCN and IN abundances on precipitation processes, the water cycle, and climate. © 2008 Elsevier B.V. All rights reserved."
"6603813334;8080847900;6603581921;","Volcanic ash forecast - Application to the May 2008 Chaitén eruption",2008,"10.5194/nhess-8-927-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50949098934&doi=10.5194%2fnhess-8-927-2008&partnerID=40&md5=3fbe6ba19e23a470a7b5d229c532b322","We model the transport and subsequent deposition of ash from Chaitén volcano, Chile, during the first week of May 2008. The simulation couples the Weather Research and Forecasting (WRF) meteorological model with the FALL3D dispersion model. We only use semi-quantitative volcanological inputs based on the first eruption reports. We consider two different run types based on forecasted and hindcasted meteorological conditions. The first simulation type can be regarded as a syn-eruptive operational forecast for the 2ĝ€""8 May period. We predict the evolution of the ash cloud position, the concentration of ash on air, the expected deposit thickness, and the ash accumulation rates at different localities. The comparison of model results with observed cloud arrival times and satellite images shows the goodness of the combined WRF+FALL3D forecast system and points out the feasibility of combining these two models for short-term forecast of volcanic clouds and ash fallout."
"7403906746;23668415500;","Air-earth current density measurements at Lerwick; implications for seasonality in the global electric circuit",2008,"10.1016/j.atmosres.2008.01.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44649150528&doi=10.1016%2fj.atmosres.2008.01.008&partnerID=40&md5=8a514201fc83eae4af208c05b5ff958e","Atmospheric electricity measurements were made at Lerwick Observatory in the Shetland Isles (60°09′N, 1°08′W) during most of the 20th century. The Potential Gradient (PG) was measured from 1926 to 84 and the air-earth conduction current (Jc) was measured during the final decade of the PG measurements. Daily Jc values (1978-1984) observed at 15 UT are presented here for the first time, with independently-obtained PG measurements used to select valid data. The 15 UT Jc (1978-1984) spans 0.5-9.5 pA/m2, with median 2.5 pA/m2; the columnar resistance at Lerwick is estimated as 70 PΩm2. Smoke measurements confirm the low pollution properties of the site. Analysis of the monthly variation of Lerwick Jc data shows that winter (DJF) Jc is significantly greater than the summer (JJA) Jc by 20%. The Lerwick atmospheric electricity seasonality differs from the global lightning seasonality, but Jc has a similar seasonal phasing to that observed in Nimbostratus clouds globally, suggesting a role for non-thunderstorm rain clouds in the seasonality of the global circuit. © 2008 Elsevier B.V. All rights reserved."
"16443990500;21734131700;13204674800;7006347751;","Water adsorption and cloud condensation nuclei activity of calcite and calcite coated with model humic and fulvic acids",2008,"10.1016/j.atmosenv.2008.03.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46749140890&doi=10.1016%2fj.atmosenv.2008.03.005&partnerID=40&md5=576f3d2b44b8c0015a7fb455f501757b","Recent studies have shown that organics can alter the water adsorption and cloud condensation nuclei (CCN) activity of common deliquescent species in the Earth's atmosphere. However, very little is known about the effect of organics on water adsorption and CCN activity of insoluble nuclei, such as mineral dust aerosol. A large fraction of unidentified organic material in aerosol particles is composed of poly-acidic compounds resembling humic substances. The presence of these humic-like substances (HULIS) can alter the water adsorption and CCN activity of mineral dust aerosol. We have measured the CCN activity of model humic and fulvic acids and of mineral dust particles coated with these substances in the laboratory. We find that coatings of humic and fulvic acids on calcite particles significantly increases water adsorption compared to uncoated particles. CCN measurements indicate that humic- or fulvic acid-coated calcite particles are more CCN active than uncoated calcite particles. Additionally, thicker coatings of humic or fulvic acids appear to result in more efficient CCN activity. Thus, mineral dust particles coated with high molecular weight organic materials will take up more water and become more efficient CCN in the atmosphere than uncoated mineral dust particles, potentially altering the effect of mineral dust on the Earth's climate. In addition to the experimental results, we have explored a newly modified Köhler theory for predicting the CCN activity of insoluble, wettable particles based on multi layer water adsorption measurements of calcite. © 2008 Elsevier Ltd. All rights reserved."
"25941200000;8397494800;24322005900;57205867148;6701511324;6603613067;7003557662;","The Monte Carlo independent column approximation: An assessment using several global atmospheric models",2008,"10.1002/qj.303","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57349086394&doi=10.1002%2fqj.303&partnerID=40&md5=3cc1c4c7d6ea2446551b3f417f8bc50a","The Monte Carlo Independent Column Approximation (McICA) computes domain-average, broadband radiative flux profiles within conventional global climate models (GCMs). While McICA is unbiased with respect to the full ICA, it generates, as a by-product, random noise. If this by-product leads to statistically significant impacts on GCM simulations, it could limit the usefulness of McICA. This paper assesses the impact of McICA's random noise on six GCMs. To this end, the GCMs performed ensembles of 14-day long simulations for various renditions of McICA, each with differing amounts of random noise. As seen in the past, low-cloud fraction and surface temperature were affected most by noise. However, all GCM simulations using operationally viable renditions of McICA showed no statistically significant impacts, even for precipitation - a highly intermittent variable that one might expect to be sensitive to random fluctuations. Two GCMs showed statistically significant responses using an academic version of McICA that generates overly large sampling noise. Time series analyses of high-resolution (i.e. typically 2-hourly) data revealed that fluctuations associated with most variables and GCMs are immune to McICA noise. Moreover, the nature of these fluctuations can vary substantially among GCMs and most often they overwhelm any noise impacts. Overall, the results presented here corroborate a range of previous studies done on one GCM at a time: random noise produced by recommended versions of McICA has statistically insignificant effects on GCM simulations. Copyright © 2008 Royal Meteorological Society and Her Majesty in Right of Canada."
"23493195700;7003679485;14822032600;7102582535;17341189400;","Origin of black carbon concentration peaks in Cairo (Egypt)",2008,"10.1016/j.atmosres.2008.01.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44649175828&doi=10.1016%2fj.atmosres.2008.01.004&partnerID=40&md5=8eea7452121d500240bc82e31166d6b3","The concentration in black carbon (BC) has been monitored in the megacity of Cairo (Egypt) during the autumn 2004 and spring 2005 intensive observation periods of the Cairo Aerosol CHaracterization Experiment (CACHE). As expected for a species released by human activities, hourly mean of this concentration is found to be large at all times. It is also significantly larger in autumn than in spring (9.9 ± 6.6 and 6.9 ± 4.8 μgC/m3, respectively) and quite variable at shorter (diurnal) time scales. Indeed, sharp concentration peaks larger than 25 μgC/m3 are frequently detected during both observation periods. In order to apportion the roles played by emission intensity and meteorological conditions in the development of these peaks, a simple model is developed that allows derivation of the hourly mean BC emissions by the part of town located upwind of the measurement site. The analysis of the time dependence of these emissions indicates that traffic is by far the major source of BC in Cairo during daytime and this even in autumn when biomass burning takes place in the Nile delta. It is only between 03:00 and 05:00 in the night, at a time when traffic emissions are quite reduced, that the influence of this particular source on BC concentration can become significant. This study also indicates that BC emissions by motorized traffic remain important from the morning rush hour until late in the night. During the day, and particularly in spring, the dilution effect resulting from the development of the planetary boundary layer prevents BC concentrations from becoming very large. This is no longer the case just before sunrise and after sunset, when the combination of dense traffic and low boundary layer is responsible for the observed sharp increase in BC concentration. © 2008 Elsevier B.V. All rights reserved."
"15723754100;55695193600;7501797728;35271129900;","MM5 simulations of the China regional climate during the LGM. I: Influence of CO2 and earth orbit change",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-45749130606&partnerID=40&md5=5bddc85149f608e5a277c6081474d216","Using a regional climate model MM5 nested to an atmospheric global climate model CCM3, a series of simulations and sensitivity experiments have been performed to investigate the relative Last Glacial Maximum (LGM) climate response to different mechanisms over China. Model simulations of the present day (PD) climate and the LGM climate change are in good agreement with the observation data and geological records, especially in the simulation of precipitation change. Under the PD and LGM climate, changes of earth orbital parameters have a small influence on the annual mean temperature over China. However, the magnitude of the effect shows a seasonal pattern, with a significant response in winter. Thus, this influence cannot be neglected. During the LGM, CO2 concentration reached its lowest point to 200 ppmv. This results in a temperature decrease over China. The influences of CO2 concentration on climate show seasonal and regional patterns as well, with a significant influence in winter. On the contrary, CO2 concentration has less impact in summer season. In some cases, temperature even increases with decreasing in CO2 concentration. This temperature increase is the outcome of decrease in cloud amount; hence increase the solar radiation that reached the earth's surface. This result suggests that cloud amount plays a very important role in climate change and could direct the response patterns of some climate variables such as temperature during certain periods and over certain regions. In the Tibetan Plateau, the temperature responses to changes of the above two factors are generally weaker than those in other regions because the cloud amount in this area is generally more than in the other areas. Relative to the current climate, changes in orbital parameters have less impact on the LGM climate than changes in CO2 concentration. However, both factors have rather less contributions to the climate change in the LGM. About 3%-10% changes in the annual mean temperature are contributed by CO2."
"55624487771;55273023800;54380973500;24398609500;","Research on water-vapor distribution in the air over Qilian Mountains",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-45749109024&partnerID=40&md5=7fdfe89cffd5d66dd0390498b33ba003","Based on the remote sensing data, the radiosonde data and precipitation data observed by weather stations, distributions of atmospheric water-vapor and cloud motion wind over the Qilian Mountains are analyzed. Moreover, on the basis of water-vapor and cloud motion wind analyses, relations of atmospheric water-vapor distribution with precipitation, atmospheric circulation, and terrain are investigated. The results show that distributions of atmospheric water-vapor and precipitation in the Qilian Mountains are affected by the westerly belt, the southerly monsoon (the South Asian monsoon and plateau monsoon), and the East Asian monsoon. In the northwest Qilian Mountains, water-vapor and precipitation are entirely affected by the westerly belt, and there is no other direction water-vapor transport except westerly water-vapor flux, hence, the northwest region is regarded as the westerly belt region. In the south and middle of the mountains, water-vapor is mainly controlled by the southerly monsoon, 37.7% of the total water-vapor is from the south, especially in summer, the southerly water-vapor flux accounts for 55.9% of the total, and furthermore the water-vapor content in the southerly flow is more than that in the westerly flow. The southerly monsoon water-vapor is influenced by the South Asian monsoon from the Indian Ocean and the plateau monsoon in the Qinghai-Tibetan Plateau, thus, the south and middle region is called southerly monsoon region. But in the northeast Qilian Mountains, the East Asian monsoon is the main climate system affecting the water-vapor. Besides west and northwest water-vapor fluxes, there are a lot of easterly water-vapor fluxes in summer. The frequency of easterly cloud motion winds in summer half year accounts for 27.1% of the total, though the frequency is not high, it is the main water-vapor source of summer precipitation in this region, therefore, the northwest region is a marginal region of the East Asian monsoon. On the other hand, atmospheric water-vapor, precipitation, and conversion rate of water-vapor into precipitation are closely related with altitudes and circulation system. Generally, there is a peak value of water-vapor content at the altitude from 3500 to 4500 m on the windward slope, but on the leeward slope, water-vapor monotonically decreases with altitude descending except for that in the East Asian monsoon region. Water-vapor on the leeward is much less than that on the windward slope, and the maximal difference in water-vapor content between the two sides may reach about 4.49 kg m-2. Either the values of water-vapor content, precipitation or the conversion rate of water-vapor into precipitation all reach their maxima in the East Asian monsoon regions, and correspondingly the peak value of water-vapor on the windward is also large and occurs at a lower altitude in comparison with other two regions."
"56134185900;8974620100;24398166200;56424740200;","Heavy rainfall associated with a monsoon depression in South China: Structure analysis",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-45749133099&partnerID=40&md5=426a74018896f68a29d43fdd2d04f1c3","A heavy rainfall associated with the deepening of a monsoon depression happened in the summer of 2005. This process was first diagnostically analyzed and the 3D structure of the monsoon depression was discussed, then this structure was compared with those of the monsoon depression in South Asia and the low vortex in the Meiyu front. The results showed that the heavy rainfall directly resulted from a monsoon depression in South China, and the large-scale environment provided a favorable background for the deepening of the monsoon depression. The 3D structure of the monsoon depression was as follows. In the horizontal direction, there existed a convective cloud band to the south of the monsoon depression, which lay in a convectively instable area, with a relatively strong ascending motion in the mid and low levels of the troposphere, and the ascending motion matched well with a moist tongue, a convergence area, and a band of positive vorticity in the mid and low levels of the troposphere. In the vertical direction, the depression had an obviously cyclonic circulation in the mid and low levels of the troposphere, but no circulation from above 300 hPa. The monsoon depression corresponded to convergence and positive vorticity in the low levels, but to divergence and negative vorticity in the upper levels. The upward draft of the depression could reach the upper levels of the troposphere in the west of the depression, while the descending motion lay in the east. There was a low-level jet to the south of the depression, while the upper-level jet was not obvious. The depression was vertically warm in the upper levels and cold in the low levels, and the axis of the depression tilted southeastward with height, whose characteristics were different not only from the monsoon depression in South Asia but also from the low vortex in the Meiyu front."
"9534896800;55905970100;24757986500;7003439364;7801344746;6508074920;7004289682;7006497723;57202413846;36124109400;7202708167;6603797815;6603129558;","Aerosol and cloud effects on solar brightening and the recent rapid warming",2008,"10.1029/2008GL034228","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50849136519&doi=10.1029%2f2008GL034228&partnerID=40&md5=49a4975c06e943856271fc5016ce58d3","The rapid temperature increase of 1°C over mainland Europe since 1980 is considerably larger than the temperature rise expected from anthropogenic greenhouse gas increases. Here we present aerosol optical depth measurements from six specific locations and surface irradiance measurements from a large number of radiation sites in Northern Germany and Switzerland. The measurements show a decline in aerosol concentration of up to 60%, which have led to a statistically significant increase of solar irradiance under cloud-free skies since the 1980s. The measurements confirm solar brightening and show that the direct aerosol effect had an approximately five times larger impact on climate forcing than the indirect aerosol and other cloud effects. The overall aerosol and cloud induced surface climate forcing is ∼+1 W M-2 dec-1 and has most probably strongly contributed to the recent rapid warming in Europe. Copyright 2008 by the American Geophysical Union."
"7404211378;7403681584;8848449400;","Low cloud errors over the southeastern Atlantic in the NCEP CFS and their association with lower-tropospheric stability and air-sea interaction",2008,"10.1029/2007JD009514","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50049112969&doi=10.1029%2f2007JD009514&partnerID=40&md5=bbe8f6019d3c5661b2d6507d4aacaf65","The low cloud errors in the tropical Atlantic and their connection with lower-tropospheric stability and air-sea interaction in a simulation of the Climate Forecast System (CFS) are investigated. The CFS is the coupled ocean-atmosphere circulation model for operational climate prediction at the National Centers for Environmental Prediction. Compared with observations, the CFS produces too few low clouds over the southeastern Atlantic and too many high clouds over the whole tropical Atlantic. The center of the low clouds is also shifted westward in the model away from the cold tongue region to the central ocean. The underestimation of low clouds in the southeastern Atlantic may be one of the potential sources of the warm biases of sea surface temperature (SST) in this region. The low clouds are linked to a stable or inversion layer between 850 hPa and 925 hPa in observations, but are associated with a stable layer between 700 hPa and 850 hPa in the CFS, which may suggest that low clouds are generated in a higher layer in the CFS than in the real world. On average, the lower troposphere is less stable in the CFS than in the observations over the tropical Atlantic region, which is more favorable for the development of deep convection. Moreover, the low cloud variability in the South Atlantic is mainly associated with SST and wind stress anomalies in the subtropical South Atlantic in the CFS and in the southeastern Atlantic and along the African coast in the observations. Copyright 2008 by the American Geophysical Union."
"23995400000;7404243086;7202079615;","A study of anthropogenic impacts of the radiation budget and the cloud field in East Asia based on model simulations with GCM",2008,"10.1029/2007JD009325","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50049110527&doi=10.1029%2f2007JD009325&partnerID=40&md5=1c26c0a4dbf5e1402745624c13c2cb63","We investigated the effects of man-made air pollutants on the climate of East Asia, focusing on eastern China where anthropogenic aerosol concentrations are rapidly increasing. The increasing emission of anthropogenic aerosols causes serious air pollution episodes and various effects on the climate in this region. It is therefore necessary to quantify the contribution of aerosols to the change in the radiation budget and the cloud field. Our purpose of this study is to evaluate the sensitivity of anthropogenic aerosols and other anthropogenic factors such as greenhouse gas (GHG) upon the radiative forcing. Then an aerosol transport model coupled to a general circulation model and an ocean mixed-layer model was used to investigate the relationships among the anthropogenic aerosol forcing, GHG forcing, surface radiation budget, and cloud field. Our simulation results showed that copious anthropogenic aerosol loading causes significant decrease in the surface downward shortwave radiation flux (SDSWRF), which indicates that a direct effect of aerosols has the greatest influence on the surface radiation. It is found from our model simulations that low-level clouds increase but convective clouds decrease due to reduced convective activity caused by surface cooling when anthropogenic aerosol increases, and GHG increase has an insignificant effect on SDSWRF but a significant effect on the cloud field. In other word model simulations suggested that the aerosol forcing mainly causes a reduction of SDSWRF, whereas the change in the cloud field is influenced both anthropogenic aerosol and GHG effects. Thus this work demonstrated with sensitivity experiments the importance of aerosols to cause significant climate effects in the East Asian region, though further study is needed because our study is based on results from one specific model and limited data analysis. Copyright 2008 by the American Geophysical Union."
"7003900064;7004353965;","Incident spectral irradiance in the Arctic Basin during the summer and fall",2008,"10.1029/2007JD009418","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50049113234&doi=10.1029%2f2007JD009418&partnerID=40&md5=0b51d8c75ff51645eddcec99d5c5176a","Calibrated values of incident spectral irradiance are reported from the Healy Oden Transarctic Experiment during August and September 2005. Spectra were obtained for a wide range of solar zenith angles, cloud conditions, and surface types to provide basic data for regional shortwave radiative energy balance calculations as well as climate model parameterization and validation. Supervised principal component analysis on the spectral continuum showed that three principal components explain over 99% of the variance resulting from darkening across the solar spectrum with increasing cloud cover by volume scattering, from stronger attenuation in the solar infrared relative to visible wavelengths by H<inf>2</inf>O, and from Rayleigh scattering. Comparison of the observations with the atmospheric radiation model SBDART showed that good agreement was obtained varying only the cloud optical depth. Applying the model, we showed how the surface albedo affects incident spectral irradiance under clear as well as cloudy skies, and we obtained a quantitative estimate of the visual effects of ""water sky"" and ""ice blink."" We also determined the spectral albedo of the atmosphere for a dense arctic stratus cloud deck decoupled from the influence of the underlying surface. Incident spectral irradiances were integrated numerically and compared with calibrated pyranometer observations. Agreement was within 5% for cases where the cloud transparency and incident irradiance did not fluctuate strongly over the 10-min pyranometer recording intervals. A new set of values for total albedo for clear versus cloudy conditions at high and low Sun angles is presented for six prominent arctic surface types. Copyright 2008 by the American Geophysical Union."
"8525144100;7003278104;7201463831;7405857939;7005973015;10440447800;6603434295;7005002831;57203174863;55725404100;","Does the Madden-Julian Oscillation influence aerosol variability?",2008,"10.1029/2007JD009372","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50049084896&doi=10.1029%2f2007JD009372&partnerID=40&md5=34ab1768a9f63252c458b39faa6a9415","We investigate the modulation of aerosols by the Madden-Julian Oscillation (MJO) using multiple, global satellite aerosol products: aerosol index (AI) from the Total Ozone Mapping Spectrometer (TOMS) on Nimbus-7, and aerosol optical thickness (AOT) from the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua and the Advanced Very High Resolution Radiometer (AVHRR) on NOAA satellites. A composite MJO analysis indicates that large variations in the TOMS AI and MODIS/AVHRR AOT are found over the equatorial Indian and western Pacific Oceans where MJO convection is active, as well as the tropical Africa and Atlantic Ocean where MJO convection is weak but the background aerosol level is high. A strong inverse linear relationship between the TOMS AI and rainfall anomalies, but a weaker, less coherent positive correlation between the MODIS/AVHRR AOT and rainfall anomalies, were found. The MODIS/AVHRR pattern is consistent with ground-based Aerosol Robotic Network data. These results indicate that the MJO and its associated cloudiness, rainfall, and circulation variability systematically influence the variability in remote sensing aerosol retrieval results. Several physical and retrieval algorithmic factors that may contribute to the observed aerosol-rainfall relationships are discussed. Preliminary analysis indicates that cloud contamination in the aerosol retrievals is likely to be a major contributor to the observed relationships, although we cannot exclude possible contributions from other physical mechanisms. Future research is needed to fully understand these complex aerosol-rainfall relationships. Copyright 2008 by the American Geophysical Union."
"55470017900;7004692414;","Glaciation of a mixed-phase boundary layer cloud at a coastal arctic site as depicted in continuous lidar measurements",2008,"10.1016/j.polar.2008.04.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-47749099236&doi=10.1016%2fj.polar.2008.04.004&partnerID=40&md5=8c3275b0bc180e798862ed453012e8b1","The dynamic seeding and glaciation of a mixed-phase cloud by ice crystals injected from above at Ny Ålesund, Svalbard, Norway is described using continuous lidar measurements and thermodynamic data. Glaciation of this cloud was caused by ice crystal growth and sedimentation due to the preferential differences in saturation vapor pressure over ice versus liquid water and riming. The lidar data suggest that precipitation reached the ground for nearly 4 h as a result. The symbiosis between ice and liquid water hydrometeor presence in the polar troposphere is unique. Thermal perturbations and airmass fluctuations influence microphysical cloud characteristics and radiative balance, which makes the otherwise pristine region sensitive to lower-latitude anthropogenic and biogenic influences and a focal point for observing indirect effects and their influence on climate change. The development of lidar technologies capable of continuous and autonomous measurements is yielding important datasets to study unique atmospheric phenomena. © 2008 Elsevier B.V. and NIPR."
"24597575200;7401459840;7005922731;","Climate change scenario for Costa Rican montane forests",2008,"10.1029/2008GL033940","https://www.scopus.com/inward/record.uri?eid=2-s2.0-49849086557&doi=10.1029%2f2008GL033940&partnerID=40&md5=15b3978d4af1dcc1c08da5ae83388f64","Tropical montane cloud forests are characterized by persistent immersion in clouds, an important source of moisture during the dry season. Future changes in temperature and precipitation could alter cloud cover at the vegetation level and seriously affect mountain ecosystems. A regional climate modeling study that focuses on changes in the distributions of temperature and precipitation in Costa Rica shows, in general, an increase in temperature and a decrease in precipitation under the A2 scenario. At high elevations, warming is amplified and future temperature distribution lies outside the range of present-day distribution. Compared to the Caribbean side, temperature changes are greater at high elevations on the Pacific side. Model results also show significant changes in precipitation amounts and variability and an increase in the altitude of cloud formation on the Pacific side that may have serious implications for mountain ecosystems in and around Costa Rica. Copyright 2008 by the American Geophysical Union."
"24491985100;7005449794;","Modeling the hydroclimatology of Kuwait: The role of subcloud evaporation in semiarid climates",2008,"10.1175/2007JCLI2123.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48749094700&doi=10.1175%2f2007JCLI2123.1&partnerID=40&md5=7660914ebdc476f9f42a8111d944e76c","A new subcloud layer evaporation scheme is incorporated into Regional Climate Model, version 3. (RegCM3), to better simulate the rainfall distribution over a semiarid region around Kuwait. The new scheme represents subcloud layer evaporation of convective as well as large-scale rainfall. Model results are compared to observations from rain gauge data networks and satellites. The simulations show significant response to the incorporation of subcloud layer evaporation as a reduction by as much as 20% in annual rainfall occurs over the region. As a result, the new model simulations of annual rainfall are within 15% of observations. In addition, results indicate that the interannual variability of rainfall simulated by RegCM3 is sensitive to the specification of boundary conditions. For example, forcing RegCM3's lateral boundary conditions with the 40-yr ECMWF Re-Analysis (ERA-40) data, instead of NCEP-NCAR's Reanalysis Project 2 (NNRP2), reduces interannual variability by over 25%. Moreover, with subcloud layer evaporation incorporated and ERA-40 boundary conditions implemented, the model's bias and root-mean-square error are significantly reduced. Therefore, the model's ability to reproduce observed annual rainfall and the year-to-year variation of rainfall is greatly improved. Thus, these results elucidate the critical role of this natural process in simulating the hydroclimatology of semiarid climates. Last, a large discrepancy between observation datasets over the region is observed. It is believed that the inherent characteristics that are used to construct these datasets explain the differences observed in the annual and interannual variability of Kuwait's rainfall. © 2008 American Meteorological Society."
"7006518289;6701508272;57203406068;","A coupled air-sea response mechanism to solar forcing in the Pacific region",2008,"10.1175/2007JCLI1776.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46449091082&doi=10.1175%2f2007JCLI1776.1&partnerID=40&md5=d863cf757de48f49a69b9bada3f2591d","The 11-yr solar cycle [decadal solar oscillation (DSO)] at its peaks strengthens the climatological precipitation maxima in the tropical Pacific during northern winter. Results from two global coupled climate model ensemble simulations of twentieth-century climate that include anthropogenic (greenhouse gases, ozone, and sulfate aerosols, as well as black carbon aerosols in one of the models) and natural (volcano and solar) forcings agree with observations in the Pacific region, though the amplitude of the response in the models is about half the magnitude of the observations. These models have poorly resolved stratospheres and no 11-yr ozone variations, so the mechanism depends almost entirely on the increased solar forcing at peaks in the DSO acting on the ocean surface in clear sky areas of the equatorial and subtropical Pacific. Mainly due to geometrical considerations and cloud feedbacks, this solar forcing can be nearly an order of magnitude greater in those regions than the globally averaged solar forcing. The mechanism involves the increased solar forcing at the surface being manifested by increased latent heat flux and evaporation. The resulting moisture is carried to the convergence zones by the trade winds, thereby strengthening the intertropical convergence zone (ITCZ) and the South Pacific convergence zone (SPCZ). Once these precipitation regimes begin to intensify, an amplifying set of coupled feedbacks similar to that in cold events (or La Niña events) occurs. There is a strengthening of the trades and greater upwelling of colder water that extends the equatorial cold tongue farther west and reduces precipitation across the equatorial Pacific, while increasing precipitation even more in the ITCZ and SPCZ. Experiments with the atmosphere component from one of the coupled models are performed in which heating anomalies similar to those observed during DSO peaks are specified in the tropical Pacific. The result is an anomalous Rossby wave response in the atmosphere and consequent positive sea level pressure (SLP) anomalies in the North Pacific extending to western North America. These patterns match features that occur during DSO peak years in observations and the coupled models. © 2008 American Meteorological Society."
"36538539800;","Online-coupled meteorology and chemistry models: History, current status, and outlook",2008,"10.5194/acp-8-2895-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45349092233&doi=10.5194%2facp-8-2895-2008&partnerID=40&md5=c3298fcf3f33a63551b0bbd6e4946f80","The climate-chemistry-aerosol-cloud-radiation feedbacks are important processes occurring in the atmosphere. Accurately simulating those feedbacks requires fully-coupled meteorology, climate, and chemistry models and presents significant challenges in terms of both scientific understanding and computational demand. This paper reviews the history and current status of the development and application of online-coupled meteorology and chemistry models, with a focus on five representative models developed in the US including GATOR-GCMOM, WRF/Chem, CAM3, MIRAGE, and Caltech unified GCM. These models represent the current status and/or the state-of-the science treatments of online-coupled models worldwide. Their major model features, typical applications, and physical/chemical treatments are compared with a focus on model treatments of aerosol and cloud microphysics and aerosol-cloud interactions. Aerosol feedbacks to planetary boundary layer meteorology and aerosol indirect effects are illustrated with case studies for some of these models. Future research needs for model development, improvement, application, as well as major challenges for online-coupled models are discussed."
"7003532926;","Relation between temperature sensitivity to doubled carbon dioxide and the distribution of clouds in current climate models",2008,"10.1134/S0001433808030043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-47249154873&doi=10.1134%2fS0001433808030043&partnerID=40&md5=b2f46dacfec8594ecf11e45cd92ad5a5","The paper considers a relation between equilibrium global warming at doubled carbon dioxide (climate sensitivity) and the distribution of clouds and relative humidity in 18 state-of-the-art climate models. There is a strong correlation among three indices: (1) model climate sensitivity, (2) mean cloud amount change due to global warming, and (3) the difference in cloud amount between the tropics and midlatitudes. In the simulation of the present-day current, models with high sensitivity produce smaller clouds amounts in the tropics and larger cloud amounts over midlatitude oceans than models with low sensitivity. The relative humidity in the tropics is smaller in models with high sensitivity than in models with low sensitivity. There is a similarity between vertical profiles of cloud amount and relative humidity under global warming and vertical profiles of the difference in these quantities averaged over the tropics and midlatitudes. Based on the correlations obtained and observations of cloud amount and relative humidity, an estimate is made of the sensitivity of a real climate system. © Pleiades Publishing, Ltd. 2008."
"57219951382;7102495313;7004920873;","Cloud radiative forcing of subtropical low level clouds in global models",2008,"10.1007/s00382-007-0322-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42349093515&doi=10.1007%2fs00382-007-0322-1&partnerID=40&md5=9d66d9bd655d1b69a4661e38eb935b5d","Simulations of subtropical marine low clouds and their radiative properties by nine coupled ocean-atmosphere climate models participating in the fourth assesment report (AR4) of the intergovernmental panel on climate change (IPCC) are analyzed. Satellite observations of cloudiness and radiative fluxes at the top of the atmosphere (TOA) are utilized for comparison. The analysis is confined to the marine subtropics in an attempt to isolate low cloudiness from tropical convective systems. All analyzed models have a negative bias in the low cloud fraction (model mean bias of -15%). On the other hand, the models show an excess of cloud radiative cooling in the region (model mean excess of 13 W m-2). The latter bias is shown to mainly originate from too much shortwave reflection by the models clouds rather than biases in the clear-sky fluxes. These results confirm earlier studies, thus no major progress in simulating the marine subtropical clouds is noted. As a consequence of the combination of these two biases, this study suggests that all investigated models are likely to overestimate the radiative response to changes in low level subtropical cloudiness. © Springer-Verlag 2007."
"8922308700;7102266120;7006270084;7003666669;","The Explicit-Cloud Parameterized-Pollutant hybrid approach for aerosol-cloud interactions in multiscale modeling framework models: Tracer transport results",2008,"10.1088/1748-9326/3/2/025005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46749087994&doi=10.1088%2f1748-9326%2f3%2f2%2f025005&partnerID=40&md5=95a4e7a980357336f4704696e89319ce","All estimates of aerosol indirect effects on the global energy balance have either completely neglected the influence of aerosol on convective clouds or treated the influence in a highly parameterized manner. Embedding cloud-resolving models (CRMs) within each grid cell of a global model provides a multiscale modeling framework for treating both the influence of aerosols on convective as well as stratiform clouds and the influence of clouds on the aerosol, but treating the interactions explicitly by simulating all aerosol processes in the CRM is computationally prohibitive. An alternate approach is to use horizontal statistics (e.g., cloud mass flux, cloud fraction, and precipitation) from the CRM simulation to drive a single-column parameterization of cloud effects on the aerosol and then use the aerosol profile to simulate aerosol effects on clouds within the CRM. Here, we present results from the first component of the Explicit-Cloud Parameterized-Pollutant parameterization to be developed, which handles vertical transport of tracers by clouds. A CRM with explicit tracer transport serves as a benchmark. We show that this parameterization, driven by the CRM's cloud mass fluxes, reproduces the CRM tracer transport significantly better than a single-column model that uses a conventional convective cloud parameterization. © IOP Publishing Ltd."
"24398842400;57203053317;57201904116;56250185400;","The global influence of dust mineralogical composition on heterogeneous ice nucleation in mixed-phase clouds",2008,"10.1088/1748-9326/3/2/025003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45749115495&doi=10.1088%2f1748-9326%2f3%2f2%2f025003&partnerID=40&md5=35af98de1e4b546c179ab1d9aced1a4b","Mineral dust is the dominant natural ice nucleating aerosol. Its ice nucleation efficiency depends on the mineralogical composition. We show the first sensitivity studies with a global climate model and a three-dimensional dust mineralogy. Results show that, depending on the dust mineralogical composition, coating with soluble material from anthropogenic sources can lead to quasi-deactivation of natural dust ice nuclei. This effect counteracts the increased cloud glaciation by anthropogenic black carbon particles. The resulting aerosol indirect effect through the glaciation of mixed-phase clouds by black carbon particles is small (+0.1 W m-2 in the shortwave top-of-the-atmosphere radiation in the northern hemisphere). © IOP Publishing Ltd."
"7006550762;","The consequences of not knowing low- and high-latitude Climate sensitivity",2008,"10.1175/2007BAMS2520.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-49249122249&doi=10.1175%2f2007BAMS2520.1&partnerID=40&md5=f2cd7098ae3c2b97dec5b63dcaf05617","Along with the continuing uncertainty associated with global climate sensitivity [2°-4.5°+, for doubled CO2 in the latest Inter-governmental Panel on Climate Change (IPCC) report], we have not made much progress in improving our understanding of the past/future sensitivity of low- and high-latitude climates. Disagreements in paleoclimate interpretations, and diverse results from the IPCC Fourth Assessment Report future climate model simulations suggest that this uncertainty is still a factor of 2 in both latitude regimes. Cloud cover is the primary reason for model discrepancies at low latitudes, while snow/sea ice differences along with cloud cover affect the high-latitude response. While these uncertainties obviously affect our ability to predict future climate-change impacts in the tropics and polar regions directly, the uncertainty in latitudinal temperature gradient changes affects projections of future atmospheric dynamics, including changes in the tropical Hadley cell, midlatitude storms, and annual oscillation modes, with ramifications for regional climates. In addition, the uncertainty extends to the patterns of sea surface temperature changes, with, for example, no consensus concerning longitudinal gradient changes within each of the tropical oceans. We now know a good deal more about how latitudinal and longitudinal gradients affect regional climates; we just do not know how these gradients will change. New satellite observations and field programs are underway, which should help improve our modeling capability, although there is no guarantee that these issues will be resolved before a substantial global warming impact is upon us. A review of this topic is presented here. © 2008 American Meteorological Society."
"6701854276;7102912169;6603589745;","Spatial and temporal varying thresholds for cloud detection in GOES imagery",2008,"10.1109/TGRS.2008.916208","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44049098809&doi=10.1109%2fTGRS.2008.916208&partnerID=40&md5=22047b7df33ed1719533e698635330cb","A new cloud detection technique has been developed and applied to GOES-12 Imager data. The bispectral composite threshold (BCT) technique uses only the 11- and 3.9-μm channels, and composite imagery generated from these channels, in a four-step cloud detection procedure to produce a binary cloud mask at single-pixel resolution. An innovative aspect of this algorithm is the use of 20-day composites of the 11- and the 11-3.9-μm channel difference imagery to represent spatially and temporally varying clear-sky thresholds for the bispectral cloud tests. The BCT cloud detection technique has been validated against a ""truth"" data set generated by the manual determination of the sky conditions from available satellite imagery for four seasons during 2003-2004. The day-and-night algorithm has been shown to determine the correct sky conditions 87.6% of the time (on average) over the eastern two-thirds of the U.S. and surroundings oceans. The incorrectly determined conditions arose from missing clouds 8.9% of the time or from overdetermining clouds 3.5% of the time. Nearly 82% of the misses came in the presence of low clouds. Only small variations in algorithm performance occurred between day-night, land-ocean, and between seasons. The algorithm performed best in the warmer seasons (90.9% correct during the summer versus 81.8% correct in the winter season) and during the day, when the solar illumination provides enhanced surface atmospheric cloud contrast in the infrared channels, and least well during the winter season. The algorithm was found to slightly underdetermine clouds at night and during times of low sun angle and tends to be cloud conservative during the day, particularly in the summertime. © 2008 IEEE."
"7005742394;24401083300;7005899086;","Factors determining the impact of aerosols on surface precipitation from clouds: An attempt at classification",2008,"10.1175/2007JAS2515.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45849113311&doi=10.1175%2f2007JAS2515.1&partnerID=40&md5=094d9993071021b186eaf83e335e184b","The simulation of the dynamics and the microphysics of clouds observed during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke, Aerosols, Clouds, Rainfall, and Climate (LBA-SMOCC) campaign, as well as extremely continental and extremely maritime clouds, is performed using an updated version of the Hebrew University spectral microphysics cloud model (HUCM). A new scheme of diffusional growth allows the reproduction of in situ-measured droplet size distributions including those formed in extremely polluted air. It was shown that pyroclouds forming over the forest fires can precipitate. Several mechanisms leading to formation of precipitation from pyroclouds are considered. The mechanisms by which aerosols affect the microphysics and precipitation of warm cloud-base clouds have been investigated by analyzing the mass, heat, and moisture budgets. The increase in aerosol concentration increases both the generation and the loss of the condensate mass. In the clouds developing in dry air, the increase in the loss is dominant, which suggests a decrease in the accumulated precipitation with the aerosol concentration increase. On the contrary, an increase in aerosol concentration in deep maritime clouds leads to an increase in precipitation. The precipitation efficiency of clouds in polluted air is found to be several times lower than that of clouds forming in clean air. A classification of the results of aerosol effects on precipitation from clouds of different types developing in the atmosphere with high freezing level (about 4 km) is proposed. The role of air humidity and other factors in precipitation's response to aerosols is discussed. The analysis shows that many discrepancies between the results reported in different observational and numerical studies can be attributed to the different atmospheric conditions and cloud types analyzed. © 2008 American Meteorological Society."
"6506152198;7403906746;7003605315;","Tropospheric new particle formation and the role of ions",2008,"10.1007/s11214-008-9388-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-49849096356&doi=10.1007%2fs11214-008-9388-2&partnerID=40&md5=e7365e713f72d6793f494f3251936cd2","Aerosol particles play an important role in the Earth's troposphere and in the climate system: They scatter and absorb solar radiation, facilitate chemical processes, and serve as condensation nuclei for the formation of clouds. Tropospheric aerosol particles are emitted from surface sources or form in situ from the gas phase. Formation from the gas phase requires concentrations of aerosol precursor molecules aggregating to form molecular clusters able to grow faster than they evaporate. This process is called nucleation. Gas phase ions can reduce the concentration of aerosol precursor molecules required for nucleation, as they greatly stabilize molecular clusters with respect to evaporation. Therefore, ions are a potential source of aerosol particles. Since atmospheric ionization carries the signal of the decadal solar cycle due to the modulation of the galactic cosmic ray intensity by solar activity, a possible connection between the solar cycle, galactic cosmic rays, aerosols, and clouds has been a long-standing focus of interest. In this paper, we provide an overview of theoretical, modeling, laboratory, and field work on the role and relevance of ions for the formation of tropospheric aerosol particles, and on subsequent effects on clouds, and discuss briefly related research needs. © 2008 Springer Science+Business Media B.V."
"24178410600;7005428121;7102284642;","Isolated breakdown activity in Swedish lightning",2008,"10.1016/j.jastp.2008.03.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44649149648&doi=10.1016%2fj.jastp.2008.03.003&partnerID=40&md5=d4848de8d2abf346bdc1c9a52ce27f93","The initial breakdown processes or preliminary breakdown (PB) processes are generally associated with either cloud or cloud-ground lightning flashes, and hence have been studied mainly in connection with those subsequent activities. However, it has been observed in the summer thunderstorms of Sweden that there are breakdown processes that may not culminate into any subsequent activity. As these processes do not lead to any subsequent activity, they have been termed as isolated breakdown activities. Such isolated breakdown activities involve microsecond-scale pulses with both initial polarities. Based on their polarities, breakdown processes are divided into two groups; the negative breakdown pulses that are similar to the breakdown pulses leading to negative return strokes in ground flashes and the positive breakdown pulses similar to the breakdown pulses generally leading to the cloud flashes. The occurrence of the two types of breakdown processes is found to vary from a thunderstorm day to the other. In the present study, the signatures of isolated breakdown activities have been analyzed and are compared with those leading to the subsequent activities observed during the same measurement campaign. The average duration of the isolated breakdown activity associated with the negative initial polarity pulses is found to be 0.98 ms with average number of pulses 8.5. Similarly, the average duration and number of pulses in the isolated breakdown process with positive initial polarity pulses are 6.9 ms and 3.9, respectively. © 2008 Elsevier Ltd. All rights reserved."
"24477979600;","Cloud forests",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-47949125300&partnerID=40&md5=3132e639302c17caf704f4c4b5a6d4e3","The Cusuco National Park located in north-west Honduras has a rare type of evergreen forest found in equatorial regions, enveloped with pure stands of pine. Its about 13km from east to west and around 8km north to south. The forest has steep terrain creating many different climate conditions in close proximity to one another. There are volunteers helped survey over 150 sites scattered across the park. These surveys will allow to determine the most efficient way of monitoring the park's state of health. It also gives information along with animal surveys, which factors are the most essential for each animal species. Because of these surveys, it is found that the forest have 39 species of dung beetles, 270 bird species, 35 bat species, and 93 species of reptiles and amphibians."
"7201837768;14829673100;56249704400;7201706787;15032788000;6603140753;7004214645;7006461606;","Aerosol climate effects and air quality impacts from 1980 to 2030",2008,"10.1088/1748-9326/3/2/024004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46749133626&doi=10.1088%2f1748-9326%2f3%2f2%2f024004&partnerID=40&md5=1a92417f14d38ea958960c5de373445f","We investigate aerosol effects on climate for 1980, 1995 (meant to reflect present day) and 2030 using the NASA Goddard Institute for Space Studies climate model coupled to an on-line aerosol source and transport model with interactive oxidant and aerosol chemistry. Aerosols simulated include sulfates, organic matter (OM), black carbon (BC), sea-salt and dust and, additionally, the amount of tropospheric ozone is calculated, allowing us to estimate both changes to air quality and climate for different time periods and emission amounts. We include both the direct aerosol effect and indirect aerosol effects for liquid-phase clouds. Future changes for the 2030 A1B scenario are examined, focusing on the Arctic and Asia, since changes are pronounced in these regions. Our results for the different time periods include both emission changes and physical climate changes. We find that the aerosol indirect effect (AIE) has a large impact on photochemical processing, decreasing ozone amount and ozone forcing, especially for the future (2030-1995). Ozone forcings increase from 0 to 0.12 W m -2 and the total aerosol forcing decreases from -0.10 to -0.94 W m-2 (AIE decreases from -0.13 to -0.68 W m-2) for 1995-1980 versus 2030-1995. Over the Arctic we find that compared to ozone and the direct aerosol effect, the AIE contributes the most to net radiative flux changes. The AIE, calculated for 1995-1980, is positive (1.0 W m-2), but the magnitude decreases (-0.3 W m-2) considerably for the future scenario. Over Asia, we evaluate the role of biofuel- and transportation-based emissions (for BC and OM) via a scenario (2030A) that includes a projected increase (factor of 2) in biofuel- and transport-based emissions for 2030 A1B over Asia. Projected changes from present day due to the 2030A emissions versus 2030 A1B are a factor of 4 decrease in summertime precipitation in Asia. Our results are sensitive to emissions used. Uncertainty in present-day emissions suggests that future climate projections warrant particular scrutiny. © IOP Publishing Ltd."
"57202477448;36107698500;","Satellite and ground observations for large-scale air pollution transport in the Yellow Sea region",2008,"10.1007/s10874-008-9111-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74149093542&doi=10.1007%2fs10874-008-9111-4&partnerID=40&md5=7e22b01f8aedc76cd60434d45a3a28a5","Large-scale air pollution transport (LSAPT) in the Yellow Sea region and their inflow onto the Korean Peninsula were observed through satellite images and ground measurements. LSAPT includes regional continental air-masses saturated with pollutants originating from China and subsequently landing on or passing through the Korean Peninsula. It is also possible to identify the distribution and transport patterns of LSAPT over the Yellow Sea. The ground concentrations for PM10, PM2.5 and CO measured at Cheongwon, located in the centre of south Korea, were compared with NOAA satellite images. Notably, the episodes observed of the LSAPT show a PM2.5 to PM10 ratio of 74% of the daily maximum concentrations. However, cases of duststorms were clearly distinguished by much higher PM10 concentrations and a ratio of 30% of PM2.5 to PM10 for daily maximum concentrations. For the episode on January 27, 2006, the inflow of a regionally polluted continental air-mass into the central and southwestern regions of the Korean Peninsula was observed sequentially at various ground observatories as well as by satellite. The north airflow dissipated the clouds over Mt. Halla on Jeju Island and further downwind, reducing air pollution and creating a von Kármán vortex. © 2008 Springer Science+Business Media B.V."
"57199843170;7003371432;","Satellite-derived aerosol radiative forcing from the 2004 British Columbia wildfires",2008,"10.3137/ao.460201","https://www.scopus.com/inward/record.uri?eid=2-s2.0-47249149696&doi=10.3137%2fao.460201&partnerID=40&md5=687ab2c20f34ed486c2997b019e74a5f","The British Columbia wildfires of 2004 was one of the largest wildfire events in the last ten years in Canada. Both the shortwave and longwave smoke aerosol radiative forcing at the top-of-atmosphere (TOA) are investigated using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth's Radiant Energy System (CERES) instruments. Relationships between the radiative forcing fluxes (ΔF) and wildfire aerosol optical thickness (AOT) at 0.55 μm (τ0.55) are deduced for both noontime instantaneous forcing and diurnally averaged forcing. The noontime averaged instantaneous shortwave and longwave smoke aerosol radiative forcing at the TOA are 45.8±27.5 W m-2 and -12.6±6.9 W m-2, respectively for a selected study area between 62°N and 68°N in latitude and 125°W and 145°W in longitude over three mainly clear-sky days (23-25 June). The derived diurnally averaged smoke aerosol shortwave radiative forcing is 19.9±12.1 W m-2 for a mean τ0.55 of 1.88±0.71 over the same time period. The derived ΔF-τ relationship can be implemented in the radiation scheme used in regional climate models to assess the effect of wildfire aerosols."
"25928347900;7006577245;6701754792;35551238800;","New approach to determine aerosol optical depth from combined CALIPSO and CloudSat ocean surface echoes",2008,"10.1029/2008GL033442","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049083112&doi=10.1029%2f2008GL033442&partnerID=40&md5=420cf2435530889bca8978b3b5409569","Backscatter lidar observations such as those provided by the CALIPSO mission are expected to give complementary information to long-used radiometric observations for aerosol properties characterization important to climate and environment issues. However, retrieving aerosol optical depth (AOD) and profiling the aerosol extinction cannot be done accurately applying a standard inversion procedure to the backscatter lidar measurements, without a precise knowledge of aerosol properties on the vertical. The objective of this first study is to propose a new approach to quantify the AOD over the ocean combining the surface return signals from the lidar and radar onboard the CALIPSO and CloudSat platforms, respectively. Taking advantage of the satellite formation within the AQUA-train, first comparisons of AODs retrieved with our method and MODIS ones at tropical latitudes show an overall bias smaller than 1%, and a standard deviation of about 0.07. These first results are presented and error sources are discussed. Copyright 2008 by the American Geophysical Union."
"7402548443;24335366400;22836686300;12544502800;8447628500;6602624109;6504688501;6505791231;7202191636;7003927831;6505595743;16555233400;6603604042;7004937718;56233900400;7006252528;15050707900;7003355879;7006532784;56283402900;6602889001;35376447600;8586435700;6701363731;7005829052;","Ozone trends at northern mid- and high latitudes &ndash; A European perspective",2008,"10.5194/angeo-26-1207-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44449142574&doi=10.5194%2fangeo-26-1207-2008&partnerID=40&md5=2302fca58016cab4686f7e92417ae70d","The EU CANDIDOZ project investigated the chemical and dynamical influences on decadal ozone trends focusing on the Northern Hemisphere. High quality long-term ozone data sets, satellite-based as well as ground-based, and the long-term meteorological reanalyses from ECMWF and NCEP are used together with advanced multiple regression models and atmospheric models to assess the relative roles of chemistry and transport in stratospheric ozone changes. This overall synthesis of the individual analyses in CANDIDOZ shows clearly one common feature in the NH mid latitudes and in the Arctic: an almost monotonic negative trend from the late 1970s to the mid 1990s followed by an increase. In most trend studies, the Equivalent Effective Stratospheric Chlorine (EESC) which peaked in 1997 as a consequence of the Montreal Protocol was observed to describe ozone loss better than a simple linear trend. Furthermore, all individual analyses point to changes in dynamical drivers, such as the residual circulation (responsible for the meridional transport of ozone into middle and high latitudes) playing a key role in the observed turnaround. The changes in ozone transport are associated with variations in polar chemical ozone loss via heterogeneous ozone chemistry on PSCs (polar stratospheric clouds). Synoptic scale processes as represented by the new equivalent latitude proxy, by conventional tropopause altitude or by 250 hPa geopotential height have also been successfully linked to the recent ozone increases in the lowermost stratosphere. These show significant regional variation with a large impact over Europe and seem to be linked to changes in tropospheric climate patterns such as the North Atlantic Oscillation. Some influence in recent ozone increases was also attributed to the rise in solar cycle number 23. Changes from the late 1970s to the mid 1990s were found in a number of characteristics of the Arctic vortex. However, only one trend was found when more recent years are also considered, namely the tendency for cold winters to become colder."
"35917252100;55574198423;","Parameterization of continental boundary layer clouds",2008,"10.1029/2007JD009315","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48749109597&doi=10.1029%2f2007JD009315&partnerID=40&md5=407974d576bf62f81adb0f69ad2da3a6","Large eddy simulations (LESs) of continental boundary layer clouds (BLCs) observed at the southern Great Plains (SGP) are used to study issues associated with the parameterization of sub-grid BLCs in large scale models. It is found that liquid water potential temperature θ<inf>l</inf> and total specific humidity q<inf>t</inf> which are often used as parameterization predictors in statistical cloud schemes, do not share the same probability distribution in the cloud layer with θ<inf>l</inf> skewed to the left (negatively skewed) and q<inf>t</inf> skewed to the right (positively skewed). The skewness and kurtosis change substantially in time and space when the development of continental BLCs undergoes a distinct diurnal variation. The wide range of skewness and kurtosis of θ<inf>l</inf> and q<inf>t</inf> can hardly be described by a single probability distribution function. To extend the application of the statistical cloud parameterization approach, this paper proposes an innovative cloud parameterization scheme that uses the boundary layer height and the lifting condensation level as the primary parameterization predictors. The LES results indicate that the probability distribution of these two quantities is relatively stable compared with that of θ<inf>l</inf> and q<inf>t</inf> during the diurnal variation and nearly follows a Gaussian function. Verifications using LES output and the observations collected at the Atmospheric Radiation Measurement (ARM) Climate Research Facility (ARCF) SGP site indicate that the proposed scheme works well to represent continental BLCs. Copyright 2008 by the American Geophysical Union."
"56158229700;7403664744;57214415369;6603611312;35461255500;11339750700;7004165697;7402049334;7404521962;","Observations of nighttime new particle formation in the troposphere",2008,"10.1029/2007JD009351","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48749116330&doi=10.1029%2f2007JD009351&partnerID=40&md5=d2d91f7a636e88d2a5ac60c93d463ca1","We present atmospheric observations which indicate efficient new particle formation during the nighttime in the troposphere under low condensation sinks, in contrast to the current prevailing assumption that aerosol nucleation takes place only during the daytime and typically from sulfinic acid. High concentrations of ultrafine particles with diameters from 4 to 9 nm (ℓ1000 cm-3) were measured from the three days of nighttime observations in the upper troposphere during the NSF/NCAR GV Progressive Science Missions. Long-term ground-based observations of charged and neutral clusters and aerosols made in Tumbarumba, Australia, also showed surprisingly high frequency of nighttime new particle formation (30%) with low condensation sinks. Nighttime nucleation can be significant for global aerosol load and cloud condensation nuclei productions and thus needs to be included in global climate models. Future studies are required to understand the nighttime nucleation mechanisms. Copyright 2008 by the American Geophysical Union."
"10139397300;7407104838;7102805852;7005135473;","Updated estimate of aerosol direct Radiative forcing from satellite observations and comparison against the centre climate model",2008,"10.1029/2007JD009385","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48749109059&doi=10.1029%2f2007JD009385&partnerID=40&md5=a5fea37addf5bf3f458b2a2d641f8df5","The fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC) includes a comparison of observation-based and modeling-based estimates of the aerosol direct radiative forcing. In this comparison, satellite-based studies suggest a more negative aerosol direct radiative forcing than modeling studies. A previous satellite-based study, part of the IPCC comparison, uses aerosol optical depths and accumulation-mode fractions retrieved by the Moderate Resolution Imaging Spectroradiometer (MODIS) at collection 4. The latest version of MODIS products, named collection 5, improves aerosol retrievals. Using these products, the direct forcing in the shortwave spectrum defined with respect to present-day natural aerosols is now estimated at -1.30 and -0.65 Wm-2 on a global clear-sky and all-sky average, respectively, for 2002. These values are still significantly more negative than the numbers reported by modeling studies. By accounting for differences between present-day natural and preindustrial aerosol concentrations, sampling biases, and investigating the impact of differences in the zonal distribution of anthropogenic aerosols, good agreement is reached between the direct forcing derived from MODIS and the Hadley Centre climate model HadGEM2-A over clear-sky oceans. Results also suggest that satellite estimates of anthropogenic aerosol optical depth over land should be coupled with a robust validation strategy in order to refine the observation-based estimate of aerosol direct radiative forcing. In addition, the complex problem of deriving the aerosol direct radiative forcing when aerosols are located above cloud still needs to be addressed."
"55414609600;7401795483;","Seasonal variation of cloud activity and atmospheric profiles over the eastern part of the Tibetan Plateau",2008,"10.1029/2007JD009321","https://www.scopus.com/inward/record.uri?eid=2-s2.0-47749146098&doi=10.1029%2f2007JD009321&partnerID=40&md5=c87aeb678d67fb4545853fed22327db3","Cumulus activity over the Tibetan Plateau has a clear pattern of seasonal progression. Activity occurs with significant frequency in the eastern part of the plateau from April to mid-May. From mid-May to mid-June the frequency of cumulus activity drastically decreases and then increases after mid-June. Causes of such definite seasonal progression are revealed by in situ radiosonde observation data. In early spring the vertical profile of potential temperature is almost uniform from the surface to 7000 m above sea level around noon, and atmospheric stratification is vertically neutral for dry convection. Under such a condition, dry convection easily occurs and develops cumulus cloud that is frequently observed. From mid-May to mid-June the atmosphere has conditionally unstable stratification, but the atmosphere is relatively dry and hardly saturated and cumulus activity occurs less frequently. Though the atmosphere is also conditionally unstable after mid-June, the increase in total precipitable water content allows easy atmospheric saturation and cumulus activity recommences. At the same time, satellite data and reanalysis data show, in the eastern part of the Tibetan Plateau, a consistent correspondence of the seasonal variation of cumulus activity, total precipitable water content, and vertical instability of the atmosphere. Results of synoptic-scale analysis indicate the enhancement of cumulus convection in the northern part of India and the Tibetan High cause a moisture increase over the Tibetan Plateau and leads to the recommencement of frequent cumulus activity over the plateau. Copyright 2008 by the American Geophysical Union."
"23065650200;7006705919;7004586655;7004242319;7004999694;","Impact of small ice crystal assumptions on ice sedimentation rates in cirrus clouds and GCM simulations",2008,"10.1029/2008GL033552","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48549101769&doi=10.1029%2f2008GL033552&partnerID=40&md5=8871eb79825be13634702449119410d0","In the prediction of climate change, the greatest uncertainty lies in the representation of clouds. Ice clouds are particularly challenging, and to date there is no accepted method for measuring the smaller ice crystals (D &lt; 60 μm). This study examines the sensitivity of a global climate model to different assumptions regarding the number concentrations of small ice crystals when they are allowed to affect ice sedimentation rates. When their concentrations are relatively high, the GCM predicts a 12% increase in cloud ice amount and a 5.5% increase in cirrus cloud coverage globally. This produces a net cloud forcing of -5 W m-2 in the tropics and warms the upper tropical troposphere over 3°C. Ice crystal concentration differences assumed were modest in comparison to corresponding measurement uncertainties, revealing a potentially large source of uncertainty in the prediction of global climate. Copyright 2008 by the American Geophysical Union."
"7401501923;7201634460;8578246200;55575353100;","Assessing the consistency of AVHRR and MODIS L1B reflectance for generating Fundamental Climate Data Records",2008,"10.1029/2007JD009363","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46449132587&doi=10.1029%2f2007JD009363&partnerID=40&md5=0a95282043a5278a0960c298f2e29ac2","Satellite detection of the global climate change signals as small as a few percent per decade in albedo critically depends on consistent and accurately calibrated Level 1B (L1B) data or Fundamental Climate Data Records (FCDRs). Detecting small changes in signal over decades is a major challenge not only to the retrieval of geophysical parameters from satellite observations, but more importantly to the current state-of-the-art calibration, since such small changes can easily be obscured by erroneous variations in the calibration, especially for instruments with no onboard calibration, such as the Advanced Very High Resolution Radiometer (AVHRR). Without dependable FCDRs, its derivative Thematic Climate Data Records (TCDRs) are bound to produce false trends with questionable scientific value. This has been increasingly recognized by more and more remote sensing scientists. In this study we analyzed the consistency of calibrated reflectance from the operational LIB data between AVHRR on NOAA-16 and -17 and between NOAA-16/AVHRR and Aqua/MODIS, based on Simultaneous Nadir Overpass (SNO) observation time series. Analyses suggest that the NOAA-16 and -17/AVHRR operationally calibrated reflectance became consistent two years after the launch of NOAA-17, although they still differ by 9% from the MODIS reflectance for the 0.63 μm band. This study also suggests that the SNO method has reached a high level of relative accuracy (∼1.5%) for estimating the consistency for both the 0.63 and 0.84 μm bands between AVHRRs, and a 0.9% relative accuracy between AVHRR and MODIS for the 0.63 μm band. It is believed that the methodology is applicable to all historical AVHRR data for improving the calibration consistency, and work is in progress generating FCDRs from the nearly 30 years of AVHRR data using the SNO and other complimentary methods. A more consistent historical AVHRR L1B data set will be produced for a variety of geophysical products including aerosol, vegetation, cloud, and surface albedo to support global climate change detection studies. Copyright 2008 by the American Geophysical Union."
"15135280400;15122248200;7004723203;","Impact of extreme CO2 levels on tropical climate: A CGCM study",2008,"10.1007/s00382-008-0414-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-54949096958&doi=10.1007%2fs00382-008-0414-6&partnerID=40&md5=2abf47087133dabda11f7e93c51545cb","A coupled general circulation model has been used to perform a set of experiments with high CO2 concentration (2, 4, 16 times the present day mean value). The experiments have been analyzed to study the response of the climate system to strong radiative forcing in terms of the processes involved in the adjustment at the ocean-atmosphere interface. The analysis of the experiments revealed a non-linear response of the mean state of the atmosphere and ocean to the increase in the carbon dioxide concentration. In the 16 × CO2 experiment the equilibrium at the ocean-atmosphere interface is characterized by an atmosphere with a shut off of the convective precipitation in the tropical Pacific sector, associated with air warmer than the ocean below. A cloud feedback mechanism is found to be involved in the increased stability of the troposphere. In this more stable condition the mean total precipitation is mainly due to large-scale moisture flux even in the tropics. In the equatorial Pacific Ocean the zonal temperature gradient of both surface and sub-surface waters is significantly smaller in the 16 × CO2 experiment than in the control experiment. The thermocline slope and the zonal wind stress decrease as well. When the CO2 concentration increases by about two and four times with respect to the control experiment there is an intensification of El Niño. On the other hand, in the experiment with 16 times the present-day value of CO2, the Tropical Pacific variability weakens, suggesting the possibility of the establishment of permanent warm conditions that look like the peak of El Niño. © Springer-Verlag Berlin Heidelberg 2008."
"6701455548;7005513582;7201520140;","Using the radiative kernel technique to calculate climate feedbacks in NCAR's Community Atmospheric Model",2008,"10.1175/2007JCLI2044.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45349091207&doi=10.1175%2f2007JCLI2044.1&partnerID=40&md5=a7f338048abede99cfa5048eb5ca5475","Climate models differ in their responses to imposed forcings, such as increased greenhouse gas concentrations, due to different climate feedback strengths. Feedbacks in NCAR's Community Atmospheric Model (CAM) are separated into two components: the change in climate components in response to an imposed forcing and the ""radiative kernel,"" the effect that climate changes have on the top-of-the-atmosphere (TOA) radiative budget. This technique's usefulness depends on the linearity of the feedback processes. For the case of CO2 doubling, the sum of the effects of water vapor, temperature, and surface albedo changes on the TOA clear-sky flux is similar to the clear-sky flux changes directly calculated by CAM. When monthly averages are used rather than values from every time step. the global-average TOA shortwave change is underestimated by a quarter, partially as a result of intramonth correlations of surface albedo with the radiative kernel. The TOA longwave flux changes do not depend on the averaging period. The longwave zonal averages are within 10% of the model-calculated values, while the global average differs by only 2%. Cloud radiative forcing (ΔCRF) is often used as a diagnostic of cloud feedback strength. The net effect of the water vapor, temperature, and surface albedo changes on ΔCRF is -1.6 W m-2 , based on the kernel technique, While the total ΔCRF from CAM is -1.3 W m-2, indicating these components contribute significantly to ΔCRF and make it more negative. Assuming linearity of the ΔCRF contributions, these results indicate that the net cloud feedback in CAM is positive. © 2008 American Meteorological Society."
"6507078612;8609629400;6602511330;7103332704;23488276300;7102265802;23487783100;","Evaluation of the onset of green-up in temperate deciduous broadleaf forests derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data",2008,"10.1016/j.rse.2007.12.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41449115901&doi=10.1016%2fj.rse.2007.12.004&partnerID=40&md5=504dc15ff5fe080c7e7b8658da2dfc54","Vegetation phenology is the chronology of periodic phases of development. It constitutes an efficient bio-indicator of impacts of climate changes and a key parameter for understanding and modelling vegetation-climate interactions and their implications on carbon cycling. Numerous studies were devoted to the remote sensing of vegetation phenology. Most of these were carried out using data acquired by AVHRR instrument onboard NOAA meteorological satellites. Since 1999, multispectral images were acquired over the whole earth surface every one to two days by MODIS instrument onboard Terra and Aqua platforms. In comparison with AVHRR, MODIS constitutes a significant technical improvement in terms of spatial resolution, spectral resolution, geolocation accuracy, atmospheric corrections scheme and cloud screening and sensor calibration. In this study, 250 m daily MODIS data were used to derive precise vegetation phenological dates over deciduous forest stands. Phenological markers derived from MODIS time-series and provided by MODIS Global Land Cover Dynamics product (MOD12Q2) were compared to field measurements carried out over the main deciduous forest stands across France and over five years. We show that the inflexion point of the asymmetric double-sigmoid function fitted to NDVI temporal profile is a good marker of the onset of green-up in deciduous stands. At plot level, the prediction uncertainty is 8.5 days and the bias is 3.5 days. MODIS Global Land Cover Dynamics MOD12Q2 provides estimates of onset of green-up dates which deviate substantially from in situ observations and do not perform better than the null model. RMSE values are 20.5 days (bias -17 days) using the onset of greenness increase and 36.5 days (bias 34.5 days) using the onset of greenness maximum. An improvement of prediction quality is obtained if we consider the average of MOD12Q2 onset of greenness increase and maximum as marker of onset of green-up date. RMSE decreases to 16.5 days and bias to 7.5 days. © 2008 Elsevier Inc. All rights reserved."
"6602098362;7005578774;","The annual cycle of the energy budget. Part I: Global mean and land-ocean exchanges",2008,"10.1175/2007JCLI1935.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45349103866&doi=10.1175%2f2007JCLI1935.1&partnerID=40&md5=e7c66df93d1e240685eb1e07d6fb3401","The mean and annual cycle of energy flowing into the climate system and its storage, release, and transport in the atmosphere, ocean, and land surface are estimated with recent observations. An emphasis is placed on establishing internally consistent quantitative estimates with discussion and assessment of uncertainty. At the top of the atmosphere (TOA), adjusted radiances from the Earth Radiation Budget Experiment (ERBE) and Clouds and the Earth's Radiant Energy System (CERES) are used, while in the atmosphere the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis and 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) estimates are used. The net upward surface flux (Fs) over ocean is derived as the residual of the TOA and atmospheric energy budgets, and is compared with direct calculations of ocean heat content (OE) and its tendency (δOE/δt) from several ocean temperature datasets. Over land, Fs from a stand-alone simulation of the Community Land Model forced by observed fields is used. A depiction of the full energy budget based on ERBE fluxes from 1985 to 1989 and CERES fluxes from 2000 to 2004 is constructed that matches estimates of the global, global ocean, and global land imbalances. In addition, the annual cycle of the energy budget during both periods is examined and compared with ocean heat content changes. The near balance between the net TOA radiation (RT) and Fs over ocean and thus with OE, and between RT and atmospheric total energy divergence over land, are documented both in the mean and for the annual cycle. However, there is an annual mean transport of energy by the atmosphere from ocean to land regions of 2.2 ± 0.1 PW (1 PW = 1015 W) primarily in the northern winter when the transport exceeds 5 PW. The global albedo is dominated by a semiannual cycle over the ooeans, but combines with the large annual cycle in solar insulation to produce a peak in absorbed solar and net radiation in February, somewhat after the perihelion, and with the net radiation 4.3 PW higher than the annual mean, as it is enhanced by the annual cycle of outgoing longwave radiation that is dominated by land regions. In situ estimates of the annual variation of OE are found to be unrealistically large. Challenges in diagnosing the interannual variability in the energy budget and its relationship to climate change are identified in the context of the episodic and inconsistent nature of the observations. © 2008 American Meteorological Society."
"6602098362;7005578774;","The annual cycle of the energy budget. Part II: Meridional structures and poleward transports",2008,"10.1175/2007JCLI1936.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45349103587&doi=10.1175%2f2007JCLI1936.1&partnerID=40&md5=56a1bea699c420e388295fdb16e99282","Meridional structure and transports of energy in the atmosphere, ocean, and land are evaluated holistically for the mean and annual cycle zonal averages over the ocean, land, and global domains, with discussion and assessment of uncertainty. At the top of the atmosphere (TOA), adjusted radiances from the Earth Radiation Budget Experiment (ERBE) and Clouds and Earth's Radiant Energy System (CERES) are used along with estimates of energy storage and transport from two global reanalysis datasets for the atmosphere. Three ocean temperature datasets are used to assess changes in the ocean heat content (OE) and their relationship to the net upward surface energy flux over ocean (Fs o), which is derived from the residual of the TOA and atmospheric energy budgets. The surface flux over land is from a stand-alone simulation of the Community Land Model forced by observed fields. In the extratropics, absorbed solar radiation (ASR) achieves a maximum in summer with peak values near the solstices. Outgoing longwave radiation (OLR) maxima also occur in summer but lag ASR by 1-2 months, consistent with temperature maxima over land. In the tropics, however, OLR relates to high cloud variations and peaks late in the dry monsoon season, while the OLR minima in summer coincide with deep convection in the monsoon trough at the height of the rainy season. Most of the difference between the TOA radiation and atmospheric energy storage tendency is made up by a large heat flux into the ocean in summer and out of the ocean in winter. In the Northern Hemisphere, the transport of energy from ocean to land regions is substantial in winter, and modest in summer. In the Southern Hemisphere extratropics, land - ocean differences play only a small role and the main energy transport by the atmosphere and ocean is poleward. There is reasonably good agreement between Fso and observed changes in OE, except for south of 40°S, where differences among several ocean datasets point to that region as the main source of errors in achieving an overall energy balance. The winter hemisphere atmospheric circulation is the dominant contributor to poleward energy transports outside of the tropics [6-7 PW (1 petawatt = 1015 W)], with summer transports being relatively weak (∼3 PW) - slightly more in the Southern Hemisphere and slightly less in the Northern Hemisphere. Ocean transports outside of the tropics are found to be small (&lt;2 PW) for all months. Strong cross-equatorial heat transports in the ocean of up to 5 PW exhibit a large annual cycle in phase with poleward atmospheric transports of the winter hemisphere. © 2008 American Meteorological Society."
"26428503000;6603286088;23767761300;12766055000;7004418509;","A systematic method for 3D mapping of mangrove forests based on Shuttle Radar Topography Mission elevation data, ICEsat/GLAS waveforms and field data: Application to Ciénaga Grande de Santa Marta, Colombia",2008,"10.1016/j.rse.2007.10.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41249097079&doi=10.1016%2fj.rse.2007.10.012&partnerID=40&md5=cb17f417474f8656f9177bdf8c589559","Mangrove forests are found within the intertropical zone and are one of the most biodiverse and productive wetlands on Earth. We focus on the Ciénaga Grande de Santa Marta (CGSM) in Colombia, the largest coastal lagoon-delta ecosystem in the Caribbean area with an extension of 1280 km2, where one of the largest mangrove rehabilitation projects in Latin America is currently underway. Extensive man-made hydrological modifications in the region caused hypersaline soil (&gt; 90 g kg- 1) conditions since the 1960s triggering a large dieback of mangrove wetlands (~ 247 km2). In this paper, we describe a new systematic methodology to measure mangrove height and aboveground biomass by remote sensing. The method is based on SRTM (Shuttle Radar Topography Mission) elevation data, ICEsat/GLAS waveforms (Ice, Cloud, and Land Elevation Satellite/Geoscience Laser Altimeter System) and field data. Since the locations of the ICEsat and field datasets do not coincide, they are used independently to calibrate SRTM elevation and produce a map of mangrove canopy height. We compared height estimation methods based on waveform centroids and the canopy height profile (CHP). Linear relationships between ICEsat height estimates and SRTM elevation were derived. We found the centroid of the canopy waveform contribution (CWC) to be the best height estimator. The field data was used to estimate a SRTM canopy height bias (- 1.3 m) and estimation error (rms = 1.9 m). The relationship was applied to the SRTM elevation data to produce a mangrove canopy height map. Finally, we used field data and published allometric equations to derive an empirical relationship between canopy height and biomass. This relationship was used to scale the mangrove height map and estimate aboveground biomass distribution for the entire CGSM. The mean mangrove canopy height in CGSM is 7.7 m and most of the biomass is concentrated in forests around 9 m in height. Our biomass maps will enable estimation of regeneration rates of mangrove forests under hydrological rehabilitation at large spatial scales over the next decades. They will also be used to assess how highly disturbed mangrove forests respond to increasing sea level rise under current global climate change scenarios. © 2008 Elsevier Inc."
"35615735500;7005202019;7202364010;","Relationship between downwelling surface shortwave radiative fluxes and sea surface temperature over the tropical Pacific: AMIP II models versus satellite estimates",2008,"10.5194/angeo-26-785-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43949087207&doi=10.5194%2fangeo-26-785-2008&partnerID=40&md5=ba7c5420d2f0e44963df7ba1e8795a92","Incident shortwave radiation at the Earth's surface is the driving force of the climate system. Understanding the relationship between this forcing and the sea surface temperature, in particular, over the tropical Pacific Ocean is a topic of great interest because of possible climatic implications. The objective of this study is to investigate the relationship between downwelling shortwave radiative fluxes and sea surface temperature by using available data on radiative fluxes. We assess first the shortwave radiation from three General Circulation Models that participated in the second phase of the Atmospheric Model Intercomparison Project (AMIP II) against estimates of such fluxes from satellites. The shortwave radiation estimated from the satellite is based on observations from the International Satellite Cloud Climatology Project D1 data and the University of Maryland Shortwave Radiation Budget model (UMD/SRB). Model and satellite estimates of surface radiative fluxes are found to be in best agreement in the central equatorial Pacific, according to mean climatology and spatial correlations. We apply a Canonical Correlation Analysis to determine the interrelated areas where shortwave fluxes and sea surface temperature are most sensitive to climate forcing. Model simulations and satellite estimates of shortwave fluxes both capture well the interannual signal of El Ni ±o-like variability. The tendency for an increase in shortwave radiation from the UMD/SRB model is not captured by the AMIP II models."
"6701419565;","Range of application of the scattering theory within the multicomponent turbid media of the cloud atmosphere is the reason for anomalous absorption and incorrectness of climate prediction",2008,"10.1080/01431160701767443","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43549123552&doi=10.1080%2f01431160701767443&partnerID=40&md5=699b7fae0d9832f39fd851f214ba9bb3","Contemporary climatic models predicting different scenarios of climate formation are examined and educated on examples of known parameters of the climatic system of the last century. The atmospheric aerosols' impact is taken into account as adjusting factor. The cloud influence on increasing absorption of the solar radiation in the atmosphere ('anomalous absorption' in the short wavelength ranges) is not considered in the climatic simulations. Observations of the shortwave solar radiation in the Earth's atmosphere demonstrate increasing radiation absorption under cloudy conditions compared with the clear atmosphere. The difference between the spectral dependence of the cloud optical thickness together with the value of the single scattering albedo, retrieved from airborne, satellite and ground-based radiation observations, and results of model calculations with applying scattering theory is revealed. A possible physical explanation is proposed in this paper. An incorrect account of the absorption of solar radiation in the cloudy atmosphere during the process of refining a climatic model attaches too much weight of the greenhouse gases yield on atmospheric energy balance in simulation. As a result, the influence of greenhouse gases on formation of the temperature field appears overestimated."
"6507817959;6603761049;","Greenhouse gases and future long-term changes in the stratospheric temperature and the ozone layer",2008,"10.1080/01431160701767583","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43549119322&doi=10.1080%2f01431160701767583&partnerID=40&md5=9e7a669ebfc803b169aacc796da2fe72","A numerical two-dimensional (2D) interactive dynamical-radiative-photochemical model including aerosol physics is used to examine the expected long-term changes in stratospheric temperature and the Earth's ozone layer due to anthropogenic pollution of the atmosphere by the greenhouse gases CO2, CH4 and N2O. The model time-dependent runs were made for the period from 1975 to 2050. The results of the calculations show that the basic mechanism by which greenhouse gases influence the ozone layer is stratospheric cooling accompanied by a weakness in the efficiency of the catalytic cycles of ozone destruction due to temperature dependencies of the photochemical gas-phase reactions. Modification of polar stratospheric clouds (PSCs) caused by anthropogenic growth of the greenhouse gases is important only for the polar ozone. An essential influence of the greenhouse gases on the ozone by a modification of the stratospheric sulphate aerosol is revealed. The aerosol changes caused by the greenhouse gases modify the distribution of the ozone-active gaseous chlorine, bromine and nitrogen components by means of heterogeneous reactions on the aerosol surface, resulting in a significant decrease in springtime polar ozone depletion of the Antarctic ozone hole."
"6506709167;7005233189;","Tropospheric aerosol forcing of climate: A case study for the greater area of Greece",2008,"10.1080/01431160701767575","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43549123551&doi=10.1080%2f01431160701767575&partnerID=40&md5=51d17e56ece453f88b2b49629e767beb","Although greenhouse gas forcing has global significance, the aerosol forcing is regional and seasonal, associated with the much shorter aerosol residence times in the atmosphere, and could become dominant on a regional scale. Several studies indicate that aerosol radiative forcing is among the highest in the world over the Mediterranean in the summer. In this study, the aerosol impact (forcing) on the short-wave and long-wave fluxes, as well as the radiative heating rate due to aerosols for different altitudes in the atmosphere over Athens, Greece, was estimated using satellite data and SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model. The short-wave aerosols radiative forcing at the surface in cloud-free conditions during the period 2000-2001 ranged from 10.8 to 20.1 W m-2 in the winter and from 15.2 to 16.6 W m-2 in the summer. The radiative heating rates near the surface due to aerosols were found to be in the range of 0.2-0.5 K day-1 during the winter period and 0.4 K day-1 during the summer period simultaneous with enhanced heating in the lower troposphere (below 5 km). The long-wave radiative forcing (clear sky) at the top of the atmosphere induced by aerosols during night-time was estimated to be only 0.02-0.04 W m-2 and 0.04-0.05 W m-2 for the winter and summer months, respectively."
"55502994400;6602390932;23011244600;8351732300;7004459129;","Dependence of cloud properties derived from spectrally resolved visible satellite observations on surface temperature",2008,"10.5194/acp-8-2299-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43749091749&doi=10.5194%2facp-8-2299-2008&partnerID=40&md5=77c3b3505f8f9209c30d2360118f011d","Cloud climate feedback constitutes the most important uncertainty in climate modelling, and currently even its sign is still unknown. In the recently published report of the intergovernmental panel on climate change (IPCC), 6 out of 20 climate models showed a positive and 14 a negative cloud radiative feedback in a doubled CO2 scenario. The radiative budget of clouds has also been investigated by experimental methods, especially by studying the relation of satellite observed broad band shortwave and longwave radiation to sea surface temperature. Here we present a new method for the investigation of the dependence of cloud properties on temperature changes, derived from spectrally resolved satellite observations in the visible spectral range. Our study differs from previous investigations in three important ways: first, we directly extract cloud properties (effective cloud fraction and effective cloud top height) and relate them to surface temperature. Second, we retrieve the cloud altitude from the atmospheric O2 absorption instead from thermal IR radiation. Third, our correlation analysis is performed using 7.5 years of global monthly anomalies (with respect to the average of the same month for all years). For most parts of the globe (except the tropics) we find a negative correlation of effective cloud fraction versus surface-near temperature. In contrast, for the effective cloud top height a positive correlation is found for almost the whole globe. Both findings might serve as an indicator for an overall positive cloud radiative feedback. Another peculiarity of our study is that the cloud-temperature relationships are determined for fixed locations (instead to spatial variations over selected areas) and are based on the ""natural"" variability over several years (instead the anomaly for a strong El-Nino event). From a detailed comparison to cloud properties from the International Satellite Cloud Climatology Project (ISCCP), in general good agreement is found. However, also systematic differences occurred indicating that our results provide independent and complementary information on cloud properties. Climate models should thus aim to reproduce our findings. Recommendations for the development of a ""processor"" to convert model results into the cloud sensitive quantities observed by the satellite are given."
"7005441447;16315767700;6701849060;55665325500;7101808591;16403028400;","Arctic Ocean gravity field derived from ICESat and ERS-2 altimetry: Tectonic implications",2008,"10.1029/2007JB005217","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55349134201&doi=10.1029%2f2007JB005217&partnerID=40&md5=0c58f87c84c633a5be8178c9836db3b3","A new, detailed marine gravity field for the persistently ice-covered Arctic Ocean, derived entirely from satellite data, reveals important new tectonic features in both the Amerasian and Eurasian basins. Reprocessed Geoscience Laser Altimeter System (GLAS) data collected by NASA's Ice Cloud and land Elevation Satellite (ICESat) between 2003 and 2005 have been combined with 8 years worth of retracked radar altimeter data from ESA's ERS-2 satellite to produce the highest available resolution gravity mapping of the entire Arctic Ocean complete to 86°N. This ARCtic Satellite-only (ARCS) marine gravity field uniformly and confidently resolves marine gravity to wavelengths as short as 35 km. ARCS relies on a Gravity Recovery and Climate Experiment (GRACE)-only satellite gravity model at long (>580 km) wavelengths and plainly shows tectonic fabric and numerous details imprinted in the Arctic seafloor, in particular, in the enigmatic Amerasian Basin (AB). For example, in the Makarov Basin portion of the AB, two north-south trending lineations are likely clues to the highly uncertain seafloor spreading history which formed the AB. Copyright 2008 by the American Geophysical Union."
"12139043600;56250250300;12139310900;6506436908;13403622000;7005955015;","Aerosol-cloud-climate interactions in the climate model CAM-Oslo",2008,"10.1111/j.1600-0870.2008.00313.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42549159929&doi=10.1111%2fj.1600-0870.2008.00313.x&partnerID=40&md5=80a7740f3a046d44a684e9d1555402ee","A new aerosol module is integrated on-line in the atmospheric GCM CAM-Oslo coupled to a slab ocean for equilibrium climate response studies. The response to an anthropogenic change in aerosols since pre-industrial times is compared with that of a future 63% increased CO2 level. The aerosol module calculates concentrations of sea-salt, mineral dust, sulphate, black carbon (BC) and particulate organic matter (POM). Look-up tables, constructed from first principles, are used to obtain optical parameters and cloud droplet numbers (CDNC) for any given aerosol composition. Anthropogenic aerosols thus produce a global near-surface cooling of 1.94 K and a 5.5% precipitation decrease, including amplifications by positive cloud feedbacks. In comparison, the CO2 increase gives a warming of 1.98 K and a 3.8% precipitation increase, causing slightly reduced sulphate, BC, POM and sea-salt burdens. A minor increase in mineral dust is ascribed to reduced subtropical precipitation downwind of Sahara over the Atlantic Ocean. The modelled indirect effects are probably overestimated, mainly due to neglected natural aerosol components and the diagnostic scheme for CDNC. Adding 15 cm-3 to CDNC everywhere reduces the indirect forcing from -2.34 to -1.36 Wm-2, whilst solving a prognostic equation for CDNC reduces it from -2.34 to -1.44 Wm-2. © 2008 The Authors Journal compilation © 2008 Blackwell Munksgaard."
"7006016266;55605771904;6602336407;7102959401;","Testing climate models using thermal infrared spectra",2008,"10.1175/2007JCLI2061.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45249089713&doi=10.1175%2f2007JCLI2061.1&partnerID=40&md5=d1c05d91fa368750cb6c2446b1259faa","An approach to test climate models with observations is presented. In this approach, it is possible to directly observe the longwave feedbacks of the climate system in time series of annual average outgoing longwave spectra. Tropospheric temperature, stratospheric temperature, water vapor, and carbon dioxide have clear and distinctive signatures in the infrared spectrum, and it is possible to detect trends of these signals unambiguously from trends in the outgoing longwave spectrum by optimal detection techniques. This approach is applied to clear-sky data in the tropics simulated from the output of an ensemble of climate models. Estimates of the water vapor-longwave feedback by this approach agree to within estimated errors with truth, and it is likely that an uncertainty of 50% can be obtained in 20 yr of a continuous time series. The correlation of tropospheric temperature and water vapor anomalies can provide a constraint on the water vapor-longwave feedback to 5% uncertainty in 20 yr, or 7% in 10 yr. Thus, it should be possible to place a strong constraint on climate models, which currently show a range of 30% in the water vapor-longwave feedback, in just 10 yr. These results may not hold in the presence of clouds, however, and so it may be necessary to supplement time series of outgoing longwave spectra with GPS radio occultation data, which are insensitive to clouds. © 2008 American Meteorological Society."
"55511340100;9271448600;7402590526;","Characteristics of climate change in the ""significant impact zone"" affected by aerosols over eastern China in warm seasons",2008,"10.1007/s11430-008-0044-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42549168640&doi=10.1007%2fs11430-008-0044-1&partnerID=40&md5=f3dfd3e6fc3641e7d838b0ea14d2061d","Through analysis of the distribution pattern and changing characteristics of atmospheric aerosols over the East Asia region during warm seasons in recent 20 a and beyond as well as their possible interactive relationship with a variety of meteorological elements, it is found that the high-value zone of aerosol optical depth derived from the Total Ozone Mapping Spectrometer (TOMS), its significant negative correlation zones in terms of sunshine duration (SD) and surface air temperature (SAT) and its significant positive correlation zones with low-level cloud amount (LCC) are co-located in the South China region during warm periods. Based on this finding, the region is referred to as a ""significant impact zone"" (SI zone) affected by aerosols. Then, a comparative analysis is made on variation differences of observed SAT, SD and LCC, etc. in different regions. It is also found that the LCC is increased and the SD is decreased within the ""SI zone"" over eastern China during the warm season. These characteristics are more evident than those beyond the zone, while the warming trend within the zone is evidently weaker than that outside it. Studies show that since recent 20 a, under the influence of aerosols, the LCC tend to increase substantially with a clear decrease of SD and an unnoticeable warming trend within the ""SI zone"". Comparing with the climate change beyond the zone, the difference is significant. Therefore, the effects of atmospheric aerosols on climate is possibly one of the contributions to the difference of climate change existed between the southern and northern parts of the Eastern China during a warm season. © Science in China 2008."
"12139310900;56250250300;12139043600;13403622000;","Aerosol-climate interactions in the CAM-Oslo atmospheric GCM and investigation of associated basic shortcomings",2008,"10.1111/j.1600-0870.2008.00318.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42549139340&doi=10.1111%2fj.1600-0870.2008.00318.x&partnerID=40&md5=b0e439ac75ec38bede645cd7c6172dc5","The paper discusses some challenges in aerosol-climate modelling. CAM-Oslo, extended from NCAR-CAM3, employs an aerosol module for sea-salt, dust, sulphate, black carbon (BC) and particulate organic matter (OM). Primary aerosol size-distributions are modified by condensation, coagulation and wet-phase processes. Aerosol optics and cloud droplet numbers use look-up tables constructed from first principles. Ground level sulphate and sea-salt are generally well modelled, BC and OM are slightly underestimated (uncertain), and dust is considerably (factor ∼2) underestimated. Since non-desert dust, nitrate, anthropogenic secondary organics, and biological particles are omitted, aerosol optical depths (0.12) are underestimated by 10-25%. The underestimates are large in areas with biomass burning and soil dust. The direct and indirect forcing of aerosol increments since pre-industrial time are estimated at +0.031 Wm-2 and -1.78 Wm-2, respectively. Although the total absorption AOD probably is slightly underestimated, the BC contributes to DRF with double strength compared to the AeroCom average. Main reasons for this include: internal BC-mixing (+0.2 Wm-2), accumulation mode BC-agglomerates (+0.05 Wm-2), assumed aitken-mode OM-BC mixture (+0.1 Wm-2), large BC fraction (36%) above 500hPa, and high low-level cloudiness. Using a prognostic CDNC and process parametrized CCN activation instead of assuming CDNC are equal to CCN, the indirect forcing is 36% smaller. © 2008 The Authors Journal compilation © 2008 Blackwell Munksgaard."
"7004037177;35551120200;6603324654;","A second generation climate index for tourism (CIT): Specification and verification",2008,"10.1007/s00484-007-0134-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42149089204&doi=10.1007%2fs00484-007-0134-3&partnerID=40&md5=dc97931408aaf34322db8cabd510b5aa","Climate is a key resource for many types of tourism and as such can be measured and evaluated. An index approach is required for this task because of the multifaceted nature of weather and the complex ways that weather variables come together to give meaning to climate for tourism. Here we address the deficiencies of past indices by devising a theoretically sound and empirically tested method that integrates the various facets of climate and weather into a single index called the Climate Index for Tourism (CIT). CIT rates the climate resource for activities that are highly climate/weather sensitive, specifically, beach ""sun, sea and sand"" (3S) holidays. CIT integrates thermal (T), aesthetic (A) and physical (P) facets of weather, which are combined in a weather typology matrix to determine a climate satisfaction rating that ranges from very poor (1 = unacceptable) to very good (7 = optimal). Parameter A refers to sky condition and P to rain or high wind. T is the body-atmosphere energy balance that integrates the environmental and physiological thermal variables, such as solar heat load, heat loss by convection (wind) and by evaporation (sweating), longwave radiation exchange and metabolic heat (activity level). Rather than use T as a net energy (calorific) value, CIT requires that it be expressed as thermal sensation using the standard nine-point ASHRAE scale (""very hot"" to ""very cold""). In this way, any of the several body-atmosphere energy balance schemes available may be used, maximizing the flexibility of the index. A survey (N∈=∈331) was used to validate the initial CIT. Respondents were asked to rate nine thermal states (T) with different sky conditions (A). They were also asked to assess the impact of high winds or prolonged rain on the perceived quality of the overall weather condition. The data was analysed statistically to complete the weather typology matrix, which covered every possible combination of T, A and P. Conditions considered to be optimal (CIT class 6-7) for 3S tourism were those that were ""slightly warm"" with clear skies or scattered cloud (25% cloud). Acceptable conditions (CIT∈=∈4-5) fell within the thermal range ""indifferent"" to ""hot"" even when the sky was overcast. Wind equal to or in excess of 6 m/s (22 km/h) or rain resulted in the CIT rating dropping to 1 or 2 (unacceptable) and was thus an override of pleasant thermal conditions. Further cross-cultural research is underway to examine whether climate preferences vary with different social and cultural tourist segments internationally. © 2007 ISB."
"14040398300;36538539800;6603262263;6701497749;","Examining the sensitivity of MM5-CMAQ predictions to explicit microphysics schemes and horizontal grid resolutions, Part I-Database, evaluation protocol, and precipitation predictions",2008,"10.1016/j.atmosenv.2007.12.067","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43149100111&doi=10.1016%2fj.atmosenv.2007.12.067&partnerID=40&md5=851429a0e816f56f1c9e4e9a923f2f7a","Wet deposition of chemical species is one of the most difficult processes to simulate in three-dimensional (3-D) air quality models, due to the complex interplay among meteorology, cloud, and atmospheric chemistry. Different cloud microphysical treatments and horizontal grid resolutions in 3-D models can directly affect simulated clouds, precipitation, and wet deposition. In this study, the performance and sensitivity of the simulated precipitation, concentrations, and wet deposition to different explicit microphysics schemes and horizontal grid resolutions are evaluated for August and December 2002 for a domain centered over North Carolina (NC). Four explicit microphysics schemes in MM5 are examined: Reisner 1 (R1), Reisner 2 (R2), Dudhia (SI), and Hsie (WR). The precipitation evaluation indicates that monthly-average precipitation amounts are underpredicted by all schemes in both August and December at all sites except for the R1 August simulation that shows overpredictions at National Acid Deposition Program (NADP) sites. An increased sensitivity to microphysics schemes is found at locations in both the coastal plain and mountain regions in August and the mountain region in December. The differences in simulation results in August and December are mainly attributed to seasonal differences in dominant meteorological forcing (mesoscale vs. synoptic, respectively). Among the schemes tested, R2 and SI give the best overall performance in predicting precipitation for both months. These findings are applicable for NC and neighboring states with similar meteorological and emission characteristics."
"12139043600;56250250300;7005955015;12139310900;6506436908;","On the additivity of climate response to anthropogenic aerosols and CO2, and the enhancement of future global warming by carbonaceous aerosols",2008,"10.1111/j.1600-0870.2008.00308.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42549165534&doi=10.1111%2fj.1600-0870.2008.00308.x&partnerID=40&md5=5e1884e25dd71ee8b62c5b21cd6f33a4","Climate responses to aerosol forcing at present-day and doubled CO2-levels are studied based on equilibrium simulations with the CCM-Oslo atmospheric GCM coupled to a slab ocean. Aerosols interact on-line with meteorology through life-cycling of sulphate and black carbon (BC), and tables for aerosol optics and CCN activation. Anthropogenic aerosols counteract the warming by CO2 through a negative radiative forcing dominated by the indirect effect. Anthropogenic aerosols reduce precipitation by 4%, while CO2 doubling gives a 5% increase, mainly through enhanced convective activity, including a narrower ITCZ. Globally, the aerosol cooling is insensitive to CO2, and the effects of CO2 doubling are insensitive to aerosols. Hence, global climate responses to these sources of forcing are almost additive, although sulphate and BC burdens are slightly increased due to reduced stratiform precipitation over major anthropogenic source regions and a modified ITCZ. Regionally, positive cloud feedbacks give up to 5 K stronger aerosol cooling at present-day CO2 than after CO2 doubling. Aerosol emissions projected for year-2100 (SRES A2) strongly increase BC and change the sign of the direct effect. This results in a 0.3 K warming and 0.1% increase in precipitation compared to the year 2000, thus enhancing the global warming by greenhouse gases. © 2008 The Authors Journal compilation © 2008 Blackwell Munksgaard."
"6507501796;35204593500;36717393600;","The variation of ENSO characteristics associated with atmospheric parameter perturbations in a coupled model",2008,"10.1007/s00382-007-0313-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41449092111&doi=10.1007%2fs00382-007-0313-2&partnerID=40&md5=5c6d818ef8318e487f46db8272db2517","We analyse the differences in the properties of the El Niño Southern Oscillation (ENSO) in a set of 17 coupled integrations with the flux-adjusted, 19-level HadCM3 model with perturbed atmospheric parameters. Within this ensemble, the standard deviation of the NINO3.4 deseasonalised SSTs ranges from 0.6 to 1.3 K. The systematic changes in the properties of the ENSO with increasing amplitude confirm that ENSO in HadCM3 is prevalently a surface (or SST) mode. The tropical-Pacific SST variability in the ensemble of coupled integrations correlates positively with the SST variability in the corresponding ensemble of atmosphere models coupled with a static mixed-layer ocean (""slab"" models) perturbed with the same changes in atmospheric parameters. Comparison with the respective coupled ENSO-neutral climatologies and with the slab-model climatologies indicates low-cloud cover to be an important controlling factor of the strength of the ENSO within the ensemble. Our analysis suggests that, in the HadCM3 model, increased SST variability localised in the south-east tropical Pacific, not originating from ENSO and associated with increased amounts of tropical stratocumulus cloud, causes increased ENSO variability via an atmospheric bridge mechanism. The relationship with cloud cover also results in a negative correlation between the ENSO activity and the model's climate sensitivity to doubling CO2. © Springer-Verlag 2007."
"25928579600;7003623241;","Development of a severe winter index: Buffalo, New York",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049114611&partnerID=40&md5=d1bb39cadcc08deee69e50b536a4ee9c","Climate indices provide a useful way to characterize climate. The objective of this study is to rank the past 37 winters (1970-1971 to 2006-2007) in Buffalo, New York using a 'Severe Winter Index' (SWI) that incorporates a number of winter-related elements. Five elements were chosen to reflect varying aspects of a winter season: snowfall amount, number of days with 12 inches or greater of snow on the ground, heating degree days (HDD), number of days with temperatures at or below OT, and percent cloudiness during daylight hours. Data were obtained from the Buffalo Forecast Office of the National Weather Service. The SWI normalized each element by calculating the percentile-ranking of each data point within the data set. Each element was given equal weighting. The 1983-1984 winter season was the most severe, followed by 1977-1978 and 1976-1977. The mildest was the 1990-1991 winter season. 'Severe' winter seasons tend to group in the dataset, occurring for no more than three consecutive years. The SWI exhibits a decreasing trend and greater variability in winter severity. While 'Severe' and 'Average' winters can be expected, there appears to be a growing tendency for 'Mild' winters. © 2008 by Gamma Theta Upsilon."
"56289323700;24329947300;7005135473;","Multisensor data product fusion for aerosol research",2008,"10.1109/TGRS.2008.916087","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44249126423&doi=10.1109%2fTGRS.2008.916087&partnerID=40&md5=03f3ff6e045df5e6ec500e2e1e621b59","Combining data sets from multiple satellite sensors is a powerful method for studying Earth-atmosphere problems. By fusing data, we can utilize the strengths of the individual sensors that may not be otherwise possible. In this paper, we provide the framework for combining level 2 data products, using data from three sensors aboard the National Aeronautics and Space Administration (NASA)'s Terra satellite. These data include top-of-the-atmosphere (TOA) radiative energy fluxes obtained from the Clouds and the Earth's Radiant Energy System (CERES), aerosol optical thickness from the multispectral Moderate Resolution Imaging Spectroradiometer (MODIS), and aerosol properties from the Multi-angle Imaging SpectroRadiometer (MISR). The CERES Single Scanner Footprint (SSF) contains the pixel level CERES TOA fluxes and the level 2 MODIS aerosol data. We specifically focus upon fusing the CERES SSF with the MISR aerosol products. Although this project was undertaken specifically to address aerosol research, the methods employed for fusing data products can be used for other problems requiring synergistic data sets. We present selected case studies over different aerosol regimes and indicate that multisensor information provides value-added information for aerosol research that is not available from a single sensor. © 2008 IEEE."
"7003374464;7004044484;7003408439;","The west African monsoon dynamics. Part III: The quasi-biweekly zonal dipole",2008,"10.1175/2007JCLI1706.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45249123473&doi=10.1175%2f2007JCLI1706.1&partnerID=40&md5=9db52b4f46a02c2a5727180a50fdf2ae","This paper presents an investigation of the mechanisms giving rise to the main intraseasonal mode of convection in the African monsoon during northern summer, here identified as the quasi-biweekly zonal dipole (QBZD). The QBZD is primarily characterized by a quasi-stationary zonal dipole of convetion whose dimension is larger than the West African monsoon domain, with its two poles centered along the Guinean coast and between 30° and 60°W in the equatorial Atlantic. The QBZD dynamical processes within the Atlantic-Africa domain are examined in some detail. The QBZD has a dipole pattern associated with a Walker-type circulation in the near-equatorial zonal plane. It is controlled both by equatorial atmospheric dynamics through a Kelvin wave-like disturbance propagating eastward between its two poles and by land surface processes over Africa, inducing combined fluctuations in surface temperatures, surface pressure, and low-level zonal winds off the coast of West Africa. When convection is at a minimum over central and West Africa, a lack of cloud cover results in higher net shortwave flux at the surface, which increases surface temperatures and lowers surface pressures. This creates an east-west pressure gradient at the latitude of both the ITCZ (10°N) and the Saharan heat low (20°N), leading to an increase in eastward moisture advection inland. The arrival from the Atlantic of the positive pressure signal associated with a Kelvin wave pattern amplifies the low-level westerly wind component and the moisture advection inland, leading to an increase in convective activity over central and West Africa. Then the opposite phase of the dipole develops. Propagation of the QBZD convective envelope and of the associated 200 high-level velocity potential anomalies is detected from the eastern Pacific to the Indian Ocean. When the effect of the Kelvin wave propagation is removed by filtering, the stationary character of the QBZD is highlighted. The impact of the QBZD in combination with a Kelvin wave is illustrated by a case study of the monsoon onset in 1984. © 2008 American Meteorological Society."
"35272924300;6603943978;8403728600;7005661275;8403728700;16064490100;","Seasonal transport patterns of intense Saharan dust events at the Mediterranean island of Lampedusa",2008,"10.1016/j.atmosres.2007.10.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41549129040&doi=10.1016%2fj.atmosres.2007.10.007&partnerID=40&md5=9a6c94c16b9a112baa94472fd607afdc","Saharan dust (SD) episodes occurring at the Mediterranean island of Lampedusa (35.52° N, 12.63° E) from May 1999 to December 2005 have been shown to occur in the 26% of the cloud-free days [Meloni, D., di Sarra, A., Biavati, G., DeLuisi, J.J., Monteleone, F., Pace, G., Piacentino, S., Sferlazzo, D.M., 2007. Seasonal behavior of Saharan dust events at the Mediterranean island of Lampedusa in the period 1999-2005, Atmos. Environ. 41, 3041-3056]. In this paper we focus on intense SD events detected until September 2006, characterized by large values of the Saharan Dust Event Index (SDEI), the sum of the daily average aerosol optical depth at 500 nm, τ, over the duration of the dust episode. The SDEI index provides an indication about the intensity of SD events, due either to a long duration and/or to high dust optical depth. A total of 24 episodes characterized by large values of SDEI are examined. The NCEP-based maps of geopotential height and temperature at 700 mbar are used to identify the main circulation patterns driving SD to the Central Mediterranean and Lampedusa. Dust transport episodes in summer last for several days, and the corresponding SDEI values are the highest of the year. These episodes are mainly governed by two circulation patterns: the trough extending near the Atlantic coast of Europe and the high pressure system present in North Africa, generally above 25° N. This configuration causes strong south-westerly flows from the Sahara towards Southern Italy. The time evolution of τ for these long SD events shows that the largest values (> 0.3) are usually observed when the two patterns are present simultaneously, while low (< 0.3) τ values are measured when the Atlantic trough influence is weak. Moreover, the most probable loading region typically shows a warm kernel in North-Western Sahara, with a tongue extending north-eastward towards Sicily. In spring, moderate to high τ are measured, and SD episodes last as long as 13 days. Two synoptic configurations can be distinguished. Days with large τ are associated with the 700 mbar geopotential height features typical of summer. Days with moderate τ are found to be characterized by the Saharan high, but with the close low replaced by the Atlantic trough descending West of Africa or above the Iberian peninsula. In winter the typical meteorological conditions are determined by the presence of westerly cyclones. Depressions centered over Portugal, Central/Northern Europe, and Western Mediterranean have been shown to drive dust transport to Lampedusa. © 2007 Elsevier B.V. All rights reserved."
"55762732700;57202301596;","Role of atmospheric adjustments in the tropical Indian Ocean warming during the 20th century in climate models",2008,"10.1029/2008GL033631","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48249094305&doi=10.1029%2f2008GL033631&partnerID=40&md5=98a328945c5c8e2718256d3abd1f2b2f","The tropical Indian Ocean has been warming steadily since 1950s, a trend simulated by a large ensemble of climate models. In models, changes in net surface heat flux are small and the warming is trapped in the top 125 m depth. Analysis of the model output suggests the following quasi-equilibrium adjustments among various surface heat flux components. The warming is triggered by the greenhouse gas-induced increase in downward longwave radiation, amplified by the water vapor feedback and atmospheric adjustments such as weakened winds that act to suppress turbulent heat flux from the ocean. The sea surface temperature dependency of evaporation is the major damping mechanism. The simulated changes in surface solar radiation vary considerably among models and are highly correlated with inter-model variability in SST trend, illustrating the need to reduce uncertainties in cloud simulation. Copyright 2008 by the American Geophysical Union."
"10141883400;7003278104;8525144100;7404297096;7404829395;35550043200;","Characterization of MJO-related upper tropospheric hydrological processes using MLS",2008,"10.1029/2008GL033675","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48249138711&doi=10.1029%2f2008GL033675&partnerID=40&md5=2b2e2f429aa83efd7de152f602c1b8e8","This study quantifies Madden-Julian Oscillation (MJO)- related hydrological variability in the upper troposphere/lower stratosphere (UT/LS) using Aura Microwave Limb Sounder (MLS) cloud ice water content (IWC) and water vapor (H2O). In a composite of six boreal-winter MJO events, the UT/LS IWC anomaly is strongly positively correlated with the convection (TRMM rainfall) anomaly. IWC anomalies range from ±2 mg/m3 at 215 hPa to ±0.08 mg/m3 at 100 hPa. The UT/LS H2O anomaly has an eastward-tilting structure similar to the previous-documented temperature structure, but the H2O maximum lags the temperature maximum by about a week. The H2O anomaly is positively correlated with the convection anomaly in the UT (261 hPa) and LS (68 hPa) but negatively correlated with the convection anomaly near the tropopause (100 hPa). This analysis provides a multi-parameter construct useful in validating and improving the parameterization of convection, clouds and cloud microphysics in MJO modeling. Copyright 2008 by the American Geophysical Union."
"35302065900;7006437242;7005477332;7005703744;8507259400;6701316460;7004159070;7409080503;","Stratospheric impact of the Chisholm pyrocumulonimbus eruption: 1. Earth-viewing satellite perspective",2008,"10.1029/2007JD009153","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45549087555&doi=10.1029%2f2007JD009153&partnerID=40&md5=de55c8bf5a0287ee8e154b79a044c8ac","The pyrocumulonimbus storm near Chisholm, Alberta, on 28 May 2001 has been studied in depth. However, the impact of this eruption on the lower stratosphere has not been characterized. Here and in a companion paper we explore this topic. This paper focuses on the ""young"" Chisholm smoke plume, from the age of ∼3 h to 1 week, as observed by Earth-viewing satellite instruments. (The companion paper presents strictly profile data.) GOES visible and infrared image loops reveal the pyroconvective life cycle and initial transport of the smoke cloud. MISR stereographic heights are the first of their kind for a stratospheric cloud, showing smoke up to 5 km above the tropopause on 29 May. MODIS IR and visible images are analyzed to give constraints on plume height, thickness, and particle size. Infrared brightness temperature analyses reveal unique aspects of the ""day-after"" Chisholm plume. Particle sizes are 1/3 to 1/2 compared to normal cirrus crystals. The daytime 29 May plume is optically thick at tropopause temperatures yet smoky brown. A transition from deep anvil blow off to ""dry"" smoke is still occurring after ∼1.5 d. TOMS aerosol index is used as a proxy for areas of particularly high smoke plume altitude. The Chisholm smoke in the upper troposphere and lower stratosphere is traced with AI for 1 week as the plume blows across North America to western Europe. First estimates are made of stratospheric smoke mass in relation to emissions during pyroconvection. The 29 May stratospheric Chisholm pyroCb plume contains a mass between ∼1.39 × 104 and 1.09 × 105 t. This represents between ∼10% and 121% of total particle mass emitted from the fire on 28 May, calling into question some frequently assumed values for smoke single scatter albedo and/or emission estimates. Strictly in terms of mass, the stratospheric Chisholm plume amounted to ∼15% of background Northern Hemispheric stratospheric sulfate aerosol. Overall, the young pyroCb plume is seen to be a peculiar mixture of smoke aerosols and water-ice that confounds operational cloud/aerosol detection routines and exhibits extreme, and still mysterious, composition and life cycle features. Copyright 2008 by the American Geophysical Union."
"35459245100;7004469744;8942525300;24391333100;7102862273;","A global model study of processes controlling aerosol size distributions in the Arctic spring and summer",2008,"10.1029/2007JD009114","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45549085574&doi=10.1029%2f2007JD009114&partnerID=40&md5=64d6a101d157472b546973c1ab31a4b2","We use a global chemical transport model (CTM) with size-resolved aerosol microphysics to evaluate our understanding of the processes that control Arctic aerosol, focussing on the seasonal changes in the particle size distribution during the transition from Arctic haze in spring to cleaner conditions in summer. This period presents several challenges for a global model simulation because of changes in meteorology, which affect transport pathways and precipitation scavenging rates, changes in the ocean-atmosphere flux of trace gases and particulates associated with sea ice break-up and increased biological activity and changes in photolysis and oxidation rates which can affect particle nucleation and growth rates. Observations show that these changes result in a transition from an accumulation mode-dominated aerosol in spring to one dominated by Aitken and nucleation mode particles in summer. We find that remote Arctic aerosol size distribution is very sensitive to the model treatment of wet removal. In order to simulate the high accumulation mode concentrations typical of winter and spring it was necessary to substantially reduce the scavenging of these particles during transport. The resulting increases in accumulation mode lead to improvement in the modeled Aitken mode particle concentrations (which fall, due to increased scavenging in the free troposphere) and produce, aerosol, optical depths in good agreement with observations. The summertime increase in nucleation and Aitken mode particles is consistent with changes in local aerosol nucleation rates driven mainly by increased photochemical production of sulphuric acid vapor and to a lesser extent, by decreases in the condensation sink as Arctic haze decreases. Alternatively, to explain the observed summertime Aitken mode particle concentrations in terms of ultrafine sea spray particles requires a sea-air flux a factor 5-25 greater than predicted by current wind speed and sea surface temperature dependent flux parameterizations. The enhanced total flux is clearly higher than measured in the Arctic and cannot explain the observed nucleation mode in the high Arctic. The model suggests that the summertime source of Aitken particles has very little effect on the accumulation mode and aerosol optical depth but they may contribute to cloud condensation nuclei in clouds with updraught velocities greater than about 15 cm/s. From a global aerosol modeling perspective, our understanding of Arctic aerosol is poor. We suggest several processes that currently limit our ability to simulate this challenging environment. Copyright 2008 by the American Geophysical Union."
"24390253300;7402820442;57204346059;","Temporal and spatial characteristics of positive and negative Indian Ocean dipole with and without ENSO",2008,"10.1029/2007JD009151","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45549106368&doi=10.1029%2f2007JD009151&partnerID=40&md5=be3e054067dd985facee3ee5c5284c08","The differences in the temporal evolution and spatial characteristics of the Indian Ocean Dipole (IOD) between positive and negative events with and without ENSO have been investigated using observations for the period 1948-2002. To document such differences is particularly important for climate forecasts over far east Asia, since distinctly different monsoon activities over China, Korea, and Japan for different types of IOD are found in the composite maps of precipitation anomalies. The composite map of SST and wind during various stages of IOD and the ocean mixed layer heat budget showed that the IOD with and without ENSO has a large difference in its temporal evolutions and their triggering mechanisms. In both negative and positive IOD events without ENSO, the wind anomaly in the eastern Indian Ocean seems to be responsible for the formation of sea surface temperature anomalies, while the anomaly in the western Indian Ocean seems to be the oceanic dynamical response to the anomaly in the east. During the ENSO years, the temporal and spatial contrast of the asymmetry of the IOD evolution is smaller, and the SST anomaly is driven by the anomalies in incoming radiation due to changes in cloudiness caused by the ENSO associated anomalous atmospheric circulations and not by the local wind anomalies. Copyright 2008 by the American Geophysical Union."
"10243650000;7201485519;13402835300;7404142321;10241462700;7410084319;","Comparison of cloud response to CO2 doubling in two GCMS",2008,"10.2151/sola.2008-008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42449137373&doi=10.2151%2fsola.2008-008&partnerID=40&md5=16de2c2c950c03bbbb240f8147860239","The source terms of the cloud condensate tendency equation are analyzed for two general circulation models to clarify the effect of model differences on the non-convective cloud response to CO2 doubling. This analysis investigates the differences in the mechanism of cloud feedback between models, which is considered a major source of uncertainty in climate change projections. The two GCMs, the Hadley Centre model and MIROC, exhibit marked differences in cloud response in the mixed-phase region: cloud in middle to low latitudes decreases in the former and increases in the latter. The source terms indicate that the difference is attributable to the condensation-evaporation response. Discussions on the inter-model variance of cloud feedback may thus be assisted by developing a better understanding and evaluation of condensation-evaporation. The difference in the cloud response is also related to the relative importance of ice sedimentation compared to other microphysical processes: the former tends to increase mixedphase cloud while the latter tends to decrease the cloud. Physically based modeling of the relevant microphysical processes is thus considered essential for having more confidence in the simulated cloud feedback."
"7801611878;15081409200;6603054509;7004324889;","High resolution spatio-temporal water vapour mapping using GPS and MERIS observations",2008,"10.1080/01431160701436825","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41549113407&doi=10.1080%2f01431160701436825&partnerID=40&md5=e4a24577e86ed708aa912c28ae929283","Improved knowledge of atmospheric water vapour and its temporal and spatial variability is of great scientific interest for climate research and weather prediction. Moreover, the availability of fine resolution water vapour maps is expected to reduce significant errors in applications using the Global Positioning System, GPS, or radar interferometry. Several methods exist to estimate water vapour using satellite systems. Combining radiances as measured in two spectral bands of the Medium Resolution Imaging Spectrometer (MERIS) results in an Integrated Water Vapor (IWV) product with high spatial resolution, up to 300 m, but a limited temporal resolution of about three days, in case of cloud free conditions. On the other hand, IWV estimates can be derived from the zenith total delays as observed by continuous GPS networks. The GPS IWV estimates have a higher temporal resolution of typically 1 hour, but, even in Western Europe, inter-station distances are at least tenths of kilometres. Here we describe how to obtain IWV products with high spatio-temporal resolution by combining GPS and MERIS IWV estimates. For this purpose an analysis is made of MERIS and GPS based IWV data, retrieved at the same day over Western Europe. A variance-covariance analysis is performed and is subsequently applied to produce time series of combined high-resolution water vapour maps using Kriging. The research presented here is a first step towards near real-time fine resolution water vapour products."
"24398842400;57203053317;57208121852;13403689700;7006434689;","Aerosol processing in mixed-phase clouds in ECHAM5-HAM: Model description and comparison to observations",2008,"10.1029/2007JD009251","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45749156410&doi=10.1029%2f2007JD009251&partnerID=40&md5=110992da3ce68614d0e2efc89328de03","The global aerosol-climate model ECHAM5-HAM has been extended by an explicit treatment of cloud-borne particles. Two additional modes for in-droplet and in-crystal particles are introduced, which are coupled to the number of cloud droplet and ice crystal concentrations simulated by the ECHAM5 double-moment cloud microphysics scheme. Transfer, production, and removal of cloud-borne aerosol number and mass by cloud droplet activation, collision scavenging, aqueous-phase sulfate production, freezing, melting, evaporation, sublimation, and precipitation formation are taken into account. The model performance is demonstrated and validated with observations of the evolution of total and interstitial aerosol concentrations and size distributions during three different mixed-phase cloud events at the alpine high-altitude research station Jungfraujoch (Switzerland). Although the single-column simulations cannot be compared one-to-one with the observations, the governing processes in the evolution of the cloud and aerosol parameters are captured qualitatively well. High scavenged fractions are found during the presence of liquid water, while the release of particles during the Bergeron-Findeisen process results in low scavenged fractions after cloud glaciation. The observed coexistence of liquid and ice, which might be related to cloud heterogeneity at subgrid scales, can only be simulated in the model when assuming nonequilibrium conditions. Copyright 2008 by the American Geophysical Union."
"57197233116;7004942632;","Radiative forcing by persistent contrails and its dependence on cruise altitudes",2008,"10.1029/2007JD009117","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45749134639&doi=10.1029%2f2007JD009117&partnerID=40&md5=c49162e1a7294ad8266bc9c516c95210","The expected increase of global air traffic raises concern over the impact of aviation on climate, for instance via the creation of persistent contrails that influence the radiative budget of the Earth. Here the radiative forcing due to persistent contrails due to potential new aircraft, which are added to the present fleet, is studied as a function of cruise altitudes. A sophisticated radiative transfer model is used to calculate the forcing, assuming a contrail cover derived from ECMWF analyses combined with information on air traffic from the AER02k inventory for 2002. The global net forcing of the 2002 fleet is found to be 6 mW/m2 with a large uncertainty of about 50%, mainly due to the sparseness of contrail cover observations, assumptions about the optical depth of the contrails, and the small size of the net forcing, which results from a large cancellation of longwave and shortwave forcings of opposite signs. By increasing air traffic by, e.g., 10% in 2000 ft thick horizontal global layers in turn, it is found that contrails produced around 10 km have the largest impact on the radiative forcing per flown kilometer. A clear linear behavior was observed: in the most sensitive layer each percent of increase in air traffic leads to a 0.25% increased radiative forcing. A comparison between using ECMWF model outputs with different cloud schemes, allowing for or neglecting ice supersaturation, is presented. Copyright 2008 by the American Geophysical Union."
"15044936400;6506730508;15076205500;7006329853;","Modeling the transport and optical properties of smoke plumes from South American biomass burning",2008,"10.1029/2007JD009005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45749098501&doi=10.1029%2f2007JD009005&partnerID=40&md5=93dc1e7ac0cd87f7e6dd46248288c896","This study investigates the transport and optical properties of smoke plumes from South American biomass burning by using an aerosol transport and microphysical model. In general, the model can reproduce the smoke aerosol optical properties observed by satellite and ground-based instruments during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) campaign. The simulated spatial distribution of smoke aerosol loading over South America also compares well to satellite observations, suggesting that the transport processes in the model are adequate over this region. The results further suggest that the emissions provided by version 2 of the Global Fire Emissions Database are too low over South America, However, wet deposition may be too aggressive in the model. Since the model wet deposition does not include the feedback smoke may have on cloud formation and precipitation suppression, too many aerosols may be removed. Surprisingly, given the different vegetation types, the model simulations also suggest that similar initial particle size distributions and aerosol optical properties can be used to simulate smoke from both African savanna and South American forest fires. However, to reproduce the observed smoke aerosol optical properties over South America, humidification of smoke aerosols needs to be considered. Model results and observations both suggest that the typical single scattering albedo of smoke over South America and Africa differ because of relative humidity, not vegetation type. Overall, this work suggests strategies for improved treatment of South American smoke plumes in climate and microphysical models. Copyright 2008 by the American Geophysical Union."
"7003705113;57206038917;56154540200;7202779585;57208121852;7003931528;","Trace gas and aerosol interactions in the fully coupled model of aerosol-chemistry-climate ECHAM5-HAMMOZ: 1. Model description and insights from the spring 2001 TRACE-P experiment",2008,"10.1029/2007JD009007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69949134186&doi=10.1029%2f2007JD009007&partnerID=40&md5=7cead28ec6c2276a567e0a75bcc65b3a","In this paper, we introduce the ECHAM5-HAMMOZ aerosol-chemistry-climate model that includes fully interactive simulations of Ox-NOx-hydrocarbons chemistry and of aerosol microphysics (including prognostic size distribution and mixing state of aerosols) implemented in the General Circulation Model ECHAM5. The photolysis rates used in the gas chemistry account for aerosol and cloud distributions and a comprehensive set of heterogeneous reactions is implemented. The model is evaluated with trace gas and aerosol observations provided by the TRACE-P aircraft experiment. Sulfate concentrations are well captured but black carbon concentrations are underestimated. The number concentrations, surface areas, and optical properties are reproduced fairly well near the surface but underestimated in the upper troposphere. CO concentrations are well reproduced in general while O<inf>3</inf> concentrations are overestimated by 10-20 ppbv. We find that heterogeneous chemistry significantly influences the regional and global distributions of a number of key trace gases. Heterogeneous reactions reduce the ozone surface concentrations by 18-23% over the TRACE-P region and the global annual mean O<inf>3</inf> burden by 7%. The annual global mean OH concentration decreases by 10% inducing a 7% increase in the global CO burden. Annual global mean HNO<inf>3</inf> surface concentration decreases by 15% because of heterogenous reaction on mineral dust. A comparison of our results to those from previous studies suggests that the choice of uptake coefficients for a given species is the critical parameter that determines the global impact of heterogeneous chemistry on a trace gas (rather than the description of aerosol properties and distributions). A prognostic description of the size distribution and mixing state of the aerosols is important, however, to account for the effect of heterogeneous chemistry on aerosols as further discussed in the second part of this two-part series. Copyright 2008 by the American Geophysical Union."
"12242677000;36101394300;7005339628;24400369800;14068668300;","Land surface temperature retrieval at high spatial and temporal resolutions over the southwestern United States",2008,"10.1029/2007JD009048","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45749083375&doi=10.1029%2f2007JD009048&partnerID=40&md5=e71ada4f2a9b476084bfd274c0c50f9a","Land surface temperature (LST) and its diurnal variation are important when evaluating climate change, land-atmosphere energy exchange, and the global hydrological cycle. These characteristics are observable from satellites using thermal infrared measurements, but doing so at both high spatial and temporal resolutions has been difficult. Accurate temporal and spatial knowledge of LST is critical in global-scale hydrological assimilation to improve estimates of soil moisture and evapotranspiration. Historically, satellite retrieval of global LST at high spatial resolutions (1 km) has relied on NOAA polar-orbiting satellites recently augmented by Moderate Resolution Imaging Spectroradiometer (MODIS) data on board the Earth Observing System (EOS). Each satellite instrument in a polar orbit typically provides one to two observations per day. High temporal sampling of LST is achievable with geostationary satellites but at spatial resolutions is too coarse to distinguish different land surface types (4-5 km) and with lower accuracy. We describe an approach which employs MODIS data as a calibration source for Geostationary Environmental Satellite (GOES) data, then uses both data sets to yield half-hourly LST values, at 1 km spatial resolution, and returns LST with an accuracy better than 2°C. The approach requires good cloud clearing, atmospheric correction, and an underlying LST model to propagate values between observations. Retrieved LST against ground truth data indicate the approach is accurate to about 2°C. Copyright 2008 by the American Geophysical Union."
"6603591591;6603156461;7006760449;","Saharan mineral dust transport into the Caribbean: Observed atmospheric controls and trends",2008,"10.1029/2007JD009171","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45749143588&doi=10.1029%2f2007JD009171&partnerID=40&md5=81f7f4a00d5cf2d23c0a5c46bb2de989","Each summer large amounts of mineral dust from the Sahara are transported across the Atlantic and arrive at the Caribbean with far-reaching implications for climate in this region. In this paper we analyze summer season interannual variability of North African mineral dust over the Caribbean using the Total Ozone Mapping Spectrometer (TOMS)/Nimbus 7 (1979-1992) and TOMS/Earth Probe (1998-2000) satellite aerosol data. We apply the ""centers of action"" approach to gain insight into the atmospheric controls on Saharan dust transport into the Caribbean and identify longitudinal displacement and pressure fluctuation of the Hawaiian High as well as longitudinal displacement of the Azores High as key players. In contrast, traditional indices such as the North Atlantic Oscillation and the Southern Oscillation are not correlated with the mineral dust variations over the Caribbean region. We utilize National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis to investigate the underlying physical mechanisms and to identify meteorological conditions that correspond to high and low dust loads. Our analysis shows that two different transport routes from distinct source regions are responsible for transporting mineral dust into the Caribbean: a northern mode in which dust mobilized from the Sahara travels westward controlled primarily by the Azores High and a southern mode in which intense dust clouds originating in the Sahel region travel over the Gulf of Guinea to reach the Caribbean. The latter is controlled primarily by teleconnections with the Hawaiian High. Copyright 2008 by the American Geophysical Union."
"6701895637;7402287546;8856938500;55636317282;","The relationship between the Southern Hemisphere annular mode and antarctic Peninsula summer temperatures: Analysis of a high-resolution model climatology",2008,"10.1175/2007JCLI1695.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44449123541&doi=10.1175%2f2007JCLI1695.1&partnerID=40&md5=0ccf1fc76a5a95edca1d75c56f934528","The large regional summer warming on the east coast of the northern Antarctic Peninsula (AP), which has taken place since the mid-1960s, has previously been proposed to be caused by a trend in the Southern Hemisphere Annular Mode (SAM). The authors utilize a high-resolution regional atmospheric model climatology (14-km grid spacing) to study the mechanisms that determine the response of the near-surface temperature to an increase in the SAM (ΔT/ΔSAM). Month-to-month variations in near-surface temperature and surface pressure are well represented by the model. It is found that north of ∼68°S, ΔT/ΔSAM is much larger on the eastern (lee) side than on the western (windward) side of the barrier. This is because of the enhanced westerly flow of relatively warm air over the barrier, which warms (and dries) further as it descends down the lee slope. The downward motion on the eastern side of the barrier causes a decrease in surface-mass balance and cloud cover. South of ∼68°S, vertical deflection across the barrier is greatly reduced and the contrast in ΔT/ ΔSAM between the east and west sides of the barrier vanishes. In the northeastern part of the AP, the modeled Δ/ΔSAM distribution is similar to the distribution derived from satellite infrared radiometer data. The region of strongest modeled temperature sensitivity to the SAM is where ice shelf collapse has recently taken place and does not extend farther south over the Larsen-C Ice Shelf. © 2008 American Meteorological Society."
"57202099430;7005058694;7006087478;7003813649;7005886151;8581743700;6603654586;6701389765;7006031215;14015514600;7006104157;7006965640;6602579980;7007112987;6701386379;7003509783;36749030600;6602703376;8378887500;16029734400;6701797047;7004181239;7004168515;7102666935;","MIPAS: An instrument for atmospheric and climate research",2008,"10.5194/acp-8-2151-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42249099156&doi=10.5194%2facp-8-2151-2008&partnerID=40&md5=5a8138c6d354626f81fb0224aea8cb60","MIPAS, the Michelson Interferometer for Passive Atmospheric Sounding, is a mid-infrared emission spectrometer which is part of the core payload of ENVISAT. It is a limb sounder, i.e. it scans across the horizon detecting atmospheric spectral radiances which are inverted to vertical temperature, trace species and cloud distributions. These data can be used for scientific investigations in various research fields including dynamics and chemistry in the altitude region between upper troposphere and lower thermosphere. The instrument is a well calibrated and characterized Fourier transform spectrometer which is able to detect many trace constituents simultaneously. The different concepts of retrieval methods are described including multi-target and two-dimensional retrievals. Operationally generated data sets consist of temperature, H2O, O3, CH4, N2O, HNO3, and NO2 profiles. Measurement errors are investigated in detail and random and systematic errors are specified. The results are validated by independent instrumentation which has been operated at ground stations or aboard balloon gondolas and aircraft. Intercomparisons of MIPAS measurements with other satellite data have been carried out, too. As a result, it has been proven that the MIPAS data are of good quality. MIPAS can be operated in different measurement modes in order to optimize the scientific output. Due to the wealth of information in the MIPAS spectra, many scientific results have already been published. They include intercomparisons of temperature distributions with ECMWF data, the derivation of the whole NOy family, the study of atmospheric processes during the Antarctic vortex split in September∼2002, the determination of properties of Polar Stratospheric Clouds, the downward transport of NOx in the middle atmosphere, the stratosphere- troposphere exchange, the influence of solar variability on the middle atmosphere, and the observation of Non-LTE effects in the mesosphere."
"7007160862;7203085045;","Regional weather patterns during anomalous air-sea fluxes at the Kuroshio extension observatory (KEO)",2008,"10.1175/2007JCLI1797.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42549117882&doi=10.1175%2f2007JCLI1797.1&partnerID=40&md5=a8ad8c6dae7295736525d5cdc06a1dc4","The weather patterns during periods of anomalous surface fluxes in the Kuroshio recirculation gyre of the western North Pacific are documented. Separate analyses are carried out for the cold season (October-March) when the net surface heat flux is controlled by the combination of the turbulent sensible and latent heat fluxes (Qturb), and for the warm season (May-August) when the net heating is dominated by the net radiative fluxes (Qrad). For analysis of high-frequency (daily to weekly) variations in the fluxes, direct measurements from the Kuroshio Extension Observatory (KEO) for the period June 2004-November 2005 are used to specify flux events. For analysis of interannual variations, these events are selected using NCEP-NCAR reanalysis estimates for Qturb in the cold season, and International Comprehensive Ocean-Atmosphere Data Set (ICOADS) data for cloud fraction, as a proxy for Qrad, in the warm season. During the cold season, episodic high-frequency flux events are associated with significant anomalies in the cast-west sea level pressure gradients, and hence meridional winds and lower-troposphcric air temperature, reflecting the dominance of the atmospheric forcing of the flux variability. On the other hand, interannual variations in Qturb are associated with relatively weak atmospheric circulation anomalies, implying a relatively important role for the ocean. During the warm season, high-frequency fluctuations in the net surface fluxes occur due to a mix of anomalies in Qturb and Qrad. Enhanced cloudiness in the vicinity of KEO, and hence reduced Qrad, tends to occur in association with weak cyclonic disturbances of extratropical origin. A regional atmospheric circulation favoring these types of events also was found for warm seasons that were cloudier on the whole. Results suggest that the ocean's influence on air-sea fluxes at KEO is manifested mostly on interannual time scales during the cold season. © 2008 American Meteorological Society."
"16067735700;7201504886;7004479957;6701464294;7403326970;6701752471;7006904374;7402064802;35569011300;7202208382;6603566335;7006091410;","Parameterization of the atmospheric boundary layer: A view from just above the inversion",2008,"10.1175/BAMS-89-4-453","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44449120247&doi=10.1175%2fBAMS-89-4-453&partnerID=40&md5=6369784b7113882efb7696f225b63d31","Since the atmospheric boundary layer is one of the main components of the climate system, its realistic parameterization can yield better climate prediction models. However, there are relevant issues that need to be addressed to improve boundary layer parameterization like how to represent subgrid vertical fluxes, how to represent cloud fraction and cloud water, how to solve the equations efficiently and how to develop more general parameterizations that represent all types of boundary layers. As such, the Parameterization of the Atmospheric Boundary Layer was held in June 2005 at the UCL conference Center in California to tackle this issue. It discussed issues regarding boundary layer clouds, stable boundary layer, interaction with the surface, and interaction with deep convection."
"23987289400;7102862273;7102084129;6506180220;7005287667;","Anthropogenic aerosol effects on convective cloud microphysical properties in southern Sweden",2008,"10.1111/j.1600-0889.2007.00337.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41549123210&doi=10.1111%2fj.1600-0889.2007.00337.x&partnerID=40&md5=6158c9f62bbea2b7b1ceb54e83f712c2","In this study, we look for anthropogenic aerosol effects in southern Scandinavia's clouds under the influence of moderate levels of pollution and relatively weak dynamic forcing. This was done by comparing surface aerosol measurements with convective cloud microphysical profiles produced from satellite image analyses. The results show that the clouds associated with the anthropogenic-affected air with high PM0.5, had to acquire a vertical development of ∼3.5 km before forming precipitation-sized particles, compared to less than 1 km for the clouds associated with low PM0.5 air-masses. Additionally, a comparison of profiles with precipitation was done with regard to different potentially important parameters. For precipitating clouds the variability of the cloud thickness needed to produce the precipitation (Δ h14) is directly related to PM0.5 concentrations, even without considering atmospheric stability, the specific aerosol size distribution or the aerosols' chemical composition. Each additional 1 μg m-3 of PM0.5 was found to increase Δ h14 by ∼200-250 m. Our conclusion is that it is indeed possible to detect the effects of anthropogenic aerosol on the convective clouds in southern Scandinavia despite modest aerosol masses. It also emphasizes the importance of including aerosol processes in climate-radiation models and in numerical weather prediction models. © Journal compilation © 2008 Blackwell Munksgaard."
"36951202700;57214107381;7202834249;55665557400;","The influence of cloud cover index on the accuracy of solar irradiance model estimates",2008,"10.1007/s00703-007-0272-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43049148742&doi=10.1007%2fs00703-007-0272-5&partnerID=40&md5=aa229e9e826290eb765bc94a7fe1f24d","Cloud cover index (CCI) obtained from satellite images contains information on cloud amount and their optical thickness. It is the chief climate data for the assessment of solar energy resources in most radiative transfer models, particularly for the model BRASIL-SR that is currently operational at CPTEC. The wide range of climate environments in Brazil turns CCI determination into a challenging activity and great effort has been directed to develop new methods and procedures to improve the accuracy of these estimations from satellite images (Martins 2001; Martins et al. 2003a; Ceballos et al. 2004). This work demonstrates the influence of CCI determination methods on estimates of surface solar irradiances obtained by the model BRASIL-SR comparing deviations among ground data and model results. Three techniques using visible and/or thermal infrared images of GOES-8 were employed to generate the CCI for input into the model BRASIL-SR. The ground-truth data was provided by the solar radiation station located at Caicó/ PE, in Brazilian Northeast region, which is part of the UNEP/GEF project SWERA (Solar and Wind Energy Resources Assessment). Results have shown that the application of the bi-spectral techniques have reduced mean bias error up to 66% and root mean square error up to 50% when compared to the usual technique for CCI determination based on the straightforward determination of month-by-month extremes for maximum and minimum cloud states. © Springer-Verlag 2007."
"35570389600;57203049177;7201485519;7103373205;7103248807;","Mechanisms for the land/sea warming contrast exhibited by simulations of climate change",2008,"10.1007/s00382-007-0306-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39349109784&doi=10.1007%2fs00382-007-0306-1&partnerID=40&md5=399b4e3b7e3097069af718aa1722a93b","The land/sea warming contrast is a phenomenon of both equilibrium and transient simulations of climate change: large areas of the land surface at most latitudes undergo temperature changes whose amplitude is more than those of the surrounding oceans. Using idealised GCM experiments with perturbed SSTs, we show that the land/sea contrast in equilibrium simulations is associated with local feedbacks and the hydrological cycle over land, rather than with externally imposed radiative forcing. This mechanism also explains a large component of the land/sea contrast in transient simulations as well. We propose a conceptual model with three elements: (1) there is a spatially variable level in the lower troposphere at which temperature change is the same over land and sea; (2) the dependence of lapse rate on moisture and temperature causes different changes in lapse rate upon warming over land and sea, and hence a surface land/sea temperature contrast; (3) moisture convergence over land predominantly takes place at levels significantly colder than the surface; wherever moisture supply over land is limited, the increase of evaporation over land upon warming is limited, reducing the relative humidity in the boundary layer over land, and hence also enhancing the land/sea contrast. The non-linearity of the Clausius - Clapeyron relationship of saturation specific humidity to temperature is critical in (2) and (3). We examine the sensitivity of the land/sea contrast to model representations of different physical processes using a large ensemble of climate model integrations with perturbed parameters, and find that it is most sensitive to representation of large-scale cloud and stomatal closure. We discuss our results in the context of high-resolution and Earth-system modelling of climate change. © Crown Copyright 2007."
"11939918300;56188106700;57206546852;7003748648;","Cloud-resolving ensemble simulations of the August 2005 alpine flood",2008,"10.1002/qj.252","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41649110897&doi=10.1002%2fqj.252&partnerID=40&md5=18554ad74b67dcebcda3b1dc29dca5ff","In this study we explore the potential benefits of applying a cloud-resolving ensemble prediction system (EPS; 2.2 km grid spacing) over its driving synoptic-scale limited-area EPS (COSMO-LEPS, 10 km grid spacing, driven by the ECMWF EPS) for a case of heavy precipitation over the Alpine region. The selected event is the devastating August 2005 flood that affected the northern Alpine slopes. The cloud-resolving EPS includes an explicit treatment of deep convection and dynamically downscales the COSMO-LEPS information. Results are compared against rain-gauge and radar data. Furthermore, the sensitivity of the results to initial versus lateral boundary uncertainties are analyzed using a series of additional simulations. Comparison of the cloud-resolving and its driving limited-area EPS pinpoints the high skill of both ensembles in simulating the major phase of heavy precipitation. The high-resolution EPS yields more realistic rain amounts, in particular in areas of active convection, but in general the resolution-induced differences tend to be smaller than typical member-to-member variability. The differences between the two ensembles can be tied to the synoptic situation (stratiform or convective precipitation, location of the cyclone), to the mesoscale interaction of the flow with the topography (flow over the Alpine ridge), and to the experimental set-up (lead time and computational domain). For the considered event and set-up, the growth of initial perturbations dominates over lateral boundary uncertainties during the first ∼12 integration hours. Afterwards, the ensemble spread is controlled by large-scale error growth advected from the lateral boundaries into the domain. Copyright © 2008 Royal Meteorological Society."
"57203055233;7202216319;","A lagrangian spectral parameterization of gravity wave drag induced by cumulus convection",2008,"10.1175/2007JAS2369.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45849140572&doi=10.1175%2f2007JAS2369.1&partnerID=40&md5=4a234c22d0f36a287f0b06529dac7065","A Lagrangian spectral parameterization of gravity wave drag (GWD) induced by cumulus convection (GWDC) is developed based on ray theory and several assumptions and implemented into the NCAR Whole Atmosphere Community Climate Model. The Lagrangian parameterization calculates explicitly gravity wave (GW) propagation that has been treated too simply in existing column-based parameterizations. For comparison with column-based parameterization, a hydrostatic and Boussinesq version of the Lagrangian parameterization is used in the present study. One-day convective GW-packet trajectories demonstrate that the Lagrangian parameterization calculates reasonably the GW-packet propagation, and GW packets propagate upward along curved paths determined by Doppler shifting and the variation of stability. The GW trajectories show that the horizontal extent of GW propagation can be as large as 20° as GWs approach critical levels. Comparison with column-based parameterization through one-month simulations indicates that the magnitude of GWDC is much increased due mainly to the vertical convergence of GW packets in the lower stratosphere and equatorial troposphere with the Lagrangian parameterization. However, this increase in GWDC is found to be essentially dependent on the horizontal propagation characteristics of GWs. In climate simulations, it is found that the easterly flow in the equatorial stratosphere and mesospheric subtropical jet are improved through the Lagrangian parameterization. With the Lagrangian parameterization, interannual variability is significantly enhanced in the equatorial lower stratosphere and exhibits a structure related to the onset of the westerly phase of the stratospheric quasi-biennial oscillations. Finally, limitations of the current Lagrangian parameterization and required improvements are noted. © 2008 American Meteorological Society."
"7402655099;6701806265;7102403008;","The representation of a synoptic-scale weather system in a thermodynamically adjusted version of the ECHAM4 general circulation model",2008,"10.1007/s00703-007-0275-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43049144260&doi=10.1007%2fs00703-007-0275-2&partnerID=40&md5=f73b9d35b915acf4286a03350a79fe76","In this work, a strong cyclone event is simulated by the general circulation model (GCM) ECHAM4 for studying the representation of weather systems in a climate model. The system developed along the East Coast of the U.S.A. between the 12th and 14th of March 1993. The GCM simulation was started from climatological conditions and was continuously forced to the analyzed state by a thermodynamical adjustment based on the Newtonian relaxation technique (nudging). Relaxation terms for vorticity, divergence, temperature, and the logarithm of surface pressure were added at each model level and time step. The necessary forcing files were calculated from the ECMWF re-analysis (ERA15). No nudging terms were added for the components of the water cycle. Using this forcing, the model was able to reproduce the synoptic-scale features and its temporal development realistically after a spin-up period. This is true even for quantities that are not adjusted to the analysis (e.g., humidity). Detailed comparisons of the model simulations with available observations and the forcing ERA15 were performed for the cyclone case. Systematic errors were detected in the simulation of the thermodynamic state of the atmosphere, which can be traced back to deficiencies in model parametrizations. Differences in the representation of the surface fluxes lead to systematic deviations in near-surface temperature and wind fields. The general situation is very similar in both model representations. Errors were detected in the simulation of the convective boundary layer behind the cold front. The observed strong convective activity is missed both by the adjusted ECHAM4 simulation and ERA15. This is most likely caused by weaknesses in the cloud and convection schemes or by a too strong downdraft compensating the frontal lifting and suppressing the vertical transport of moisture from the boundary layer to higher levels. This work demonstrates for the investigated case the value of simulating single weather events in climate models for validating model physics. © Springer-Verlag 2007."
"22953390300;7003510880;12041883300;57219982231;","Evolution of the atmospheric boundary-layer structure of an arid Andes Valley",2008,"10.1007/s00703-007-0274-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43049138837&doi=10.1007%2fs00703-007-0274-3&partnerID=40&md5=cc534a6080dcef5c85a1fc598b722506","The boundary-layer structure of the Elqui Valley is investigated, which is situated in the arid north of Chile and extends from the Pacific Ocean in the west to the Andes in the east. The climate is dominated by the south-eastern Pacific subtropical anticyclone and the cold Humboldt Current. This combination leads to considerable temperature and moisture gradients between the coast and the valley and results in the evolution of sea and valley wind systems. The contribution of these mesoscale wind systems to the heat and moisture budget of the valley atmosphere is estimated, based on radiosoundings performed near the coast and in the valley. Near the coast, a well-mixed cloud-topped boundary layer exists. Both, the temperature and the specific humidity do not change considerably during the day. In the stratus layer the potential temperature increases, while the specific humidity decreases slightly with height. The top of the thin stratus layer, about 300 m in depth, is marked by an inversion. Moderate sea breeze winds of 3-4 ms-1 prevail in the sub-cloud and cloud layer during daytime, but no land breeze develops during the night. The nocturnal valley atmosphere is characterized by a strong and 900 m deep stably stratified boundary layer. During the day, no pronounced well-mixed layer with a capping inversion develops in the valley. Above a super-adiabatic surface layer of about 150 m depth, a stably stratified layer prevails throughout the day. However, heating can be observed within a layer above the surface 800 m deep. Heat and moisture budget estimations show that sensible heat flux convergence exceeds cold air advection in the morning, while both processes compensate each other around noon, such that the temperature evolution stagnates. In the afternoon, cold air advection predominates and leads to net cooling of the boundary layer. Furthermore, the advection of moist air results in the accumulation of moisture during the noon and afternoon period, while latent heat flux convergence is of minor relevance to the moisture budget of the boundary layer. © Springer-Verlag 2007."
"23975649000;7003663731;","Mountain permafrost probability mapping using the BTS method in two climatically dissimilar locations, northwest Canada",2008,"10.1139/E08-013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46749138324&doi=10.1139%2fE08-013&partnerID=40&md5=ac0820c4b6fda92d06eebc0d21b54c22","The Basal Temperature of Snow (BTS) method was used to predict permafrost distribution in two climatologically dissimilar mountain environments in northwest Canada. Permafrost probability maps with 30 m × 30 m grid cells were generated for part of the Ruby Range, Yukon Territory (425 km2), and for the Haines Summit area, northern British Columbia (536 km2), using winter BTS measurements in conjunction with late-summer ground truthing by probing and digging pits to physically verify the presence of permafrost. BTS values, and hence permafrost distribution, were modeled using elevation and potential incoming solar radiation (PISR) for the Ruby Range. PISR was not significant at Haines Summit, probably because persistent cloudiness associated with its more maritime climatic regime reduced aspect-induced variability in insolation. Probability maps indicate that ∼66% of the Ruby Range area and ∼43% of the Haines Summit area are underlain by permafrost. Therefore, the Ruby Range should be classified as extensive discontinuous permafrost, while Haines Summit is part of the sporadic discontinuous permafrost zone and not the isolated patches zone as portrayed on recent maps. Extensive ground truthing proved to be an essential part of the procedure because traditional BTS ""rules-of-thumb"" did not remain valid across the differing mountain climate zones. © 2008 NRC Canada."
"16479754400;23976830600;","A topography-based model of forest cover at the alpine tree line in the tropical Andes",2008,"10.1111/j.1365-2699.2007.01818.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40749132545&doi=10.1111%2fj.1365-2699.2007.01818.x&partnerID=40&md5=ad29a387127d8adae413eee253ee4bcc","Aim: To present a method that assesses the influence of environmental variables, including climate, substrate, topography, and anthropogenic disturbances, on the distribution of Andean forest at the tree line, and to compare this forest distribution between areas. Location: Sangay National Park, on the eastern slopes of the Andes in central Ecuador. Methods: A logistic regression model was built using topographical variables and environmental indices, derived from a digital elevation model, to explain forest cover, derived from a Landsat ETM image, in a zone around the average tree line altitude. Results: The model shows that after altitude, which can explain about 80% of forest cover, wetness has the next strongest effect (areas accumulating water, but also cold air, were devoid of forest, resulting in inverted tree lines), followed by eastness (western slopes had forest to higher altitudes). Application of the model in two nearby areas showed that the real tree line was lower than the predicted tree line in both areas, probably owing mainly to macroclimatic differences in one area, and partly also to human land use in the other. The locations with the largest deviations could be the focus of further research concerning human impacts on tree line vegetation. Main conclusions: The tree line is located at lower altitudes on east-facing slopes, which may be because high levels of radiation are received by east-facing slopes in the clear mornings, resulting in the photoinhibition of tree seedlings in the páramo. In spite of the limitations of the quality and resolution of the remote sensing data, the presented method provides indications for important ecological factors at the tree line. The method also allows the detection of differences in tree line position between areas, which may reflect climatic differences or the location of anthropogenic disturbances. © 2007 The Authors."
"7003397735;7003946763;7103170390;7003824291;7003665942;7101877072;","Seasonal and latitudinal variation of noctilucent cloud altitudes",2008,"10.1029/2007GL032281","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44349122291&doi=10.1029%2f2007GL032281&partnerID=40&md5=94e57be279b9e99ad51f6aa0db1928f9","We present a summary of ∼1500 hours of lidar measurements of noctilucent cloud (NLC) altitudes at Kühlungsborn (54°N), ALOMAR (69°N), and Spitsbergen (78°N). Mean centroid altitudes (zc) are 82.75 km, 83.33 km, and 83.68 km, respectively. Standard deviations σ representing geophysical variability are ∼0.7-1.6 km. Errors of mean heights Δzc are much smaller (60-340 m). Several processes which are not yet fully understood influence zc. Therefore, σ is a better measure of uncertainties in zc compared to Δzc. The increase of NLC heights with latitude is very small (43 ± 65 m/deg) and statistically not significant. At ALOMAR zc varies with season by up to ∼1-1.5 km. NLC heights accumulate around climatological temperatures of 145 K at 69°N and 78°N (higher at 54°N). The LIMA model nicely reproduces observations and indicates that non-variation of NLC heights at polar latitudes is caused by temperature uniformity: the 145 K isotherm varies in height by less than 250 m from the pole to 60°N. Copyright 2008 by the American Geophysical Union."
"6602600408;57203200427;10139397300;56270311300;","Satellite-based estimate of the direct and indirect aerosol climate forcing",2008,"10.1029/2007JD008962","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43449091896&doi=10.1029%2f2007JD008962&partnerID=40&md5=43c967156f592fd0767e3f629eba1625","The main uncertainty in anthropogenic forcing of the Earth's climate stems from pollution aerosols, particularly their ""indirect effect"" whereby aerosols modify cloud properties. We develop a new methodology to derive a measurement-based estimate using almost exclusively information from an Earth radiation budget instrument (CERES) and a radiometer (MODIS). We derive a statistical relationship between planetary albedo and cloud properties, and, further, between the cloud properties and column aerosol concentration. Combining these relationships with a data set of satellite-derived anthropogenic aerosol fraction, we estimate an anthropogenic radiative forcing of -0.9± 0.4 Wm-2 for the aerosol direct effect and of -0.2 ± 0.1 Wm-2 for the cloud albedo effect. Because of uncertainties in both satellite data and the method, the uncertainty of this result is likely larger than the values given here which correspond only to the quantifiable error estimates. The results nevertheless indicate that current global climate models may overestimate the cloud albedo effect. Copyright 2008 by the American Geophysical Union."
"55522563200;55740664200;55207447000;56611366900;7004057920;","The role of adiabaticity in the aerosol first indirect effect",2008,"10.1029/2007JD008961","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43449102178&doi=10.1029%2f2007JD008961&partnerID=40&md5=904b90c2e4eefe7a5feb4cc55db04090","Aerosol indirect effects are the most uncertain of the climate forcing mechanisms that have operated through the industrial period. Several studies have demonstrated modifications of cloud properties due to aerosols and corresponding changes in shortwave and longwave radiative fluxes under specific cloud conditions, but some recent studies have indicated that cloud dynamical processes such as entrainment-mixing may be the primary modulator of cloud optical properties in certain situations. For example, day-to-day variations of the cloud drop effective radius (r<inf>e</inf>) determined from the ground-based remote sensing at the Southern Great Plains were found to be weakly associated with the variations in aerosol loading as characterized by its light-scattering coefficient at the surface, implying that other processes were impacting the cloud radiative properties. To study these other impacts, we extend a previous study to investigate the role of changes in liquid water path (LWP) and r<inf>e</inf> in single layer stratiform clouds that are induced by entrainment-mixing processes and their effects on cloud radiative properties. We quantify the degree of entrainment-mixing in terms of the adiabaticity defined as the ratio of the observed cloud liquid water path to the corresponding adiabatic value. The cloud optical depth is, as expected, governed primarily by LWP, but that adiabaticity is the next most influential factor. In contrast, r<inf>e</inf> is found to be equally sensitive to adiabaticity and LWP. In adiabatic clouds the aerosol first indirect effect is clearly observed and related to independent measures of aerosol loading. In sub-adiabatic clouds the aerosol first indirect effect is not readily observed; this may in some circumstances be due to interference from heterogeneous mixing processes that change the droplet number density in a manner that attenuates the effect. Copyright 2008 by the American Geophysical Union."
"56611366900;7005862399;7003842561;","Ship tracks revisited: New understanding and cloud parameterization",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-40549123681&partnerID=40&md5=6e5a7129771579443293b0086d639f96","Ship tracks have been considered the Rosetta Stone demonstrating the effects of anthropogenic aerosols on cloud radiative properties through alteration of cloud microphysical properties. Previous ship-track studies have focused on identifying the signatures of indirect aerosol effects (e.g. enhanced droplet concentration) caused by ship emissions, and have been mainly concerned with comparing cloud properties within ship tracks to those of surrounding clouds on an individual track-by-track basis. Here we show that, examined together, ship-track studies can also provide crucial insights into cloud parameterizations in climate models, as well as understanding the conditions conducive to ship-track formation. It is found that unlike the measurements from general stratiform clouds where the effective radius is larger than the mean volume radius, the effective radius is smaller than the mean volume radius for some clouds in which ship tracks form. The radius ratio (the ratio of the effective radius to the mean volume radius) varies significantly and cannot be ignored in cloud parameterizations. The relation between the radius ratio and the spectral shape descriptors (relative dispersion and skewness) of the cloud droplet size distribution is further examined, revealing that the clouds with the effective radius smaller than the mean volume radius are likely to have negatively skewed cloud droplet size distributions with a higher concentration of relatively big droplets."
"7102171439;23975862800;35236899800;25031430500;7005528388;7102018821;","Tropical thin cirrus and relative humidity observed by the Atmospheric Infrared Sounder",2008,"10.5194/acp-8-1501-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40749121351&doi=10.5194%2facp-8-1501-2008&partnerID=40&md5=649fc8fef255265572e9e5893e030780","Global observations of cloud and humidity distributions in the upper troposphere within all geophysical conditions are critically important in order to monitor the present climate and to provide necessary data for validation of climate models to project future climate change. Towards this end, tropical oceanic distributions of thin cirrus optical depth (τ), effective diameter (De), and relative humidity with respect to ice (RHi) within cirrus (RHic) are simultaneously derived from the Atmospheric Infrared Sounder (AIRS). Corresponding increases in De and cloud temperature are shown for cirrus with τ&gt;0.25 that demonstrate quantitative consistency to other surface-based, in situ and satellite retrievals. However, inferred cirrus properties are shown to be less certain for increasingly tenuous cirrus. In-cloud supersaturation is observed for 8-12% of thin cirrus and is several factors higher than all-sky conditions; even higher frequencies are shown for the coldest and thinnest cirrus. Spatial and temporal variations in RHiC correspond to cloud frequency while regional variability in RHiC is observed to be most prominent over the N. Indian Ocean basin. The largest cloud/clear sky RHi anomalies tend to occur in dry regions associated with vertical descent in the sub-tropics, while the smallest occur in moist ascending regions in the tropics. The characteristics of RHic frequency distributions depend on τ and a peak frequency is located between 60-80% that illustrates RHic is on average biased dry. The geometrical thickness of cirrus is typically less than the vertical resolution of AIRS temperature and specific humidity profiles and thus leads to the observed dry bias, shown with coincident cloud vertical structure obtained from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The joint distributions of thin cirrus microphysics and humidity derived from AIRS provide unique and important regional and global-scale insights on upper tropospheric processes not available from surface, in situ, and other contemporary satellite observing platforms."
"7202429440;7201432984;16303438900;6507640204;7102447698;8570871900;6506545080;15032788000;56249704400;7201837768;7004214645;7006107059;7401491382;","Short-lived pollutants in the Arctic: Their climate impact and possible mitigation strategies",2008,"10.5194/acp-8-1723-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41249087239&doi=10.5194%2facp-8-1723-2008&partnerID=40&md5=021eb80529b68c305f1eec5fc0b1b474","Several short-lived pollutants known to impact Arctic climate may be contributing to the accelerated rates of warming observed in this region relative to the global annually averaged temperature increase. Here, we present a summary of the short-lived pollutants that impact Arctic climate including methane, tropospheric ozone, and tropospheric aerosols. For each pollutant, we provide a description of the major sources and the mechanism of forcing. We also provide the first seasonally averaged forcing and corresponding temperature response estimates focused specifically on the Arctic. The calculations indicate that the forcings due to black carbon, methane, and tropospheric ozone lead to a positive surface temperature response indicating the need to reduce emissions of these species within and outside the Arctic. Additional aerosol species may also lead to surface warming if the aerosol is coincident with thin, low lying clouds. We suggest strategies for reducing the warming based on current knowledge and discuss directions for future research to address the large remaining uncertainties."
[No author id available],"Cloud birth",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-42449107838&partnerID=40&md5=399dd51c8c0fd2dc5dde24c138f40ca9","Researchers in Helsinki have studied where particles come from and their profound effects on human health, influence on climate and cloud formation. Particles influence the climate in two ways. One is that light-colored particles can reflect sunshine back into space and offset the effects of greenhouse warming. On the other hand, black particles that come from burning coal or diesel absorb incoming sunshine and cause local warming. Particles help cloud development since cloud droplets need them on which to condense."
"24331295800;35571173100;6602729528;7006248174;6603031108;","The influence of cloud and surface properties on the arctic ocean shortwave radiation budget in coupled models",2008,"10.1175/2007JCLI1614.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44349109009&doi=10.1175%2f2007JCLI1614.1&partnerID=40&md5=cdb1fe22958801fc5c7b5995471cb601","The impact of sea ice concentrations, surface albedo, cloud fraction, and cloud ice and liquid water paths on the surface shortwave (SW) radiation budget is analyzed in the twentieth-century simulations of three coupled models participating in the Intergovernmental Panel on Climate Change Fourth Assessment Report. The models are the Goddard Institute for Space Studies Model E-R (GISS-ER), the Met Office Third Hadley Centre Coupled Ocean-Atmosphere GCM (UKMO HadCM3), and the National Center for Atmosphere Research Community Climate System Model, version 3 (NCAR CCSM3). In agreement with observations, the models all have high Arctic mean cloud fractions in summer, however, large differences are found in the cloud ice and liquid water contents. The simulated Arctic clouds of CCSM3 have the highest liquid water content, greatly exceeding the values observed during the Surface Heat Budget of the Arctic Ocean (SHEBA) campaign. Both GISS-ER and HadCM3 lack liquid water and have excessive ice amounts in Arctic clouds compared to SHEBA observations. In CCSM3, the high surface albedo and strong cloud SW radiative forcing both significantly decrease the amount of SW radiation absorbed by the Arctic Ocean surface during the summer. In the GISS-ER and HadCM3 models, the surface and cloud effects compensate one another: GISS-ER has both a higher summer surface albedo and a larger surface incoming SW flux when compared to HadCM3. Because of the differences in the models' cloud and surface properties, the Arctic Ocean surface gains about 20% and 40% more solar energy during the melt period in the GISS-ER and HadCM3 models, respectively, compared to CCSM3. In twenty-first-century climate runs, discrepancies in the surface net SW flux partly explain the range in the models' sea ice area changes. Substantial decrease in sea ice area simulated during the twenty-first century in CCSM3 is associated with a large drop in surface albedo that is only partly compensated by increased cloud SW forcing. In this model, an initially high cloud liquid water content reduces the effect of the increase in cloud fraction and cloud liquid water on the cloud optical thickness, limiting the ability of clouds to compensate for the large surface albedo decrease. In HadCM3 and GISS-ER, the compensation of the surface albedo and cloud SW forcing results in negligible changes in the net SW flux and is one of the factors explaining moderate future sea ice area trends. Thus, model representations of cloud properties for today's climate determine the ability of clouds to compensate for the effect of surface albedo decrease on the future shortwave radiative budget of the Arctic Ocean and, as a consequence, the sea ice mass balance. © 2008 American Meteorological Society."
"14825561100;7004862771;","Spatio-temporal combination of MODIS images - Potential for snow cover mapping",2008,"10.1029/2007WR006204","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43049092989&doi=10.1029%2f2007WR006204&partnerID=40&md5=ee22a604e1b0413b6c8f9a7ad3a82d65","MODIS snow cover products are appealing for hydrological applications because of their good accuracy and daily availability. Their main limitation, however, is cloud obscuration. In this study we evaluate simple mapping methods, termed temporal and spatial filters, that reduce cloud coverage by using information from neighboring non-cloud covered pixels in time or space, and by combining MODIS data from the Terra and Aqua satellites. The accuracy of the filter methods is evaluated over Austria, using daily snow depth observations at 754 climate stations and daily MODIS images in the period 2003-2005. The results indicate that the filtering techniques are remarkably efficient in cloud reduction, and the resulting snow maps are still in good agreement with the ground snow observations. There exists a clear, seasonally dependent, trade off between accuracy and cloud coverage for the various filtering methods. An average of 63% cloud coverage of the Aqua images is reduced to 52% for combined Aqua-Terra images, 46% for the spatial filter, 34% for the 1-day temporal filter and 4% for the 7-day temporal filter, and the corresponding overall accuracies are 95.5%, 94.9%, 94.2%, 94.4% and 92.1%, respectively. Copyright 2008 by the American Geophysical Union."
"56511954300;57200366382;56629149600;56249551800;57090634600;","The climate of the coast and fog zone in the Tarapacá Region, Atacama Desert, Chile",2008,"10.1016/j.atmosres.2007.11.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39149122501&doi=10.1016%2fj.atmosres.2007.11.011&partnerID=40&md5=8da317bb548b2cf278ab6d7eb0a7ce12","In the Atacama Desert, the narrow littoral plain and the adjacent mountain range have a unique climate. This area is locally called the ""coastal desert with abundant cloudiness"", and extends from the coastline up to an elevation of 1000 m. The climate is designated as being BWn according to Köppen's Climate Classification as adapted for Chile. In the original classification the acronym (Bn) is used for foggy environments. Toward the east a ""normal desert"" climate (BW) is found. This is known as one of the most extreme deserts of the world. In the BWn areas there are meteorological differences between low and high elevation zones. The climate of the coastal plains and the mountains is described in this paper in order to show that there is an area where the climate differs from those classified as BWn and BW in the Chilean Climate Classification. This area is located between 650 and 1200 m a.s.l. and contains several fog oases or lomas vegetation, rich in biodiversity and endemism. The weather is warmer near sea level, with an annual average temperature of 18 °C. At high elevation sites like Alto Patache, the temperature decreases at a rate of 0.7 °C for every 100-m increase in altitude. The average annual minimum temperature often approaches 1 °C in winter, while the mean annual temperature range is significant (8.3 °C in Los Cóndores). The mean monthly relative humidity in Alto Patache is over 80%, except during the summer months. During autumn, winter and spring high elevation fog is present in the study area at altitudes ranging from 650 m up to 1060 m, giving annual water yields of 0.8 to 7 L m- 2 day- 1. If vegetation is used as an indicator, the foggy zone lies between 650 m a.s.l. and 1200 m a.s.l. About 70% of the mountain range experiences the foggy climate, as opposed to the coastal plains that are characterized by a cloudy climate. © 2007 Elsevier B.V. All rights reserved."
"8520395200;7103109066;7003378484;6603561077;7801659989;56182830100;","Biogeochemistry of iron in Australian dust: From eolian uplift to marine uptake",2008,"10.1029/2007GC001813","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48149112008&doi=10.1029%2f2007GC001813&partnerID=40&md5=f415639ba437eee533217ca0621dd34e","Dust is an important vector for iron supply to the ocean, which subsequently impacts ocean productivity, atmospheric CO2 concentrations, and hence global climate. Here, we synthesize the processes influencing the biogeochemistry of Australian dust and compare them with those from other Southern Hemisphere dust sources. Our observations range from soil and dust physical properties to abrasion and cloud chamber chemistry experiments to dust storms and their dispersion and deposition. We then present satellite observations of the impact of episodic dust deposition events on the productivity of low-iron oceanic waters north (i.e., low-nitrate, low-chlorophyll (LNLC)) and south (i.e., high-nitrate, lowchlorophyll (HNLC)) of Australia. Dust deposition from the largest dust storm in over 40 years did not result in iron-mediated algal blooms in either oceanic region. A comparison of Australia with other Southern Hemisphere source regions reveals that the relatively well sampled Australian system is a poor generic model. Furthermore, there are marked distinctions between Southern and Northern Hemisphere iron/dust biogeochemistry that must be recognized by modelers and included in future simulations. Better information is required on the relative role of the atmosphere and ocean on influencing iron biogeochemistry and how their relative influences might change in the future due to climate change. Copyright 2008 by the American Geophysical Union."
"7004399781;7004015298;56878283500;7801467546;6603094181;57215223917;57208464149;55984424900;7005601996;7006354036;7006813055;7005182425;7003658685;35998927000;23025467900;21741206300;8084443000;7005274759;17435961300;6506129917;57050508600;24484158900;","The ABC-Pyramid Atmospheric Research Observatory in Himalaya for aerosol, ozone and halocarbon measurements",2008,"10.1016/j.scitotenv.2007.10.024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37649008910&doi=10.1016%2fj.scitotenv.2007.10.024&partnerID=40&md5=11bf4db2aa362707c8849a60f91f1d8a","In this work we present the new ABC-Pyramid Atmospheric Research Observatory (Nepal, 27.95 N, 86.82 E) located in the Himalayas, specifically in the Khumbu valley at 5079 m a.s.l. This measurement station has been set-up with the aim of investigating natural and human-induced environmental changes at different scales (local, regional and global). After an accurate instrumental set-up at ISAC-CNR in Bologna (Italy) in autumn 2005, the ABC-Pyramid Observatory for aerosol (physical, chemical and optical properties) and trace gas measurements (ozone and climate altering halocarbons) was installed in the high Khumbu valley in February 2006. Since March 2006, continuous measurements of aerosol particles (optical and physical properties), ozone (O3) and meteorological parameters as well as weekly samplings of particulate matter (for chemical analyses) and grab air samples for the determination of 27 halocarbons, have been carried out. These measurements provide data on the typical atmospheric composition of the Himalayan area between India and China and make investigations of the principal differences and similarities between the monsoon and pre-monsoon seasons possible. The study is carried out within the framework of the Ev-K2-CNR ""SHARE-Asia"" (Stations at High Altitude for Research on the Environment in Asia) and UNEP-""ABC"" (Atmospheric Brown Clouds) projects. With the name of ""Nepal Climate Observatory-Pyramid"" the station is now part of the Observatory program of the ABC project. © 2007 Elsevier B.V. All rights reserved."
"9243772600;6603699044;","Climatology of strong intermountain cold fronts",2008,"10.1175/2007MWR2136.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44449106536&doi=10.1175%2f2007MWR2136.1&partnerID=40&md5=d76f9a706ab0d1611c460b0558606580","Motivated by the intensity and severity of winds and temperature falls that frequently accompany rapidly eveloping cold fronts in northern Utah, this paper presents a 25-yr climatology of strong cold frontal passages over the Intermountain West and adjoining western United States. Using conventional surface observations and the North American Regional Reanalysis, strong cold frontal passages are identified based on a temperature fall of 7°C or greater in a 2-3-h period, a concurrent pressure rise of 3 hPa or greater, and the presence of a large-scale 700-hPa temperature gradient of at least 6°C (500 km)-1. The number of strong cold frontal passages exhibits a strong continental signature with very few events (&lt;10) along the Pacific coast and more than 200 events east of the Continental Divide. The number of events increases dramatically from the Cascade Mountains and Sierra Nevada to northern Utah, indicating that the Intermountain West is a frequent cold front breeding ground. A composite of the 25 strongest events at Salt Lake City (based on the magnitude of the temperature fall) reveals that confluent deformation acting on a broad baroclinic zone over central Nevada commonly initiates Intermountain frontogenesis. The confluent deformation develops in southwesterly large-scale flow and appears to be enhanced by flow deflection around the Sierra Nevada. Quasi-stationary development and intensification of the southwest-northeast-oriented cold front then occurs as a mobile upper-level trough approaches from the west. The front becomes mobile as cold advection and ascent associated with the upper-level trough overtake the low-level front. Cloud and precipitation observations suggest that differential diabatic heating contributes to the rapid frontal intensification in many events. © 2008 American Meteorological Society."
"14822032600;55401022300;17341189400;7003679485;6602635483;23050025700;7102582535;","Seasonality of major aerosol species and their transformations in Cairo megacity",2008,"10.1016/j.atmosenv.2007.10.081","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39149104952&doi=10.1016%2fj.atmosenv.2007.10.081&partnerID=40&md5=a6a24300eb66c174042d4ff5992a8e73","Bulk aerosols sampled on a weekly basis at two Cairo (Egypt) urban sites from January 2003 to May 2006 were analysed for their chemical composition of major aerosol species (elemental carbon, water soluble/insoluble organic carbon, nitrate, sulphate, ammonium, chloride, sodium and calcium). Data subsequently obtained constitute one of the longest and more detailed dataset related to Cairo aerosols, and offer the opportunity to investigate seasonal trends. Dust aerosols (derived from calcium measurements) displayed maximum concentrations in spring and winter, due to frequent dust storms, but also high background concentration levels (∼50 μg m-3) all year long. Within these particles, about 40% on average of Ca2+ was found to be associated with SO42-, NO3- and/or Cl-, pointing out ""dust anthropization"" processes and their subsequent climatic impact on a regional scale. Seasonal variations of non-dust aerosols, equally distributed between carbonaceous aerosols and ions, were also observed, with concentrations of the order of 100 μg m-3 in autumn and winter, and of 60 μg m-3 in spring and summer. High concentration levels of non-sea-salt chloride (up to 15 μg m-3 on a monthly basis), likely of industrial origin, were observed in autumn and winter. During the autumn ""Black Cloud"" event, biomass burning aerosols originating from rice straw burning in the Nile Delta have shown to account for 12%, 35% and 50% of Cairo EC, WIOC and WSOC mass concentrations, respectively. Finally, relatively low WSOC/OC ratios (∼1/3) were obtained all the year long, calling for more investigation on the water-solubility of organic aerosols originating from the burning of agricultural waste, and on that of secondary organic aerosols formed in dry urban atmospheres. © 2007 Elsevier Ltd. All rights reserved."
"24329376600;35547807400;","CO2 forcing induces semi-direct effects with consequences for climate feedback interpretations",2008,"10.1029/2007GL032273","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44249117154&doi=10.1029%2f2007GL032273&partnerID=40&md5=21d6a3acfb608246173f5f59414d4c47","Climate forcing and feedbacks are diagnosed from seven slab-ocean GCMs for 2 × CO2 using a regression method. Results are compared to those using conventional methodologies to derive a semi-direct forcing due to tropospheric adjustment, analogous to the semi-direct effect of absorbing aerosols. All models show a cloud semi-direct effect, indicating a rapid cloud response to CO2; cloud typically decreases, enhancing the warming. Similarly there is evidence of semi-direct effects from water-vapour, lapse-rate, ice and snow. Previous estimates of climate feedbacks are unlikely to have taken these semi-direct effects into account and so misinterpret processes as feedbacks that depend only on the forcing, but not the global surface temperature. We show that the actual cloud feedback is smaller than what previous methods suggest and that a significant part of the cloud response and the large spread between previous model estimates of cloud feedback is due to the semi-direct forcing. Copyright 2008 by the American Geophysical Union."
"23571129400;8670472000;7003557662;6506579205;23571234400;23570843600;","An evaluation of the surface radiation budget over North America for a suite of regional climate models against surface station observations",2008,"10.1007/s00382-008-0378-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-54949117222&doi=10.1007%2fs00382-008-0378-6&partnerID=40&md5=3ad6b6fcdd5eac66d44a4085eec563fa","Components of the surface radiation budget (SRB) [incoming shortwave radiation (ISR) and downwelling longwave radiation (DLR)] and cloud cover are assessed for three regional climate models (RCM) forced by analysed boundary conditions, over North America. We present a comparison of the mean seasonal and diurnal cycles of surface radiation between the three RCMs, and surface observations. This aids in identifying in what type of sky situation simulated surface radiation budget errors arise. We present results for total-sky conditions as well as overcast and clear-sky conditions separately. Through the analysis of normalised frequency distributions we show the impact of varying cloud cover on the simulated and observed surface radiation budget, from which we derive observed and model estimates of surface cloud radiative forcing. Surface observations are from the NOAA SURFRAD network. For all models DLR all-sky biases are significantly influenced by cloud-free radiation, cloud emissivity and cloud cover errors. Simulated cloud-free DLR exhibits a systematic negative bias during cold, dry conditions, probably due to a combination of omission of trace gas contributions to the DLR and a poor treatment of the water vapor continuum at low water vapor concentrations. Overall, models overestimate ISR all-sky in summer, which is primarily linked to an underestimate of cloud cover. Cloud-free ISR is relatively well simulated by all RCMs. We show that cloud cover and cloud-free ISR biases can often compensate to result in an accurate total-sky ISR, emphasizing the need to evaluate the individual components making up the total simulated SRB. © Springer-Verlag 2008."
"24329947300;56289323700;7005135473;","First observational estimates of global clear sky shortwave aerosol direct radiative effect over land",2008,"10.1029/2007GL032314","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44249126517&doi=10.1029%2f2007GL032314&partnerID=40&md5=cd021611a064640da2b750add1204352","Using one year (2000-2001) of merged Multiangle Imaging SpectroRadiometer (MISR), Moderate Resolution Imaging SpectroRadiometer (MODIS) and Clouds and the Earth's Radiant Energy System (CERES) data sets from NASA's Terra satellite, we estimate the top of atmosphere cloud-free direct radiative effect (DRE) of aerosols over global land areas. The global mean shortwave DRE is -5.1 ± 1.1 Wm-2 although substantial regional variability in DRE over land exists due to differences in aerosol properties and land cover types. This value is consistent with those reported in the literature although this is the first observational estimate of the global DRE over land using satellite data alone. Future studies need to separate the anthropogenic component of aerosols from satellite data to examine aerosol climate forcing over global scales. Copyright 2008 by the American Geophysical Union."
"8706262900;34770572800;","Tidal propagation of deep tropical cloud signatures into the thermosphere from TIMED observations",2008,"10.1029/2007GL032397","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44249111460&doi=10.1029%2f2007GL032397&partnerID=40&md5=033067f9f704dbfd6e5eab2e43fc5ff7","The diurnal eastward zonal wavenumber-3 (DE3) tide is excited in the tropical troposphere by latent heat release in deep convective clouds. Its direct propagation into the thermosphere is explored using Hough Mode Extension (HME) analysis of temperature T, and zonal and meridional wind (u, v) measurements from SABER and TIDI on board the TIMED satellite. HMEs provide observation-based tidal information about parameters not measured (vertical wind w, density p) and at latitudes and altitudes not covered by the two instruments. DE3 in (u, v, T, p) maximizes around 100 km. The thermospheric (180 km) signal is negligible for (v, p) but still considerable for (u, w, T). Maximum amplitudes are 6 m/s (u), 0.12 m/s (w), and 8 K (T). The HME analysis also shows the quantitative consistency of the DE3 tides from SABER and TIDI in the mesosphere/lower thermosphere region. This allows one to interpret the seasonal DE3 variation in terms of symmetric vs. antisymmetric modes. Copyright 2008 by the American Geophysical Union."
"7409389979;55210563600;57202301596;","Observations of the trade wind wakes of Kauai and Oahu",2008,"10.1029/2007GL031742","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44249114120&doi=10.1029%2f2007GL031742&partnerID=40&md5=aece78d702bf96d4cd7c1098beaa5777","The Hawaiian islands of Kauai and Oahu stand in the path of the east-northeasterly trade winds, creating wakes in the lee. For the first time, the structure of the wakes and their diurnal cycle were observed on a cruise during 18-20 December 2006. The dynamic wakes, characterized by reduced trades, extend about 1 km in height with strong wind shear at the top. Thermal forcing of these small islands also affects the wake circulations. Sea breezes develop in the afternoon turning the winds into westerly near the shore in the wakes. At night, land breezes advect cool air from the islands, creating a shallow cool layer between the sea surface and a capping inversion. The warming in the wake in the afternoon extends much deeper (1.4 km) than the cool layer (0.5 km) at night. The effect of diurnal changes on cloud formation in the wakes is discussed, and the sharp variations in wind velocity lee of the islands may affect ocean currents, waves and mixing. Copyright 2008 by the American Geophysical Union."
"12645612500;6602111828;","Impacts of 3-D radiative effects on satellite cloud detection and their consequences on cloud fraction and aerosol optical depth retrievals",2008,"10.1029/2007JD009095","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42549098506&doi=10.1029%2f2007JD009095&partnerID=40&md5=88ace846c85c51917c11bb3cdf8e662d","We present the first examination on how 3-D radiative transfer impacts satellite cloud detection that uses a single visible channel threshold. The 3-D radiative transfer through predefined heterogeneous cloud fields embedded in a range of horizontally homogeneous aerosol fields have been carried out to generate synthetic nadir-viewing satellite images at a wavelength of 0.67 μm. The finest spatial resolution of the cloud field is 30 m. We show that 3-D radiative effects cause significant histogram overlap between the radiance distribution of clear and cloudy pixels, the degree to which depends on many factors (resolution, solar zenith angle, surface reflectance, aerosol optical depth (AOD), cloud top variability, etc.). This overlap precludes the existence of a threshold that can correctly separate all clear pixels from cloudy pixels. The region of clear/cloud radiance overlap includes moderately large (up to 5 in our simulations) cloud optical depths. Purpose-driven cloud masks, defined by different thresholds, are applied to the simulated images to examine their impact on retrieving cloud fraction and AOD. Large (up to 100s of %) systematic errors were observed that depended on the type of cloud mask and the factors that influence the clear/cloud radiance overlap, with a strong dependence on solar zenith angle. Different strategies in computing domain-averaged AOD were performed showing that the domain-averaged BRF from all clear pixels produced the smallest AOD biases with the weakest (but still large) dependence on solar zenith angle. The large dependence of the bias on solar zenith angle has serious implications for climate research that uses satellite cloud and aerosol products. Copyright 2008 by the American Geophysical Union."
"7003498714;6701768500;6506988679;24080686800;7101877072;","The quasi 5-day signal in the mesospheric water vapor concentration at high latitudes in 2003-a comparison between observations at ALOMAR and calculations",2008,"10.1029/2007JD008875","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42549144949&doi=10.1029%2f2007JD008875&partnerID=40&md5=05f4839cc3e0db46de6007db02bc37ef","A quasi 5-day signature in different middle atmospheric parameters such as the horizontal wind, the temperature, the pressure, the occurrence rate of Polar Mesospheric Summer Echoes (PMSEs) and Noctilucent Clouds (NLCs) or the ozone concentration has been found during the last decades since the 1970s. These effects were interpreted in terms of the impact of a 5-day planetary normal mode (1,1) of Rossby waves. In the mesosphere the quasi 5-day variation is predominantly a summer phenomenon occurring in high and middle latitudes. Water vapor measurements were carried out by means of the microwave technique in high latitudes at ALOMAR (69.29°N, 16.03°E), Norway, for the year 2003. The observations revealed a clear signature of a quasi 5-day variation. Using our real-date Leibniz-Institute Middle Atmosphere (LIMA) model of the Institute of Atmospheric Physics in Kühlungsborn, Germany, in a case study for the same period we found a very clear quasi 5-day signal in the distribution of the minor constituents and particularly in the water vapor mixing ratio in middle to high northern latitudes in the late spring and summer season. A similar finding is valid for the southern hemisphere half a year later. The variations of the minor constituents are triggered by the wind system resulting from the dynamical part of the model. The calculations satisfactorily reproduce the observed water vapor concentrations. In particular, the annual variation including intraannual variations is reflected by the model. We discuss the findings in terms of dynamics and chemistry. Copyright 2008 by the American Geophysical Union."
"6602576807;6701348241;6602738250;55885662200;9233141200;8667844900;14029002800;7202419956;","Trends, seasonal variability and dominant NOx source derived from a ten year record of NO2 measured from space",2008,"10.1029/2007JD009021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42549164152&doi=10.1029%2f2007JD009021&partnerID=40&md5=36ce85ec052ab8fa96fdade4a2457e8c","For the period 1996-2006, global distributions of tropospheric nitrogen dioxide (NO2) have been derived from radiances measured with the satellite instruments GOME (Global Ozone Monitoring Experiment) and SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY). A statistical analysis is applied to derive trends and seasonal variability for this period on a global scale. The time series of the monthly NO2 columns for these ten years have been fitted with a linear function superposed on an annual seasonal cycle on a grid with a spatial resolution of 1° by 1°. We see significant reductions (up to 7% per year) in NO2 in Europe and parts of the eastern United States, and a strong increase in Asia, most particularly in China (up to 29% per year) but also in Iran and Russia. By comparing the data with the cloud information derived from the same satellite observations, the contribution of lightning to the total column of NO2 is estimated. The estimated NO2 from lightning is, especially in the tropics, in good agreement with lightning flash rate observations from space. The satellite observed seasonal variability of NO2 generally correlates well with independent observations and estimates of the seasonal cycle of specific NOx sources. Source categories considered are anthropogenic (fossil fuel and biofuel), biomass burning, soil emissions and lightning. Using the characteristics of the seasonal variability of these source categories, the dominant source of NOx emissions has been identified on a global scale and on a 1° by 1° grid. Copyright 2008 by the American Geophysical Union."
"6507224579;7004247643;","Sea ice, high-latitude convection, and equable climates",2008,"10.1029/2007GL032286","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849144241&doi=10.1029%2f2007GL032286&partnerID=40&md5=c94d65550dec57d3a8d104d62f516004","It is argued that deep atmospheric convection might occur during winter in ice-free high-latitude oceans, and that the surface radiative warming effects of the clouds and water vapor associated with this winter convection could keep high-latitude oceans ice-free through polar night. In such an ice-free high-latitude ocean the annual-mean SST would be much higher and the seasonal cycle would be dramatically reduced - making potential implications for equable climates manifest. The constraints that atmospheric heat transport, ocean heat transport, and CO2 concentration place on this mechanism are established. These ideas are investigated using the NCAR column model, which has state-of-the-art atmospheric physics parameterizations, high vertical resolution, a full seasonal cycle, a thermodynamic sea ice model, and a mixed layer ocean. Copyright 2008 by the American Geophysical Union."
"24477694300;8147766700;7006212411;34769585100;57203053317;57208121852;7007172001;7202586843;16032925200;35459699300;35406457100;7007061674;7406645661;7403189961;","Coatings and their enhancement of black carbon light absorption in the tropical atmosphere",2008,"10.1029/2007JD009042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42649093881&doi=10.1029%2f2007JD009042&partnerID=40&md5=7b44b9812d0c9c5c527672d2f955ea94","Black carbon (BC) is the dominant aerosol absorber of solar radiation in the atmosphere and is an important component of anthropogenic climate forcing. BC's role is strongly dependent on its physical state, which can influence the way that BC particles may act as ice and cloud nuclei, as well as the way they interact with solar radiation. In situ measurements made with a single-particle soot photometer flown on a NASA high-altitude research aircraft show the mass and size of individual BC particles in the tropics, as well as their propensity to be found mixed with additional materials. Mie theory was used to connect observed light scattering off BC particles to the optical effects of coatings on the particles. The observations indicate that as BC from ground-based emission sources rises in altitude to the lower stratosphere, coatings on BC particles become both thicker and more prevalent, while BC mass mixing ratios decrease dramatically from their values near the ground. Coatings enhance light absorption by the ambient BC column by at least 30%. These results reveal the microphysical state of BC in the atmosphere while providing important constraints for models evaluating BC's role in climate change. Copyright 2008 by the American Geophysical Union."
"6507033203;14048222100;35232671500;","Multiscale geostatistical analysis of AVHRR, SPOT-VGT, and MODIS global NDVI products",2008,"10.1016/j.rse.2007.05.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38049054713&doi=10.1016%2fj.rse.2007.05.008&partnerID=40&md5=99e1a2363e72b48e0013bc8505a440ea","Global NDVI data are routinely derived from the AVHRR, SPOT-VGT, and MODIS/Terra earth observation records for a range of applications from terrestrial vegetation monitoring to climate change modeling. This has led to a substantial interest in the harmonization of multisensor records. Most evaluations of the internal consistency and continuity of global multisensor NDVI products have focused on time-series harmonization in the spectral domain, often neglecting the spatial domain. We fill this void by applying variogram modeling (a) to evaluate the differences in spatial variability between 8-km AVHRR, 1-km SPOT-VGT, and 1-km, 500-m, and 250-m MODIS NDVI products over eight EOS (Earth Observing System) validation sites, and (b) to characterize the decay of spatial variability as a function of pixel size (i.e. data regularization) for spatially aggregated Landsat ETM+ NDVI products and a real multisensor dataset. First, we demonstrate that the conjunctive analysis of two variogram properties - the sill and the mean length scale metric - provides a robust assessment of the differences in spatial variability between multiscale NDVI products that are due to spatial (nominal pixel size, point spread function, and view angle) and non-spatial (sensor calibration, cloud clearing, atmospheric corrections, and length of multi-day compositing period) factors. Next, we show that as the nominal pixel size increases, the decay of spatial information content follows a logarithmic relationship with stronger fit value for the spatially aggregated NDVI products (R2 = 0.9321) than for the native-resolution AVHRR, SPOT-VGT, and MODIS NDVI products (R2 = 0.5064). This relationship serves as a reference for evaluation of the differences in spatial variability and length scales in multiscale datasets at native or aggregated spatial resolutions. The outcomes of this study suggest that multisensor NDVI records cannot be integrated into a long-term data record without proper consideration of all factors affecting their spatial consistency. Hence, we propose an approach for selecting the spatial resolution, at which differences in spatial variability between NDVI products from multiple sensors are minimized. This approach provides practical guidance for the harmonization of long-term multisensor datasets. © 2007 Elsevier Inc. All rights reserved."
"25627687800;","The weather and climate of the tropics part 4 - Forecasting significant cloud and associated weather",2008,"10.1002/wea.125","https://www.scopus.com/inward/record.uri?eid=2-s2.0-54949114714&doi=10.1002%2fwea.125&partnerID=40&md5=77e199f95b03157203c3f7aa27a6975f",[No abstract available]
"10243650000;8979277400;7201485519;7007021059;10241462700;6603196127;7102857642;","Towards understanding cloud response in atmospheric GCMs: The use of tendency diagnostics",2008,"10.2151/jmsj.86.69","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42449148943&doi=10.2151%2fjmsj.86.69&partnerID=40&md5=5b41d215e42dcb11618e14d01d98552a","In climate change projections, inter-model differences in cloud feedback have been identified as the largest source of uncertainty. The source terms of the cloud condensate tendency equation (CCTD) are expected to be useful diagnostics to better understand the different cloud responses to a CO2 increase in GCMs. To demonstrate the idea, analysis of the CCTD response to CO2 doubling is presented using two versions of a climate model with different climate sensitivities of 6.2°C ('HS' version) and 4.1°C ('LS' version). The model's response to CO2 doubling is characterized with a marked difference in the cloud feedback between the two versions, which is consistent with the cloud response in the southern middle latitudes: cloud decreases in the HS version and increases in the LS version. Analysis of the source terms reveals that the difference in cloud response is attributable to the ice sedimentation process. The results also suggest the importance of the vertical cloud ice profile which controls the ice sedimentation response to a CO2 increase, indicating the potential for providing constraints on the aspect of cloud feedback. © 2008, Meteorological Society of Japan."
"7404142321;8946494600;","Initial tendencies of cloud regimes in the Met Office unified model",2008,"10.1175/2007JCLI1900.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849106829&doi=10.1175%2f2007JCLI1900.1&partnerID=40&md5=c2625ffc9fa005f3943fa00856bc78d8","The Met Office unified forecast-climate model is used to compare the properties of simulated climatological cloud regimes with those produced in short-range forecasts initialized from operational analyses. The regimes are defined as principal clusters of joint cloud-top pressure-optical depth histograms. In general, the cloud regime properties are found to be similar at all forecast times, including the climatological mean. This suggests that weaknesses in the representation of fast local processes are responsible for errors in the simulation of the cloud regimes. The increased horizontal resolution of the model used for numerical weather prediction generally has little impact on the cloud regimes, although the simulation of tropical shallow cumulus is improved, while the relative frequency of tropical deep convection and cirrus compare less favorably with observations. Analysis of the initial temperature tendency profiles for each cloud regime indicates that some of the initial temperature tendency which leads to a systematic bias in the model climatology, is associated with a particular cloud regime."
"23486332900;6603749140;7004169476;7403159332;7404105326;","Towards constraining climate sensitivity by linear analysis of feedback patterns in thousands of perturbed-physics GCM simulations",2008,"10.1007/s00382-007-0280-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38849206844&doi=10.1007%2fs00382-007-0280-7&partnerID=40&md5=b51e1bd983cad7fb6d92acb1840893bd","A linear analysis is applied to a multi-thousand member ""perturbed physics"" GCM ensemble to identify the dominant physical processes responsible for variation in climate sensitivity across the ensemble. Model simulations are provided by the distributed computing project, climate prediction.net. A principal component analysis of model radiative response reveals two dominant independent feedback processes, each largely controlled by a single parameter change. The leading EOF was well correlated with the value of the entrainment coefficient - a parameter in the model's atmospheric convection scheme. Reducing this parameter increases high vertical level moisture causing an enhanced clear sky greenhouse effect both in the control simulation and in the response to greenhouse gas forcing. This effect is compensated by an increase in reflected solar radiation from low level cloud upon warming. A set of 'secondary' cloud formation parameters partly modulate the degree of shortwave compensation from low cloud formation. The second EOF was correlated with the scaling of ice fall speed in clouds which affects the extent of cloud cover in the control simulation. The most prominent feature in the EOF was an increase in longwave cloud forcing. The two leading EOFs account for 70% of the ensemble variance in λ - the global feedback parameter. Linear predictors of feedback strength from model climatology are applied to observational datasets to estimate real world values of the overall climate feedback parameter. The predictors are found using correlations across the ensemble. Differences between predictions are largely due to the differences in observational estimates for top of atmosphere shortwave fluxes. Our validation does not rule out all the strong tropical convective feedbacks leading to a large climate sensitivity. © Springer-Verlag 2007."
"6602178158;8670472000;12764954600;7003908632;6603341831;6602926744;7402504552;7202162685;6701915334;12763461700;55637266800;12764661900;7004279859;7102636922;23482558100;6701832491;7003455444;55708356600;7003875148;6701728368;","An evaluation of Arctic cloud and radiation processes during the SHEBA year: Simulation results from eight Arctic regional climate models",2008,"10.1007/s00382-007-0286-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38849133494&doi=10.1007%2fs00382-007-0286-1&partnerID=40&md5=bda09486c9a6bd0898daa221f487bb44","Eight atmospheric regional climate models (RCMs) were run for the period September 1997 to October 1998 over the western Arctic Ocean. This period was coincident with the observational campaign of the Surface Heat Budget of the Arctic Ocean (SHEBA) project. The RCMs shared common domains, centred on the SHEBA observation camp, along with a common model horizontal resolution, but differed in their vertical structure and physical parameterizations. All RCMs used the same lateral and surface boundary conditions. Surface downwelling solar and terrestrial radiation, surface albedo, vertically integrated water vapour, liquid water path and cloud cover from each model are evaluated against the SHEBA observation data. Downwelling surface radiation, vertically integrated water vapour and liquid water path are reasonably well simulated at monthly and daily timescales in the model ensemble mean, but with considerable differences among individual models. Simulated surface albedos are relatively accurate in the winter season, but become increasingly inaccurate and variable in the melt season, thereby compromising the net surface radiation budget. Simulated cloud cover is more or less uncorrelated with observed values at the daily timescale. Even for monthly averages, many models do not reproduce the annual cycle correctly. The inter-model spread of simulated cloud-cover is very large, with no model appearing systematically superior. Analysis of the co-variability of terms controlling the surface radiation budget reveal some of the key processes requiring improved treatment in Arctic RCMs. Improvements in the parameterization of cloud amounts and surface albedo are most urgently needed to improve the overall performance of RCMs in the Arctic. © Springer-Verlag 2007."
"22975069200;6701764148;9842184600;7202170177;7203085045;7007160862;57190749913;","Observations of cloud, radiation, and surface forcing in the equatorial eastern Pacific",2008,"10.1175/2007JCLI1757.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849120610&doi=10.1175%2f2007JCLI1757.1&partnerID=40&md5=470912eb6f6c169f07128f57fe614dbc","In this paper the authors report on a study of cloud and surface flux processes in the tropical eastern Pacific Ocean based on a series of ship-based cloud and flux measurements made during fall (1999-2002) and spring (2000-02) maintenance cruises along the 95° and 110°W Tropical Atmosphere Ocean (TAO) buoy lines between 8°S and 12°N. The year-to-year and seasonal variabilities of many of the meteorological and oceanic means are relatively small. However, notable seasonal, variability is found in the northern branch of the intertropical convergence zone, the north-south sea surface temperature gradient, and heat fluxes north of the equator. In the fall, the strengthening of the north-south SST contrast enhances convective activity (more and deeper clouds, precipitation, southerly inflow) in the area around 6°N, 95°W; diurnal variations of low cloud fraction were weak. Spring cloud fraction varied significantly over the diurnal cycle with substantially lower cloud fraction during the day south of 5°N. Relatively low average cloud-base heights around the equator are due to chilling of the marine boundary layer over the cold tongue. Cloud radiative forcing strongly correlates with cloud fraction; clouds in the observation region cool the surface by about 40 W m-2 in both seasons. Cloud forcing estimates from the ship data, the TAO buoys, and International Satellite Cloud Climatology Project (ISCCP) products were combined to form a consensus observation dataset that is compared with the second NCEP reanalysis (NCEP-2) and 40-yr ECMWF Re-Analysis (ERA-40) cloud forcing values. The reanalysis products were within 10 W m-2 of the observations for IR cloud forcing but substantially overestimated the solar cloud forcing, particularly in spring. © 2008 American Meteorological Society."
"7202216319;57206006874;57203055233;","Effects of nonlinearity on convectively forced internal gravity waves: Application to a gravity wave drag parameterization",2008,"10.1175/2007JAS2255.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41049115176&doi=10.1175%2f2007JAS2255.1&partnerID=40&md5=55f316ba2e526da979312cd48d5a03e7","In the present study, the authors propose a way to include a nonlinear forcing effect on the momentum flux spectrum of convectively forced internal gravity waves using a nondimensional numerical model (NDM) in a two-dimensional framework. In NDM, the nonlinear forcing is represented by nonlinear advection terms multiplied by the nonlinearity factor-(NF) of the thermally induced internal gravity waves for a given specified diabatic forcing. It was found that the magnitudes of the waves and resultant momentum flux above the specified forcing decrease with increasing NF due to cancellation between 'the two forcing mechanisms. Using the momentum flux spectrum obtained by the NDM simulations with various NFs, a scale factor for the momentum flux, normalized by the momentum flux induced by diabatic forcing alone, is formulated as a function of NF. Inclusion of the nonlinear forcing effect into current convective gravity wave drag (GWD) parameterizations, which consider diabatic forcing alone by multiplying the cloud-top momentum flux spectrum by the scale factor, is proposed. An updated convective GWD parameterization using the scale factor is implemented into the NCAR Whole Atmosphere Community Climate Model (WACCM). The 10-yr simulation results, compared with those by the original convective GWD parameterization considering diabatic forcing alone, showed that the magnitude of the zonal-mean cloud-top momentum flux is reduced for wide range of phase speed spectrum by about 10%, except in the middle latitude storm-track regions where the cloud-top momentum flux is amplified. The zonal drag forcing is determined largely by the wave propagation condition under the reduced magnitude of the cloud-top momentum flux, and its magnitude decreases in many regions, but there are several areas of increasing drag forcing, especially in the tropical upper mesosphere and lower thermosphere. © 2008 American Meteorological Society."
"55977336000;16637291100;7501855361;","The influence of changes in cloud cover on recent surface temperature trends in the Arctic",2008,"10.1175/2007JCLI1681.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849087929&doi=10.1175%2f2007JCLI1681.1&partnerID=40&md5=7e3555d1dde0d704cae223dabdd6601e","A method is presented to assess the influence of changes in Arctic cloud cover on the surface temperature trend, allowing for a more robust diagnosis of causes for surface warming or cooling. Seasonal trends in satellite-derived Arctic surface temperature under clear-, cloudy-, and all-sky conditions are examined for the period 1982-2004. The satellite-derived trends are in good agreement with trends in the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis product and surface-based weather station measurements in the Arctic. Surface temperature trends under clear and cloudy conditions have patterns similar to the all-sky trends, though the magnitude of the trends under cloudy conditions is smaller than those under clear-sky conditions, illustrating the negative feedback of clouds on the surface temperature trends. The all-sky surface temperature trend is divided into two parts: the first part is a linear combination of the surface temperature trends under clear and cloudy conditions; the second part is caused by changes in cloud cover as a function of the clear-cloudy surface temperature difference. The relative importance of these two components is different in the four seasons, with the first part more important in spring, summer, and autumn, but with both parts being equally important in winter. The contribution of biases in satellite retrievals is also evaluated. © 2008 American Meteorological Society."
"6701346974;6507017020;7202208382;","Evaluation of the simulated interannual and subseasonal variability in an AMIP-style simulation using the CSU multiscale modeling framework",2008,"10.1175/2007JCLI1630.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849150834&doi=10.1175%2f2007JCLI1630.1&partnerID=40&md5=f74f495a653ba891c381755f0beee5bc","The Colorado State University (CSU) Multiscale Modeling Framework (MMF) is a new type of general circulation model (GCM) that replaces the conventional parameterizations of convection, clouds, and boundary layer with a cloud-resolving model (CRM) embedded into each grid column. The MMF has been used to perform a 19-yr-long Atmospheric Model Intercomparison Project-style simulation using the 1985-2004 sea surface temperature (SST) and sea ice distributions as prescribed boundary conditions. Particular focus has been given to the simulation of the interannual and subseasonal variability. The annual mean climatology is generally well simulated. Prominent biases include excessive precipitation associated with the Indian and Asian monsoon seasons, precipitation-deficits west of the Maritime Continent and over Amazonia, shortwave cloud effect biases west of the subtropical continents due to insufficient stratocumulus clouds, and longwave cloud effect biases due to overestimation of high cloud amounts, especially in the tropics. ne geographical pattern of the seasonal cycle of precipitation is well reproduced, although the seasonal variance is considerably overestimated mostly because of the excessive monsoon precipitation mentioned above. The MMF does a good job of reproducing the interannual variability in terms of the spatial structure and magnitude of major anomalies associated with El Niño-Southern Oscillation (ENSO). The subseasonal variability of tropical climate associated with the Madden-Julian oscillation (MJO) and equatorially trapped waves are particular strengths of the simulation. The wavenumber-frequency power spectra of the simulated outgoing longwave radiation (OLR), precipitation rate, and zonal wind at 200 and 850 mb for time scales in the range of 2-96 days compare very well to the spectra derived from observations, and show a robust MJO and Kelvin and Rossby waves with phase speeds similar to those observed. The geographical patterns of the MJO and Kelvin wave-filtered OLR variance for summer and winter seasons are well simulated; however, the variances tend to be overestimated by as much as 50%. The observed seasonal and interannual variations of the strength of the MJO are also well reproduced. The physical realism of the simulated marine stratocumulus clouds is demonstrated by an analysis of the composite diurnal cycle of cloud water content, longwave (IR) cooling, vertical velocity variance, rainfall, and subcloud vertical velocity skewness. The relationships between vertical velocity variance, IR cooling, and negative skewness all suggest that, despite the coarse numerical grid of the CRM, the simulated clouds behave in a manner consistent with the understanding of the stratocumulus dynamics. In the stratocumulus-to-cumulus transition zone, the diurnal cycle of the inversion layer as simulated by the MMF also bears a remarkable resemblance to in situ observations. It is demonstrated that in spite of the coarse spacing of the CRM grid used in the current version of MMF, the bulk of vertical transport of water in the MMF is carried out by the circulations explicitly represented on the CRM grid rather than by the CRM's subgrid-scale parameterization. © 2008 American Meteorological Society."
"36058191800;55916149100;55991851900;7004372110;","Climatic response to anthropogenic sulphate aerosols versus well-mixed greenhouse gases from 1850 to 2000 AD in CLIMBER-2",2008,"10.1111/j.1600-0889.2007.00318.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38349014019&doi=10.1111%2fj.1600-0889.2007.00318.x&partnerID=40&md5=1d8af0880af5cee3b011365830edd688","The Earth system model CLIMBER-2 is extended by a scheme for calculating the climatic response to anthropogenic sulphur dioxide emissions. The scheme calculates the direct radiative forcing, the first indirect cloud albedo effect, and the second indirect cloud lifetime effect induced by geographically resolved sulphate aerosol burden. The simulated anthropogenic sulphate aerosol burden in the year 2000 amounts to 0.47 TgS. The best guesses for the radiative forcing due to the direct effect are -0.4 W m-2 and for the decrease in short-wave radiation due to all aerosol effects -0.8 W m-2. The simulated global warming by 1 K from 1850 to 2000 caused by anthropogenic greenhouse gases reduces to 0.6 K when the sulphate aerosol effects are included. The model's hydrological sensitivity of 4%/K is decreased by the second indirect effect to 0.8%/K. The quality of the geographically distributed climatic response to the historic emissions of sulphur dioxide and greenhouse gases makes the extended model relevant to computational efficient investigations of future climate change scenarios. © 2007 The Authors Journal compilation © 2007 Blackwell Munksgaard."
"57201410408;11939816400;","Climatology of the Sierra Nevada mountain-wave events",2008,"10.1175/2007MWR1902.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44449083802&doi=10.1175%2f2007MWR1902.1&partnerID=40&md5=0bd24fd07cc301d8c2ac9adaa6da1a7a","This note presents a satellite-based climatology of the Sierra Nevada mountain-wave events. The data presented were obtained by detailed visual inspection of visible satellite imagery to detect mountain lee-wave clouds based on their location, shape, and texture. Consequently, this climatology includes only mountain-wave events during which sufficient moisture was present in the incoming airstream and whose amplitude was large enough to lead to cloud formation atop mountain-wave crests. The climatology is based on data from two mountain-wave seasons in the 1999-2001 period. Mountain-wave events are classified in two types according to cloud type as lee-wave trains and single wave clouds. The frequency of occurrence of these two wave types is examined as a function of the month of occurrence (October-May) and region of formation (north, middle, south, or the entire Sierra Nevada range). Results indicate that the maximum number of mountain-wave events in the lee of the Sierra Nevada occurs in the month of April. For several months, including January and May, frequency of wave events displays substantial interannual variability. Overall, trapped lee waves appear to be more common, in particular in the lee of the northern sierra. A single wave cloud on the lee side of the mountain range was found to be a more common wave form in the southern Sierra Nevada. The average wavelength of the Sierra Nevada lee waves was found to lie between 10 and 15 km, with a minimum at 4 km and a maximum at 32 km. © 2008 American Meteorological Society."
"12040335900;7404653593;8284622100;23480586700;23028717700;","Spectral analysis of weekly variation in PM10 mass concentration and meteorological conditions over China",2008,"10.1016/j.atmosenv.2007.09.075","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38649141166&doi=10.1016%2fj.atmosenv.2007.09.075&partnerID=40&md5=a5bdb509599ffa160fe55c1c0bf7fe79","This study investigates the region-dependent anthropogenic weekly variation in air pollutants and its relationship with the meteorological conditions over China for the summers of 2001-2005. Spectral analysis was applied to the local daily observations of PM10 (aerosol particulate matter with a diameter <10 μm) mass concentrations and precipitation from 31 ground stations, reanalysis estimates of regional atmospheric variables, and satellite retrievals of clouds. Our analysis shows that the 6-8-day variance of PM10 concentrations from the periodogram is closely correlated with the mean PM10 concentration, which may depend on the size (population) and geographical setting of a city, its prevailing climatic conditions, and the type/degree of human activities. We define normalized variance as the ratio of the 6-8-day to 2-14-day variance of PM10 concentrations, possibly indicating the relative anthropogenic signal to the noise of natural weather variability. The normalized variance of PM10 concentrations has a distinct regional rainfall distribution from that of the mean PM10 concentration in China. As compared to regions with lower normalized variance of PM10 concentrations, the regions with higher normalized variance generally show higher normalized variance of rainfall events, 1000 hPa wind speeds, sea-level pressure, size spectrum and phase of cloud particles, cloud optical depth, and cloud top pressure. Our results confirm the presence of the interaction between PM10 and the meteorological conditions in the boundary layer, and suggest a possible link of cloud formation to PM10 on a weekly scale. © 2007 Elsevier Ltd. All rights reserved."
"7402207328;7102987843;","Incorporating organic soil into a global climate model",2008,"10.1007/s00382-007-0278-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38849152178&doi=10.1007%2fs00382-007-0278-1&partnerID=40&md5=8f24a5380f24ff31a90e105fc0ec953c","Organic matter significantly alters a soil's thermal and hydraulic properties but is not typically included in land-surface schemes used in global climate models. This omission has consequences for ground thermal and moisture regimes, particularly in the high-latitudes where soil carbon content is generally high. Global soil carbon data is used to build a geographically distributed, profiled soil carbon density dataset for the Community Land Model (CLM). CLM parameterizations for soil thermal and hydraulic properties are modified to accommodate both mineral and organic soil matter. Offline simulations including organic soil are characterized by cooler annual mean soil temperatures (up to ∼2.5°C cooler for regions of high soil carbon content). Cooling is strong in summer due to modulation of early and mid-summer soil heat flux. Winter temperatures are slightly warmer as organic soils do not cool as efficiently during fall and winter. High porosity and hydraulic conductivity of organic soil leads to a wetter soil column but with comparatively low surface layer saturation levels and correspondingly low soil evaporation. When CLM is coupled to the Community Atmosphere Model, the reduced latent heat flux drives deeper boundary layers, associated reductions in low cloud fraction, and warmer summer air temperatures in the Arctic. Lastly, the insulative properties of organic soil reduce interannual soil temperature variability, but only marginally. This result suggests that, although the mean soil temperature cooling will delay the simulated date at which frozen soil begins to thaw, organic matter may provide only limited insulation from surface warming. © Springer-Verlag 2007."
"8900751100;7406671641;","Statistical and dynamical assessment of vegetation feedbacks on climate over the boreal forest",2008,"10.1007/s00382-008-0368-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52549132944&doi=10.1007%2fs00382-008-0368-8&partnerID=40&md5=4177bd9fa0b7d6aa9c67996047b6ae89","Vegetation feedbacks over Asiatic Russia are assessed through a combined statistical and dynamical approach in a fully coupled atmosphere-ocean-land model, FOAM-LPJ. The dynamical assessment is comprised of initial value ensemble experiments in which the forest cover fraction is initially reduced over Asiatic Russia, replaced by grass cover, and then the climatic response is determined. The statistical feedback approach, adopted from previous studies of ocean-atmosphere interactions, is applied to compute the feedback of forest cover on subsequent temperature and precipitation in the control simulation. Both methodologies indicate a year-round positive feedback on temperature and precipitation, strongest in spring and moderately substantial in summer. Reduced boreal forest cover enhances the surface albedo, leading to an extended snow season, lower air temperatures, increased atmospheric stability, and enhanced low cloud cover. Changes in the hydrological cycle include diminished transpiration and moisture recycling, supporting a reduction in precipitation. The close agreement in sign and magnitude between the statistical and dynamical feedback assessments testifies to the reliability of the statistical approach. An additional statistical analysis of monthly vegetation feedbacks over Asiatic Russia reveals a robust positive feedback on air temperature of similar quantitative strength in two coupled models, FOAM-LPJ and CAM3-CLM3, and the observational record. © Springer-Verlag 2008."
"57203939102;7405437902;8906055900;57212209888;8578247700;","Net radiation and turbulent energy exchanges over a non-glaciated coastal area on King George Island during four summer seasons",2008,"10.1017/S095410200700082X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38149126510&doi=10.1017%2fS095410200700082X&partnerID=40&md5=266aab5fef166e4560cbaa61a4e3b8d8","Recently, the Antarctic Peninsula has received more attention due to the pronounced warming in that region. Non-glaciated coastal areas on the Peninsula can be significant energy sources for the atmosphere when they are exposed during summer despite the high degree of cloud associated with the frequent passage of low pressure systems. An eddy covariance system was established in December 2002 to evaluate the turbulent energy exchanges between the atmosphere and a non-glaciated coastal area on King George Island. Monthly average downward shortwave radiation was less than 210 Wm-2 in summer. Due to the low albedo of 0.12, monthly average net radiation reached &gt; 130 Wm-2, a magnitude that was significantly larger than the reported magnitudes of &lt; ∼70 Wm-2 at glaciated areas with a high albedo on the Peninsula. The sum of monthly average sensible heat (&lt; 64 Wm-2) and latent heat (&lt; 20 Wm-2) fluxes amounted up to ∼80 Wm-2, which was an order of magnitude larger than those at glaciated areas on the Antarctic Peninsula. Given that non-glaciated areas should be enlarged if the warming continues, more attention may need to be paid to the role of non-glaciated areas in the local climate to predict climate change on the Antarctic Peninsula. © 2008 Antarctic Science Ltd."
"55492209000;7004814501;35467186900;7003926380;","On the differences in storm rainfall from hurricanes Isidore and Lili. Part II: Water budget",2008,"10.1175/2007WAF2005120.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41949109104&doi=10.1175%2f2007WAF2005120.1&partnerID=40&md5=fd2b0f4055aa4204b354c46f1d51ddc4","Part I of this two-part paper examined the satellite-derived rainfall accumulation and rain potential history of Hurricanes Isidore and Lili (2002). This paper (Part II) uses analyses from tile Navy Operational Global Atmospheric Prediction System (NOGAPS) to examine the water budget and environmental parameters and their relationship to the precipitation for these two storms. Factors other than storm size are found to account for large volumetric differences in storm total rainfall between Lili and Isidore. It is found that the horizontal moisture convergence was crucial to the initiation and maintenance of Isidore's intense rainfall before and during its landfall. When the storm was over the ocean, the ocean moisture flux (evaporation) was the second dominant term among the moisture sources that contribute to precipitation. During Isidore's life history, the strong horizontal moisture flux convergence corresponded to the large storm total precipitable water. The large difference in budget-derived stored cloud ice and liquid water between Isidore and Lili is corroborated from Tropical Rainfall Measuring Mission (TRMM) measurements. During Isidore's landfall, the decrease in environmental water vapor contributed to rainfall in a very small amount. These results indicate the importance of the environmental precipitable water and moisture convergence and ocean surface moisture flux in generating Isidore's large rainfall volume and inland flooding as compared with Lili's water budget history. Both the moisture convergence and ocean flux were small for Lili. © 2008 American Meteorological Society."
"14067392400;6701845806;7102271194;7202772927;","An integrated high-resolution hydrometeorological modeling testbed using LIS and WRF",2008,"10.1016/j.envsoft.2007.05.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34748856119&doi=10.1016%2fj.envsoft.2007.05.012&partnerID=40&md5=97bf566b53de22aa2b0fbd16b61c16fa","Interactions between the atmosphere and the land surface have considerable influences on weather and climate. Coupled land-atmosphere systems that can realistically represent these interactions are thus critical for improving our understanding of the atmosphere-biosphere exchanges of energy, water, and their associated feedbacks. NASA's Land Information System (LIS) is a high-resolution land data assimilation system that integrates advanced land surface models, high-resolution satellite and observational data, data assimilation techniques, and high performance computing tools. LIS has been coupled to the Weather Research and Forecasting (WRF) model, enabling a high-resolution land-atmosphere modeling system. Synthetic simulations using the coupled LIS-WRF system demonstrates the interoperable use of land surface models, high-resolution land surface data and other land surface modeling tools through LIS. Real case study simulations for a June 2002 International H2O Project (IHOP) day is conducted by executing LIS first in an uncoupled manner to generate high-resolution soil moisture and soil temperature initial conditions. During the case study period, the land surface (LIS) and the atmospheric (WRF) models are executed in a coupled manner using the LIS-WRF system. The results from the simulations illustrate the impact of accurate, high-resolution land surface conditions on improving the prediction of clouds and precipitation. Thus, the coupled LIS-WRF system provides a testbed to enable studies in improving our understanding and predictability of regional and global water and energy cycles. © 2007 Elsevier Ltd. All rights reserved."
"7004250903;23013601900;23011787700;","Spring and summer severe weather reports over the midwest as a function of convective mode: A preliminary study",2008,"10.1175/2007WAF2006120.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41949114010&doi=10.1175%2f2007WAF2006120.1&partnerID=40&md5=7255a344a073afee0534da7560e2e9dc","Radar data during the period 1 April-31 August 2002 were used to classify all convective storms occurring in a 10-state region of the central United States into nine predominant morphologies, and the severe weather reports associated with each morphology were then analyzed. The morphologies included three types of cellular convection (individual cells, clusters of cells, and broken squall lines), five types of linear systems (bow echoes, squall lines with trailing stratiform rain, lines with leading stratiform rain, lines with parallel stratiform rain, and lines with no stratiform rain), and nonlinear systems. Because linear systems with leading and line-parallel stratiform rainfall were relatively rare in the 2002 sample of 925 events, 24 additional cases of these morphologies from 1996 and 1997 identified by Parker and Johnson were included in the sample. All morphologies were found to pose some risk of severe weather, but substantial differences existed between the number and types of severe weather reports and the different morphologies. Normalizing results per event, nonlinear systems produced the fewest reports of hail, and were relatively inactive for all types of severe weather compared to the other morphologies. Linear systems generated large numbers of reports from all categories of severe weather. Among linear systems, the hail and tornado threat was particularly enhanced in systems having leading and line-parallel stratiform rain. Bow echoes were found to produce far more severe wind reports than any other morphology. The flooding threat was largest in broken lines and linear systems having trailing and line-parallel stratiform rain. Cellular storms, despite much smaller areal coverage, also were abundant producers of severe hail and tornadoes, particularly in broken squall lines. © 2008 American Meteorological Society."
"12242422700;35614191800;","Response of the tropical Pacific to changes in extratropical clouds",2008,"10.1007/s00382-007-0363-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52549087820&doi=10.1007%2fs00382-007-0363-5&partnerID=40&md5=65313c48845b875f5f948a54f844e44e","A decrease in cloud cover over higher latitudes - a decrease in the extratropical albedo-especially over the Southern Ocean, can result in an extratropical and tropical warming with the intensity of the equatorial cold tongues in the Pacific and Atlantic basins decreasing. These results, obtained by means of a coupled ocean-atmosphere model of intermediate complexity that allow the prescription of atmospheric cloud cover, are relevant to future global warming, and also to conditions during the Pliocene some 3 million years ago. The mechanisms responsible for the response of the tropics to changes in the extra-tropics include atmospheric and oceanic connections. This tropical adjustment can be interpreted from the constraint of a balanced heat budget for the ocean: A change in the albedo of the Southern Hemisphere causes the ocean to lose less heat there, so that it has to gain less heat in the tropics. As a consequence the cold tongues are reduced, particularly in the eastern Pacific where a decrease in the zonal tilt of the equatorial thermocline significantly weakens the east-west sea surface temperature gradient. The total adjustment time scale of the equatorial Pacific to the extratropical perturbation is of the order of interdecadal to centennial time scales, and thus represents a new mechanism of rapid climate change. © Springer-Verlag 2008."
"7004057920;57213428259;","Clouds modulate terrestrial carbon uptake in a midlatitude hardwood forest",2008,"10.1029/2007GL032398","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849083738&doi=10.1029%2f2007GL032398&partnerID=40&md5=133e17678425ee22ef8d9b7629eb0eac",[No abstract available]
"14035836100;7003591311;","Quantifying error in the radiative forcing of the first aerosol indirect effect",2008,"10.1029/2007GL032667","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849126797&doi=10.1029%2f2007GL032667&partnerID=40&md5=84b4d363c0d73963cfe85dd44e476e91","Anthropogenic aerosol plays a major role in the Earth's radiation budget, particularly via effects on clouds. The Intergovernmental Panel on Climate Change lists the uncertainty in aerosol modification of cloud albedo as the largest unknown in the radiative forcing of climate change. Common measures of aerosol effects on clouds, Aerosol-Cloud Interaction (ACI = -∂lnre/∂lnα, where re is drop size and a aerosol burden), cover an enormous range and, as these measures are now being used as parameterizations in global-scale models, this has large implications for radiative forcing. We quantify the relationship between radiative forcing and changes in ACI over the range of values found in the literature. Depending on anthropogenic aerosol perturbation, radiative forcing ranges from -3 to -10 W m-2 for each 0.05 increment in ACI. Narrowing uncertainty in measures of ACI to an accuracy of 0.05 would place estimated cloud radiative forcing on a sounder footing. Copyright 2008 by the American Geophysical Union."
"6602974799;7004091561;7005002049;13406040100;7005968859;7003591311;","Secondary organic aerosol yields from cloud-processing of isoprene oxidation products",2008,"10.1029/2007GL031828","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849124168&doi=10.1029%2f2007GL031828&partnerID=40&md5=fb2d4beb8181c4682e8475be7217f704","While there is a growing understanding from laboratory studies of aqueous phase chemical processes that lead to secondary organic aerosol (SOA) formation in cloud droplets (SOAdrop), the contribution of aqueous phase chemistry to atmospheric SOA burden is yet unknown. Using a parcel model including a multiphase chemical mechanism, we show that SOAdrop carbon yields (Yc) from isoprene (1) depend strongly on the initial volatile organic carbon (VOC)NOx ratio resulting in 42% &gt; Yc &gt; 0.4% over the atmospherically-relevant range of 0.25 &lt; VOCNOx &lt; 100; (2) increase with increasing cloud-contact time; (3) are less affected by cloud liquid water content, pH, and droplet number. (4) The uncertainty associated with gas/particle-partitioning of semivolatile organics introduces a relative error of -50% ≤ ΔYc &lt; +100%. The reported yields can be applied to air quality and climate models as is done with SOA formed on/in concentrated aerosol particles (SOAaer). Copyright 2008 by the American Geophysical Union."
"23977679300;7202628826;56920790500;23977795400;8503380800;23977685500;7103353990;15840467900;57194628631;7102054073;","Regional and seasonal variations of the Twomey indirect effect as observed by the ATSR-2 satellite instrument",2008,"10.1029/2007GL031394","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849124169&doi=10.1029%2f2007GL031394&partnerID=40&md5=6b3f392610392b5c3a26ddace17bfd9b","We use satellite observations of aerosol optical depth τa and cloud effective radius re from the ATSR-2 instrument in 1997 to investigate the Twomey indirect effect (IE, -∂ 1n re/∂ 1n τa ) in regions of continental outflow. We generally find a negative correlation between τa and re, with the strongest inverse relationships downwind of Africa. North American and eastern Asian continental outflow exhibits a strong seasonal dependence, as expected. Global values for IE range from 0.10 to 0.16, consistent with theoretical predictions. Downwind of Africa, we find that the IE is unphysically high but robust (r = -0.85) during JJA associated with high aerosol loading, and attribute this tentatively to the Twomey hypothesis accounting only for a limited number of physical properties of aerosols. Copyright 2008 by the American Geophysical Union."
"7004559579;7003886299;","Factorial method as a tool for estimating the relative contribution to precipitation of cloud microphysical processes and environmental conditions: Method and application",2008,"10.1029/2007JD008960","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41649098011&doi=10.1029%2f2007JD008960&partnerID=40&md5=21a774782d6c4807d055927fdbc1f0ee","The factorial experiment method is presented as a tool for evaluating the sensitivity of precipitation to changes in atmospheric thermodynamic conditions and cloud microphysical characteristics in mixed phase convective clouds. As an example, the method is adopted here for analysis of the sensitivity of precipitation to changes in various parameters using simulations with the Tel Aviv University 2D (TAU 2D) cloud model. The cloud model was run in 80 scenarios in order to determine the relative sensitivity of precipitation in eastern Mediterranean winter mixed phase convective clouds to changes in cloud condensation nuclei (CCN) concentration, parameterization of ice formation mechanisms and initial atmospheric thermodynamic conditions. When these parameters act synergistically to suppress precipitation (by increasing the concentration of CCN and of small ice crystals and reducing the water vapor mixing ratio), for the cases simulated here, a decrease of about 2°C in the entire profile of the ambient temperature while keeping the relative humidity constant has the same contribution to precipitation suppression as an increase of about 400 cm-3 in the CCN concentration. It is shown that under the warmest and most humid atmospheric thermodynamic conditions simulated here, the suppression of precipitation is affected more by the increased CCN than by the ice generation processes, whereas in colder atmospheric conditions the reverse is true. For a given atmospheric sounding the time of rain initiation strongly depends on the CCN concentrations. The role of ice generation begins to affect precipitation at a later stage when the cloud is more mature. Copyright 2008 by the American Geophysical Union."
"55574223716;13406672500;","Solar radiation budget and radiative forcing due to aerosols and clouds",2008,"10.1029/2007JD008434","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41649115469&doi=10.1029%2f2007JD008434&partnerID=40&md5=87082b6b60cfda4f0477671233c30c08","This study integrates global data sets for aerosols, cloud physical properties, and shortwave radiation fluxes with a Monte Carlo Aerosol-Cloud-Radiation (MACR) model to estimate both the surface and the top-of-atmosphere (TOA) solar radiation budget as well as atmospheric column solar absorption. The study also quantifies the radiative forcing of aerosols and that of clouds. The observational input to MACR includes data from the Multiangle Imaging Spectroradiometer (MISR) for aerosol optical depths, single scattering albedos, and asymmetry factors; satellite retrieved column water vapor amount; the Total Ozone Mapping Spectrometer (TOMS) total ozone amount; and cloud fraction and cloud optical depth from the Cloud and Earth's Radiant Energy System (CERES) cloud data. The present radiation budget estimates account for the diurnal variation in cloud properties. The model was validated against instantaneous, daily and monthly solar fluxes from the ground-based Baseline Surface Radiation Network (BSRN) network, the Global Energy Balance Archive (GEBA) surface solar flux data, and CERES TOA measurements. The agreement between simulated and observed values are within experimental errors, for all of the cases considered here: instantaneous fluxes and monthly mean fluxes at stations around the world and TOA fluxes and cloud forcing for global annual mean and zonal mean fluxes; in addition the estimated aerosol forcing at TOA also agrees with other observationally derived estimates. Overall, such agreements suggest that global data sets of aerosols and cloud parameters released by recent satellite experiments (MISR, MODIS and CERES) meet the required accuracy to use them as input to simulate the radiative fluxes within instrumental errors. Last, the atmospheric solar absorption derived in this study should be treated as an improved estimate when compared with earlier published studies. The main source of improvement in the present estimate is the use of global distribution of observed parameters for model input such as aerosols and clouds. The agreement between simulated and observed solar fluxes at the surface supports our conclusion that the present estimate is an improvement over previous studies. MACR with the global input data was used to simulate the global and regional solar radiation budget, aerosol radiative forcing and cloud radiative forcing for a 3-year period from 2000 to 2002. We estimate the planetary albedo for a 3-year average to be 28.9 ± 1.2% to be compared with CERES estimate of 28.6% and ERBE's estimate of 29.6%. Without clouds (including aerosols) the planetary albedo is only 15.0 ± 0.6%. The global mean TOA shortwave cloud forcing is -47.5 ± 4 W m-2, comparing well with the CERES and ERBE estimates of -46.5 and -48 W m-2, respectively. The clear-sky 2 atmospheric absorption is 72 ± 3 W m-2, and the surface absorption is 218 ± 4 W m-2. Clouds in all-sky conditions enhance atmospheric absorption from 72 ± 3 W m-2 to 79 ± 5 W m-2 and decrease surface solar absorption from 218 ± 4 W m-2 to 164 ± 6 W m-2. The present estimate of 79 W m-2 for all-sky solar absorption is much larger than the Intergovernmental Panel on Climate Change (2001) values of about 67 W m-2. Most of the increased atmospheric solar absorption is due to improved treatment of aerosol absorption (backed by surface based aerosol network and chemical transport models) and water vapor spectroscopic data. The global mean clear-sky aerosol (both natural and anthropogenic) radiative forcing at the TOA and the surface are -6.0 ± 1 W m-2 and -11.0 ± 2 W m-2, respectively. In the presence 2 of clouds the aerosol radiative forcing is -3.0 ± 1 W m-2 (at TOA) and -7.0 ± 2 W m-2 (at the surface). The study also documents the significant regional variations in the solar radiation budget and radiative forcing of aerosols and clouds. Copyright 2008 by the American Geophysical Union."
"7402501507;7102084129;7409322518;7402295755;56224155200;23992492600;","Midweek increase in U.S. summer rain and storm heights suggests air pollution invigorates rainstorms",2008,"10.1029/2007JD008623","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41649092520&doi=10.1029%2f2007JD008623&partnerID=40&md5=cc9b1516ad8a256543a157f14ecefdda","Tropical Rainfall Measuring Mission (TRMM) satellite estimates of summertime rainfall over the southeast U.S. are found on average to be significantly higher during the middle of the work week than on weekends, attributable to a midweek intensification of afternoon storms and an increase in area with detectable rain. TRMM radar data show a significant midweek increase in the echo-top heights reached by afternoon storms. Weekly variations in model-reanalysis wind patterns over the region are consistent with changes in convection implied by the satellite data. Weekly variations in rain gauge averages are also consistent with the satellite estimates, though possibly smaller in amplitude. A midweek decrease of rainfall over the nearby Atlantic is also seen. EPA measurements of surface particulate concentrations show a midweek peak over much of the U.S. These observations are consistent with the theory that anthropogenic air pollution suppresses cloud-drop coalescence and early rainout during the growth of thunderstorms over land, allowing more water to be carried above the 0°C isotherm, where freezing yields additional latent heat, invigorating the storms and producing large ice hydrometeors. The enhanced convection induces regional convergence, uplifting and an overall increase of rainfall. Compensating downward air motion suppresses convection over the adjacent ocean areas. Pre-TRMM-era data suggest that the weekly cycle only became strong enough to be detectable beginning in the 1980's. Rain-gauge data also suggest that a weekly cycle may have been detectable in the 1940's, but with peak rainfall on Sunday or Monday, possibly explained by the difference in composition of aerosol pollution at that time. This ""weekend effect"" may thus offer climate researchers an opportunity to study the regional climate-scale impact of aerosols on storm development and monsoon-like circulation. Copyright 2008 by the American Geophysical Union."
"55729083100;7403968239;","What causes the excessive response of clear-sky greenhouse effect to El Niño warming in Community Atmosphere Models?",2008,"10.1029/2007JD009247","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41649122121&doi=10.1029%2f2007JD009247&partnerID=40&md5=a1abcd3a194829ae029472d6143b4dbe","To diagnose the causes of an excessive response of the clear-sky greenhouse effect to El Niño warming in the Community Atmosphere Models (CAMs), the response of both water vapor and temperature to El Niño warming in the models is examined as a function of height. The percentage response of water vapor to El Niño warming in the models is considerably stronger than the response in the NCEP reanalysis in the middle and upper troposphere (700-300 mbar). The maximum discrepancy with NCEP data at 500 mbar reaches 18%/K in CAM3. The discrepancy in the temperature response between the models and NCEP data at all tropospheric levels is within 0.3 K/K, with the maximum discrepancy occurring in the immediate neighborhood of 600 mbar. The comparison between the models and ERA-40 reanalysis leads to the similar results. Employing a radiative model, we have calculated the contributions of the excessive water vapor response in the middle and upper troposphere and the contributions from the differences in the lapse rate response to the discrepancies seen in the clear-sky greenhouse effect. The results confirm that the main cause of the excessive response of the clear-sky greenhouse effect is an excessive response of water vapor in the middle and upper troposphere. The excessive response of upper tropospheric water vapor is found to be accompanied with an excessive response in the upper cloud cover and vertical motion. Biases in both phases of ENSO contribute to these excessive responses to ENSO. © 2008 by the American Geophysical Union."
"7201472576;6603341831;8670472000;6602178158;","Evaluation of regional cloud climate simulations over Scandinavia using a 10-year NOAA Advanced Very High Resolution Radiometer cloud climatology",2008,"10.1029/2007JD008658","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40949127858&doi=10.1029%2f2007JD008658&partnerID=40&md5=47877cdf21d6be20fa8abe910b514218","A satellite-derived (NOAA Advanced Very High Resolution Radiometer) cloud climatology over the Scandinavian region covering the period 1991-2001 has been used to evaluate the performance of cloud simulations of the Swedish Meteorological and Hydrological Institute Rossby Centre regional climate model (RCA3). Several methods of adapting the satellite and model data sets to allow a meaningful comparison were applied. RCA3-simulated total cloud cover was shown to agree within a few percent of the satellite-retrieved cloud amounts on seasonal and annual timescales. However, a substantial imbalance between the respective RCA3 contributions from low-, medium- and high-level clouds was seen. The differences from satellite-derived contributions were +2.4% for high-level clouds, -5.2% for medium-level clouds and +4.0% for low-level clouds. In addition, an overrepresentation of cloud categories with high optical thicknesses was seen for all vertical cloud groups, particularly during the summer season. Some specific features of the geographical distribution of cloudiness were also noticed. Most pronounced were the excess of cloud amounts over the Scandinavian mountain range and a deficit leeward of the mountains. The overall results simply problems with the RCA3-modeled surface radiation budget components by causing reduced incoming solar radiation and increased downwelling longwave radiation. Copyright 2008 by the American Geophysical Union."
"8212745300;6603031730;8212745200;","Trends in vegetation NDVI from 1 km AVHRR data over Canada for the period 1985-2006",2008,"10.1080/01431160802302090","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57049131561&doi=10.1080%2f01431160802302090&partnerID=40&md5=800a30dd8780da20d2b0ae8c56d3ea3c","Long-term changes in the Normalized Difference Vegetation Index (NDVI) have been evaluated in several studies but results have not been conclusive due to differences in data processing as well as the length and time of the analysed period. In this research a newly developed 1 km Advanced Very High Resolution Radiometer (AVHRR) satellite data record for the period 1985-2006 was used to rigorously evaluate NDVI trends over Canada. Furthermore, climate and land cover change as potential causes of observed trends were evaluated in eight sample regions. The AVHRR record was generated using improved geolocation, cloud screening, correction for sun-sensor viewing geometry, atmospheric correction, and compositing. Results from both AVHRR and Landsat revealed an increasing NDVI trend over northern regions where comparison was possible. Overall, 22% of the vegetated area in Canada was found to have a positive NDVI trend based on the Mann-Kendal test at the 95% confidence level. Of these, 40% were in northern ecozones. The mean absolute difference of NDVI measurements between AVHRR and Landsat data was <7%. When compared with results from other studies, similar trends were found over northern areas, while in southern regions the results were less consistent. Local assessment of potential causes of trends in each region revealed a stronger influence of climate in the north compared to the south. Southern regions with strong positive trends appeared to be most influenced by land cover change."
"12801992200;","A note on the effect of GCM tuning on climate sensitivity",2008,"10.1088/1748-9326/3/1/014001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43149094019&doi=10.1088%2f1748-9326%2f3%2f1%2f014001&partnerID=40&md5=7d795bf07d24bf95b14fac921b0c9347","A tuning experiment is carried out with the Community Atmosphere Model version 3, where the top-of-the-atmosphere radiative balance is tuned to agree with global satellite estimates from ERBE and CERES, respectively, to investigate if the climate sensitivity of the model is dependent upon which of the datasets is used. The tuning is done through alterations of cloud parameters that affect, for instance, the model cloud water content, but the difference in cloud water content between the two model configurations is found to be negligible compared to the wide spread of the same quantity in a number of state-of-the-art GCMs. The equilibrium climate sensitivities of the two model configurations differ by ca.0.24K, and both lie well within the range of present estimates of climate sensitivity in different GCMs. This indicates that it is possible to tune the model to either of the two satellite datasets without drastically changing the climate sensitivity. However, the study illustrates that the climate sensitivity is a product of choices of parameter values that are not well restricted by observations, which allows for a certain degree of arbitrariness in the estimates of climate sensitivity. © 2008 IOP Publishing Ltd."
"57203049177;7201485519;","Tropospheric adjustment induces a cloud component in CO2 forcing",2008,"10.1175/2007JCLI1834.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849113474&doi=10.1175%2f2007JCLI1834.1&partnerID=40&md5=ae752ef3dd0e6f4e046ddf9428cf6ede","The radiative forcing of CO2 and the climate feedback parameter are evaluated in several climate models with slab oceans by regressing the annual-mean global-mean top-of-atmosphere radiative flux against the annual-mean global-mean surface air temperature change ΔT following a doubling of atmospheric CO2 concentration. The method indicates that in many models there is a significant rapid tropospheric adjustment to CO2 leading to changes in cloud. and reducing the effective radiative forcing, in a way analogous to the indirect and semidirect effects of aerosol. By contrast, in most models the cloud feedback is small, defined as the part of the change that evolves with ΔT. Comparison with forcing evaluated by fixing sea surface conditions gives qualitatively similar results for the cloud components of forcing, both globally and locally. Tropospheric adjustment to CO2 may be responsible for some of the model spread in equilibrium climate sensitivity and could affect time-dependent climate projections."
"56611366900;7005862399;57208698992;19638935200;","Dispersion bias, dispersion effect, and the aerosol-cloud conundrum",2008,"10.1088/1748-9326/3/4/045021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651127549&doi=10.1088%2f1748-9326%2f3%2f4%2f045021&partnerID=40&md5=78781302b6239418467ec85d7cef6482","This work examines the influences of relative dispersion (the ratio of the standard deviation to the mean radius of the cloud droplet size distribution) on cloud albedo and cloud radiative forcing, derives an analytical formulation that accounts explicitly for the contribution from droplet concentration and relative dispersion, and presents a new approach to parameterize relative dispersion in climate models. It is shown that inadequate representation of relative dispersion in climate models leads to an overestimation of cloud albedo, resulting in a negative bias of global mean shortwave cloud radiative forcing that can be comparable to the warming caused by doubling CO2 in magnitude, and that this dispersion bias is likely near its maximum for ambient clouds. Relative dispersion is empirically expressed as a function of the quotient between cloud liquid water content and droplet concentration (i.e., water per droplet), yielding an analytical formulation for the first aerosol indirect effect. Further analysis of the new expression reveals that the dispersion effect not only offsets the cooling from the Twomey effect, but is also proportional to the Twomey effect in magnitude. These results suggest that unrealistic representation of relative dispersion in cloud parameterization in general, and evaluation of aerosol indirect effects in particular, is at least in part responsible for several outstanding puzzles of the aerosol-cloud conundrum: for example, overestimation of cloud radiative cooling by climate models compared to satellite observations; large uncertainty and discrepancy in estimates of the aerosol indirect effect; and the lack of interhemispheric difference in cloud albedo. © 2008 IOP Publishing Ltd."
"57205867148;8731430700;35220400000;57210518852;8875844200;","Evaluating the present-day simulation of clouds, precipitation, and radiation in climate models",2008,"10.1029/2007JD009334","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71949105949&doi=10.1029%2f2007JD009334&partnerID=40&md5=db0a1cc845bcaeb7d9f18f50a139d2c9","This paper describes a set of metrics for evaluating the simulation of clouds, radiation, and precipitation in the present-day climate. As with the skill scores used to measure the accuracy of short-term weather forecasts, these metrics are low-order statistical measures of agreement with relevant, well-observed physical quantities. The metrics encompass five statistical summaries computed for five physical quantities (longwave, shortwave, and net cloud radiative effect, projected cloud fraction, and surface precipitation rate) over the global climatological annual cycle. Agreement is measured against two independent observational data sets. The metrics are computed for the models that participated in the Coupled Model Intercomparison Project phase 3, which formed the basis for the Fourth Assessment of the IPCC. Model skill does not depend strongly on the data set used for verification, indicating that observational uncertainty does not limit the ability to assess model simulations of these fields. No individual model excels in all scores though the ""IPCC mean model,"" constructed by averaging the fields produced by all the CMIP models, performs particularly well across the board. This skill is due primarily to the individual model errors being distributed on both sides of the observations, and to a lesser degree to the models having greater skill at simulating large-scale features than those near the grid scale. No measure of model skill considered here is a good predictor of the strength of cloud feedbacks under climate change. The model climatologies, observational data sets, and metric scores are available on-line."
"57203053317;6603315547;35800064100;7102011023;7102781936;","Cirrus cloud formation and ice supersaturated regions in a global climate model",2008,"10.1088/1748-9326/3/4/045022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951046238&doi=10.1088%2f1748-9326%2f3%2f4%2f045022&partnerID=40&md5=24ff7797a3973e66a3d2bb436ca13342","At temperatures below 238 K, cirrus clouds can form by homogeneous and heterogeneous ice nucleation mechanisms. ECHAM5 contains a two-moment cloud microphysics scheme and permits cirrus formation by homogeneous freezing of solution droplets and heterogeneous freezing on immersed dust nuclei. On changing the mass accommodation coefficient, a, of water vapor on ice crystals from 0.5 in the standard ECHAM5 simulation to 0.006 as suggested by previous laboratory experiments, the number of ice crystals increases by a factor of 14, as a result of the delayed relaxation of supersaturation. At the same time, the ice water path increases by only 29% in the global annual mean, indicating that the ice crystals are much smaller in the case of low α. As a consequence, the short wave and long wave cloud forcing at the top of the atmosphere increase by 15 and 18 W m-2, respectively. Assuming heterogeneous freezing caused by immersed dust particles instead of homogeneous freezing, the effect is much weaker, decreasing the global annual mean short wave and long wave cloud forcing by 2.7 and 4.7 W m-2. Overall, these results provide little support, if any, for kinetic growth limitation of ice particles (i.e. a very low α). © 2008 IOP Publishing Ltd."
"6507224579;7004247643;","A high-latitude convective cloud feedback and equable climates",2008,"10.1002/qj.211","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41949091634&doi=10.1002%2fqj.211&partnerID=40&md5=a2fb8fe86f04cc2aa2baec205619e19c","A convective cloud feedback on extratropical surface temperatures is identified in a zonally averaged two-level atmospheric model. The model contains simplified parametrizations for convection, precipitation, and clouds, and a long-wave radiation scheme that explicitly depends on carbon dioxide, water vapour, and cloud fraction. The convective cloud feedback occurs if the extratropical surface temperature is increased enough to initiate strong atmospheric convection. This results in a change from low to high clouds and from negative to neutral or positive cloud radiative forcing, which further warms the surface and leads to more convection. This positive feedback activates as the CO2 concentration is increased and leads to a climate solution with high boundary-layer temperatures, convection at mid and high latitudes, and an Equator to Pole temperature difference that is reduced by 8-10°C. The reduction in Equator to Pole temperature difference is due to changes in high-latitude local heat balance and occurs despite decreased meridional heat transport. The convective cloud feedback also leads to multiple equilibria and hysteresis with respect to CO2 and other model variables, although these results may be due to the simplicity of the model. The possible connection of the behaviour of the model at high CO2 with equable climates is considered. Copyright © 2008 Royal Meteorological Society."
"35264611800;7003591311;7101846027;7004885872;24341429500;7006572336;57196499374;","Aerosol-cloud relationships in continental shallow cumulus",2008,"10.1029/2007JD009354","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50849112002&doi=10.1029%2f2007JD009354&partnerID=40&md5=01ee3f99d25f008b0e226ab8a0ce7615","Aerosol-cloud relationships are derived from 14 warm continental cumuli cases sampled during the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) by the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. Cloud droplet number concentration is clearly proportional to the subcloud accumulation mode aerosol number concentration. An inverse correlation between cloud top effective radius and subcloud aerosol number concentration is observed when cloud depth variations are accounted for. There are no discernable aerosol effects on cloud droplet spectral dispersion; the averaged spectral relative dispersion is 0.30 ± 0.04. Aerosol-cloud relationships are also identified from comparison of two isolated cloud cases that occurred under different degrees of anthropogenic influence. Cloud liquid water content, cloud droplet number concentration, and cloud top effective radius exhibit subadiabaticity resulting from entrainment mixing processes. The degree of LWC subadiabaticity is found to increase with cloud depth. Impacts of subadiabaticity on cloud optical properties are assessed. It is estimated that owing to entrainment mixing, cloud LWP, effective radius, and cloud albedo are decreased by 50-85%, 5-35%, and 2-26%, respectively, relative to adiabatic values of a plane-parallel cloud. The impact of subadiabaticity on cloud albedo is largest for shallow clouds. Results suggest that the effect of entrainment mixing must be accounted for when evaluating the aerosol indirect effect. Copyright 2008 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",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049103969&partnerID=40&md5=7798de3313b101059dd0adfadacc7c40","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-infřared retrievals from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) are used to estimate the vertical profile of r<inf>e</inf>. MODIS r<inf>e</inf> 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."
"25941200000;","Overlap of fractional cloud for radiation calculations in GCMs: A global analysis using CloudSat and CALIPSO data",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049086705&partnerID=40&md5=838fbc36f65fb28ffd2c6b3220e7d86e","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>* ∼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 ℒ<inf>cf</inf>* was estimated at 2 to 3 W m-2 km-1."
"6701511324;6603271938;35392584500;","Noise due to the Monte Carlo independent-column approximation: Short-term and long-term impacts in ECHAM5",2008,"10.1002/qj.231","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44349156996&doi=10.1002%2fqj.231&partnerID=40&md5=2ee80a8c97bca1cfaf86fcac079a9d95","The Monte Carlo independent-column approximation (McICA), as a method for computing domain-average radiative fluxes, allows a flexible treatment of unresolved cloud structure, and is unbiased with respect to the full independent-column approximation, but its flux estimates contain conditional random noise. In our previous study with the ECHAM5 atmospheric general-circulation model with prescribed sea-surface temperatures (SSTs), McICA noise caused a slight reduction in low-cloud fraction. Here, we first demonstrate that this feature originates from an immediate, nonlinear response of precipitation formation to McICA's random errors in radiative-heating rates, and is subsequently amplified by a radiative feedback. We then study the long-term impacts of McICA noise on climate in ECHAM5 simulations employing a mixed-layer ocean model. The use of interactive rather than prescribed SST somewhat amplifies the reduction in low-cloud fraction, which contributes to an overall warming of simulated climate with increasing McICA noise. For a typical implementation of McICA, the global-mean 2 m air temperature is 0.33 K higher than for a low-noise reference simulation. A 0.1 μm systematic increase in cloud-droplet effective radius re causes a similar global-mean warming (0.31 K), with generally similar spatial patterns. However, in the eastern tropical Pacific, McICA noise has locally larger effects than the uniform perturbation in re. It is concluded that the climatic impacts of McICA noise mainly represent a straightforward response to the systematic perturbation in the surface and top-of-atmosphere energy budget related to the initial reduction in low cloudiness. Copyright © 2008 Royal Meteorological Society."
"55601602900;55601746100;43961752000;55712683400;","Analytic model of upper tropospheric clouds in the tropical Hadley cell",2008,"10.1186/BF03352784","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41849123467&doi=10.1186%2fBF03352784&partnerID=40&md5=06f183c65ec1dadcab67fa226738a7c4","We have developed a two-dimensional analytic model that describes the behavior of upper tropospheric clouds in the tropical Hadley cell. The behavior of the model is characterized by two dimensionless parameters: one is proportional to the temperature lapse rate, and the other is relevant to the initial altitude of the cloud particles. We derived analytic expressions for the motion and evaporation of the cloud particles and calculate various cloud properties, such as the cloudiness and the column water content. We found that the outflow from the convective regions spreads out and generates a cirrus layer whose coverage has a maximum at the tropopause: the cloudiness is as large as 0.5-1 in the vicinity of the tropopause for small cloud particles with radii of less than 5 μm. We suggest that the thin cirrus clouds observed near the tropopause in the tropic region are formed by the advection of cloud particles supplied from the ITCZ. Because of its simpleness, the present model may play a role in diagnosing cloud properties in climate models that are used to study climate changes over a long time span. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB."
"7004368198;7005412286;7201706659;6602101632;7004914081;23013023700;26648162300;6701544275;14819186100;6602724321;14119516800;7005828307;12792311100;6603850404;7004608274;14012502000;24076731100;6701797047;7006280684;","Deriving a sea surface temperature record suitable for climate change research from the along-track scanning radiometers",2008,"10.1016/j.asr.2007.07.041","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36448950146&doi=10.1016%2fj.asr.2007.07.041&partnerID=40&md5=ceb442d8065ad741fc8b249c6875e7be","We describe the approach to be adopted for a major new initiative to derive a homogeneous record of sea surface temperature for 1991-2007 from the observations of the series of three along-track scanning radiometers (ATSRs). This initiative is called (A)RC: (Advanced) ATSR Re-analysis for Climate. The main objectives are to reduce regional biases in retrieved sea surface temperature (SST) to less than 0.1 K for all global oceans, while creating a very homogenous record that is stable in time to within 0.05 K decade -1 , with maximum independence of the record from existing analyses of SST used in climate change research. If these stringent targets are achieved, this record will enable significantly improved estimates of surface temperature trends and variability of sufficient quality to advance questions of climate change attribution, climate sensitivity and historical reconstruction of surface temperature changes. The approach includes development of new, consistent estimators for SST for each of the ATSRs, and detailed analysis of overlap periods. Novel aspects of the approach include generation of multiple versions of the record using alternative channel sets and cloud detection techniques, to assess for the first time the effect of such choices. There will be extensive effort in quality control, validation and analysis of the impact on climate SST data sets. Evidence for the plausibility of the 0.1 K target for systematic error is reviewed, as is the need for alternative cloud screening methods in this context. © 2007 COSPAR."
"26643440200;","Scientific data stewardship of international satellite cloud climatology project B1 global geostationary observations",2008,"10.1117/1.3043461","https://www.scopus.com/inward/record.uri?eid=2-s2.0-61349121520&doi=10.1117%2f1.3043461&partnerID=40&md5=cec16084fae0c271d8f20d8eb6f39669","The International Satellite Cloud Climatology Project (ISCCP) B1 data was recently rescued by NOAA's National Climatic Data Center (NCDC). ISCCP B1 data are geostationary imagery from satellites worldwide which are subsampled to 10 km and 3 hourly resolution. These data were unusable given the disarray of format documentation and lack of software for reading the data files. After developing access software, assessing data quality, and removing infrared window calibration biases, the data have been used for research in studying tropical cyclones and is available for other topics, such as rainfall and cloud cover. This resulted not only in valuable scientific data for weather and climate research but also in important lessons learned for future archiving of scientific data records. The effort also exemplifies principles of scientific data stewardship. © 2008 Society of Photo-Optical Instrumentation Engineers."
"35887706900;7501627905;","Cloud-rain interactions: As complex as it gets",2008,"10.1088/1748-9326/3/4/045018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749143492&doi=10.1088%2f1748-9326%2f3%2f4%2f045018&partnerID=40&md5=a63d19981976ff85ac22c563008bd0b5","The effect of aerosol on clouds and precipitation poses one of the largest uncertainties in the estimation of the anthropogenic contribution to climate change. Often the local effect of aerosol on the radiation field both directly and indirectly by changing cloud properties can be more than an order of magnitude larger than the effect of greenhouse gases. Recent works also suggest that some of the local aerosol effects such as the heating of the atmosphere from aerosol absorption can have a large-scale impact. However, due to the inhomogeneous distribution and short lifetime of aerosols, the inherent complexity of cloud microphysics and dynamics, and the strong coupling of aerosol-related processes with meteorology, it is still challenging to estimate the overall effect that aerosols exert on the radiation field and climate. The climatic effect of aerosol-cloud interaction is not limited to the radiation field. By changing the cloud microphysical and radiative properties, aerosols may affect precipitation amount and patterns. Precipitation processes are located at the end of the 'food chain' of aerosol-cloud processes. Rain rates and patterns are the final result of many cloud processes and feedbacks, some of which are affected by aerosols. Changes in precipitation patterns could lead to serious hydrological consequences. For example if the same amount of rain precipitates in shorter time, e.g. heavier rain rates, the probability of floods increases, a larger portion of the water is drained by rapid surface run-off and the amount of water penetrating the subsurface and available as an underground reservoir of drinking water is reduced. Moreover, the subsurface water distribution depends heavily on topography and geomorphology. Therefore small changes in the timing or location of precipitation may dramatically alter the surface and subsurface water distribution and affect the water reservoir. In studying aerosol-cloud-precipitation interactions, the largest challenge is determining how to separate the effect of meteorological processes from aerosol effects. Simple statistical correlations between observed or retrieved aerosol and cloud properties do not imply causality. With the help of sophisticated cloud numerical models where certain variables or processes can be controlled in sensitivity simulations, aerosol-precipitation casual relationships could be examined in specific conditions. However, it is not always clear whether such aerosol-precipitation relationships seen in the model could be applied to more general meteorological scenarios. Aerosol-cloud-precipitation interaction is a highly complex problem involving processes and feedbacks that span the size range from an aerosol particle (10-7m) to a cloud (103m), and all the way to synoptic scale systems (106m). These feedbacks determine whether a droplet, initiated at a size of few microns, could grow within the time scale of a cloud's lifetime to reach a raindrop size of a few mm, and whether this raindrop will fall all the way to the surface and be available as fresh water. These feedbacks include dynamic and thermodynamic processes of precipitating particles, which in conjunction with other processes determine the micro and macrophysical properties of the cloud and hence determine the cloud's effect on the regional radiation field and local climate. Thus, aerosol, cloud, precipitation and radiation interactions are inherently linked, and need to be addressed as a single problem when attempting to better understand human-induced changes in the climate system. Focus on Aerosol Precipitation Contents Drizzle rates versus cloud depths for marine stratocumuli A B Kostinski Characteristics of vertical velocity in marine stratocumulus: comparison of large eddy simulations with observations Huan Guo, Yangang Liu, Peter H Daum, Gunnar I Senum and Wei-Kuo Tao Dispersion bias, dispersion effect, and the aerosol-cloud conundrum Yangang Liu, Peter H Daum, Huan Guo and Yiran Peng The impact of smoke from forest fires on the spectral dispersion of cloud droplet size distributions in the Amazonian region J A Martins and M A F Silva Dias A conceptual model for the link between Central American biomass burning aerosols and severe weather over the south central United States Jun Wang, Susan C van den Heever and Jeffrey S Reid © 2008 IOP Publishing Ltd."
"55543656200;55545601500;7403282069;7406683894;35180216600;56239378700;26427916400;7202418453;","Deriving Marine-Boundary-Layer Lapse Rate from Collocated CALIPSO, MODIS, and AMSR-E Data to Study Global Low-Cloud Height Statistics",2008,"10.1109/LGRS.2008.2002024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85008020299&doi=10.1109%2fLGRS.2008.2002024&partnerID=40&md5=f7e5c0073e14920fdbfc8f6aada66067","Global cloud-top height statistics of marine-boundary-layer clouds are derived from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Level 2 aerosol and cloud layer products. The boundary-layer lapse rate in the northeast region of the Pacific Ocean is investigated using sea surface temperature (SST) data from the Advanced Microwave Scanning Radiometer-EOS (AMSR-E), cloud-top temperature data from the Moderate Resolution Imaging Spectroradiometer (MODIS), and cloud-top height data from CALIPSO. Based on the lapse rate derived from the combined CALIPSO/MODIS/AMSR-E measurements, cloud-top heights in regions within CALIPSO tracks are derived from AMSR SST and MODIS cloud temperature to test the validity of this approach. For homogeneous low-level clouds, the results agree with the cloud-top height from the collocated CALIPSO cloud-top height measurements. These results suggest that the database of derived lapse rates from the combined measurements can be applied to study cloud-top height climate statistics using the MODIS and AMSR data when CALIPSO observations are not available. © 2008 IEEE"
"7202233375;56294871100;","A cloud-based reconstruction of surface solar radiation trends for Australia",2008,"10.1007/s00704-006-0287-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39449094385&doi=10.1007%2fs00704-006-0287-8&partnerID=40&md5=3762eb1c7b2ea13cff9c1b9c65cde778","Despite its importance to climate change, reliable and calibrated measurements of solar radiation are available only after 1992 for Australia. In this study we extend the data base from 1967 to 2004 by the development of a cloud-based solar radiation model. Results show no significant change in the majority of stations, although slightly more than one quarter of the stations report a significant decrease of solar radiation with a maximum of just less than one percent per decade. Trend analyses also detect an upturn in many of the southern stations in the late eighties which appear to relate to changes in middle and high cloud cover. © Springer-Verlag 2007."
"6603021857;7102976560;","Maintenance of polar stratospheric clouds in a moist stratosphere",2008,"10.5194/cp-4-69-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41549097797&doi=10.5194%2fcp-4-69-2008&partnerID=40&md5=ab6cc76c6ff0a5824334ec1b71eef41a","Previous work has shown that polar stratospheric clouds (PSCs) could have acted to substantially warm high latitude regions during past warm climates such as the Eocene (55 Ma). Using a simple model of stratospheric water vapor transport and polar stratospheric cloud (PSC) formation, we investigate the dependence of PSC optical depth on tropopause temperature, cloud microphysical parameters, stratospheric overturning, and tropospheric methane. We show that PSC radiative effects can help slow removal of water from the stratosphere via self-heating. However, we also show that the ability of PSCs to have a substantial impact on climate depends strongly on the PSC particle number density and the strength of the overturning circulation. Thus even a large source of stratospheric water vapor (e.g. from methane oxidation) will not result in substantial PSC radiative effects unless PSC ice crystal number density is high compared to most current observations, and stratospheric overturning (which modulates polar stratospheric temperatures) is low. These results are supported by analysis of a series of runs of the NCAR WACCM model with methane concentrations varying up to one thousand times present levels."
"57203053317;","Global anthropogenic aerosol effects on convective clouds in ECHAM5-HAM",2008,"10.5194/acp-8-2115-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42149133079&doi=10.5194%2facp-8-2115-2008&partnerID=40&md5=09b4a98f93787119117ff91e369edf20","Aerosols affect the climate system by changing cloud characteristics in many ways. They act as cloud condensation and ice nuclei and may have an influence on the hydrological cycle. Here we investigate aerosol effects on convective clouds by extending the double-moment cloud microphysics scheme developed for stratiform clouds, which is coupled to the HAM double-moment aerosol scheme, to convective clouds in the ECHAM5 general circulation model. This enables us to investigate whether more, and smaller cloud droplets suppress the warm rain formation in the lower parts of convective clouds and thus release more latent heat upon freezing, which would then result in more vigorous convection and more precipitation. In ECHAM5, including aerosol effects in large-scale and convective clouds (simulation ECHAM5-conv) reduces the sensitivity of the liquid water path increase with increasing aerosol optical depth in better agreement with observations and large-eddy simulation studies. In simulation ECHAM5-conv with increases in greenhouse gas and aerosol emissions since pre-industrial times, the geographical distribution of the changes in precipitation better matches the observed increase in precipitation than neglecting microphysics in convective clouds. In this simulation the convective precipitation increases the most suggesting that the convection has indeed become more vigorous."
"7004159166;","A GCM study of organic matter in marine aerosol and its potential contribution to cloud drop activation",2008,"10.5194/acp-8-709-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39449120068&doi=10.5194%2facp-8-709-2008&partnerID=40&md5=5ebd6db39b4499e3a0847ffeb9cbbe6c","With the global aerosol-climate model ECHAM5HAM we investigate the potential influence of organic aerosol originating from the ocean on aerosol mass and chemical composition and the droplet concentration and size of marine clouds. We present sensitivity simulations in which the uptake of organic matter in the marine aerosol is prescribed for each aerosol mode with varying organic mass and mixing state, and with a geographical distribution and seasonality similar to the oceanic emission of dimethyl sulfide. Measurements of aerosol mass, aerosol chemical composition and cloud drop effective radius are used to assess the representativity of the model initializations. Good agreement with the measurements is obtained when organic matter is added to the Aitken, accumulation and coarse modes simultaneously. Representing marine organics in the model leads to higher cloud drop number concentrations and thus smaller cloud drop effective radii, and this improves the agreement with measurements. The mixing state of the organics and the other aerosol matter, i.e. internal or external depending on the formation process of aerosol organics, is an important factor for this. We estimate that globally about 75 Tg C yr-1 of organic matter from marine origin enters the aerosol phase, with comparable contributions from primary emissions and secondary organic aerosol formation."
"20436169300;","Drizzle rates versus cloud depths for marine stratocumuli",2008,"10.1088/1748-9326/3/4/045019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749083668&doi=10.1088%2f1748-9326%2f3%2f4%2f045019&partnerID=40&md5=65b4c95913eb70e1cbe2101ad601a174","Marine stratocumuli make a major contribution to Earth's radiation budget. Drizzle in such clouds can greatly affect their albedo, lifetime and fractional coverage, so drizzle rate prediction is important. Here we examine a question: does a drizzle rate (R) depend on cloud depth (H) and/or drop number concentration n in a simple way? This question was raised empirically in several recent publications and an approximate H3/n dependence was observed. Here we suggest a simple explanation for H3 scaling from viewing the drizzle rate as a sedimenting volume fraction (f) of water drops (radius r) in air, i.e.R = fu(r), where u is the fall speed of droplets at the cloud base. Both R and u have units of speed. In our picture, drizzle drops begin from condensation growth on the way up and continue with accretion on the way down. The ascent contributes H () and the descent H2 () to the drizzle rate. A more precise scaling formula is also derived and may serve as a guide for parameterization in global climate models. The number concentration dependence is also discussed and a plausibility argument is given for the observed n-1 dependence of the drizzle rate. Our results suggest that deeper stratocumuli have shorter washout times. © IOP Publishing Ltd."
"23047834100;","Validation of a mixed-layer closure. II: Observational tests",2008,"10.1002/qj.183","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41949112640&doi=10.1002%2fqj.183&partnerID=40&md5=4ed8dff57e196cc3e8cd989a7b64cf34","Data from the DYCOMS2 observational campaign are used to test a mixed-layer entrainment model presented previously by the author. The model is extended to include the effects of drizzle precipitation and radiative warming from the surface. The most consistent results are obtained under the assumption that the mixed-layer top is unsaturated, that is, the cloud top is below the top of the turbulent flow. With this assumption, the predicted entrainment rates lie near those obtained by Faloona et al., and are well correlated with them, but are sensitive to the evaluation of temperature and moisture jumps and other parameters. The predicted entrainment rates are substantially smaller than those observed by Gerber et al., and are not correlated with them. Drizzle precipitation, as evaluated by VanZanten et al., reduces entrainment rates due to evaporative cooling below cloud base. This effect appears to improve the comparisons with observations. Tests of the robustness of the model calculations show mostly encouraging results. The effect of surface radiation into cloud base is found to be almost negligible. A new criterion for cloud-top entrainment instability, based on the entrainment closure, indicates stability for most observed conditions. The homogeneity of the DYCOMS2 data is beneficial for obtaining reliable measures of entrainment, but limits the ability to test closure predictions over a wide range of conditions. Use of this model for parametrization of marine stratiform cloud layers in large-scale or climate prediction models is considered plausible with limitations. Copyright © 2008 Royal Meteorological Society."
"7005446873;7101867299;","A stochastic parameterization for deep convection based on equilibrium statistics",2008,"10.1175/2007JAS2263.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38849155083&doi=10.1175%2f2007JAS2263.1&partnerID=40&md5=403fc9007a0d7547f86aac033c3152e9","A stochastic parameterization scheme for deep convection is described, suitable for use in both climate and NWP models. Theoretical arguments and the results of cloud-resolving models are discussed in order to motivate the form of the scheme. In the deterministic limit, it tends to a spectrum of entraining/detraining plumes and is similar to other current parameterizations. The stochastic variability describes the local fluctuations about a large-scale equilibrium state. Plumes are drawn at random from a probability distribution function (PDF) that defines the chance of finding a plume of given cloud-base mass flux within each model grid box. The normalization of the PDF is given by the ensemble-mean mass flux, and this is computed with a CAPE closure method. The characteristics of each plume produced are determined using an adaptation of the plume model from the Kain-Fritsch parameterization. Initial tests in the single-column version of the Unified Model verify that the scheme is effective in producing the desired distributions of convective variability without adversely affecting the mean state. © 2008 American Meteorological Society."
"56218203200;7401945370;25647939800;6701670597;","Characteristics of cloud size of deep convection simulated by a global cloud resolving model over the western tropical pacific",2008,"10.2151/jmsj.86A.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971373037&doi=10.2151%2fjmsj.86A.1&partnerID=40&md5=8cf5116717a16147481a130eedb09d8c","Cloud horizontal size distributions of cloud clusters were analyzed for global cloud resolving simulations with the global nonhydrostatic model NICAM whose mesh interval is about 3.5 km and 7 km. The 3.5 km-mesh simulation was performed for 7 days starting at 00 UTC 25 Dec 2006 by giving an initial condition of reanalysis data, while the 7 km-mesh simulation was run for 32 days from 00 UTC 15 Dec 2006. We used outgoing long-wave radiation (OLR) simulated by NICAM to calculate size distributions of deep convection, and compared them with those analyzed using equivalent blackbody temperature (TBB) of the infrared channel of 11 μm of the Japanese geostationary meteorological satellite (MTSAT-1R). We selected two threshold temperatures, 208 K and 253 K, to identify deep convective areas including anvil cloud. Specifically, we call clouds defined by the 208 K-threshold “deeper” convective clouds. Over the tropical region covering the maritime continent and the western tropical Pacific (10S-10N, 90E-160W), we examined the size of cloud areas defined by the two TBB threshold values and corresponding threshold values of OLR of 90 W m-2 and 210 W m-2, which were chosen by comparing cumulative histograms of TBB and OLR in this region. Resolution dependency by NICAM shows that the overall cloud size distribution of the 3.5 km-mesh simulation is much closer to that of the MTSAT-1R observation than that of the 7 km-mesh simulation. Size distributions of deep convection in both simulations indicate nearly lognormal as is seen in the MTSAT-1R observations. The 3.5 km-mesh simulation shows slightly less frequency than the MTSAT- 1R observation for smaller size of deeper convection, and it does not reproduce very large clouds. When comparing cloud characteristics over land and ocean, simulated cloud size statistics are slightly closer to the MT-SAT-1R observation in the maritime continent region (westward of 160E) than in the open ocean region (eastward of 160E). A comparison of temporal variation of cloud area shows that the 3.5 km-mesh simulation captures clear signals of diurnal cycles over the maritime continent, together with amplification associated with the Madden-Julian Oscillation (MJO) event. Morning and afternoon difference of convective activity over a large island within the maritime continent is also simulated by 3.5 km-mesh simulation. When one uses a global cloud resolving model for climate studies, the analysis of cloud size distributions gives another dimension to improve the cloud properties of simulations. It is not only relevant to realistic representations of deep convection, but is also useful for improving the radiation budget of global cloud resolving simulations. © 2008, Meteorological Society of Japan."
"55713905400;57200702127;7404865816;","Implementation of a two-moment bulk microphysics scheme to the WRF model to investigate aerosol-cloud interaction",2008,"10.1029/2007JD009361","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53749089891&doi=10.1029%2f2007JD009361&partnerID=40&md5=f5891864693afcf3268e0fab846755fa","A two-moment bulk microphysical scheme has been implemented into the Weather Research and Forecasting (WRF) model to investigate the aerosol-cloud interaction. The microphysical scheme calculates the mass mixing ratios and number concentrations of aerosols and five types of hydrometeors and accounts for various cloud processes including warm and mixed phase microphysics. The representation of the aerosol size distribution is evaluated, showing that the three-moment modal method produces results better in agreement with the sectional approach than the two-moment modal method for variable supersaturation conditions in clouds. The effects of aerosols on cloud processes are investigated using the two-moment bulk microphysical scheme in a convective cumulus cloud event occurring on 24 August 2000 in Houston, Texas. The modeled evolution of the distribution of radar reflectivity in the y-z section, the cell lifetime, and averaged accumulated precipitation with the aerosol concentration under the polluted urban condition are qualitatively consistent with the measurements. Sensitivity simulations are initialized using a set of aerosol profiles with the number concentrations ranging from 200 to 50,000 cm -3 and mass ranging from 1 to 10 μg m-3 at the surface level. The response of precipitation to the increase of aerosol concentrations is nonmonotonic, because of the complicated interaction between cloud microphysics and dynamics. The precipitation increases with aerosol concentrations from clean maritime to continental background conditions, but is considerably reduced and completely suppressed under highly polluted conditions, indicating that the aerosol concentration exhibits distinct effects on the precipitation efficiency under different aerosol conditions. The maximal cloud cover, core updraft, and maximal vertical velocity exhibit similar responses as precipitation. Comparison is made to evaluate the effects of different autoconversion parameterizations and bulk microphysical schemes on cloud properties. Because of its broad application in numerical weather prediction, implementation of the two-moment microphysical scheme to the WRF model will greatly facilitate assessment of aerosol-cloud interaction from individual cumulus to mesoscale convective systems. Copyright 2008 by the American Geophysical Union."
"7004013739;7202219092;6602239759;6603328138;7102262417;24167945000;","The Geostationary Earth Radiation Budget Edition 1 data processing algorithms",2008,"10.1016/j.asr.2007.07.042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42949090819&doi=10.1016%2fj.asr.2007.07.042&partnerID=40&md5=016f99c6cd9e096cb672b8dc45241ea3","The Geostationary Earth Radiation Budget (GERB) instrument is the first to measure the earth radiation budget from a geostationary orbit. This allows a full sampling of the diurnal cycle of radiation and clouds - which is important for climate studies, as well as detailed process studies, e.g. the lifecycle of clouds or particular aerosol events such as desert storms. GERB data is now for the first time released as Edition 1 data for public scientific use. In this paper we summarise the algorithms used for the Edition 1 GERB data processing and the main validation results. Based on the comparison with the independent CERES instrument, the Edition 1 GERB accuracy is 5% for the reflected solar radiances and 2% for the emitted thermal radiances. © 2007 COSPAR."
"7005035762;6701670597;","Cloud vertical structure observed from space and ship over the bay of bengal and the eastern tropical pacific",2008,"10.2151/jmsj.86A.205","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971467995&doi=10.2151%2fjmsj.86A.205&partnerID=40&md5=038393beb0a9dd2033545092b92ca137","The cloud vertical structure at two remote tropical oceanic convective locations is characterized using both ship-based (35 GHz) and space-based (94 GHz) cloud radar data. The field experiment data depicted the full diurnal cycle and detail of the vertical structures, while the CloudSat sampling was more extensive, but did not coincide with the field experiments. One location is the monsoonal Bay of Bengal, sampled as part of the Joint Air-Sea Monsoon Interaction Experiment (JASMINE), and the other location is the eastern Pacific intertropical convergence zone, sampled during the Eastern Pacific Investigation of Climate (EPIC) experiment. Both ship- and space-based radar datasets find more high cloudiness (9−14 km altitude with an 11−12 km maximum) over the Bay of Bengal than over the eastern tropical Pacific, postulated to reflect the advection of cirrus by upper-level easterly winds. Low-level cloudiness, with some extending into what may be cumulus congestus, is more characteristic of the eastern tropical Pacific than the Bay of Bengal. CloudSat cloud fractions over the eastern Pacific were only ~ one-third those over the Bay of Bengal, in contrast to comparable cloud fractions within the field experiment datasets. A thin melting- level cloud population was also more apparent in the JASMINE data than in the EPIC field experiment data, but the larger CloudSat dataset showed the opposite. These differences discourage regional generalities based on a few weeks of point sampling. Pre-monsoon-onset conditions included a slight afternoon low cloud amount maximum combined with typically one warm rain event per night. High thin cirrus was common (cloud fraction of ~35% with cloud optical depths of 2 or less and ice water paths typically &lt; 40 g m−2). After monsoon onset, the ship-based cloud radar documented examples of coherent relationships among cloud structure, precipitation, and the larger-scale wind field. CloudSat did not detect much precipitating low cloud during its pre-monsoon time period, but did sample the upper-level clouds at approximately the maximum and minimum of their diurnal range. An intriguing finding is that CloudSat perceived a greater daytime occurrence of the highest clouds with reflectivitives &lt; 10 dBZ at both locations, a finding replicated with a year’s data covering the full, ocean-only, tropical belt. We speculate the daytime high cloud may reflect remains of outflow from previous convection. The comparison also highlights differences in the Rayleigh versus Mie responses of the two radars. © 2008, Meteorological Society of Japan."
"7005961973;8576245800;7102038914;","Estimating future trends in severe hailstorms over the Sydney Basin: A climate modelling study",2008,"10.1016/j.atmosres.2007.06.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36849029123&doi=10.1016%2fj.atmosres.2007.06.006&partnerID=40&md5=6130babd19987a2729a767b696447ff7","This study estimates future trends in the characteristics of severe hailstorms that affect the most heavily populated region of Australia, the Sydney Basin, using coupled climate model simulations under both fixed (no change) greenhouse gas concentrations and the IPCC SRES A1B future climate scenario. The ""future climate"", as defined here, is the 50-year period January 1, 2001 to December 31, 2050. First, an assessment is made of the ability of the climate model, in very high-resolution mesoscale model mode, to simulate three of the most severe hailstorms recorded in the Sydney Basin during the ""present climate"" period, defined here as the years 1990 to 2002. These simulations, nested down to 1 km grid spacing, are compared with the archived hail observations of the storms. The climate model then is used to provide estimates of projected changes in hailstorm frequency, tracks, intensity, duration, and hail size over the Sydney Basin for the ""future climate"" period. The model employed in all simulations is the University of Oklahoma Coupled General Circulation Model, known as OU-CGCM, which also can be run as a high-resolution NWP model. The high-resolution version of the OU-CGCM used for the case studies employs a hierarchy of graded mesh and nested model domains, with a sophisticated 10-ice phase cloud microphysics scheme used in the highest resolution domain (1 km horizontal grid spacing) of the model. This work builds upon preliminary hail modelling case studies over eastern New South Wales carried out by the present authors with an earlier version of the model. The model results under the SRES A1B future climate scenario show significant trends out to 2050 in the key characteristics of severe hailstorms over the Sydney Basin, relative to both the 1990-2002 present climate and the 2001-2050 no-change future climate. © 2007 Elsevier B.V. All rights reserved."
"23098367900;57199409342;22234662700;7404416268;7801316935;8931739300;55969830400;7004154240;","Evaluation of community climate system model soil temperatures using observations from Russia",2008,"10.1007/s00704-007-0350-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55149092546&doi=10.1007%2fs00704-007-0350-0&partnerID=40&md5=ccd39871b03870e28e5bd0f20c1b790a","Soil temperatures simulated by the fully coupled Community Climate System Model (CCSM) version 3.0 are evaluated using three gridded climatologies (1951-1980, 1961-1990, 1971-2000) based on data from more than 400 Russian sites. CCSM captures the annual phase of the soil temperature cycle well, but not the amplitude. It provides slightly too high (low) soil temperatures in winter (summer). Root mean square errors, on average, are less than 5 K. Simulated near-surface air temperatures agree well, on average, with near-surface air temperatures from reanalysis data. Errors in simulated atmospheric-temperature forcing correlate statistically significantly (95% or higher confidence level) with soil temperature errors, i.e. contribute to discrepancy in soil temperature simulation. Comparison to International Satellite Cloud Climatology project data shows that errors in simulated cloud fraction explain some soil and near-surface air temperature and precipitation discrepancies. Evaluation by means of Global Precipitation Climatology Centre data identifies inaccurately-simulated precipitation as a contributor to underestimating summer soil temperatures. Comparison to snow-depth observations shows that overestimating snow depth yields winter soil-temperature overestimation. Sensitivity studies show that uncertainty in mineral-soil composition notably, and differences between the vegetation in CCSM and nature marginally contribute to discrepancies between simulated and observed soil-temperature climatology. © Springer-Verlag 2007."
"15726335100;23970271800;6602806333;","Validation of cloud liquid water path retrievals from SEVIRI using one year of CloudNET observations",2008,"10.1175/2007JAMC1661.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40449126198&doi=10.1175%2f2007JAMC1661.1&partnerID=40&md5=9b701945f6f72315dbb19ffcc66a3bf5","The accuracy and precision are determined of cloud liquid water path (LWP) retrievals from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board Meteosat-8 using 1 yr of LWP retrievals from microwave radiometer (MWR) measurements of two CloudNET stations in northern Europe. The MWR retrievals of LWP have a precision that is superior to current satellite remote sensing techniques, which justifies their use as validation data. The Cloud Physical Properties (CPP) algorithm of the Satellite Application Facility on Climate Monitoring (CM-SAF) is used to retrieve LWP from SEVIRI reflectances at 0.6 and 1.6 μm. The results show large differences in the accuracy and precision of LWP retrievals from SEVIRI between summer and winter. During summer, the instantaneous LWP retrievals from SEVIRI agree well with those from the MWRs. The accuracy is better than 5 g m-2 and the precision is better than 30 g m-2, which is similar to the precision of LWP retrievals from MWR. The added value of the 15-min sampling frequency of Meteosat-8 becomes evident in the validation of the daily median and diurnal variations in LWP retrievals from SEVIRI. The daily median LWP values from SEVIRI and MWR are highly correlated (correlation &gt; 0.95) and have a precision better than 15 g m-2. In addition, SEVIRI and MWR reveal similar diurnal variations in retrieved LWP values. The peak LWP values occur around noon. During winter, SEVIRI generally overestimates the instantaneous LWP values from MWR, the accuracy drops to about 10 g m2, and the precision to about 30 g m-2. The most likely reason for these lower accuracies is the shortcoming of CPP, and similar one-dimensional retrieval algorithms, to model inhomogeneous clouds. It is suggested that neglecting cloud inhomogeneities leads to a significant overestimation of LWP retrievals from SEVIRI over northern Europe during winter. © 2008 American Meteorological Society."
"22978151200;7404381445;56249704400;10040054900;7005263785;7404274952;55207447000;6604021707;","MATRIX (Multiconfiguration Aerosol TRacker of mIXing state): An aerosol microphysical module for global atmospheric models",2008,"10.5194/acp-8-6003-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-54949107400&doi=10.5194%2facp-8-6003-2008&partnerID=40&md5=41d87b39c64756f7250b10b833d26385","A new aerosol microphysical module MATRIX, the Multiconfiguration Aerosol TRacker of mIXing state, and its application in the Goddard Institute for Space Studies (GISS) climate model (ModelE) are described. This module, which is based on the quadrature method of moments (QMOM), represents nucleation, condensation, coagulation, internal and external mixing, and cloud-drop activation and provides aerosol particle mass and number concentration and particle size information for up to 16 mixed-mode aerosol populations. Internal and external mixing among aerosol components sulfate, nitrate, ammonium, carbonaceous aerosols, dust and sea-salt particles are represented. The solubility of each aerosol population, which is explicitly calculated based on its soluble and insoluble components, enables calculation of the dependence of cloud drop activation on the microphysical characterization of multiple soluble aerosol populations. A detailed model description and results of box-model simulations of various aerosol population configurations are presented. The box model experiments demonstrate the dependence of cloud activating aerosol number concentration on the aerosol population configuration; comparisons to sectional models are quite favorable. MATRIX is incorporated into the GISS climate model and simulations are carried out primarily to assess its performance/efficiency for global-scale atmospheric model application. Simulation results were compared with aircraft and station measurements of aerosol mass and number concentration and particle size to assess the ability of the new method to yield data suitable for such comparison. The model accurately captures the observed size distributions in the Aitken and accumulation modes up to particle diameter 1 μm, in which sulfate, nitrate, black and organic carbon are predominantly located; however the model underestimates coarse-mode number concentration and size, especially in the marine environment. This is more likely due to oversimplifications of the representation of sea salt emissions - sea salt emissions are only calculated for two size classes - than to inherent limitations of MATRIX."
"56486548700;6701726317;7402000409;23491915700;6603916623;6701436098;7005165467;27868165400;14033392700;","An algorithm to produce temporally and spatially continuous MODIS-LAI time series",2008,"10.1109/LGRS.2007.907971","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38349115938&doi=10.1109%2fLGRS.2007.907971&partnerID=40&md5=b5f0ed336339bed0c3aa163c5dc9673f","Ecological and climate models require high-quality consistent biophysical parameters as inputs and validation sources. NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) biophysical products provide such data and have been used to improve our understanding of climate and ecosystem changes. However, the MODIS time series contains occasional lower quality data, gaps from persistent clouds, cloud contamination, and other gaps. Many modeling efforts, such as those used in the North American Carbon Program, that use MODIS data as inputs require gap-free data. This letter presents the algorithm used within the MODIS production facility to produce temporally smoothed and spatially continuous biophysical data for such modeling applications. We demonstrate the algorithm with an example from the MODIS-leaf-area-index (LAI) product. Results show that the smoothed LAI agrees with high-quality MODIS LAI very well. Higher R-squares and better linear relationships have been observed when high-quality retrieval in each individual tile reaches 40% or more. These smoothed products show similar data quality to MODIS high-quality data and, therefore, can be substituted for low-quality retrievals or data gaps. © 2007 IEEE."
"36910462600;23010243200;57202402269;","Simulation of hailstorm event using Mesoscale Model MM5 with modified cloud microphysics scheme",2008,"10.5194/angeo-26-3545-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56549097332&doi=10.5194%2fangeo-26-3545-2008&partnerID=40&md5=bfb5965531b60f8f4497c41d25a9f9cc","Mesoscale model MM5 (Version 3.5) with some modifications in the cloud microphysics scheme of Schultz (1995), has been used to simulate two hailstorm events over Gangetic Plain of West Bengal, India. While the first event occurred on 12 March 2003 and the hails covered four districts of the state of West Bengal, India, the second hailstorm event struck Srinikatan (22.65° N, 87.7° E) on 10 April 2006 at 11:32 UT and it lasted for 2ĝ€""3 min. Both these events can be simulated, if the same modifications are introduced in the cloud microphysics scheme of Schultz. However, the original scheme of Schultz cannot simulate any hail. The results of simulation were compared with the necessary products of Doppler Weather Radar (DWR) located at Kolkata (22.57° N, 88.35° E). Model products like reflectivity, graupel and horizontal wind are compared with the corresponding products of DWR. The pattern of hail development bears good similarity between model output and observation from DWR, if necessary modifications are introduced in the model. The model output of 24 h accumulated rain from 03:00 UT to next day 03:00 UT has also been compared with the corresponding product of the satellite TRMM."
"15926005400;23568361900;6602300389;","Artificial Neural Networks to reconstruct incomplete satellite data: Application to the Mediterranean Sea Surface Temperature",2008,"10.5194/npg-15-61-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39449120242&doi=10.5194%2fnpg-15-61-2008&partnerID=40&md5=38696777c27561a0cf8ef378d8af44b6","Satellite data can be very useful in applications where extensive spatial information is needed, but sometimes missing data due to presence of clouds can affect data quality. In this study a methodology for pre-processing sea surface temperature (SST) data is proposed. The methodology, that processes measures in the visible wavelength, is based on an Artificial Neural Network (ANN) system. The effectiveness of the procedure has been also evaluated comparing results obtained using an interpolation method. After the methodology has been identified, a validation is performed on 3 different episodes representative of SST variability in the Mediterranean sea. The proposed technique can process SST NOAA/AVHRR data to simulate severe storm episodes by means of prognostic meteorological models."
"15125055800;7004885872;6701378450;","How quickly do cloud droplets form on atmospheric particles?",2008,"10.5194/acp-8-1043-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40149097324&doi=10.5194%2facp-8-1043-2008&partnerID=40&md5=a6ebf26661d7ddc60ad567e9b8ecd396","The influence of aerosols on cloud properties is an important modulator of the climate system. Traditional Köhler theory predicts the equilibrium concentration of cloud condensation nuclei (CCN); however, it is not known to what extent particles exist in the atmosphere that may be prevented from acting as CCN by kinetic limitations. We measured the rate of cloud droplet formation on atmospheric particles sampled at four sites across the United States during the summer of 2006: Great Smoky Mountain National Park, TN; Bondville, IL; Houston, TX; and the Atmospheric Radiation Measurement Program Southern Great Plains site near Lamont, OK. We express droplet growth rates with the mass accommodation coefficient (α), and report values of a measured in the field normalized to the mean a measured for lab-generated ammonium sulfate (AS) particles (i.e., α′=α/αAS)- Overall, 59% of ambient CCN grew at a rate similar to AS. We report the fraction of CCN that were ""low-α′"" (α′&lt;10-1, corresponding to α&lt;1.5×10-2). Of the 16 days during which these measurements were made, 8 had relatively few low-α′ CCN (&lt;16%), 6 had moderate low-α′ fractions (27% to 59%), and 2 had large low-α′ fractions (&gt; 82% during at least one ∼30 min period). Day to day variability was greatest in Tennessee and Illinois, and low-α′ particles were most prevalent on days when back trajectories suggested that air was arriving from aloft. The highest fractions of low-α′ CCN in Houston and Illinois occurred around local noon, and decreased later in the day. These results suggest that for some air masses, accurate quantification of CCN concentrations may need to account for kinetic limitations."
"8594725500;7408466015;55703452200;6602954618;","Statistical downscaling of hourly and daily climate scenarios for various meteorological variables in South-central Canada",2008,"10.1007/s00704-007-0302-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39449091742&doi=10.1007%2fs00704-007-0302-8&partnerID=40&md5=04ccc911a45cda9729b61a8fb99af770","A regression-based methodology was used to downscale hourly and daily station-scale meteorological variables from outputs of large-scale general circulation models (GCMs). Meteorological variables include air temperature, dew point, and west-east and south-north wind velocities at the surface and three upper atmospheric levels (925, 850, and 500 hPa), as well as mean sea-level air pressure and total cloud cover. Different regression methods were used to construct downscaling transfer functions for different weather variables. Multiple stepwise regression analysis was used for all weather variables, except total cloud cover. Cumulative logit regression was employed for analysis of cloud cover, since cloud cover is an ordered categorical data format. For both regression procedures, to avoid multicollinearity between explanatory variables, principal components analysis was used to convert inter-correlated weather variables into uncorrelated principal components that were used as predictors. The results demonstrated that the downscaling method was able to capture the relationship between the premises and the response; for example, most hourly downscaling transfer functions could explain over 95% of the total variance for several variables (e.g. surface air temperature, dew point, and air pressure). Downscaling transfer functions were validated using a cross-validation scheme, and it was concluded that the functions for all weather variables used in the study are reliable. Performance of the downscaling method was also evaluated by comparing data distributions and extreme weather characteristics of downscaled GCM historical runs and observations during the period 1961-2000. The results showed that data distributions of downscaled GCM historical runs for all weather variables are significantly similar to those of observations. In addition, extreme characteristics of the downscaled meteorological variables (e.g. temperature, dew point, air pressure, and total cloud cover) were examined. © Springer-Verlag 2007."
"24537168200;7007061674;7003480967;6602765265;20433889200;7004052136;6504664266;7005941217;55730602600;6701842515;23971773000;14034301300;6602128405;7401891176;7402838215;","Clouds and aerosols in Puerto Rico - A new evaluation",2008,"10.5194/acp-8-1293-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40449090378&doi=10.5194%2facp-8-1293-2008&partnerID=40&md5=09d4162bcb27814a614955e016be1d86","The influence of aerosols, both natural and anthropogenic, remains a major area of uncertainty when predicting the properties and behaviour of clouds and their influence on climate. In an attempt to better understand warm cloud formation in a tropical marine environment, a period of intensive measurements took place in December 2004 in Puerto Rico, using some of the latest developments in online instrumentation such as aerosol mass spectrometers, cloud condensation nuclei counters and a hygroscopicity tandem differential mobility analyser. Simultaneous online measurements of aerosol size distributions, composition, hygroscopicity and optical properties were made near the lighthouse of Cape San Juan in the north-eastern corner of the island and at the top of East Peak mountain (1040 m a.s.l.), the two sites separated by 17km. Additional measurements of the cloud droplet residual and interstitial aerosol properties were made at the mountain site, accompanied by measurements of cloud droplet size distributions, liquid water content and the chemical composition of cloud and rain water samples. Both aerosol composition and cloud properties were found to be sensitive to wind sector. Air from the east-northeast (ENE) was mostly free of anthropogenic influences, the submicron fraction being mainly composed of non-sea salt sulphate, while that from the east-southeast (ESE) was found to be moderately influenced by populated islands upwind, adding smaller (&lt;100nm), externally mixed, carbonaceous particles to the aerosol that increased the number concentrations by over a factor of 3. This change in composition was also accompanied with a reduction in the measured hygroscopicity and fractional cloud activation potential of the aerosol. At the mountain site, the average cloud droplet concentrations increased from 193 to 519 cm -3, median volume diameter decreased from 20 to 14 μm and the liquid water content increased from 0.24 to 0.31 gm-3 when the winds shifted from the ENE to ESE. Larger numbers of interstitial particles were recorded, most notably at sizes greater than 100 nm, which were absent during clean conditions. The average size of the residual particles and concentrations of cloudwater nitrate, sulphate and insoluble material increased during polluted conditions. Previous studies in Puerto Rico had reported the presence of a significant non-anthropogenic organic fraction in the aerosols measured and concluded that this was a factor controlling the in situ cloud properties. However, this was not observed in our case. In contrast to the 1.00±0.14μgm-3 of organic carbon measured in 1992 and 1995, the organic matter measured in the current study of 0.17±0.35μgm -3 is many times lower, most of which can be attributed to anthropogenic sources. During clean conditions, the submicron aerosol was observed to be almost entirely inorganic, an observation supported by the hygroscopicity measurements. This suggests that organic aerosols from marine sources may not be completely ubiquitous (either spatially or temporally) in this environment and requires further investigation to quantify their true extent and implications, with more extensive, longer-term sampling in conjunction with wind field analyses."
"24484636500;11241769400;7003461830;","Modeling the impacts of land cover change in Amazonia: A regional climate model (RCM) simulation study",2008,"10.1007/s00704-007-0335-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48449096575&doi=10.1007%2fs00704-007-0335-z&partnerID=40&md5=49f63751816d66c2275258de75b92346","The numerical regional model (Eta) coupled with the Simplified Simple Biosphere Model (SSiB) was used to investigate the impact of land cover changes on the regional climate in Amazonia. Four 13-month integrations were performed for the following scenarios: (a) no deforestation, (b) current conditions, (c) deforestation predicted for 2033, and (d) large scale deforestation. All initial and prescribed boundary conditions were kept identical for all integrations, except the land cover changes. The results show that during the dry season the post-deforestation decrease in root depth plays an important role in the energy budget, since there is less soil moisture available for evapotranspiration. In all scenarios there was a significant increase in the surface temperature, from 2.0 °C in the first scenario, up to 2.8 °C in the last one. In both the scenarios (b) and (c), the downward component of the surface solar radiation decreased due to an increase in the cloud cover over the deforested areas, which contributed to a further reduction of the net radiation absorbed at the surface. The cloud mechanism, where an increase in albedo is balanced by an increase in downward solar radiation, was not detected in any of these scenarios. In scenarios (a), (b) and (c), a negative feedback mechanism was observed in the hydrological cycle, with greater amounts of moisture being carried to the deforested areas. The increase in moisture convergence was greater than the reduction in evapotranspiration for both scenarios (b) and (c). This result, and the meso-scale thermodynamic processes caused an increase in precipitation. A different situation was observed in the large-scale deforestation scenario (d): a local increase of moisture convergence was observed, but not sufficiently intense to generate an increase in precipitation; the local evapotranspiration decrease was dominant in this scenario. Therefore, the partial deforestation in Amazonia can actually lead to an increase in precipitation locally. However, if the deforestation increases, this condition becomes unsustainable, leading to drier conditions and, consequently, to reduced precipitation in the region. © Springer-Verlag 2007."
"57203983376;","Numerical simulations of the role of land surface conditions in the evolution and structure of summertime thunderstorms over a flat highland",2008,"10.1175/2007MWR2053.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39749157770&doi=10.1175%2f2007MWR2053.1&partnerID=40&md5=ff9b702a75fcebed5010e403f07ba77a","Numerical simulations of summertime thunderstorms over a flat highland (4700 m MSL), assuming the central Tibetan Plateau, were conducted with the use of a cloud-resolving nonhydrostatic model. This study was aimed at clarifying the role of land surface conditions, such as soil moisture and vegetation activity, in the evolution and structure of airmass thunderstorms over the plateau. Two simulations with cyclic lateral boundaries and different surfaces of a dry or wet land were initialized using a unique vertical atmospheric profile at dawn. These initial conditions assume the real atmospheric conditions in two periods of the 1998 summer monsoon, which are characterized by a dry or wet surface. The results of the two experiments were used to examine the contrasting features between the two experiments arising from the different surface conditions. The simulations reproduced differences in the convective structure, the conditions of the subcloud layer, and the evaporation rate of precipitation within this layer. These resulted from different surface-heating processes and were supported by the observational evidence clarified in a previous study. Moreover, the simulations also reproduced the cell broadening occurring in both the boundary and cloud layers and different precipitation processes dependent on the updraft strength. The evidence was partly supported by additional analyses of observational data. This study, therefore, demonstrates a significant effect of the plateau surface upon the cloud evolution and the precipitation process. © 2008 American Meteorological Society."
"55839333400;6603580234;7202887238;7006068346;","Water quality assessment in the application of stormwater reuse for irrigating public lands",2008,"10.2166/wqrj.2008.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952586891&doi=10.2166%2fwqrj.2008.018&partnerID=40&md5=e32fff6823e05add33bd397c5c098909","Stormwater reuse for irrigating public lands presents a viable option for reducing potable water demand in urban settings. However, stormwater generally contains high pollutant levels, which may cause adverse effects on public health and the environment. Water quality in a stormwater retention pond in the City of Calgary, Alberta, was examined in order to assess the feasibility of reusing stormwater for irrigation purposes. Field campaigns were conducted in the 2004, 2005, and 2006 irrigation seasons. The water quality data indicated that the pond water quality generally satisfies the requirements for stormwater recycled as irrigation water. Relationships between stormwater quality and climatological variables were investigated using correlation and regression analysis. Their correlations suggest that intermittent rain events contribute to elevated microbial levels and total suspended solids (TSS). Other climatological variables-air temperature, cloud cover, wind speed, and relative humidity-are also correlated with certain water quality parameters including fecal coliform (FC), TSS, nutrients, and conductivity. Formulated regression equations demonstrate good predictions of observed FC and TSS using climatological variables. Results showing stormwater quality as a function of climatological variables imply that climate change might have potential influence on stormwater quality. © 2008, CAWQ."
"55106893400;","Rate of increasing concentrations of atmospheric carbon dioxide controlled by natural temperature variations",2008,"10.1260/095830508786238369","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65849526241&doi=10.1260%2f095830508786238369&partnerID=40&md5=5a681e42d5262ad55598dac109f4b4f7","Studies of the temperature anomalies during the last 27 years show a close relationship with the varying increase of CO2 in the atmosphere. Volcanic eruptions and La Niñas reduce CO2 values and El Niños increase them. This close relationship strongly indicates that ocean temperatures and the solubility of CO2 in seawater control the amount of CO2 being absorbed or released by the oceans. It is therefore likely that the increased CO2 concentration in the atmosphere is due to a natural global warming and that CO2 produced through fossil fuel combustion by humans can not disrupt this balance. An advanced statistical multiregression analysis confirms this conclusion. Therefore it is likely that there is no anthropogenic climate change on a global scale. The natural exchange of CO2 between ocean, biomass on land and the atmosphere is very large. In only four to five years all the CO2 in the atmosphere has been recycled through the oceans and the biomass system. The annual anthropogenic human production of CO2 is neutralized by nature in as little as 12 days. Recent studies of the solar forcing, changes in cosmic radiation and its role in cloud formations explain the global warming that has taken place since 1910."
"7202429440;7201432984;7006399419;7005254328;","Influence of particle size and chemistry on the cloud nucleating properties of aerosols",2008,"10.5194/acp-8-1029-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40049087558&doi=10.5194%2facp-8-1029-2008&partnerID=40&md5=1a9ee17227665ef868a31a77d73122c3","The ability of an aerosol particle to act as a cloud condensation nuclei (CCN) is a function of the size of the particle, its composition and mixing state, and the supersaturation of the cloud. In-situ data from field studies provide a means to assess the relative importance of these parameters. During the 2006 Texas Air Quality - Gulf of Mexico Atmospheric Composition and Climate Study (TexAQSGoMACCS), the NOAA RV Ronald H. Brown encountered a wide variety of aerosol types ranging from marine near the Florida panhandle to urban and industrial in the HoustonGalveston area. These varied sources provided an opportunity to investigate the role of aerosol sources and chemistry in the potential activation of particles to form cloud droplets. Measurements were made of CCN concentrations, aerosol chemical composition in the size range relevant for particle activation in warm clouds, and aerosol size distributions. Variability in aerosol composition was parameterized by the mass fraction of Hydrocarbon-like Organic Aerosol (HOA) for particle diameters less than 200 nm (vacuum aerodynamic). The HOA mass fraction in this size range was lowest for marine aerosol and highest for aerosol sampled close to anthropogenic sources. Combining all data from the experiment reveals that composition (defined by HOA mass fraction) explains 40% of the variance in the critical diameter for particle activation at the instrumental supersaturation (S) of 0.44%. Correlations between HOA mass fraction and aerosol mean diameter show that these two parameters are essentially independent of one another for this data set. We conclude that, based on the variability of the HOA mass fraction observed during TexAQS-GoMACCS, variability in particle composition played a significant role in determining the fraction of particles that could activate to form cloud droplets. Using a simple model based on Köhler theory andthe assumption that HOA is insoluble, we estimate the degree to which calculated CCN concentrations are under- or overestimated if the variability in the HOA mass fraction that was observed during TexAQS-GoMACCS is neglected. The percent under- or overestimation in the CCN concentration is related to the source of the aerosol. Relative to the mean HOA mass fraction of 0.4±0.2 (average ±1σ standard deviation) for the entire experiment, CCN concentrations are underestimated by up to 50% (at 0.22% S) for aerosol sampled far from anthropogenic source regions as it had a lower HOA mass fraction and overestimated by up to 50% for organicrich aerosol sampled near the source as it had a higher HOA mass fraction."
"6602908667;7102857642;","Diurnal march of rainfall simulated in a T106 AGCM and dependence on cumulus schemes",2008,"10.2151/jmsj.86a.163","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971402151&doi=10.2151%2fjmsj.86a.163&partnerID=40&md5=a4d4515a5deaa70e2424e6f0772f6ab4","Realistic large-scale diurnal marches of precipitation in various regions in the global tropics over both land and ocean were successfully simulated in an atmospheric general circulation model (AGCM) developed in collaboration by the Center for Climate System Research, the National Institute for Environmental Studies, and the Frontier Research Center for Global Climate (CCSR/NIES/FRCGC), with a resolution of T106, and was forced with prescribed sea surface temperatures. This is an outstanding performance of the diurnal cycle simulated in the AGCM with similar resolution. Comparison analyses with the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and Precipitation Radar (PR) data revealed that an implementation of the relative humidity (RH) threshold to the prognostic Arakawa-Schubert (AS) cumulus parameterization significantly improved the diurnal variation of precipitation especially in its large-scale marches. It was suggested that the cloud-layer RH threshold lead to a tighter coupling between free-tropospheric gravity waves and cumulus convection compared to the original prognositic AS, with which convection is more obedient to the boundary-layer warming. © 2008, Meteorological Society of Japan."
"8966521300;24460392200;35550043200;9233214000;57199847019;","Comparison of satellite limb-sounding humidity climatologies of the uppermost tropical troposphere",2008,"10.5194/acp-8-309-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38749152456&doi=10.5194%2facp-8-309-2008&partnerID=40&md5=55771a9289bf719441202b6e7404fd08","Humidity climatologies of the tropical uppermost troposphere from satellite limb emission measurements have been compared. Four instruments are considered; UARS-MLS, Odin-SMR, and Aura-MLS operating in the microwave region, and MIPAS in the infrared region. A reference for the comparison is obtained by MOZAIC in-situ measurements. The upper tropospheric humidity products were compared on basis of their empirical probability density functions and seasonally averaged horizontal fields at two altitude layers, 12 and 15 km. The probability density functions of the microwave datasets were found to be in very good agreement with each other, and were also consistent with MOZAIC. The average seasonal humidities differ with less than 10%RHi between the instruments, indicating that stated measurement accuracies of 20-30% are conservative estimates. The systematic uncertainty in Odin-SMR data due to cloud correction was also independently estimated to be 10%RHi. MIPAS humidity profiles were found to suffer from cloud contamination, with only 30% of the measurements reaching into the upper troposphere, but under clear-sky conditions there is a good agreement between MIPAS, Odin-SMR and Aura-MLS. Odin-SMR and the two MLS datasets can be treated as independent, being based on different underlying spectroscopy and technology. The good agreement between the microwave limb-sounders, and MOZAIC, is therefore an important step towards understanding the upper tropospheric humidity. The found accuracy of 10%RHi is approaching the level required to validate climate modelling of the upper troposphere humidity. The comparison of microwave and infrared also stresses that microwave limb-sounding is necessary for a complete view of the upper troposphere."
"7402456930;7404222967;7004159070;36000595000;35849753400;13310165300;7004208584;9746433100;","Radiative impact of boreal smoke in the Arctic: Observed and modeled",2008,"10.1029/2007JD009657","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649152896&doi=10.1029%2f2007JD009657&partnerID=40&md5=10aef428fa9c12d6cbf033ab6d96e322","The Arctic climate is modulated, in part, by the presence of aerosols that affect the horizontal and vertical 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. During summer 2004 forest fires destroyed vast areas of boreal forest in Alaska and western Canada, releasing smoke into the atmosphere. Smoke aerosol passing over instrumented field sites near Barrow, Alaska, was monitored to determine its physical and optical properties and its impact on the surface radiation budget. Empirical determinations of the direct aerosol radiative forcing (DARF) by the smoke were used to corroborate simulations made using the Moderate Resolution Transmittance radiative transfer model, MODTRAN™5. DARF is defined as the change in net shortwave irradiance per unit of aerosol optical depth (AOD). DARF, varying with solar angle and surface type, was evaluated at the surface, at the top of the atmosphere (TOA), and within the intervening layers of the atmosphere. The TOA results are compared with fluxes derived from coincident satellite retrievals made using the Clouds and the Earth's Radiant Energy System (CERES) radiance data. Smoke tends to reduce the net shortwave irradiance at the surface while increasing it within layers in which it resides. Over the Arctic tundra during summer, a layer of smoke having AOD = 0.5 at 500 nm produces a diurnally averaged DARF of about -40 W m-2 at the surface and -20 W m -2 at TOA, while the layer itself tends to warm at a rate of ≈1 Kd-1. The tendency of smoke to cool the surface while heating the layer above may lead to increased atmospheric stability and suppress cloud formation. Radiative forcing at the top of the atmosphere is especially sensitive to small changes in surface albedo, evidenced in both the model results and satellite retrievals. TOA net shortwave flux decreases when smoke is present over dark surfaces and tends to increase if the underlying surface is bright. For example, at solar noon during midsummer at Barrow, a layer of smoke having AOD(500) = 0.5 will reduce the net shortwave flux at TOA by ≈30 W m-2 over the ocean while at the same time increasing it by 20 W m-2 over an adjacent area of melting sea ice. For smoke aerosol, the sensitivity of DARF to changing surface albedo (assuming a solar zenith angle of 50°) is about +15 W m-2 AOD-1 for every increase in surface albedo of 0.10. Throughout the Arctic summer, surface and TOA cooling and a tendency toward warming in the intervening atmospheric layers are the dominant radiative impacts of boreal smoke over the ocean and tundra areas, but the radiative forcing at TOA is positive over regions covered by ice or snow. Enhanced differential cooling/heating of ocean, ice, and snow due to the presence of smoke in the atmosphere may affect regional circulation patterns by perturbing diabatic processes. Should the frequency and intensity of boreal fires increase in the future because of global warming, the more persistent presence of smoke in the atmosphere may be manifest as a negative feedback at the surface. In addition, there will likely be indirect radiative impacts of the smoke as it influences cloudiness, which in turn further modulates the Arctic radiation budget. Copyright 2008 by the American Geophysical Union."
"26655075300;6506238357;","Use of radio occultation for long-term tropopause studies: Uncertainties, biases, and instabilities",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749105032&partnerID=40&md5=5ce00e0cdd79cdc7ecf021b623aa860e","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."
"6508340903;7403019018;7102193375;7003771738;","Climatic conditions at the Mittivakkat Glacier catchment (1994-2006), Ammassalik Island, SE Greenland, and in a 109-year perspective (1898-2006)",2008,"10.1080/00167223.2008.10649574","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50449095458&doi=10.1080%2f00167223.2008.10649574&partnerID=40&md5=b74db2a549f31e73145d7cdd3570a822","The present-day climate in tne Mittivakkat Glacier catchment (65°N), Southeast Greenland, is investigated spatiotemporally based on time series (13 years, 1994-2006) and standard synoptic climate data from the meteorological station in Tasiilaq (Ammasslik), covering 109 years (1898-2006). Within the catchment, meteorological conditions are monitored at the coast (Station Coast, 25 m a.s.l) for the period 1998-2006 and in the glacier area (Station Nunatak, 515 m a.s.l.) for 1994-2006 During this 13-year period, solar radiation shows increasing values, averaging 0.5 W m-2 y-1, at the nunatak and decreasing values, averaging 1.4 W m-2 y-1, at the coast. The mean annual solar radiation at Station Coast is 102 W m-2 y-1, which is about 10% lower than at Station Nunatak, and is probably caused by increasing and higher percentages of dense clouds and sea fog in the coastal area. The mean annual air temperature is increasing by 0.10°C y-1 at the nunatak and by 0.05°C y-1 at the coast, extending the thawing periods by about 50 days and 5 days, respectively. A snow-free period of 64 days is observed at the nunatak. The coastal area is highly dominated by air temperature inversion and sea breezes during spring and summer, strongly controlling the lapse rates within the catchments. The glacier area is highly dominated by katabatic fall winds, resulting in an almost total lack of calm periods. The wind speed is highest during winter with mean average values around 6.0 m s-1, and gusts up to 35.0 m s-1. The total annual precipitation varies from 1,851 mm w.eq. y-1 at the nunatak (solid precipitation: 80%, mixed: 6%, and liquid: 14%) to 1,428 mm w.eq. y-1 at the coast (53%, 31%, and 16%), covering an average positive orographic effect for solid precipitation during winter (113 mm w.eq. 100 m-1) and a negative effect for liquid precipitation during summer (-52 mm w.eq. 100 m-1). Over the last 109 years (1898-2006) precipitation in the catchment has increased about 85 mm w.eq., covering two significant precipitation-rich periods: 1901-1914 (1,560 mm w.eq. y-1) and 1963-1978 (1,563 mm weq. y-1). Mean annual air temperature in the catchment has generally increased 0.2°C through the 109-year period, most significantly -2.7°C within the last 25 years. The warmest 10-year period since 1898 was 1938-1947, showing an annual average of -1.83°C, while 1997-2006 was the warmest 10-year period within the last 60 years, with an annual average of 2.10°C."
"35779178900;7407116104;7004364155;7403508241;7003854810;","Using CERES data to evaluate the infrared flux derived from diffusivity approximation",2008,"10.1109/LGRS.2007.905198","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38349170374&doi=10.1109%2fLGRS.2007.905198&partnerID=40&md5=91475b0b0d56967220b5692f5b78dc33","Based on the diffusivity approximation theory, the infrared flux at the top of atmosphere (TOA) can be obtained by multiplying a factor of on the infrared radiance that was measured at a viewing zenith angle (VZA) of 53°. This letter applies the diffusivity approximation on radiance measurements of the Clouds and the Earth's Radiant Energy System (CERES) to derive TOA infrared fluxes and compares these fluxes with the state-of-the-art CERES outgoing radiative fluxes. We find that the mean difference between the two kinds of instantaneous flux that were estimated at the window channel is ∼1 W ·m-2, with a root-mean-square error of ∼1.7 W ·m-2. This result shows that radiance measurement at a fixed VZA of 53° is a simple and effective method in the remote sensing of the infrared flux for satellite missions that monitor some specific climate processes and require longwave/window TOA fluxes, such as the Broad Band Radiometer instrument on EarthCARE; however, this approach may involve errors from an inhomogeneous scene or non-Lambertian emission of the surface. A careful design of the VZA and scan mode, such as a conical scan at 53°, would produce much more convenient infrared flux measurements for the Earth-atmosphere system than other designs. © 2007 IEEE."
"6602148086;57200997365;","Quantifying spatial patterns of bioclimatic zones and controls in Turkey",2008,"10.1007/s00704-006-0294-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39449107562&doi=10.1007%2fs00704-006-0294-9&partnerID=40&md5=2aac944051d7307638555c66f58d2115","The study was aimed at inferring spatial patterns of climatic zones as well as identifying significant discriminating bioclimatic controls for distribution of major ecosystems in Turkey, based on multivariate analyses. A total of 12 climate variables and 11 bioclimatic indices for the period of 1968-2004 at 272 meteorological stations, and four location data (latitudes, longitudes, altitudes, and distance to sea) were analyzed using discriminant analysis (DA), hierarchical and non-hierarchical cluster analyses (CA), principal components analysis (PCA), and multiple linear regression (MLR) models. The first three and four linear discriminant functions (LDFs) explained 88 and 95% of the variation in the dataset, respectively. The efficacy of the discriminant model was high (85.5%) based on the cross-validation method. The hierarchical and non-hierarchical CA pointed to seven clusters (climate types) that can be observed on the basis of broad climatic similarity of 97%. PCA elucidated 78% of variation in the dataset. MLR models that accounted for variations in the 12 climatic response variables as a function of the four location variables and aspect had R2 values ranging from 28.8% for precipitation to 89.8% for mean air temperature and soil temperature for a depth of 5 cm. The multivariate analyses indicated that the meteorological stations are heterogeneous clusters consisting of the seven climatic zones. However, differences in the bioclimatic variables at the boundaries complicate the natural clustering scheme of a multidimensional cloud of data points and were detected in a climatologically plausible manner by the Ward and K-means CA, and PCA. Our multivariate approach revealed that the commonly used climatic zones are insufficient representations of the inferred climatic zones: (1) the coastal Black Sea; (2) the inland Black Sea; (3) the southeastern Anatolia; (4) the eastern Anatolia; (5) the central Anatolia; (6) the Mediterranean; and (7) the Aegean. © Springer-Verlag 2007."
"7004375028;","Natural hazards for the Earth's civilization from space, 1. Cosmic ray influence on atmospheric processes",2008,"10.5194/adgeo-14-281-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42149170648&doi=10.5194%2fadgeo-14-281-2008&partnerID=40&md5=f86af40579225b9bf3ec1638d44d7b9b","In this paper we give a short description of global natural disasters for the Earth's civilization from space: 1) Galactic and solar cosmic ray (CR) influence on the atmospheric processes; 2) Impacts of great space magnetic storms during big Forbush-effects in CR, 3) Impacts of great radiation hazards from solar CR during flare energetic particle events, 4) Great impacts on planetary climate during periods of the Solar system capturing by molecular-dust clouds, 5) Catastrophic disasters from nearby Supernova explosions, and 6) Catastrophic disasters from asteroid impacts on the Earth. Some of these problems have been already studied (see e.g. Dorman, 1957, 1963a, b; Dorman and Miroshnichenko, 1968; Dorman, 1972, 1974, 1975a, b, 1978; Velinov et al., 1974; Miroshnichenko, 2001, 2003; Dorman, 2004, 2006, 2008). We present here a detailed treatment of the first disaster only, leaving to future papers the analysis of the other aspects."
"6506944086;9740124600;6603433890;6505842306;6603123442;","Correlation of the late eocene-early oligocene izúcar de matamoros evaporites (Cuayuca Formation) in Mexico based on parsimony analysis of endemicity",2008,"10.2113/gspalynol.32.1.231","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58649124517&doi=10.2113%2fgspalynol.32.1.231&partnerID=40&md5=8991b9f5889f9799d3e953e733f54b8c","Based on the lithology of the Izucar de Matamoros (IzM) sections, and the occurrence of index taxa such as Armeria, Cicatricosisporites dorogensis, Corsinipollenites, Eucommia, Momipites coryloides, Momipites tenuipolus, Mutisiapollis, and Ranuculacidites operculatus, a correlation between the IzM sections and the Cuayuca Formation stratotypes is proposed. The IzM sections are Late Eocene-Early Oligocene, and they are part of the evaporitic member (Mcy) of the Cuayuca Formation. These new data are consistent with the paleoenvironmental interpretations proposed for the formation. It was probably deposited under local xeric conditions in a semiarid climate that allowed the development of grassland (Gramineae with Amaranthaceae-Chenopodiaceae and Ephedra) and a thorn shrub community with Acacia, other Leguminosae, Linum, and Plumbaginaceae. The neighboring communities were probably tropical deciduous forests, low tropical deciduous forest, thorn forest, and chaparral. There were also regional temperate vegetations such as a Picea-Pinus forest, and a cloud forest community. Using parsimony analysis of endemicity, a biogeographic method, a palynofloristic relationship between the Cuayuca Formation and the Pie de Vaca Formation (Late Eocene-Early Oligocene) is proposed. Both formations are within the Balsas Group, and are correlated with San Gregorio Formation (Oligocene) of southern Baja California. © 2008 by AASP Foundation."
"7409389979;7601443168;","Effects of terrain heights and sizes on island-scale circulations and rainfall for the island of Hawaii during HaRP",2008,"10.1175/2007MWR1984.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39749181048&doi=10.1175%2f2007MWR1984.1&partnerID=40&md5=3a3d7b236b933da348fa67c5ef361e1d","Islands in Hawaii have different sizes and terrain heights with notable differences in climate and weather. In this study, the fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5) land surface model (LSM) is used to conduct numerical simulations for the island of Hawaii with different model terrain heights and sizes during the diurnal cycle for the Hawaiian Rainband Project (HaRP) period. In addition to island blocking and orographic lifting, terrain heights also affect the land surface thermal forcing throughout the diurnal cycle by the variations of orographic clouds during the day and by the variations of the longwave radiation heat loss at night. The simulated rainfall distributions and amounts throughout the diurnal cycle are closely related to rising motions caused by nonlinear interactions among island blocking, orographic lifting, and land surface processes. Besides the terrain/mountain height, island size is another factor that affects rainfall production and distribution in Hawaii, because island size affects orographic lifting, surface forcing, and the advection time scale for an air parcel to reach the mountaintop. The heavy rainfall maximum on the mountaintop of the island of Kauai is due to its suitable height and size. This study confirms that the evening rainfall maximum along the western Kona leeside coast is caused by the convergence between the westerly return flow and the offshore flow. For a lower model terrain, the westerly return flow is weaker; as a result, there are smaller evening rainfall amounts. © 2008 American Meteorological Society."
"8218839600;57203052274;9940368600;7102578937;8980175400;8888621200;","Global budgets of atmospheric glyoxal and methylglyoxal, and implications for formation of secondary organic aerosols",2008,"10.1029/2007JD009505","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71949119674&doi=10.1029%2f2007JD009505&partnerID=40&md5=0103ad6e20f865c866e9165b163a2fe9","We construct global budgets of atmospheric glyoxal and methylglyoxal with the goal of quantifying their potential for global secondary organic aerosol (SOA) formation via irreversible uptake by aqueous aerosols and clouds. We conduct a detailed simulation of glyoxal and methylglyoxal in the GEOS-Chem global 3-D chemical transport model including our best knowledge of source and sink processes. Our resulting best estimates of the global sources of glyoxal and methylglyoxal are 45 Tg a-1 and 140 Tg a-1, respectively. Oxidation of biogenic isoprene contributes globally 47% of glyoxal and 79% of methylglyoxal. The second most important precursors are acetylene (mostly anthropogenic) for glyoxal and acetone (mostly biogenic) for methylglyoxal. Both acetylene and acetone have long lifetimes and provide a source of dicarbonyls in the free troposphere. Atmospheric lifetimes of glyoxal and methylglyoxal in the model are 2.9 h and 1.6 h, respectively, mostly determined by photolysis. Simulated dicarbonyl concentrations in continental surface air at northern midlatitudes are in the range 10-100 ppt, consistent with in situ measurements. On a global scale, the highest concentrations are over biomass burning regions, in agreement with glyoxal column observations from the SCIAMACHY satellite instrument. SCIAMACHY and a few ship cruises also suggest a large marine source of dicarbonyls missing from our model. The global source of SOA from the irreversible uptake of dicarbonyls in GEOS-Chem is 11 Tg C a-1, including 2.6 Tg C a-1 from glyoxal and 8 Tg C a-1 from methylglyoxal; 90% of this source takes place in clouds. The magnitude of the global SOA source from dicarbonyls is comparable to that computed in GEOS-Chem from the standard mechanism involving reversible partitioning of semivolatile products from the oxidation of monoterpenes, sesquiterpenes, isoprene, and aromatics. Copyright 2008 by the American Geophysical Union."
"23468493600;36523706800;6701410329;","Verification of NCEP reanalysis shortwave radiation with mesoscale remote sensing data",2008,"10.1109/LGRS.2007.907537","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38349154126&doi=10.1109%2fLGRS.2007.907537&partnerID=40&md5=b189820f987c65d93860d7857211a3a3","This letter contains a validation of the National Center for Environmental Prediction/National Center for Atmospheric Research 40-year reanalysis radiation data sets to evaluate their accuracy in the determination of radiation fluxes. Unlike other recent studies that operate on a global scale, this letter concentrates on the regional aspects of climate research using high-resolution remote sensing data as a reference. These data sets are derived from Meteosat Second Generation, and the focus lies in the area between 35° N to 60° N, 10° N to 25° E covering Central and Southern Europe and the surrounding sea. The examination of the incoming shortwave radiation, the surface albedo, and the solar radiation budget shows the influence of cloud cover parameterization and land-sea distribution as well as orographic and subgrid phenomena. The results lead to the conclusion that on a regional scale, the accuracy of the reanalysis products concerning solar radiation fluxes is limited. © 2007 IEEE."
"12143017100;54983307800;7404168840;8558968300;56245612500;36870160800;57211224269;","Reproducibility of maximum daily precipitation amount over Japan by a High-resolution Non-hydrostatic Model",2008,"10.2151/sola.2008-027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957720658&doi=10.2151%2fsola.2008-027&partnerID=40&md5=70c9286e1f9799fb335cd401dac3acc9","In order to study changes in the regional climate in the vicinity of Japan during the summer rainy season due to global warming, preliminary experiments by a semi-cloud resolving non-hydrostatic model with a horizontal resolution of 5 km (NHM-5km) are conducted from June to October between 2002 and 2006 using 20-km horizontal grid operational regional analysis data of Japan Meteorological Agency (JMA) as the initial and boundary conditions. The total precipitation amount and appearance frequency for daily precipitation amount simulated by the NHM-5km show notable agreement with those of the surface observation data of Automated Meteorological Data Acquisition System (AMeDAS) of JMA. The temporal and spatial characteristics of maximum daily precipitation amounts (MDPs) from June to October also agree well with the observational results. The regional largest values among MDPs (R-MDPs) for 6 regions of the Japanese Islands are also estimated for the simulation results of the nearest grid points for each AMeDAS station and the AMeDAS observations. Those comparisons conclude the high performance of the NHM-5km for the reproducibility of MDPs and R-MDPs, which are highly related to extreme events. © 2008, the Meteorological Society of Japan."
"7005196173;7003553425;57206225739;8721557100;7007025811;7006406683;8509152300;7202622508;54079615400;","Increased runoff from melt from the Greenland Ice Sheet: A response to global warming",2008,"10.1175/2007JCLI1964.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849105229&doi=10.1175%2f2007JCLI1964.1&partnerID=40&md5=10f588a679eacdb7522c955fa4f0cdfb","The authors attribute significantly increased Greenland summer warmth and Greenland Ice Sheet melt and runoff since 1990 to global warming. Southern Greenland coastal and Northern Hemisphere summer temperatures were uncorrelated between the 1960s and early 1990s but were significantly positively correlated thereafter. This relationship appears to have been modulated by the North Atlantic Oscillation, whose summer index was significantly (negatively) correlated with southern Greenland summer temperatures until the early 1990s but not thereafter. Significant warming in southern Greenland since ∼1990, as also evidenced from Swiss Camp on the west flank of the ice sheet, therefore reflects general Northern Hemisphere and global warming. Summer 2003 was the warmest since at least 1958 in coastal southern Greenland. The second warmest coastal summer 2005 had the most extensive anomalously warm conditions over the ablation zone of the ice sheet, which caused a record melt extent. The year 2006 was the third warmest in coastal southern Greenland and had the third-highest modeled runoff in the last 49 yr from the ice sheet; five of the nine highest runoff years occurred since 2001 inclusive. Significantly rising runoff since 1958 was largely compensated by increased precipitation and snow accumulation. Also, as observed since 1987 in a single composite record at Summit, summer temperatures near the top of the ice sheet have declined slightly but not significantly, suggesting the overall ice sheet is experiencing a dichotomous response to the recent general warming: possible reasons include the ice sheet's high thermal inertia, higher atmospheric cooling, or changes in regional wind, cloud, and/or radiation patterns. © 2008 American Meteorological Society."
"24337692100;7003673415;","SERGE: A spatially explicit generator of local rainfall in southern Africa",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-44649173228&partnerID=40&md5=1b3233ac61f0a8d1f85d5715e22f31b3","This article describes the features of SERGE, a stochastic, spatially explicit tool for the simulation of daily rainfall in arid environments. Rainfall data (either raw or produced by a rainfall generator) are frequently available on a daily basis but at low spatial resolution. Furthermore, although the rainfall characteristics of a given small area may vary little when averaged over the long term, rainfall does vary substantially on a daily time scale. It is exactly this short-term, small-scale variation that is of interest to modellers in many applications. A tool is needed therefore that generates spatio-temporal rainfall estimates based on only temporal data. To fill this gap, we developed SERGE using an ad hoc approach. Based on known characteristics of rainfall at a point, SERGE projects spatially homogeneous daily rainfall produced by a rainfall generator into spatially heterogeneous estimates by distributing clouds of fixed size and random position. Our algorithm preserves the long-term rainfall characteristics at each point, but introduces spatial autocorrelation of variable length. SERGE provides a simple and flexible tool for the simulation of spatio-temporal rainfall to be integrated into other models. SERGE is intended for modellers wanting to investigate the effect of spatially variable rainfall in their system. Given the importance of spatial variability in arid environments, this should be of interest to scientists in the fields of ecology, range management, agriculture, climate change, and hydrology."
"7402689885;6506387443;7006346740;","Climatology of tropopause folds over a European Arctic station (Esrange)",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049084525&partnerID=40&md5=fe9eaa8285277aa99aa2ba32d7aee68e","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."
"57204301081;56014511300;55438286600;","Resonant response of deep convection to surface hot spots",2008,"10.1175/2007JAS2398.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38849089270&doi=10.1175%2f2007JAS2398.1&partnerID=40&md5=cf1aa02b9975e664dfa410f734f818fe","Observations show substantial variations of the intensity of tropical and/or summertime deep convection on land that are not explained by standard measures of convective instability. One feature that distinguishes land surfaces is their heterogeneity. The possible importance of this is investigated here by calculating the response of a nonrotating atmosphere to localized, transient surface heating using both the linearized equations of motion and a cloud-resolving configuration of the Weather Research and Forecasting (WRF) numerical model with moist physics, each in 2D. Both models predict that the depth of the resulting surface heat low near storm center will be greatest for a particular horizontal scale of heating. The linear model reveals that this is a resonant scale determined by the product of the environmental buoyancy frequency, characteristic heating time scale, and thickness of the thermal boundary layer, and the resonance occurs when the aspect ratio of the applied heating matches the ratio of vertical and horizontal wavenumbers demanded by the dispersion relation for buoyancy (gravity) waves. For realistic conditions, the resonant horizontal scale is roughly 50 km. The numerical model indicates that other measures of convective intensity, such as updraft speed and storm height, are largely controlled by the depth of the heat low, despite the presence of conditional instability and the vigorous growth of moist convective plumes. Predictions here agree with reported observations of storm severity over islands of different sizes. These findings may help explain why observed geographical variations in storm intensity defy parcel theory and indicate that phenomena often attributed to parcel entrainment may instead be due largely to storm-scale dynamical constraints. © 2008 American Meteorological Society."
"37032346000;7203054240;7202155374;14030633500;56134453000;57214057144;","Interannual variability of smoke and warm cloud relationships in the Amazon as inferred from MODIS retrievals",2007,"10.1016/j.rse.2007.04.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35548972886&doi=10.1016%2fj.rse.2007.04.003&partnerID=40&md5=f4f5158b5268ebdd9d84f16baedf5e09","Aerosol and cloud data from the MODerate resolution Imaging Spectroradiometer (MODIS) onboard the Earth Observing System (EOS) Aqua are used to investigate interannual variability of smoke and warm cloud relationships during the dry-to-wet transition season (August-October) over the Amazon for two years and its association with meteorological conditions. In one year (2003), smoke aerosols are associated with an increase of cloud fraction and a decrease of cloud effective radius. These effects amplify the cooling at the surface and at the top of the atmosphere (TOA) caused by the aerosol extinction. However, in another year (2002) the cloud fraction decreases with increasing aerosol optical depth. Such a decrease of cloud fraction could offset the effect of increased reflection of solar radiation by the aerosols both at the surface and at TOA. The changes in radiative fluxes between these years would contribute to interannual changes of surface energy fluxes and radiative balance at the top of the atmosphere and influence variability of the wet season onset in the basin. In 2003, the atmosphere was more humid and less stable. These conditions may be relatively favorable for the activation of aerosol particles into cloud condensation nuclei and hence cloud droplets. In 2002, the clouds were less extensive and thinner in a relatively dry atmosphere and presumably dissipated more easily. This study suggests that the aerosol-cloud relation can be influenced by atmospheric structure and convective motions, in addition to changes in aerosols properties. An adequate characterization of aerosol-cloud relationship would require a longer time series of data that includes a variety of climate conditions. The caveat of this analysis is that differences in aerosol absorption and its vertical distribution may have contributed to the observed interannual change of smoke-cloud relationship but could not be determined due to lack of adequate measurements. © 2007 Elsevier Inc. All rights reserved."
"57196143493;56744278700;8953038700;55087038900;16027966800;","A strict test in climate modeling with spectrally resolved radiances: GCM simulation versus AIRS observations",2007,"10.1029/2007GL031409","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39549090178&doi=10.1029%2f2007GL031409&partnerID=40&md5=819b448f5387db4fb6e847b320fc6d1f","The spectrally resolved infrared radiances observed by AIRS provide a strict and insightfal test for general circulation models (GCMs). We compare the clear- and total-sky spectra simulated from the Geophysical Fluid Dynamics Laboratory GCM using a high resolution radiation code with the AIRS observations. After ensuring consistency in the sampling of the observed and simulated spectra and a proper representation of clouds in the radiance simulation, the observed and simulated global-mean radiances are shown to agree to within 2 K in the window region. Radiance discrepancies in the water vapor v2 (1300-1650 cm-1) and carbon dioxide v2 (650-720 cm-1) bands are consistent with the model biases in atmospheric temperature and water vapor. The existence of radiance biases of opposite signs in different spectral regions suggests that a seemingly good agreement of the model's broadband longwave flux with observations may be due to a fortuitous cancellation of spectral errors. Moreover, an examination of the diurnal difference spectrum indicates pronounced biases in the model-simulated diurnal hydrologic cycle over the tropical oceans, a feature seen to occur in other GCMs as well. Copyright 2007 by the American Geophysical Union."
"55113736500;35464731600;7003897194;","Examining feedbacks of aerosols to urban climate with a model that treats 3-D clouds with aerosol inclusions",2007,"10.1029/2007JD008922","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39449113126&doi=10.1029%2f2007JD008922&partnerID=40&md5=eb68a464fbcdf5dabb73d6d757265ad4","Anthropogenic aerosol particles alter clouds, radiation, and precipitation, thereby affecting weather, climate, and air pollution. To examine and understand such feedbacks, a module that simulates the evolution, movement, and microphysics of three-dimensional size-resolved mixed-phase clouds and precipitation and their multicomponent aerosol inclusions was developed and implemented into the GATOR-GCMOM global-through-urban air pollution-weather-climate model. A unique feature of the module is that aerosol particles and their chemical components are tracked in time and space within size-resolved liquid, ice, and graupel and interstitially within clouds. Modeled parameters were evaluated against in situ data, compared with MODIS climatologies, and nested with emission data down to 5 km resolution to study aerosol-cloud feedbacks in Los Angeles. Although updrafts are not resolved during deep convection at this resolution, most convection is shallow in Los Angeles. This resolution is also near the lower limit for which a hydrostatic solution to vertical momentum (used here) is similar to a nonhydrostatic solution. Aerosols in Los Angeles were found to increase cloud optical depth, cloud liquid water, cloud fraction, net downward thermal-infrared radiation, soil moisture, the relative humidity, and (slightly) middle-boundary layer air temperatures. Aerosols also decreased precipitation, surface solar, and near-surface temperatures. Both boundary layer warming due to black carbon and surface cooling due to all aerosol components increased stability, inhibiting cloud top growth under some conditions. Aerosols may feed back to themselves by increasing cloud liquid, gas dissolution, and aerosol volume upon evaporation. They may also decrease visibility by increasing the relative humidity and decrease photolysis below them by enhancing cloud thickness. Copyright 2007 by the American Geophysical Union."
"9249605700;","Environmental stability control of the intensity of squall lines under low-level shear conditions",2007,"10.1029/2007JD008793","https://www.scopus.com/inward/record.uri?eid=2-s2.0-49249098972&doi=10.1029%2f2007JD008793&partnerID=40&md5=ec380f26afc64850816aaef9c76827be","The environment for the development and evolution of linearly organized convective systems, i.e., squall lines is diverse for their existence in various climate regions. Understanding the behavior of squall lines under various environmental conditions is required for diagnosing and forecasting the development and intensity of the convective systems. The present study investigates the effects of environmental static stability on the squall-line intensity by conducting a systematic series of idealized cloud-resolving simulations of squall lines that develop in line-perpendicular, low-level westerly shear. Changing the temperature lapse rate with convective available potential energy (CAPE) being unchanged, we showed that the environmental stability in a convectively unstable layer well describes the intensity of the simulated squall lines. A less stable stability is favorable for generating stronger convective systems. The amount of CAPE does not account for the difference in the squall-line intensity in different temperature environments. An environment with a less static stability leads to the development of stronger cold pool, which will strongly controls the scale and strength of convective updrafts, the intensity of tropospheric overturning, and thus the organization and intensity of squall lines. The CAPE value can only be a good measure for diagnosing the development and intensity of the convective systems so long as the environmental static stability is identical. The static stability is a controlling parameter in determining the intensity of squall lines. Copyright 2007 by the American Geophysical Union."
"7003492327;","An adsorption model of insoluble particle activation: Application to black carbon",2007,"10.1029/2007JD008549","https://www.scopus.com/inward/record.uri?eid=2-s2.0-49249102893&doi=10.1029%2f2007JD008549&partnerID=40&md5=b74b45ab5e0080d3dc7228bd83320433","We present a model of insoluble particle activation based on a modification of the Köhler equation in which we introduce a term based on the activity of water adsorbed on the particle surface. We illustrate the model by application to activation data from black carbon (BC) particles. We parameterize the model using a free energy of adsorption that reflects the relative affinity for water vapor adsorbing on either the BC surface or the adsorbed water layer. This enables the parameterization of either chemically modified (hydrophilic) or graphitic (hydrophobic) BC. Several features of a suite of carbon activation data are captured by the model. In particular, upper and lower bounding curves are predicted for activation supersaturation as a function of diameter. We show a large body of recent activation data that all fall within these bounds. The model also predicts that activation of BC aerosol leads to activation diameters from 3 to 10 times smaller than activation of soluble particles of identical dry diameter. The activation of smaller particles may be expected to impact the size distribution of resulting cloud droplets and thus the aerosol first indirect effect on climate. Finally, we compare activation of BC aerosol as calculated with this model to activation of mixed particles of BC and ammonium sulfate. It is shown that for some range of the adsorption free energy a hydrophilic BC aerosol is predicted to activate at lower supersaturation than comparable mixed aerosol of low mass fraction in the soluble component, indicating the utility of a model of mixed particle activation based on the adsorption of water to form an interfacial solution."
"55717074000;7401936984;7003666669;","Evaluation of a new mixed-phase cloud microphysics parameterization with CAM3 single-column model and M-PACE observations",2007,"10.1029/2007GL031446","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39049089463&doi=10.1029%2f2007GL031446&partnerID=40&md5=6c09477193924a38ce918f3d5297aff3","Most global climate models generally prescribe the partitioning of condensed water into cloud droplets and cloud ice in mixed-phase clouds according to a temperature-dependent function, which affects modeled cloud phase, cloud lifetime and radiative properties. This study evaluates a new mixed-phase cloud microphysics parameterization (for ice nucleation and water vapor deposition) against the Atmospheric Radiation Measurement (ARM) Mixed-phase Arctic Cloud Experiment (M-PACE) observations using the NCAR Community Atmospheric Model Version 3 (CAM3) single column model (SCAM). It is shown that SCAM with the new scheme produces a more realistic simulation of the cloud phase structure and the partitioning of condensed water into liquid droplets against observations during the M-PACE than the standard SCAM. A sensitivity test indicates that ice number concentration could play an important role in the simulated mixed-phase cloud microphysics, and therefore needs be realistically represented in global climate models. Copyright 2007 by the American Geophysical Union."
"55547129338;36851768400;7401548835;7201706787;","Future regime shift in feedbacks during Arctic winter",2007,"10.1029/2007GL031826","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39049107431&doi=10.1029%2f2007GL031826&partnerID=40&md5=8d9f43cad46c48dd1fc4d9bb4e24517a","The Arctic is among the regions where climate is changing most rapidly today. Climate change is amplified by a variety of positive feedbacks, many of which are linked with changes in water vapor, cloud cover, and other cloud properties. We use a global climate model to examine several of these feedbacks, with a particular emphasis on determining whether there are significant temporal changes in these feedbacks that would make them stronger or weaker during the 21st century. The model results indicate that one of the significant positive feedbacks on Arctic surface air temperature in winter weakens substantially toward the end of the 21st century. The feedback loop begins with a temperature increase that produces increases in water vapor, cloud cover, and cloud optical depth which increase the downward longwave flux by 30 Wm-2 by 2060 which then increases the surface air temperature. Copyright 2007 by the American Geophysical Union."
"13403689700;9271096600;7006434689;7006377579;6701842515;9043417100;57195257572;7201787800;7006235542;7005069415;","Aerosol partitioning between the interstitial and the condensed phase in mixed-phase clouds",2007,"10.1029/2007JD008714","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38949173893&doi=10.1029%2f2007JD008714&partnerID=40&md5=4ee7e198dbe156149a53ee8a5fab795a","The partitioning of aerosol particles between the cloud and the interstitial phase (i.e., unactivated aerosol) has been investigated during several Cloud and Aerosol Characterization Experiments (CLACE-3, CLACE-3 1/2 and CLACE-4) conducted in winter and summer 2004 and winter 2005 at the high alpine research station Jungfraujoch (3580 m altitude, Switzerland). Ambient air was sampled using different inlets in order to determine the activated fraction of aerosol particles, F<inf>N</inf>, defined as the fraction of the total aerosol number concentration (with particle diameter d<inf>p</inf> > 100 nm) that has been incorporated into cloud particles. The liquid and ice water content of mixed-phase clouds were characterized by analyzing multiple cloud probes. The dependence of the activated fraction on several environmental factors is discussed on the basis of more than 900 h of in-cloud observations and parameterizations for key variables are given. F<inf>N</inf> is found to increase with increasing liquid water content and to decrease with increasing particle number concentration in liquid clouds. F<inf>N</inf> also decreases with increasing cloud ice mass fraction and with decreasing temperature from 0 to -25°C. The Wegener-Bergeron-Findeisen process probably contributed to this trend, since the presence of ice crystals causes liquid droplets to evaporate, thus releasing the formerly activated particles back into the interstitial phase. Ice nucleation could also have prevented additional cloud condensation nuclei from activating. The observed activation behavior has significant implications for our understanding of the indirect effect of aerosols on climate. Copyright 2007 by the American Geophysical Union."
"15835359300;6602415076;6701620591;7004741554;6602661960;57212368685;6602699701;11141437800;","A method for reconstruction of past UV radiation based on radiative transfer modeling: Applied to four stations in northern Europe",2007,"10.1029/2007JD008454","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38949192000&doi=10.1029%2f2007JD008454&partnerID=40&md5=db4caf6b68f324e5587df4d81e4a16c4","A method for reconstruction of past UV radiation has been developed. The idea of the method is to use measurements of global radiation (300-3000 nm) for determining the influence of clouds on UV radiation. In order to transfer the information contained in the global radiation data into a cloud effect in the UV range, a so-called cloud modification table was developed, which is based on physical relationships determined through radiative transfer calculations. The method was given as input the measured global radiation and total ozone column, the total water vapor column from the ERA-40 data set, the surface albedo as estimated from snow depth, and the altitude of the location. Using this method, erythemally weighted UV irradiances were reconstructed back to the early 1980s at four stations in northern Europe: Bergen in Norway, Norrköping in Sweden, and Jokioinen and Sodankylä in Finland. The reconstructed daily UV doses are in good agreement with measurements. For the summer season, the systematic error was found to vary between 0% at Bergen and 4% at Jokioinen, and the correlation coefficient was 0.99 at all stations. The summer root-mean-square error was 5% at all stations except Jokioinen, where it was 9%. The method performs well also for spring and autumn, whereas for winter conditions of low Sun, a systematical underestimation was found. A large part of this underestimation was found to be due to the plane-parallel approximation used in the radiative transfer calculations. The time series of reconstructed UV exhibit a clear increase since the early 1980s at both Sodankylä (4.1%/decade; statistically significant) and Norrköping (3.3%/decade; not significant). At Jokioinen, a weak increase was found, while at Bergen there was no considerable overall change. At both Sodankylä and Norrköping, the increase in the reconstructed UV radiation was primarily driven by an increase in the global radiation, that is, by decreased cloudiness. The method is general in the sense that it can be applied also to other stations. Copyright 2007 by the American Geophysical Union."
"7102038796;16308669200;16310647400;57214587969;22986679200;22987209500;","Analyses of growth rings of Pinus merkusii from Lao P.D.R.",2007,"10.1016/j.foreco.2007.07.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36148976787&doi=10.1016%2fj.foreco.2007.07.018&partnerID=40&md5=34d46713484c79927f61c5156ef46ee3","We present the first tree-ring chronologies of total ring width (RW), earlywood width (EWW) and latewood width (LWW) from Lao P.D.R., from 52 core samples from 26 mature pines (Pinus merkusii Junghuhn & De Vriese), from Phu Khao Khouay National Biodiversity Conservation Area northeast of Vientiane. The chronologies span the 262-year period from 1743 to 2005 a.d., and at least for RW and LWW exhibit strong signal strength back to the late 1700s. Correlation analyses with climate data from a composite of 13 nearby stations in Thailand indicate statistically significant (p ≤ 0.05) negative correlation with prior year June rainfall, and positive correlation with August-September maximum temperature. Annual radial increment is also significantly negatively correlated with percent cloud fraction, leading us to believe that growth may be adversely affected by light availability (i.e., reduced growth during periods of low light) and not positively affected by high temperature per se. Spatial correlation with sea surface temperature fields highlights the influence of the central and eastern tropical Pacific Ocean, particularly for EWW. Wavelet analysis reveals multi-decadal scale variability between 30 and 60 years for all three indices, and higher frequency power for RW and LWW between 2 and 7 years, the typical range of ENSO. While RW, EWW and LWW all appear to respond to monsoon climate, we highlight the need for far more detailed ecophysiological response studies for this species, particularly with regard to the role of light availability and temperature during the peak monsoon. © 2007 Elsevier B.V. All rights reserved."
"14627622500;7004598032;23090174200;35578212100;","Measurements of transpiration in four tropical rainforest types of north Queensland, Australia",2007,"10.1002/hyp.6576","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37549068132&doi=10.1002%2fhyp.6576&partnerID=40&md5=4f5ee4d1b091fbd63ee55ffae8b4a68d","Transpiration of four different rainforest types in north Queensland, Australia, was determined using the heat pulse technique for periods ranging between 391 and 657 days. Despite the complexity of the natural rainforest systems being studied, the relationship between sample tree size and daily water use was found to be strong, thus providing a robust means by which to scale transpiration from individual trees to the entire forest stand. Transpiration was shown to be dependent on solar radiation and atmospheric demand for moisture with little evidence of limitation by soil moisture supply. Total stand transpiration was controlled by forest characteristics such as stem density, size distribution and sapwood area. Annual transpiration for each of the four sites ranged between 353 mm for cloud forest and 591 mm for montane rainforest. In comparison with the international literature, transpiration from Australian rainforests is low; the reasons for this could be related to a combination of differences in forest structure, climatic conditions, canopy wetness duration and tree physiology. Copyright © 2007 John Wiley & Sons, Ltd."
"6603408978;7004794838;7201671604;","Functional relationships between denudation andhillslope form and relief",2007,"10.1016/j.epsl.2007.09.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36049011982&doi=10.1016%2fj.epsl.2007.09.035&partnerID=40&md5=4650e32ac556409e129a7307eb53964f","Functional relationships between landscape morphology and denudation rate allow for the estimation of sediment fluxes using readily available topographic information. Empirical studies of topography-erosion linkages typically employ data with diverse temporal and broad spatial scales, such that heterogeneity in properties and processes may cloud fundamental process-scale feedbacks between tectonics, climate, and landscape development. Here, we use a previously proposed nonlinear model for sediment transport on hillslopes to formulate 1-D dimensionless functions for hillslope morphology as well as a generalized expression relating steady-state hillslope relief to erosion rate, hillslope transport parameters, and hillslope length. For study sites in the Oregon Coast Range and Gabilan Mesa, CA, model predictions of local relief and average hillslope gradient compare well with values derived from high-resolution topographic data acquired via airborne laser altimetry. Our formulation yields a nondimensional number describing the extent to which the nonlinearity in our gradient-flux model affects slope morphology and landscape response to tectonic and climatic forcing. These results should be useful for inferring rates of hillslope denudation and sediment flux from topography, or for coarse-scale landscape evolution simulations, in that first-order hillslope properties can be calculated without explicit modeling of individual hillslopes. © 2007 Elsevier B.V. All rights reserved."
"6602112847;7005135192;7102015136;","Where to now? A synthesis of current views of the CLAW hypothesis",2007,"10.1071/EN07082","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36849083434&doi=10.1071%2fEN07082&partnerID=40&md5=8299f405f5eb2483840bd5756604d35f","The CLAW hypothesis was published 20 years ago, building on suggestions that the sulfur cycle provided a natural feedback mechanism whereby plankton in the ocean had a role in modifying climate by providing the precursors for cloud condensation nuclei, which leads to the formation of high albedo clouds. In this issue, the 10 preceding articles represent the opinions of several leading scientists working on various aspects of the CLAW hypothesis and here we synthesise these varied opinions to answer the questions: Does the CLAW hypothesis operate as described in the original 1987 publication? and What steps and advances are needed to better understand CLAW and resolve any outstanding areas of difficulty?"
"8941441300;8941441100;7402727711;12762518000;12761855700;8941441200;","Macro- and micro-structures of heavy fogs and visibility in the Dayaoshan expressway",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-36849063069&partnerID=40&md5=6a79f5c0b8d3fcbf58f2f9ecc9a82ac8","Belonging to the southern subtropical moist type of monsoon climate, the Nanling mountainous area experiences heavy fogs whenever quasi-stationary fronts appear there from September to May. There can be as many as 15-18 days of heavy fogs per month. Fogs have more serious consequences in the Lechang-Ruyuan section of the Beijing-Zhuhai Expressway (the longest expressway in China) that passes through the main part of the Nanling Mts., where the road rises from 200 m to more than 800 m above sea level (ASL). For a major motorway in the mountainous areas of Nanling Mts., two multidisciplinary integrated field observations were carried out, which measured visibility by the naked eyes, visibility by instrument, spectrum of fogdrops, liquid water content (LWC) of fog, tethered sounding, dual-parameter low-level sounding, turbulence diffusion within fog layers, aerosol spectra of size and composition, sampled fog water compositions, and sampled rainwater compositions. Typical cases were probed for their analyses of synoptics, micro- and macro-structures and microphysics. It is understood that heavy fogs take place with high frequency in the area and bring about serious consequences. Being typical advection and upslope fogs, they are in essence low-lying clouds appearing at high altitudes, which are closely related with the activity of South China frontal processes, especially the South China quasi-stationary fronts, and reflect on the role of local terrain as well. The heavy fogs are characteristic of long duration, extremely low visibility, well-organized lumpshaped structure, large-size fog-drops, moderate concentration, high LWC, and stronger turbulent diffusion within the fog layers than in fine sky. They differ much from radiation fogs, which are better documented in previous study in China. It is found that fog LWC is in significant anti-correlation with visibility so that large LWC is associated with small visual range. It is also noted that one of the reasons for the fluctuation of characteristic quantities of micro-structure such as the LWC of fog in the area is, in addition to the inhomogeneous structure of the fog itself, the effect of advection and inhomogeneous underlying surface; during the translation of fog with the ambient wind, irregular upslope and cross-over movement is another reason for the inhomogeneous structure and fluctuation of fog. The spectrum of the aerosol size displays itself as the power function of monotonous descent. The concentration of submicrometer particles is even higher. The high-concentration sulfate particles found in the aerosols of Nanling Mts. are actually good nuclei for condensation, which are favorable for the formation of fog. The presence of fog can help cleanse the trace compositions in the atmosphere so that fog droplets contain high levels of polluting elements. In the meantime, compared to cloud droplets, fog droplets are easier to be captured by the vertical surfaces of objects on the land surface, such as vegetation and buildings to constitute another kind of cleansing process. In vast stretches of forest like the Nanling Mts., this kind of cleansing may be quite important. Studying the characteristic variation of fogs in the area realistically assists in setting up a forecast and warning system for local fogs and provides basic information for fog dispersal experiments."
"7103363111;7103219776;55665325500;7101808591;","Ice, Cloud, and land Elevation Satellite (ICESat) over Arctic sea ice: Retrieval of freeboard",2007,"10.1029/2006JC003978","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38949133045&doi=10.1029%2f2006JC003978&partnerID=40&md5=435f9a5b47c045d153c55cf9d5c55048","Total freeboard (snow and ice) of the Arctic Ocean sea ice cover is derived usmig Ice, Cloud, and land Elevation Satellite (ICESat) data from two 35-day periods: one during the fall (October-November) of 2005 and the other during the winter (February- March) of 2006. Three approaches are used to identify near-sea-surface tiepoints. Thin ice or open water samples in new openings, typically within 1-2 cm of the sea surface, are used to assess the sea surface estimates. Results suggest that our retrieval procedures could provide consistent freeboard estimates along 25-km segments with uncertainties of better than 7 cm. Basin-scale composites of sea ice freeboard show a clear delineation of the seasonal ice zone in the fall. Overall, the mean freeboards of multiyear (MY) and first-year (FY) ice are 35 cm and 14 cm in the fall, and 43 cm and 27 cm in the winter. The increases of ∼9 cm and ∼12 cm on MY and FY sea ice are associated with the 4 months of ice growth and snow accumulation between data acquisitions. Since changes in snow depth account for >90% of the seasonal increase in freeboard on MY ice, it dominates the seasonal signal. Our freeboard estimates are within 10 cm of those derived from available snow/ice thickness measurements from ice mass balance buoys. Examination of the two residual elevations fields, after the removal of the sea ice freeboard contribution, shows coherent spatial patterns with a standard deviation (S.D.) of ∼23 cm. Differencing them reduces the variance and gives a near random field with a mean of ∼2 cm and a standard deviation of ∼14 cm. While the residual fields seem to be dominated by the static component of unexplained sea surface height and mean dynamic topography (S.D. ∼23 cm), the difference field reveals the magnitude of the time-varying components as well as noise in the ICESat elevations (S.D. ∼10 cm). Copyright 2007 by the American Geophysical Union."
"7101689290;7003984663;6602470643;6602494584;55667807200;","Cloud water in windward and leeward mountain forests: The stable isotope signature of orographic cloud water",2007,"10.1029/2007WR006011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38549122407&doi=10.1029%2f2007WR006011&partnerID=40&md5=0b95fdfaa7928fc0f00a282362030024","Cloud water can be a significant hydrologic input to mountain forests. Because it is a precipitation source that is vulnerable to climate change, it is important to quantify amounts of cloud water input at watershed and regional scales. During this study, cloud water and rain samples were collected monthly for 2 years at sites on windward and leeward East Maui. The difference in isotopic composition between volume-weighted average cloud water and rain samples was 1.4‰ δ18O and 12‰ δ2H for the windward site and 2.8‰ δ18O and 25‰ δ2H for the leeward site, with the cloud water samples enriched in 18O and 2H relative to the rain samples. A summary of previous literature shows that fog and/or cloud water is enriched in 18O and 2H compared to rain at many locations around the world; this study documents cloud water and rain isotopic composition resulting from weather patterns common to montane environments in the trade wind latitudes. An end-member isotopic composition for cloud water was identified for each site and was used in an isotopic mixing model to estimate the proportion of precipitation input from orographic clouds. Orographic cloud water input was 37% of the total precipitation at the windward site and 46% at the leeward site. This represents an estimate of water input to the forest that could be altered by changes in cloud base altitude resulting from global climate change or deforestation."
"14018722800;","Seasonal and latitudinal features of the greenhouse effect in Russia",2007,"10.3103/S1068373907120023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43649087985&doi=10.3103%2fS1068373907120023&partnerID=40&md5=109a1db67169cedc18a2ea7805193374","The annual cycle of air temperature trends is analyzed in comparison with total cloud amount trends. It is shown that during the last 30 years the cloud amount changes were associated with air temperature trends with positive and negative correlation in cold and warm half-year, respectively, which is in perfect agreement with the well-known facts of the influence of clouds on radiation balance and of the latter on temperature regime of the atmosphere. In all cases, the greenhouse effect increases when the radiation budget is nearly zero due to physical-geographic features; the small contribution of the greenhouse effect to the budget change manifests itself in climate changes. A conclusion is drawn on the presence of a greenhouse component of CO2 in the phenomena described; however, in the high latitudes, this effect is exceeded by long-term changes in cloud amount. © Allerton Press, Inc. 2007."
"6701752471;7005920812;55737616800;23393856300;23392868000;","Elucidating model inadequacies in a cloud parameterization by use of an ensemble-based calibration framework",2007,"10.1175/2007MWR2008.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38049164191&doi=10.1175%2f2007MWR2008.1&partnerID=40&md5=6ce44538e1f2dc01c339d0026cc9000d","Every cloud parameterization contains structural model errors. The source of these errors is difficult to pinpoint because cloud parameterizations contain nonlinearities and feedbacks. To elucidate these model inadequacies, this paper uses a general-purpose ensemble parameter estimation technique. In principle, the technique is applicable to any parameterization that contains a number of adjustable coefficients. It optimizes or calibrates parameter values by attempting to match predicted fields to reference datasets. Rather than striving to find the single best set of parameter values, the output is instead an ensemble of parameter sets. This ensemble provides a wealth of information. In particular, it can help uncover model deficiencies and structural errors that might not otherwise be easily revealed. The calibration technique is applied to an existing single-column model (SCM) that parameterizes boundary layer clouds. The SCM is a higher-order turbulence closure model. It is closed using a multivariate probability density function (PDF) that represents subgrid-scale variability. Reference datasets are provided by large-eddy simulations (LES) of a variety of cloudy boundary layers. The calibration technique locates some model errors in the SCM. As a result, empirical modifications are suggested. These modifications are evaluated with independent datasets and found to lead to an overall improvement in the SCM's performance. © 2007 American Meteorological Society."
"25226620200;7005485117;9249731200;","Prediction of the diurnal cycle using a multimodel superensemble. Part II: Clouds",2007,"10.1175/2007MWR2080.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35748953588&doi=10.1175%2f2007MWR2080.1&partnerID=40&md5=c0ff6d50e2bf4c3d39f94740f60fb5e0","This study addresses the issue of cloud parameterization in general circulation models utilizing a twofold approach. Four versions of the Florida State University (FSU) global spectral model (GSM) were used, including four different cloud parameterization schemes in order to construct ensemble forecasts of cloud covers. Next, a superensemble approach was used to combine these model forecasts based on their past performance. It was shown that it is possible to substantially reduce the 1-5-day forecast errors of phase and amplitude of the diurnal cycle of clouds from the use of a multimodel superensemble. Further, the statistical information generated in the construction of a superensemble was used to develop a unified cloud parameterization scheme for a single model. This new cloud scheme, when implemented in the FSU GSM, carried a higher forecast accuracy compared to those of the individual cloud schemes and their ensemble mean for the diurnal cycle of cloud cover up to day 5 of the forecasts. This results in a 5-10 W m-2 improvement in the root-mean-square error to the upward longwave and shortwave flux at the top of the atmosphere, especially over deep convective regions. It is shown that while the multimodel superensemble is still the best product in forecasting the diurnal cycle of clouds, a unified cloud parameterization scheme, implemented in a single model, also provides higher forecast accuracy compared to the individual cloud models. Moreover, since this unified scheme is an integral part of the model, the forecast accuracy of the single model improves in terms of radiative fluxes and thus has greater impacts on weather and climate time scales. This new cloud scheme will be tested in real-time simulations. © 2007 American Meteorological Society."
"7404334532;7405727977;6604021707;16304578900;7006399110;36705143500;56203249800;12241892400;35561911800;7401548835;9242539000;22978151200;16303438900;57126848900;7004409909;7102886537;55339475000;56277667200;57193132723;12240390300;7005474099;57203048291;7402484050;34770976500;16304488000;9242540400;57191693467;56249704400;6602859414;57192185620;7201837768;7006167299;6506806004;55403720400;6701348935;7006550762;12763470600;16305478500;7004214645;57206416522;56528677800;7006461606;55408944000;12763581600;14829673100;7403318365;56099064600;","Climate simulations for 1880-2003 with GISS modelE",2007,"10.1007/s00382-007-0255-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548075852&doi=10.1007%2fs00382-007-0255-8&partnerID=40&md5=b65f600032df1aa7ce3a2751b19bcf67","We carry out climate simulations for 1880-2003 with GISS modelE driven by ten measured or estimated climate forcings. An ensemble of climate model runs is carried out for each forcing acting individually and for all forcing mechanisms acting together. We compare side-by-side simulated climate change for each forcing, all forcings, observations, unforced variability among model ensemble members, and, if available, observed variability. Discrepancies between observations and simulations with all forcings are due to model deficiencies, inaccurate or incomplete forcings, and imperfect observations. Although there are notable discrepancies between model and observations, the fidelity is sufficient to encourage use of the model for simulations of future climate change. By using a fixed well-documented model and accurately defining the 1880-2003 forcings, we aim to provide a benchmark against which the effect of improvements in the model, climate forcings, and observations can be tested. Principal model deficiencies include unrealistically weak tropical El Nino-like variability and a poor distribution of sea ice, with too much sea ice in the Northern Hemisphere and too little in the Southern Hemisphere. Greatest uncertainties in the forcings are the temporal and spatial variations of anthropogenic aerosols and their indirect effects on clouds. © Springer-Verlag 2007."
"7004003763;7201504886;7202762223;7202381052;35473805400;23491331000;22975069200;7404521962;7801634218;6602765265;7004084412;57202521210;9535817700;7006901405;23491463000;55896920900;7005886535;55454856700;7004885872;25953950400;6602111828;6701590980;7202185413;22953316500;7103337730;35393120300;7402565763;6603431534;55663817800;7103119050;23019327900;23492864500;57203054678;14020513000;7402049334;6603566335;12645126500;7003406689;57209341911;7202408732;7004198777;7005035762;","Rain in shallow cumulus over the ocean: The RICO campaign",2007,"10.1175/BAMS-88-12-1912","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38949157156&doi=10.1175%2fBAMS-88-12-1912&partnerID=40&md5=33943f54e6cff57e91da132737d69a0f","Shallow, maritime cumuli are ubiquitous over much of the tropical oceans, and characterizing their properties is important to understanding weather and climate. The Rain in Cumulus over the Ocean (RICO) field campaign, which took place during November 2004-January 2005 in the trades over the western Atlantic, emphasized measurements of processes related to the formation of rain in shallow cumuli, and how rain subsequently modifies the structure and ensemble statistics of trade wind clouds. Eight weeks of nearly continuous S-band polarimetric radar sampling, 57 flights from three heavily instrumented research aircraft, and a suite of ground- and ship-based instrumentation provided data on trade wind clouds with unprecedented resolution. Observational strategies employed during RICO capitalized on the advances in remote sensing and other instrumentation to provide insight into processes that span a range of scales and that lie at the heart of questions relating to the cause and effects of rain from shallow maritime cumuli. © 2008 American Meteorological Society Privacy Policy and Disclaimer."
"6602506180;7003627515;6603888932;","Strong-wind events and their impact on the near-surface climate at Kohnen Station on the Antarctic Plateau",2007,"10.1017/S095410200700065X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35848945093&doi=10.1017%2fS095410200700065X&partnerID=40&md5=50c44d33140b4d9bede5f14f44e83da8","Strong-wind events occur 10-20 times per year at Kohnen Station, East Antarctica (75°00'S, 0°04'E, 2892 m above sea level), and are often caused by warm-core cyclones in the north-eastern Weddell Sea. An uncommon event occurred in January 2002, when blocking both in the south Atlantic Ocean and in the south Tasman Sea caused a split-up of the circumpolar vortex, and large amounts of heat and moisture were transported onto the Antarctic Plateau. During strong-wind events over the plateau the near-surface temperature can increase by tens of degrees, which is partly caused by the advection of heat, but for an important part by the destruction of the stable temperature-deficit layer by enhanced vertical mixing. The temperature rise is larger during the winter/night than during the summer/day, due to a better-developed temperature deficit. Snowdrift during the January 2002 event linearly increased surface roughness for momentum with friction velocity, for values over about 0.18 m s-1. The cloud cover during the event reduced down-welling solar radiation by 32%, and increased the albedo from about 0.86 to 0.92. Changes in longwave radiation largely cancelled the daytime changes in shortwave radiation, thus net radiation was most affected at night. © 2007 Antarctic Science Ltd."
"6603415336;22951673500;23972292000;7006702222;","Instability of copronecrophagous beetle assemblages (Coleoptera: Scarabaeinae) in a mountainous tropical landscape of Mexico",2007,"10.1603/0046-225X(2007)36[1397:IOCBAC]2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40549098389&doi=10.1603%2f0046-225X%282007%2936%5b1397%3aIOCBAC%5d2.0.CO%3b2&partnerID=40&md5=1588f1c5d0d95a92c1d91b03c643c3aa","We analyzed changes over time in species composition and functional guild structure (temporal beta diversity) for natural assemblages and those modified by humans in a fragmented, tropical mountain landscape. The assemblages belong to cloud forests (the original vegetation type), secondary forests, traditional shaded coffee plantations, commercial shaded coffee plantations, and a cattle pasture. Copronecrophagous beetles, subfamily Scarabaeinae (Insecta: Coleoptera: Scarabaeidae), were used as the indicator group. This group has been used in previous studies and other tropical forests and has been found to be a good indicator of the effects of anthropogenic change. For each assemblage, we compared samples that were collected several years apart. Changes were found in species composition, order of abundance, and in the proportion that a given species is present in the different functional groups. The changes that occurred between samplings affected the less abundant species in the cloud forest and in the pasture. In the other vegetation types, both abundant and less abundant species were affected. Their order of abundance and proportion in the different guilds also changed. This study shows that, although landscape richness remains relatively constant, richness at the local level (alpha diversity) changes notably even over short lapses of time. This could be a characteristic of landscapes with intermediate degrees of disturbance (such as those that have been partially modified for human use), where assemblage composition is very fluid. © 2007 Entomological Society of America."
"14627622500;35578212100;7004598032;23090174200;6701392449;","Water balance of tropical rainforest canopies in north Queensland, Australia",2007,"10.1002/hyp.6618","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37249063618&doi=10.1002%2fhyp.6618&partnerID=40&md5=848c479911381e67d4ef3e0199a82d32","The water balance of four different rainforest types in the Wet Tropics region of north Queensland is inferred from measurements of canopy hydrological components undertaken for periods between 391 to 657 days. These measurements of rainfall, cloud interception, stem-flow, throughfall, canopy interception and transpiration have revealed considerable differences in the canopy water balance of different locations as a result of forest structural differences, altitude, exposure and climate. Cloud interception is a significant extra input of water to forests at high altitude sites (&gt;1000 m) and varies between 7 and 29% of the total water input. At coastal and lower montane rainforests annual total evaporation is consistently around 50% of the total water input, but in upper montane cloud forest this drops dramatically to only 13% of the water input. At all sites actual evaporation is greater than potential evaporation for most of the year and on an annual basis exceeds potential by between 2 and 53%. The source of this additional energy is uncertain, but is likely to come from advection. Annual interception at all the rainforest sites was greater than annual transpiration, with transpiration dominating in the dry season and interception dominating in the wet season. All of the rainforests have a large annual net water balance to sustain runoff and recharge. Towards the end of the dry season runoff and recharge can cease in coastal lowland and lower mountain forests and they may have to draw on soil moisture and/or ground water at this time. In contrast, upper montane cloud forests have a positive net water balance throughout the year and are therefore an important source of dry seasoruiver flows. Furthermore, their exceptionally large annual runoff. (∼ 6500 mm year-1) is a major source of downstream water. Copyright © 2007 John Wiley &amp; Sons, Ltd."
"6507224579;7006184606;","A tropical and subtropical land-sea-atmosphere drought oscillation mechanism",2007,"10.1175/2007JAS2186.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38349156762&doi=10.1175%2f2007JAS2186.1&partnerID=40&md5=3903f0bda35685944af9d3b5f1cd6207","A two-column atmospheric model on a land-sea interface is studied. The model has sophisticated convection, cloud, and radiation schemes, a mixed layer ocean, and a bucket model to simulate land hydrology. A self-sustained oscillation in soil moisture with a period on the order of months is found. This oscillation is strongest when the model is run with parameters chosen to correspond to the and subtropics. The effect of changing model parameters on the oscillation is explored. The existence and qualitative behavior of the oscillation are relatively robust to changes in model parameters. © 2007 American Meteorological Society."
"55498964300;57139379600;36725898200;26643193200;","Terrestrial growth in China and its relationship with climate based on the MODIS data",2007,"10.1016/S1872-2032(08)60015-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38549165866&doi=10.1016%2fS1872-2032%2808%2960015-3&partnerID=40&md5=7021db9bddf8929041a3e2a0c385ce6f","The characteristics of terrestrial growth in China and its relationship with various climatic factors (e.g. temperature, precipitation and radiation) were investigated by using the data collected with the Moderate Resolution Imaging Spectroradiometer (MODIS). These data were collected once every 8 days during 2000-2003 and then again in 2005. The average annual gross primary production (GPP) in China during this period ranged from 0 to 3252.6 gC·m-2·a-1 with an average value of 491.1 gC·m-2·a-1. The maximum GPP values were observed over the regions of Yunnan, Hainan and Taiwan, and the southeast coastal areas, while the minimum values were observed in the cold and arid regions of the Tibetan Plateau, Xinjiang and Inner Mongolia. Correlation analysis showed that temperature was the primary factor influencing this terrestrial growth, while precipitation played a secondary role. However, only the terrestrial growth that occurred in southern China was affected by radiation. The correlation coefficients of GPP with temperature and precipitation decreased from northern to southern China and were negatively correlated with the distribution of the associated climatic factors within China. Furthermore, the correlation coefficient of GPP with cloud contents was observed to increase from northern to southern China. © 2007 Ecological Society of China."
"57118434000;56141544400;57192495556;55506700500;","Numerical study on microphysical processes of two different snowfall cases in northern China",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-39649109880&partnerID=40&md5=d338013eadbc2c33cfa44a871ba69265","In this paper, two snowfall cases under different weather conditions in northern China are simulated by using the meso scale model MM5. Two-way nesting structure of domains is designed for each case. Among the explicit schemes of MM5, the Reisner graupel scheme is selected to describe the microphysical process. The simulated snow-bands of two cases are basically consistent with observations. The simulated results of microphysical processes axe mainly discussed. The hydrometeors and their sources and sinks under different weather backgrounds are described. The feedback effects of microphysical processes on the thermal and dynamic processes are also discussed. Method that outputs the accumulative sources and sinks per hour is used to analyze the distribution characteristics of hydrometeors during the strongest snowfall period. Two sensitivity tests (called heat test and drag test) are conducted to examine the effects of microphysical processes on cloud produced by the latent heat and drag force. Results have shown that the distribution of particles has a close relation with temperature. The temperature of Beijing snowfall is under 0°C and there exist vapor and solid phase particles, while Liaoning snowfall has vapor, liquid, and solid phase particles due to the warm temperature. The distribution of these particles is not the same at different development stages. From the analyses of the characteristics of sources and sinks, it is found that snow is mainly produced by the deposition and accretion with ice. Cloud water is crucial to graupel. The melting of ice-phase particles enhances the rain production. The results of heat tests and drag tests reveal that the microphysical processes have interacted with the dynamic and thermal processes. Latent heat release of hydrometeors feeds back positively on snowfall while the drag force not. At last, comparisons of simulated results have been done between the two different kinds of snowfall cases. The microphysical processes of Liaoning snowfall case is more complicated than those of Beijing snowfall case. The values of the cloud variables are larger and the interactions between the microphysical processes and the thermal and dynamic processes of Liaoning snowfall case are stronger than those of Beijing snowfall case."
"23028838900;7004877677;55188785600;55728968600;","The suburban energy balance in Miami, Florida",2007,"10.1111/j.1468-0459.2007.00329.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36549069074&doi=10.1111%2fj.1468-0459.2007.00329.x&partnerID=40&md5=be3ebee5ee1ed4c0bf248f81e7c169d3","Summertime measurements of local scale energy balance of a suburban site in west Miami, Florida, in 1995 are presented. All of the radiation and turbulent heat fluxes were measured directly. In addition several derived surface characteristics are calculated including the albedo, radiation temperature, emissivity, aerodynamic and canopy resistances, Bowen's ratio, Priestley-Taylor and McNaughton-Jarvis coefficients. The results are used to test parameterizations to calculate several heat fluxes. Most radiation fluxes can be calculated with simple schemes in cloudless conditions but the spatial and temporal variability of cloud degrades results greatly. This highlights the value of observing incoming solar radiation since it can form an excellent surrogate for daytime net all-wave radiation in all sky conditions. The heat flux results for this warm, wet subtropical site demonstrate similarities with those from similarly developed locations in temperate climates. Interestingly this finding includes the fraction of energy used in evaporation. It is thought that this may be related to the relatively large heat storage in Miami which may reflect the presence of wet soils and free-standing water, the persistently low vapor pressure deficits (7-14 hPa) typical of this humid climate and the relatively poor coupling between the surface and the whole planetary boundary layer due to relatively low surface roughness. © 2007 Swedish Society for Anthropology and Geography."
"6602523178;7005647953;6508177249;7402851442;6602124129;7006073550;7006099341;","Chronotopographic analysis directly from point-cloud data: A method for detecting small, seasonal hillslope change, Black Mesa Escarpment, NE Arizona",2007,"10.1130/GES00110.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46149126684&doi=10.1130%2fGES00110.1&partnerID=40&md5=66935fa0c5e010eff4285c254ce23620","The advent of high-resolution, precise, back-pack portable terrestrial lidar scanners (TLS) provides a revolutionary new tool for obtaining quantitative, high-resolution (2-mm to 30-mm point spacing) measurements of landscape surface features. Moreover, data collected using these instruments allow observation of geomorphic processes in systems that can experience change on a daily basis. We have introduced TLS techniques in ongoing investigations of semiarid landscapes associated with weakly cemented sandstones along part of the Black Mesa escarpment of NE Arizona. Clay-cemented, Jurassic sandstones exposed along this escarpment are sensitive to moisture, and thus climate, via hydration-expansion weathering of interstitial clay. Sediment shed from weathered slopes has caused locally rapid valley fl oor aggradation and upper basin slope vertical denudation rates of 2-3 mm/yr over 10- to 100-yr timescales, as indicated by dendrochronology coupled with soil geomorphic analysis. These rates suggest rapid hillslope denudation rates. Employing the University of New Mexico Lidar Laboratory Optech Ilris 3D TLS, we are constructing a high-resolution model of two major basins along the escarpment. Focusing on a single, small (30 × 60 m) area of a mostly non-vegetated, steep slope (>35°), we demonstrate in this paper a method of comparative analysis of pointcloud data sets that can detect subcentimeter change resulting from a single season of monsoon precipitation along the escarpment. Using repeat scans can provide an empirical evaluation of single season erosion rates in the study site, and because our observations are geospatial in nature, we can also document the parts of the slopes that make the greatest contribution to local valley fl oor aggradation. In demonstrating the utility of this method, we expect that continued investigation of this site will provide insight to the key processes associated with soil-mantled versus bedrockdominated slopes during modern escarpment retreat and hillslope modifi cation, which, in turn, may further elucidate the impacts of Holocene climate change on this rapidly evolving landscape. © 2007 Geological Society of America."
"7201972249;7004048039;6603665315;57210540117;6602793307;","The operational GFDL coupled Hurricane-Ocean prediction system and a summary of its performance",2007,"10.1175/2007MWR2032.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38049168888&doi=10.1175%2f2007MWR2032.1&partnerID=40&md5=b3b84d1fbda79f52c8199bce612f2832","The past decade has been marked by significant advancements in numerical weather prediction of hurricanes, which have greatly contributed to the steady decline in forecast track error. Since its operational implementation by the U.S. National Weather Service (NWS) in 1995, the best-track model performer has been NOAA's regional hurricane model developed at the Geophysical Fluid Dynamics Laboratory (GFDL). The purpose of this paper is to summarize the major upgrades to the GFDL hurricane forecast system since 1998. These include coupling the atmospheric component with the Princeton Ocean Model, which became operational in 2001, major physics upgrades implemented in 2003 and 2006, and increases in both the vertical resolution in 2003 and the horizontal resolution in 2002 and 2005. The paper will also report on the GFDL model performance for both track and intensity, focusing particularly on the 2003 through 2006 hurricane seasons. During this period, the GFDL track errors were the lowest of all the dynamical model guidance available to the NWS Tropical Prediction Center in both the Atlantic and eastern Pacific basins. It will also be shown that the GFDL model has exhibited a steady reduction in its intensity errors during the past 5 yr, and can now provide skillful intensity forecasts. Tests of 153 forecasts from the 2004 and 2005 Atlantic hurricane seasons and 75 forecasts from the 2005 eastern Pacific season have demonstrated a positive impact on both track and intensity prediction in the 2006 GFDL model upgrade, through introduction of a cloud microphysics package and an improved air-sea momentum flux parameterization. In addition, the large positive intensity bias in sheared environments observed in previous versions of the model is significantly reduced. This led to the significant improvement in the model's reliability and skill for forecasting intensity that occurred in 2006. © 2007 American Meteorological Society."
"6701569731;","Andrija Mohorovičić as a meteorologist",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-67149139740&partnerID=40&md5=825ea66758ce68038b9d947ac48f85a1","Andrija Mohorovičić's meteorology-related activities are reviewed. It is shown that he was involved in teaching and professional work in meteorology throughout his professional career, and in meteorological research until his early forties - i.e. before switching to seismological research and arriving at the famous discovery of discontinuity between the Earth's crust and its mantle. Mohorovičić taught meteorology at the Nautical School in Bakar (1882-1891) and later at the University of Zagreb (since 1894). As for the professional engagement in meteorology, his major achievements were foundation of me- teorological station in Bakar (1887), start of meteorological forecasting in Croatia (1893), and establishment of the network of Croatian meteorological stations (1901). Mohorovičić's meteorological research included, but was not limited to, the climatological investigation of clouds and their movements in the Bakar area, the study of tornado that struck Novska, and an early study of the Zagreb climate conditions. As demonstrated in a recent publication, Mohorovičić also made pioneering contribution to the investigation of atmo- spheric rotors, by describing in some detail a vortex with horizontal axis he had observed from Bakar (1889); this discovery influenced later research of similar phenomena in England and Germany, but was forgotten by the inter- national scientific community some fifty years later."
"23027746100;55739684700;","The peatland/ice age hypothesis revised, adding a possible glacial pulse trigger",2007,"10.1111/j.1468-0459.2007.00328.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36749057402&doi=10.1111%2fj.1468-0459.2007.00328.x&partnerID=40&md5=296691a7ece26cfac16f9be69ff1423a","Carbon sequestering in peatlands is believed to be a major climate-regulating mechanism throughout the late Phanerozoic. Since plant life first evolved on land, peatlands have been significant carbon sinks, which could explain significant parts of the large variations in atmospheric carbon dioxide observed in various records. The result is peat in different degrees of metamorphosis, i.e. lignite, hard coal and graphite. During phases of extensive glaciations such as the 330-240 Ma Pangea Ice Age, atmospheric carbon dioxide was critically low. This pattern repeats itself during the Pleistocene when carbon dioxide oscillates with an amplitude of c. 200-300 ppmv. This paper suggests that the ice age cycles during the Pleistocene are generated by the interglacial growth of peatlands and the subsequent sequestering of carbon into this terrestrial pool. The final initiation of ice age pulses towards the end of inter-glacials, on the other hand, is attributed to the cyclic influx of cosmic dust to the Earth surface, which in turn regulates cloud formation and the incoming shortwave radiation. These shorter cycles have a frequency of c. 1000-1250 years and might be connected to sunspot or other low frequency solar variations. In a wider context the ice age cycling could be regarded as an interplay between terrestrial life on the high latitudes of the northern hemisphere and the marine subsurface life in the southeast. If the results presented here are correct, the present global warming might just be the early part of a new warm period such as the Bronze Age and the Roman and Medieval Warm periods. This could be caused by entry into another phase of decreasing influx rates of cosmic dust. The increasing concentrations of atmospheric carbon dioxide might have contributed to this warming but, most important of all, it might temporarily have saved us from a new ice age pulse. © 2007 Swedish Society for Anthropology and Geography."
"56139541600;6701358470;7202163945;7103246957;","Relationships between land surface and near-surface atmospheric variables in the NCEP North American Regional Reanalysis",2007,"10.1175/2007JHM844.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38749119028&doi=10.1175%2f2007JHM844.1&partnerID=40&md5=6dcc230517abf61963973aaeba8e592c","This study examines the recently released National Centers for Environmental Prediction (NCEP) North American Regional Reanalysis (NARR) products over diverse climate regimes to determine the regional relationships between soil moisture and near-surface atmospheric variables. NARR assimilates observed precipitation, as well as near-surface observations of humidity and wind, while seeking a balance of the surface water and energy budgets with a modern land surface model. The results of this study indicate that for most basins (of approximate size of 0.5-1.0 × 106 km2) the NARR surface water budgets have relatively small residuals (about 0.2 mm day-1), and slightly larger residuals (about 0.4 mm day-1) for basins with complex terrain like those in the western United States. Given that the NARR is an assimilation system (especially one that assimilates observed precipitation), the NARR does not include feedbacks between soil moisture and precipitation. Nonetheless, as a diagnostic tool anchored to observations, the NARR does show that the extent of positive correlation between anomalies of soil moisture and anomalies of precipitation in a given region depends on that region's dryness. The existence of correlations among all variables is a necessary - but not sufficient - condition for land-atmosphere feedbacks to exist, as a region with no correlations would not be expected to have feedbacks. Likewise, a high degree of persistence of soil moisture anomalies in a given basin does not by itself guarantee a positive correlation between anomalies of soil moisture and precipitation. Land surface-atmosphere relationships at monthly time scales are identified by examining the associations between soil moisture and surface and boundary layer variables. Low soil moisture is consistently associated with increased net shortwave radiation and increased outgoing longwave radiation through the effects of less cloud cover and lower atmospheric humidity. No systematic association is revealed between soil moisture and total net surface radiation, as this relation varies substantially between different basins. Low soil moisture is positively correlated with increased sensible heat and lower latent heat (reflected in a smaller evaporative fraction), decreased low-cloud cover, and higher lifting condensation level. The relation between soil moisture anomalies and precipitation anomalies is found to be quite variable between the basins, depending on whether availability of surface water exceeds the available energy for evaporation, or vice versa. Wetter basins, like the Columbia and Ohio, display weak or no correlations between soil moisture anomalies and precipitation anomalies. On the other hand, transitional regions between wet and dry regions, like the central Great Plains, manifest a positive correlation between soil moisture anomalies and precipitation anomalies. These results further the understanding of previous predictability studies (in coupled land-atmosphere prediction models), which indicates that in order for precipitation anomalies to emerge in response to soil moisture anomalies in a given region, it is necessary that the region's seasonal climate be neither too dry nor too wet. © 2007 American Meteorological Society."
"7501488862;7102127179;7006738324;26643408200;","Development of the HIRS outgoing longwave radiation climate dataset",2007,"10.1175/2007JTECHA989.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38549181922&doi=10.1175%2f2007JTECHA989.1&partnerID=40&md5=9d642a9badbf64b8040d7c7ca594d4d1","The Advanced Very High Resolution Radiometer (AVHRR) outgoing longwave radiation (OLR) product, which NOAA has been operationally generating since 1979, is a very long data record that has been used in many applications, yet past studies have shown its limitations and several algorithm-related deficiencies. Ellingson et al. have developed the multispectral algorithm that largely improved the accuracy of the narrowband-estimated OLR as well as eliminated the problems in AVHRR. NOAA has been generating High Resolution Infrared Radiation Sounder (HIRS) OLR operationally since September 1998. In recognition of the need for a continuous and long OLR data record that would be consistent with the earth radiation budget broadband measurements in the National Polar-orbiting Operational Environmental Satellite System (NPOESS) era, and to provide a climate data record for global change studies, a vigorous reprocessing of the HIRS radiance for OLR derivation is necessary. This paper describes the development of the new HIRS OLR climate dataset. The HIRS level 1b data from the entire Television and Infrared Observation Satellite N-series (TIROS-N) satellites have been assembled. A new radiance calibration procedure was applied to obtain more accurate and consistent HIRS radiance measurements. The regression coefficients of the HIRS OLR algorithm for all satellites were rederived from calculations using an improved radiative transfer model. Intersatellite calibrations were performed to remove possible discontinuity in the HIRS OLR product from different satellites. A set of global monthly diurnal models was constructed consistent with the HIRS OLR retrievals to reduce the temporal sampling errors and to alleviate an orbital-drift-induced artificial trend. These steps significantly improved the accuracy, continuity, and uniformity of the HIRS monthly mean OLR time series. As a result, the HIRS OLR shows a comparable stability as in the Earth Radiation Budget Satellite (ERBS) nonscanner OLR measurements. HIRS OLR has superb agreement with the broadband observations from Earth Radiation Budget Experiment (ERBE) and Clouds and the Earth's Radiant Energy System (CERES) in the ENSO-monitoring regions. It shows compatible ENSO-monitoring capability with the AVHRR OLR. Globally, HIRS OLR agrees with CERES with an accuracy to within 2 W m-2 and a precision of about 4 W m-2. The correlation coefficient between HIRS and CERES global monthly mean is 0.997. Regionally, HIRS OLR agrees with CERES to within 3 W m-2 with precisions better than 3 W m-2 in most places. HIRS OLR could be used for constructing climatology for applications that plan to use NPOESS ERBS and previously used AVHRR OLR observations. The HIRS monthly mean OLR data have high accuracy and precision with respect to the broadband observations of ERBE and CERES. It can be used as an independent validation data source. The uniformity and continuity of HIRS OLR time series suggest that it could be used as at reliable transfer reference for the discontinuous broadband measurements from ERBE, CERES, and ERBS. © 2007 American Meteorological Society."
"7003668116;6701606453;7005135473;","Evaluating specific error characteristics of microwave-derived cloud liquid water products",2007,"10.1029/2007GL031180","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38949160765&doi=10.1029%2f2007GL031180&partnerID=40&md5=57112f7b85d201152576580adb5c52d0","Methods are presented for assessing minimum errors and cloud inhomogeneity effects in cloud liquid water path (LWP) products derived from passive microwave satellite measurements. Using coincident visible/ infrared satellite data, errors are isolated by identifying certain cloud conditions within the microwave sensor's field of view. Analysis of 3 weeks of global pixel-level LWP data revealed that 70% of the systematic errors occurred between -0.011 and +0.025 kgm-2, with the mean random error being 0.013 kgm-2. For overcast clouds these systematic errors translate to a mean lower-bound relative error of about +23%. A significant correlation of these products with near-surface wind speed was also shown. The LWP products were found to depend on cloud fraction as well, suggesting the influence of beam filling errors. This approach shows promise in characterizing the minimum errors in LWP products needed for climate and remote sensing studies as well as future data assimilation applications. Copyright 2007 by the American Geophysical Union."
"8962699100;7202954964;7007021059;7401945370;","Climatology of a nonhydrostatic global model with explicit cloud processes",2007,"10.1029/2007GL031048","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38949138080&doi=10.1029%2f2007GL031048&partnerID=40&md5=8accfb5bb4515d4472f6a613c43f86c1","This is the first study to obtain a statistical climate state under a perpetual July condition using a nonhydrostatic global model with explicit cloud processes. Horizontal grid intervals of approximately 7 and 14 km over the globe marginally allowed for a general representation of mesoscale circulations associated with deep clouds. The fine-scale precipitation distribution was similar to satellite observations, particularly in regions of the Intertropical Convergence Zone. Realistic distributions of cloud cover in upper, middle, and lower levels were also obtained, although the geographic locations of lower clouds differed slightly from observations over the eastern Pacific. Sensitivity experiments revealed a decrease in outgoing longwave radiation (OLR) as ice fall speed increased or as mixing in the boundary layer was enhanced. As the horizontal resolution increased, the cloud fraction increased and both the OLR and the total water path decreased, implying that cloud overlap also decreased as the resolution increased. Copyright 2007 by the American Geophysical Union."
"7409080503;57218665240;8839875600;23470280500;7005399437;22236001900;57138743300;7101899854;7005793702;7402049961;13310165300;7101638253;","Aerosol optical properties and their radiative effects in northern China",2007,"10.1029/2006JD007382","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38149052692&doi=10.1029%2f2006JD007382&partnerID=40&md5=17f7e0c08cee38d3a583d314f0c4d719","As a fast developing country covering a large territory, China is experiencing rapid environmental changes. High concentrations of aerosols with diverse properties are emitted in the region, providing a unique opportunity for understanding the impact of environmental changes on climate. Until very recently, few observational studies were conducted in the source regions. The East Asian Study of Tropospheric Aerosols: An International Regional Experiment (EAST-AIRE) attempts to characterize the physical, optical and chemical properties of the aerosols and their effects on climate over China. This study presents some preliminary results using continuous high-quality measurements of aerosol, cloud and radiative quantities made at the first EAST-AIRE baseline station at Xianghe, about 70 km east of Beijing over a period of one year (September 2004 to September 2005). It was found that the region is often covered by a thick layer of haze (with a yearly mean aerosol optical depth equal to 0.82 at 500 run and maximum greater than 4) due primarily to anthropogenic emissions. An abrupt ""cleanup"" of the haze often took place in a matter of one day or less because of the passage of cold fronts. The mean single scattering albedo is approximately 0.9 but has strong day-to-day variations with maximum monthly averages occurring during the summer. Large aerosol loading and strong absorption lead to a very large aerosol radiative effect at the surface (the annual 24-hour mean values equals 24 W m-2), but a much smaller aerosol radiative effect at the top of the atmosphere (one tenth of the surface value). The boundary atmosphere is thus heated dramatically during the daytime, which may affect atmospheric stability and cloud formation. In comparison, the cloud radiative effect at the surface is only moderately higher (-41 W m-2) than the aerosol radiative effect at the surface. Copyright 2007 by the American Geophysical Union."
"57212704708;13403030300;7005773698;","Analysis of rainwater samples: Comparison of single particle residues with ambient particle chemistry from the northeast Pacific and Indian oceans",2007,"10.1029/2006JD008269","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38349084749&doi=10.1029%2f2006JD008269&partnerID=40&md5=d9cc7b238ec0333aa58e152d695fd7be","Individual particles produced from atomized rainwater samples collected in California and the Indian Ocean were analyzed with an aerosol time-of-flight mass spectrometer (ATOFMS) to investigate the chemical composition of the individual rain residue particles. Insoluble residue particle types were determined on the basis of a comparison of the rainwater particle mass spectra with ambient particle spectra. Major particle types found in rainwater include dust, organic carbon with sodium, aromatic organic carbon, vegetative detritus, and an internally mixed sea salt and elemental carbon class. A unique internally mixed sea salt-elemental carbon particle type was detected in both the ambient and rainwater samples, suggesting this particle type was most likely formed by cloud processing occurring during long-range transport. The presence of this particle type in remote marine locations has important climate ramifications as it is anticipated it will be strongly absorbing on the basis of the combination of an absorbing particle (elemental carbon) mixed with a high refractive index material (sea salt). Most of the particle types detected in rainwater were detected in the ambient particles with the exception of a unique aromatic particle type detected in rainwater samples from both locations. The presence of the aromatic type coupled with the absence of biomass particles in the rainwater samples leads to the hypothesis the aromatic components were originally associated with atmospheric biomass burning particles. The ubiquitous presence of this aromatic type in rainwater samples highlights the potential importance of biomass burning and/or humic-like substances (HULIS) compounds in cloud formation and rain processes. Copyright 2007 by the American Geophysical Union."
"35291021400;6602286409;7006383649;7801595201;7005858285;13406672500;","Understanding the origin of black carbon in the atmospheric brown cloud over the Indian Ocean",2007,"10.1029/2006JD008118","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38349137439&doi=10.1029%2f2006JD008118&partnerID=40&md5=49c5124667f85cee1e503ea5822c2c1e","Atmospheric particulate matter samples were collected at two Maldives climate observatories from 30 August 2004 to 21 January 2005. This time period encompassed both wet and dry seasons, which correspond to low and high aerosol loadings. High aerosol loadings were observed in the northern sampling site in Hanimaadhoo, caused by long-range transport from south and Southeast Asia, whereas the southern sampling site, Gan, was not subject to as much continental inflow. The polluted period began in mid-November and lasted through the remainder of the sampling period. Fine particulate matter during this time was characterized by relatively high concentrations of aerosol mass and elemental carbon. Concentrations of water-soluble potassium, sulfate, levoglucosan, polyaromatic hydrocarbons, aliphatic diacids, aromatic diacids, and trace metals increased over the clean, transition, and polluted dry season. Organic speciation suggested that significant secondary organic aerosol formation occurred during the polluted dry season, meaning that traditional methods of source identification relying on fixed elemental and organic carbon ratios between source and receptors are not sufficient. Well-studied molecular markers for combustion sources were not adequate in fully attributing elemental carbon over the northern Indian Ocean to specific sources. Further source profiling of south and Southeast Asian biofuels and fossil fuels is recommended. A receptor-based positive matrix factorization model was applied to fine particulate matter trace metal measurements and showed that biofuel burning and fossil fuel combustion were equally important sources of elemental carbon during the polluted dry season. Copyright 2007 by the American Geophysical Union."
"36892703600;7102294773;7404592426;7202048112;55802246600;7006383649;35291021400;13406672500;57196817178;","Characterization of the seasonal cycle of south Asian aerosols: A regional-scale modeling analysis",2007,"10.1029/2006JD008143","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38349118365&doi=10.1029%2f2006JD008143&partnerID=40&md5=ca63a58d18b7f2a9f91692aefc08cadf","The sulfur transport and deposition model (STEM) is used to study the aerosol seasonality, distribution, and composition over south Asia from September 2004 to August 2005. Model predictions of sulfate, black carbon, primary organic carbon, other anthropogenic particulate matter, windblown mineral dusts, and sea salt are compared at two sites in south Asia where yearlong experimental observations are available from the Atmospheric Brown Cloud (ABC) project. The model predictions are able to capture both the magnitude and seasonality of aerosols over Hanimaadhoo Observatory, Maldives. However, the model is not able to explain the seasonality at the Kathmandu Observatory; but the model does capture Kathmandu's observed annual mean concentration. The absence of seasonal brick kiln emissions within Kathmandu valley in the current inventory is a probable reason for this problem. This model study reveals high-anthropogenic aerosol loading over the Ganges valley even in the monsoonal months, which needs to be corroborated by experimental observations. Modeling results also show a high dust loading over south Asia with a distinct seasonality. Model results of aerosol monthly composition are also presented at five cities in south Asia. Total and fine-mode monthly aerosol optical depth along with contribution from each aerosol species is presented; the results show that the anthropogenic fraction dominates in the postmonsoon and the early dry season with major contributions from sulfate and absorbing aerosols. Model sensitivity studies of dry deposition velocity and wet scavenging efficiency show that model improvements are needed in the treatment of carbonaceous aerosol dry and wet removal processes. Modeled SO<inf>2</inf> conversion rate constrained with sulfate observations at Hanimaadhoo suggests the need to increase model sulfate production rate during the dry season to account for probable sulfate production via heterogeneous pathways. Copyright 2007 by the American Geophysical Union."
"7003830856;","Pollution and the Planetary Albedo",2007,"10.1016/j.atmosenv.2007.10.062","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36249026321&doi=10.1016%2fj.atmosenv.2007.10.062&partnerID=40&md5=8f09f1b680edd5c7bc662dd50a5f8c4d","Addition of cloud nuclei by pollution can lead to an increase in the solar radiation reflected by clouds. The reflection of solar energy by clouds already may have been increased by the addition of man-made cloud nuclei. The albedo of a cloud is proportional to optical thickness for thin clouds, but changes more slowly with increasing thickness. The optical thickness is increased when the number of cloud nuclei is increased. Although the changes are small, the long-term effect on climate can be profound. © 2007 Elsevier Ltd. All rights reserved."
"36021770100;55359062800;7005256762;36916954400;","ENSO and convective activities in Southeast Asia and western Pacific",2007,"10.1029/2007GL030758","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38549162244&doi=10.1029%2f2007GL030758&partnerID=40&md5=2700a0988da9aac37b8cbe3cfc9e6260","The remarkable contrasts between El Niño and La Niña in the East/Southeast Asia region and the western Pacific region are reported. One is that the lightning flash rate in the East/Southeast Asia region shows a clear inverse correlation with the Southern Oscillation Index (SOI). The lightning activity increases during the El Niño period and decrease during the La Niña period in this area. The other is that the contrast of the areal distribution of the variation of the flash rate in the western Pacific region. During the El Niño period the moist air from the ocean is warmed over the land, and that makes strong updrafts in high-pressure systems over the oceanic area. As a result, well-developed cumulonimbus with frequent lightning activity is observed in the coastal area. During the La Niña period, low-pressure systems on the land cause the increase of rainfall frequency with less lightning activity. Copyright 2007 by the American Geophysical Union."
"23003611300;7004415966;7003922583;","Intercomparison of global cloud cover fields over oceans from the VOS observations and NCEP/NCAR reanalysis",2007,"10.1002/joc.1490","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36248948587&doi=10.1002%2fjoc.1490&partnerID=40&md5=e4ca9a7a0dddf6d057b34762443db495","The paper inter-compares the total cloud cover over the World Ocean from marine visual observations assimilated in the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) and National Centers of Environmental Prediction/National Center of Atmospheric Research (NCEP-NCAR) reanalysis. The Intercomparison covers the period from 1948 to 2002. NCEP-NCAR reanalysis shows about 10% of fractional cloud cover smaller than the visual observations do. The largest differences are observed in the mid and sub-polar latitudes. In the tropics, NCEP-NCAR data show slightly higher cloud cover then ICOADS. These systematic differences are quite persistent through the year with somewhat stronger differences in summer. Comparison of the characteristics of inter-annual variability shows little consistency between visually observed total cloud cover and total cloudiness diagnosed by the reanalysis. Linear trends are primarily positive in the ICOADS cloud data, while in the NCEP-NCAR reanalysis they show downward trends in the tropics and upward tendencies in the mid and high latitudes. Analysis of the effect of sampling in ICOADS shows that sampling inhomogeneity cannot fully explain the disagreements observed. At the same time, the major climate variability patterns such as North Atlantic Oscillation (NAO) and El-Nino - Southern Oscillation (ENSO) are well captured in both ICOADS and NCEP-NCAR cloud cover data sets. Copyright © 2007 Royal Meteorological Society."
"55087038900;","A new parameterization of an asymmetry factor of cirrus clouds for climate models",2007,"10.1175/2007JAS2289.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37349026177&doi=10.1175%2f2007JAS2289.1&partnerID=40&md5=49cdf4f0dc3ceab0efec906b57f8dfd9","The aspect ratio (AR) of a nonspherical ice particle is identified as the key microphysical parameter to determine its asymmetry factor for solar radiation. The mean effective AR is defined for cirrus clouds containing various nonspherical ice particles. A new parameterization of the asymmetry factor of cirrus clouds in terms of AR and mean effective size, Dgσ is developed for solar radiation. It is based on geometric ray-tracing calculations for hexagonal ice crystals with a simple representation of particle surface roughness. The present parameterization well reproduces the asymmetry factors of complicated ice particles such as bullet rosettes, aggregates with rough surfaces, and fractal crystals and agrees well with observations. It thus can be properly applied to cirrus clouds containing various nonspherical ice particles. The asymmetry factor from this parameterization in the visible spectrum ranges from about 0.73 to more than 0.85. Radiative transfer calculations show that for a cirrus cloud with an optical depth of 4 and a solar zenith angle of 60°, changes in AR from 1.0 to 0.5 or from 1.0 to 0.1 result in differences in reflected solar fluxes of about -30 or - 70 W m-2, respectively. For the same cloudy conditions, the effect of ice particle surface roughness on the reflected solar flux is found to be about 20 W m-2. © 2007 American Meteorological Society."
"6505561064;7006184606;","The dynamic response of the winter stratosphere to an equable climate surface temperature gradient",2007,"10.1175/2007JCLI1556.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36348942347&doi=10.1175%2f2007JCLI1556.1&partnerID=40&md5=0c02c143f6f1d235cef0082af7ee4713","This work investigates the dynamic and thermal response of the winter stratosphere to the presence of a weak meridional surface temperature gradient. Previous work suggested that polar stratospheric clouds could have played a decisive role in maintaining high-latitude warmth, especially over continental interiors, during the polar nights of the late Paleocene and early Eocene epochs; both a chemical source of additional water vapor and a dynamical feedback between the surface climate and stratospheric temperatures have been proposed as mechanisms by which such clouds could form. A principal goal of this work is to investigate the latter problem using a general circulation model with stratospheric resolution that is forced with a very weak surface temperature gradient. It is found that temperatures in the lower stratosphere do not deviate significantly from the control run, which results from a robust flux of wave activity into the winter stratosphere. The strength of the stratosphere's residual circulation increases slightly in the presence of the weak gradient, as wavenumber 3 begins to propagate to stratospheric altitudes. Changes in the zonal wind field that allow for the altered propagation are in balance with a weakened temperature gradient through the full depth of the troposphere. These simulations also suggest that the tropospheric thermal stratification could be maintained by moist convection at all latitudes in warm climate states with a weak temperature gradient. © 2007 American Meteorological Society."
"7003875148;","Is there a diurnal cycle in the summer cloud-capped Arctic boundary layer?",2007,"10.1175/2007JAS2257.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37349132306&doi=10.1175%2f2007JAS2257.1&partnerID=40&md5=dcc8e673e74da07311b47742b69f3d98","Data from the Arctic Ocean Experiment 2001 (AOE-2001) are used to study the vertical structure and diurnal cycle of the summertime central Arctic cloud-capped boundary layer. Mean conditions show a shallow stratocumulus-capped boundary layer, with a nearly moist neutrally stratified cloud layer, although cloud tops often penetrated into the stable inversion. The subcloud layer was more often stably stratified. Conditions near the surface were relatively steady, with a strong control on temperature and moisture by the melting ice surface. A statistically significant diurnal cycle was found in many parameters, although weak in near-surface temperature and moisture. Near-surface wind speed and direction and friction velocity had a pronounced cycle, while turbulent kinetic energy showed no significant diurnal variability. The cloud layer had the most pronounced diurnal variability, with lowest cloud-base height midday followed by enhanced drizzle and temporarily higher cloud-top heights in the afternoon. This is opposite to the cycle found in midlatitude or subtropical marine stratocumulus. The cloud layer was warmest (coolest) and more (less) stably stratified midafternoon (midmorning), coinciding with the coolest (warmest) but least (most) stably stratified capping inversion layer. It is speculated that drizzle is important in regulating the diurnal variability in the cloud layer, facilitated by enhanced midday mixing due to a differential diurnal variability in cloud and subcloud layer stability. Changing the Arctic aerosol climate could change these clouds to a more typical ""marine stratocumulus structure,"" which could act as a negative feedback on Arctic warming. © 2007 American Meteorological Society."
"6701850538;35584010200;24722339600;7004479957;","The three-dimensional structure and kinematics of drizzling stratocumulus",2007,"10.1175/2007MWR1944.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36749086439&doi=10.1175%2f2007MWR1944.1&partnerID=40&md5=769e7ddf797399facbbef6676040d2aa","Drizzling marine stratocumulus are examined using observations from the 2001 East Pacific Investigation of Climate Stratocumulus (EPIC Sc) field experiment. This study uses a unique combination of satellite and shipborne Doppler radar data including both horizontal and vertical cross sections through drizzle cells. Stratocumulus cloud structure was classified as closed cellular, open cellular, or unclassifiable using infrared satellite images. Distributions of drizzle cell structure, size, and intensity are similar among the cloud-structure categories, though the open-cellular distributions are shifted toward higher values. Stronger and larger drizzle cells preferentially occur when the cloud field is broken (open-cellular and unclassifiable categories). Satellite observations of cloud structure may be useful to indicate the most likely distribution of rain rates associated with a set of scenes, but infrared data alone are not sufficient to develop routine precipitation retrievals for marine stratocumulus. Individual drizzle cells about 2-20 km across usually showed precipitation growth within the cloud layer and evaporation below, divergence near echo top, and convergence below cloud base. Diverging flow near the surface was also observed beneath heavily precipitating drizzle cells. As the cloud field transitioned from a closed to an open-cellular cloud structure, shipborne radar revealed prolific development of small drizzle cells (&lt;10 km2) that exceeded by over 5 times the number of total cells in either the preceding closed-cellular or following open-cellular periods. Peak area-average rain rates lagged by a few hours the peak in total number of drizzle cells. Based on observations from EPIC Sc, the highest stratocumulus rain rates are more likely to occur near the boundary between closed and open-cellular cloud structures. © 2007 American Meteorological Society."
"6507679962;7004160585;6701574871;6701751100;7004854393;","An approach for convective parameterization with memory: Separating microphysics and transport in grid-scale equations",2007,"10.1175/2007JAS2144.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249992181&doi=10.1175%2f2007JAS2144.1&partnerID=40&md5=a1584b14fa65dc92ff1776d0d7ae5dc8","An approach for convective parameterization is presented here, in which grid-scale budget equations of parameterization use separate microphysics and transport terms. This separation is used both as a way to introduce into the parameterization a more explicit causal link between all involved processes and as a vehicle for an easier representation of the memory of convective cells. The equations of parameterization become closer to those of convection-resolving models [cloud-system-resolving models (CSRMs) and large-eddy simulations (LESs)], facilitating parameterization development and validation processes versus a detailed budget of these high-resolution models. The new Microphysics and Transport Convective Scheme (MTCS) equations are presented and discussed. A first version of a convective scheme based on these equations is tested within a single-column framework. The results obtained with the new scheme are close to those of traditional ones in very moist convective cases (like the Global Atmospheric Research Programme (GARP) Atlantic Tropical Experiment (GATE) Phase III, 1974]. The simulation of more difficult drier situations [European Cloud Systems Study/Global Energy and Water Cycle Experiment (GEWEX) Cloud System Studies (EUROCS/GCSS)] is improved through more memory due to higher sensitivity of simulated convection to dry midtropospheric layers; a prognostic relation between cloudy entrainment and precipitation evaporation dramatically improves the prediction of the phase lag of the convective diurnal cycle over land with respect to surface heat forcing. The present proposal contains both a relatively general equation set, which can deal continuously with dry, moist, and deep precipitating convection, and separate - and still crude - explicit moist microphysics. In the future, when increasing the complexity of microphysical computations, such an approach may help to unify dry, moist, and deep precipitating convection inside a single parameterization, as well as facilitate global climate model (GCM) and limited-area model (LAM) parameterizations in sharing the same formulation of explicit microphysics with CSRMs. © 2007 American Meteorological Society."
"22980987200;55915387400;7006592026;","Increase in summer European ozone amounts due to climate change",2007,"10.1016/j.atmosenv.2007.05.048","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36049008092&doi=10.1016%2fj.atmosenv.2007.05.048&partnerID=40&md5=b260d8a27415ca92c419d34b29656de7","The local and regional distribution of pollutants is significantly influenced by weather patterns and variability along with the spatial patterns of emissions. Therefore, climatic changes which affect local meteorological conditions can alter air quality. We use the regional air quality model CHIMERE driven by meteorological fields from regional climate change simulations to investigate changes in summer ozone mixing ratios over Europe under increased greenhouse gas (GHG) forcing. Using three 30-year simulation periods, we find that daily peak ozone amounts as well as average ozone concentrations substantially increase during summer in future climate conditions. This is mostly due to higher temperatures and reduced cloudiness and precipitation over Europe and it leads to a higher number of ozone events exceeding information and warning thresholds. Our results show a pronounced regional variability, with the largest effects of climate change on ozone concentrations occurring over England, Belgium, Germany and France. The temperature-driven increase in biogenic emissions appears to enhance the ozone production and isoprene was identified as the most important chemical factor in the ozone sensitivity. We also find that summer ozone levels in future climate projections are similar to those found during the exceptionally warm and dry European summer of 2003. Our simulations suggest that in future climate conditions summer ozone might pose a much more serious threat to human health, agriculture and natural ecosystems in Europe, so that the effects of climate trends on pollutant amounts should be considered in future emission control measures. © 2007 Elsevier Ltd. All rights reserved."
"57215549801;6602667330;7202972418;","Time series of daily averaged cloud fractions over landfast first-year sea ice from multiple data sources",2007,"10.1175/2007JAMC1472.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38049174354&doi=10.1175%2f2007JAMC1472.1&partnerID=40&md5=c0d25818050f78fba39880453ebd8d73","The time series of daily averaged cloud fractions (CFs) collected from different platforms - two Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on Terra and Aqua satellites, the National Centers for Environmental Prediction (NCEP) model, a Vaisala 25K laser ceilometer, and ground-based manual observations (manobs) - above the winter camp of the Canadian Arctic Shelf Exchange Study (CASES) field experiment are analyzed in this study. Taking the manobs as standard, the authors conclude that 1) the NCEP products considerably underestimated CFs in spring (e.g., from April to May) and 2) the performance of two MODIS products depends on the variation of solar zenith angle (SZA). Aqua MODIS misrepresents the snow-covered surface as clouds with almost randomly distributed CFs during the dark winter [cos(SZA) < 0], leading to the overestimation of CFs in winter while Terra MODIS has good agreement with manobs. When 0.1 < cos(SZA) < 0.4, both MODIS products regularly misrepresent the snow-covered background as clouds, leading to the significant overestimation of CFs in late winter (February) and early spring (March). When cos(SZA) > 0.4, both MODIS products have good performance in detecting cloud masks over snow backgrounds. If the sky is slightly cloudy, surface-based meteorological observers tend to underestimate cloud amounts when there is a lack of light. Comparing the CFs from Terra and manobs, the authors conclude that this bias can be over 10%. Power spectral analysis and wavelet analysis show three results: 1) High clouds more frequently appear in winter than in spring with periods between 8 and 16 days, indicating their close connection with synoptic events. Current NCEP products can predict this periodicity but have a phase lag. 2) Middle and low clouds are more local and are common in mid- and late spring (April and May) with periods between 2 and 4 days. At the CASES winter and spring field site, the periodicity of high clouds is dominant. 3) The time-scale-dependent correlation coefficients (CCs) between both MODIS products, NCEP and manobs, show that with high frequent CF sampling per day, the CCs are stable when the time scale varies between 1 and 4 days: with Terra MODIS and NCEP, the value is about 0.6; with Aqua MODIS, between 0.4 and 0.5. All CCs get smaller when the time scale increases beyond 8 days: with respect to both MODIS products, the CCs get closer with values between 0.3 and 0.4; with respect to NCEP, the CC dramatically decreases from positive values to negative values, indicating the lack of accuracy in current NCEP cloud schemes. © 2007 American Meteorological Society."
"56036694200;7007067997;7004346367;7003398293;","Trends in aerosol optical depth for cities in India",2007,"10.1016/j.atmosenv.2007.05.055","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35748957125&doi=10.1016%2fj.atmosenv.2007.05.055&partnerID=40&md5=5de3c8cd588d86dfaecbd55230f6462e","Recent analysis of trends in global short-wave radiation measured with pyranometers in major cities in India support a decrease in solar radiation in many of those cities since 1990. Since direct and diffuse radiation measurements include cloud effects, spring and summer dust and the variable summer monsoon rains, we concentrate in this paper on wintertime (November-February) aerosol optical depth measurements. The aerosol optical depth is derived from cloud-free turbidity measurements beginning in the 1960s and more recent sun photometer direct aerosol optical depth measurements. We compare the sun photometer derived trends with the pyranometer-derived trends using a radiative transfer model. These results are then compared to total ozone mapping spectrometer (TOMS) satellite-derived regional aerosol optical depths from 1980 to 2000. The results show that inclusion of the earlier turbidity measurements helps to establish an increasing regional turbidity trend. However, most of the increasing trend is confined to the larger cities in the Ganges River Basin of India (mainly Calcutta and New Delhi) with other cities showing a much less increase. Regional satellite data show that there is an increasing trend in aerosol off the coast of India and over the Ganges River Basin. The increase over the Ganges River Basin is consistent with population trends over the region during 1980-2000. © 2007 Elsevier Ltd. All rights reserved."
"24436549800;6701389719;55724852700;57218315286;","Impacts of absorbing aerosols on South Asian rainfall: A modeling study",2007,"10.1007/s10584-006-9184-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35148866738&doi=10.1007%2fs10584-006-9184-5&partnerID=40&md5=9f8cacb389628a09265cef40a3e41b05","Anthropogenic aerosols in the lower troposphere increase the absorption and scattering of solar radiation by air and clouds, causing a warmer atmosphere and a cooler surface. It is suspected that these effects contribute to slow down the hydrological cycle. We conducted a series of numerical experiments using a limited area atmospheric model to understand the impacts of aerosol radiative forcing on the rainfall process. Experiments with different radiative conditions under an idealized setting revealed that increasing atmospheric forcing and decreasing surface forcing of radiation causes reductions in rainfall. There was no relationship of top of the atmosphere forcing to the rainfall yield. The model was then used to simulate a domain covering southern part of Sri Lanka, over for the period from November 2002 to July 2003. For a given radiative forcing, instances with lower rainfall yields showed larger fractional reductions in rainfall. The trends in seasonal rainfall observed over the site in past 30 years in a different study confirms this finding. We conclude that the negative impact of increase of anthropogenic aerosols on rainfall would be more severe on regions and seasons with lower rainfall yields. The consequences of this problem on the industries that critically depend on well-distributed rainfall like non-irrigated agriculture and on the general livelihood of societies in low-rain areas can be serious. © 2006 Springer Science+Business Media, Inc."
"8612873400;7102866124;8612872900;6603274559;","Intercomparison of integrated water vapor estimates from multisensors in the Amazonian region",2007,"10.1175/JTECH2090.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36749076016&doi=10.1175%2fJTECH2090.1&partnerID=40&md5=4f860233fa16095f12562ec9bb69394d","Water vapor is an atmospheric component of major interest in atmospheric science because it affects the energy budget and plays a key role in several atmospheric processes. The Amazonian region is one of the most humid on the planet, and land use change is able to affect the hydrologic cycle in several areas and consequently to generate severe modifications in the global climate. Within this context, accessing the error associated with atmospheric humidity measurement and the validation of the integrated water vapor (IWV) quantification from different techniques is very important in this region. Using data collected during the Radiation, Cloud, and Climate Interactions in Amazonia during the Dry-to-Wet Transition Season (RACCI/DRY-TO-WET), an experiment carried out in southwestern Amazonia in 2002, this paper presents quality analysis of IWV measurements from RS80 radiosondes, a suite of GPS receivers, an Aerosol Robotic Network (AERONET) solar radiometer, and humidity sounding from the Humidity Sounder for Brazil (HSB) aboard the Aqua satellite. When compared to RS80 IWV values, the root-mean-square (RMS) from the AERONET and GPS results are of the order of 2.7 and 3.8 kg m-2, respectively. The difference generated between IWV from the GPS receiver and RS80 during the daytime was larger than that of the nighttime period because of the combination of the influence of high ionospheric activity during the RACCI experiment and a daytime drier bias from the RS80. © 2007 American Meteorological Society."
"9244954000;6701549604;7004201807;","The IMPROVE-1 storm of 1-2 February 2001. Part III: Sensitivity of a mesoscale model simulation to the representation of snow particle types and testing of a bulk microphysical scheme with snow habit prediction",2007,"10.1175/2007JAS2239.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37348998885&doi=10.1175%2f2007JAS2239.1&partnerID=40&md5=9c69f8e7f34134992e1a2901e7436d00","A mesoscale model simulation of a wide cold-frontal rainband observed in the Pacific Northwest during the Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-1) field study was used to test the sensitivity of the model-produced precipitation to varied representations of snow particles in a bulk microphysical scheme. Tests of sensitivity to snow habit type, by using empirical relationships for mass and velocity versus diameter, demonstrated the defectiveness of the conventional assumption of snow particles as constant density spheres. More realistic empirical mass-diameter relationships result in increased numbers of particles and shift the snow size distribution toward larger particles, leading to increased depositional growth of snow and decreased cloud water production. Use of realistic empirical mass-diameter relationships generally increased precipitation at the surface as the rainband interacted with the orography, with more limited increases occurring offshore. Changes in both the mass-diameter and velocity-diameter relationships significantly redistributed precipitation either windward or leeward when the rainband interacted with the mountain barrier. A method of predicting snow particle habit in a bulk microphysical scheme, and using predicted habit to dynamically determine snow properties in the scheme, was developed and tested. The scheme performed well at predicting the habits present (or not present) in aircraft observations of the rainband. Use of the scheme resulted in little change in the precipitation rate at the ground for the rainband offshore, but significantly increased precipitation when the rainband interacted with the windward slope of the Olympic Mountains. The study demonstrates the promise of the habit prediction approach to treating snow in bulk microphysical schemes. © 2007 American Meteorological Society."
"7102805852;57205638870;","Causes of the reduction in uncertainty in the anthropogenic radiative forcing of climate between IPCC (2001) and IPCC (2007)",2007,"10.1029/2007GL030749","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37349113351&doi=10.1029%2f2007GL030749&partnerID=40&md5=89da95b3690ba5eb548fd356e27e4382","Mechanisms that drive climate change are quantified by the radiative forcing which is the perturbation to the global energy balance of the Earth/atmosphere system. These mechanisms may be of anthropogenic or natural origins and each has an associated level of scientific uncertainty. Until recently, even the sign of the anthropogenic radiative forcing has been in doubt because strong, poorly quantified negative radiative forcings such as those from aerosols act to oppose the strong, well quantified positive radiative forcings from well mixed greenhouse gases. We present an analysis of the probability distribution function of the anthropogenic radiative forcing for the individual forcing mechanisms identified by IPCC (2001) and IPCC (2007). We conclude that significant progress in reducing the uncertainty of the anthropogenic radiative forcing has been made since IPCC (2001). The single most important contributor to this conclusion appears to be the reduction in the uncertainty associated with the aerosol direct effect, followed by the provision of a best estimate for the aerosol cloud albedo indirect effect. Copyright 2007 by the American Geophysical Union."
"6701481405;57214594557;16643457000;23096202700;6602623905;6603573706;","Atmospheric forcing validation for modeling the central Arctic",2007,"10.1029/2007GL031378","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37349024987&doi=10.1029%2f2007GL031378&partnerID=40&md5=2a0c35f8879c4de9cd53c52609d2fc6f","We compare daily data from the National Center for Atmospheric Research and National Centers for Environmental Prediction ""Reanalysis 1"" project with observational data obtained from the North Pole drifting stations in order to validate the atmospheric forcing data used in coupled ice-ocean models. This analysis is conducted to assess the role of errors associated with model forcing before performing model verifications against observed ocean variables. Our analysis shows an excellent agreement between observed and reanalysis sea level pressures and a relatively good correlation between observed and reanalysis surface winds. The observed temperature is in good agreement with reanalysis data only in winter. Specific air humidity and cloudiness are not reproduced well by reanalysis and are not recommended for model forcing. An example sensitivity study demonstrates that the equilibrium ice thickness obtained using NP forcing is two times thicker than using reanalysis forcing. Copyright 2007 by the American Geophysical Union."
"7201897043;7004210200;","Manifestation of remote response over the equatorial Pacific in a climate model",2007,"10.1029/2007JD008597","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37349026860&doi=10.1029%2f2007JD008597&partnerID=40&md5=60b44e3e8744d8d80497ed7e488069e8","In this paper we examine the simulations over the tropical Pacific Ocean from long-term simulations of two different versions of the Center for Ocean-Land-Atmosphere Studies (COLA) coupled climate model that have a different global distribution of the inversion clouds. We find that subtle changes made to the numerics of an empirical parameterization of the inversion clouds can result in a significant change in the coupled climate of the equatorial Pacific Ocean. In one coupled simulation of this study we enforce a simple linear spatial filtering of the diagnostic inversion clouds to ameliorate its spatial incoherency (as a result of the Gibbs effect) while in the other we conduct no such filtering. It is found from the comparison of these two simulations that changing the distribution of the shallow inversion clouds prevalent in the subsidence region of the subtropical high over the eastern oceans in this manner has a direct bearing on the surface wind stress through surface pressure modifications. The SST in the warm pool region responds to this modulation of the wind stress, thus affecting the convective activity over the warm pool region and also the large-scale Walker and Hadley circulation. The interannual variability of SST in the eastern equatorial Pacific Ocean is also modulated by this change to the inversion clouds. Consequently, this sensitivity has a bearing on the midlatitude height response. The same set of two experiments were conducted with the respective versions of the atmosphere general circulation model uncoupled to the ocean general circulation model but forced with observed SST to demonstrate that this sensitivity of the mean climate of the equatorial Pacific Ocean is unique to the coupled climate model where atmosphere, ocean and land interact. Therefore a strong case is made for adopting coupled ocean-land-attnosphere framework to develop climate models as against the usual practice of developing component models independent of each other. Copyright 2007 by the American Geophysical Union."
"7005861295;23011971900;13805883800;","Telescoping, multimodel approaches to evaluate extreme convective weather under future climates",2007,"10.1029/2006JD008345","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37349070274&doi=10.1029%2f2006JD008345&partnerID=40&md5=f4edfa37fe6a1546a0595c15b43236ee","Understanding of the possible response of severe convective precipitating storms to elevated greenhouse gas concentrations remains elusive. To address this problem, telescoping, multimodel approaches are proposed, which allow representation of a broad range of processes that could regulate convective storm behavior. In the global-cloud approach (G-C), the NCEP-NCAR Reanalysis Project (NNRP) global data set provides initial and boundary conditions for short-term integrations of a mesoscale model and nested convective-cloud-permitting domain. In the global-regional-cloud approach (G-R-C), the NNRP data set provides initial and boundary conditions for long-term integrations of a regional climate model, which in turn forces short-term integrations of a mesoscale model and nested convective-cloud-permitting domain. Upon applying these approaches to historical extreme convective storm events, it was found that the global-scale data could be dynamically downscaled to produce realistic convective-scale solutions. In particular, tornado proxies computed from the model-simulated winds were shown to compare well in relative numbers to those of tornado observations on many of the days considered. This supports the telescoping modeling concept as a viable means to address effects of elevated greenhouse gas concentrations on convective-scale phenomena. In an evaluation of the two approaches, it was also found that simulations of the historical events by the G-C were superior to those by the G-R-C. Sensitivity of the convective-scale processes to details in the downscaled synoptic-scale flow, and to the placement of the mesoscale model domain within the regional climate model, reduced the effectiveness of the G-R-C. Copyright 2007 by the American Geophysical Union."
"55887377500;7003343898;57204295513;7403143411;","Inferences of all-sky solar irradiance using Terra and Aqua MODIS satellite data",2007,"10.1080/01431160701241902","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34748908820&doi=10.1080%2f01431160701241902&partnerID=40&md5=79bb50a76c472e2ef1aa3e20a0ebb1b9","Solar irradiance is a key environmental control, and accurate spatial and temporal solar irradiance data are important for a wide range of applications related to energy and carbon cycling, weather prediction, and climate change. This study presents a satellite-based scheme for the retrieval of all-sky solar irradiance components, which links a physically based clear-sky model with a neural network version of a rigorous radiative transfer model. The scheme exploits the improved cloud characterization and retrieval capabilities of the MODerate resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites, and employs a cloud motion tracking scheme for the production of hourly solar irradiance data throughout the day. The scheme was implemented for the Island of Zealand, Denmark (56°N, 12°E) and Southern Arizona, USA (31°N, 110°W) permitting model evaluation for two highly contrasting climates and cloud environments. Information on the atmospheric state was provided by MODIS data products and verifications against AErosol RObotic NETwork (AERONET) data demonstrated usefulness of MODIS aerosol optical depth and total precipitable water vapour retrievals for the delineation of spatial gradients. However, aerosol retrievals were significantly biased for the semi-arid region, and water-vapour retrievals were characterized by systematic deviations from the measurements. Hourly global solar irradiance data were retrieved with overall root mean square deviations of 11.5% (60 W m-2) and 26.6% (72 W m-2) for Southern Arizona and the Island of Zealand, respectively. For both regions, hourly satellite estimates were shown to be more reliable than pyranometer measurements from ground stations only 15 km away from the point of interest, which is comparable to the accuracy level obtainable from geostationary satellites with image acquisitions every 15-30 min. The proposed scheme is particularly useful for solar irradiance mapping in high-latitude regions as data from geostationary satellites experience a gradual degradation in spatial resolution and overall quality with latitude and become unusable above approximately 60° latitude. However, in principle, the scheme can be applied anywhere on the globe, and a synergistic use of MODIS and geostationary satellite datasets may be envisaged for some applications."
"8922308700;7101909551;7003666669;7006270084;57193213111;","Impact on modeled cloud characteristics due to simplified treatment of uniform cloud condensation nuclei during NEAQS 2004",2007,"10.1029/2007GL030021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37249042269&doi=10.1029%2f2007GL030021&partnerID=40&md5=2b391b4e885d77ec67334b3171ad1d28","Subgrid-scale cloud condensation nuclei (CCN) heterogeneity is not represented in global climate models (GCM) and potentially contributes systematic errors to simulated cloud effects. High-resolution WRF-Chem model simulations were performed to investigate the impact of assuming a uniform CCN distribution on cloud properties and surface radiation over a region the size of a GCM grid column. Results indicate that a prescribed CCN distribution allowing for vertical and temporal fluctuations does substantially better in simulating cloud properties and radiative effects than does a prescribed uniform and constant CCN distribution. Spatially and temporally averaged net effects on downwelling shortwave radiation are between -3 and -11 W m-2 for the fluctuating and uniform distributions, respectively, versus a control simulation with fully interactive aerosols. Both prescribed CCN distributions produce optically thicker clouds more often than the control, with the mean cloud optical depth increasing by over 25% when using the uniform and constant CCN distribution. Copyright 2007 by the American Geophysical Union."
"36449635400;7103098729;","Multiyear satellite observations of the atmospheric response to Atlantic tropical instability waves",2007,"10.1029/2007JD008627","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36849026834&doi=10.1029%2f2007JD008627&partnerID=40&md5=fc90fcff564fb0798d4944186cafaa1f","High-resolution satellite measurements from the Tropical Rainfall Measuring Mission (TRMM), Quick Scatterometer (QuikSCAT), and Special Sensor Microwave Imager (SSM/I) are used to study the variability of sea surface temperature (SST), surface wind velocity, water vapor, cloud liquid water, and precipitation associated with westward moving tropical instability waves (TIWs) in the Atlantic Ocean from 1998 to 2005. Coherent ocean-atmosphere patterns are shown during these 8 years. Southeasterly trades strengthen and water vapor increases over warm SST anomalies associated with TIWs. The opposite is true over cold TIW SST anomalies. The cloud liquid water and rain response to the SSTs follows a similar pattern, appearing generally downstream of SST anomalies in the central tropical Atlantic. The atmospheric response to the TIW SST anomalies extends north of the TIW active region, suggesting a remote response to the TIWs. The atmospheric response to the Atlantic TIWs also exhibits interannual variations. In 1999, owing to the southward movement of the Atlantic Intertropical Convergence Zone (ITCZ), the rainfall response to the TIW SST anomalies is much larger than in other years. When the Atlantic ITCZ moves south, it is more susceptible to TIW influence. Copyright 2007 by the American Geophysical Union."
"7003991987;56431832800;","Using airborne laser scanning to monitor tree migration in the boreal-alpine transition zone",2007,"10.1016/j.rse.2007.03.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548045502&doi=10.1016%2fj.rse.2007.03.004&partnerID=40&md5=c3775005dc9db285b53f301e67f1cac3","The boreal tree line is expected to advance upwards into the mountains and northwards into the tundra due to global warming. The major objective of this study was to find out if it is possible to use high-resolution airborne laser scanner data to detect very small trees - the pioneers that are pushing the tree line up into the mountains and out onto the tundra. The study was conducted in a sub-alpine/alpine environment in southeast Norway. A total of 342 small trees of Norway spruce, Scots pine, and downy birch with tree heights ranging from 0.11 to 5.20 m were precisely georeferenced and measured in field. Laser data were collected with a pulse density of 7.7 m- 2. Three different terrain models were used to process the airborne laser point cloud in order to assess the effects of different pre-processing parameters on small tree detection. Greater than 91% of all trees &gt; 1 m tall registered positive laser height values regardless of terrain model. For smaller trees (&lt; 1 m), positive height values were found in 5-73% of the cases, depending on the terrain model considered. For this group of trees, the highest rate of trees with positive height values was found for spruce. The more smoothed the terrain model was, the larger the portion of the trees that had positive laser height values. The accuracy of tree height derived from the laser data indicated a systematic underestimation of true tree height by 0.40 to 1.01 m. The standard deviation for the differences between laser-derived and field-measured tree heights was 0.11-0.73 m. Commission errors, i.e., the detection of terrain objects - rocks, hummocks - as trees, increased significantly as terrain smoothing increased. Thus, if no classification of objects into classes like small trees and terrain objects is possible, many non-tree objects with a positive height value cannot be separated from those actually being trees. In a monitoring context, i.e., repeated measurements over time, we argue that most other objects like terrain structures, rocks, and hummocks will remain stable over time while the trees will change as they grow and new trees are established. Thus, this study indicates that, given a high laser pulse density and a certain density of newly established trees, it would be possible to detect a sufficient portion of newly established trees over a 10 years period to claim that tree migration is taking place."
"57203051832;7006894780;14028759700;","Modelling tree height to assess climatic conditions at tree lines in the Bolivian Andes",2007,"10.1016/j.ecolmodel.2007.05.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548387569&doi=10.1016%2fj.ecolmodel.2007.05.001&partnerID=40&md5=28bd2af20b06e797eb2a80d3b0b0151a","One of the major problems in assessing growth conditions of trees at upper tropical tree lines is that the vast majority of tree lines have been influenced or destroyed by human activities. Confronted with this situation, we modelled tree height of Polylepis trees in the Bolivian Andes correlating field data from 167 Polylepis stands and a climatic model at a resolution of 925 m × 925 m, across a wide range of elevations and tree growth conditions. Overall, mean annual temperature showed the strongest relationship to tree height (r2 = 0.73), closely followed by a temperature index summing up temperatures above 6.5 °C (r2 = 0.71) and elevation (r2 = 0.68). Mean annual precipitation (r2 = 0.32), humidity balance (r2 = 0.27), potential evaporation (r2 = 0.26), and solar radiation (r2 = 0.18) all showed much weaker relationships to tree height. However, when we divided the Bolivian Andes into three contrasting bioclimatic regions and used residual tree height (against temperature) as a variable, in the humid NE Bolivian Andes solar radiation was significantly positively related to residuals of tree height, in semi-arid SE Bolivia humidity balance and mean annual precipitation had positive and solar radiation negative influence, and in the arid W cordillera mean annual precipitation had positive influence. Our modelling approach thus confirms the overall predominance of temperatures in determining tree height growth. This temperature-determined pattern is regionally modified by positive effects of increasing water availability in arid regions and of increasing solar radiation in very humid and cloudy regions. This suggests that tree growth is primarily limited by temperatures (ca. 70% of the variance explained), but that water and light availability also play a role (an additional 5%). Accordingly, it appears that there may not be one constant factor limiting tree growth at high elevations, but rather that different tree lines may be affected by different combinations of climatic factors which in turn lead to different ecophysiological effects. © 2007."
"6602873453;","A model study of smoke-haze influence on clouds and warm precipitation formation in Indonesia 1997/1998",2007,"10.1016/j.atmosenv.2007.04.050","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548805440&doi=10.1016%2fj.atmosenv.2007.04.050&partnerID=40&md5=2e9a34f10bafdb23f7fd97d4d23bb45f","In the last few decades, fire and smoke-haze occurrence increased in Indonesia by intentionally set land clearing fires and higher fire susceptibility of disturbed forests. Particularly, during El Niño years with prolonged droughts in Indonesia, land clearing fires become uncontrolled wildfires and produce large amounts of gaseous and particulate emissions. This paper investigates the influence of smoke-haze aerosols from such fires on clouds and precipitation over Indonesia during the El Niño event 1997/1998 by numerical modelling. Warm precipitation formation in both layered and convective clouds is calculated dependent on the atmospheric aerosol concentration. In the smoke-haze affected regions of Indonesia, aerosol-cloud interactions induce events with both precipitation suppression and increase compared to a reference simulation without aerosol-cloud interactions. The effect of precipitation suppression is found to dominate with about 2/3 of all precipitation modification events pointing to a prolongation of smoke-haze episodes. The corresponding convective cloud top height of shallow clouds is increased whereas distinct lower deep convective cloud top heights are found. The remaining about 1/3 events are characterised by increased precipitation and cloud liquid water content, accompanied by lower convective cloud top heights of shallow clouds and higher deep convective clouds. © 2007 Elsevier Ltd. All rights reserved."
"8315173500;7006328089;","Cloud variability, radiative forcing and meridional temperature gradients in a general circulation model",2007,"10.1111/j.1600-0870.2007.00265.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548749237&doi=10.1111%2fj.1600-0870.2007.00265.x&partnerID=40&md5=1c2ec8672d7cb95b575a50b110640b55","Due to the non-linearity of cloud-radiation interaction in general circulation models (GCMs), the time-mean cloud radiative forcing (CRF) is in general different from the CRF of time-mean clouds. This implies that a change in temporal cloud variability induces a change in radiative forcing even if there is no change in time-mean cloud properties. Here we investigate this variability contribution to CRF quantitatively in the National Center for Atmospheric Research Community Climate Model 3.6 GCM. In a reference run, the variability contribution is found to account for 35% of the global-mean climatological CRF. The variability contribution peaks in the mid-latitudes and is shown to be driven by synoptic eddy activity. In a climate change experiment, where the atmospheric CO2 is quadrupled, the change in cloud variability offsets 40% of the change in CRF due to the change in mean clouds. It is found that almost all of this effect is due to variability in cloud fraction rather than in cloud water content, and it is traced to the non-linearity introduced by the model's treatment of vertical cloud overlap. This study indicates the possibility of an eddy variability-climate feedback that has not been extensively studied and quantified in the past. © 2007 The Authors Journal compilation © 2007 Blackwell Munksgaard."
"7103033047;","Trends in cloud cover from 1960 to 2005 over South Africa",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-36049007096&partnerID=40&md5=a697af2e6b9b76d82b925730e17fbe5d","Seasonal trends in low and total cloud cover, as well as for associated climate variables diurnal temperature range (DTR) and number of rain days, are investigated for South Africa. It is also investigated whether the observed trends and variability in cloud cover could be related to the El Niño-Southern Oscillation (ENSO) phenomenon, which has a major influence on the variability of summer rainfall in South Africa. These trends have not been investigated recently and in such detail. In the light of the climate change debate, updated studies of historical climate change are important, especially for regions and climate variables of which such studies are not published often. Seasonal trends of daily means were examined from quality-controlled data time series of 28 climate stations over South Africa, for the period 1960 to 2005. Regional trends could be determined by averaging series of stations showing similar trends, within areas delineated in such a way that the trend of the averaged series would be statistically significant. In this way the intra-seasonal spatial variability of same trend regions, as well as the spatial relationships between trends of the different climate variables under discussion, could be established. The main results, taking all seasons into account, is a general decrease in mean daily low cloud cover, and to a lesser extent total cloud cover, over most of South Africa, but an increase in the south and south-west of the country. However, the sizes of same trend regions show considerable variability between seasons. While trends in DTR and rain days are the opposite and the same, respectively, of trends in cloud cover in most cases, it is shown that this is not always the case. A region covering the northern, central and western interior of South Africa, with late-summer (JFM) cloud cover negatively correlated with equatorial Pacific sea-surface temperatures (SSTs), shows only a non-significant decrease in total and low cloud cover for JFM, which corresponds to a non-significant increase in equatorial Pacific SSTs during the same period."
"55879681300;57192912623;","Nested regional climate-chemistry simulations for central Europe",2007,"10.1016/j.crte.2007.09.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36049021865&doi=10.1016%2fj.crte.2007.09.018&partnerID=40&md5=05aada6fac65bbcb147a4d907b4dd7fe","The potential impact of global climate change on regional meteorology and near-surface ozone concentrations in central Europe and the effect of model resolution on the simulated quantities were studied using a coupled climate-chemistry model. Nested simulations with a horizontal resolution of 60 km for Europe and 20 km for central Europe were performed for two time slices of about 10 years representing present-day and future climate conditions. The model results indicate that increased solar radiation due to decreased cloud cover, higher temperatures, and enhanced isoprene emissions promote the formation of tropospheric ozone in central Europe under future climate conditions. Depending on the region, the increase of the mean daily maximum ranges between 2 and 10 ppb and exceedances of the threshold of 60 ppb for the 8-hourly mean as well as the AOT40 index were found to increase considerably. General tendencies in the regional distributions of near-surface ozone were similar for 60- and 20-km resolutions. However, pronounced regional differences were found for some regions due to stronger smoothing of anthropogenic and biogenic emissions as well as flattened topography for the 60-km resolution. © 2007 Académie des sciences."
"55334859900;7202975488;35502101300;","Tropical montane forest ecotones: Climate gradients, natural disturbance, and vegetation zonation in the Cordillera Central, Dominican Republic",2007,"10.1111/j.1365-2699.2007.01726.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34648827088&doi=10.1111%2fj.1365-2699.2007.01726.x&partnerID=40&md5=8c8f04d8e0538d6378e70e12a4e0c764","Aim: We examined relationships between climate-disturbance gradients and patterns of vegetation zonation and ecotones on a subtropical mountain range. Location: The study was conducted on the windward slopes of the Cordillera Central, Dominican Republic, where cloud forest appears to shift in a narrow ecotone to monodominant forest of Pinus occidentalis. Methods: Climate, disturbance and vegetation data were collected over the elevation range 1100-3100 m and in 50 paired plots along the ecotone. Aerial photographs were georeferenced to a high-resolution digital elevation model in order to enable the analysis of landscape-scale patterns of the ecotone. Results: A Shipley-Keddy test detected discrete compositional ecotones at 2200 and 2500 m; the distributions of tree species at lower elevations were continuous. The elevation of the ecotone determined with aerial photographs was fairly consistent, namely ± 164 m (SD) over its 124-km length, but it exhibited significant landscape variation, occurring at a lower elevation in a partially leeward, western zone. The ecotone also occurred significantly lower on ridges than it did in drainage gullies. Ecotone forest structure and composition differed markedly between paired plots. In pine paired plots, the canopy height was 1.7 times higher and the basal area of non-pine species was 6 times lower than in the cloud forest directly below. Fire evidence was ubiquitous in the pine forest but rare in the abutting cloud forest. Mesoclimate changed discontinuously around the elevation of the ecotone: humidity and cloud formation decreased markedly, and frost frequency increased exponentially. Main conclusions: The discreteness of the ecotone was produced primarily by fire. The elevational consistency of the ecotone, however, resulted from the overarching influence of mesoclimate on the elevational patterns of fire occurrence. Declining temperature and precipitation combine with the trade-wind inversion to create a narrow zone where high-elevation fires extinguish, enabling fire-sensitive and fire-tolerant taxa to abut. Once established, mesotopography and contrasting vegetation physiognomy probably reinforce this boundary through feedbacks on microenvironment and fire likelihood. The prominence of the pine in this study - and of temperate and fire-tolerant taxa in subtropical montane forests in general - highlights the importance of climate-disturbance- biogeography interactions in ecotone formation, particularly where fire mediates a dynamic between climate and vegetation. © 2007 The Authors."
"6603431534;7006204393;55740664200;35473805400;7202899330;7005626683;","Millimeter-wavelength radars: New frontier in atmospheric cloud and precipitation research",2007,"10.1175/BAMS-88-10-1608","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36049003821&doi=10.1175%2fBAMS-88-10-1608&partnerID=40&md5=5f7c8498c1364271a7a7e885e3464743","During the past 20 yr there has been substantial progress on the development and application of millimeter-wavelength (3.2 and 8.6 mm, corresponding to frequencies of 94 and 35 GHz) radars in atmospheric cloud research, boosted by continuous advancements in radar technology and the need to better understand clouds and their role in the Earth's climate. Applications of millimeter-wavelength radars range from detailed cloud and precipitation process studies to long-term monitoring activities that strive to improve our understanding of cloud processes over a wide range of spatial and temporal scales. These activities are the result of a long period of successful research, starting from the 1980s, in which research tools and sophisticated retrieval techniques were developed, tested, and evaluated in field experiments. This paper presents a cohesive, chronological overview of millimeter-wavelength radar advancements during this period and describes the potential of new applications of millimeter-wavelength radars on sophisticated platforms and the benefits of both lower- and higher-frequency radars for cloud and precipitation research. © 2007 American Meteorological Society."
"6701511324;6603271938;35392584500;6603247427;7003979342;57119668700;6602206729;","Tests of Monte Carlo Independent Column Approximation in the ECHAM5 atmospheric GCM",2007,"10.1175/JCLI4290.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35448966212&doi=10.1175%2fJCLI4290.1&partnerID=40&md5=9cb4a1ae83c4ed5194dfd661e49dc9cb","The Monte Carlo Independent Column Approximation (McICA) method for computing domain-average radiative fluxes allows a flexible treatment of unresolved cloud structure, and it is unbiased with respect to the full ICA, but its flux estimates contain conditional random noise. Here, tests of McICA in the ECHAM5 atmospheric GCM are reported. ECHAM5 provides an interesting test bed for McICA because it carries prognostic variables for the subgrid-scale probability distribution of total water content, which allows us to determine subgrid-scale cloud variability directly from the resolved-scale model variables. Three experiments with differing levels of radiative noise, each consisting of ten 6-yr runs, are performed to estimate the impact of McICA noise on simulated climate. In an experiment that attempted to deliberately maximize McICA noise, a systematic reduction in low cloud fraction occurred. For a more reasonable implementation of McICA, the impact of noise is very small, although statistically discernible. In terms of the impacts of noise, McICA appears to be a viable approach for use in ECHAM5. However, to improve the simulation of cloud radiative effects, realistic representation of both unresolved and resolved cloud structures is needed, which remains a challenging problem. Comparison of ECHAM5 data with a global cloud system-resolving model dataset and with International Satellite Cloud Climatology Project data suggested two problems related to unresolved cloud structures. First, ECHAM5 appears to underestimate subgrid-scale cloud variability. This problem seems partly related to the use of the beta distribution scheme for total water content in ECHAM5: in its current form, the scheme is unable to generate highly inhomogeneous clouds (relative standard deviation of condensate amount >1). Second, it appears that in ECHAM5, overcast cloud layers occur too frequently and partially cloudy layers too rarely. This problem is not unique to the beta distribution scheme; in fact, it is more pronounced when using an alternative, relative humidity-based cloud fraction scheme. © 2007 American Meteorological Society."
"55351503200;7005052420;7202745975;","A weather generator for hydrological, ecological, and agricultural applications",2007,"10.1029/2006WR005364","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35349004764&doi=10.1029%2f2006WR005364&partnerID=40&md5=6f918930bf2c2e03f9e626846a492b03","[1] This paper presents a weather generator that allows simulation of hydrometeorological variables representative of a given geographic location: precipitation, total cloud cover, incoming shortwave radiation, air temperature, humidity, and wind speed. The approach captures the essential relationships among the quantities of interest, while modeling the diurnal variation of weather conditions at the hourly scale. Precipitation is considered to be the key driver of simulated hydrometeorological conditions, which leads to a consistent covariation of the weather variables. The generator was calibrated and validated with data from three meteorological stations located in New Mexico, Arizona, and Oklahoma. The set of variables reproduced by the weather generator can serve as input to a number of models of environmental systems, involving hydrological, ecological, water resources, and agricultural applications. The model is also suitable for creating scenarios of climate regimes (e.g., dry versus wet climates) useful in sensitivity studies. The source codes of the weather generator, manual, and test applications are publicly available. Copyright 2007 by the American Geophysical Union."
"7410041005;","A refined two-channel microwave radiometer liquid water path retrieval for cold regions by using multiple-sensor measurements",2007,"10.1109/LGRS.2007.900752","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35348843538&doi=10.1109%2fLGRS.2007.900752&partnerID=40&md5=ba3ddfeb6cc5f65ceb0c7f09b7b53472","Traditional two-channel microwave radiometers (MWRs) are widely used to measure cloud liquid water path (LWP); however, the retrieved LWPs are subject to relatively large uncertainties, particularly for low LWP clouds. By reformulating the statistical retrieval method with clear-sky measurements as a reference, a simple method is presented to significantly reduce uncertainties in the LWP retrieval due to errors in MWR calibration, uncertainties in the absorption coefficients of atmospheric gases, and variations in the vertical profiles of temperature and pressure. The improvement is illustrated by comparing the statistics of the erroneous clear-sky LWP for the Department of Energy's Atmospheric Radiation Measurement Program Climate Research Facility observations at the North Slope of Alaska site and by comparing LWP retrieved with a multiple-sensor algorithm and LWP retrieved based mainly on MWR measurements. This letter also demonstrates the importance of using correct water cloud temperature and temperature-dependent water absorption coefficients for MWR LWP retrieval over cold regions. This approach can be easily implemented for combined MWR, ceilometer, and surface meteorological measurements. © 2007 IEEE."
"35489629800;57197404404;7203047486;","Fertilization responses of soil litter fauna and litter quantity, quality, and turnover in low and high elevation forests of Puerto Rico",2007,"10.1016/j.apsoil.2007.03.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548022342&doi=10.1016%2fj.apsoil.2007.03.012&partnerID=40&md5=e150a1d701089e15574582127a030094","This study evaluates the effects of chemical fertilization on litter production, litter arthropods, and earthworms in tropical wet and cloud forests in the Luquillo Mountains in northeastern Puerto Rico. Litter production, chemistry and turnover, forest floor mass, litter arthropod density (individuals g-1 dry litter), abundance (individuals m-2) and diversity, and earthworm abundance and fresh mass (g m-2) were measured in 20 m × 20 m control and fertilized plots. We hypothesized that fertilization would increase litter arthropod density, abundance and diversity in both forests through elevating litter production and improving litter quality, and the increased litter quality in fertilized plots was also expected to result in faster litter turnover rates. Fertilization significantly increased monthly litterfall production and litter quality as measured by leaf litter C/N and C/P ratios in both forests, and higher litter production led to significant litter accumulation on the forest floor. Litter arthropod abundance increased in the wet forest fertilized plots due to the accumulated litter. Higher litter quality did not affect litter arthropod density in either forest, and densities were slightly higher in the cloud forest. High litter quality increased litter turnover rate in the cloud forest only. A significant reduction in earthworm populations in fertilized plots may have offset the positive effect of litter quality on litter turnover in the wet forest. Shannon biodiversity index for litter arthropod taxa was similar between treatments in the wet forest, and was higher in the wet forest than cloud forest. We conclude that climate influences litter arthropod diversity, but differences in litter quantity and quality do not affect their densities in island tropical wet and cloud forests. © 2007 Elsevier B.V. All rights reserved."
"8420354200;8750834400;7402452055;6701778684;36155758500;57204901815;7202459859;57191076887;55576176900;36039858000;7003567733;6506322240;7102613897;6603375632;55850691100;55723405300;36155343600;57080213400;22136719900;9249296100;35389408800;","Planet-C: Venus Climate Orbiter mission of Japan",2007,"10.1016/j.pss.2007.01.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548204458&doi=10.1016%2fj.pss.2007.01.009&partnerID=40&md5=f978db42eba552f738f5993fcad42405","The Venus Climate Orbiter mission (PLANET-C), one of the future planetary missions of Japan, aims at understanding the atmospheric circulation of Venus. Meteorological information will be obtained by globally mapping clouds and minor constituents successively with four cameras at ultraviolet and infrared wavelengths, detecting lightning with a high-speed imager, and observing the vertical structure of the atmosphere with radio science technique. The equatorial elongated orbit with westward revolution fits the observation of the movement and temporal variation of the atmosphere which as a whole rotates westward. The systematic, continuous imaging observations will provide us with an unprecedented large data set of the Venusian atmospheric dynamics. Additional targets of the mission are the exploration of the ground surface and the observation of zodiacal light. The mission will complement the ESA's Venus Express, which also explores the Venusian environment with different approaches. © 2007 Elsevier Ltd. All rights reserved."
"6603125722;7101735729;36815358800;","Importance of orographic precipitation to the water resources of Monteverde, Costa Rica",2007,"10.1016/j.advwatres.2006.07.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547599047&doi=10.1016%2fj.advwatres.2006.07.008&partnerID=40&md5=31e957ed193007fe8031d413797c8eba","Monteverde, Costa Rica harbors montane forests that exemplify the delicate balances among climate, hydrology, habitat, and development. Most of the annual precipitation to this region arrives during the wet season, but the importance of orographic precipitation during the dry and transitional seasons should not be underestimated. Development associated with ecotourism has put significant stress on water resources, and recent work has shown evidence that changes in regional land-cover and global climate may lead to reduced precipitation and cloud cover and a subsequent decline in endemic species. Precipitation samples collected from 2003 to 2005 reveal a seasonal signal in stable isotope composition, as measured by δ18O and δ2H, that is heaviest during the dry and transitional seasons. Attenuated versions of this signal propagate through to stream samples and provide a means of determining the importance of precipitation delivered by the trade winds during the dry and transitional seasons to water resources for the region. Results from six catchments on the leeward slope indicate that topography exerts a strong control on the importance of orographic precipitation to stream baseflow. The contributions are greatest in those catchments that are close to the Brillante Gap in the Continental Divide. Differences in the temporal variation of precipitation and streamflow isotope compositions provide insight to the hydrologic pathways that move water to the streams. © 2007 Elsevier Ltd. All rights reserved."
"7102591209;6602350870;","A self-consistent scattering model for cirrus. I: The solar region",2007,"10.1002/qj.164","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38849143166&doi=10.1002%2fqj.164&partnerID=40&md5=c2af0f01951841972a33c870733e453c","In this paper a self-consistent scattering model for cirrus is presented. The model consists of an ensemble of ice crystals where the smallest ice crystal is represented by a single hexagonal ice column. As the overall ice crystal size increases, the ice crystals become progressively more complex by arbitrarily attaching other hexagonal elements until a chain-like ice crystal is formed, this representing the largest ice crystal in the ensemble. The ensemble consists of six ice crystal members whose aspect ratios (ratios of the major-to-minor axes of the circumscribed ellipse) are allowed to vary between unity and 1.84 for the smallest and largest ice crystal, respectively. The ensemble model's prediction of parameters fundamental to solar radiative transfer through cirrus such as ice water content and the volume extinction coefficient is tested using in situ based data obtained from the midlatitudes and Tropics. It is found that the ensemble model is able to generally predict the ice water content and extinction measurements within a factor of two. Moreover, the ensemble model's prediction of cirrus spherical albedo and polarized reflection are tested against a space-based instrument using one day of global measurements. The space-based instrument is able to sample the scattering phase function between the scattering angles of approximately 60° and 180°, and a total of 37 581 satellite pixels were used in the present analysis covering latitude bands between 43.75°S and 76.58°N. It is found that the ensemble model phase function is well able to minimize significantly differences between satellite-based measurements of spherical albedo and the ensemble model's prediction of spherical albedo. The satellite-based measurements of polarized reflection are found to be reasonably described by more simple members of the ensemble. The ensemble model presented in this paper should find wide applicability to the remote sensing of cirrus as well as more fundamental solar radiative transfer calculations through cirrus, and improved solar optical properties for climate and Numerical Weather Prediction models. Copyright © 2007 Royal Meteorological Society."
"23009601400;57203235663;","Evaluation of the hydrological cycle over the Mississippi River Basin a simulated by the Canadian regional climate model (CRCM)",2007,"10.1175/JHM627.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36348961925&doi=10.1175%2fJHM627.1&partnerID=40&md5=d942db8fc0b33ac90c0dce1008cf54ec","The water cycle over a given region is governed by many complex multiscale interactions and feedbacks, and their representation in climate models can vary in complexity. To understand which of the key processes require better representation, evaluation and validation of all components of the simulated water cycle are required. Adequate assessing of the simulated hydrological cycle over a given region is not trivial because observations for various water cycle components are seldom available at the regional scale. In this paper, a comprehensive validation method of the water budget components over a river basin is presented. In addition, the sensitivity of the hydrological cycle in the Canadian Regional Climate Model (CRCM) to a more realistic representation of the land surface processes, as well as radiation, cloud cover, and atmospheric boundary layer mixing is investigated. The changes to the physical parameterizations are assessed by evaluating the CRCM hydrological cycle over the Mississippi River basin. The first part of the evaluation looks at the basin annual means. The second part consists of the analysis and validation of the annual cycle of all water budget components. Finally, the third part is directed toward the spatial distribution of the annual mean precipitation, evapotranspiration, and runoff. Results indicate a strong response of the CRCM evapotranspiration and precipitation biases to the physical parameterization changes. Noticeable improvement was obtained in the simulated annual cycles of precipitation, evapotranspiration, moisture flux convergence, and terrestrial water storage tendency when more sophisticated physical parameterizations were used. Some improvements are also observed for the simulated spatial distribution of precipitation and evapotranspiration. The simulated runoff is less sensitive to changes in the CRCM physical parameterizations. © 2007 American Meteorological Society."
"15070038800;21734131700;57192107995;7006347751;","Generation of internally mixed insoluble and soluble aerosol particles to investigate the impact of atmospheric aging and heterogeneous processing on the CCN activity of mineral dust aerosol",2007,"10.1080/02786820701557222","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548567823&doi=10.1080%2f02786820701557222&partnerID=40&md5=3845e7e100b5de81209f850a1ff7bcd2","Heterogeneous reactions of trace gases with mineral dust aerosol not only impact the chemical balance of the atmosphere but also the physicochemical properties of the dust particle and the ability of the particle to act as a cloud condensation nuclei (CCN). Recent field studies have shown that carbonate minerals are preferentially associated with nitrates whereas aluminum silicates (i.e., clay minerals) are preferentially associated with sulfates. To better understand how this association can impact the climate effects of mineral dust particles, we have measured the CCN activity of a number of pure and internal mixtures of aerosols relevant to these recent field studies. The CCN activity of CaCO3-Ca(NO3)2 aerosol, simulating the activity of mineral dust aerosol that has been partially processed by nitrogen oxides in the atmosphere, is significantly enhanced relative to CaCO3 aerosol of the same diameter. Similar results are obtained for a clay mineral, kaolinite, internally mixed with (NH4)2SO4. For example, at 0.3% supersaturation, a 200 nm particle containing a soluble nitrate or sulfate component is 2 to 4 times more active than an unreacted particle. The results presented here show that when determining the contribution of mineral dust aerosol to the overall impact of the aerosol indirect effect on radiative forcing, changes in chemical composition due to atmospheric processing cannot be ignored. Copyright © American Association for Aerosol Research."
"7005485117;9249731200;25226620200;","Prediction of the diurnal change using a multimodel superensemble. Part I: Precipitation",2007,"10.1175/MWR3446.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548576292&doi=10.1175%2fMWR3446.1&partnerID=40&md5=07d649265acc96777b3dd6413a89c899","Modeling the geographical distribution of the phase and amplitude of the diurnal change is a challenging problem. This paper addresses the issues of modeling the diurnal mode of precipitation over the Tropics. Largely an early morning precipitation maximum over the oceans and an afternoon rainfall maximum over land areas describe the first-order diurnal variability. However, large variability in phase and amplitude prevails even within the land and oceanic areas. This paper addresses the importance of a multimodel superensemble for much improved prediction of the diurnal mode as compared to what is possible from individual models. To begin this exercise, the skills of the member models, the ensemble mean of the member models, a unified cloud model, and the superensemble for the prediction of total rain as well as its day versus night distribution were examined. Here it is shown that the distributions of total rain over the earth (tropical belt) and over certain geographical regions are predicted reasonably well (RMSE less than 18%) from the construction of a multimodel superensemble. This dataset is well suited for addressing the diurnal change. The large errors in phase of the diurnal modes in individual models usually stem from numerous physical processes such as the cloud radiation, shallow and deep cumulus convection, and the physics of the planetary boundary layer. The multimodel superensemble is designed to reduce such systematic errors and provide meaningful forecasts. That application for the diurnal mode appears very promising. This paper examines some of the regions such as the Tibetan Plateau, the eastern foothills of the Himalayas, and the Amazon region of South America that are traditionally difficult for modeling the diurnal change. In nearly all of these regions, errors in phase and amplitude of the diurnal mode of precipitation increase with the increased length of forecasts. Model forecast errors on the order of 6-12 h for phase and 50% for the amplitude are often seen from the member models. The multimodel superensemble reduces these errors and provides a close match (RMSE < 6 h) to the observed phase. The percent of daily rain and their phases obtained from the multimodel superensemble at 3-hourly intervals for different regions of the Tropics showed a closer match (pattern correlation about 0.4) with the satellite estimates. This is another area where the individual member models conveyed a much lower skill. © 2007 American Meteorological Society."
"16403070500;25647939800;7401945370;","Spring diurnal cycle of clouds over Tibetan Plateau: Global cloud-resolving simulations and satellite observations",2007,"10.1029/2007GL030782","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36549006040&doi=10.1029%2f2007GL030782&partnerID=40&md5=257f43311c4d89bc7a10eb5b62055576","Thermal forcing of the Tibetan Plateau (TP) has large impacts on the Asian summer monsoon. In this study, we statistically analyzed the outputs from the global cloud-resolving model, NICAM (Nonhydrostatic ICosahedral Atmospheric Model). In order to investigate the convective activities, two brightness temperature datasets were compared, one derived from the satellite observation and another derived from the model. The model well simulated the spatio-temporal variations of convective clouds in April 2004. The diurnal cycle of clouds was better represented in NICAM, which shows only few-hour phase difference, than that in the reanalysis data. Three experiments changing horizontal resolution revealed that the higher resolution run conducts better representation of the diurnal cycle, especially on the nighttime disappearance of the high clouds. These results indicate that the global cloud-resolving model will improve the seasonal prediction of the Asian summer monsoon through better description on the thermal forcing of the Tibetan Plateau. Copyright 2007 by the American Geophysical Union."
"6603910424;7006367091;23019327900;7403232646;7005281574;7101877955;7402464825;","Observing the moist troposphere with radio occultation signals from COSMIC",2007,"10.1029/2007GL030458","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36549006537&doi=10.1029%2f2007GL030458&partnerID=40&md5=dd54fa3c8b449f568c7963fc04931f97","New approaches for observing the moist troposphere using radio occultation (RO) signals transformed to impact parameter representation by radio-holographic (RH) methods are presented. Large changes in the RH bending angle are used as indicators of significant vertical refractivity gradients that often occur on top of the atmospheric boundary layer (ABL), convective cloud layers such as the trade-wind inversion, and other moist layers in the free troposphere. RH amplitude fluctuations are used as an indicator of turbulence in the moist troposphere. The approaches are demonstrated using RO data from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) mission from September 2006. The global distributions of the ABL depths and tops of moist convective layers derived from COSMIC RO data correspond generally to the observed locations and structures of the Intertropical Convergence Zone and adjacent sub-tropical regions. The approaches are suitable for investigations of the temporal and spatial ABL variability. Copyright 2007 by the American Geophysical Union."
"56158622800;7006783796;8833356300;35308117100;55937653600;7407116104;7406683894;11940301100;7004678728;7003865921;","Summer dust aerosols detected from CALIPSO over the Tibetan Plateau",2007,"10.1029/2007GL029938","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36549016144&doi=10.1029%2f2007GL029938&partnerID=40&md5=67c6411de1ed7c2e88e600b251d825a9","Summertime Tibetan dust aerosol plumes are detected from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite. CALIPSO reveals that dust storms occur more frequently than previously found from Tibetan surface observations because few surface sites were available over remote northwestern Tibet due to high elevation and harsh climate. The Tibetan dust aerosol is characterized by column-averaged volume depolarization and total volume color ratios around 21% and 0.83, respectively. The dust layers appear most frequently around 4-7 km above mean sea level. The volume depolarization ratio for about 90% of the dust particles is less than 10% at low altitudes (3-5 km), while only about 50% of the particles have a greater depolarization ratio at higher altitudes (7-10 km). The 4-day back trajectory analyses show that these plumes probably originate from the nearby Taklamakan desert surface and accumulate over the northern slopes of the Tibetan Plateau. These dust outbreaks can affect the radiation balance of the atmosphere of Tibet because they both absorb and reflect solar radiation. Copyright 2007 by the American Geophysical Union."
"8656468000;7103399784;7102535623;26643043700;6701853567;","A numerical study of the South Atlantic circulation at the Last Glacial Maximum",2007,"10.1016/j.palaeo.2007.06.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548522093&doi=10.1016%2fj.palaeo.2007.06.018&partnerID=40&md5=bfee960a855ac9b15de34f2a49a9610f","In this study, we examine the simulation results from the paleoclimate version of the National Center of Atmospheric Research coupled Climate System Model (CSM 1.4) for the Last Glacial Maximum (LGM) in order to understand changes in the South Atlantic (SA) circulation relative to the Present Day (PD). The LGM simulation is validated with the available proxy data in the region. The results show good agreement, except in the eastern equatorial and eastern SA region, where the model is not able to reproduce the correct cloud cover and the associated air-sea interactions. Ocean transport in the PD simulation is in good agreement with observational estimates. Results show that at subsurface levels there are two distinct patterns: (i) strengthening of the transport for the LGM in the southern SA (35°S to 25°S); and (ii) weakening of the mass transport in the northern SA (25°S to the Equator). In intermediate layers, there is an intensification of the subtropical gyre and a northward shift of the South Equatorial Current (SEC) bifurcation for the LGM. This leads to the intensification of the southward transport by the Brazil Current (BC) and the associated BC recirculation cell in the southern basin for the LGM. This shift in the position of the SEC bifurcation leads to a weakening in the northward transport and the western recirculation of the central SEC in the northern basin. This northward shift of the SEC (upper limit of the subtropical gyre) is consistent with the northward shift observed in the subtropical convergence zone and suggests a displacement of the sub-tropical gyre 3°-5° towards the Equator. In deeper layers, a shallower and weaker North Atlantic Deep Water (NADW) circulation in the LGM contributes to the reduction of the southward transport in the northern part of the basin and is associated with a greater northward intrusion of Antarctic Bottom Water. This intrusion plus the increase of the Indian Water inflow is responsible for the northward transport intensification in the southern basin. © 2007 Elsevier B.V. All rights reserved."
"7201463831;7004315232;55383124200;7101941415;7102785020;6506612036;7003621869;7404061081;","Satellite-derived aerosol optical depth over dark water from MISR and MODIS: Comparisons with AERONET and implications for climatological studies",2007,"10.1029/2006JD008175","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36348965883&doi=10.1029%2f2006JD008175&partnerID=40&md5=5fbaa947400f8bde9ba2f507a63af7e2","Although the current Multiangle Imaging Spectroradiometer (MISR) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite passive remote sensing midvisible aerosol optical thickness (AOT) products are accurate overall to about 0.05 or 20%, they differ systematically on a global, monthly average basis, by about 0.03 to 0.05. Some key climate change and other applications require accuracies of 0.03 or better. The instruments are sufficiently stable and well characterized, and have adequate signal-to-noise, to realize such precision. However, assumptions made in the current standard aerosol retrieval algorithms produce AOT biases that must be addressed first. We identify the causes of AOT discrepancies over dark water under typical, relatively low AOT conditions and quantify their magnitudes on the basis of detailed analysis. Examples were selected to highlight key issues for which there are coincident MISR, MODIS, and Aerosol Robotic Network (AERONET) observations. Instrument calibration and sampling differences, assumptions made in the MISR and MODIS standard algorithms about ocean surface boundary conditions, missing particle property or mixture, options, and the way reflectances used in the retrievals are selected each contribute significantly to the observed differences under some circumstances. Cloud screening is also identified as a factor, though not fully examined here, as are the relatively rare high-AOT cases over ocean. Specific algorithm upgrades and further studies indicated by these findings are discussed, along with recommendations for effectively using the currently available products for regional and global applications. Copyright 2007 by the American Geophysical Union."
"35917252100;7005814217;7005513582;7004479957;","Climate sensitivity of tropical and subtropical marine low cloud amount to ENSO and global warming due to doubled CO2",2007,"10.1029/2006JD008174","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35748955226&doi=10.1029%2f2006JD008174&partnerID=40&md5=ae15febc7c259d6dcae9e3f5c75bed15","In this study, we systematically analyzed the sensitivity of tropical and subtropical marine low cloud amount to the short-term climate anomaly associated with the 1997-1998 El Niño and the long-term climate change caused by doubled CO2 using the International Satellite Cloud Climatology Project (ISCCP) cloud measurements, European Centre for Medium-Range Weather Forecasting (ECMWF) reanalyses, and the sea surface temperature (SST) forced and coupled simulations performed by the latest version of the National Center for Atmospheric Research (NCAR) and Geophysical Fluid Dynamics Laboratory (GFDL) climate models. It is found that the changes in low cloud amount associated with the 1997-1998 El Niño and the doubled CO2 induced climate change have different characteristics and are controlled by different physical processes. Most reduction in low cloud amount related to the 1997-1998 El Niño occurs in the eastern tropical Pacific associated with an upward large-scale motion and a weak atmospheric stability measured by the 500 hPa vertical velocity and the potential temperature difference between 700 hPa and the surface, and is negatively correlated to the local, SST anomaly. In addition to the other mechanisms suggested by the previous studies, our analyses based on the ISCCP observations indicate that the change in atmospheric convective activities in these regions is one of the reasons responsible for the change in low cloud amount. In contrast, most increase in low cloud amount due to doubled CO2 simulated by the NCAR and GFDL models occurs in the subtropical subsidence regimes associated with a strong atmospheric stability, and is closely related to the spatial change pattern of SST consistent with previous studies. The increase in low cloud amount appears to favor the location where SST is less increased. After removing the background mean SST increase due to doubled CO2, the results show a clear negative correlation between the change in low cloud and the SST change. An analysis based on the simple atmospheric mixed layer model demonstrates a thermodynamic reason for such a change. The increase in the above-inversion atmospheric stratification due to doubled CO2 tends to reduce the mixed layer depth in the areas with a small temperature increase, which helps to trap the moisture within the mixed layer, thus, favors low cloud formation. Copyright 2007 by the American Geophysical Union."
"6602636483;26643530600;7102063963;6603631763;7102171439;24071119300;","Comparison of AIRS, MODIS, CloudSat and CALIPSO cloud top height retrievals",2007,"10.1029/2007GL030676","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34848835605&doi=10.1029%2f2007GL030676&partnerID=40&md5=60666970c84cf1f7e5b46d331f0f4a73","Knowledge of cloud properties like cloud top height (CTH) is essential to understand their impact on the earth's radiation budget and on climate change. High spectral resolution measurements from the Atmospheric Infrared Sounder (AIRS) are well suited to reveal valuable e information about cloud altitude. The CTH retrievals derived from AIRS single field-of-view (FOV) radiance measurements are compared with the operational MODIS (Moderate Resolution Imaging Spectroradiometer) cloud product, and Level 2 products obtained from radar and lidar instruments onboard the EOS (Earth Observing System) CloudSat and the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellites. Two cases containing a variety of cloud conditions have been studied, and the strengths/shortcomings of CTH products from infrared (IR) sounder radiances are discussed. Copyright 2007 by the American Geophysical Union."
"22956930200;7005137442;","Intercomparison of tropical tropospheric humidity in GCMs with AMSU-B water vapor data",2007,"10.1029/2006GL029118","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35948941903&doi=10.1029%2f2006GL029118&partnerID=40&md5=f3eb24c989e255c79685c86238abdff2","We make use of microwave measurements of the tropical free tropospheric relative humidity (FTH) to evaluate the extent to which the water vapor distribution in four general circulation models is faithftil to reality. The comparison is performed in the tropics by sorting the FTH in dynamical regimes defined upon the 500 hPa vertical velocity. Because microwave radiation penetrates non-rainy and warin clouds, we are able to estimate the FTH over most of the dynamical regimes that characterize the tropics. The comparisons reveal that two models simulate a free troposphere drier than observed (<10%), while the others agree with the observations. Despite some differences, the level of agreement is good enough to lend confidence in the representation of atmospheric moistening processes. A climate change scenario, tested on two models, shows a tendency to maintain the FTH to an almost fixed value be it an ascending or a subsiding regime. Copyright 2007 by the American Geophysical Union."
"36489595600;7202620125;7201754973;56188731500;7202793894;7101700601;7404062063;","Polar mesosphere and lower thermosphere dynamics: 1. Mean wind and gravity wave climatologies",2007,"10.1029/2006JD008126","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35748964169&doi=10.1029%2f2006JD008126&partnerID=40&md5=a06f87fc09bdce9b9d957378a6a545fe","Mean wind and gravity wave climatologies are presented for the polar mesosphere and lower thermosphere (MLT). The data were derived using MF radars at Davis (69°S, 78°E) and Syowa (69°S, 40°E) in the Antarctic and Poker Flat (65°N, 147°W) and Andenes (69°N, 16°E) in the Arctic. The dynamics of the Antarctic MLT are found to be significantly different from the Arctic MLT. Summer maxima in both the westward and equatorward winds occur closer to the solstice in the Antarctic than in the Arctic. The greater symmetry around the solstice suggests radiative effects may play a greater role in controlling the state of the Antarctic MLT than in the Arctic, where dynamical effects appear to be more important. Gravity wave observations also suggest that wave drag may be greater in the Arctic than in the Antarctic. The equatorward flow near the mesopause persists later in summer in the Arctic than in the Antarctic, as do observations of polar mesospheric clouds and polar mesospheric summer echoes. All three phenomena begin at about the same time in each hemisphere, but end later in the Arctic than in the Antarctic. It is proposed that the magnitude of the meridional winds can be used as a proxy for gravity wave driving and the consequent adiabatic cooling in the MLT. Seasonal variations in gravity wave activity are predominately combinations of annual and semiannual components. Significant hemispheric differences are observed for both the timing and magnitude of these seasonal variations. Copyright 2007 by the American Geophysical Union."
"7402129369;7005228636;6701556472;24458137900;","Evaluation of the GOME Water Vapor Climatology 1995-2002",2007,"10.1029/2006JD008246","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35748965590&doi=10.1029%2f2006JD008246&partnerID=40&md5=c06799eec5bceea83d01f924762cfcde","An accurate knowledge of the 3-D water vapor (WV) field is still limited, because of the limited capabilities of sensors in the past to cover the whole Earth's surface and the lower part of the troposphere, as well as to measure over reasonably long time series. We show here water vapor total column retrieved from seven years of Global Ozone Monitoring Experiment (GOME) measurements collected from August 1995 until August 2002. Our aim is two-fold: (1) to evaluate the accuracy and the limitations of the GOME water vapor total column and (2) to demonstrate its potential for climate studies. The column retrieval makes use of two innovative techniques operating in tandem, namely the University of Graz empirical air mass factor ratioing technique (IGAM) and the Spectral Structure Parameterization (SSP) retrieval method. The GOME instrument and its follow-up instruments (SCIAMACHY and GOME-2), using these algorithms, have the capability to cover nearly the whole globe in cloud-free situations and collect robust WV total column information over more than 3 decades. In this work we evaluate the results for the first 7 years against independent in situ measurements from the operational WMO radiosonde network, against high spatial resolution water vapor columns from MERIS (the Medium Resolution Imaging Spectrometer on EnviSat) and also compare with ERA40 model results. The GOME water vapor total column exhibits a bias of less than 2.5% with an uncertainty of around 5 mm for collocated measurements against radiosonde and MERIS measurements. Spatial patterns and trends in the global distribution of WV total column fields from GOME against re-analysis model results are well correlated with temperature in the tropics, and exhibit a lesser degree of correlation in the extra tropics. Cloud-free total columns from GOME can be systematically lower by up to 5 mm in the sub-tropics with respect to the all-sky case. In contrast, the impact of the diurnal cycle on the monthly mean values is found to be very small. Copyright 2007 by the American Geophysical Union."
"6701606453;7202899330;","The tropical atmospheric energy budget from the TRMM perspective. Part II: Evaluating GCM representations of the sensitivity of regional energy and water cycles to the 1998-99 ENSO cycle",2007,"10.1175/JCLI4207.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35448978759&doi=10.1175%2fJCLI4207.1&partnerID=40&md5=119677af48bc2506105b1850e873a38b","The impact of clouds and precipitation on the climate is a strong function of their spatial distribution and microphysical properties, characteristics that depend, in turn, on the environments in which they form. Simulating feedbacks between clouds, precipitation, and their surroundings therefore places an enormous burden on the parameterized physics used in current climate models. This paper uses multisensor observations from the Tropical Rainfall Measuring Mission (TRMM) to assess the representation of the response of regional energy and water cycles in the tropical Pacific to the strong 1998 El Niño event in (Atmospheric Model Intercomparison Project) AMIP-style simulations from the climate models that participated in the Intergovernmental Panel on Climate Change's (IPCC's) most recent assessment report. The relationship between model errors and uncertainties in their representation of the impacts of clouds and precipitation on local energy budgets is also explored. With the exception of cloud radiative impacts that are often overestimated in both regions, the responses of atmospheric composition and heating to El Niño are generally captured in the east Pacific where the SST forcing is locally direct. Many models fail, however, to correctly predict the magnitude of induced trends in the west Pacific where the response depends more critically on accurate representation of the zonal atmospheric circulation. As a result, a majority of the models examined do not reproduce the apparent westward transport of energy in the equatorial Pacific during the 1998 El Niño event. Furthermore, the intermodel variability in the responses of precipitation, total heating, and vertical motion is often larger than the intrinsic ENSO signal itself, implying an inherent lack of predictive capability in the ensemble with regard to the response of the mean zonal atmospheric circulation in the tropical Pacific to ENSO. While ENSO does not necessarily provide a proxy for anthropogenic climate change, the results suggest that deficiencies remain in the representation of relationships between radiation, clouds, and precipitation in current climate models that cannot be ignored when interpreting their predictions of future climate. © 2007 American Meteorological Society."
"7402435469;57212416832;","A comparison of forecast errors in CAM2 and CAM3 at the ARM Southern Great Plains site",2007,"10.1175/JCLI4267.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35448958914&doi=10.1175%2fJCLI4267.1&partnerID=40&md5=d6780c90f3234a976258bff51cdce985","The authors compare short forecast errors and the balance of terms in the moisture and temperature prediction equations that lead to those errors for the Community Atmosphere Model versions 2 and 3 (CAM2 and CAM3, respectively) at T42 truncation. The comparisons are made for an individual model column from global model forecasts at the Atmospheric Radiation Measurement Program (ARM) Southern Great Plains site for the April 1997 and June-July 1997 intensive observing periods. The goal is to provide insight into parameterization errors in the CAM, which ultimately should lead to improvements in the way processes are modeled. The atmospheric initial conditions are obtained from the 40-yr ECMWF Re-Analysis (ERA-40). The land initial conditions are spun up to be consistent with those analyses. The differences between the model formulations that are responsible for the major differences in the forecast errors and/or parameterization behaviors are identified. A sequence of experiments is performed, accumulating the changes from CAM3 back toward CAM2 to demonstrate the effect of the differences in formulations. In June-July 1997 the CAM3 temperature and moisture forecast errors were larger than those of CAM2. The terms identified as being responsible for the differences are 1) the convective time scale assumed for the Zhang-McFarlane deep convection, 2) the energy associated with the conversion between water and ice of the rain associated with the Zhang-McFarlane convection parameterization, and 3) the dependence of the rainfall evaporation on cloud fraction. In April 1997 the CAM2 and CAM3 temperature and moisture forecast errors are very similar, but different tendencies arising from modifications to one parameterization component are compensated by responding changes in another component to yield the same total moisture tendency. The addition of detrainment of water in CAM3 by the Hack shallow convection to the prognostic cloud water scheme is balanced by a responding difference in the advective tendency. A halving of the time scale assumed for the Hack shallow convection was compensated by a responding change in the prognostic cloud water. Changes to the cloud fraction parameterization affect the radiative heating, which in turn modifies the stability of the atmospheric column and affects the convection. The resulting changes in convection tendency are balanced by responding changes in the prognostic cloud water parameterization tendency. © 2007 American Meteorological Society."
"7501720647;","The double-ITCZ problem in IPCC AR4 coupled GCMs: Ocean-atmosphere feedback analysis",2007,"10.1175/JCLI4272.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35448994853&doi=10.1175%2fJCLI4272.1&partnerID=40&md5=4b2dddb4ac7ccead3655811b8770e579","This study examines the double-intertropical convergence zone (ITCZ) problem in the coupled general circulation models (CGCMs) participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). The twentieth-century climate simulations of 22 IPCC AR4 CGCMs are analyzed, together with the available Atmospheric Model Intercomparison Project (AMIP) runs from 12 of them. To understand the physical mechanisms for the double-ITCZ problem, the main ocean-atmosphere feedbacks, including the zonal sea surface temperature (SST) gradient-trade wind feedback (or Bjerknes feedback), the SST-surface latent heat flux (LHF) feedback, and the SST-surface shortwave flux (SWF) feedback, are studied in detail. The results show that most of the current state-of-the-art CGCMs have some degree of the double-ITCZ problem, which is characterized by excessive precipitation over much of the Tropics (e.g., Northern Hemisphere ITCZ, South Pacific convergence zone, Maritime Continent, and equatorial Indian Ocean), and are often associated with insufficient precipitation over the equatorial Pacific. The excessive precipitation over much of the Tropics usually causes overly strong trade winds, excessive LHF, and insufficient SWF, leading to significant cold SST bias in much of the tropical oceans. Most of the models also simulate insufficient latitudinal asymmetry in precipitation and SST over the eastern Pacific and Atlantic Oceans. The AMIP runs also produce excessive precipitation over much of the Tropics, including the equatorial Pacific, which also leads to overly strong trade winds, excessive LHF, and insufficient SWF. This suggests that the excessive tropical precipitation is an intrinsic error of the atmospheric models, and that the insufficient equatorial Pacific precipitation in the coupled runs of many models comes from ocean-atmosphere feedback. Feedback analysis demonstrates that the insufficient equatorial Pacific precipitation in different models is associated with one or more of the following three biases in ocean-atmosphere feedback over the equatorial Pacific: 1) excessive Bjerknes feedback, which is caused by excessive sensitivity of precipitation to SST and overly strong time-mean surface wind speed; 2) overly positive SST-LHF feedback, which is caused by excessive sensitivity of surface air humidity to SST; and 3) insufficient SST-SWF feedback, which is caused by insufficient sensitivity of cloud amount to precipitation. Off the equator over the eastern Pacific stratus region, most of the models produce insufficient stratus-SST feedback associated with insufficient sensitivity of stratus cloud amount to SST, which may contribute to the insufficient latitudinal asymmetry of SST in their coupled runs. These results suggest that the double-ITCZ problem in CGCMs may be alleviated by reducing the excessive tropical precipitation and the above feedback-relevant errors in the atmospheric models. © 2007 American Meteorological Society."
"36934610300;7005231450;7005578774;","Hydroclimatic trends in the Mississippi River basin from 1948 to 2004",2007,"10.1175/JCLI4262.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35448999346&doi=10.1175%2fJCLI4262.1&partnerID=40&md5=43025efcfd99972f5899b2be294c66e1","The trends of the surface water and energy budget components in the Mississippi River basin from 1948 to 2004 are investigated using a combination of hydrometeorological observations and observation-constrained simulations of the land surface conditions using the latest version of the Community Land Model version 3 (CLM3). The atmospheric forcing data for the CLM3 were constructed by adding the intramonthly variations from the 6-hourly National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis to observation-based analyses of monthly precipitation, surface air temperature, and cloud cover. The model-based analysis suggests that, for the surface water budget, the observed increase in basin-averaged precipitation is compensated by increases in both runoff and evapotranspiration. For the surface energy budget, the decrease of net shortwave radiation associated with observed increases in cloudiness is compensated by decreases in both net longwave radiation and sensible heat flux, while the latent heat flux increases in association with wetter soil conditions. Both the simulated surface water and energy budgets support the view that evapotranspiration has increased in the Mississippi River basin from 1948 to 2004. Sensitivity experiments show that the precipitation change dominates the evapotranspiration trend, while the temperature and solar radiation changes have only small effects. Large spatial variations within the Mississippi River basin and the contiguous United States are also found. However, the increased evapotranspiration is ubiquitous despite spatial variations in hydrometeorology. © 2007 American Meteorological Society."
"7006307463;7203034123;12801992200;57189585133;7406683894;","On the climate forcing consequences of the albedo continuum between cloudy and clear air",2007,"10.1111/j.1600-0889.2007.00297.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547900699&doi=10.1111%2fj.1600-0889.2007.00297.x&partnerID=40&md5=5f65faa4f0a94d7792f9fc2660306bff","It has been long understood that the partly cloudy atmosphere manifests a continuum of states between the end members 'clear' and 'cloud.' Nevertheless, many research methods are premised on a dichotomy of states - for example, those that use 'cloud cover' or 'cloud-clearing.' Here we consider the consequences of this practice for studies of aerosol-climate effects. Aerosols affect the Earth's energy budget primarily by affecting albedo; therefore, we explore the nature of albedo variability in the partly cloudy marine boundary layer on scales down to a few tens of metres. We employ two diagnostic tools: A cloud resolving model and an albedo proxy derived from high altitude lidars. We show that a continuum of albedo values results from indeterminate and variable combinations of hydrated aerosol and wispy (including subvisible) clouds. Two consequences arise. First, cloud-clearing schemes employed by different observational methods are mutually inconsistent and are sensitive to concentrations of unactivated aerosol particles. Second, aerosol radiative forcing (the sensitivity of overall albedo to changes in aerosol concentration) is inaccurately calculated as the average of clear and overcast conditions. Together, these results imply that dividing the aerosol forcing problem into 'direct' and 'indirect' components may lead to substantial errors. © 2007 The Authors Journal compilation © 2007 Blackwell Munksgaard."
"7004384155;6504018529;57193920163;57207603330;","Evaluation of cirrus parameterizations for radiative flux computations in climate models using TOVS-ScaRaB satellite observations",2007,"10.1175/JCLI4251.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34648836827&doi=10.1175%2fJCLI4251.1&partnerID=40&md5=1546d4f9e9e12170209f3bc4566bdf17","Combined simultaneous satellite observations are used to evaluate the performance of parameterizations of the microphysical and optical properties of cirrus clouds used for radiative flux computations in climate models. Atmospheric and cirrus properties retrieved from Television and Infrared Observation Satellite (TIROS-N) Operational Vertical Sounder (TOVS) observations are given as input to the radiative transfer model developed for the Met Office climate model to simulate radiative fluxes at the top of the atmosphere (TOA). Simulated cirrus shortwave (SW) albedos are then compared to those retrieved from collocated Scanner for Radiation Budget (ScaRaB) observations. For the retrieval, special care has been given to angular direction models. Three parameterizations of cirrus ice crystal optical properties are represented in the Met Office radiative transfer model. These parameterizations are based on different physical approximations and different hypotheses on crystal habit. One parameterization assumes pristine ice crystals and two ice crystal aggregates. By relating the cirrus ice water path (IWP) retrieved from the effective infrared emissivity to the cirrus SW albedo, differences between the parameterizations are amplified. This study shows that pristine crystals seem to be plausible only for cirrus with IWP less than 30 g m-2. For larger IWP, ice crystal aggregates lead to cirrus SW albedos in better agreement with the observations. The data also indicate that climate models should allow the cirrus effective ice crystal diameter (De) to increase with IWP, especially in the range up to 30 g m-2. For cirrus with IWP less than 20 g m-2, this would lead to SW albedos that are about 0.02 higher than the ones of a constant De of 55 μm. © 2007 American Meteorological Society."
"57199843170;7003371432;7103172539;","Surface-absorbed and top-of-atmosphere radiation fluxes for the Mackenzie River Basin from satellite observations and a regional climate model and an evaluation of the model",2007,"10.3137/ao.450301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34748904106&doi=10.3137%2fao.450301&partnerID=40&md5=048d21fd7913f80bdf100034c058948d","Both the earth-reflected shortwave and outgoing longwave radiation (OLR) fluxes at the top of the atmosphere (TOA) as well as surface-absorbed solar fluxes from Canadian Regional Climate Model (CRCM) simulations of the Mackenzie River Basin for the period March 2000 to September 2003 are compared with the radiation fluxes deduced from satellite observations. The differences between the model and satellite solar fluxes at the TOA and at the surface, which are used in this paper to evaluate the CRCM performance, have opposite biases under clear skies and overcast conditions, suggesting that the surface albedo is underestimated while cloud albedo is overestimated. The slightly larger differences between the model and satellite fluxes at the surface compared to those at the TOA indicate the existence of a small positive atmospheric absorption bias in the model. The persistent overestimation of TOA reflected solar fluxes and underestimation of the surface-absorbed solar fluxes by the CRCM under all sky conditions are consistent with the overestimation of cloud fraction by the CRCM. This results in a larger shortwave cloud radiative forcing (CRF) both at the TOA and at the surface in the CRCM simulation. The OLR from the CRCM agrees well with the satellite observations except for persistent negative biases during the winter months under all sky conditions. Under clear skies, the OLR is slightly underestimated by the CRCM during the winter months and overestimated in the other months. Under overcast conditions the OLR is underestimated by the CRCM, suggesting an underestimation of cloud-top temperature by the CRCM. There is an improvement in differences between model and satellite fluxes compared to previously reported results largely because of changes to the treatment of the surface in the model."
"7005629694;35231062700;7006193614;6602583669;","Trends in solar radiation due to clouds and aerosols, southern India, 1952-1997",2007,"10.1002/joc.1487","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548598663&doi=10.1002%2fjoc.1487&partnerID=40&md5=f91bebe4cd22115b869a57954d204a3e","Decadal trends in cloudiness are shown to affect incoming solar radiation (SWSFC) in the Krishna River basin (13-20°N, 72-82°E), southern India, from 1952 to 1997. Annual average cloudiness at 14 meteorological stations across the basin decreased by 0.09% of the sky per year over 1952-1997. The decreased cloudiness partly balanced the effects of aerosols on incoming solar radiation (SWSFC), resulting in a small net increase in SWSFC in monsoon months (0.1-2.9 W m-2 per decade). During the non-monsoon, aerosol forcing dominated over trends in cloud forcing, resulting in a net decrease in SWSFC (-2.8 to -5.5 W m-2 per decade). Monthly satellite measurements from the International Satellite Cloud Climatology Project (ISCCP) covering 1983-1995 were used to screen the visual cloudiness measurements at 26 meteorological stations, which reduced the data set to 14 stations and extended the cloudiness record back to 1952. SWSFC measurements were available at only two stations, so the SWSFC record was extended in time and to the other stations using a combination of the Angstrom and Hargreaves-Supit equations. The Hargreaves-Supit estimates of SWSFC were then corrected for trends in aerosols using the literature values of aerosol forcing over India. Monthly values and trends in satellite measurements of SWSFC from National Aeronautics and Space Administration's (NASA's) surface radiation budget (SRB) matched the aerosol-corrected Hargreaves-Supit estimates over 1984-1994 (RMSE = 11.9 W m-2 5.2%). We conclude that meteorological station measurements of cloudiness, quality checked with satellite imagery and calibrated to local measurements of incoming radiation, provide an opportunity to extend radiation measurements in space and time. Reports of decreased cloudiness in other parts of continental Asia suggest that the cloud-aerosol trade-off observed in the Krishna basin may be widespread, particularly during the rainy seasons when changes in clouds have large effects on incoming radiation compared with aerosol forcing. Copyright © 2007 Royal Meteorological Society."
"57203920741;34882060600;57196542350;","Microwave response of seasonal snow-cover measured by using a ground-based radiometer at 6.93 and 18.7 GHz frequencies and at dual polarization",2007,"10.1007/BF03013492","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349562377&doi=10.1007%2fBF03013492&partnerID=40&md5=ef53a90cbaa757e59a40ad87bed36ff8","Snow cover is an important variable for climatic and hydrologic models due to its effects on surface albedo, energy, and moisture budgets. Passive microwave sensors can be used to monitor temporal and spatial variations in large-scale snow cover parameters, avoiding problems of cloud cover and polar nights.In the present study, brightness temperature values were estimated (using calibration curves) for moist snow on natural and blackbody/metal surface. TB response on snow depth, density, SWE and angular variation from nadir were measured and found that TB decreases with increase of snow depth and with increase of angle from nadir. Empirical relations were used to estimate emissivity, dielectric constant and dielectric loss factor. It was observed that emissivity decreases with the increase of dielectric constant. The dielectric constant and dielectric loss factor both increases with the increase of density.Experiments were performed during winter of year 2005 at Dhundi and Solang (H.P.), India, using ground based passive microwave radiometer having 6.9 and 18.7 GHz antenna frequencies at dual polarization. © Springer 2007."
"23977419900;57201235812;","The variability and heat budget of the upper ocean under the Chile-Peru stratus",2007,"10.1357/002224007783649510","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849100348&doi=10.1357%2f002224007783649510&partnerID=40&md5=f5c22d76af2ce8d457959e278acedfc9","The persistent stratus clouds found west of Chile and Peru are important for the coupling of the ocean and atmosphere in the eastern Pacific and thus in the climate of the region. The relatively cool sea-surface temperatures found west of Peru and northern Chile are believed to play a role in maintaining the stratus clouds over the region. In October 2000 a buoy was deployed at 20S, 85W, a site near the center of the stratus region, in order to examine the variability of sea-surface temperature and the temporal evolution of the vertical structure of the upper ocean. The buoy was well-instrumented and obtained accurate time series of the surface forcing as well as time series in the upper ocean of temperature, salinity, and velocity. The variability and the extent to which local forcing explains the temporal evolution of upper ocean structure and heat content was examined. The sources of heating (primarily surface fluxes with weaker contributions from Ekman convergence and transport) are found to be balanced by cooling from the gyre-scale circulation, an eddy flux divergence and vertical diffusion. The deduced eddy flux divergence term is bounded away from zero and represents an order one source of cooling (and freshening). We postulate that the eddy flux divergence represents the effect of the cold coherent eddies formed near the coast, which propagate westward and slowly decay. Direct advection of coastal upwelled water by Ekman transport is negligible. Thus the upwelled water does influence the offshore structure, but through the fluctuating mesoscale flow not the mean transport."
"7003758673;","The relationship between biodiversity and population centres: The high Andes region as an example",2007,"10.1007/s10531-007-9204-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548461670&doi=10.1007%2fs10531-007-9204-4&partnerID=40&md5=4da0b3aab7e39462da11c2f448065495","Several coarse-scale studies have demonstrated a positive correlation between biodiversity and human population density. In this paper this relationship is studied for part of the Andean highland, on a finer spatial scale than in earlier studies, and comparing bird distribution data with pre-Columbian as well as contemporary population centres. A particularly close correspondence was found between ancient population centres and high numbers of species with small distributions. This suggests that the growth of resident human cultures was related, in some way, to local factors which-over a much longer time-scale-stimulated the process of evolution of new species. This correspondence may be a consequence of climate moderation in the mountain areas leading to local persistence, of wild species as well as human communities. However, the result also suggests that we need to study to what extent high biodiversity as such, under certain conditions, yields environmental services which were important for people. It also suggests that traditional efforts to preserve biodiversity in wilderness areas with few people should be supplemented with efforts to promote a more sustainable development in the populated areas, allowing cloud forest and other biologically rich habitats to persist in suitable places near population centres. © 2007 Springer Science+Business Media B.V."
"8941441300;8941441200;8941441100;36080026700;18134578100;19933815800;55742392200;","Effect of atmospheric haze on the deterioration of visibility over the Pearl River Delta",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548173029&partnerID=40&md5=b3d7925cd52cf8fb7ab5cde211ce54c7","The studies on the effect of atmospheric aerosol on climate and environment are hot issues in the current circle of international science and technology. In recent years the pollution of aerosol is getting worse and worse over the Pearl River Delta. The clouds of aerosol occur all year round, with heavy pollution area located at the western side at the mouth of Pearl River. The haze weather mainly occurs from October to April next year, resulting in visibility deterioration. From the beginning of 1980s, visibility dramatically deteriorated, obviously increasing haze weather, in which there are three big fluctuations, showing the periods of pollutions of dust, sulphate and dust, fine particle from photochemical process and sulphate and dust accompanying with the development of economy respectively. The long-term tendency of visibility caused by fog and light fog does not show a tendency due to human activities or economic development, wich mainly shows the interannual and interdecadal variation of climate. The deterioration of visibility has close relation to the fine particles over Pearl River Delta, with half of PM10 overpass the limited value set by national second graded standard (150 μg m-3), meanwhile, all values of PM2.5 overpass the day-mean limited value of American national standard (65 μg m-3), especially from October to January next year, monthly mean values of PM2.5 almost reach two times of standard value, indicating the fine particle concentration is very high. The ratio of PM2.5 to PM10 is also very high, reaching 58%-77%, higher especially in dry season than in rainy season. Thus it is the fine particle pollution in aerosol pollution over the Pearl River Delta. Compared with the data of 15 years ago, the ratio of fine particle to aerosol has obviously increased."
"55724139300;55723539100;","Numerical simulations of impacts of urbanization on heavy rainfall in Beijing using different land-use data",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548186511&partnerID=40&md5=9b68b10908b0159ce90c91ea32be8418","A summer strong convective precipitation event on 10 July 2004 over Beijing is numerically simulated in this paper, and the impact of urban heat island (UHI) on summer convective rain is investigated. The analysis reveals that a mesoscale convective cloud cluster system leads to this heavy rainfall event, suggesting the supply of moisture by the large scale circulation before the initiation of precipitation, a generally weaker UHI of 2-3°C existed in the urban area. Much like a sea breeze, the anomalously warm urban air created relatively low pressure, inducing the inflow of cooler rural air towards the urban center, which is favorable to the ascending motion and the formation of convective precipitation over the urban area. In addition, the numerical simulation of the strong convective precipitation event suggests that the simulated result of precipitation using the 2002 LANDSAT-7 land-use data with 30-m resolution is much better than that using the 1992-1993 USGS land-use data with 1-km resolution, whether in the magnitude of rainfall or in the location of precipitation. The simulation confirms to some extent that the UHI has a significant role in causing extreme rainfall event."
"56611366900;7005862399;7005263785;55740664200;24765069600;","Theoretical expression for the autoconversion rate of the cloud droplet number concentration",2007,"10.1029/2007GL030389","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35948953542&doi=10.1029%2f2007GL030389&partnerID=40&md5=042e1e54269173b5b4848818c93ff68e","Accurate parameterization of the autoconversion rate of the cloud droplet concentration (number autoconversion rate in cm-3 s-1) is critical for evaluating aerosol indirect effects using climate models; however, existing parameterizations are empirical at best. A theoretical expression is presented in this contribution that analytically relates the number autoconversion rate to the liquid water content, droplet concentration and relative dispersion of the cloud droplet size distribution. The analytical expression is theoretically derived by generalizing the analytical formulation previously developed for the autoconversion rate of the cloud liquid water content (mass autoconversion rate in g cm-3 s-1). Further examination of the theoretical number and mass autoconversion rates reveals that the former is not linearly proportional to the latter as commonly assumed in existing parameterizations. The formulation forms a solid theoretical basis for developing multi-moment representation of the autoconversion process in atmospheric models in general. Copyright 2007 by the American Geophysical Union."
"8404544300;7006204597;","Strong dependence of cubic ice formation on droplet ammonium to sulfate ratio",2007,"10.1029/2007GL030471","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35948933837&doi=10.1029%2f2007GL030471&partnerID=40&md5=5b93928dbac4be5becac23bcc51df1a3","We show that the phase of ice that crystallizes in lution droplets, under conditions relevant for the upper troposphere (UT) and tropopause region (typically &gt;188 K), is strongly dependent on the ammonium to sulfate ratio (ASR) of the solute. Droplets of aqueous (NH4)3H(SO4)2 (ASR = 1.5) freeze dominantly to cubic ice over a range of temperatures relevant for the UT and tropopause; whereas aqueous NH4HSO4 (ASR = 1.0) droplets do not freeze dominantly to ice Ic at temperatures relevant for the UT and tropopause region. We also show that the amount of cubic ice formed in the aqueous solution droplets at temperatures below 200 K is independent of droplet size, whereas a size dependence was observed at higher temperatures. The implications of these results for the phase of ice that forms in upper tropospheric ice clouds and the potential impact on climate, water vapor, and ozone are briefly discussed. Copyright 2007 by the American Geophysical Union."
"57203012011;22956952000;16246205000;6507253351;7102011703;55738957800;","Impact of a modified convective scheme on the Madden-Julian Oscillation and El Niño - Southern Oscillation in a coupled climate model",2007,"10.1029/2007GL030637","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35949004388&doi=10.1029%2f2007GL030637&partnerID=40&md5=74cccacec961e12be7c028a6e9a0747c","The connection between the intraseasonal Madden-Julian Oscillation (MJO) and interannual El Niño - Southern Oscillation (ENSO) has been proposed and investigated for the last two decades. However, many fully coupled atmosphere-ocean general circulation models (GCMs) are still unable to simulate many important characteristics of these two phenomena partly due to the great uncertainty in the representation of subgrid-scale cloud systems. We report herein the simulation of an El Niño in a fully coupled GCM with a modified convection scheme, which captures many of the observed features of the 1997/1998 El Niño event. The representation of convection in the coupled model plays a major role in modeling both interannual ENSO and intraseasonal MJO variability in closer accord with observations, and in reproducing the evolution of 1997/1998 El Niño-type events. Copyright 2007 by the American Geophysical Union."
"22936531700;13406672500;12239699000;55574223711;","Dust plumes over the Pacific, Indian, and Atlantic oceans: Climatology and radiative impact",2007,"10.1029/2007JD008427","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35348949605&doi=10.1029%2f2007JD008427&partnerID=40&md5=4923f9b5c7fe6ecf531b821b428c251b","Multiple satellite data sets in conjunction with the Monte Carlo Aerosol-Cloud-Radiation (MACR) model are employed to determine climatological distributions and radiative impacts of dust plumes over the Pacific, Indian, and Atlantic oceans. Three target regions, namely the Yellow Sea (YS), Arabian Sea (AS), and Saharan Coast (SC), are examined for quantitative comparisons of dust properties and their impacts on climate. Twenty year averaged Advanced Very High Resolution Radiometer (AVHRR) aerosol optical depth (AOD) data clearly show the peak dust season for the three target regions, March-April-May for YS and June-July-August for AS and SC. Georgia Institute of Technology- Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) modeled dust AOD fraction and Moderate Imaging Spectroradiometer (MODIS) large-mode AOD ratio are adopted to evaluate the dust fraction estimate. Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction coefficient data are used to define the vertical distribution of dust. The elevated dust plumes are detected by subtracting the non-dust-season values from dust season values of SAGE II data, showing extinction peak around ∼4 km over AS and SC. Over YS, dust plumes are found presenting multilayered structure. The shortwave (SW) forcing of dust, although moderated by the longwave (LW) effect, dominates the net effects (SW + LW) of dust plumes. Under clear-sky (i.e., cloudless) conditions, dust plumes reduce about 5.9 W m-2, 17.8 W m-2 and 14.2 W m-2 regional and seasonal mean radiative flux reaching the surface over YS, AS, and SC, respectively. Of the three regions, dust plumes over AS have the largest effect on atmospheric heating owing to a lower single-scattering albedo and the relatively large dust loading. The maximum SW heating occurs over AS with the value around +0.5 K/day inside the dust layer at ∼4 km. The LW effect results in strong cooling throughout the dust layer and moderate heating below the dust layer, and dust plumes over SC exert the maximum LW effect on heating rates, with up to -0.5 K/day LW cooling in the free troposphere and about +0.3 K/day warming in the boundary layer. As the sum of the SW and the LW heating rates, net heating rate shows a more complex pattern. Over SC, large LW cooling inside the dust layer offsets up to 80% SW heating and results in about -0.1 K/day net heating rate change at the height ∼5 km in over SC. Over AS the net heating rate change is dominated by SW heating because the maximum LW cooling is less than 60% of the SW heating, which leads to +0.3 K/day net heating inside the dust layer and moderate heating below the dust base. The net heating rate change over YS is the smallest among the three regions, with magnitude within 0.1 K/day. Copyright 2007 by the American Geophysical Union."
"7102141244;6701757092;7101800834;","Omnipresence of biological material in the atmosphere",2007,"10.1071/EN07021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547981667&doi=10.1071%2fEN07021&partnerID=40&md5=2da1666371a295bd83469fc5f8493535","Measurements of biological particles in the atmosphere during the last decade indicate that the presence of these particles seems to have been underestimated by atmospheric scientists. On the average these primary aerosol particles might be present as much as 25% of the total mass (or number for particles with radius greater than 0.2 μm) concentration of the atmospheric aerosol. Such a large fraction certainly plays a major role in all processes affected by atmospheric aerosols, such as cloud and precipitation formation, climate forcing, visibility, turbidity, and so on. This disregard of the biological particles requires a new attitude in our opinion. © CSIRO 2007."
"56676874900;6602230939;7007034953;6602904617;","Cloud and radiation budget changes associated with tropical intraseasonal oscillations",2007,"10.1029/2007GL029698","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34948817205&doi=10.1029%2f2007GL029698&partnerID=40&md5=1572eadcd982231fdb4a0f2a9bacffe6","We explore the daily evolution of tropical intraseasonal oscillations in satellite-observed tropospheric temperature, precipitation, radiative fluxes, and cloud properties. The warm/rainy phase of a composited average of fifteen oscillations is accompanied by a net reduction in radiative input into the ocean-atmosphere system, with longwave heating anomalies transitioning to longwave cooling during the rainy phase. The increase in longwave cooling is traced to decreasing coverage by ice clouds, potentially supporting Lindzen's ""infrared iris"" hypothesis of climate stabilization. These observations should be considered in the testing of cloud parameterizations in climate models, which remain sources of substantial uncertainty in global warming prediction. Copyright 2007 by the American Geophysical Union."
"7004932211;6602438250;6701508267;10243910600;","Seasonal correlations of SST, water vapor, and convective activity in tropical oceans: A new hyperspectral data set for climate model testing",2007,"10.1029/2006GL029191","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34948880742&doi=10.1029%2f2006GL029191&partnerID=40&md5=92ebcab540ff8c47bdde3a4cd58bd28c","The analysis of the response of the Earth Climate System to the seasonal changes of solar forcing in the tropical oceans using four years of the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) data between 2002 and 2006 gives new insight into amplitude and phase relationships between surface and tropospheric temperatures, humidity, and convective activity. The intensity of the convective activity is measured by counting deep convective clouds. The peaks of convective activity, temperature in the mid-troposphere, and water vapor in the 0-30 N and 0-30 S tropical ocean zonal means occur about two months after solstice, all leading the peak of the sea surface temperature by several weeks. Phase is key to the evaluation of feedback. The evaluation of climate models in terms of zonal and annual means and annual mean deviations from zonal means can now be supplemented by evaluating the phase of key atmospheric and surface parameters relative to solstice. The ability of climate models to reproduce the statistical flavor of the observed amplitudes and relative phases for broad zonal means should lead to increased confidence in the realism of their water vapor and cloud feedback algorithms. AIRS and AMSU were launched into a 705 km altitude polar sun-synchronous orbit on the EOS Aqua spacecraft on May 4, 2002, and have beeen routine data gathering mode since September 2002. Copyright 2007 by the American Geophysical Union."
"7005072865;7402434077;7404096944;24278776400;56130997600;","Lidar measurements of Asian dust storms and dust cloud interactions",2007,"10.1029/2007JD008476","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35148841438&doi=10.1029%2f2007JD008476&partnerID=40&md5=088d65acd84f893795ab6c582f91a013","Long-range transport of Asian dust storms has been investigated by using lidar at Chungli (24.6°N, 121.1°E) in 2002-2004. One of the dust storms that occurred in the period of 27-31 March 2002 was also observed by lidar at Hefei (31.9°N, 117.16°E). The lidar height distributions of dust extinction were compared with back trajectory calculation and atmospheric data including First Global GARP Experiment (FGGE)-type ground observations and National Center for Environment Prediction/ Atmospheric Research (NCEP/NCAR) reanalysis. Dust layers had an average total (aerosol and molecular) depolarization ratio (DR) about 0.2; however, formation of droplets with near-zero depolarization ratio (0.02) was also measured. The cloud condensation nuclei (CCN) activities of dust particles were considered based on chemical properties observed from the ground. We observed that dust transport to the south may interact strongly with the moisture from the active weather system in the region producing significant climate effects. Copyright 2007 by the American Geophysical Union."
"7004868225;34571514100;56619491100;6506486381;34571084000;","Climate and behaviour in a Nordic city",2007,"10.1016/j.landurbplan.2007.01.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34447311380&doi=10.1016%2fj.landurbplan.2007.01.020&partnerID=40&md5=fc910cc72c6155848c12228407b8662d","Four urban public spaces, representing various designs and microclimates, were investigated in Gothenburg, Sweden, in order to estimate how weather and microclimate affect people in urban outdoor environments. The research strategy was both multidisciplinary and interdisciplinary and included scientists from three disciplines: architecture, climatology and psychology. The project is based on common case studies carried out during four seasons, including measurements of meteorological variables, interviews and observations of human activity at each place. Multiple regression analysis of meteorological and behavioural data showed that air temperature, wind speed and clearness index (cloud cover) have a significant influence on people's assessments of the weather, place perceptions and place-related attendance. The results support the arguments in favour of employing climate sensitive planning in future urban design and planning projects, as the physical component of a place can be designed to influence the site-specific microclimate and consequently people's place-related attendance, perceptions and emotions. © 2007 Elsevier B.V. All rights reserved."
"6603382743;17342751300;","Long-term changes to incoming solar energy on the Canadian Prairie",2007,"10.1016/j.agrformet.2007.04.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34447619667&doi=10.1016%2fj.agrformet.2007.04.011&partnerID=40&md5=97ada82b667bcc709c9583f358b43aa0","Many regions of the earth experienced a steady decline in solar radiation (global dimming) from the late 1950s to the late 1980s-early 1990s and a steady brightening thereafter. To determine trends in solar energy across the agricultural region of the Canadian Prairie, we analyzed incoming solar radiation, sunshine, and climate data gathered between 1951 and 2005 from 7 locations on the prairies. From the 1950s, there was a decreasing trend in annual average daily incoming solar radiation, no trend in annual average daily sunshine hours, and increasing trends in annual average daily temperature and in the annual number of precipitation/rain events. As well, we found the annual average daily incoming solar radiation decreased as the annual number of precipitation/rain events increased, but increased as the annual average precipitation intensity increased. We found the annual average daily sunshine hours decreased as the annual precipitation amount increased and as the annual average precipitation intensity increased. Thus, incoming solar radiation and sunshine responded differently to precipitation amount/events. Nevertheless, climate trends coupled with the relationship of solar radiation/sunshine to precipitation amount/events suggested that increased cloudiness played a key role in the extinction of solar radiation by the atmosphere over the past 50-60 years on the Canadian Prairie. Increasing greenhouse gas concentrations act to reduce cloudiness, whereas increasing aerosol concentrations often increase cloudiness. Specific to the Canadian Prairie, further research is needed to determine the influence of changing greenhouse gas and aerosol concentrations on cloudiness and cloud characteristics and the impact these changes would have on solar energy measured at the earth's surface. Crown Copyright © 2007."
"57203199846;7006535719;7203025162;23082420800;57202301596;","The effect of orbital forcing on the mean climate and variability of the tropical Pacific",2007,"10.1175/JCLI4240.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548476254&doi=10.1175%2fJCLI4240.1&partnerID=40&md5=1fd30231bc464f364a3551140c36af71","Using a coupled general circulation model, the responses of the climate mean state, the annual cycle, and the El Niño-Southern Oscillation (ENSO) phenomenon to orbital changes are studied. The authors analyze a 1650-yr-long simulation with accelerated orbital forcing, representing the period from 142 000 yr B.P. (before present) to 22 900 yr A.P. (after present). The model simulation does not include the time-varying boundary conditions due to ice sheet and greenhouse gas forcing. Owing to the mean seasonal cycle of cloudiness in the off-equatorial regions, an annual mean precessional signal of temperatures is generated outside the equator. The resulting meridional SST gradient in the eastern equatorial Pacific modulates the annual mean meridional asymmetry and hence the strength of the equatorial annual cycle. In turn, changes of the equatorial annual cycle trigger abrupt changes of ENSO variability via frequency entrainment, resulting in an anticorrelation between annual cycle strength and ENSO amplitude on precessional time scales. © 2007 American Meteorological Society."
"24341786100;7005805728;7201779750;6701910294;26643606100;57213092986;57194438001;7005058634;6602301658;7402534112;","Climate change and Australian marine life",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547611049&partnerID=40&md5=f4aa26753e6925b4a77ff172720e66ca","Australia's marine life is highly diverse and endemic. Here we describe projections of climate change in Australian waters and examine from the literature likely impacts of these changes on Australian marine biodiversity. For the Australian region, climate model simulations project oceanic warming, an increase in ocean stratification and decrease in mixing depth, a strengthening of the East Australian Current, increased ocean acidification, a rise in sea level, alterations in cloud cover and ozone levels altering the levels of solar radiation reaching the ocean surface, and altered storm and rainfall regimes. Evidence of climate change impacts on biological systems are generally scarce in Australia compared to the Northern Hemisphere. The poor observational records in Australia are attributed to a lack of studies of climate impacts on natural systems and species at regional or national scales. However, there are notable exceptions such as widespread bleaching of corals on the Great Barrier Reef and poleward shifts in temperate fish populations. Biological changes are likely to be considerable and to have economic and broad ecological consequences, especially in climate-change 'hot spots' such as the Tasman Sea and the Great Barrier Reef."
"7404142321;6603422104;","GCM intercomparison of global cloud regimes: Present-day evaluation and climate change response",2007,"10.1007/s00382-007-0232-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250023480&doi=10.1007%2fs00382-007-0232-2&partnerID=40&md5=cc9751267248a12933130df349f844e1","The radiative feedback from clouds remains the largest source of variation in climate sensitivity amongst general circulation models (GCMs). A cloud clustering methodology is applied to six contemporary GCMs in order to provide a detailed intercomparison and evaluation of the simulated cloud regimes. By analysing GCMs in the context of cloud regimes, processes related to particular cloud types are more likely to be evaluated. In this paper, the mean properties of the global cloud regimes are evaluated, and the cloud response to climate change is analysed in the cloud-regime framework. Most of the GCMs are able to simulate the principal cloud regimes, however none of the models analysed have a good representation of trade cumulus in the tropics. The models also share a difficulty in simulating those regimes with cloud tops at mid-levels, with only ECHAM5 producing a regime of tropical cumulus congestus. Optically thick, high top cloud in the extra-tropics, typically associated with the passage of frontal systems, is simulated considerably too frequently in the ECHAM5 model. This appears to be a result of the cloud type persisting in the model after the meteorological conditions associated with frontal systems have ceased. The simulation of stratocumulus in the MIROC GCMs is too extensive, resulting in the tropics being too reflective. Most of the global-mean cloud response to doubled CO2 in the GCMs is found to be a result of changes in the cloud radiative properties of the regimes, rather than changes in the relative frequency of occurrence (RFO) of the regimes. Most of the variance in the global cloud response between the GCMs arises from differences in the radiative response of frontal cloud in the extra-tropics and from stratocumulus cloud in the tropics. This variance is largely the result of excessively high RFOs of specific regimes in particular GCMs. It is shown here that evaluation and subsequent improvement in the simulation of the present-day regime properties has the potential to reduce the variance of the global cloud response, and hence climate sensitivity, amongst GCMs. For the ensemble of models considered in this study, the use of observations of the mean present-day cloud regimes suggests a potential reduction in the range of climate sensitivity of almost a third. © British Crown Copyright 2007."
"57198472289;7501757094;","SUNYA regional climate model simulations of East Asia summer monsoon: Effects of cloud vertical structure on the surface energy balance",2007,"10.3319/TAO.2007.18.3.493(EA)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35648958727&doi=10.3319%2fTAO.2007.18.3.493%28EA%29&partnerID=40&md5=8a7d1200482e79f9f12ab031d9ebcdd9","We used the State University of New York at Albany (SUNYA) regional climate model to study the effect of cloud vertical distribution in affecting the surface energy balance of the East Asia summer monsoon (EASM). Simulations were conducted for the summers of 1988 and 1989, during which large contrast in the intra-seasonal cloud radiative forcing (CRF) was observed at the top of the atmosphere. The model results indicate that both the high and low clouds are persistent throughout the summer months in both years. Because of large cloud water, low clouds significantly reduce the solar radiation flux reaching the surface, which nevertheless still dominate the surface energy balance, accounting for more than 50% of the surface heating. The low clouds also contribute significantly the downward longwave radiation to the surface with values strongly dependent on the cloud base temperature. The presence of low clouds effectively decreases the temperature and moisture gradients near surface, resulting in a substantial decrease in the sensible and latent heat fluxes from surface, which partially compensate the decrease of the net radiative cooling of the surface. For example, in the two days, May 8 and July 11 of 1988, the total cloud cover of 80% is simulated, but the respective low cloud cover (water) was 63% (114 gm-2) and 22% (21 gm-2). As a result, the downward solar radiation is smaller by 161 Wm-2 in May 8. On the other hand, the cloud temperature was 10°C lower, yielding 56 Wm-2 smaller downward longwave radiation. The near surface temperature and gradient is more than 1°C smaller (and moisture gradient), leading to 21 and 81 Wm-2 smaller sensible heat and latent heat fluxes. It is also demonstrated that the model is capable to reproduce the intra-seasonal variation of shortwave CRF, and catches the relationship between total cloud cover and SW CRF. The model results show the dominance of high cloud on the regional mean longwave CRF and low cloud on the intra-seasonal variation of shortwave CRF, indicating the importance of cloud vertical structure. The strong negative feedbacks from the responses of latent and sensible heat flux tend to limit the effects of low clouds on the surface temperature simulations, as evidently the surface air temperatures bias of only 0.34°C in the EASM simulations while the variances of the surface radiative fluxes and heat fluxes are, respectively, in the ranges of 100 - 200 and 60 - 110 Wm-2 when total cloud cover are all near 80%. Therefore, it is also concluded that surface air temperature, precipitation, and total cloud cover, which are three frequently examined variables for climate models, are not sufficient for model evaluation, but instead the cloud vertical structure needs to be examined."
"7102490158;22434361700;","Trends in cloud amount and radiative fluxes at Syowa Station, Antarctica",2007,"10.1016/j.polar.2007.04.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35048873288&doi=10.1016%2fj.polar.2007.04.001&partnerID=40&md5=a8f8419ff8032cca453e64bf05dac083","Variations of cloud amount and radiative fluxes are a matter of discussion related to the recent climate change in the Arctic and Antarctic. It is also of great concern related to ""from dimming to brightening"" recently found. Discussions based on satellite data had been conducted; however, no solid results are obtained from the surface station data for a long term in the recent. At Syowa Station, Antarctica, meteorological observation has been continued for nearly 50 years. During this term, an annual mean cloud amount showed a gradual increase at a rate of 0.014/yr. Radiation budget was observed since 1991 as one of the BSRN stations. Trends of monthly mean radiative fluxes were compared with those of cloud amount and conformable relations were seen during the period from 1991 to 2004. A cloud radiative forcing was estimated. In December, a downward trend in net longwave and net total appeared, while an upward trend in net shortwave was seen, and all corresponded to the decrease of cloud amount in this month. On the other hand in June, an upward trend in net longwave forcing was seen, corresponding to the increase of cloud amount. On an average, cloud radiative forcings at Syowa Station represented those of Antarctic costal stations near sea ice area. © 2007 Elsevier B.V. and NIPR."
"7103158465;57193882808;","Comparison of bulk and bin warm-rain microphysics models using a kinematic framework",2007,"10.1175/JAS3980","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548177831&doi=10.1175%2fJAS3980&partnerID=40&md5=7622987bcdd47ac61cf2a8a0faa57b46","This paper discusses the development and testing of a bulk warm-rain microphysics model that is capable of addressing the impact of atmospheric aerosols on ice-free clouds. Similarly to previous two-moment bulk schemes, this model predicts the mixing ratios and number concentrations of cloud droplets and drizzle/raindrops. The key elements of the model are the relatively sophisticated cloud droplet activation scheme and a comprehensive treatment of the collision-coalescence mechanism. For the latter, three previously published schemes are selected and tested, with a detailed (bin) microphysics model providing the benchmark. The unique aspect of these tests is that they are performed using a two-dimensional prescribed-flow (kinematic) framework, where both advective transport and gravitational sedimentation are included. Two quasi-idealized test cases are used, the first mimicking a single large eddy in a stratocumulus-topped boundary layer and the second representing a single shallow convective cloud. These types of clouds are thought to be the key in the indirect aerosol effect on climate. Two different aerosol loadings are considered for each case, corresponding to either pristine or polluted environments. In general, all three collision-coalescence schemes seem to capture key features of the bin model simulations (e.g., cloud depth, droplet number concentration, cloud water path, effective radius, precipitation rate, etc.) for the polluted and pristine environments, but there are detailed differences. Two of the collision-coalescence schemes require specification of the width of the cloud droplet spectrum, and model results show significant sensitivity to the specification of the width parameter. Sensitivity tests indicate that a one-moment version of the bulk model for drizzle/rain, which predicts rain/drizzle mixing ratio but not number concentration, produces significant errors relative to the bin model. © 2007 American Meteorological Society."
"6603752490;6603680545;7003532926;","Combined chemistry-climate model of the atmosphere",2007,"10.1134/S0001433807040020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548388979&doi=10.1134%2fS0001433807040020&partnerID=40&md5=0e51a6264902a949ab100981aed3872f","A combined three-dimensional global model of the chemistry and dynamics of the lower and middle atmosphere (up to 90 km from the Earth's surface) is described. With the use of this model within the AMIP2 (1979-1995) program, numerical calculations were performed with consideration for the interactive coupling between the ozone content, radiation heating, and atmospheric circulation. Comparisons were made between calculated and observed data on the ozone content and temperature. Heterogeneous processes on the surface of polar stratospheric clouds were shown to be important for a correct simulation of the spatial and temporal distribution of atmospheric ozone. © Pleiades Publishing, Ltd. 2007."
"56132618000;36950518200;","The role of cloud radiative forcing in the Asian-Pacific summer monsoon",2007,"10.3319/TAO.2007.18.3.623(A)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35649028440&doi=10.3319%2fTAO.2007.18.3.623%28A%29&partnerID=40&md5=769b70b77600ff431986513c62f34370","Convective-cloud clusters with strong precipitation occur frequently in most of the Asian-Pacific summer monsoon (APSM) regions such as the Bay of Bengal (BOB), South China Sea (SCS), and Tropical Western North Pacific (TWNP). Cloud radiative forcing (CRF) is important in these regions. The net CRF at the top of the atmosphere (TOA) has shown large cooling over these APSM regions. This is on account of the presence of large amounts of high clouds with large optical depth. Through data analysis, the summer convective precipitation in TWNP is as strong as that in the BOB. However, the average net CRF at the TOA in the BOB (∼ -36 Wm-2) is twice as big as in the TWNP (∼ -17 Wm-2). The spectral analysis of cloud optical depth shows that in the BOB, the highest power is in the intra-seasonal timescale, while in the TWNP, the leading spectral peaks are less than 10 days. The radiative cooling from net CRF at the TOA could be associated with low-frequency oscillation. The difference between the APSM regions is related to their sub-stages separating from CRF in time evolution. In a convective system, convective clouds can detrain to form other high clouds. In the APSM regions, large areas of high-thin and high-thick clouds cause different CRF at the TOA. These two types of CRF relate to precipitation, atmospheric vertical motion, and cloud life cycles etc. and should be separated from the APSM time evolution. We divided the APSM precipitation into two categories. As in the heavy-precipitation stage, clouds with large optical depth shield solar radiation and cause local and instantaneous surface cooling. The outgoing longwave radiation (OLR) is generally lower than 210 (Wm-2). The net CRF at the TOA is large negatively. Besides, large high-thin clouds can be found in a stage of relatively small or no precipitation. The OLR in this stage has a broad range and the net CRF is small and could be either positive or negative. The major difference between the APSM regions occurs in this stage. In this stage at the BOB, significant high-thick clouds cause negative net CRF, while more than half of the SCS and TWNP at this stage is dominated by large amounts of cirrus clouds. The optically thin cirrus clouds with large spatial size and long lasting time are important modulators for modifying the net CRF at the TOA. The poor simulation of the APSM climate in general circulation models (GCMs) maybe associated with the inability for accurately simulating the role of cirrus clouds in this stage. Based on the cloud classification of the International Satellite Cloud Climatology Project (ISCCP), we found a useful cloud-amount index from cloud amounts of cirrus minus the sum of deep convection and cirrostratus. The index can effectively separate different characteristics of CRF from the APSM time evolution. The cloud-amount index should be more appropriate for APSM studies and model simulations instead of considering only one cloud type in convective systems."
"6701392598;55225734700;","Tornadoes and other whirlwinds in the United Kingdom 2006",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548674005&partnerID=40&md5=20ab557eadfd152e0a6d2a5535cf4e38","Tornadoes, waterspouts, funnel clouds and other whirlwinds are summarised for 2006, and the data compared with 2004 and 2005. The numbers are again very high. Total number of tornado-related events for the UK reached 157 in 2006, as compared with 156 in 2004 and 189 in 2005. The year's major event happened on 7th December 2006 when a tornado tracked for several kilometres through part of the city of London, not far north of the city centre. Its maximum intensity was T5. When tornado events for Ireland are included using John Tyrrell's additional data, the numbers for 2006 for the whole of the British Isles are 76 (comprising 72 tornadoes and 4 waterspouts not making land fall). When other funnel clouds amounting to 96 events are included, the combined total for all tornadic events for the British Isles becomes 172. © The International Journal of Meteorology."
"7401984344;8225183400;7202226478;","Changes in cloud-ceiling heights and frequencies over the United States since the early 1950s",2007,"10.1175/JCLI4213.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548119501&doi=10.1175%2fJCLI4213.1&partnerID=40&md5=db3e7af13b59c64952e687bbea496cc0","U.S. weather stations operated by NOAA's National Weather Service (NWS) have undergone significant changes in reporting and measuring cloud ceilings. Stations operated by the Department of Defense have maintained more consistent reporting practices. By comparing cloud-ceiling data from 223 NWS first-order stations with those from 117 military stations, and by further comparison with changes in physically related parameters, inhomogeneous records, including all NWS records based only on automated observing systems and the military records prior to the early 1960s, were identified and discarded. Data from the two networks were then used to determine changes in daytime ceiling height (the above-ground height of the lowest sky-cover layer that is more than half opaque) and ceiling occurrence frequency (percentage of total observations that have ceilings) over the contiguous United States since the 1950s. Cloud-ceiling height in the surface-3.6-km layer generally increased during 1951-2003, with more significant changes in the period after the early 1970s and in the surface-2-km layer. These increases were mostly over the western United States and in the coastal regions. No significant change was found in surface-3.6-km ceiling occurrence during 1951-2003, but during the period since the early 1970s, there is a tendency for a decrease in frequency of ceilings with height below 3.6 km. Cloud-ceiling heights above 3.6 km have shown no significant changes in the past 30 yr, but there has been an increase in frequency, consistent with the increase in ceiling height below 3.6 km. For the surface-3.6-km layer, physically consistent changes were identified as related to changes in ceiling height and frequency of occurrence. This included reductions in precipitation frequency related to low ceiling frequency, and surface warming and decreasing relative humidity accompanying increasing ceiling heights during the past 30 yr. © 2007 American Meteorological Society."
"6701519241;6701341222;7004307308;57213740728;","A study on combining global and regional climate model results for generating climate scenarios of temperature and precipitation for the Netherlands",2007,"10.1007/s00382-007-0227-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249996232&doi=10.1007%2fs00382-007-0227-z&partnerID=40&md5=b45010ff4f1908f4471524e0ac866064","Climate scenarios for the Netherlands are constructed by combining information from global and regional climate models employing a simplified, conceptual framework of three sources (levels) of uncertainty impacting on predictions of the local climate. In this framework, the first level of uncertainty is determined by the global radiation balance, resulting in a range of the projected changes in the global mean temperature. On the regional (1,000-5,000 km) scale, the response of the atmospheric circulation determines the second important level of uncertainty. The third level of uncertainty, acting mainly on a local scale of 10 (and less) to 1,000 km, is related to the small-scale processes, like for example those acting in atmospheric convection, clouds and atmospheric meso-scale circulations - processes that play an important role in extreme events which are highly relevant for society. Global climate models (GCMs) are the main tools to quantify the first two levels of uncertainty, while high resolution regional climate models (RCMs) are more suitable to quantify the third level. Along these lines, results of an ensemble of RCMs, driven by only two GCM boundaries and therefore spanning only a rather narrow range in future climate predictions, are rescaled to obtain a broader uncertainty range. The rescaling is done by first disentangling the climate change response in the RCM simulations into a part related to the circulation, and a residual part which is related to the global temperature rise. Second, these responses are rescaled using the range of the predictions of global temperature change and circulation change from five GCMs. These GCMs have been selected on their ability to simulate the present-day circulation, in particular over Europe. For the seasonal means, the rescaled RCM results obey the range in the GCM ensemble using a high and low emission scenario. Thus, the rescaled RCM results are consistent with the GCM results for the means, while adding information on the small scales and the extremes. The method can be interpreted as a combined statistical-dynamical downscaling approach, with the statistical relations based on regional model output. © Springer-Verlag 2007."
"55740664200;7004034323;","The ARM Mobile Facility and its first international deployment: Measuring radiative flux divergence in West Africa",2007,"10.1175/BAMS-88-8-1229","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548646927&doi=10.1175%2fBAMS-88-8-1229&partnerID=40&md5=fb8b01631daede95d85cfd723634421e","The Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) was recently developed to enable collection of detailed climate data in locations not currently sampled by ARM's five fixed sites. The AMF includes a comprehensive suite of active and passive remote sensors, including cloud radar, that sample the atmosphere in a narrow column above its location. Surface radiation, aerosols, and fluxes are also measured and there is an ancillary measurement facility to help quantify local gradients. The AMF is deployed at no cost to the principal investigator or institution for periods from six months to one year on the basis of an international proposal competition judged by a nonpartisan board. The proposal to ARM that led to the initial international deployment of the AMF in Niamey, Niger, was titled ""Radiative Atmospheric Divergence Using the AMF, GERB Data, and AMMA Stations (RADAGAST)."" This paper provides a description of the instruments that compose the AMF, its charter, a description of its deployment in support of RADAGAST, and examples of data that have been collected in Africa. © 2007 American Meteorological Society."
"7404288437;7003543851;","Detection and correction of diurnal sampling bias in HIRS/2 brightness temperatures",2007,"10.1175/JTECH2062.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548632091&doi=10.1175%2fJTECH2062.1&partnerID=40&md5=5b3faced2c46f9d83ea700d283d33a01","Diurnal sampling biases arise in the High-Resolution Infrared Radiation Sounder (HIRS) satellite observations because some of the NOAA polar-orbiting satellites drift significantly from their original local observation time. Such bias adversely affects interpretation of these data for climate studies. Twenty-six years of HIRS/2 radiance satellite data (1979-2004) were examined by creating monthly mean gridded data that categorize the observations by local observing time through averaging ascending and descending orbits separately. Corresponding HIRS/ 2 simulated radiance data from the Geophysical Fluid Dynamics Laboratory (GFDL) climate model were constructed using HIRS/2 satellite sampling and were found to accurately represent the diurnal sampling bias. Correction of the HIRS/2 observations from the observed diurnal sampling bias was using the model simulations of HIRS brightness temperatures to adjust the observed brightness temperatures to the model daily mean. The diurnal bias was found to vary with channel, surface type, latitude, satellite, and cloud cover, but showed little dependence on satellite scan angle. Diurnal bias is most pronounced for ascending orbit observations of the afternoon [1400 local solar time (LST)] satellites with 60°N to 60°S domain averaged brightness temperatures variations up to 0.78 K yr-1. Lower tropospheric temperature and water vapor channels contained the largest bias, and biases over land were more than twice as large as those over the ocean. Brightness temperature adjustments of up to 10 K were needed in the most extreme situations. © 2007 American Meteorological Society."
"57203474131;55542320000;57200540848;7202674824;57215268681;7201837768;35453054300;","Potential impacts of aerosol-land-atmosphere interactions on the Indian monsoonal rainfall characteristics",2007,"10.1007/s11069-006-9085-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72549103102&doi=10.1007%2fs11069-006-9085-y&partnerID=40&md5=4807bdfc640292ffc0f7dc026b018f5e","Aerosols can affect the cloud-radiation feedback and the precipitation over the Indian monsoon region. In this paper, we propose that another pathway by which aerosols can modulate the multi-scale aspect of Indian monsoons is by altering the land-atmosphere interactions. The nonlinear feedbacks due to aerosol/diffuse radiation on coupled interactions over the Indian monsoon region are studied by: (1) reviewing recent field measurements and modeling studies, (2) analyzing the MODIS and AERONET aerosol optical depth datasets, and (3) diagnosing the results from sensitivity experiments using a mesoscale modeling system. The results of this study suggest that the large magnitude of aerosol loading and its impact on land-atmosphere interactions can significantly influence the mesoscale monsoonal characteristics in the Indo-Ganges Basin. © 2007 Springer Science+Business Media, Inc."
"14035706000;55731643300;55145417300;17342843800;12801677100;14035976500;7005712075;","Characteristics of Japanese winter sprites and their parent lightning as estimated by VHF lightning and ELF transients",2007,"10.1016/j.jastp.2007.05.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34447646893&doi=10.1016%2fj.jastp.2007.05.002&partnerID=40&md5=2d01f6323d1936bc4d7f9fd47d59655d","Sprites are newly discovered optical emissions in the mesosphere over large thunderstorms. This paper is the observational summary of winter sprites in the Hokuriku area of Japan and their parent lightning in the winter of 2004/2005, by using the coordinated optical and electromagnetic (VHF and ELF) measurements in Japan. As the results of optical observations at two stations, we have found that this campaign has yielded a variety of sprite shapes; V-angle shaped structures have been often observed (25%) in addition to columnar structures familiar for us. All of the sprite events are found to be associated with +CG lightning, as seen from the macroscopic information by ELF data at Moshiri. However, examining the microscopic properties of parent lightning as seen from the VHF SAFIR lightning detection network, has suggested very complicated characteristics of parent lightning discharges inducing sprites, as compared with the ELF data. One half of the sprite events are also found to be associated with +CG by the SAFIR observation, but another half has yielded rather new results as compared with earlier results. Four events are definitely associated with -CG and the remaining three events, inter-cloud flashes. The overall picture for Japanese winter sprites and their parent lightning discharges, is significantly different from that for the summer-time, continental sprites. This is indicative of complexity of winter lightning in the Hokuriku area of Japan and this would provide new information on the sprite generation mechanism. © 2007 Elsevier Ltd. All rights reserved."
"57196755283;7201888941;","Event-based climatology and typology of fog in the New York City region",2007,"10.1175/JAM2516.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548632253&doi=10.1175%2fJAM2516.1&partnerID=40&md5=c0a08d1f79e1702cce40ab0b683b8fd9","The character of fog in a region centered on New York City, New York, is investigated using 20 yr of historical data. Hourly surface observations are used to identify fog events at 17 locations under the influence of various physiographic features, such as land-water contrasts, land surface character (urban, suburban, and rural), and terrain. Fog events at each location are classified by fog types using an objective algorithm derived after extensive examination of fog formation processes. Events are characterized according to frequency, duration, and intensity. A quantitative assessment of the likelihood with which mechanisms leading to fog formation are occurring in various parts of the region is obtained. The spatial, seasonal, and diurnal variability of fog occurrences are examined and results are related to regional and local influences. The results show that the likelihood of fog occurrence is influenced negatively by the presence of the urban heat island of New York City, whereas it is enhanced at locations under the direct influence of the marine environment. Inland suburban and rural locations also experience a considerable amount of fog. As in other areas throughout the world, the overall fog phenomenon is a superposition of various types. Precipitation fog, which occurs predominantly in winter, is the most common type. Fog resulting from cloud-base lowering also occurs frequently across the region, with an enhanced likelihood in winter and spring. A considerable number of advection fog events occur in coastal areas, mostly during spring, whereas radiation fog occurs predominantly at suburban and rural locations during late summer and early autumn but also occurs during the warm season in the coastal plain of New Jersey as advection-radiation events. © 2007 American Meteorological Society."
"6603839217;7005853435;7003299599;","Maximum entropy production, cloud feedback, and climate change",2007,"10.1029/2007GL029925","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548597135&doi=10.1029%2f2007GL029925&partnerID=40&md5=26a68228513ef7d642af1b192efb1769","A steady-state energy-balance climate model based on a global constraint of maximum entropy production is used to examine cloud feedback and the response of surface temperature T to doubled atmospheric CO2. The constraint ensures that change in zonal cloud amount øo necessarily involves change in the convergence KX of meridional energy flow. Without other feedbacks, the changes in øo, KX and T range from about 2%, 2 Wm-2 and 1.5 K respectively at the equator to -2%, -2 WM-2 and 0.5 K at the poles. Global-average cloud effectively remains unchanged with increasing CO2 and has little effect on global-average temperature. Global-average cloud decreases with increasing water vapour and amplifies the positive feedback of water vapour and lapse rate. The net result is less cloud at all latitudes and a rise in T of the order of 3 K at the equator and 1 K at the poles Ice-albedo and solar absorption feedbacks are not considered. Copynght 2007 by the American Geophysical Union."
"55977336000;16637291100;7201706787;7501855361;","Possible causes of decreasing cloud cover in the Arctic winter, 1982-2000",2007,"10.1029/2007GL030042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548600085&doi=10.1029%2f2007GL030042&partnerID=40&md5=47669058d20e3ca0ca12c56146662f8f","Satellite and reanalysis datasets show a decrease in wintertime (Dec., Jan., Feb.) cloud cover over most of the Arctic Ocean from 1982 to 2000. Concurrently, wintertime moisture convergence has decreased significantly over the Nansen Basin and parts of the Barents and Kara Seas (NBK; 75-90°N, 45-90°E). Over this region, correlation coefficients between monthly anomalies in the satellite-derived cloud cover and moisture convergence in the cold season are large and statistically significant. This reduction in moisture convergence results in a decrease in cloud formation due to weakening cyclone activity over the NBK region. Reduced cloud amount over this area leads to decreased cloud cover over the entire central Arctic because less cloud is advected to other regions. The same mechanism has been observed over northeastern Russia and the Bering Strait area (RBS; 65-75°N, 150-200°E) and is therefore an additional, and perhaps more important, control over cloud cover in the Chukchi/Beaufort Seas and the Laptev Sea region. Copyright 2007 by the American Geophysical Union."
"11141872500;57214957751;7005287667;7401891176;35461763400;","Cloud-nucleating properties of the Amazonian biomass burning aerosol: Cloud condensation nuclei measurements and modeling",2007,"10.1029/2006JD008104","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548780314&doi=10.1029%2f2006JD008104&partnerID=40&md5=238e61af3a0347a82de1e90835eb25ff","The cloud-nucleating properties of the atmospheric aerosol were studied in an area under strong influence of vegetation burning. The measurements were part of Large-Scale Biosphere Atmosphere Experiment in Amazonia-Smoke Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) and were carried out at a ground site located in the state of Rondônia in southwestern Amazonia, Brazil, September to November 2002, covering the dry season, a transition period, and the onset of the wet season. The concentrations of cloud condensation nuclei (CCN) were measured with a static thermal gradient CCN counter for supersaturations ranging between 0.23 and 1.12%. As a closure test, the CCN concentrations were predicted with a time resolution of 10 min from measurements of the dry particle number size distribution (3-850 nm, Differential Mobility Analyzer (DMPS)) and hygroscopic growth at 90% relative humidity (Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA)). No chemical information was needed. The predicted and measured CCN concentrations were highly correlated (r2 = 0.97-0.99), and the predictions were only slightly lower than those measured, typically by 15-20%. Parameterizations of the predicted CCN concentrations are given for each of the three meteorological periods. These are based on averages taken during the afternoon hours when the measurements at ground level were representative for the aerosol entering the base of convective clouds. Furthermore, a more detailed parameterization including the mixing state of the aerosol is given, where the hygroscopic properties are expressed as the number of soluble ions or nondissociating molecules per unit volume dry particle. Copyright 2007 by the American Geophysical Union."
"37013451200;7601490850;7501461145;","Spatiotemporal characteristics of photosynthetically active radiation in China",2007,"10.1029/2006JD007965","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548722176&doi=10.1029%2f2006JD007965&partnerID=40&md5=71775d719fbe528acc1dadab3f2fdc96","Photosynthetically active radiation (PAR) plays an important part in climate change and ecological processes. Few PAR measurements are usually available, especially in China. Thus it is important and significant to investigate the spatiotemporal characteristics of PAR in China for radiation budget and ecosystem studies. In order to study the spatiotemporal characteristics of PAR, photosynthetic photon flux density (Q<inf>p</inf>) and broadband solar radiation (R<inf>s</inf>) measurement data were analyzed for the period of January 2005 to June 2006. Q<inf>p</inf> increases gradually from spring and reaches its maximum and minimum in summer and winter, respectively. The highest value of annual mean daily Q<inf>p</inf> (40.9 ± 4.1 mol m-2 d-1) appears in the Qinghai-Tibet Plateau region along with higher atmospheric transmission; and the lowest value (17.4 ± 9.03 mol m-2 d-1) is found in the northern subtropics, along with the largest aerosol optical depth (AOD) and a lower water vapor content. PAR fraction shows a similar seasonal trend as that of Q<inf>p</inf> at all sites except for some near to lakes and sea. The annual mean daily value of PAR fraction varies from 1.75 ± 0.12 to 2.3 ± 0.15 mol MJ-1 over China. The largest value appears in tropical regions because of higher relative humidity (RH). The lowest value is observed at the Luancheng site, which features low humidity and an abundance of fine aerosols, instead of sites in China's driest northern desert region. The variability of PAR fraction is mainly controlled by the selective scattering of aerosol particles and absorption of water vapor. Two different diurnal trends of PAR fraction are observed in China. In most sites, PAR fraction tends to peak during sunrise or sunset and reaches its lowest value around noon. However, it exhibits an opposite trend in the northern desert area because of the distinctive diurnal variation of water vapor in this region. Further analysis of annual mean hourly PAR fraction shows that the national average is 1.82 ± 0.11 and 2.00 ± 0.08 μmol J-1 for clear and cloudy days, respectively. The cloudy day's ratio is therefore 10% higher than that for clear days. The altitude dependency of PAR fraction is very weak below 1500 m because of uneven distributions of water vapor, clouds, and aerosols. Above 1500 m, PAR fraction increases gradually with altitude on both cloudy and clear days, attributed to the weaker extinction of Q<inf>p</inf> at higher-altitude sites. The distribution pattern of annual mean daily PAR fraction is similar to that of the hourly value. Its magnitude is medial to the hourly values on cloudy and clear days. These results are helpful for understanding the climatic, agricultural, and ecological processes over China and useful for primary productivity estimation and ecosystem - atmosphere CO<inf>2</inf> exchange study in China. Copyright 2007 by the American Geophysical Union."
"16308514000;7004040199;16444215600;7003591311;7006572336;57196499374;","Particulate organic acids and overall water-soluble aerosol composition measurements from the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS)",2007,"10.1029/2007JD008537","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548609954&doi=10.1029%2f2007JD008537&partnerID=40&md5=676d4c4add6bd4c084273c9b9821657d","The Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter participated in the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) mission during August-September 2006. A particle-into-liquid sampler (PILS) coupled to ion chromatography was used to characterize the water-soluble ion composition of aerosol and cloud droplet residual particles (976 5-min PM<inf>1.0</inf> samples in total). Sulfate and ammonium dominated the water-soluble mass (NH<inf>4</inf>+ + SO<inf>4</inf>2 = 84 ± 14%), while organic acids contributed 3.4 ± 3.7%. The average NH<inf>4</inf>+: SO<inf>4</inf>2- molar ratio was 1.77 ± 0.85. Particulate concentrations of organic acids increased with decreasing carbon number from C<inf>9</inf> to C<inf>2</inf>. Organic acids were most abundant above cloud, presumably as a result of aqueous phase chemistry in cloud droplets, followed by subsequent droplet evaporation above cloud tops; the main product of this chemistry was oxalic acid. The evolution of organic acids with increasing altitude in cloud provides evidence for the multistep nature of oxalic acid production; predictions from a cloud parcel model are consistent with the observed oxalate:glyoxylate ratio as a function of altitude in GoMACCS cumuli. Suppressed organic acid formation was observed in clouds with relatively acidic droplets, as determined by high particulate nitrate concentrations (presumably high HNO<inf>3</inf> levels too) and lower liquid water content, as compared to other cloud fields probed. In the Houston Ship Channel region, an area with significant volatile organic compound emissions, oxalate, acetate, formate, benzoate, and pyruvate, in decreasing order, were the most abundant organic acids. Photo-oxidation of m-xylene in laboratory chamber experiments leads to a particulate organic acid product distribution consistent with the Ship Channel area observations. Copyright 2007 by the American Geophysical Union."
"6508287655;7102797196;7005931768;35330367300;21740108200;","Influence of inhomogeneous cloud fields on optical properties retrieved from satellite observations",2007,"10.1029/2006JD007891","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548652326&doi=10.1029%2f2006JD007891&partnerID=40&md5=b9492ecc338acafab98be79c65c54cff","Analyses of solar radiation exchanges between the atmosphere and clouds are vital for the understanding of climate processes and cycles. Comparisons of satellite-to-satellite or satellite-to-ground-truth observations aiming at, elucidating the radiative behavior of atmospheric components (clouds, aerosols, gas, etc.), or validating data of a particular satellite are a common practice in global radiation investigations. In order to assess the quality of cloud optical properties derived from Geostationary Meteorological Satellite-5/ Stretched Visible Infrared Spin Scan Radiometer (GMS-5/SVISSR), the former procedure (satellite-to-satellite comparison) was used. Data derived from GMS-5/SVISSR satellite were compared with those from the polar-orbiting Terra-Moderate Resolution Imaging Spectroradiometer (Terra-MODIS) satellite. This comparison showed serious discrepancies between cloud optical depth (COD) data retrieved from the two satellites' observations. GMS-5/SVISSR-retrieved COD appeared mostly lower than that of Terra-MODIS. To understand the origin of such differences, an identification procedure of the major factors likely to affect these data is conducted. Some of these factors were the satellite viewing and solar conditions, the cloud thermodynamic phase differentiation and particle effective radius, and the cloud inhomogeneity. Then emphasis was put on the examination of the latter effect (i.e., the cloud inhomogeneity). The analysis procedure was as follows: First, data having close-viewing geometries between both satellites were selected and used to understand the effects of the remaining factors. Among these, the cloud thermodynamic phase appeared to play the major role as analyses showed that most of the COD differences between both satellites were confined within ice clouds while warm clouds had the least discrepancies. This would suggest that the choice of a water cloud particle radiative transfer model to analyze a 2-phase cloud radiation data, as used here, may produce large uncertainties in ice COD retrievals from at least one of the satellites. To avoid the cloud phase problem, a more restrictive data set comprising only water clouds (besides close-viewing geometries between both satellites) was selected, and the impact of the degree of cloud inhomogeneity on the COD retrievals was evaluated. The study reveals that the 3-D radiative effects deriving from the external cloud inhomogeneity, i.e., cloud asymmetry and structured sides, were the most influencing properties here. The GMS-5/SVISSR interpretation of inhomogeneous cloud optical properties showed larger uncertainties than that of Terra-MODIS. Furthermore, COD values of GMS-5/SVISSR were systematically lower than those of Terra-MODIS for the pixels at shadow sides of the cloud, while at illuminated sides they often showed higher values. For gentle or near-plane-parallel cloud surfaces, fewer discrepancies were noticed (the best agreement between both satellites' retrievals). At steep slopes of the shadow and illuminated cloud sides, GMS-5/SVISSR average COD data were respectively under- and overestimated compared to those of Terra-MODIS. COD differences between the two satellites could be sometimes higher than 30% for slopes steeper than 0.5 K/km. Copyright 2007 by the American Geophysical Union."
"6506837510;7007108728;7005453346;7410070663;","The sensitivity of the radiation budget in a climate simulation to neglecting the effect of small ice particles",2007,"10.1175/JCLI4191.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547924537&doi=10.1175%2fJCLI4191.1&partnerID=40&md5=306fe46cfd97acf9152dbb0785cd4b13","The sensitivity of the atmospheric radiation budget to ignoring small ice particles (D ≤ 100 μm) in parameterization of the mean effective size of ice particles was investigated by using the Canadian Centre for Climate Modelling and Analysis (CCCma) third-generation general atmospheric circulation model (AGCM3). The results indicate that small ice particles play two crucial roles in the radiative transfer that influence the simulated climate. First, they inhibit the IR radiation from escaping to space and, second, they enhance the scattering of solar radiation. On average, these two effects tend to partially cancel each other out. However, based on AGCM simulations, the small ice crystals make clouds more opaque to IR radiation. Generally, 5-yr seasonally averaged GCM results suggest that the strongest anomalies in outgoing longwave radiation (OLR) are found in the Tropics, reaching 15 to 25 W m-2 in areas where cold high cirrus anvil clouds are prevalent. The global average change in net cloud radiative forcing was 2.4 W m-2 in June-August (JJA) and 1.7 W m-2 in December-February (DJF). The change in globally averaged 5-yr mean cloud forcing was close to 1.9 W m-2. When the small particles were included, the globally averaged 5-yr mean precipitation decreased by about 8%, but cloudiness increased only slightly (by 2%). The 5-yr averaged global mean surface (screen) temperature also increased slightly (about 0.2°C) when the small ice particles were included."
"6701354900;7403044861;6603894240;7004544454;","South Atlantic variability arising from air-sea coupling: Local mechanisms and tropical-subtropical interactions",2007,"10.1175/JCLI4114.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547911485&doi=10.1175%2fJCLI4114.1&partnerID=40&md5=a4db3bf5d43e8038cfff30173c7dec2e","Interannual variability in the southern and equatorial Atlantic is investigated using an atmospheric general circulation model (AGCM) coupled to a slab ocean model (SOM) in the Atlantic in order to isolate features of air-sea interactions particular to this basin. Simulated covariability between sea surface temperatures (SSTs) and atmosphere is very similar to the observed non-ENSO-related covariations in both spatial structures and time scales. The leading simulated empirical coupled mode resembles the zonal mode in the tropical Atlantic, despite the lack of ocean dynamics, and is associated with baroclinic atmospheric anomalies in the Tropics and a Rossby wave train extending to the extratropics, suggesting an atmospheric response to tropical SST forcing. The second non-ENSO mode is the subtropical dipole in the SST with a mainly equivalent barotropic atmospheric anomaly centered on the subtropical high and associated with a midlatitude wave train, consistent with atmospheric forcing of the subtropical SST. The power spectrum of the tropical mode in both simulation and observation is red with two major interannual peaks near 5 and 2 yr. The quasi-biennial component exhibits a progression between the subtropics and the Tropics. It is phase locked to the seasonal cycle and owes its existence to the imbalances between SST-evaporation and SST-shortwave radiation feedbacks. These feedbacks are found to be reversed between the western and eastern South Atlantic, associated with the dominant role of deep convection in the west and that of shallow clouds in the east. A correct representation of tropical-extratropical interactions and of deep and shallow clouds may thus be crucial to the simulation of realistic interannual variability in the southern and tropical Atlantic. © 2007 American Meteorological Society."
"36851768400;57193132723;7501894557;","The tropical atmospheric El Niño signal satellite precipitation data and a global climate model",2007,"10.1175/JCLI4208.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547858578&doi=10.1175%2fJCLI4208.1&partnerID=40&md5=7cb48fa3648de2a412c61db7bd7b1345","Aspects of the tropical atmospheric response to El Niño related to the global energy and water cycle are examined using satellite retrievals from the Tropical Rainfall Measuring Mission and the Advanced Microwave Scanning Radiometer-E and simulations from the Goddard Institute for Space Studies (GISS) general circulation model (GCM). The El Niño signal is extracted from climate fields using a linear cross-correlation technique that captures local and remote in-phase and lagged responses. Passive microwave and radar precipitation anomalies for the 1997/98 and 2002/03 El Niños and the intervening La Niña are highly correlated, but anomalies in stratiform-convective rainfall partitioning in the two datasets are not. The GISS GCM produces too much rainfall in general over ocean and too little over land. Its atmospheric response to El Niño is weaker and decays a season too early. Underestimated stratiform rainfall fraction (SRF) and convective downdraft mass flux in the GISS GCM and excessive shallow convective and low stratiform cloud result in latent heating that peaks at lower altitudes than inferred from the data. The GISS GCM also underestimates the column water vapor content throughout the Tropics, which causes it to overestimate outgoing longwave radiation. The response of both quantities to interannual Hadley circulation anomalies is too weak. The GISS GCM's Walker circulation also exhibits a weak remote response to El Niño, especially over the Maritime Continent and western Indian Ocean. This appears to be a consequence of weak static stability due to the model's lack of upper-level stratiform anvil heating, excessive low-level heating, and excessive dissipation due to cumulus momentum mixing. Our results suggest that parameterizations of mesoscale updrafts, convective downdrafts, and cumulus-scale pressure gradient effects on momentum transport are keys to a reasonable GISS GCM simulation of tropical interannual variability."
"56257070800;36819688200;7103371748;57203259172;","On the consistency in variations of the South China Sea Warm Pool as revealed by three sea surface temperature datasets",2007,"10.1016/j.rse.2006.12.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248678694&doi=10.1016%2fj.rse.2006.12.012&partnerID=40&md5=eb2350b4864523c0e8e99a1c18feb645","The areal and intensity indices of the South China Sea Warm Pool (SCSWP) derived from three datasets, the Advanced Very High Resolution Radiometer (AVHRR), Tropical Rainfall Measuring Mission's Microwave Imager (TMI) and Optimum Interpolation Version 2 (OI.v2) sea surface temperature (SST), are generally consistent with each other at monthly, seasonal and interannual scales. However, the three records are different in some cases. First, minor differences among the monthly records of intensity index are observed in the period July to September. Secondly, the interannual records of SCSWP intensity derived from AVHRR and OI.v2 are different in autumn during the period 1990-1996. The reason is not yet clear and nor is it clear which record best represents fluctuations in SCSWP intensity. These suggest that various drawbacks of the three datasets, such as low resolution of OI.v2, and cloud and rain contamination on AVHRR and TMI data, would be serious enough to allow deviation from each other to appear. Merging AVHRR and TMI SST data might be the way leading to a more convincing time series of SCSWP. In addition, changes of areal and intensity indices are not always consistent with each other, for example, they have different monthly patterns. Although the three interannual records of intensity index in three seasons all capture the main Multivariate ENSO Index (MEI) signals at a half-year lag, only those which are in the summer significantly correlated with MEI. © 2007 Elsevier Inc. All rights reserved."
"55667068400;","Sources, nature and influence on climate of marine airborne particles",2007,"10.1071/EN07001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250851376&doi=10.1071%2fEN07001&partnerID=40&md5=bcf7cf0506abac9f6cd30cbe37517faa","Airborne particles (aerosol) collected at Cape Grim, Tasmania, in February 2006 in baseline conditions were examined by transmission electron microscopy. Particles recognised as marine exopolymer gels, and aggregates of insoluble organic particles that have diameters of ∼40 nm, formed 9% of the particles larger than 200 nm. Once water-soluble compounds were removed by dialysis, the proportion rose to 30%. The gels and exopolymers were mainly of marine algal and bacterial origin. Their highly surface-active properties make them potentially environmentally important in the aerosol because of their ability to act as cloud condensation nuclei. The chemical constitution of particles in the 80?200-nm diameter size range is controversial, and widely varying estimates of the proportion of sea salt they contain have been published. Possible reasons for this are discussed. The present work supports the lowest estimate. © CSIRO 2007."
"16308514000;35264611800;6602832585;7101846027;7003591311;7006572336;57196499374;","On the source of organic acid aerosol layers above clouds",2007,"10.1021/es0630442","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34447266878&doi=10.1021%2fes0630442&partnerID=40&md5=c17d1040049f0113639292cca7aeea94","During the July 2005 Marine Stratus/Stratocumulus Experiment (MASE) and the August-September 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS), the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter probed aerosols and cumulus clouds in the eastern Pacific Ocean off the coast of northern California and in southeastern Texas, respectively. An on-board particle-into-liquid sampler (PILS) quantified inorganic and organic acid species with ≤5-min time resolution. Ubiquitous organic aerosol layers above cloud with enhanced organic acid levels were observed in both locations. The data suggest that aqueous-phase reactions to produce organic acids, mainly oxalic acid, followed by droplet evaporation is a source of elevated organic acid aerosol levels above cloud. Oxalic acid is observed to be produced more efficiently relative to sulfate as the cloud liquid water content increases, corresponding to larger and less acidic droplets. As derived from large eddy simulations of stratocumulus under the conditions of MASE, both Lagrangian trajectory analysis and diurnal cloudtop evolution provide evidence that a significant fraction of the aerosol mass concentration above cloud can be accounted for by evaporated droplet residual particles. Methanesulfonate data suggest that entrainment of free tropospheric aerosol can also be a source of organic acids above boundary layer clouds. © 2007 American Chemical Society."
"27170375100;7005922032;13309700700;7409874856;","Intercomparison of precipitation simulated by regional climate models over East Asia in 1997 and 1998",2007,"10.1007/s00376-007-0539-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38349056804&doi=10.1007%2fs00376-007-0539-2&partnerID=40&md5=2533192a494983045357d85b90d77ad0","Regional climate simulations in Asia from May 1997 to August 1998 were performed using the Seoul National University regional climate model (SNURCM) and Iowa State University regional climate model (ALT.MM5/LSM), which were developed by coupling the NCAR/Land Surface Model (LSM) and the Mesoscale Model (MM5). However, for physical processes of precipitation, the SNURCM used the Grell scheme for the convective parameterization scheme (CPS) and the simple ice scheme for the explicit moisture scheme (EMS), while the ALT.MM5/LSM used the Betts-Miller scheme for CPS and the mixed phase scheme for EMS. The simulated precipitation patterns and amounts over East Asia for the extreme climatic summer in 1997 (relative drought conditions) and 1998 (relative flood conditions) were especially focused upon. The ALT.MM5/ LSM simulated more precipitation than was observed in 1997 due to more moisture and cloud water in the lower levels, despite weak upward motion. In the SNURCM, strong upward motion resulted in more precipitation than that was observed in 1998, with more moisture and cloud water in the middle levels. In the ALT.MM5/LSM, weak upward motion, unchanged moisture in the lower troposphere, and the decrease in latent heat flux at the surface increased convective precipitation only by 3% for the 1998 summer event. In the SNURCM, strong upward motion, the increase in moisture in the lower troposphere, and the increase in latent heat flux at the surface increased convective precipitation by 48% for the summer of 1998. The main differences between both simulations were moisture availability and horizontal momentum transport in the lower troposphere, which were also strongly influenced by large-scale forcing. © Science Press 2007."
"7004978125;","Multiscale model with moisture and systematic strategies for superparameterization",2007,"10.1175/JAS3976.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547729090&doi=10.1175%2fJAS3976.1&partnerID=40&md5=326a82a895e574f82450c44382231459","The accurate parameterization of moist convection presents a major challenge for the accurate prediction of weather and climate through numerical models. Superparameterization is a promising recent alternative strategy for including the effects of moist convection through explicit turbulent fluxes calculated from a cloud-resolving model. Basic scales for cloud-resolving modeling are the microscales on the order of 10 km in space on time scales on the order of 15 min, where vertical and horizontal motions are comparable and moist processes are strongly nonlinear (meso-gamma scale). In this paper, systematic multiscale asymptotic analysis is utilized to develop simplified microscale mesoscale dynamic (MMD) models for interaction between the microscales and spatiotemporal mesoscales on the order of 100 km and 2.5 h (meso-beta scale). The new MMD models lead to a systematic framework for superparameterization for numerical weather prediction (NWP) generalizing the traditional column modeling framework. The MMD formulation also provides a flexible systematic framework for devising new parameterization strategies for NWP intermediate between the two extremes of column modeling and detailed cloud-resolving modeling. It is also established here that these MMD models fit crudely into the recent systematic multiscale framework developed to explain the observed larger-scale statistical self-similarity of tropical convection, and therefore provide a systematic framework for superparameterization. Finally, it is shown that the new MMD models have the structure of a heterogeneous multiscale method so that many numerical techniques recently developed in the applied mathematics literature can be applied to this formulation. © 2007 American Meteorological Society."
"8672586200;55640225400;7202245915;7201527458;","Initialization with diabatic heating from satellite-derived rainfall",2007,"10.1016/j.atmosres.2007.01.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249936934&doi=10.1016%2fj.atmosres.2007.01.001&partnerID=40&md5=d87e5e90dd109fa72ba2a17be9308452","In this paper, a new technique is proposed to improve initialization of a tropical cyclone (TC) prediction model using diabatic heating profiles estimated from a combination of both infrared satellite cloud imagery and satellite-derived rainfall. The method is termed Rainfall-defined Diabatic Heating, RDH. To examine the RDH performance, initialization and forecast experiments are made with the Australia Bureau of Meteorology Research Centre (BMRC) Tropical Cyclone - Limited Area Prediction System (TC-LAPS) for the case of TC Chris, which made landfall on the west coast of Australia during 3-6 Feb 2002. RDH is performed in three steps: 1) based on previous observational and numerical studies, reference diabatic heating profiles are firstly classified into three kinds: convective, stratiform or composite types; 2) NRL (Naval Research Laboratory) 3-hourly gridded satellite rainfall estimates are categorized as one of the three types according to the rain rate; 3) within a nudging phase of 24 h, the model-generated heating at each grid point during the integration is replaced by the reference heating profiles on the basis of the satellite-observed cloud top temperature and rainfall type. The results of sensitivity experiments show that RDH has a positive impact on the model initialization of TC Chris. The heating profiles generated by the model within the observed rainfall area show agreement with that of reference heating. That is, maximum heating is located in the lower troposphere for convective rainfall, and in the upper troposphere for stratiform rainfall. In response to the replaced heating and its impact on the TC structure, the model initial condition and forecasts of the track and intensity are improved. © 2007 Elsevier B.V. All rights reserved."
"7101667328;35497573900;6701431208;57209147261;7103211168;","Why simulating the ITCZ in GCMs is so difficult",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548027052&partnerID=40&md5=36bfdbb5edb10a212198dd1902e046e2","The Intertropical Convergence Zone (ITCZ) in global climate models (GCMs) is highly sensitive to model physics, specifically in cumulus parameterization scheme. In a study where an aqua-planet GCM with a zonally uniform sea surface temperature (SST) and a global-scale Gaussian latitudinal profile together with a pole-to-Equator difference of 29°C was used, the GCM was having difficulty in representing the forcing of the ITCZ of which a double ITCZ error was always occurring when a dotted curve is used. This dilemma is mainly caused by lacked of understanding in model physics, particularly in scheme. In order to remove the ITCZ systematic error, a change in model physics must be considered."
"7003582587;20435098200;12800106700;6507112497;","Modelling suppressed and active convection. Comparing a numerical weather prediction, cloud-resolving and single-column model",2007,"10.1002/qj.109","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548210984&doi=10.1002%2fqj.109&partnerID=40&md5=833cdbb3862f1c52494ea0b373de289d","This paper describes the design of and basic results from a case study to compare simulations of convection over the Tropical West Pacific. Simulations are carried out using a cloud-resolving model (CRM), a global numerical weather prediction (NWP) model and a single-column version of the NWP model (SCM). The experimental design for each model type is discussed and then results are compared. The periods simulated each include a regime with strong convective activity, a much more suppressed regime with far less convection, as well as the transition between these regimes. The description of the design and basic results from this study are given in some detail, as a study including all these model types is relatively new. Comparing the local forcing due to the dynamics in the NWP model with the observed forcing used to drive the CRM and SCM it is found that there is good agreement for one period chosen but significant differences for another. This is also seen in fields such as rain rate and top-of-atmosphere radiation. Using the period with good agreement we are able to identify examples of biases in the NWP model that are also reproduced in the SCM. Also discussed are examples of biases in the NWP simulation that are not reproduced in the SCM. It is suggested that understanding which biases in the SCM are consistent with the full NWP model can help focus the use of an SCM in this framework. © Crown Copyright 2007. Reproduced with the permission of the Controller of HMSO."
"7003637188;6602655859;22939789300;","Conditions for freezing precipitation at some airports of Russia and the CIS: IV. Airport of Nizhni Novgorod",2007,"10.3103/S1068373907070035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35448975686&doi=10.3103%2fS1068373907070035&partnerID=40&md5=4bcac9bcadaaa8edf4e9f4ea0d5449f4","Results of study of conditions for freezing precipitation (FP) at the airport of Nizhni Novgorod based on 20-year series of surface observations are described. The cloud tops are estimated from radiosonde data. It is found that the monthly mean FP frequency does not exceed 0.44%; the phenomenon occurs from October to February. Over 20 years, a total of 113 FP episodes were observed, or less than six episodes annually. Freezing precipitation is more frequent at night and in the morning and very rare in the afternoon, at surface air temperatures not exceeding 0°C and not below -10°C; in half of the cases, the air temperature is within -0.1 to -2.0°C. Surface wind is most frequently from south or southwest, while in the lower 4-km layer, according to the radiosonde data, wind direction mostly veers with height from south to west and north. In the boundary layer, FP is often associated with low-level jet streams, most frequently of southwest direction in the cloudy layers. The warm layers within and below the clouds occur in more than 20% of the cases. The most typical precipitation is FP from ""all cold"" clouds. Using objective criteria of the fronts, synoptic situations, advection, and baroclinicity, it is shown that almost all cases of freezing rain are observed in frontal zones, while freezing drizzle is as frequent at the fronts as under airmass conditions. Both types of FP are associated mainly with high baroclinicity and warm advection. The results can be used to develop an objective method of FP forecasting. © Allerton Press, Inc. 2007."
"57203055233;7202216319;7403263977;7003684963;","Momentum flux spectrum of convectively forced internal gravity waves and its application to gravity wave drag parameterization. Part II: Impacts in a GCM (WACCM)",2007,"10.1175/JAS3954.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547765293&doi=10.1175%2fJAS3954.1&partnerID=40&md5=3cbfe749de8719381d45c932a6da2a08","Impacts of a spectral parameterization of gravity wave drag (GWD) induced by cumulus convection (GWDC) in the NCAR Whole Atmosphere Community Climate Model (WACCM1b) are investigated. In the spectral GWDC parameterization, reference wave momentum flux spectrum is launched at cloud top and analytically calculated based on the physical properties of convection and the large-scale flow. The cloud-top wave momentum flux is strong mainly in the Tropics and midlatitude storm-track regions, and exhibits anisotropy and spatiotemporal variability. The anisotropy and variability are determined by the distributions and variations of convective activities, the moving speed of convection, and horizontal wind and stability in convection regions. Zonal-mean zonal GWDC has a maximum of 13-27 (37-50) m s-1 day-1 in the mesosphere in January (July). Impacts of GWDC on zonal wind appear mainly in the low to midlatitudes of the upper stratosphere and mesosphere. In these regions, biases of zonal wind with respect to observation are reduced more than 50% through the GWDC process. In contrast to zonal wind, impacts of GWDC on temperature occur mainly in the mid- to high latitudes. Through the analysis of forcing terms in the zonal wind and temperature equations, it is found that impacts of GWDC result from interaction among wave forcing terms (resolved wave forcing, parameterized background GWD, and GWDC) and meridional circulations induced by the wave forcing terms. With regard to tropical variability, when GWDC is included, the model produces the stratospheric semiannual oscillation with more realistic amplitude and structure and stronger interannual variabilities in the lower stratosphere. These enhanced variabilities are caused by resolved wave forcing and meridional circulations. © 2007 American Meteorological Society."
"8236726600;7005401705;","Estimation of potential evapotranspiration in the mountainous Panama Canal watershed",2007,"10.1002/hyp.6394","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34447313630&doi=10.1002%2fhyp.6394&partnerID=40&md5=7a9551ad2cf8f1d37d3b9ac22246b9ba","Spatially distributed hydrometeorological and plant information within the mountainous tropical Panama Canal watershed is used to estimate parameters of the Penman-Monteith evapotranspiration formulation. Hydrometeorological data from a few surface climate stations located at low elevations in the watershed are complemented by (a) typical wet- and dry-season fields of temperature, wind, water vapour and pressure produced by a mesoscale atmospheric model with a 3 × 3 km2 spatial and hourly temporal resolution, and (b) leaf area index fields estimated over the watershed during a few years using satellite data with two different spatial and temporal resolutions. The mesoscale model estimates of spatially distributed surface hydrometeorological variables provide the basis for the extrapolation of the surface climate station data to produce input for the Penman-Monteith equation. The satellite information and existing digital spatial databases of land use and land cover form the basis for the estimation of Penman-Monteith spatially distributed parameter values. Spatially distributed 3 × 3 km2 potential evapotranspiration estimates are obtained for the 3300 km2 Panama Canal watershed. Estimates for Gatun Lake within the watershed are found to reproduce well the monthly and annual lake evaporation obtained from submerged pans. Sensitivity analysis results of potential evapotranspiration estimates with respect to cloud cover, dew formation, leaf area index distribution and mesoscale model estimates of surface climate are presented and discussed. The main conclusion is that even the limited spatially distributed hydrometeorological and plant information used in this study contributes significantly toward explaining the substantial spatial variability of potential evapotranspiration in the watershed. These results also allow the determination of key locations within the watershed where additional surface stations may be profitably placed. Copyright © 2006 John Wiley &amp; Sons, Ltd."
"55666517900;6602521281;13105500600;6701777177;6508247200;6602732919;35548761600;","Solar activity imprints in tree ring width from Chile (1610-1991)",2007,"10.1016/j.jastp.2007.03.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249941553&doi=10.1016%2fj.jastp.2007.03.010&partnerID=40&md5=0a5ebe2efa3d91aba737de395c75f87a","We have investigated the solar activity signal in tree ring data from two locations in Chile. The tree ring time series extended over a period of ∼400 yr. Spectral and wavelet analysis techniques were employed. We have found evidence for the presence of the solar activity Schwabe (∼11 yr), Hale (∼22 yr), fourth-harmonic of the 208-yr Suess cycle (∼52 yr) and Gleissberg (∼80 yr) cycles. The Gleissberg cycle of tree ring data is in anti-phase with solar activity. Wavelet and cross-wavelet techniques revealed that the periods found are intermittent, possibly because solar activity signals observed in tree rings are mostly due to solar influence on local climate (rainfall, temperature, and cloud cover) where trees grow up. Further, cross-wavelet analysis between sunspot and tree ring time series showed that the cross power around the 11 yr solar cycle is more significant during periods of high solar activity (grand maximum) than during periods of low solar activity (grand minimum). As Glaciar Pio XI is practically at the Pacific Ocean level, the tree-ring response may be stronger due to the heating of the Pacific Ocean water following an increase of the solar radiation incidence rather than at the higher altitudes of Osorno region. © 2007 Elsevier Ltd. All rights reserved."
"14627622500;35578212100;6701392449;","Precipitation interception in Australian tropical rainforests: II. Altitudinal gradients of cloud interception, stemflow, throughfall and interception",2007,"10.1002/hyp.6346","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34447097737&doi=10.1002%2fhyp.6346&partnerID=40&md5=c0bac31bca66f03c30597e33695bb764","This article presents a comprehensive study of canopy interception in six rainforests in Australia's Wet Tropics for periods ranging between 2 and 3.5 years. Measurements of rainfall, throughfall, stemflow and cloud interception were made at sites characterized by different forest types, canopy structure, altitude, rainfall and exposure to prevailing winds. Throughfall at these sites ranged between 64 and 83% of total precipitation inputs, while stemflow ranged between 2 and 11%. At sites higher than 1000 m, cloud interception was found to contribute up to 66% of the monthly water input to the forest, more than twice the rainfall at these times. Over the entire study period, cloud interception accounted for between 4 and 30% of total precipitation inputs, and was related more to the exposure of sites to prevailing winds than to altitudinal differences alone. Over the duration of the study period, interception losses ranged between 22 and 29% of total water input (rainfall and cloud interception) at all sites except the highest altitude site on Bellenden Ker, where interception was 6% of total water input. This smaller interception loss was the result of extremely high rainfall, prolonged immersion in cloud and a sparser canopy. On a monthly basis, interception losses from the six sites varied between 10 and 88% of rainfall. All sites had much higher interception losses during the dry season than in the wet season because of the differences in storm size and rainfall intensity. The link between rainfall conditions and interception losses has important implications for how evaporative losses from forests may respond to altered rainfall regimes under climate change and/or large-scale atmospheric circulation variations such as El Niño. Copyright © 2007 John Wiley & Sons, Ltd."
"7003908632;6504389831;","Assessment of the dehydration-greenhouse feedback over the Arctic during February 1990",2007,"10.1002/joc.1455","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347218177&doi=10.1002%2fjoc.1455&partnerID=40&md5=a6709bfb6e8861f6a3171458b5856b2a","The effect of pollution-derived sulfuric acid aerosols on the aerosol-cloud-radiation interactions is investigated over the Artic for February 1990. Observations suggest that acidic aerosols can decrease the heterogeneous nucleation rate of ice crystals and lower the homogeneous freezing temperature of haze droplets. On the basis of these observations, we hypothesize that the cloud thermodynamic phase is modified in polluted air mass (Arctic haze). Cloud ice number concentration is reduced, thus promoting further ice crystal growth by the Bergeron-Findeisen process. Hence, ice crystals reach larger sizes and low-levkel ice crystal precipitation from mixed-phase clouds increases. Enhanced dehydration of the lower troposphere contributes to decreased water vapour greenhouse effect and cools the surface. A positive feedback is created between surface cooling and air dehydration, accelerating cold air production. This process is referred to as the dehydration-greenhouse feedback (DGF). Simulations performed using an Arctic regional climate model for February 1990 are used to assess the potential effect of the DGF on the Arctic climate during February. Results show that the DGF has an important effect on cloud, atmospheric dehydration, and temperature over the Central and Eurasian Arctic, which is the coldest part of the Arctic. Cloud ice is significantly reduced and the total atmospheric water path is decreased by as much as 12%. This results in a surface cooling ranging between 0 and -3 K. Moreover, the lower tropospheric cooling over the Eurasian and Central Arctic strengthens the atmospheric circulation at the upper level, thus increasing the aerosol transport from the mid-latitudes and enhancing the DGF. Over warmer areas, the increased aerosol concentration (caused by the DGF) leads to longer cloud lifetime, which contributes to warm these areas. Copyright © 2006 Royal Meteorological Society."
"56093699900;55745955800;8859530100;","A case study of a frontal system simulated by a climate model: Clouds and radiation",2007,"10.1029/2006JD008238","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547780768&doi=10.1029%2f2006JD008238&partnerID=40&md5=78acbd58244de0930ebd34bf1e178102","A case study is carried out to evaluate the capability of the Community Atmosphere Model (CAM3) in simulating frontal clouds over the Southern Great Plains (SGP). It focuses on a midlatitude cyclonic storm system observed during the March 2000 Intensive Observation Period (IOP) of the Atmospheric Radiation Measurement Program (ARM). Cloud biases are found to be consistent with climate model biases in this region: overestimation of optically thick clouds and shortwave cooling at the top-of-the-atmosphere (TOA), underestimation of optically thin middle clouds. Satellite observations, NOAA ETA analysis and a suite of ARM measurements are used to analyze the model cloud biases. We found two independent causes of model errors during two stages of the evolution of the cyclone. In the first stage, the biases are from cloud microphysical properties. The model significantly overpredicted cloud liquid water path, while it underpredicted cloud ice water path. As a result, it overestimated the magnitude of shortwave cloud forcing. In the second stage, the model cloud biases are primarily caused by a faster eastward propagation of the 500 mbar ridge behind the cyclone, which dissipated the high- and middle-level clouds but favored low clouds, leading to biases in cloud forcing. Averaged over the cyclone domain and period, the model simulated shortwave and longwave TOA cloud forcing of -113 W/ m2 and 30 W/m2, respectively, while the corresponding observations are -69 W/m2 and 38 W/m2. Our results illustrated the feasibility of using synoptic cases to understand and eventually eliminate systematic cloud biases in climate models. Copyright 2007 by the American Geophysical Union."
"6507984183;6701378450;57211106013;57196499374;","Cloud condensation nuclei prediction error from application of Köhler theory: Importance for the aerosol indirect effect",2007,"10.1029/2006JD007834","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547819313&doi=10.1029%2f2006JD007834&partnerID=40&md5=c9101f5878240732fb45bf0135a3ec18","In situ observations of aerosol and cloud condensation nuclei (CCN) and the GISS GCM Model II' with an online aerosol simulation and explicit aerosol-cloud interactions are used to quantify the uncertainty in radiative forcing and autoconversion rate from application of Köhler theory. Simulations suggest that application of Köhler theory introduces a 10-20% uncertainty in global average indirect forcing and 2-11% uncertainty in autoconversion. Regionally, the uncertainty in indirect forcing ranges between 10-20%, and 5-50% for autoconversion. These results are insensitive to the range of updraft velocity and water vapor uptake coefficient considered. This study suggests that Köhler theory (as implemented in climate models) is not a significant source of uncertainty for aerosol indirect forcing but can be substantial for assessments of aerosol effects on the hydrological cycle in climatically sensitive regions of the globe. This implies that improvements in the representation of GCM subgrid processes and aerosol size distribution will mostly benefit indirect forcing assessments. Predictions of autoconversion, by nature, will be subject to considerable uncertainty; its reduction may require explicit representation of size-resolved aerosol composition and mixing state. Copyright 2007 by the American Geophysical Union."
"7003824291;7003665942;6507337434;7101700601;56027651900;7003397735;","Simultaneous observation of noctilucent clouds, mesospheric summer echoes, and temperature at a midlatitude station (54°N)",2007,"10.1029/2006JD008135","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547842342&doi=10.1029%2f2006JD008135&partnerID=40&md5=9bf152cc15d1327f1ead28c99743a59f","Between 2003 and 2005, 12.9 h (8 events) of noctilucent clouds (NLC) and 250 h of mesospheric summer echoes (MSE) were observed above Kühlungsborn (54°N, 12°E) by lidar and radar, respectively. The ice-layer seasons typically last for 50 (NLC) and 70 days (MSE). The observations are compared with simultaneous lidar temperature soundings. Altogether, 79 soundings were performed in the periods 10 May to 8 August of each year. These profiles revealed a minimum mesopause temperature of 145 K at 87 km shortly after summer solstice. The mean temperatures are below the frost point temperature for a period of ∼15 days after summer solstice and in the altitude range ∼85-89 km. Simultaneous observations of temperature, MSE/NLC, and winds by radar and lidar show that ice particles occur primarily during southward winds and during the cold phases of gravity waves and tides, providing temperatures up to ∼20 K lower than the mean. Water vapor saturation profiles are calculated from the temperatures and modeled water vapor concentrations, showing that the ice layers occur at the bottom of the supersaturated region. Only about one fifth of all supersaturation events below 85 km in fact yield NLC above our site. Even saturation ratios of 10-100 lasting for at least 4 h do not necessarily lead to the formation of NLC. We conclude that NLC at midlatitudes are strongly coupled to the advection of preexisting ice particles from northern latitudes. If the ice particles have sublimated prior to the observation, they do not form again even in the cold phases of waves. Copyright 2007 by the American Geophysical Union."
"7201897043;","A sensitivity study of the coupled simulation of the Northeast Brazil rainfall variability",2007,"10.1029/2006JD008093","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548088458&doi=10.1029%2f2006JD008093&partnerID=40&md5=3a5bf1aa1c4ccd5da946e1b33374e6fd","Two long-term coupled ocean-land-atmosphere simulations with slightly different parameterization of the diagnostic shallow inversion clouds in the atmospheric general circulation model (AGCM) of the Center for Ocean-Land-Atmosphere Studies (COLA) coupled climate model are compared for their annual cycle and interannual variability of the northeast Brazil (NEB) rainfall variability. It is seen that the solar insolation affected by the changes to the shallow inversion clouds results in large scale changes to the gradients of the SST and the surface pressure. The latter in turn modulates the surface convergence and the associated Atlantic ITCZ precipitation and the NEB annual rainfall variability. In contrast, the differences in the NEB interannual rainfall variability between the two coupled simulations is attributed to their different remote ENSO forcing. Copyright 2007 by the American Geophysical Union."
"55710671300;7003904922;","Production of space charge at the boundaries of layer clouds",2007,"10.1029/2006JD007998","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548094946&doi=10.1029%2f2006JD007998&partnerID=40&md5=7a33485234657c62b0f4b2bc260c59ac","The ionosphere-Earth current density J<inf>z</inf> creates space charge at the upper and lower boundaries of layer clouds. This occurs because clouds have an order of magnitude lower conductivity than the clear air at the same altitude, and as the current density flows through the boundaries, it creates a gradient of electric field that must be satisfied by the accumulation of space charge, according to Gauss's law. We have modeled the production of space charge and its partition between charges on droplets, aerosol particles, and ions and performed sensitivity tests for the variation of a number of relevant atmospheric parameters. We find typical droplet charges of 50-100 elementary charges, positive at cloud top and negative at cloud base, consistent with recent observations. The charges are of sufficient magnitude to suggest measurable electrical effects on scavenging of ice-forming nuclei and cloud condensation nuclei. The results are relevant to the modeling of solar or internally forced changes of J<inf>z</inf> and space charge on cloud microphysics as a possible cause of small effects on weather and climate. Copyright 2007 by the American Geophysical Union."
"7006246996;6701333444;","Expected magnitude of the aerosol shortwave indirect effect in springtime Arctic liquid water clouds",2007,"10.1029/2006GL028750","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547977997&doi=10.1029%2f2006GL028750&partnerID=40&md5=6094606db0a82a5803f4af7fff1bfb0f","Radiative transfer simulations are used to assess the expected magnitude of the diurnally-averaged shortwave aerosol first indirect effect in Arctic liquid water clouds, in the context of recently discovered longwave surface heating of order 3 to 8 W m-2 by this same aerosol effect detected at the Barrow, Alaska, ARM Site. We find that during March and April, shortwave surface cooling by the first indirect effect is comparable in magnitude to the longwave surface heating. During May and June, the shortwave surface cooling exceeds the longwave heating. Due to multiple reflection of photons between the snow or sea ice surface and cloud base, the shortwave first indirect effect may be easier to detect in surface radiation measurements than from space. Copyright 2007 by the American Geophysical Union."
"19638935200;57203053317;7801611677;35461255500;","An investigation into the aerosol dispersion effect through the activation process in marine stratus clouds",2007,"10.1029/2006JD007401","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548094128&doi=10.1029%2f2006JD007401&partnerID=40&md5=a40918dacadf6e1238b46eb9c92516c4","The aerosol dispersion effect (the influence of an increasing number of aerosol particles on the width of the cloud droplet size distribution) has been observed in maritime clouds [e.g., Liu and Daum, 2002]. Climate model simulations show that the dispersion effect at least partially compensates the first indirect aerosol effect. The application of observational data from maritime stratus/stratocumulus clouds into an adiabatic parcel model allows to analyze the role of the aerosol activation process for the dispersion effect in order to better understand the microphysical mechanism of the dispersion effect in the early stage of cloud formation. When the total aerosol number concentration is increased, the parcel model simulations show that the higher number of aerosol particles at cloud base reduces the supersaturation, which results in a slower particle growth rate, and thus more cloud droplets remain small. This extends the droplet spectra toward the smaller size end and increases the spectral width. The broadening effect partially offsets the reduction of droplet radius because of an enhanced number of aerosol particles, leading to a positive aerosol dispersion effect. Sensitivity studies show that the dispersion effect decreases for increasing updraft velocities. When the updraft velocity approaches 55 cm s-1, the dispersion effect almost vanishes for maritime stratus clouds. Aerosols composed of sulfate or of less soluble organics increase the dispersion effect as compared to sea-salt aerosols, whereas condensation of gaseous nitric acid on aerosols decreases the dispersion effect in marine stratus clouds. Copyright 2007 by the American Geophysical Union."
"7006461882;18934960400;","Lightning activity analysis with respect to the SPCZ location",2007,"10.1029/2007GL029730","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547993337&doi=10.1029%2f2007GL029730&partnerID=40&md5=cf2ddb3dfeb27879dde87748d63d6021","The South Pacific Convergence Zone (SPCZ) stretches over the West Pacific warm pool Southeastward to French Polynesia. The Island Climate Update monthly publishes the mean location deduced from the total rainfall. On the other hand, the World Wide Lightning Location Network monthly provides data from which the lightning activity distribution in the 0°-30° South latitude and 150°-240° West longitude area can be drawn. Scanning this rectangle from West to East allows the spots of maximum lightning activity to be located versus the longitude. Fitting the location of these maxima with a polynomial function leads to a curve comparable with the monthly mean position of the SPCZ, showing that this band of cloudiness is one of the main sources of lightning in this whole area. Copyright 2007 by the American Geophysical Union."
"15845961900;7004490499;7005112315;15846888800;","Characteristics of the double intertropical convergence zone over the tropical Indian Ocean",2007,"10.1029/2006JD007950","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548105748&doi=10.1029%2f2006JD007950&partnerID=40&md5=7e2beda96b2d06b01d3e54b6581e3391","Investigations on the double intertropical convergence zone (DITCZ) over the Indian Ocean using the monthly mean surface wind divergence data obtained from scatterometers on board the ERS-1/2 and QuikSCAT satellites (1991-2005) and the monthly mean cloud amount obtained from the International Satellite Cloud Climatology Project (1988-1989, 1998-2005) and the Advanced Very High Resolution Radiometer (AVHRR) data (1996-2003) reveal that its frequency of occurrence is considerably larger than that reported earlier, though the DITCZ feature in this region is rather diffused compared to Pacific. The 14-year analysis of monthly mean surface wind divergence shows that DITCZ structure is clearly discernible in April (frequency of occurrence, f = 64%), November (f = 73%) and December (f = 60%) in the 50-85°E longitude band over the tropical Indian Ocean. Though less frequent, DITCZ occur during other months also, except the Asian summer monsoon season. Most preferred latitudes of the north and south bands of DITCZ are ∼6°N and ∼7°S, respectively, during November and December. The DITCZ structure is well manifested in the cloud amount also during November and December, while it is less prominent in April. A weak but clearly identifiable hemispherical asymmetry is observed in latitude of occurrence and amplitude of the DITCZ bands. Since the sea surface temperature (SST) at the equatorial region over the Indian Ocean is nearly uniform, the DITCZ appears to be generated mainly by the atniospheric dynamics. This provides a unique opportunity to investigate the structure of ITCZ created by the atmospheric dynamics alone, which is one of the important problems in ITCZ dynamics. Copyright 2007 by the American Geophysical Union."
"7201463831;56113721000;6602136577;7005477332;7003621869;7007127402;","Aerosol source plume physical characteristics from space-based multiangle imaging",2007,"10.1029/2006JD007647","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548083824&doi=10.1029%2f2006JD007647&partnerID=40&md5=6ab65d442ad6a343a4e955d31a9ff0b0","Models that assess aerosol effects on regional air quality and global climate parameterize aerosol sources in terms of amount, type, and injection height. The multiangle imaging spectroradiometer (MISR) aboard NASA's Terra satellite retrieves total column aerosol optical thickness (AOT), and aerosol type over cloud-free land and water. A stereo-matching algorithm automatically retrieves reflecting-layer altitude wherever clouds or aerosol plumes have discernable spatial contrast, with about 500-m accuracy, at 1.1-km horizontal resolution. Near-source biomass burning smoke, volcanic effluent, and desert dust plumes are observed routinely, providing information about aerosol amount, particle type, and injection height useful for modeling applications. Compared to background aerosols, the plumes sampled have higher AOT, contain particles having expected differences in Angstrom exponent, size, single-scattering albedo, and for volcanic plume and dust cloud cases, particle shape. As basic thermodynamics predicts, thin aerosol plumes lifted only by regional winds or less intense heat sources are confined to the boundary layer. However, when sources have sufficient buoyancy, the representative plumes studied tend to concentrate within discrete, high-elevation layers of local stability; the aerosol is not uniformly distributed up to a peak altitude, as is sometimes assumed in modeling. MISR-derived plume heights, along with meteorological profile data from other sources, make it possible to relate radiant energy flux observed by the moderate resolution imaging spectroradiometer (MODIS), also aboard the Terra spacecraft, to convective heat flux that plays a major role in buoyant plume dynamics. A MISR climatology of plume behavior based on these results is being developed. Copyright 2007 by the American Geophysical Union."
"23502460300;55709034700;7005231450;6506961436;6602177985;","A near-global, 2-hourly data set of atmospheric precipitable water from ground-based GPS measurements",2007,"10.1029/2006JD007529","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548061332&doi=10.1029%2f2006JD007529&partnerID=40&md5=955ab8992a363b3ac7a8f70869179877","A 2-hourly data set of atmospheric precipitable water (PW) has been produced from the zenith path delay (ZPD) derived from ground-based Global Positioning System (GPS) measurements. The PW data are available every 2 hours from 80 to 268 International GNSS Service (IGS, formally International GPS Service) ground stations from 1997 to 2004. The accuracy of the IGS ZPD product is roughly 4 mm. An analysis technique is developed to convert ZPD to PW on a global scale. Special efforts are made on deriving surface pressure (P<inf>s</inf>) and water-vapor-weighted atmospheric mean temperature (T<inf>m</inf>), which are two key parameters for converting ZPD to PW. P<inf>s</inf> is derived from global, 3-hourly surface synoptic observations with temporal, vertical and horizontal adjustments. T<inf>m</inf> is calculated from NCEP/NCAR reanalysis with temporal, vertical and horizontal interpolations. The derived P<inf>s</inf> and T<inf>m</inf> at the GPS location and height have root-mean-square (rms) errors of 1.65 hPa and 1.3 K, respectively. A theoretical error analysis concludes that typical PW error associated with the errors in ZPD, T<inf>m</inf> and P<inf>s</inf> is on the order of 1.5 mm. The PW data set is compared with radiosonde, microwave radiometer (MWR) and satellite data. The GPS and radiosonde PW comparisons at 98 stations around the globe show a mean difference of 1.08 mm (drier for radiosonde data) with a standard deviation of differences of 2.68 mm, which corresponds to mean percentage difference and standard deviation of 5.5% and 10.6%, respectively. The bias is primarily due to known dry biases in the Vaisala radiosonde data. The RMS difference between GPS and radiosonde /MWR data ranges from 1.2 mm to 2.83 mm. The latitudinal and seasonal variations of PW derived from the GPS data agree well with that from International Satellite Cloud Climatology Project (ISCCP) data if the ISCCP data are sampled only at grid boxes containing GPS stations. The large difference between GPS and ISCCP data in the subtropics is interesting, but is not easily explained. The comparisons did not reveal any systematic bias in GPS PW data and show that a RMS difference of less than 3 mm between GPS-derived PW and other data sets is achieved. The comparison study also illustrates the value of GPS-estimated PW for examining the quality of other data sets, such as those from radiosondes and MWR. Preliminary analysis of this data set shows interesting and significant diurnal variations in PW in four different regions. Copyright 2007 by the American Geophysical Union."
"24330746000;7003270177;6507569269;","The urban heat island in Salamanca (Spain) and its relationship to meteorological parameters",2007,"10.3354/cr034039","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44349185421&doi=10.3354%2fcr034039&partnerID=40&md5=f9c467d93ec2ae78af8b8816da34ab83","An urban heat island (UHI) was found to exist in Salamanca, Spain - a medium-sized European city that has a continental climate and relatively little industrial pollution. We demonstrate that urban heating can occur in cities with these characteristics, giving rise to a microclimate that may alter the biological rhythm of the zone e.g. under these conditions, spring arrives earlier in the urban zone then in the rural zone. The study was carried out using data from 2 recording stations (one in and the other outside the city) for the years 1996-1998. The existence of a nocturnal UHI was observed, with a highest annual mean value of 3.6°C and a lowest annual mean value (cool island) of -0.9°C. The most intense nocturnal UHI was seen in autumn, while the strongest sinks occurred in spring and summer. As in other types of city with different characteristics, the UHI was seen to vary according to the atmospheric situation. The meteorological variables that most affected the UHI were found to be: (1) wind, which at speeds of &gt;∼6 m s-1 prevented the development of UHIs; (2) cloudiness, which altered the flux of incident solar radiation (the intensity of the nocturnal UHI was greater with high clouds); and (3) atmospheric pressure, which characterised the days of atmospheric stability or instability, leading to variations in the intensity of the UHI. © Inter-Research 2007."
"7007114756;7102128820;7006146719;6506416572;8946494600;23017945100;7102410621;6701819092;8957645200;7201462545;6602137606;22835065400;6508104909;7006577245;6507679962;6701754792;7003972559;8701353900;7003406400;6701530981;16178501600;6603341831;7410084319;6603028621;","Cloudnet: Continuous evaluation of cloud profiles in seven operational models using ground-based observations",2007,"10.1175/BAMS-88-6-883","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548040817&doi=10.1175%2fBAMS-88-6-883&partnerID=40&md5=44451c3acaf7822601a185772ff3a162","The Cloudnet project aims to provide a systematic evaluation of clouds in forecast and climate models by comparing the model output with continuous ground-based observations of the vertical profiles of cloud properties. In the models, the properties of clouds are simplified and expressed in terms of the fraction of the model grid box, which is filled with cloud, together with the liquid and ice water content of the clouds. These models must get the clouds right if they are to correctly represent both their radiative properties and their key role in the production of precipitation, but there are few observations of the vertical profiles of the cloud properties that show whether or not they are successful. Cloud profiles derived from cloud radars, ceilometers, and dual-frequency microwave radiometers operated at three sites in France, Netherlands, and the United Kingdom for several years have been compared with the clouds in seven European models. The advantage of this continuous appraisal is that the feedback on how new versions of models are performing is provided in quasi-real time, as opposed to the much longer time scale needed for in-depth analysis of complex field studies. Here, two occasions are identified when the introduction of new versions of the ECMWF and Météo-France models leads to an immediate improvement in the representation of the clouds and also provides statistics on the performance of the seven models. The Cloudnet analysis scheme is currently being expanded to include sites outside Europe and further operational forecasting and climate models. © 2007 American Meteorological Society."
"35917252100;7005814217;7005513582;","Diagnosing cloud feedbacks in general circulation models",2007,"10.1175/JCLI4140.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250821102&doi=10.1175%2fJCLI4140.1&partnerID=40&md5=7145d4601e7f1733477a3f09328448d2","In this study, it is shown that the NCAR and GFDL GCMs exhibit a marked difference in climate sensitivity of clouds and radiative fluxes in response to doubled CO2 and ±2-K SST perturbations. The GFDL model predicted a substantial decrease in cloud amount and an increase in cloud condensate in the warmer climate, but produced a much weaker change in net cloud radiative forcing (CRF) than the NCAR model. Using a multiple linear regression (MLR) method, the full-sky radiative flux change at the top of the atmosphere was successfully decomposed into individual components associated with the clear sky and different types of clouds. The authors specifically examined the cloud feedbacks due to the cloud amount and cloud condensate changes involving low, mid-, and high clouds between 60°S and 60°N. It was found that the NCAR and GFDL models predicted the same sign of individual longwave and shortwave feedbacks resulting from the change in cloud amount and cloud condensate for all three types of clouds (low, mid, and high) despite the different cloud and radiation schemes used in the models. However, since the individual longwave and shortwave feedbacks resulting from the change in cloud amount and cloud condensate generally have the opposite signs, the net cloud feedback is a subtle residual of all. Strong cancellations between individual cloud feedbacks may result in a weak net cloud feedback. This result is consistent with the findings of the previous studies, which used different approaches to diagnose cloud feedbacks. This study indicates that the proposed MLR approach provides an easy way to efficiently expose the similarity and discrepancy of individual cloud feedback processes between GCMs, which are hidden in the total cloud feedback measured by CRF. Most importantly, this method has the potential to be applied to satellite measurements. Thus, it may serve as a reliable and efficient method to investigate cloud feedback mechanisms on short-term scales by comparing simulations with available observations which may provide a useful way to identify the cause for the wide spread of cloud feedbacks in GCMs. © 2007 American Meteorological Society."
"55739684700;7004504559;7006198308;","Dimethylsulphide, clouds, and phytoplankton: Insights from a simple plankton ecosystem feedback model",2007,"10.1029/2006GB002812","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548210997&doi=10.1029%2f2006GB002812&partnerID=40&md5=c3cb3919a5e43bbe956023a71859de7a","The hypothesis that marine plankton ecosystems may effectively regulate climate by the production of dimethylsulphide (DMS) has attracted substantial research effort over recent years. This hypothesis suggests that DMS produced by marine ecosystems can affect cloud properties and hence the averaged irradiance experienced by the phytoplankton that produce DMS's precursor dimethylsulphoniopropionate (DMSP). This paper describes the use of a simple model to examine the effects of such a biogenic feedback on the ecosystem that initiates it. We compare the responses to perturbation of a simple marine nitrogen-phytoplankton-zooplankton (NPZ) ecosystem model with and without biogenic feedback. Our analysis of this heuristic model reveals that the addition of the feedback can increase the model's resilience to perturbation and hence stabilize the model ecosystem. This result suggests the hypothesis that DMS may play a role in stabilizing marine plankton ecosystem dynamics through its effect on the atmosphere. Copyright 2007 by the American Geophysical Union."
"34568038900;7405763496;","Improvements in the subgrid-scale representation of moist convection in a cumulus parameterization scheme: The single-column test and its impact on seasonal prediction",2007,"10.1175/MWR3397.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34447327207&doi=10.1175%2fMWR3397.1&partnerID=40&md5=4b46cca1bddb640684b8e46eeac50c8f","This study describes a revised approach for the subgrid-scale convective properties of a moist convection scheme in a global model and evaluates its effects on a simulated model climate. The subgrid-scale convective processes tested in this study comprise three components: 1) the random selection of cloud top, 2) the inclusion of convective momentum transport, and 3) a revised large-scale destabilization effect considering synoptic-scale forcing in the cumulus convection scheme of the National Centers for Environmental Prediction medium-range forecast model. Each component in the scheme has been evaluated within a single-column model (SCM) framework forced by the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment data. The impact of the changes in the scheme on seasonal predictions has been examined for the boreal summers of 1996, 1997, and 1999. In the SCM simulations, an experiment that includes all the modifications reproduces the typical convective heating and drying feature. The simulated surface rainfall is in good agreement with the observed precipitation. Random selection of the cloud top effectively moistens and cools the upper troposphere, and it induces drying and warming below the cloud-top level due to the cloud-radiation feedback. However, the two other components in the revised scheme do not play a significant role in the SCM simulations. On the other hand, the role of each modification component in the scheme is significant in the ensemble seasonal simulations. The random selection process of the cloud top preferentially plays an important role in the adjustment of the thermodynamic profile in a manner similar to that in the SCM framework. The inclusion of convective momentum transport in the scheme weakens the meridional circulation. The revised large-scale destabilization process plays an important role in the modulation of the meridional circulation when this process is combined with other processes; on the other hand, this process does not induce significant changes in large-scale fields by itself. Consequently, the experiment that involves all the modifications shows a significant improvement in the seasonal precipitation, thereby highlighting the importance of nonlinear interaction between the physical processes in the model and the simulated climate. © 2007 American Meteorological Society."
"57210518852;6602665711;6603875926;7202923875;6602963031;7003922138;7406514318;7201485519;","Estimating shortwave radiative forcing and response in climate models",2007,"10.1175/JCLI4143.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250157338&doi=10.1175%2fJCLI4143.1&partnerID=40&md5=98d5f220f525a48e5533c69a4929e50b","Feedback analysis in climate models commonly involves decomposing any change in the system's energy balance into radiative forcing terms due to prescribed changes, and response terms due to the radiative effects of changes in model variables such as temperature, water vapor, clouds, sea ice, and snow. The established ""partial radiative perturbation"" (PRP) method allows an accurate separation of these terms, but requires processing large volumes of model output with an offline version of the model's radiation code. Here, we propose an ""approximate PRP (APRP) method for the shortwave that provides an accurate estimate of the radiative perturbation, but derived from a quite modest amount of monthly mean model output. The APRP method is based on a simplified sho rtwave radiative model of the atmosphere, where surface absorption and atmospheric scattering and absorption are represented by means of three parameters that are diagnosed for overcast and clear-sky portions of each model grid cell. The accuracy of the method is gauged relative to full PRP calculations in two experiments: one in which carbon dioxide concentration is doubled and another in which conditions of the Last Glacial Maximum (LGM) are simulated. The approximate PRP method yields a shortwave cloud feedback accurate in the global mean to within 7%. Forcings and feedbacks due to surface albedo and noncloud atmospheric constituents are also well approximated with errors of order 5%-10%. Comparison of two different model simulations of the LGM shows that the regional and global differences in their ice sheet albedo forcing fields are clearly captured by the APRP method. Hence this method is an efficient and satisfactory tool for studying and intercomparing shortwave forcing and feedbacks in climate models. © 2007 American Meteorological Society."
"9249605700;","A sensitivity of squall-line intensity to environmental static stability under various shear and moisture conditions",2007,"10.1016/j.atmosres.2006.10.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248402064&doi=10.1016%2fj.atmosres.2006.10.001&partnerID=40&md5=eec6a2ac4113eb15e63012122fc67c04","Squall lines develop in various climate regions having diverse environmental profiles of wind shear, moisture, and temperature. In order to explore the sensitivity of squall lines to these environmental profiles, we have performed an extensive set of numerical simulations under various shear and moisture conditions in midlatitude-continental and tropical-oceanic temperature environments. From the results of the sensitivity simulations and the analyses of the environmental parameters, it is found that the static stability in a convectively unstable layer is of primary importance in determining the strength of squall lines. Under temperature environments having the same static stability, convective available potential energy (CAPE) and precipitable water content (PWC) well describe the squall-line intensity. Vertical shear also plays an important role in determining the squall-line structure as well as the intensity through the interaction with surface cold pool. The combination of the static stability in a convectively unstable layer, CAPE, and PWC should be examined in diagnosing the intensity of squall lines that develop with an optimal shear for their environment. © 2006 Elsevier B.V. All rights reserved."
"6602364115;7006417494;7201504886;","Impact mechanisms of shallow cumulus convection on tropical climate dynamics",2007,"10.1175/JCLI4079.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250887499&doi=10.1175%2fJCLI4079.1&partnerID=40&md5=d28b816bdefd2ed5539ed3e29d4a7922","Subtropical shallow cumulus convection is shown to play an important role in tropical climate dynamics, in which convective mixing between the atmospheric boundary layer and the free troposphere initiates a chain of large-scale feedbacks. It is found that the presence of shallow convection in the subtropics helps set the width and intensity of oceanic ITCZs, a mechanism here termed the shallow cumulus humidity throttle because of the control exerted on the moisture supply to the deep convection zones. These conclusions are reached after investigations based on a tropical climate model of intermediate complexity, with sufficient vertical degrees of freedom to capture (i) the effects of shallow convection on the boundary layer moisture budget and (ii) the dependency of deep convection on the free-tropospheric humidity. An explicit shallow cumulus mixing time scale in this simple parameterization is varied to assess sensitivity, with moist static energy budget analysis aiding to identify how the local effect of shallow convection is balanced globally. A reduction in the mixing efficiency of shallow convection leads to a more humid atmospheric mixed layer, and less surface evaporation, with a drier free troposphere outside of the convecting zones. Advection of drier free-tropospheric air from the subtropics by transients such as dry intrusions, as well as by mean inflow, causes a substantial narrowing of the convection zones by inhibition of deep convection at their margins. In the tropical mean, the reduction of convection by this narrowing more than compensates for the reduction in surface evaporation. Balance is established via a substantial decrease in tropospheric temperatures throughout the Tropics, associated with the reduction in convective heating. The temperature response - and associated radiative contribution to the net flux into the column - have broad spatial scales, while the reduction of surface evaporation is concentrated outside of the convecting zones. This results in differential net flux across the convecting zone, in a sense that acts to destabilize those areas that do convect. This results in stronger large-scale convergence and more intense convection within a narrower area. Finally, mixed layer ocean experiments show that in a coupled ocean-atmosphere system this indirect feedback mechanism can lead to SST differences up to +2 K between cases with different shallow cumulus mixing time, tending to counteract the direct radiative impact of low subtropical clouds on SST. © 2007 American Meteorological Society."
"7403681584;7404211378;7005030996;","Evolution of model systematic errors in the tropical atlantic basin from coupled climate hindcasts",2007,"10.1007/s00382-006-0223-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247578012&doi=10.1007%2fs00382-006-0223-8&partnerID=40&md5=1ea66642c928a3dd1c5780f20367040e","Significant systematic errors in the tropical Atlantic Ocean are common in state-of-the-art coupled ocean-atmosphere general circulation models. In this study, a set of ensemble hindcasts from the NCEP coupled forecast system (CFS) is used to examine the initial growth of the coupled model bias. These CFS hindcasts are 9-month integrations starting from perturbed real-time oceanic and atmospheric analyses for 1981-2003. The large number of integrations from a variety of initial states covering all months provides a good opportunity to examine how the model systematic errors grow. The monthly climatologies of ensemble hindcasts from various initial months are compared with both observed and analyzed oceanic and atmospheric datasets. Our analyses show that two error patterns are dominant in the hindcasts. One is the warming of the sea surface temperature (SST) in the southeastern tropical Atlantic Ocean. This error grows faster in boreal summer and fall and peaks in November-December at round 2°C in the open ocean. It is caused by an excessive model surface shortwave radiative flux in this region, especially from boreal summer to fall. The excessive radiative forcing is in turn caused by the CFS inability to reproduce the observed amount of low cloud cover in the southeastern ocean and its seasonal increase. According to a comparison between the seasonal climatologies from the CFS hindcasts and a long-term simulation of the atmospheric model forced with observed SST, the CFS low cloud and radiation errors are inherent to its atmospheric component. On the other hand, the SST error in CFS is a major cause of the model's southward bias of the intertropical convergence zone (ITCZ) in boreal winter and spring. An analysis of the SST errors of the 6-month ensemble hindcasts by seven coupled models in the Development of a European Multimodel Ensemble System for Seasonal-to-Interannual Prediction project shows that this SST error pattern is common in coupled climate hindcasts. The second error pattern is an excessive deepening of the model thermocline depth to the north of the equator from the western coast toward the central ocean. This error grows fastest in boreal summer. It is forced by an overly strong local anticyclonic surface wind stress curl and is in turn related to the weakened northeast trade winds in summer and fall. The thermocline error in the northwest delays the annual shoaling of the equatorial thermocline in the Gulf of Guinea remotely through the equatorial waveguide. © Springer-Verlag 2007."
"57213020763;7003478309;7006128738;6701884630;","Clear-sky aerosol radiative forcing effects based on multi-site AERONET observations over Europe",2007,"10.1007/s00703-006-0212-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34447095845&doi=10.1007%2fs00703-006-0212-9&partnerID=40&md5=0ca75dfa83d8b5b9fee256716ebdedc4","One of the great unknowns in climate research is the contribution of aerosols to climate forcing and climate perturbation. In this study, retrievals from AERONET are used to estimate the direct clear-sky aerosol top-of-atmosphere and surface radiative forcing effects for 12 multi-site observing stations in Europe. The radiative transfer code sdisort in the libRadtran environment is applied to accomplish these estimations. Most of the calculations in this study rely on observations which have been made for the years 1999, 2000, and 2001. Some stations do have observations dating back to the year of 1995. The calculations rely on a pre-compiled aerosol optical properties database for Europe. Aerosol radiative forcing effects are calculated with monthly mean aerosol optical properties retrievals and calculations are presented for three different surface albedo scenarios. Two of the surface albedo scenarios are generic by nature bare soil and green vegetation and the third relies on the ISCCP (International Satellite Cloud Climatology Project) data product. The ISCCP database has also been used to obtain clear-sky weighting fractions over AERONET stations. The AERONET stations cover the area 0° to 30° E and 42° to 52° N. AERONET retrievals are column integrated and this study does not make any seperation between the contribution of natural and anthropogenic components. For the 12 AERONET stations, median clear-sky top-of-atmosphere aerosol radiative forcing effect values for different surface albedo scenarios are calculated to be in the range of - 4 to - 2 W/m2. High median radiative forcing effect values of about - 6 W/m2 were found to occur mainly in the summer months while lower values of about - 1 W/m2 occur in the winter months. The aerosol surface forcing also increases in summer months and can reach values of - 8 W/m2. Individual stations often have much higher values by a factor of 2. The median top-of-atmosphere aerosol radiative forcing effect efficiency is estimated to be about - 25 W/ m2 and their respective surface efficiency is around - 35 W/m2. The fractional absorption coefficient is estimated to be 1.7, but deviates significantly from station to station. In addition, it is found that the well known peak of the aerosol radiative forcing effect at a solar zenith angle of about 75° is in fact the average of the peaks occurring at shorter and longer wavelengths. According to estimations for Central Europe, based on mean aerosol optical properties retrievals from 12 stations, the critical threshold of the aerosol single scattering albedo, between cooling and heating in the presence of an aerosol layer, is close between 0.6 and 0.76. © Springer-Verlag 2006."
"8247122100;57202301596;7005170782;7202474186;7202801743;","What maintains the SST front north of the Eastern Pacific equatorial cold tongue?",2007,"10.1175/JCLI4173.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247611362&doi=10.1175%2fJCLI4173.1&partnerID=40&md5=c841b5d0e50226d63e1730f84680e1c8","A coupled ocean-atmosphere regional model suggests a mechanism for formation of a sharp sea surface temperature (SST) front north of the equator in the eastern Pacific Ocean in boreal summer and fall. Meridional convergence of Ekman transport at 5°N is forced by eastward turning of the southeasterly cross-equatorial wind, but the SST front forms considerably south of the maximum Ekman convergence. Geostrophic equatorward flow at 3°N in the lower half of the isothermally mixed layer enhances mixed layer convergence. Cold water is upwelled on or so uth of the equator and is advected poleward by mean mixed layer flow and by eddies. The mixed layer current convergence in the north confines the cold advection, so the SST front stays close to the equator. Warm advection from the north and cold advection from the south strengthen the front. In the Southern Hemisphere, a continuous southwestward current advects cold water far from the upwelling core. The cold tongue is warmed by the net surface f lux, which is dominated by solar radiation. Evaporation and net surface cooling are at a maximum just north of the SST front where relatively cool dry air is advected northward over warm SST. The surface heat flux is decomposed into a response to SST alone, and an atmospheric feedback. The atmospheric feedback enhances cooling on the north side of the front by 178 W m-2, about half of which is due to enhanced evaporation from cold dry advection, while the other half is due to cloud radiative forcing. © 2007 American Meteorological Society."
"19338121600;7102870914;","Role of SST over the Indian Ocean in influencing the intraseasonal variability of the Indian summer monsoon",2007,"10.2151/jmsj.85.349","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548029986&doi=10.2151%2fjmsj.85.349&partnerID=40&md5=094c9c38f943680c2dedd04825dbd69f","Intraseasonal variability (10-60 days) of sea surface temperature (SST) over the north Indian Ocean and its influence on regional precipitation variability over the Indian subcontinent are examined. SST, cloud liquid water and precipitation over the Indian Ocean of the Tropical Rainfall Measuring Mission (TRMM), precipitation of Climate Prediction Center Merged Analysis of Precipitation (CMAP), and low-level atmospheric parameters of National Center for Environmental Prediction (NCEP) II reanalysis are utilized for this study. Western Ghats (WG) in the southwest and the Ganges-Mahanadi Basin (GB) in the northeast of the Indian subcontinent are observed to be the regions of maximum precipitation with large standard deviations of the intraseasonal variability. Active (break) phases of precipitation occur in these regions by the northward propagation of positive (negative) precipitation anomalies over the Arabian Sea and the Bay of Bengal. Latitude-time plots during the active phase of the WG region shows that the positive SST anomalies over the Arabian Sea formed by suppressed surface latent heat flux and increased downward shortwave radiation flux lead the positive precipitation anomalies. Surface air temperature anomalies follow the SST anomalies and then destabilize the lower atmosphere between 1000 hPa and 700 hPa. These results indicate that, in the northward propagating dynamical surface convergence, underlying SST anomalies tend to form a favorable condition for convective activity and may sustain enhanced precipitation over the convergence region. This results in enhanced precipitation anomalies over the WG region that move further northeastward and merge with the northward propagating precipitation anomalies from the Bay of Bengal, enhancing the active phase of the GB region. © 2007, Meteorological Society of Japan."
"7003762096;","An analysis of winter temperature and dew point under the canopy of a common Sonoran Desert nurse and the implications for positive plant interactions",2007,"10.1016/j.jaridenv.2006.11.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947236271&doi=10.1016%2fj.jaridenv.2006.11.003&partnerID=40&md5=77dc2d11aa49453eccc2ee43e2b1d3be","Many studies have focused on positive-plant interactions such as nurse plants, which provide a sheltered subcanopy environment that benefits the nursed species. Most of these studies have focused on plant distribution and association patterns, while the microclimatic benefits are often assumed. This study quantifies 5 a.m. subcanopy temperatures as well as dew points beneath a common nurse tree of the Sonoran Desert, Cercidium microphyllum (palo verde, Fabaceae). Data are collected over 35 days in the winter (January and February) at six locations (at the base of the trunk, midway to the canopy edge, canopy edge, all to the north and to the south of the base of the tree) under each of two trees, as well as a control in the open. It is warmer beneath the tree than in the open, but also, it is warmer in the interior than at the canopy edge, and warmer to the south. Furthermore, differences in temperature between the subcanopy and the open site are greater on colder nights, and less pronounced on warmer winter nights, possibly due to the effect of cloud cover which often results in warmer overnight lows. In addition, variation in 5 a.m. temperature is greatest at the canopy edge and open, and temperature varies less in the interior where temperatures are also warmer. Subcanopy cover was quantified using fish-eye imagery. Results show that there is a significant relationship between 5 a.m. temperature and overlying cover. Dew point temperatures, surprisingly, were lower under the tree than at the canopy edge and in the open. That is, it is relatively dry under the nurse. This pattern can similarly be seen by distance and direction from the base of the tree (drier in the south). This may have to do with the nurse's roots and other vegetation growing beneath the nurse's canopy that compete for water in the ground, which leaves less available water to evaporate into the subcanopy air. © 2006 Elsevier Ltd. All rights reserved."
"8644382200;8644381800;8644381700;12759440600;6507291204;6603935310;","Fairweather atmospheric electricity at Antarctica during local summer as observed from Indian station, Maitri",2007,"10.1007/s12040-007-0018-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36349007086&doi=10.1007%2fs12040-007-0018-2&partnerID=40&md5=b18494ab18e76616ba5383ea46c8bed0","Surface measurements of the atmospheric electrical parameters like Maxwell current, electric field and conductivity studied at the Indian station, Maitri (70.75° S, 11.75° E, 117 m above mean sea level), Antarctica, during austral summer have been analyzed for the years 2001 to 2004. A total of 69 days were selected which satisfied the 'fairweather' conditions, i.e., days with absence of high winds, drifting or falling snow, clouds, and fog effects. The diurnal variation curve of electric field and vertical current averaged for 69 fairweather days is a single periodic with a minimum at 03:00 UT and a maximum near 19:00 UT, which is very similar to the Carnegie curve. The correlation coefficient between these measured parameters has a high value (more than 0.9) for all the days. During fairweather days the measured current and field variations are similar and hence it is clear that the conductivity is more or less stable. During magnetically disturbed days, the dawn-dusk potential drop has clear influences on the diurnal variation and it modifies the conductivity. Apart from the day-to-day variation in low latitude thunderstorm activity, there are diurnal, seasonal, inter-annual variations in the electric potential and the currents, as well as solar influences on the measured parameters. This study will help us to examine the impact of solar and geophysical phenomena like solar flares, geomagnetic storms and substorms on the global electric circuit."
"15319594400;56250448700;35993315500;35263296300;55703069400;6506643140;57207433434;7201414259;6507663029;34972083800;7004499182;55205637400;57203365974;19337390700;7004507076;6507141306;19338016300;","The JRA-25 reanalysis",2007,"10.2151/jmsj.85.369","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548030679&doi=10.2151%2fjmsj.85.369&partnerID=40&md5=100ed67c0dda11a8e73c09fea833405b","A long-term global atmospheric reanalysis, named ""Japanese 25-year Reanalysis (JRA-25)"" was completed using the Japan Meteorological Agency (JMA) numerical assimilation and forecast system. The analysis covers the period from 1979 to 2004. This is the first long-term reanalysis undertaken in Asia. JMA's latest numerical assimilation system, and specially collected observational data, were used to generate a consistent and high-quality reanalysis dataset designed for climate research and operational monitoring and forecasts. One of the many purposes of JRA-25 is to enhance the analysis to a high quality in the Asian region. Six-hourly data assimilation cycles were performed, producing 6-hourly atmospheric analysis and forecast fields of various physical variables. The global model used in JRA-25 has a spectral resolution of T106 (equivalent to a horizontal grid size of around 120 km) and 40 vertical layers with the top level at 0.4 hPa. In addition to conventional surface and upper air observations, atmospheric motion vector (AMV) wind retrieved from geostationary satellites, brightness temperature from TIROS Operational Vertical Sounder (TOVS), precipitable water retrieved from orbital satellite microwave radiometer radiance and other satellite data are assimilated with three-dimensional variational method (3D-Var). JMA produced daily sea surface temperature (SST), sea ice and three-dimensional ozone profiles for JRA-25. A new quality control method for TOVS data was developed and applied in advance. Many advantages have been found in the JRA-25 reanalysis. Predicted 6-hour global total precipitation distribution and amount are well reproduced both in space and time. The performance of the long time series of the global precipitation is the best among the other reanalyses, with few unrealistic variations from degraded satellite data contaminated by volcanic eruptions. Secondly, JRA-25 is the first re-analysis to assimilate wind profiles around tropical cyclones reconstructed from historical best track information; tropical cyclones were analyzed properly in all the global regions. Additionally, low-level cloud along the subtropical western coast of continents is well simulated and snow depth analysis is also of a good quality. The article also covers material which requires attention when using JRA-25. © 2007, Meteorological Society of Japan."
"8601841600;6506202087;7005060124;","On the reliability of simulated Arctic sea ice on global climate models",2007,"10.1029/2007GL029914","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34447507643&doi=10.1029%2f2007GL029914&partnerID=40&md5=2332e996dc97acb47a14d263879a2c7e","While most of the global climate models (GCMs) currently being evaluated for the IPCC Fourth Assessment Report simulate present-day Arctic sea ice in reasonably good agreement with observations, the intermodel differences in simulated Arctic cloud cover are large and produce significant differences in downwelling longwave radiation. Using the standard thermodynamic models of sea ice, we find that the GCM-generated spread in longwave radiation produces equilibrium ice thicknesses that range from 1 to more than 10 meters. However, equilibrium ice thickness is an extremely sensitive function of the ice albedo, allowing errors in simulated cloud cover to be compensated by tuning of the ice albedo. This analysis suggests that the results of current GCMs cannot be relied upon at face value for credible predictions of future Arctic sea ice. Copyright 2007 by the American Geophysical Union."
"7103246957;","Coupling of water vapor convergence, clouds, precipitation, and land-surface processes",2007,"10.1029/2006JD008191","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547596224&doi=10.1029%2f2006JD008191&partnerID=40&md5=69687f3243d2ad4bb1009cc5ca5f2681","On daily timescales, the climate over land is a complex balance of many coupled processes. ERA40 reanalysis data for subbasins of the Mississippi in summer are used to explore the links between these processes in a fully coupled model system, and observed surface precipitation and surface short-wave fluxes derived by the International Satellite Cloud Climatology Project are used for evaluation. This paper proposes that the effective cloud albedo viewed from the surface is a useful link which connects the cloud fields to both surface and large-scale processes. The reanalysis has a low bias in cloud albedo in all seasons except summer. In the coupled system in the warm season, on daily timescales, the lifting condensation level falls as soil moisture and precipitation increase. The ratio of the cloud short-wave radiative forcing at the surface to the diabatic precipitation heating of the atmosphere is less in the reanalysis than in the observations. The surface energy budget is split into the surface net radiation and the evaporative fraction. The surface cloud radiative forcing largely determines the surface net radiation, while evaporative fraction, with fixed vegetation, is largely determined by temperature and near-surface soil moisture. Copyright 2007 by the American Geophysical Union."
"56373027800;15032788000;7006107059;","Evaluation of the aerosol indirect effect using satellite, tracer transport model, and aircraft data from the International Consortium for Atmospheric Research on Transport and Transformation",2007,"10.1029/2006JD007581","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547609628&doi=10.1029%2f2006JD007581&partnerID=40&md5=34eeff62ac10acdcbdd9a646cb8c74ed","The magnitudes of the ""indirect effects"" that anthropogenic aerosols have on clouds and climate remain uncertain. Past space-based characterizations have compared satellite retrievals of cloud properties with satellite- or model-derived aerosol quantities. The two fields have been taken from air masses displaced from each other either horizontally or vertically. Thus, almost by definition, the cloud retrievals have come from different meteorological regimes than the aerosol to which ostensibly they are related. Because cloud properties depend foremost on meteorology, the difference introduces undesired ambiguity in the comparisons. In this study, we compare Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) cloud retrievals with high spatial and temporal resolution output from a tracer transport model (FLEXPART), enabling colocation of fields of pollution and clouds both vertically and horizontally. Anthropogenic carbon monoxide (CO) is used as a passive pollution tracer, because its concentrations are tied to mixing and pollutant source strength, and they are independent of atmospheric oxidation and removal processes on timescales of weeks to months. Cloud and pollution fields are compared along a downwind axis from the U.S. northeastern seaboard for the duration of the summer 2004 International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) mission. Where the transport model indicates air as being polluted, cloud r<inf>e</inf> is smaller and cloud optical depth is in some cases higher, at least close to primary source regions. However, within 4 ± 1 days advection time from the northeastern seaboard, cloud perturbations become negligible, probably because of wet-scavenging of CCN. No conclusive evidence was found for any perturbation to cloud liquid water path by pollution. Copyright 2007 by the American Geophysical Union."
"56298802300;6701915334;6701832491;23034217100;35548900300;55915601800;56031450100;","Sensitivities and uncertainties in a coupled regional atmosphere-ocean-ice model with respect to the simulation of Arctic sea ice",2007,"10.1029/2006JD007814","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547593080&doi=10.1029%2f2006JD007814&partnerID=40&md5=fe1dd90daf3eeac47f8b3c4cb3b4d979","A series of sensitivity experiments using a coupled regional atmosphere-ocean-ice model of the Arctic has been conducted in order to identify the requirements needed to reproduce observed sea-ice conditions and to address uncertainties in the description of Arctic processes. The ability of the coupled model to reproduce observed summer ice retreat depends largely on a quasi-realistic ice volume at the beginning of the melting period, determined by the relationship between winter growth and summer decay of ice. While summer ice decay is strongly affected by the parameterization of the sea-ice albedo, winter ice growth depends significantly on the parameterization of lateral freezing. Reciprocal model biases due to uncertainties in the atmospheric energy fluxes can be compensated to a certain extent. However, potential underlying weaknesses of the model cannot be eliminated that way. Since lateral freezing also determines the ice concentration during winter, and thus the heat loss of the ocean and the near-surface air temperature, the model tuning possibilities are limited. A large uncertainty in the model relates to the simulation of long-wave radiation most likely as a result of overestimated cloud cover. The results suggest that uncertainties in the descriptions for Arctic clouds, snow, and sea-ice albedo, and lateral freezing and melting of sea ice, including the treatment of snow, are responsible for large deviations in the simulation of Arctic sea ice in coupled models. Improved descriptions of these processes are needed to reduce model biases and to enhance the credibility of future climate change projections. Copyright 2007 by the American Geophysical Union."
"6506257058;6602738250;6701348241;6602576807;9233141200;8667844900;55502835800;56253852700;","Intercomparison of SCIAMACHY nitrogen dioxide observations, in situ measurements and air quality modeling results over Western Europe",2007,"10.1029/2006JD007277","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547606514&doi=10.1029%2f2006JD007277&partnerID=40&md5=3561e055d251a29a59e2c65d345516ac","The Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) satellite spectrometer provides detailed information on the nitrogen dioxide (NO<inf>2</inf>) content in the planetary boundary layer. NO<inf>2</inf> tropospheric column retrievals of SCIAMACHY and its predecessor Global Ozone Monitoring Experiment are characterized by errors of the order of 40%. We present here a new SCIAMACHY tropospheric retrieval data set for the year 2003. The cloud free satellite observations are compared to surface measurements and simulations over western Europe performed with the regional air-quality model CHIMERE. The model has a resolution of 50 km similar to the satellite observations. For these comparisons, averaging kernels are applied to the collocated model profiles to remove the dependency of the comparison on a priori NO<inf>2</inf> profile information used in the retrieval. The consistency of both SCIAMACHY and CHIMERE outputs over sites where surface measurements are available allows us to be confident in evaluation of the model over large areas not covered by surface observations. CHIMERE underestimates surface NO<inf>2</inf> concentrations for urban and suburban stations which we mainly attribute to the low representativeness of point observations. No such bias is found for rural locations. The yearly average SCIAMACHY and CHIMERE spatial NO<inf>2</inf> distributions show a high degree of quantitative agreement over rural and urban sites: a bias of 5% (relative to the retrievals) and a correlation coefficient of 0.87 (n = 2003). On a seasonal basis, biases are smaller than 20% and correlation coefficients are larger than 0.75. Spatial correlations between both the model and satellite columns and the European Monitoring and Evaluation Program (EMEP) emission inventory are high in summer (r = 0.74, n = 1779) and low in winter (r = 0.48, n = 1078), related to seasonal changes in lifetime and transport. On the other hand, CHIMERE and SCIAMACHY columns are mutually consistent in summer (r = 0.82) and in winter (r = 0.79). This shows that CHIMERE simulates the transport and chemical processes with a reasonable accuracy. The NO<inf>2</inf> columns show a high daily variability. The daily NO<inf>2</inf> pollution plumes observed by SCIAMACHY are often well described by CHIMERE both in extent and in location. This result demonstrates the capabilities of a satellite instrument such as SCIAMACHY to monitor the NO<inf>2</inf> concentrations over large areas on a daily basis. It provides evidence that present and future satellite missions, in combination with CTM and surface data, will contribute to improve quantitative air quality analyses at a continental scale. Copyright 2007 by the American Geophysical Union."
"6603431534;6603422104;35473805400;","Cloud climatology at the Southern Great Plains and the layer structure, drizzle, and atmospheric modes of continental stratus",2007,"10.1029/2006JD007307","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347347294&doi=10.1029%2f2006JD007307&partnerID=40&md5=63b9a8aa9a8889dc7b9d936814f53d97","Long-term (6.5 years) cloud observations from the Atmospheric Radiation Measurements (ARM) program Southern Great Plains (SGP) climate research facility in Oklahoma are used to develop detailed cloud climatology. Clouds are classified with respect to their altitude (low, middle, and high), vertical development, and the presence of multilayer clouds. Single-layered cirrus, middle or low clouds were observed a total of 23% of the time the MilliMeter Cloud Radar (MMCR) was operating, and multilayer clouds were observed 20.5% of the time. Boundary layer clouds exhibit the strongest seasonal variability because of continental stratus associated with midlatitude frontal systems. Cirrus clouds are the most frequently observed cloud type and exhibit strong seasonal variability in cloud base height (higher cloud base during the summer months) and relatively constant cloud fraction. The majority of middle-level clouds are shallow with vertical extent less than 1 km. No strong seasonal cycle in the fractional coverage of multilayer clouds is observed. Continental stratus clouds exhibit strong seasonal variability with maximum occurrence during the cold seasons. Nondrizzling stratus clouds exhibit a bimodal seasonal variability with maximum occurrences in the fall and spring, while drizzling stratus occur most frequently in the winter. Thermodynamic and dynamic variables from soundings and the European Centre for Medium-Range Weather Forecasts Model (ECMWF) analyses at the SGP site illustrate an interesting coupling between strong large-scale forcing and the formation of single-layered (no other cloud layer is present) continental stratus clouds. Single-layered stratus clouds (drizzling and nondrizzling exhibit a strong correlation with positive ω at 500 mbar and strong northerly flow. Copyright 2007 by the American Geophysical Union."
"6603809220;7401711350;7006577693;7005853435;7404544551;57208462871;57210717445;55654938600;7102604282;7003663632;56162305900;","Have Australian rainfall and cloudiness increased due to the remote effects of Asian anthropogenic aerosols?",2007,"10.1029/2006JD007712","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347344079&doi=10.1029%2f2006JD007712&partnerID=40&md5=a40be7b477420cead127ace71f66af2d","There is ample evidence that anthropogenic aerosols have important effects on climate in the Northern Hemisphere but little such evidence in the Southern Hemisphere. Observations of Australian rainfall and cloudiness since 1950 show increases over much of the continent. We show that including anthropogenic aerosol changes in 20th century simulations of a global climate model gives increasing rainfall and cloudiness over Australia during 1951-1996, whereas omitting this forcing gives decreasing rainfall and cloudiness. The pattern of increasing rainfall when aerosols are included is strongest over northwestern Australia, in agreement with the observed trends. The strong impact of aerosols is primarily due to the massive Asian aerosol haze, as confirmed by a sensitivity test in which only Asian anthropogenic aerosols are included. The Asian haze alters the meridional temperature and pressure gradients over the tropical Indian Ocean, thereby increasing the tendency of monsoonal winds to flow toward Australia. Anthropogenic aerosols also make the simulated pattern of surface-temperature change in the tropical Pacific more like La Niña, since they induce a cooling of the surface waters in the extratropical North Pacific, which are then transported to the tropical eastern Pacific via the deep ocean. Transient climate model simulations forced only by increased greenhouse gases have generally not reproduced the observed rainfall increase over northwestern and central Australia. Our results suggest that a possible reason for this failure was the omission of forcing by Asian aerosols. Further research is essential to more accurately quantify the role of Asian aerosols in forcing Australian climate change. Copyright 2007 by the American Geophysical Union."
"11940701600;","Geographical and seasonal distribution of tropical tropopause thin clouds and their relation to deep convection and water vapor viewed from satellite measurements",2007,"10.1029/2006JD007479","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347366432&doi=10.1029%2f2006JD007479&partnerID=40&md5=289e1a2a7ac6641874447e4b2a4f4455","The climatologies of deep convection, thin clouds, and water vapor measurements from four independent satellites are compared in this study. Deep convection reaching the tropical tropopause layer (TTL) is indicated by the area of the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) 20 dBZ reflectivity reaching 14 km and the area of the TRMM visible and infrared scanner (VIRS) brightness temperature at 10.8 μm (T<inf>B11</inf>) < 210 K. TTL clouds are identified by 17 years of Stratospheric Aerosol and Gas Experiment (SAGE) II measurements and by 1 year of Earth Observing System (EOS) Microwave Limb Sounder (MLS) ice water content in 2005. TTL water vapor is estimated from 2005 EOS MLS retrievals. Results suggest that TTL clouds are geographically and seasonally correlated with deep convection as inferred from the area of T<inf>B11</inf>) < 210 K. Patterns of regional differences of seasonal variations of deep convection are also related to the regional differences of seasonal variations of TTL clouds. By grouping the Ice Cloud and Land Elevation Satellite /Geoscience Laser Altimeter System (ICESat/GLAS) layer cloud products, we find that there is a general spatial correlation between the largest, thickest TTL layer clouds with the highest optical depth and the regions with the most intense deep convection. MLS CO and water vapor at 146 hPa have similar geographical and seasonal variations as deep convection and TTL clouds. EOS MLS 100 hPa water vapor is low over the west Pacific Ocean at the same location and time as more TTL clouds are observed. Copyright 2007 by the American Geophysical Union."
"7003341226;7003673986;","Realizing envisat's potential for rain cloud studies",2007,"10.1029/2006GL028996","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347215441&doi=10.1029%2f2006GL028996&partnerID=40&md5=6402cfa6b6a089f7be119176ef3148df","Owing to the highly variable nature of rain both in space and time and the difficulties in obtaining accurate in situ measurements, increasing reliance is being placed on the various types of satellite data now available. The multi-sensor payload of Envisat is of particular interest because the data are co-located and simultaneous, thus reducing some of the uncertainty found in multi-platform analyses. This paper shows variations in cloud and precipitation data derived from AATSR, RA-2 and MWR-2 measurements in an overpass of Hurricane Juan, revealing significant asymmetry in the spatial distribution. The results are discussed in the context of similar data from other tropical and sub-tropical features in the western Atlantic. The combination of data from these sensors allows us to see the effects of different drop-size distribution at varying distances from the hurricane's eye and to conclude that active microwave system are needed for studying small-scale variations in rainfall. Copyright 2007 by the American Geophysical Union."
"7006747671;15724399600;7402469637;6603327182;7003450096;6603054887;7003726515;6602969645;","Origin and transport of tropical cirrus clouds observed over Paramaribo, Suriname (5.8°N, 55.2°W)",2007,"10.1029/2005JD006420","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347359805&doi=10.1029%2f2005JD006420&partnerID=40&md5=85bc5edd93d1ad421d2ce034833bed90","The Intertropical Convergence Zone (ITCZ) passes twice a year over tropical Suriname, bringing two wet and two dry seasons. During a pilot study campaign in Suriname, cirrus clouds were observed with a mobile aerosol Raman lidar (MARL) and with balloon sondes containing a frost point hygrometer called Snow White, over the period October-November 2004. These observations are used to study the origin of cirrus clouds and the dynamical processes that determine their transport, using European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses. The height of cirrus occurrence is in phase with the height of the cold point tropopause, with maximum heights occurring during Northern Hemisphere winter that are about 2 km above the minimum values in summertime. The occurrence of cirrus often corresponds with a northerly meridional wind flow (in a layer underneath the tropopause), also when the ITCZ lies to the south in the period January-May. ECMWF analyses point out that inertial instability flow, in the form of vertically stacked meridional circulation cells in the upper troposphere (UT), can explain the transport of these cirrus events. Also evident is that radiative cooling of a moist layer transported in the UT leads to a thermal wind in the form of an easterly/westerly jet associated with the southward/northward transport of moist air. An interactive play between the inertial instability and thermal wind mechanisms explains many of the observed features of cirrus occurrence over Suriname. The observed cirrus mostly originates from the ITCZ or from deep convective centers to the south that form during the early summer monsoon. Copyright 2007 by the American Geophysical Union."
"7006508549;7202181543;57192695511;7005135473;7101688723;7201914101;35453054300;","Observational estimates of radiative forcing due to land use change in southwest Australia",2007,"10.1029/2006JD007505","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347363221&doi=10.1029%2f2006JD007505&partnerID=40&md5=df3dadcf6af220010c7b8ebf8982cf23","Radiative forcing associated with land use change is largely derived from global circulation models (GCM), and the accuracy of these estimates depends on the robustness of the vegetation characterization used in the GCMs. In this study, we use observations from the Clouds and Earth's Radiant Energy System (CERES) instrument on board the Terra satellite to report top-of-the-atmosphere (TOA) radiative forcing values associated with clearing of native vegetation for agricultural purposes in southwest Australia. Over agricultural areas, observations show consistently higher shortwave fluxes at the TOA compared to native vegetation, especially during the time period between harvest and planting. Estimates using CERES observations show that over a specific area originally covered by native vegetation, replacement of half the area by croplands results in a diurnally averaged shortwave radiative forcing of approximately -7 W m-2. GCM-derived estimates for areas with 30% or more croplands range from - 1 to - 2 W m-2 compared to observational estimate of -4.2 W m-2, thus significantly underestimating radiative forcing due to land use change by a factor of 2 or more. Two potential reasons for this underestimation are incorrect specification of the multiyear land use change scenario and the inaccurate prescription of seasonal cycles of crops in GCMs. Copyright 2007 by the American Geophysical Union."
"26427916400;7102290666;","Relationships between marine stratus cloud optical depth and temperature: Inferences from AVHRR observations",2007,"10.1175/JCLI4115.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250638556&doi=10.1175%2fJCLI4115.1&partnerID=40&md5=32cbfc56cf23844c7e8846c4f5715e22","Studies using International Satellite Cloud Climatology Project (ISCCP) data have reported decreases in cloud optical depth with increasing temperature, thereby suggesting a positive feedback in cloud optical depth as climate warms. The negative cloud optical depth and temperature relationships are questioned because ISCCP employs threshold assumptions to identify cloudy pixels that have included partly cloudy pixels. This study applies the spatial coherence technique to one month of Advanced Very High Resolution Radiometer (AVHRR) data over the Pacific Ocean to differentiate overcast pixels from the partly cloudy pixels and to reexamine the cloud optical depth-temperature relationships. For low-level marine stratus clouds studied here, retrievals from partly cloudy pixels showed 30%-50% smaller optical depths, 1°-4°C higher cloud temperatures, and slightly larger droplet effective radii, when they were compared to retrievals from the overcast pixels. Despite these biases, retrievals for the overcast and partly cloudy pixels show similar negative cloud optical depth-temperature relationships and their magnitudes agree with the ISCCP results for the midlatitude and subtropical regions. There were slightly negative droplet effective radius-temperature relationships, and considerable positive cloud liquid water content-temperature relationships indicated by aircraft measurements. However, cloud thickness decreases appear to be the main reason why cloud optical depth decreases with increasing temperature. Overall, cloud thickness thinning may explain why similar negative cloud optical depth-temperature relationships are found in both overcast and partly cloudy pixels. In addition, comparing the cloud-top temperature to the air temperature at 740 hPa indicates that cloud-top height generally rises with warming. This suggests that the cloud thinning is mainly due to the ascending of cloud base. The results presented in this study are confined to the midlatitude and subtropical Pacific and may not be applicable to the Tropics or other regions. © 2007 American Meteorological Society."
"10045957500;57214310900;10043822500;","The influence of land surface changes on regional climate in Northwest China",2007,"10.1007/s00376-007-0527-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249684228&doi=10.1007%2fs00376-007-0527-6&partnerID=40&md5=bb7d1a9d211553e1d105a309b1ee53dd","Land surface changes effect the regional climate due to the complex coupling of land-atmosphere interactions. From 1995 to 2000, a decrease in the vegetation density and an increase in ground-level thermodynamic activity has been documented by multiple data sources in Northwest China, including meteorological, reanalysis from European Centre for Medium-Range Weather Forecasts (ECMWF), National Oceanic and Atmospheric Administration's (NOAA) Advanced Very High Resolution Radiometer (AVHRR) and TIROS Operational Vertical Sounder (TOVS) satellite remote sensing data. As the ground-level thermodynamic activity increases, humid air from the surrounding regions converge toward desert (and semi-desert) regions, causing areas with high vegetation cover to become gradually more arid. Furthermore, land surface changes in Northwest China are responsible for a decrease in total cloud cover, a decline in the fraction of low and middle clouds, an increase in high cloud cover (due to thermodynamic activity) and other regional climatic adaptations. It is proposed that, beginning in 1995, these cloud cover changes contributed to a ""green-house"" effect, leading to the rapid air temperature increases and other regional climate impacts that have been observed over Northwest China."
"55462312300;7201496259;7005728145;","Influence of dust composition on cloud droplet formation",2007,"10.1016/j.atmosenv.2006.12.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947411714&doi=10.1016%2fj.atmosenv.2006.12.008&partnerID=40&md5=106121217c0ea92b8a7f8666729a2094","Previous studies suggest that interactions between dust particles and clouds are significant; yet the conditions where dust particles can serve as cloud condensation nuclei (CCN) are uncertain. Since major dust components are insoluble, the CCN activity of dust strongly depends on the presence of minor components. However, many minor components measured in dust particles are overlooked in cloud modeling studies. Some of these compounds are believed to be products of heterogeneous reactions involving carbonates. In this study, we calculate Kohler curves (modified for slightly soluble substances) for dust particles containing small amounts of K+, Mg2+, or Ca2+ compounds to estimate the conditions where reacted and unreacted dust can activate. We also use an adiabatic parcel model to evaluate the influence of dust particles on cloud properties via water competition. Based on their bulk solubilities, K+ compounds, MgSO4·7H2O, Mg(NO3)2·6H2O, and Ca(NO3)2·4H2O are classified as highly soluble substances, which enable activation of fine dust. Slightly soluble gypsum and MgSO3·6H2O, which may form via heterogeneous reactions involving carbonates, enable activation of particles with diameters between about 0.6 and 2 μm under some conditions. Dust particles&gt;2 μm often activate regardless of their composition. Only under very specialized conditions does the addition of a dust distribution into a rising parcel containing fine (NH4)2SO4 particles significantly reduce the total number of activated particles via water competition. Effects of dust on cloud saturation and droplet number via water competition are generally smaller than those reported previously for sea salt. Large numbers of fine dust CCN can significantly enhance the number of activated particles under certain conditions. Improved representations of dust mineralogy and reactions in global aerosol models could improve predictions of the effects of aerosol on climate. © 2007 Elsevier Ltd. All rights reserved."
"6602334551;6603227422;","Human climates of Egypt",2007,"10.1002/joc.1434","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248169214&doi=10.1002%2fjoc.1434&partnerID=40&md5=040ba3967f9bbe7c3c19fe7892ad24e5","The clo index values for different wear have been estimated for daytime and nighttime for different months of the year in order to investigate human climates in Egypt. The clo values may also be used as a good guide to gauge the thermal human comfort under different atmospheric conditions and also express the resistance to heat transfer by clothing, and are expressed relative to the units of thermal insulation. A complete set of measurements for air temperature and cloud amount in addition to wind speed for the daytime (1200 GMT) and nighttime (0000 GMT) hours for the period 1991-2002 at 40 meteorological stations in Egypt have been used. The percentage area (%) requiring different weather wear during daytime and nighttime for all the months of the year have been determined. The study revealed that the whole country is characterized by the requirement of very cold weather wear during winter nighttime while 72% of the area of the country requires tropical weather wear during summer daytime. Only 71% of the area of the country requires comfortable weather wear during summer nighttime while there is no area requiring comfortable weather wear during winter nighttime. Latitudinal gradient of clo values was observed during all months of the year. Maximum latitudinal gradients of clo values during the daytime were found for the months of April and May. The clo classification in relation to climate has been done for Egypt. Copyright © 2006 Royal Meteorological Society."
"16444324800;7102128820;","A sensitivity study of the effect of horizontal photon transport on the radiative forcing of contrails",2007,"10.1175/JAS3915.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250015535&doi=10.1175%2fJAS3915.1&partnerID=40&md5=e7253101e6ac283864934ff630bcdd2f","With the rapid growth in air travel, there is concern over the radiative impact of contrails and aircraft-induced cirrus on climate. Previous radiation calculations on contrails have almost all used the independent column approximation, which neglects the transport of photons through the sides of the contrail, but in this study the 3D effects are quantified using the Spherical Harmonic Discrete Ordinate Method (SHDOM). The authors have investigated the dependence of shortwave and longwave radiative forcing on contrail aspect ratio, optical depth, solar zenith angle, solar azimuth angle relative to contrail orientation, particle size, particle habit, surface albedo, and surface temperature. It is found that inclusion of 3D transport results in an increase in the positive longwave radiative forcing of the contrail and either an increase or a decrease in the magnitude of the negative shortwave radiative forcing depending on the orientation of the contrail with respect to the sun. Although these two effects are individually quite modest (of order 10%), the fact that the total shortwave and longwave forcings largely cancel during the day means that the relative change in the net radiative forcing due to the 3D effect is substantial; in some cases this results in a doubling of the net forcing of the contrail, in other cases changing its sign. On a more general note, the relatively simple geometry of contrail cirrus provides an ideal test case for explaining the various mechanisms by which 3D photon transport can change the radiative effect of clouds, which can be rather difficult to visualize for more complex cloud scenarios. © 2007 American Meteorological Society."
"7005002831;57126848900;7005450157;7004012437;16645471500;7404334532;16645822900;6505702510;56016057500;7101718859;","Accurate monitoring of terrestrial aerosol and total solar irradiance: Introducing the Glory mission",2007,"10.1175/BAMS-88-5-677","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250882163&doi=10.1175%2fBAMS-88-5-677&partnerID=40&md5=f0089f5fa63ca7fb4bbfa905e76b97dd","The NASA Glory mission is intended to facilitate and improve upon long-term monitoring of two key forcings influencing global climate. One of the mission's principal objectives is to determine the global distribution of detailed aerosol and cloud properties with unprecedented accuracy, thereby facilitating the quantification of the aerosol direct and indirect radiative forcings. The other is to continue the 28-yr record of satellite-based measurements of total solar irradiance from which the effect of solar variability on the Earth's climate is quantified. These objectives will be met by flying two state-of-the-art science instruments on an Earth-orbiting platform. Based on a proven technique demonstrated with an aircraft-based prototype, the Aerosol Polarimetry Sensor (APS) will collect accurate multiangle photopolarimetric measurements of the Earth along the satellite ground track within a wide spectral range extending from the visible to the shortwave infrared. The Total Irradiance Monitor (TIM) is an improved version of an instrument currently flying on the Solar Radiation and Climate Experiment (SORCE) and will provide accurate and precise measurements of spectrally integrated sunlight illuminating the Earth. Because Glory is expected to fly as part of the A-Train constellation of Earth-orbiting spacecraft, the APS data will also be used to improve retrievals of aerosol climate forcing parameters and global aerosol assessments with other A-Train instruments. In this paper, we detail the scientific rationale and objectives of the Glory mission, explain how these scientific objectives dictate the specific measurement strategy, describe how the measurement strategy will be implemented by the APS and TIM, and briefly outline the overall structure of the mission. It is expected that the Glory results will be used extensively by members of the climate, solar, atmospheric, oceanic, and environmental research communities as well as in education and outreach activities. © 2007 American Meteorological Society."
"16200336000;7005447447;38362385200;8583876500;55204225500;35466845900;36836439900;","Balloon-borne observations of high aerosol concentrations near the summertime tropopause over the Tibetan Plateau",2007,"10.1016/j.atmosres.2006.08.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34047257365&doi=10.1016%2fj.atmosres.2006.08.003&partnerID=40&md5=b0a5311112ed3e77a7ab1de83c4e2f84","Vertical profiles of aerosols (radii ≥ 0.15 μm) were measured using a balloon-borne optical particle counter at Lhasa (29.4°N, 91.1°E, 3650 m a.s.l.), China in 1999. The measurements display occurrences of relatively high number concentrations (0.7-0.8 particles cm- 3) of sub-micron size aerosols with radii = 0.15-0.6 μm near the tropopause region (between about 130 and 70 hPa) in the Asian summer monsoon period. Size distributions of the observed aerosols are clearly different from those of cirrus clouds. The high number concentrations occurred inside the Tibetan anticyclone, suggesting that these were triggered by deep convection over the Tibetan Plateau. Convective transportation of lower tropospheric materials may affect atmospheric constituents near the tropopause region. In addition, the effects of adiabatic cooling and hydration associated with deep convection may also trigger enlargement of pre-existing and/or vertically-transported aqueous solution droplets (e.g., liquid sulfate particles) near the tropopause region. Enhancement of the aerosols should be considered in assessing the global/regional climate system and the geochemical cycle. © 2006 Elsevier B.V. All rights reserved."
"16245459800;8884425800;35514012200;","The effect of the Galápagos Islands on the equatorial Pacific cold tongue",2007,"10.1175/JPO3048.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250786140&doi=10.1175%2fJPO3048.1&partnerID=40&md5=e72ef9bef6f889a401736e486e462e42","A reduced-gravity ocean general circulation model of the tropical Pacific Ocean is used to determine potential improvements to the simulated equatorial Pacific cold tongue region through choices in horizontal resolution and coastline geometry - in particular, for the Galápagos Islands. Four simulations are performed, with identical climatological forcing. Results are compared between model grids with and without the Galápagos Islands, with coarse and fine resolutions. It is found that properly including the Galápagos Islands results in the obstruction of the Equatorial Undercurrent (EUC), which leads to improvements in the simulated spatial structure of the cold tongue, including a basinwide warming of up to 2°C in the east-central Pacific. The obstruction of the EUC is directly related to the improvements east of the Galápagos Islands, and for the basinwide reduction of the tropical cold bias through an equatorial dynamical adjustment. The pattern of SST warming resulting from the inclusion of the Galápagos Islands is similar to that of the known cold biases in ocean models and the current National Oceanic and Atmospheric Administration Climate Forecast System. It is thought that such an improvement would have a considerable impact on the ability of coupled ocean-atmosphere and ocean-ecosystem models to produce realistic clouds, precipitation, surface ocean bioproductivity, and carbon cycling in the tropical Pacific Ocean. © 2007 American Meteorological Society."
"6507355875;6603256951;7202527347;7404696407;","Submesoscale spatiotemporal variability of North American Monsoon rainfall over complex terrain",2007,"10.1175/JCLI4093.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249684407&doi=10.1175%2fJCLI4093.1&partnerID=40&md5=38ec83d4d7139b8ce70c3bcc8dab0183","The authors analyze information from rain gauges, geostationary infrared satellites, and low earth orbiting radar in order to describe and characterize the submesoscale (<75 km) spatial pattern and temporal dynamics of rainfall in a 50 km × 75 km study area located in Sonora, Mexico, in the periphery of the North American monsoon system core region. The temporal domain spans from 1 July to 31 August 2004, corresponding to one monsoon season. Results reveal that rainfall in the study region is characterized by high spatial and temporal variability, strong diurnal cycles in both frequency and intensity with maxima in the evening hours, and multiscaling behavior in both temporal and spatial fields. The scaling parameters of the spatial rainfall fields exhibit dependence on the rainfall rate at the synoptic scale. The rainfall intensity exhibits a slightly stronger diurnal cycle compared to the rainfall frequency, and the maximum lag time between the two diurnal peaks is within 2.4 h, with earlier peaks observed for rainfall intensity. The time of maximum cold cloud occurrence does not vary with the infrared threshold temperature used (215-235 K), while the amplitude of the diurnal cycle varies in such a way that deep convective cells have stronger diurnal cycles. Furthermore, the results indicate that the diurnal cycle of cold cloud occurrence can be used as a surrogate for some basic features of the diurnal cycle of rainfall. The spatial pattern and temporal dynamics of rainfall are modulated by topographic features and large-scale features (circulation and moisture fields as related to geographical location). As compared to valley areas, mountainous areas are characterized by an earlier diurnal peak, an earlier date of maximum precipitation, closely clustered rainy hours, frequent yet small rainfall events, and less dependence of precipitation accumulation on elevation. As compared to the northern section of the study area, the southern section is characterized by strong convective systems that peak late diurnally. The results of this study are important for understanding the physical processes involved, improving the representation of submesoscale variability in models, downscaling rainfall data from coarse meteorological models to smaller hydrological scales, and interpreting and validating remote sensing rainfall estimates. © 2007 American Meteorological Society."
"12807105000;7403382287;","Effects of genotype and transpiration rate on the uptake and accumulation of perchlorate (ClO4-) in lettuce",2007,"10.1021/es062337s","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248217619&doi=10.1021%2fes062337s&partnerID=40&md5=3210d4bc425643930d201751365da889","Although evidence of perchlorate accumulation in plants exists, there is a scarcity of information concerning the key factors and mechanisms involved. To ascertain whether genotypic variation in perchlorate accumulation occurs within lettuce, hydroponic plant uptake experiments were conducted with five types of lettuce (Lactuca sativa L.), which were grown to market size at three perchlorate (ClO4-) concentrations (1, 5, or 10 μg/L). Perchlorate accumulated in the leafy tissues to varying amounts, ranging from 4 to 192 μg/kg fresh weight (FW), and the ranking of perchlorate accumulation was crisphead &gt; butter head &gt; romaine &gt; red leaf &gt; green leaf. The effect of transpiration rate on perchlorate accumulation was further examined using crisphead, butter head, and green leaf lettuce. By growing lettuce in controlled-environment chambers with two climatic regimes, ""cloudy, humid, cool"" (80% RH, 18/15 °C, 250 μmol/m2s photosynthetic photon flux density (PPFD)) and ""sunny, dry, warm"" (∼50% RH, 28/18 °C, 500 μmol/m2s PPFD), up to 2.7-fold differences in transpiration rates were achieved. Across all three genotypes, the plants that transpired more water accumulated more perchlorate on a whole-head basis; however, the effect of transpiration rate on perchlorate accumulation was not as great as expected. Despite 2.0-2.7-fold differences in transpiration rate, there were only 1.2-2.0-fold differences in perchlorate accumulation. In addition to whole-head analysis, plants were sectioned into inner, middle, and outer leaves and processed separately. Overall, the ranking of perchlorate accumulation was outer leaves &gt; middle leaves &gt; inner leaves. Transpiration rate has a clear effect on perchlorate accumulation in lettuce, but other factors are influential and deserve exploration. © 2007 American Chemical Society."
"38062095100;12771886800;35187557400;7405483854;6506920369;7402813218;","Evaluation of MOD16 algorithm using MODIS and ground observational data in winter wheat field in North China Plain",2007,"10.1002/hyp.6679","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247533238&doi=10.1002%2fhyp.6679&partnerID=40&md5=17caee6373f18b28571984b98e0807e5","Evapotranspiration (ET) is an important factor for understanding hydrological processes and climate dynamics. Remote sensing is considered as the most promising tool for estimation of ET over a large spatial scale. The purpose of this study is to analyse and evaluate the MOD16 algorithm, developed by Nishida et al. (2003a,b), in winter wheat fields by using MODIS land products, MOD11-land surface temperature and MOD13-standard normalized difference vegetation index (NDVI), as well as observations at the Yucheng Experimental Station, China in 2002. The original MOD16 is a dual-source ET model in which the evaporation fraction (EF) for bare soil surface is estimated using the VI-Ts diagram method, and EF for vegetation is determined by a function of canopy resistance, aerodynamic resistance and air temperature. We analysed a radiation budget sub-model and found that the estimate for solar radiation is acceptable only on cloud-free days. We also found that, in the original MOD16, seasonal variations of minimum canopy resistance and physiological temperatures are not considered, which results in overestimation of canopy resistance when leaf area index (LAI) is less than 2.5. Because the strong unstable thermal stratification over the dry bare soil surface is ignored in the original algorithm, wind speed is overestimated and aerodynamic resistance above the vegetation surface is underestimated. We then modified the original MOD16 algorithm. The result shows that both EF and ET for vegetation estimated with the modified algorithm are in consistent with both the observations of an eddy covariance system and the calculations using the Penman-Monteith method. Copyright © 2007 John Wiley & Sons, Ltd."
"55907565200;7005177384;6603214557;","A less restrictive technique for the estimation of understory light under variable weather conditions",2007,"10.1016/j.foreco.2007.01.067","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34047151186&doi=10.1016%2fj.foreco.2007.01.067&partnerID=40&md5=ed6d8147ffa87b592a802dc34a433afa","Many techniques have been developed to estimate mean available light in forest understories. The standard methods estimate average seasonal PAR by recording it in situ with quantum sensors or through simulation using hemispherical image analysis (HIA). Other techniques have been developed to overcome some of the drawbacks of the standard methods, such as high cost, cumbersome equipment, user bias, and limited replication. The ""Overcast"" method allows rapid evaluation of average seasonal PAR in most situations by taking instantaneous measurements, but is restricted by the overcast sky conditions required. The present study proposes a new, less restrictive method (BF2), that uses a sensor array under a hemispherical dome to overcome the sky condition restrictions of the Overcast method, and tests it against the Overcast and HIA techniques. The study also evaluates the method's ability to predict seedling growth and morphology. The BF2 method provided rapid and precise estimations of %PAR under variable sky conditions, as well as good estimations of seedling's responses, and is suitable for multiple site or highly replicated designs. The methods were used under deciduous stands with contrasting structures. © 2007 Elsevier B.V. All rights reserved."
"35887706900;7004174939;35464731600;7003897194;7201798916;","On the twilight zone between clouds and aerosols",2007,"10.1029/2007GL029253","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250718596&doi=10.1029%2f2007GL029253&partnerID=40&md5=6289f57de67acb2f4b817d1bf83fbb57","Cloud and aerosols interact and form a complex system leading to high uncertainty in understanding climate change. To simplify this non-linear system it is customary to distinguish between ""cloudy"" and ""cloud-free"" areas and measure them separately. However, we find that clouds are surrounded by a ""twilight zone"" - a belt of forming and evaporating cloud fragments and hydrated aerosols extending tens of kilometers from the clouds into the so-called cloud-free zone. The gradual transition from cloudy to dry atmosphere is proportional to the aerosol loading, suggesting an additional aerosol effect on the composition and radiation fluxes of the atmosphere. Using AERONET data, we find that the measured aerosol optical depth is higher by 13% ± 2% in the visible and 22% ± 2% in the NIR in measurements taken near clouds relative to its value in the measurements taken before or after, and that 30%-60% of the free atmosphere is affected by this phenomenon. Copyright 2007 by the American Geophysical Union."
"7402565763;","Variability of the relationship between particle size and cloud-nucleating ability",2007,"10.1029/2006GL028850","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250788567&doi=10.1029%2f2006GL028850&partnerID=40&md5=6cd84dcaebf8f148be86b8534a1d0f70","Cloud condensation nuclei (CCN) are characterized by their critical supersaturation (Sc), which is a function of particle size and chemistry, namely water solubility. Measurements that relate particle size to Sc can thus be used to determine CCN solubility. A sufficiently small degree of variability of size-Sc measurements has been cited as evidence that CCN can be deduced from particle size measurements alone. Since particle size is so much easier to measure than particle chemistry or CCN this would have significant advantages for investigations of the largest climate uncertainty, the indirect aerosol effect; e.g., remote sensing of CCN. However, we present size-Sc measurements with a greater range of variability, which appears to at least limit or cast doubts on the practicality of deducing CCN from particle size measurements. Copyright 2007 by the American Geophysical Union."
"7402242924;57189178163;7004239939;25647475300;","Polar mesospheric cloud mass and the ice budget: 2. Application to satellite data sets",2007,"10.1029/2006JD007532","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250661468&doi=10.1029%2f2006JD007532&partnerID=40&md5=bf67fdad437307684d39b00859c63fd1","We use satellite observations of mid-UV solar backscattered light from polar mesospheric clouds (PMCs) to constrain the water ice budget. We compare the PMC mass from observations by two instruments: the limb viewing Student Nitric Oxide Explorer (SNOE) and the nadir viewing Solar Backscattered UltraViolet (SBUV) experiments. At 70 ± 2.5°N we find that SNOE measures over three times more PMC mass than the less sensitive SBUV experiment. We directly compare the two data sets by selecting only the brightest 10% of SNOE clouds so that the SNOE and SBUV PMC occurrence frequencies are the same. This comparison shows that the PMC mass averaged over five northern seasons is the same to within uncertainties in the ice particle size distribution. We also find that near midday, the northern SBUV PMC mass is a factor of 2.4 times greater than the southern PMC mass. These results provide new constraints for global climate models of PMC formation. Copyright 2007 by the American Geophysical Union."
"6701530981;6603873829;7102410621;7004426987;57206330745;","Sensitivity of the shortwave radiative budget to the parameterization of ice crystal effective radius",2007,"10.1029/2006JD007791","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250650136&doi=10.1029%2f2006JD007791&partnerID=40&md5=e78cce71f34bbbd8343f96f6034ade2b","A new effective particle size (R<inf>eff</inf>) parameterization for ice clouds has been formulated based on depth into cloud relative to cloud top. This parameterization has been developed based on an extensive data set of lidar and radar ice cloud retrievals. Using this parameterization within the stand-alone radiation code from the European Centre for Medium Range Weather Forecasting (cy23r4), the performance of the new parameterization is compared with the more commonly used parameterizations based on temperature and/or ice water content. An evaluation is performed on the basis of observed shortwave fluxes for 13 days with persistent ice cloud decks, with no liquid clouds beneath, over the Cabauw Experimental Site for Atmospheric Research in the Netherlands. For each of these clouds the shortwave flux is calculated after which the distribution of the differences between the observed and modeled shortwave fluxes from the combined 13 days are compared with each other. The new parameterization shows a median absolute difference of 0.7 W m-2 relative to the observations. The control parameterization based on temperature shows a median absolute difference of 15 W m-2. Within the framework of the KNMI regional climate model (RACMO2), the new parameterization yields an effective particle size versus temperature distribution very similar to the observed distributions from lidar and radar retrievals. Results from a 1-year integration indicate that the domain averaged monthly mean planetary albedo and transmissivity change by a maximum of 2.6 and 2.4%, respectively, using the new parameterization compared to the temperature-based parameterization. Copyright 2007 by the American Geophysical Union."
"35596728700;6701410484;7004276118;7402242924;","Polar mesospheric cloud mass and the ice budget: 3. Application of a coupled ice-chemistry-dynamics model and comparison with observations",2007,"10.1029/2006JD007499","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250635514&doi=10.1029%2f2006JD007499&partnerID=40&md5=b0584a197c0684de94a0da1e9b00ba6b","We have combined a two-dimensional chemical/dynamics model with a monodisperse parameterization of polar mesospheric clouds (PMCs) to study the interaction of PMCs with the climate of the summer mesopause region. First, we show that PMC absorption of terrestrial and solar IR radiation lead to atmospheric heating rates which can exceed 10 K/day. This heat is dissipated by increased upwelling above the cloud layer and by a 2-6 K temperature increase. We then calculate the global PMC ice mass and evaluate its sensitivity to IR heating, assumed particle size and level of solar activity. Inclusion of the temperature increase in the model can reduce the calculated ice mass by up to a factor of two. The calculated solar cycle range in the ice mass is also about a factor of two. The calculated latitude distribution and solar cycle range of PMC ice mass are in good agreement with recent analyses of PMC satellite data. Finally, we test the hypothesis that PMC formation leads to ozone changes by comparing our model with ozone data from the Halogen Occultation Experiment (HALOE). The data show a 20-30% ozone enhancement above PMCs. In the model, dehydration above the cloud layer leads to an ozone increase due to lowered HO<inf>x</inf>. However, this competes with the temperature increase from IR absorption that can damp out this ozone increase. Surprisingly, for realistic estimates of the terrestrial IR flux, the model ozone response is reduced to well below that observed by HALOE. Copyright 2007 by the American Geophysical Union."
"15044936400;6506730508;15076205500;7006329853;","Modeling the transport and optical properties of smoke aerosols from African savanna fires during the Southern African Regional Science Initiative campaign (SAFARI 2000)",2007,"10.1029/2006JD007528","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250643594&doi=10.1029%2f2006JD007528&partnerID=40&md5=c35a8a1a6a315517a9b31e1d94f5b20f","We investigate the transport and optical properties of smoke aerosols from southern Africa using an offline three-dimensional aerosol transport model. We use Sun photometer retrieved particle size distributions and monthly mean satellite-derived smoke emissions as input parameters. We find that using these observations in our model allows us to reproduce the measured optical properties collected during the Southern African Regional Science Initiative campaign (SAFARI 2000). In particular, we find day-to-day oscillations in the simulated aerosol optical thickness (AOT) similar to Aerosol Robotic Network (AERONET) retrievals, suggesting that variations in aerosol loading are controlled more by transport processes than fluctuations in smoke emissions. We also find that the simulated AOT, Ångström exponent, and single scattering albedo compare well to AERONET. The model and satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multiangle Imaging Spectroradiometer (MISR) also show that the dominant transport of smoke plumes over Africa was westward during September 2000. However, the satellite observations show higher AOT values than our model over the Atlantic Ocean. These higher values observed by the satellites may be a result of poor single scattering assumptions and the contamination by subpixel clouds in the retrievals. However, the monthly mean smoke emissions may also be too low, resulting in low simulated AOT values. We also find discrepancies between MODIS and MISR, which limit our ability to use the satellite data to validate our model. Our work suggests strategies for improving the treatment of smoke aerosols from African biomass burning in climate and microphysical models. Copyright 2007 by the American Geophysical Union."
"8846887600;57190749913;","North Atlantic cloud cover response to the North Atlantic oscillation and relationship to surface temperature changes",2007,"10.1029/2006JD007516","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250310876&doi=10.1029%2f2006JD007516&partnerID=40&md5=646bf2fed744b4a54677084bf7a14ab1","Cloud cover changes over the high-latitude North Atlantic during January associated with the North Atlantic oscillation (NAO) are studied using the Polar MM5 regional climate model. The cloud response to the NAO is marked by an increase in cloudiness during the high phase over much of the North Atlantic east of Greenland and an overall decrease in cloudiness west of Greenland. These cloud changes are accompanied by surface cloud radiative forcing anomalies that are of the same sign as the model-simulated surface air temperature (SAT) anomalies in most areas. NAO-related cloud cover changes in January are therefore likely to represent a positive feedback on the SAT changes induced by anomalous atmospheric advection. Copyright 2007 by the American Geophysical Union."
"57202301596;7005170782;7601492669;55703823500;8247122100;7202801743;7202474186;57202396417;7003499257;","A regional ocean-atmosphere model for eastern Pacific climate: Toward reducing tropical biases",2007,"10.1175/JCLI4080.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847360807&doi=10.1175%2fJCLI4080.1&partnerID=40&md5=034127235de08aa30b8fddbafc92a97c","The tropical Pacific Ocean is a climatically important region, home to El Niño and the Southern Oscillation. The simulation of its climate remains a challenge for global coupled ocean-atmosphere models, which suffer large biases especially in reproducing the observed meridional asymmetry across the equator in sea surface temperature (SST) and rainfall. A basin ocean general circulation model is coupled with a full-physics regional atmospheric model to study eastern Pacific climate processes. The regional ocean atmosphere model (ROAM) reproduces salient features of eastern Pacific climate, including a northward displaced intertropical convergence zone (ITCZ) collocated with a zonal band of high SST, a low-cloud deck in the southeastern tropical Pacific, the equatorial cold tongue, and its annual cycle. The simulated low cloud deck experiences significant seasonal variations in vertical structure and cloudiness; cloud becomes decoupled and separated from the surface mixed layer by a stable layer in March when the ocean warms up, leading to a reduction in cloudiness. The interaction of low cloud and SST is an important internal feedback for the climatic asymmetry between the Northern and Southern Hemispheres. In an experiment where the cloud radiative effect is turned off, this climatic asymmetry weakens substantially, with the ITCZ migrating back and forth across the equator following the sun. In another experiment where tropical North Atlantic SST is lowered by 2°C - say, in response to a slow-down of the Atlantic thermohaline circulation as during the Younger Dryas - the equatorial Pacific SST decreases by up to 3°C in January-April but changes much less in other seasons, resulting in a weakened equatorial annual cycle. The relatively high resolution (0.5°) of the ROAM enables it to capture mesoscale features, such as tropical instability waves, Central American gap winds, and a thermocline dome off Costa Rica. The implications for tropical biases and paleoclimate research are discussed. © 2007 American Meteorological Society."
"16245849400;7401776640;","Low-level cloud variability over the equatorial cold tongue in observations and models",2007,"10.1175/JCLI4073.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247620296&doi=10.1175%2fJCLI4073.1&partnerID=40&md5=7d1bb8ebd3afa7215a23fbe4c120a096","Examination of cloud and meteorological observations from satellite, surface, and reanalysis datasets indicates that monthly anomalies in low-level cloud amount and near-surface temperature advection are strongly negatively correlated on the southern side of the equatorial Pacific cold tongue. This inverse correlation occurs independently of relationships between cloud amount and sea surface temperature (SST) or lower tropospheric static stability (LTS), and the combination of advection plus SST or LTS explains significantly more interannual cloud variability in a multilinear regression than does SST or LTS alone. Warm anomalous advection occurs when the equatorial cold tongue is well defined and the southeastern Pacific trade winds bring relatively warm air over colder water. Ship meteorological reports and soundings show that the atmospheric surface layer becomes stratified under these conditions, thus inhibiting the upward mixing of moisture needed to sustain cloudiness against subsidence and entrainment drying. Cold anomalous advection primarily occurs when the equatorial cold tongue is weak or absent and the air-sea temperature difference is substantially negative. These conditions favor a more convective atmospheric boundary layer, greater cloud amount, and less frequent occurrence of clear sky. Examination of output from global climate models developed by the Geophysical Fluid Dynamics Laboratory (GFDL) and the National Center for Atmospheric Research (NCAR) indicates that both models generally fail to simulate the cloud-advection relationships observed on the northern and southern sides of the equatorial cold tongue. Although the GFDL atmosphere model does reproduce the expected signs of cloud-advection correlations when forced with prescribed historical SST variations, it does not consistently do so when coupled to an ocean model. The NCAR model has difficulty reproducing the observed correlations in both atmosphere-only and coupled versions. This suggests that boundary layer cloud parameterizations could be improved through better representation of the effects of advection over varying SST. © 2007 American Meteorological Society."
"54790508000;35579822900;6602726536;7004031990;7005068720;","Comparison of MODIS, eddy covariance determined and physiologically modelled gross primary production (GPP) in a Douglas-fir forest stand",2007,"10.1016/j.rse.2006.09.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947308620&doi=10.1016%2fj.rse.2006.09.010&partnerID=40&md5=c09bd6a3bb85c602a84d61ef535dc944","Quantification of the magnitude of net terrestrial carbon (C) uptake, and how it varies inter-annually, is an important question with future potential sequestration influenced by both increased atmospheric CO2 and changing climate. However the assessment of differences in measured and modeled C accumulation is a challenging task due to the significant fine scale variation occurring in terrestrial productivity due to soil, climate and vegetation characteristics as well as difficulties in measuring carbon accumulation over large spatial areas. The Moderate Resolution Imaging Spectroradiometer (MODIS) offers a means of monitoring gross primary production (GPP), both spatially and temporally, routinely from space. However it is critical to compare and contrast the temporal dynamics of the C and water fluxes with those measured from ground-based networks, or estimated using physiological models. In this paper, using a number of approaches, our objective is to determine if any systematic biases exists in either the MODIS, or the modeled estimates of fluxes, relative to the measurements made over an evergreen, needleleaf temperate rainforest on Vancouver Island, Canada. Results indicate that 8-day GPP as predicted with a simple physiological model (3PGS), forced using local meteorology and canopy characteristics, matched measured fluxes very well (r2 = 0.86, p &lt; 0.001) with no significant difference between eddy covariance (EC) and modeled GPP (p &lt; 0.001). In addition, modeled water supply closely matched measured relative available soil water content at the site. Using canopy characteristics from the MODIS fraction of photosynthetically active radiation (fPAR) algorithm, slightly reduced the correspondence of the predictions due to a large number of unsuccessful retrievals (83%) due to sun angle, snow and cloud. Predictions of GPP based on the MODIS GPP algorithm, forced using local meteorology and canopy characteristics, were also highly correlated with EC measurements (r2 = 0.89, p &lt; 0.001) however these estimates were biased under predicting GPP. Estimates of GPP based on the most recent MODIS reprocessing (collection 4.5) remained highly correlated (r2 = 0.88, p &lt; 0.001) yet were also the most biased with the estimates being 30% less than the EC-measured GPP. Most of the variance in GPP at the site was explained by the absorbed photosynthetically active radiation. We also compared the nighttime respiration as measured over 2 years at the site with the minimum 8-day MODIS land surface temperature and found a significant relationship (r2 = 0.57), similar to other studies. © 2006 Elsevier Inc. All rights reserved."
"6603385031;7202784114;16317970100;7004715270;15318900900;7402480218;7005968859;7102046393;6701873414;","Can ice-nucleating aerosols affect arctic seasonal climate?",2007,"10.1175/BAMS-88-4-541","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249067391&doi=10.1175%2fBAMS-88-4-541&partnerID=40&md5=68d1b0c70d499c8b57aa3737ec3ffa1f","Mixed-phase stratus clouds are ubiquitous in the Arctic and play an important role in climate in this region. However, climate and regional models have generally proven unsuccessful at simulating Arctic cloudiness, particularly during the colder months. Specifically, models tend to underpredict the amount of liquid water in mixed-phase clouds. The Mixed-Phase Arctic Cloud Experiments (M-PACE), conducted from late September through October 2004 in the vicinity of the Department of Energy's Atmospheric Radiation Measurement (ARM) North Slope of Alaska field site, focused on characterizing low-level Arctic stratus clouds. Ice nuclei (IN) measurements were made using a continuous-flow ice thermal diffusion chamber aboard the University of North Dakota's Citation II aircraft. These measurements indicated IN concentrations that were significantly lower than those used in many models. Using the Regional Atmospheric Modeling System (RAMS), we show that these low IN concentrations, as well as inadequate parameterizations of the depletion of IN through nucleation scavenging, may be partially responsible for the poor model predictions. Moreover, we show that this can lead to errors in the modeled surface radiative energy budget of 10-100 W m-2. Finally, using the measured IN concentrations as input to RAMS and comparing to a mixed-phase cloud observed during M-PACE, we show excellent agreement between modeled and observed liquid water content and net infrared surface flux. ©2007 American Meteorological Society."
"7005729142;6701530981;7102410621;7004319487;7102128820;7007114756;","Refinements to ice particle mass dimensional and terminal velocity relationships for ice clouds. Part II: Evaluation and parameterizations of ensemble ice particle sedimentation velocities",2007,"10.1175/JAS3900.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247553285&doi=10.1175%2fJAS3900.1&partnerID=40&md5=450368a4c9c76305fc9a4c4c09b3b019","This two-part study addresses the development of reliable estimates of the mass and fall speed of single ice particles and ensembles. Part I of the study reports temperature-dependent coefficients for the mass-dimensional relationship, m = aDb, where D is particle maximum dimension. The fall velocity relationship, Vt = ADB, is developed from observations in synoptic and low-latitude, convectively generated, ice cloud layers, sampled over a wide range of temperatures using an assumed range for the exponent b. Values for a, A, and B were found that were consistent with the measured particle size distributions (PSD) and the ice water content (IWC). To refine the estimates of coefficients a and b to fit both lower and higher moments of the PSD and the associated values for A and B, Part II uses the PSD from Part I plus coincident, vertically pointing Doppler radar returns. The observations and derived coefficients are used to evaluate earlier, single-moment, bulk ice microphysical parameterization schemes as well as to develop improved, statistically based, microphysical relationships. They may be used in cloud and climate models, and to retrieve cloud properties from ground-based Doppler radar and spaceborne, conventional radar returns. © 2007 American Meteorological Society."
"7005890514;7005495256;7103060756;","Inferring climate sensitivity from volcanic events",2007,"10.1007/s00382-006-0193-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847153042&doi=10.1007%2fs00382-006-0193-x&partnerID=40&md5=f20570532d4a324a20145e8e1b08db97","The possibility of estimating the equilibrium climate sensitivity of the earth-system from observations following explosive volcanic eruptions is assessed in the context of a perfect model study. Two modern climate models (the CCCma CGCM3 and the NCAR CCSM2) with different equilibrium climate sensitivities are employed in the investigation. The models are perturbed with the same transient volcano-like forcing and the responses analysed to infer climate sensitivities. For volcano-like forcing the global mean surface temperature responses of the two models are very similar, despite their differing equilibrium climate sensitivities, indicating that climate sensitivity cannot be inferred from the temperature record alone even if the forcing is known. Equilibrium climate sensitivities can be reasonably determined only if both the forcing and the change in heat storage in the system are known very accurately. The geographic patterns of clear-sky atmosphere/surface and cloud feedbacks are similar for both the transient volcano-like and near-equilibrium constant forcing simulations showing that, to a considerable extent, the same feedback processes are invoked, and determine the climate sensitivity, in both cases. © Springer-Verlag 2006."
"10046018100;6701735773;6602137606;8213763800;23981063100;","Assessment of physical parameterizations using a global climate model with stretchable grid and nudging",2007,"10.1175/MWR3338.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248353921&doi=10.1175%2fMWR3338.1&partnerID=40&md5=a7d14d4b7b133b3f00f456bc94e4728d","The Laboratoire de Météorologie Dynamique atmospheric general circulation model with zooming capability (LMDZ) has been used in a nudged mode to enable comparison of model outputs with routine observations and evaluate the model physical parameterizations. Simulations have been conducted with a stretched grid refined over the vicinity of Paris, France, where observations, collected at the Trappes station (Météo-France) and at the Site Instrumental de Recherche par Télédétection Atmosphérique observatory, are available. For the purpose of evaluation of physical parameterizations, the large-scale component of the modeled circulation is adjusted toward ECMWF analyses outside the zoomed area only, whereas the inside region can evolve freely. A series of sensitivity experiments have been performed with different parameterizations of land surface and boundary layer processes. Compared with previous versions of the LMDZ model, a ""thermal plume model,"" in association with a constant resistance to evaporation improves agreement with observations. The new parameterization significantly improves the representation of seasonal and diurnal cycles of near-surface meteorology, the day-to-day variability of planetary boundary layer height, and the cloud radiative forcing. This study emphasizes the potential of using a climate model with a nudging and zooming capability to assess model physical parameterizations. © 2007 American Meteorological Society."
"16025327700;56246783000;37562220900;7003523086;12760844400;16025290700;57219456056;57210785732;","The atmospheric global electric circuit: An overview",2007,"10.1016/j.atmosres.2006.05.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847421433&doi=10.1016%2fj.atmosres.2006.05.005&partnerID=40&md5=ce83d107a667f33fb4f00c9244d242c4","Research work in the area of the Global Electric Circuit (GEC) has rapidly expanded in recent years mainly through observations of lightning from satellites and ground-based networks and observations of optical emissions between cloud and the ionosphere. After reviewing this progress, we critically examine the role of various generators of the currents flowing in the lower and upper atmosphere and supplying currents to the GEC. The role of aerosols and cosmic rays in controlling the GEC and linkage between climate, solar-terrestrial relationships and the GEC has been briefly discussed. Some unsolved problems in this area are reported for future investigations. © 2006 Elsevier B.V. All rights reserved."
"15071316400;7404493635;7203015939;57214748952;","Predictions of future climate change in the caribbean region using global general circulation models",2007,"10.1002/joc.1416","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247863656&doi=10.1002%2fjoc.1416&partnerID=40&md5=6fae57c6c28634bf75c3811faa5aa119","Since the 1800s the global average CO2 mixing ratio has increased and has been related to increases in surface air temperature (0.6 ± 0.2°C) and variations in precipitation patterns among other weather and climatic variables. The Small Island Developing States (SIDS), according to the 2001 report of the Intergovernmental Panel on Climate Change (IPCC), are likely to be among the most seriously impacted regions on Earth by global climate changes. In this work, three climate change scenarios are investigated using the Parallel Climate Model (PCM) to study the impact of the global anthropogenic CO2 concentration increases on the Caribbean climate. A climatological analysis of the Caribbean seasonal climate variation was conducted employing the National Center for Environmental Prediction (NCEP) reanalysis data, the Xie-Arkin precipitation and the Reynolds-Smith Sea Surface Temperature (SST) observed data. The PCM is first evaluated to determine its ability to predict the present time Caribbean climatology. The PCM tends to under predict the SSTs, which along with the cold advection controls the rainfall variability. This seems to be a main source of bias considering the low model performance to predict rainfall activity over the Central and southern Caribbean. Future predictions indicate that feedback processes involving evolution of SST, cloud formation, and solar radiative interactions affect the rainfall annual variability simulated by PCM from 1996 to 2098. At the same time two large-scale indices, the Southern Oscillation Index (SOI) and the North Atlantic Oscillation (NAO) are strongly related with this rainfall annual variability. A future climatology from 2041 to 2058 is selected to observe the future Caribbean condition simulated by the PCM. It shows, during this climatology range, a future warming of approximately 1 °C (SSTs) along with an increase in the rain production during the Caribbean wet seasons (early and late rainfall seasons). Although the vertical wind shear is strengthened, it typically remains lower than 8 m/s, which along with SST &gt; 26.5 °C provides favorable conditions for possible future increases in tropical storm frequency. Copyright © 2006 Royal Meteorological Society."
"7004154240;57207660719;","Influence of wildfire induced land-cover changes on clouds and precipitation in Interior Alaska - A case study",2007,"10.1016/j.atmosres.2006.06.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847388968&doi=10.1016%2fj.atmosres.2006.06.004&partnerID=40&md5=90d281a64a1e567d9bf82f9457e4cf1f","As especially observed during the 2004 Alaska fire season, huge wildfires drastically alter land cover leading to a change in the dynamic (roughness length), radiative (albedo, emissivity), vegetative (vegetation type and fraction, stomatal resistance), thermal (soil heating, thawing of permafrost), and hydrological (water loss due to the fire) surface characteristics. A case study was performed with the Mesoscale Model generation 5 (MM5) assuming the landscape prior to and after the 2004 wildfires in Interior Alaska to quantitatively examine the impact of fire-caused land-cover changes on summer cloud and precipitation formation. The results of our model study show that sensible heat fluxes into the atmosphere and air temperatures increase by up to 225 W m- 2 and 3 K over burnt areas. Burnt areas &gt; 600 km2 and &gt; 800 km2 significantly (at the 90% or higher confidence level according to statistical tests) affect sensible and latent heat fluxes, respectively. While burnt areas must exceed 1600 km2 for the increased buoyancy to significantly increase the upward transport of air, burnt areas &gt; 600 km2 already experience enough enhanced lifting to produce areas of increased cloud-water, rainwater, and graupel mixing ratios followed by an area of decreased mixing ratios downwind of them. The spatial and temporal distribution of precipitation changes appreciably and resulted in significant increases of 84 h-accumulated precipitation (by up to 15.1 mm) in the lee of burnt areas &gt; 600 km2, but a decrease by 0.1 mm on the domain average. © 2006 Elsevier B.V. All rights reserved."
"8978055900;","An integrated package for subgrid convection, clouds and precipitation compatible with meso-gamma scales",2007,"10.1002/qj.58","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249992030&doi=10.1002%2fqj.58&partnerID=40&md5=f8b02623e3b7d443ec29bafce1f8581f","The integration into a coherent package of the main 'moist' parametrizations - deep convection, resolved condensation, and microphysics - of a limited-area model is presented. The development of the package is aimed at solving efficiently the problem of combining 'resolved' and 'subgrid' condensation at all resolutions, in particular in the range between 10 km and 2 km where deep convection is partly resolved, partly subgrid. The different schemes of the package are called in cascade, with intermediate updating of internal variables, so that, for instance, the initial profiles passed to the deep-convection scheme are already balanced with respect to resolved condensation effects. Further on, the clean separation of the contributions to the closure of the updraught and downdraught from the initial vertical profile from which they evolve prevents double counting. The convective parametrization works with a prognostic mass-flux scheme, and acts on the resolved variables through condensation and convective transport. It detrains condensates that are added to the prognostic resolved condensates. A sensitivity study in a single-column model, and further validation in three-dimensional experiments at different resolutions, are presented. Copyright © 2007 Royal Meteorological Society."
"57194785789;7005202019;6602844274;","An empirical orthogonal function iteration approach for obtaining homogeneous radiative fluxes from satellite observations",2007,"10.1175/JAM2478.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249098666&doi=10.1175%2fJAM2478.1&partnerID=40&md5=a809272036a94c7743401bd775efca10","Conventional observations of climate parameters are sparse in space and/ or time, and the representativeness of such information needs to be optimized. Observations from satellites provide improved spatial coverage over point observations; however, they pose new challenges for obtaining homogeneous coverage. Surface radiative fluxes, the forcing functions of the hydrologic cycle and biogeophysical processes, are now becoming available from global-scale satellite observations. They are derived from independent satellite platforms and sensors that differ in temporal and spatial resolution and in the size of the footprint from which information is derived. Data gaps, degraded spatial resolution near boundaries of geostationary satellites, and different viewing geometries in areas of satellite overlap could result in biased estimates of radiative fluxes. In this study will be discussed issues related to the sources of inhomogeneity in surface radiative fluxes as derived from satellites, development of an approach to obtain homogeneous datasets, and application of the method to the widely used International Satellite Cloud Climatology Project data that currently serve as a source of information for deriving estimates of surface and top-of-the-atmosphere radiative fluxes. Introduced is an empirical orthogonal function (EOF) iteration scheme for homogenizing the fluxes. The scheme is evaluated in several ways, including comparison of the inferred radiative fluxes with ground observations, both before and after the EOF approach is applied. On the average, the latter reduces the RMS error by about 2-3 W m-2. © 2007 American Meteorological Society."
"7102389501;57196982444;","The impact of convective momentum transport on tropical cyclone track forecasts using the Emanuel cumulus parameterization",2007,"10.1175/MWR3365.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248343838&doi=10.1175%2fMWR3365.1&partnerID=40&md5=848bf9eb11f2bf1ef1cce3def68313c5","The influence of convective momentum transport (CMT) on tropical cyclone (TC) track forecasts is examined in the Navy Operational Global Atmospheric Prediction System (NOGAPS) with the Emanuel cumulus parameterization. Data assimilation and medium-range forecast experiments show that for 35 tropical cyclones during August and September 2004 the inclusion of CMT in the cumulus parameterization significantly improves the TC track forecasts. The tests show that the track forecasts are very sensitive to the magnitude of the Emanuel parameterization's convective momentum transport parameter, which controls the CMT tendency returned by the parameterization. While the overall effect of this formulation of CMT in NOGAPS data assimilation/ medium-range forecasts results in the surface pressure of tropical cyclones being less intense (and more consistent with the analysis), the parameterization is not equivalent to a simple diffusion of winds in the presence of convection. This is demonstrated by two data assimilation/ medium-range forecast tests in which a vertical diffusion algorithm replaces the CMT. Two additional data assimilation/medium-range forecast experiments were conducted to test whether the skill increase primarily comes from the CMT in the immediate vicinity of the tropical cyclones. The results show that the inclusion of the CMT calculation in the vicinity of the TC makes the largest contribution to the increase in forecast skill, but the general contribution of CMT away from the TC also plays an important role."
"7005206687;7004958888;","Observation and characterisation of rainfall over Hawaii and surrounding region from the Tropical Rainfall Measuring Mission",2007,"10.1002/joc.1414","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34047202674&doi=10.1002%2fjoc.1414&partnerID=40&md5=fbe6e2a407fe0c9cc0ba9ffa7052fb01","Satellite observations of clouds and precipitation have a history stretching back over 40 years. The observations of clouds initially led to the inference of precipitation from cloud top features and subsequently more direct methods derived from passive microwave observations. More recently, the Tropical Rainfall Measuring Mission (TRMM) has provided unprecedented information from the first active microwave instrument specifically designed to measure rainfall, the precipitation radar (PR). This paper utilises data from the TRMM PR for the period December 1997 to November 2005 to investigate rainfall over Hawaii and the surrounding ocean. The PR instrument not only provides spatial information on rainfall, but also vertical profiles of precipitation. Data from the PR instrument is used to map rainfall at a spatial resolution of 5 km and, utilising the information from the vertical profiles, map the distribution of trade-wind and non-trade-wind precipitation. This paper provides quantitative estimates of rainfall over Hawaii and the surrounding ocean that generally match those of surface observations and models. It is found that the islands exert a significant influence on the distribution of the amount and occurrence of precipitation over this region. Copyright © 2006 Royal Meteorological Society."
"7005719162;","Leaf water repellency of species in Guatemala and Colorado (USA) and its significance to forest hydrology studies",2007,"10.1016/j.jhydrol.2006.12.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847657895&doi=10.1016%2fj.jhydrol.2006.12.018&partnerID=40&md5=563997b3816fb08705ae0df2e7e96170","Fog persistency and high precipitation totals contribute to the unique ecohydrology of tropical montane cloud forests. The persistence of water droplets on leaf surfaces in cloud forests inhibits photosynthetic carbon exchange because carbon dioxide diffuses slower in water than air. Adaptations that reduce water retention on leaf surfaces may increase photosynthetic capacity of cloud forests. The objective of the present study was to determine if 12 cloud forest species from the Sierra de las Minas, Guatemala have a higher degree of leaf water repellency than 12 species from tropical dry forests in Chiquimula, Guatemala and 12 species from foothills-grassland vegetation in Colorado (USA). Leaf water repellency was measured as the contact angle between the leaf surface and the line tangent to the water droplet passing through the point of contact between the droplet and the leaf surface. Analysis of variance indicated that leaf water repellency was significantly different between the three study areas; however, the leaf water repellency of 12 species in the Sierra de las Minas was lower than 12 species in Chiquimula and lower than the leaf water repellency of 12 species in Colorado. Leaf water repellency of abaxial surfaces of all species in the cloud forest (Sierra de las Minas) was greater leaf water repellency of adaxial surfaces. The low values of leaf water repellency in cloud forest species may be influenced by presence of epiphylls or the loss of epicuticular wax on the leaf surfaces because of high precipitation totals and longer leaf life-span. High leaf water repellency in dry climates may be an adaptation to increase hydrological inputs underneath the canopy. © 2007 Elsevier B.V. All rights reserved."
"14626933400;7401785592;7005696150;13606897300;25630586700;14626579200;","Microclimatic responses to different thinning intensities in a Japanese cedar plantation of northern Taiwan",2007,"10.1016/j.foreco.2006.12.027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847248849&doi=10.1016%2fj.foreco.2006.12.027&partnerID=40&md5=41ddd82cb6fdf1c0b5b9777e0ec217a0","To assess the effects of thinning intensities on, and to reveal the temporal trends of, the short-term microclimates in a Japanese cedar (Cryptomeria japonica D. Don) plantation in a montane region of northern Taiwan, we monitored air and soil temperatures, air and soil temperature ranges, soil water potential, and ambient air water pressure deficit within the plantation over a 2-year period. The thinning experiment consisted of three thinning intensities (weak, moderate, and strong) and a control (unthinned). We used a set of semiparametric smoothing spline and linear mixed-effects models to analyze the monthly averages of the six variables. The results showed that the temporal trends of the six variables mainly reflected the regional climatic patterns during the study period and the topographic effects. Averaged over the 2-year period, the strongly thinned stand had significantly higher air and soil temperatures than that for the other three treatments. All the thinned stands had higher average air temperature ranges than that for the control, and the average of the strongly thinned stand was significantly higher than that for the other two thinning treatments. The air temperature ranges of the thinned stands, however, returned almost to the pre-thinning stage at the end of the monitoring period. For soil temperature range, the strongly thinned stand had a significantly higher average than that for the other three stands. Structural heterogeneity created by thinning also led to greater month-to-month variations in air and soil temperature ranges for the thinned stands. As a combination of thinning and its aspect, the moderately thinned stand had the highest soil water potential, followed by the strongly thinned stand. The thinned stands all had higher average soil water potential than for the control in a severe summer drought that occurred during the study period. For water vapor pressure deficit, no significant thinning effect was detected, probably because the study site was located within the cloud belt of northern Taiwan. This study has demonstrated that we can understand better how thinning truly affects microclimates by separating the influences that are due to higher-level climatic factors from those due to thinning. Implications of the effects of different thinning intensities were also addressed. © 2007 Elsevier B.V. All rights reserved."
"57202396417;7005170782;7003499257;","A simple diagnostic calculation of marine stratocumulus cloud cover for use in general circulation models",2007,"10.1029/2006JD007223","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249650584&doi=10.1029%2f2006JD007223&partnerID=40&md5=28bdbde3b7e65fd71459b419097acdfe","An improved diagnostic calculation for determining the marine stratocumulus (SCu) cloud cover has been implemented for atmospheric and coupled general circulation models (GCMs). The approach aims to improve the simulated climatological features of the lower troposphere and to reduce warm sea surface temperature (SST) biases that develop along western continental coasts in the subtropical regions of coupled GCMs. In the new diagnostic calculation introduced in the present study, the SCu cloud cover was linearly regressed to atmospheric stability, and the temporal and spatial distributions of the regression coefficients were estimated beforehand using observational data sets. The upward transport of heat, moisture and momentum in subcloud layers accompanying the SCu was also simulated by controlling the vertical diffusion coefficients. Using the new calculation, the SCu cloud cover in an atmospheric GCM become more representative in both spatial and seasonal variations. In addition, the simulation of related atmospheric structures in the lower troposphere is considerably improved. Furthermore, when the new calculation is applied to a coupled GCM, SST values to the west of continents in subtropical areas display weakened warm biases and more realistic seasonal cycles resulting from the modification of the downward shortwave radiation flux at the sea surface. The new calculation introduces both local and large-scale improvements in model climatology over low-latitude and midlatitude regions. In the eastern Pacific, for example, a shallow meridional circulation across the equator is excited, and the strength and location of the intertropical convergence zone and the seasonal cycle of equatorial SST become more realistic. Copyright 2007 by the American Geophysical Union."
"8211380400;7004857702;7501381728;7006461606;55624488227;8218839600;","Seasonal variability of NOx emissions over east China constrained by satellite observations: Implications for combustion and microbial sources",2007,"10.1029/2006JD007538","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249748246&doi=10.1029%2f2006JD007538&partnerID=40&md5=edb921e28df363fc32aedb1e807f338e","Observations of tropospheric column densities of NO2 obtained from the Global Ozone Monitoring Experiment (GOME) for a 3-year period (1997, 1998, and 2000) are used to derive average seasonal variations in surface emissions of NOx from east China (100-123°E, 20-42°N). The retrieval allows for zonal variations in the contribution of the stratosphere to the NO2 column and removes a bias of ±10% on the seasonality of retrieved columns introduced by cloud screening. The top-down inventory is constructed using an inversion approach with a global 3-D chemical transport model (GEOS-Chem) and combined subsequently with the a priori inventory to develop an a posteriori inventory. The contribution of background NO2 arising from nonsurface sources (lightning) and long-range transport of emissions originating outside of east China is accounted for in the inversion. The a posteriori estimate of overall emissions for east China, 4.66 Tg N/yr (±30% uncertainty), is 33% higher than the a priori value and is shown to improve agreement with surface measurements of nitrate wet deposition and concentrations of NOy observed in China. On the basis of multiple constraints on the spatial and seasonal variations of combustion and microbial processes, the a posteriori inventory is partitioned among emissions from biomass burning, fuel combustion, and microbial activity (or soil emissions). Emission of NOx from biomass burning in east China is estimated as 0.08 TgN/yr ± 50% in the a posteriori inventory, increased by about a factor of 2 from the a priori estimate. The resulting a posteriori inventory for fuel combustion (3.72 TgN/yr ± 32%) is about 15% higher than the a priori and exhibits a distinct maximum in winter, in contrast to the weak seasonality indicated in the a priori inventory. The a posteriori value for the microbial source of NOx (0.85 TgN/yr ± 40%) is about a factor of 3 higher than the a priori value, amounting to 23% of combustion sources for east China and significantly higher than a priori value of 7%. The microbial source is unimportant in winter. It peaks in summer, accounting for as much as 43% of the combustion source for that season, and is significant also in spring and fall. This seasonality is attributed to the timing of fertilizer application and to the influence of seasonally variable environmental factors including temperature and precipitation. Copyright 2007 by the American Geophysical Union."
"6603095001;16425142900;7102521545;","Climate change uncertainty for daily minimum and maximum temperatures: A model inter-comparison",2007,"10.1029/2006GL028726","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249908111&doi=10.1029%2f2006GL028726&partnerID=40&md5=9717ad44552a274eb633c790f6c435ef","Several impacts of climate change may depend more on changes in mean daily minimum (Tmin) or maximum (Tmax) temperatures than daily averages. To evaluate uncertainties in these variables, we compared projections of Tmin and Tmax changes by 2046-2065 for 12 climate models under an A2 emission scenario. Average modeled changes in Tmin were similar to those for Tmax with slightly greater increases in Tmin consistent with historical trends exhibiting a reduction in diurnal temperature ranges. In contrast, the inter-model variability of Tmin and Tmax projections exhibited substantial differences. For example, inter-model standard deviations of June-August Tmax changes were more than 50% greater than for Tmin throughout much of North America, Europe, and Asia. Model differences in cloud changes, which exert relatively greater influence on Tmax during summer and Tmin during winter, were identified as the main source of uncertainty disparities. These results highlight the importance of considering separately projections for Tmax and Tmin when assessing climate change impacts, even in cases where average projected changes are similar. In addition, impacts that are most sensitive to summertime Tmin or wintertime Tmax may be more predictable than suggested by analyses using only projections of daily average temperatures. Copyright 2007 by the American Geophysical Union."
"16425297500;55915206300;","Vertical structure of stratiform marine boundary layer clouds and its impact on cloud albedo",2007,"10.1029/2006GL028713","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249895564&doi=10.1029%2f2006GL028713&partnerID=40&md5=351356ce09bab916cb03e325ff2b79ad","One year of passive microwave as well as near infrared remote sensing observations of cloud liquid water path (LWP) are used to study stratiform marine boundary layer clouds on a large scale. Good agreement between the two different remote sensing estimates of LWP was found for values below 150 g/m2, if the clouds were assumed to be stratified vertically. For higher values of LWP the near infrared observations show a lower LWP than the passive microwave observations. Theoretical calculations of cloud albedo suggest a potentially significant underestimation of cloud albedo if, for a given LWP, clouds are assumed to be vertically homogeneous. The results presented in this study bear significance especially for climate studies. Of particular relevance is the conclusion that also at the large scale marine boundary layer clouds need to be regarded as being vertically adiabatically or sub-adiabatically stratified. Copyright 2007 by the American Geophysical Union."
"7006758502;6508170572;6602633306;7005862984;7006393267;","Observed and simulated microphysical composition of arctic clouds: Data properties and model validation",2007,"10.1029/2006JD007351","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548554573&doi=10.1029%2f2006JD007351&partnerID=40&md5=1f8347671b42b2becde4b25759ceaa2a","Data from two different sensors measuring ice particles were combined to establish an improved data series for ice water content. Together with liquid water measurements this new data set was used to evaluate arctic cloud properties, simulated with a state-of-the-art mesoscale atmospheric model. Dependent on the method used for comparison, the mean cloud fraction was found to lie between 51 and 58% in the observations and 53% in the simulations. The hit rate for the total water content was estimated to be between 65 and 71% and the systematic error to a few percent. On the basis of in-cloud observations only, the model was able to reproduce cloudy conditions in 74% of the data points. On the other hand, the model underestimated the occurrence of the liquid phase by about 80% and slightly overestimated the occurrence of the ice phase. Also, in the temperature range from 255 K to 230 K, where considerable amounts of supercooled water were observed, the model failed to produce the liquid phase. Our results confirm the previous finding that despite high forecast skill with respect to cloudy or cloud-free events, the model underpredicts the occurrence of liquid phase in arctic clouds. This shortcoming will have a large influence on precipitation forecasts, as well as on climate predictions. Despite some improvements in recent years, more research is needed to improve the parameterization of arctic cloud properties in fine-scale weather prediction models. For climate models, which have to employ a much cruder parameterization of the microphysics, we face a number of challenges. Copyright 2007 by the American Geophysical Union."
"8619284000;7101647346;55734348395;6506986541;6602652380;","The impact of changes in the weather on the surface temperatures of Lake Windermere (UK) and Lough Feeagh (Ireland)",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947098615&partnerID=40&md5=665f1f8170d0b9896810bcb4b12fd23c","The surface temperatures of Lake Windermere (UK) and Lough Feeagh (Ireland) have been recorded every day since 1960. Here, we examine the factors influencing these measurements and their associated weekly variability. At both sites there was a progressive increase in the measured temperature, but the rate of increase was very much greater in Lake Windermere. The variance of the Lake Windermere temperatures was negatively correlated with the cloud cover, but there was no corresponding relationship in Lough Feeagh. Comparisons with the Lamb system of weather classification showed that the lake temperatures were closely correlated with these synoptic conditions. The highest winter temperatures were recorded during ""westerly"" conditions and the highest summer temperatures under ""southerly"" conditions. The most striking difference between the lakes was their response to cold winters and windy summers. Such results demonstrate that lakes that are topographically different ""filter"" the imposed climate signal in subtly different ways. Copyright © 2007 IAHS Press."
"6701324864;7202162685;","Refinements to the Köhler's theory of aerosol equilibrium radii, size spectra, and droplet activation: Effects of humidity and insoluble fraction",2007,"10.1029/2006JD007672","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548557633&doi=10.1029%2f2006JD007672&partnerID=40&md5=2db9a31e8c22d15b7807e5140f290618","Hygroscopic growth of mixed aerosol particles and activation of cloud condensation nullcei (CCN) are considered using Köhler theory without the assumption of a dilute solution and accounting for the effect of insoluble fraction. New analytical expressions are derived for the equilibrium wet radius of the wet aerosol and for the critical radii and supersaturations for CCN activation for both volume-distributed soluble fraction and a soluble shell on the surface of an insoluble core (e.g., mineral dust particle). These expressions generalize the known equations of the Köhler theory, and the accuracy and applicability of the classical expressions are clarified. On the basis of these new expressions, a general but simple method is derived for calculation of the wet size spectrum and the CCN activity spectrum from the dry aerosol size spectrum. The method is applicable for any arbitrary shape of the dry aerosol spectra. Some applications for evaluation of aerosol extinction and homogeneous ice nucleation in a polydisperse aerosol are briefly considered. The method described here can be used in cloud and climate models, in particular, for evaluation of the aerosol direct and indirect effects. Copyright 2007 by the American Geophysical Union."
"12763470600;6602729528;35561911800;7004540083;6604021707;7601318782;","20th century changes in surface solar irradiance in simulations and observations",2007,"10.1029/2006GL028356","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249872464&doi=10.1029%2f2006GL028356&partnerID=40&md5=5a283f8f03d5cb370337e1afe8ac6215","The amount of solar irradiance reaching the surface is a key parameter in the hydrological and energy cycles of the Earth's climate. We analyze 20th Century simulations using nine state-of-the-art climate models and show that all models estimate a global annual mean reduction in downward surface solar radiation of 1-4 W/m2 at the same time that the globe warms by 0.4-0.7°C. In single forcing simulations using the GISS-ER model, this ""global dimming"" signal is shown to be predominantly related to aerosol effects. In the global mean sense the surface adjusts to changes in downward solar flux instantaneously by reducing the upward fluxes of longwave, latent and sensible heat. Adding increased greenhouse gas forcing traps outgoing longwave radiation in the atmosphere and surface which results in net heating (although reduced) that is consistent with global warming over the 20th Century. Over the 1984-2000 period, individual model simulations show widely disparate results, mostly related to cloud changes associated with tropical Pacific variations, similar to the changes inferred from the satellite data analysis. This suggests that this time period is not sufficient to determine longer term trends. Copyright 2007 by the American Geophysical Union."
"23987195100;23009967300;55435365800;","Comparison of models for calculating daytime long-wave irradiance using long term data set",2007,"10.1016/j.agrformet.2006.11.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846794475&doi=10.1016%2fj.agrformet.2006.11.007&partnerID=40&md5=da1e5d858c7f067fca79c351a40ddc3e","Twenty simple and widely used models for calculating clear sky daytime long-wave irradiance were tested against measured long-wave irradiance data. As input the models required only air temperature or air temperature and water vapour pressure, all measured at screen height. Meteorological data and long-wave irradiance measurements from 32 consecutive years at the Climate and Water Balance Station at Taastrup in eastern Denmark and from 7 consecutive years at the Agrometeorological Station at Foulum in western Denmark were used. The long time series of the data sets ensured all weather conditions and extreme events were captured. Clear sky conditions were assumed when the ratio of measured global radiation at the surface to the extraterrestrial exceeded approximately 0.75. A set of statistical procedures was used to evaluate the performance of the models. The mean bias errors ranged from -23 to +12 W m-2 and -18 to +15 W m-2 and root mean square errors from 39 to 45 W m-2 and 30-36 W m-2 in Taastrup and Foulum, respectively. Model performance improved when using average daily daytime clear sky data and a more strict definition of clear sky conditions. No improvements were found when the data sets were subdivided by season or upwind surface cover type. Four of the clear sky models were superior to the other models tested. These models were combined with two all sky daytime long-wave irradiance models and compared to actual all sky daytime long-wave irradiance data included in the Foulum and Taastrup data sets. The mean bias errors ranged from -8 to +5 W m-2 and -6 to +8 W m-2 and root mean square errors from 29 to 30 W m-2 and 23-24 W m-2 in Taastrup and Foulum, respectively. Based on the results of this study and the fact that the Prata and Brutsaert clear sky models were founded on a physical basis these models were recommended for use with the Crawford and Duchon all sky model when calculating daytime long-wave irradiance in a temperate climate. © 2006 Elsevier B.V. All rights reserved."
"7407182375;6603779272;57203052274;7202175203;6601992794;7006550762;","Why are there large differences between models in global budgets of tropospheric ozone?",2007,"10.1029/2006JD007801","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847187654&doi=10.1029%2f2006JD007801&partnerID=40&md5=e86e0756938110a963faba405640f5b6","Global 3-D tropospheric chemistry models in the literature show large differences in global budget terms for tropospheric ozone. The ozone production rate in the troposphere, P(O<inf>x</inf>,), varies from 2300 to 5300 Tg yr-1 across models describing the present-day atmosphere. The ensemble mean of P(O<inf>x</inf>) in models from the post-2000 literature is 35% higher than that compiled in the Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report (TAR). Simulations conducted with the GEOS-Chem model using two different assimilated meteorological data sets for 2001 (GEOS-3 and GEOS-4), as well as 3 years of GISS GCM meteorology, show P(O<inf>x</inf>) values in the range 4250-4700 Tg yr-1; the differences appear mostly because of clouds. Examination of the evolution of P(Q<inf>x</inf>) over the GEOS-Chem model history shows major effects from changes in heterogeneous chemistry, the lightning NO<inf>x</inf> source, and the yield of organic nitrates from isoprene oxidation. Multivariate statistical analysis of model budgets in the literature indicates that 74% of the variance in P(O<inf>x</inf>) across models can be explained by differences in NO<inf>x</inf> emissions, inclusion of nonmethane volatile organic compounds (NMVOCs, mostly biogenic isoprene), and ozone influx from stratosphere-troposphere exchange (STE). Higher NO<inf>x</inf> emissions, more widespread inclusion of NMVOC chemistry, and weaker STE in the more recent models increase ozone production; however, the effect of NMVOCs does not appear generally sensitive to the magnitude of emissions within the range typically used in models (500-900 Tg C yr-1). We find in GEOS-Chem that P(O<inf>x</inf>) saturates when NMVOC emissions exceed 200 Tg C yr-1 because of formation of organic nitrates from isoprene oxidation, providing an important sink for NO<inf>x</inf>. Copyright 2007 by the American Geophysical Union."
"7201637089;7401491382;","The relative importance of clouds and sea ice for the solar energy budget of the Southern Ocean",2007,"10.1175/JCLI4040.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34147117319&doi=10.1175%2fJCLI4040.1&partnerID=40&md5=95c2ba24875cefa6bccb48bb4a2df668","The effects of clouds and sea ice on the solar radiation budget are determined for the Southern Ocean around Antarctica between latitudes 50° and 80°S. Distributions of cloud optical depth are used, together with distributions of surface albedo, to estimate the geographical and seasonal variations of shortwave irradiance and cloud radiative forcing at the surface, both for the present climate and for altered surface and cloud conditions. Poleward of 68°S in spring, ice causes a greater reduction of solar energy input to the surface than does cloud. However, in summer the clouds are more important than ice at all latitudes in the Southern Ocean. In the present climate the clouds are optically thicker over open water than over sea ice, suggesting a possible negative feedback if the sea ice area shrinks with climatic warming. Compared to the present climate in spring, removing sea ice results in an increase in irradiance reaching the ocean surface, regardless of the type of cloud remaining. However, in summer the removal of ice results in higher irradiance at the surface only if clouds remain unchanged. If clouds become as thick as those presently over the ocean at 55°-60°S, irradiance reaching the ocean surface in summer decreases poleward of 65°S. © 2007 American Meteorological Society."
"7102989499;6602136577;55383124200;","Multi-angle geometric processing for globally geo-located and co-registered MISR image data",2007,"10.1016/j.rse.2006.08.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846905957&doi=10.1016%2fj.rse.2006.08.013&partnerID=40&md5=62874ddd02d6bbcaf4984e48d7a7cda6","This paper focuses on the high accuracy geo-location and co-registration performance operationally obtained for the Multi-angle Imaging SpectroRadiometer (MISR) data via a robust production algorithm. The MISR instrument (which is part of the payload for NASA's Terra spacecraft) continuously acquires systematic, global, multi-angle imagery in reflected sunlight since it was launched in December 1999, with the objective of supporting ecology and climate studies. The moderate resolution data need to be autonomously geo-rectified prior to being used in subsequent scientific retrievals. This is particularly critical to the unique cloud height/wind retrievals which require sub-pixel co-registration accuracies on a global basis. In order to address this problem, the MISR ground data processing system is based on a fully photogrammetric approach and is complemented with a quality monitoring system used to verify performance globally and over desired time periods. The geo-rectification requirements were developed from a series of data quality investigations based partially on sensitivity requirements for the cloud height/wind retrieval algorithm. An update to the nominal production algorithm has been implemented, and the final operational results are presented in this paper. © 2006 Elsevier Inc. All rights reserved."
"7403681584;7404211378;","Cloud-SST feedback in southeastern tropical Atlantic anomalous events",2007,"10.1029/2006JC003626","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249731906&doi=10.1029%2f2006JC003626&partnerID=40&md5=09059bb61692e7d89ed6191ab875e5f8","Using satellite-based cloud measurements for 1984-2004, the interannual variability of the low-level cloud cover over the tropical Atlantic Ocean in austral winter (June-July-August, JJA) is examined. It is found that the leading pattern of the low-cloud anomalies in this season is a modulation of the climatological center of the cloud cover over the southeastern tropical Atlantic Ocean off the Angola and Namibia coasts. The fluctuation of cloud amount there occurs on both interannual and longer timescales. The relationship between this low-cloud anomalous pattern and basinwide ocean-atmosphere anomalies is studied through a composite analysis based on the objectively selected major low-cloud deficit and excess years. For the composites we intentionally use data sets mainly based on satellite measurements for the past one to two decades to minimize the potential influences of the bias in the model-based ocean-atmosphere analyses. The composites show that the JJA anomalous cloud pattern is strongly influenced by the sea surface temperature (SST) anomalies of the equatorial and southeastern tropical Atlantic Ocean in the previous summer. The anomalous surface warm events off the southwestern coast of Africa near 15°S in January and February are usually initiated dynamically by remote forcing from the westerly wind anomalies over the western equatorial Atlantic, preceding the cloud anomalies. During the next few months, the warm water is spread into the southeastern tropical Atlantic Ocean and is conducive to deficit low-cloud cover in subsequent JJA. The reduced low-cloud cover in turn forces positive SST tendency in a larger area of the southeastern Atlantic Ocean by changing the amount of the local solar radiation reaching the sea surface. In June and July, this process moves the major center of the SST anomalies away from the coast and closer to the equator when the coastal process weakens. The low cloud-radiation-SST feedback also plays a role in the slow westward expansion of the SST anomalies in late austral winter and spring. Overall, the influence of the cloud fluctuation is an important component in the evolution of the southeastern tropical Atlantic anomalous events. Copyright 2007 by the American Geophysical Union."
"7004201700;7402363038;7102403008;","Origin of climate sensitivity differences: Role of selected radiative processes in two GCMs",2007,"10.1111/j.1600-0870.2006.00224.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247601523&doi=10.1111%2fj.1600-0870.2006.00224.x&partnerID=40&md5=a8427e1362cdf74cf0bafd5e52c9a4d5","Model differences in projections of global mean and regional climate change due to increasing greenhouse gases are investigated using two atmospheric general circulation models (AGCMs): ECHAM4 (Max Planck Institute, version 4) and CCM3 (National Center for Atmospheric Research Community Climate Model version 3). We replace the ECHAM4 short-wave processes (including routines for short-wave radiation, aerosols, cloud liquid water path and cloud droplet size distribution) with the corresponding parametrizations from CCM3. We also eliminate sea-ice in both models. We find that the resulting 'hybrid'-ECHAM4 model has the same global mean temperature sensitivity (defined as the difference in temperature between the 2 × CO2 and 1 × CO2 integrations at equilibrium) and similar regional temperature change patterns as CCM3. The global mean precipitation sensitivity was only slightly affected; indicating different processes control this. Investigation of top of the atmosphere radiative feedbacks in the standard-ECHAM4 and hybrid-ECHAM4 models show that the differences in global mean temperature sensitivity and regional temperature change patterns can be attributed primarily to a stronger, negative, cloud short-wave feedback in the tropics of the hybrid-ECHAM4 model. However, comparison of the hybrid-ECHAM4 model to CCM3 reveals large differences in partitioning of the cloud feedbacks between long-wave and short-wave in the two models. This suggests that the global mean temperature sensitivity and regional temperature change patterns respond primarily to the magnitude and distribution of the top of the atmosphere feedbacks and are relatively insensitive to the partitioning between individual processes. © 2007 The Authors Journal compilation © 2007 Blackwell Munksgaard."
"34879764000;7006377579;9044151600;","Our changing atmosphere",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249824585&partnerID=40&md5=e417fcfe3fc027e064164421d1c15882","In order to look at very specific areas of atmospheric chemistry and physics in an attempt to quantify the effects of greenhouse gases and other pollutants on the climate and air quality, the NERC (Natural Environment Research Council) invested in four research programs. In order to examine the causes for mid-latitude ozone changes in the past and for the future, NERC set up the Upper Troposphere Lower Stratosphere Ozone program. It showed that pollution can traverse continents, in the case of the study, from the US eastern seaboard to Europe. NERC also had the Clouds, Water Vapor and Climate program which determined the physical processes that determine humidity distribution and cloud structure. The program found out that large number of aerosols entering through the base of the cloud can influence intense thunderstorms and substantially change the ability of the clouds to scatter sunlight. NERC's Core Strategic Measurements in Atmospheric Science program demonstrated the importance of continuing laboratory experiments, developing new instruments and data acquisition."
"15828928500;57211106013;56472932500;","Sensitivity of ozone to summertime climate in the eastern USA: A modeling case study",2007,"10.1016/j.atmosenv.2006.10.033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846460448&doi=10.1016%2fj.atmosenv.2006.10.033&partnerID=40&md5=ab7d679e776af7718eb8abee1d48e6ff","The goal of this modeling study is to determine how concentrations of ozone respond to changes in climate over the eastern USA. The sensitivities of average ozone concentrations to temperature, wind speed, absolute humidity, mixing height, cloud liquid water content and optical depth, cloudy area, precipitation rate, and precipitating area extent are investigated individually. The simulation period consists of July 12-21, 2001, during which an ozone episode occurred over the Southeast. The ozone metrics used include daily maximum 8 h average O3 concentration and number of grid cells exceeding the US EPA ambient air-quality standard. The meteorological factor that had the largest impact on both ozone metrics was temperature, which increased daily maximum 8 h average O3 by 0.34 ppb K-1 on average over the simulation domain. Absolute humidity had a smaller but appreciable effect on daily maximum 8 h average O3 (-0.025 ppb for each percent increase in absolute humidity). While domain-average responses to changes in wind speed, mixing height, cloud liquid water content, and optical depth were rather small, these factors did have appreciable local effects in many areas. Temperature also had the largest effect on air-quality standard exceedances; a 2.5 K temperature increase led to a 30% increase in the area exceeding the EPA standard. Wind speed and mixing height also had appreciable effects on ozone air-quality standard exceedances. © 2006 Elsevier Ltd. All rights reserved."
"8870516000;6506724200;7006928297;6603364878;7006329385;","Meteorological conditions and polar stratospheric clouds over Yakutsk in winter 2004/05",2007,"10.3103/S1068373907030053","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548294216&doi=10.3103%2fS1068373907030053&partnerID=40&md5=9fe8fcbdacc72fe3899be717f2e5b9d2","Regular observations of polar stratospheric clouds were started at a lidar stratospheric station in the city of Yakutsk. According to lidar measurements in the winter of 2004/05, thick aerosol layers in the lower stratosphere appeared over this region quite frequently. They were episodically observed as pearl clouds. In November 2004, polar stratospheric clouds were observed at the stratospheric temperatures that were much higher than those at which particles of the polar stratospheric clouds could condense. Analysis of air-mass trajectories that simultaneously passed over Yakutsk at different altitudes on the days of polar stratospheric cloud observations showed that clouds could be formed over the Norwegian Sea at altitudes of about 18-21 km, where the stratosphere was the coldest, and then were transported to Yakutsk by wind during 4-5 days. © Allerton Press, Inc. 2007."
"14523673200;7202205546;","Daily NDVI relationship to cloud cover",2007,"10.1175/JAM2468.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247598865&doi=10.1175%2fJAM2468.1&partnerID=40&md5=5ebd0eed8d137a5749587020fbed99b1","A normalized difference vegetation index (NDVI) cloud index (NCI) was derived from Pathfinder Advanced Very High Resolution Radiometer (AVHRR) daily NDVI data and compared with observed cloud amounts and a sunshine duration-cloud index (SCI) over an area of diverse land cover. Ground observations from 120 meteorological stations were significantly related to the daily NCI and the SCI, with R2 values of 0.41 and 0.50, respectively. The daily NCI and interpolated cloud indices derived from ground observations over the 776 900 km2 study area were compared. The correlation coefficient between the NCI and the observed cloud amount was less than 0.6 for less than 20% of the area. The correlation coefficient between the NCI and the observed sunshine duration index was less than 0.6 for less than 10% of the area and less than 0.7 for 41% of the area. There were strong correlations for high elevations in summer, and correlations for low elevations in winter were weaker. A frozen soil surface or snow cover degrades the NDVI relationship to clouds. The NCI and observed cloud indices had high correlation coefficients in areas with diverse land uses, suggesting that the NCI may be useful in estimating cloudiness over a large region. © 2007 American Meteorological Society."
"6603262933;6602805181;6602135743;6505895769;6504536362;7003739558;","Characteristics of atmospheric aerosol during the anomalous fall of 2005 in the Moscow region",2007,"10.3103/S106837390703003X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548277495&doi=10.3103%2fS106837390703003X&partnerID=40&md5=3ba645f85ed450c7f6b28e72d228ca43","Results are presented of measurements of total concentration and size spectrum of aerosol particles, of ice nuclei, and cloud condensation nuclei concentrations, as obtained during an anomalously arid period in September and October 2005 in the town of Dolgoprudny, Moscow oblast. It is shown that a two-month period of anticyclonic weather, associated with peat fires, caused a 1.5-time increase in the mean number concentration of aerosol at the site. Effects of accumulation of the industrial aerosol from Moscow and of peat bog burning products are different on fractions of particles of different sizes and on cloud-active nuclei. The smoke particles increased concentrations of almost all sizes from 0.042 to 10 μm; urban aerosol makes the greater part of concentration of particles in the middle subm-icron range and causes a significant increase in the concentration of cloud condensation nuclei. © Allerton Press, Inc. 2007."
"7403282069;7403531523;7004325649;7202926455;7403508241;7801693068;6701835010;","Statistical analyses of satellite cloud object data from CERES. Part II: Tropical convective cloud objects during 1998 El Niño and evidence for supporting the fixed anvil temperature hypothesis",2007,"10.1175/JCLI4069.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947403250&doi=10.1175%2fJCLI4069.1&partnerID=40&md5=d17e27ee54fe0c2f230b3296bdbf74ef","Characteristics of tropical deep convective cloud objects observed over the tropical Pacific during January-August 1998 are examined using the Tropical Rainfall Measuring Mission/Clouds and the Earth's Radiant Energy System Single Scanner Footprint (SSF) data. These characteristics include the frequencies of occurrence and statistical distributions of cloud physical properties. Their variations with cloud object size, sea surface temperature (SST), and satellite precession cycle are analyzed in detail. A cloud object is defined as a contiguous patch of the earth composed of satellite footprints within a single dominant cloud-system type. It is found that statistical distributions of cloud physical properties are significantly different among three size categories of cloud objects with equivalent diameters of 100-150 (small), 150-300 (medium), and >300 km (large), except for the distributions of ice particle size. The distributions for the larger-size category of cloud objects are more skewed toward high SSTs, high cloud tops, low cloud-top temperature, large ice water path, high cloud optical depth, low outgoing longwave (LW) radiation, and high albedo than the smaller-size category. As SST varied from one satellite precession cycle to another, the changes in macrophysical properties of cloud objects over the entire tropical Pacific were small for the large-size category of cloud objects, relative to those of the small- and medium-size categories. This evidence supports the fixed anvil temperature hypothesis of Hartmann and Larson for the large-size category. Combined with the result that a higher percentage of the large-size category of cloud objects occurs during higher SST subperiods, this implies that macrophysical properties of cloud objects would be less sensitive to further warming of the climate. On the other hand, when cloud objects are classified according to SST ranges, statistical characteristics of cloud microphysical properties, optical depth, and albedo are not sensitive to the SST, but those of cloud macrophysical properties are dependent upon the SST. This result is related to larger differences in large-scale dynamics among the SST ranges than among the satellite precession cycles. Frequency distjributions of vertical velocity from the European Centre for Medium-Range Weather Forecasts model that is matched to each cloud object are used to further understand some of the findings in this study. © 2007 American Meteorological Society."
"7101752236;7103271625;7103242280;","Nucleation processes in deep convection simulated by a cloud-system-resolving model with double-moment bulk microphysics",2007,"10.1175/JAS3869.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34147137273&doi=10.1175%2fJAS3869.1&partnerID=40&md5=5a69d8783b3433de6c86461e3d56ef55","A novel type of limited double-moment scheme for bulk microphysics is presented here for cloud-system-resolving models (CSRMs). It predicts the average size of cloud droplets and crystals, which is important for representing the radiative impact of clouds on the climate system. In this new scheme, there are interactive components for ice nuclei (IN) and cloud condensation nuclei (CCN). For cloud ice, the processes of primary ice nucleation, Hallett-Mossop (HM) multiplication of ice particles (secondary ice production), and homogeneous freezing of aerosols and droplets provide the source of ice number. The preferential evaporation of smaller droplets during homogeneous freezing of cloud liquid is represented for the first time. Primary and secondary (i.e., in cloud) droplet nucleation are also represented, by predicting the supersaturation as a function of the vertical velocity and local properties of cloud liquid. A linearized scheme predicts the supersaturation, explicitly predicting rates of condensation and vapor deposition onto liquid (cloud liquid, rain) and ice (cloud ice, snow, graupel) species. The predicted supersaturation becomes the input for most nucleation processes, including homogeneous aerosol freezing and secondary droplet activation. Comparison of the scheme with available aircraft and satellite data is performed for two cases of deep convection over the tropical western Pacific Ocean. Sensitivity tests are performed with respect to a range of nucleation processes. The HM process of ice particle multiplication has an important impact on the domain-wide ice concentration in the lower half of the mixed-phase region, especially when a lack of upper-level cirrus suppresses homogeneous freezing. Homogeneous freezing of droplets and, especially, aerosols is found to be the key control on number and sizes of cloud particles in the simulated cloud ensemble. Preferential evaporation of smaller droplets during homogeneous freezing produces a major impact on ice concentrations aloft. Aerosols originating from the remote free troposphere become activated in deep convective updrafts and produce most of the supercooled cloud droplets that freeze homogeneously aloft. Homogeneous aerosol freezing is found to occur only in widespread regions of weak ascent while homogeneous droplet freezing is restricted to deep convective updrafts. This means that homogeneous aerosol freezing can produce many more crystals than homogeneous droplet freezing, if conditions in the upper troposphere are favorable. These competing mechanisms of homogeneous freezing determine the overall response of the ice concentration to environmental CCN concentrations in the simulated cloud ensemble. The corresponding sensitivity with respect to environmental IN concentrations is much lower. Nevertheless, when extremely high concentrations of IN are applied, that are typical for plumes of desert dust, the supercooled cloud liquid is completely eliminated in the upper half of the mixed phase region. This shuts down the process of homogeneous droplet freezing. © 2007 American Meteorological Society."
"7201504886;7004461962;6602761005;13411455700;56865378100;7103119050;16178543600;9132948500;","On the structure of the lower troposphere in the summertime stratocumulus regime of the northeast Pacific",2007,"10.1175/MWR3427.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34047194872&doi=10.1175%2fMWR3427.1&partnerID=40&md5=64d328b18070b586b6ae091a35ac1d55","Data collected in situ as part of the second field study of the Dynamics and Chemistry of Marine Stratocumulus field program are used to evaluate the state of the atmosphere in the region of field operations near 30°N, 120°W during July 2001, as well as its representation by a variety of routinely available data. The routine data include both the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and NCEP-NCAR reanalyses, forecasts from their respective forecast systems (the Integrated and Global Forecast Systems), the 30-km archive from the International Satellite Cloud Climatology Project (ISCCP), the Quick Scatterometer surface winds, and remotely sensed fields derived from radiances measured by the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), the Advanced Microwave Sounding Unit, and the Advanced Very High Resolution Radiometer. The analysis shows that outside of the boundary layer the state of the lower troposphere is reasonably represented by the reanalysis and forecast products, with the caveat of a slight warm bias at 850 hPa in the NCEP-NCAR products. Within the planetary boundary layer (PBL) the agreement is not as good: both the boundary layer depth and cloud amount are underpredicted, and the boundary layer temperature correlates poorly with the available data, which may be related to a poor representation of SSTs in this region of persistent cloud cover. ERA-40 also suffers from persistently weak zonal winds within the PBL. Among the satellite records the ISCCP data are found to be especially valuable, evincing skill in both predicting boundary layer depth (from cloud-top temperatures and TMI surface temperatures) and cloud liquid water paths (from cloud optical depths). An analysis of interannual variability (among Julys) based on ERA-40 and the 1983-2001 ISCCP record suggests that thermodynamic quantities show similar interannual and synoptic variability, principally concentrated just above the PBL, while dynamic quantities vary much more on synoptic time scales. Furthermore, the analysis suggests that the correlation between stratocumulus cloud amount and lower-tropospheric stability exhibits considerable spatial structure and is less pronounced than previously thought. © 2007 American Meteorological Society."
"57205342499;7401699378;57201725986;","Effects of salinity on long-term tropical atmospheric and oceanic variability",2007,"10.1016/j.atmosres.2006.07.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846886352&doi=10.1016%2fj.atmosres.2006.07.002&partnerID=40&md5=a44fb7c3ef116f8e5baee2317c96fde7","The effects of salinity on long-term tropical atmospheric and oceanic variability are investigated using a pair of two-dimensional coupled ocean-cloud resolving atmosphere simulations. A zero vertical velocity and a constant zonal wind are imposed in cloud resolving atmosphere model. The experiment with salinity is compared to the experiment without salinity. The model is integrated for 51 days. The comparison between the experiments with and without salinity effects shows negative differences in ocean mixed-layer temperature and precipitable water as well as positive differences in atmospheric temperature. The budgets of ocean mixed-layer heat and atmospheric mass-weighted mean temperature and precipitable water are analyzed. The ocean thermal forcing and thermal entrainment determine the negative difference in the mixed-layer temperature. Surface evaporation and condensation are responsible for the negative precipitable water difference whereas radiative heating and latent heat account for the positive air temperature difference. © 2006 Elsevier B.V. All rights reserved."
"15843952300;7005336675;","Genetic patterns in Podocarpus parlatorei reveal the long-term persistence of cold-tolerant elements in the southern Yungas",2007,"10.1111/j.1365-2699.2006.01613.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846923324&doi=10.1111%2fj.1365-2699.2006.01613.x&partnerID=40&md5=64c14be6a6dbd6d336c9d32b4197a0df","Aim: This study analyses long-term responses to climate changes in Podocarpus parlatorei, a cold-tolerant tree species from the subtropics in South America, using distribution patterns of isozyme variation. Location: Podocarpus parlatorei characterizes montane forests within the Yungas, a cloud forest of the subtropics of north-western Argentina and southern Bolivia. Podocarpus parlatorei consists of disjunct populations ecologically subdivided into northern, central, and southern sectors that we predict will be genetically divergent from one another as a result of historical isolation. Methods: We collected fresh leaves from a maximum of 30 randomly selected individuals from each of 18 populations. We resolved 25 isozyme loci, and scored the most consistent 14, 57% of which were polymorphic. Within-population variation was tested against latitude, longitude, and elevation using multiple regressions. Genetic structure across populations was analysed using diversity parameters. The relationship between genetic and geographic distances was explored with reference to Pearson correlation coefficients. Results: The effective number of alleles and observed heterozygosity increase latitudinally. Southern populations tend to be the most variable and genetically distinct. This result suggests that they could represent the location of a long-term refuge for P. parlatorei. The mean number of alleles per locus decreases with elevation. The total genetic diversity is HT = 0.163, 10% of which is distributed among populations. A positive association between genetic and geographic distances was detected. Main conclusions: Reductions in genetic diversity towards the north and high-elevation mountains are consistent with evidence of patterns of forest migration resulting from climate change during the Late Quaternary, northern expansion during episodes of cooling, and range contraction towards the highlands during warming trends. Naturally disjunct populations of P. parlatorei are genetically divergent from one another, indicating that local genetic stocks should be used for restoration of degraded habitats. © 2007 The Authors Journal compilation 2007 Blackwell Publishing Ltd."
"8576228100;8976327600;11038770400;10140927300;13403810300;","Uniform growth trends among central Asian low- and high-elevation juniper tree sites",2007,"10.1007/s00468-006-0104-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847317941&doi=10.1007%2fs00468-006-0104-0&partnerID=40&md5=f9bd44441df92b6ca57bf62b984ccfe9","We present an analysis of 28 juniper tree-ring sites sampled over the last decades by several research teams in the Tien Shan and Karakorum mountains of western central Asia. Ring-width chronologies were developed on a site-by-site basis, using a detrending technique designed to retain low-frequency climate variations. Site chronologies were grouped according to their distance from the upper timberline in the Tien Shan (∼ 3,400 m a.s.l.) and Karakorum ((∼ 4,000 m), and low- and high-elevation composite chronologies combining data from both mountain systems developed. Comparison of these elevational subsets revealed significant coherence ((r = 0.72) over the 1438-1995 common period, which is inconsistent with the concept of differing environmental signals captured in tree-ring data along elevational gradients. It is hypothesized that the uniform growth behavior in central Asian juniper trees has been forced by solar radiation variations controlled via cloud cover changes, but verification of this assumption requires further fieldwork. The high-elevation composite chronology was further compared with existing temperature reconstructions from the Karakorum and Tien Shan, and long-term trend differences discussed. We concluded that the extent of warmth during medieval times cannot be precisely estimated based on ring-width data currently available. © 2006 Springer-Verlag."
"57218273453;56962915800;7601492669;57202299549;","Improvements in climate simulation with modifications to the Tiedtke convective parameterization in the grid-point atmospheric model of IAP LASG (GAMIL)",2007,"10.1007/s00376-007-0323-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248683260&doi=10.1007%2fs00376-007-0323-3&partnerID=40&md5=cfc0e41083f15135dabb1d2413b34166","The grid-point atmospheric model of IAP LASG (GAMIL) was developed in and has been evaluated since early 2004. Although the model shows its ability in simulating the global climate, it suffers from some problems in simulating precipitation in the tropics. These biases seem to result mainly from the treatment of the subgrid scale convection, which is parameterized with Tiedtke's massflux scheme (or the Zhang-McFarlane scheme, as an option) in the model. In order to reduce the systematic biases, several modifications were made to the Tiedtke scheme used in GAMIL, including (1) an increase in lateral convective entrainment/ detrainment rate for shallow convection, (2) inclusion of a relative humidity threshold for the triggering of deep convection, and (3) a reduced efficiency for the conversion of cloud water to rainwater in the convection scheme. Two experiments, one with the original Tiedtke schem e used in GAMIL and the other with the modified scheme, were conducted to evaluate the performance of the modified scheme in this study. The results show that both the climatological mean state, such as precipitation, temperature and specific humidity, and interannual variability in the model simulation are improved with the use of this modified scheme. Results from several additional experiments show that the improvements in the model performance in different regions mainly result from either the introduction of the relative humidity threshold for triggering of the deep convection or the suppressed shallow convection due to enhanced lateral convective entrainment/detrainment rates."
"8542741400;6603631763;6505921698;","Arguments against a physical long-term trend in global ISCCP cloud amounts",2007,"10.1029/2006GL028083","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347272145&doi=10.1029%2f2006GL028083&partnerID=40&md5=aac4e3ab407a74ede9e9548022104d9b","The International Satellite Cloud Climatology Project (ISCCP) multi-decadal record of cloudiness exhibits a well-known global decrease in cloud amounts. This downward trend has recently been used to suggest widespread increases in surface solar heating, decreases in planetary albedo, and deficiencies in global climate models. Here we show that trends observed in the ISCCP data are satellite viewing geometry artifacts and are not related to physical changes in the atmosphere. Our results suggest that the ISCCP data is not currently appropriate for long-term global studies. Copyright 2007 by the American Geophysical Union."
"7202079615;18935131000;7004174939;7404243086;","Two competing pathways of aerosol effects on cloud and precipitation formation",2007,"10.1029/2006GL028349","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547977823&doi=10.1029%2f2006GL028349&partnerID=40&md5=6cb2fefdeabcf7e098d81f05df5a3580","Aerosols may influence cloud formation through two pathways: One is the effect on cloud microphysics by forming smaller and more numerous cloud droplets reducing precipitation and consequently enhancing cloud lifetime. The second is referred to as the aerosol dynamic-hydrological effect in which the aerosol direct, semi-direct, and indirect effects can modulate atmospheric radiation, which perturbs atmospheric circulation, leading to redistributions of clouds and precipitation. Here this study examines climate sensitivities using a general circulation model coupled with an aerosol transport-radiation model. The model is run first with prescribed meteorology in order to isolate the cloud microphysical effect. It is run in a separate experiment with internally generated meteorology that includes dynamic-hydrological effect as the aerosols modify clouds and interact with the radiation. We find in some regions that the dynamic-hydrological effect in the free model runs counteracts the microphysical effects seen in the prescribed runs. Copyright 2007 by the American Geophysical Union."
"8600097900;6701606453;7004899626;7102591209;7202899330;","Performance assessment of a five-channel estimation-based ice cloud retrieval scheme for use over the global oceans",2007,"10.1029/2006JD007122","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34848898242&doi=10.1029%2f2006JD007122&partnerID=40&md5=e3ed6d7c00ff19374a0b29c21b524fbc","This work determines the performance of a five-channel ice cloud retrieval scheme in context of numerical synthetic experiments and real-world data and examines the implications of these results on the global retrieval of ice cloud microphysical properties over the global oceans. This estimation-based scheme, designed from information content principles, uses a rigorous, state-dependent error analysis to combine measurements from the visible, near-infrared, and infrared spectral regions. In the synthetic experiments, the five-channel scheme performed as well or better in terms of retrieval bias and random error than the traditional split-window and Nakajima and King bispectral retrieval techniques for all states of the atmosphere. Although the five-channel scheme performed favorably compared to the other methods, the inherently large uncertainties associated with ice cloud physics dictate typical retrieval uncertainties in both IWP and effective radius of 30-40%. These relatively large uncertainties suggest caution in the strict interpretation of small temporal or spatial trends found in existing cloud products. In MODIS and CRYSTAL-FACE applications, the five-channel scheme exploited the strengths of each of the bispectral approaches to smoothly transition from a split-window type approach for thin clouds to a Nakajima and King type approach for thick clouds. Uniform application of such a retrieval scheme across different satellite and field measurement campaigns would provide a set of consistent cloud products to the user community, theoretically allowing the direct comparison of cloud properties for the climate processes studies found throughout the literature. Copyright 2007 by the American Geophysical Union."
"6603196991;6603873829;6507128092;22133985200;57206330745;","Accuracy assessment of an integrated profiling technique for operationally deriving profiles of temperature, humidity, and cloud liquid water",2007,"10.1029/2006JD007379","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34848877242&doi=10.1029%2f2006JD007379&partnerID=40&md5=fc01ec01c6410b0249e59a438aa7ea5c","An integrated profiling technique (IPT) for the simultaneous retrieval of the atmospheric state parameters temperature, humidity, and liquid water content profiles is assessed. The method combines measurements of a modern, ground-based profiling station equipped with a microwave profiler, cloud radar, and ceilometer, with the closest operational radiosonde measurement and standard surface-based meteorological measurements. All are combined within an optimal estimation procedure. The accuracy assessment is carried out in a virtual environment of a regional climate model. The model thermodynamic state is converted into the measurement space via so-called forward modeling. The IPT is then applied to the simulated measurements to retrieve the desired atmospheric state parameters which can be evaluated with the original model state. It is found that IPT-derived temperature and humidity profiles can add significant information for the time period between two operational radiosonde ascents, both if the measurements take place at the radiosonde site or if they are spatially apart. The benefits of a profiling station that applies an IPT can be valuable both for the reprocessing of dedicated field campaign data to obtain the best representation of the atmospheric state and for nowcasting and data assimilation applications. Depending on the density of the given operational radiosonde network, a ground-based profiling station has the potential of either significantly improving the quality of such a network or even substituting a small number of radiosonde stations. A further benefit of a ground-based profiling station is the retrieval of cloud microphysical properties, where IPT liquid water path retrieval accuracies show values better than 10 g m-2, and liquid water content profiles can be derived with relative accuracies of ∼30%. Copyright 2007 by the American Geophysical Union."
"57188751935;6508026916;7006174511;6508003688;6701344406;","Sensitivity of the MM5 mesoscale model to physical parameterizations for regional climate studies: Annual cycle",2007,"10.1029/2005JD006649","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548603543&doi=10.1029%2f2005JD006649&partnerID=40&md5=d48b9bc8c441f3dccbf032a3dc109179","We present an analysis of the sensitivity to different physical parameterizations of a high-resolution simulation of the MM5 mesoscale model over the Iberian Peninsula. Several (16) 5-year runs of the MM5 model with varying parameterizations: of microphysics, cumulus, planetary boundary layer and longwave radiation have been carried out. The results have been extensively compared with observational precipitation and surface temperature data. The parameterization uncertainty has also been compared with that related to the boundary conditions and the varying observational data sets. The annual cycles of precipitation and surface temperature are well reproduced. The summer season presents the largest deviations, with a 5 K cold bias in the southeast and noticeable precipitation errors over mountain areas. The cold bias seems to be related to the surface, probably because of the excessive moisture availability of the five-layer soil scheme used. No parameterization combination was found to perform best in simulating both precipitation and surface temperature in every season and subregion. The Kain-Fritsch cumulus scheme was found to produce unrealistically high summer precipitation. The longwave radiation parameterizations tested were found to have little impact on our target variables. Other factors, such as the choice of boundary conditions, have an impact on the results as large as the selection of parameterizations. The range of variability in the MM5 physics ensemble is of the same order of magnitude as the observational uncertainty, except in summer, when it is larger and probably related to the inaccuracy of the model to reproduce the summer precipitation over the area. Copyright 2007 by the American Geophysical Union."
"6701455548;7102577095;","Sensitivity of climate forcing and response to dust optical properties in an idealized model",2007,"10.1029/2006JD007198","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547882438&doi=10.1029%2f2006JD007198&partnerID=40&md5=c6ee02b47f376fa9a540d48fedf6fb4c","An idealized global climate model is used to explore the response of the climate to a wide range of dust radiative properties and dust layer heights. The top-of-the-atmosphere (TOA) shortwave forcing becomes more negative as the broadband shortwave single scattering albedo increases and the broadband shortwave asymmetry parameter decreases, but the sensitivity is highly dependent on the location of the dust layer with respect to clouds. The longwave TOA forcing is most affected by the height of the dust layer. The net TOA forcing is most sensitive to the shortwave single scattering albedo and shortwave asymmetry parameter. The surface and atmospheric temperature responses are approximately linear with respect to the TOA forcing, as opposed to the surface or atmospheric forcings. Thus the TOA forcing can be used to estimate both the surface and atmospheric temperature responses to dust. The corresponding changes in latent and sensible heat fluxes are essential for the close relationship of the surface temperature response to the TOA forcing. Estimating the hydrological cycle response requires knowledge of the vertical distribution of dust with respect to clouds or other reflective particles. The sensitivity of the latent heat flux to variations in the shortwave single scattering albedo changes sign with dust height. The latent heat flux change becomes less negative as the shortwave single scattering albedo increases if the dust layer is below clouds. However, when the dust is above clouds, the latent heat response becomes more negative as the single scattering albedo increases. Copyright 2007 by the American Geophysical Union."
"7004479957;8882641700;24538177600;","Cloud droplet sedimentation, entrainment efficiency, and subtropical stratocumulus albedo",2007,"10.1029/2006GL027648","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548049274&doi=10.1029%2f2006GL027648&partnerID=40&md5=c92fc16a00d41a8e66f198899737902e","The effect of cloud droplet sedimentation on the entrainment rate and liquid water path of a nocturnal nondrizzling stratocumulus layer is examined using large-eddy simulations (LES) with bulk microphysics. In agreement with a prior study by Ackerman et al. (2004), sedimentation is found to decrease entrainment rate and thereby increase liquid water path. They suggested this is due to reduction of boundary-layer turbulence. Our simulations suggest otherwise. Instead, sedimentation reduces entrainment by removing liquid water from the entrainment zone. This inhibits two mechanisms that promote the sinking of entrained air into the cloud layer-entrainment-induced evaporative cooling and longwave radiative cooling. A sensitivity study shows that the radiative effect is less important than the reduced evaporation. A possible parameterization of the effect of sedimentation on entrainment rate in a mixed layer model is proposed and tested. Since the droplet sedimentation rate is inversely related to cloud droplet (and presumably aerosol) concentration and nearly nondrizzling marine stratocumulus are widespread, sedimentation impacts on stratocumulus entrainment efficiency should be considered in climate model simulations of the aerosol indirect effect. Copyright 2007 by the American Geophysical Union."
"7102587442;6602208685;","TRAMS: A new dynamic cloud model for Titan's methane clouds",2007,"10.1029/2006GL028652","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548042548&doi=10.1029%2f2006GL028652&partnerID=40&md5=643eadae6f7309ffd6a1e5bcbbca4ee0","Convective clouds on Titan may play an important role in climate dynamics, atmospheric chemistry, and the overall volatile cycle. To study the formation and evolution of these clouds, we have developed the Titan Regional Atmospheric Modeling System (TRAMS). TRAMS is a three-dimensional, time-dependent, coupled fully compressible dynamic and microphysical model capable of simulating methane and ethane clouds in Titan's atmosphere. In initial model tests over a two-dimensional domain, a warm bubble or random temperature perturbations trigger a parcel of air to rise. For an initial methane profile with a 60% surface humidity, convection occurs for positive temperature perturbations of 1 K or greater. Cloud tops are between 25 and 35 km, consistent with observations of the south polar clouds. For a drier methane environment in the lower atmosphere, characteristic of the Huygens landing site, convection does not occur, but a layer of stratiform clouds is able to form at altitudes around 10 km. Copyright 2007 by the American Geophysical Union."
"7102833569;18634198200;","End-of-storm oscillation in tropical air mass thunderstorms",2007,"10.1029/2005JD006997","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547908927&doi=10.1029%2f2005JD006997&partnerID=40&md5=eefb78d31df3724d8326a994f8192760","Characteristics of the end-of-storm oscillation (EOSO) in the atmospheric surface electric field observed beneath isolated air mass thunderstorms at a tropical station, Pune, are investigated. Typically, the value of the electric field at the ground during the EOSO periods has been observed to range between - 3 and +4 kV m-1. Durations of the EOSO at Pune are 24% of those for the large quasi-stationary thunderstorms occurring at Florida and 55% of the convective air mass thunderstorms at New Mexico. During the EOSO periods, frequency of lightning decreases very much but some flashes exhibit unique features of charge transportation associated with them. Observation of a new phenomenon, the inverted EOSO, is reported in a storm with inverted polarity of electrical dipole. Our observations are found to be consistent with the convective mechanism scenario of the EOSO in which the surface field meters are exposed to the upper positive charge of the cloud by the downdrafts. Copyright 2007 by the American Geophysical Union."
"7402328256;6701465132;35510362500;7005613103;18634906400;7003266200;7202888402;","Modeling and analysis of aerosol processes in an interactive chemistry general circulation model",2007,"10.1029/2005JD006077","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247489731&doi=10.1029%2f2005JD006077&partnerID=40&md5=d977c9dc036a230b0ccfdf5a104070ee","An ""online"" aerosol dynamics and chemistry module is included in the Laboratoire de Météorologie Dynamique general circulation model (LMDZ), so that the chemical species are advected at each dynamical time step and evolve through chemical and physical processes that have been parameterized consistently with the meteorology. These processes include anthropogenic and biogenic emissions, over 50 gas/aqueous phase chemical reactions, transport due to advection, vertical diffusion and convection, dry deposition and wet scavenging. We have introduced a size-resolved representation of aerosols which undergo various processes such as coagulation, nucleation and dry and wet scavenging. The model considers 16 prognostic tracers: water vapor, liquid water, dimethyl sulfide (DMS), hydrogen sulfide (H<inf>2</inf>S), dimethyl sulphoxide (DMSO), methanesulphonic acid (MSA), sulfur dioxide (SO<inf>2</inf>), nitrogen oxides (NO<inf>x</inf>), carbon monoxide (CO), nitric acid (HNO<inf>3</inf> ozone (O<inf>3</inf>), hydrogen peroxide (H<inf>2</inf>O<inf>2</inf>), sulfate mass and number for Aitken and accumulation modes. The scheme accounts for two-way interactions between tropospheric chemistry and aerosols. The oxidants and chemical species fields that represent the sulfate aerosol formation are evolved interactively with the model dynamics. A detailed description on the coupled climate-chemistry interactive module is presented with the evaluation of chemical species in winter and summer seasons. Aqueous phase reactions in cloud accounted for 71% of sulfate production rate, while only 45% of the sulfate burden in the troposphere is derived from in-cloud oxidation. Copyright 2007 by the American Geophysical Union."
"8927064100;57189498750;","An unexpected pattern of distinct weekly periodicities in climatological variables in Germany",2007,"10.1029/2006GL028559","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547767416&doi=10.1029%2f2006GL028559&partnerID=40&md5=7a1fa8688d34ea9888f160ac762c170a","Statistical analyses of data from 12 German meteorological stations meeting WMO standards in the period 1991-2005 are presented. These stations represent different local climate conditions in terms of both meteorology and pollution situation. For the average over data of all stations, we identified significant weekly periodicities in many variables such as temperature, daily temperature range, sunshine duration, cloud amount, precipitation, and precipitation frequency. Not only data of stations situated in congested urban areas, but also data of remote stations as e.g. on Mount Zugspitze 2960 m above sea level in the Alps showed significant in-phase weekly cycles. These weekly periodicities cannot be explained completely by local pollution effects or local heat emissions. We tend towards the hypothesis that the anthropogenic weekly emission cycle and the subsequent aerosol cycle interact with the atmospheric dynamics on a larger scale which leads to a forcing of a naturally existing 7-day period among the spectrum of atmospheric periods. Copyright 2007 by the American Geophysical Union."
"16025402200;7202583200;","Dynamics of the West African monsoon under mid-Holocene precessional forcing: Regional climate model simulations",2007,"10.1175/JCLI4013.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847417518&doi=10.1175%2fJCLI4013.1&partnerID=40&md5=be9f6ebc03e0fe4e9c066c46a3bb696f","The African Humid Period (AHP), about 14 800 yr ago [14.8-5.5 ka (ka ≡ 1000 yr ago)], was a time of increased humidity over Africa. Paleoclimate evidence suggests that the West African summer monsoon was stronger and more extensive 6 ka than today, and that the Saharan Desert was green. Here, a regional climate model that produces an excellent simulation of today's climate over northern Africa is used to study the dynamics of the monsoon 6 ka. Changes in insolation, atmospheric CO2, and vegetation are used to impose 6-ka conditions, and the role of each forcing is isolated. Vegetation is not interactive, and the large-scale circulation and SSTs are fixed at present-day values for the 6-ka simulations. The regional model produces precipitation increases across the Sahel and Sahara that are in good agreement with the paleodata. However, unobserved drying is simulated over the Guinean coast region where paleodata are sparse. Precipitation increases in the Sahel are related to a northward shift of the monsoon, the elimination of the African easterly jet, and an intensification and deepening of the low-level westerly jet on the west coast. The thermal low-Saharan high system of the present-day climate is replaced by a deep thermal low. When this system becomes fully developed in midsummer, cyclonic circulations transport moisture north into the Sahara, and rainfall increases there. Surface temperatures decrease despite the increased solar forcing 6 ka because of an increase in cloudiness. A moist static energy budget analysis shows that increased low-level moisture dominates the cooling to destabilize the vertical column and enhance convection. Even though solar forcing is the ultimate cause of the AHP, the model responds more strongly to the vegetation forcing, especially early in the summer season, emphasizing the importance of vegetation in maintaining the intensified monsoon system. © 2007 American Meteorological Society."
"7005386757;7201592750;7102633013;7202872916;7102150400;7006944398;","Accumulation of current-use pesticides in neotropical montane forests",2007,"10.1021/es0622709","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847239899&doi=10.1021%2fes0622709&partnerID=40&md5=9b410310cc94906319a9ce063706dbb5","In Central America, chemical-intensive tropical agriculture takes place in close proximity to highly valued and biologically diverse ecosystems, yet the potential for atmospheric transport of pesticides from plantations to national parks and other reserves is poorly characterized. The specific meteorological conditions of mountain ranges can lead to contaminant convergence at high altitudes, raising particular concern for montane forest ecosystems downwind from pesticide use areas. Here we show, based on a wide-ranging air and soil sampling campaign across Costa Rica, that soils in some neotropical montane forests indeed display much higher concentrations of currently used pesticides than soils elsewhere in the country. Specifically, elevated concentrations of the fungicide chlorothalonil, the herbicide dacthal, and the insecticide metabolite endosulfan sulfate on volcanoes Barva and Poas, lying directly downwind of the extensive banana plantations of the Caribbean lowland, indicate the occurrence of atmospheric transport and wet deposition of pesticides at high altitudes. Calculations with a contaminant fate model, designed for mountain regions and parametrized to the Costa Rican environment, show that chemicals with a log KAW between -3 and -5 have a greater potential for accumulation at high altitudes. This enrichment behavior is quantified by the Mountain Contamination Potential and is sensitive to contaminant degradability. The modeling work supports the hypothesis suggested by the field results that it is enhanced precipitation scavenging at high elevations (caused by lower temperatures and governed by KAW) that causes pesticides to accumulate in tropical montane areas. By providing for the first time evidence of significant transfer of currently used pesticides to Central American montane cloud forests, this study highlights the need to evaluate the risk that tropical agricultural practices place on the region's ecological reserves. © 2007 American Chemical Society."
"6602292934;35453054300;7007026915;","Observational and modeling studies of the impacts of agriculture-related land use change on planetary boundary layer processes in the central U.S.",2007,"10.1016/j.agrformet.2006.07.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846455350&doi=10.1016%2fj.agrformet.2006.07.013&partnerID=40&md5=e2dadb8be0dd7f427e01baf883b84476","The impact of agricultural land use change on atmospheric boundary layer processes, the associated feedbacks and their regional scale impacts, are examined with particular emphasis on the central United States. Specifically, the role of contrasting forested and agricultural land covers in the initiation and subsequent evolution of summertime cloud patterns in the U.S. Midwest; and the impact of agricultural practices, including irrigation, on the surface climate of the U.S. High Plains are discussed in detail. Satellite-based observational results of previous work summarized in this paper indicate that the timing and intensity of cloud development appears to be influenced by both synoptic flow regimes and agricultural land use type. For example, under conditions characterized by high pressure with surface winds generally less than 5 m s-1, peak cloud development occurred almost two hours earlier over cropland than over the forest or boundary locations in Michigan. Cloud masses were also considerably taller over cropland in the mid-afternoon than over forest and land cover transition zones. The modeling results discussed here for a model domain centered over Nebraska indicate significant differences in the surface energy fluxes between the irrigated (control) and non-irrigated (dry) simulations. Surface latent heat flux was higher by 36% and dewpoint temperature higher by 2.3 °C in the control simulation. Also, surface sensible heat flux of the control simulation was 15% less and the near-ground (2 m) temperature was 1.2 °C less compared to dry run, indicating irrigation-induced surface cooling effect. Recent investigations on crop-climate interactions in which crop and ecological models were coupled to regional climate models show that incorporating important perturbations such as prolonged droughts and the resulting changes in soil and plant nutrient conditions remains one of the biggest challenges in developing effective and realistic ecological-climate integrated modeling systems. © 2006 Elsevier B.V. All rights reserved."
"35453054300;6602292934;57209089997;36864686200;7403577184;57203474131;","A new paradigm for assessing the role of agriculture in the climate system and in climate change",2007,"10.1016/j.agrformet.2006.06.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846426359&doi=10.1016%2fj.agrformet.2006.06.012&partnerID=40&md5=f5d640e06230972c070e21af8fd5c7c2","This paper discusses the diverse climate forcings that impact agricultural systems, and contrasts the current paradigm of using global models downscaled to agricultural areas (a top-down approach) with a new paradigm that first assesses the vulnerability of agricultural activities to the spectrum of environmental risk including climate (a bottom-up approach). To illustrate the wide spectrum of climate forcings, regional climate forcings are presented including land-use/land-cover change and the influence of aerosols on radiative and biogeochemical fluxes and cloud/precipitation processes, as well as how these effects can be teleconnected globally. Examples are presented of the vulnerability perspective, along with a small survey of the perceived drought impacts in a local area, in which a wide range of impacts for the same precipitation deficits are found. This example illustrates why agricultural assessments of risk to climate change and variability and of other environmental risks should start with a bottom-up perspective. © 2006 Elsevier B.V. All rights reserved."
"55206018900;6701707324;57210860816;6701824742;","Biogeophysical effects of land use on climate: Model simulations of radiative forcing and large-scale temperature change",2007,"10.1016/j.agrformet.2006.08.021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846454364&doi=10.1016%2fj.agrformet.2006.08.021&partnerID=40&md5=75bd8a3d1a5aacdb29d9e28162b2e48e","Changes in land cover affect climate through the surface energy and moisture budgets. Here we assess the importance of these biogeophysical effects for present-day climate, and quantify the radiative forcing of historical climate change by land use change for comparison with radiative forcings due to anthropogenic changes in greenhouse gases and aerosols. We also discuss the implications of biogeophysical effects for the use of forestry as a tool for mitigating climate change through carbon sequestration. Our model results suggest that since most historical deforestation has taken place in temperate regions where the main climatic effect is an increase in surface albedo, the dominant biogeophysical effect of past land cover change has been a cooling. The northern mid-latitude agricultural regions are simulated to be approximately 1-2 K cooler in winter and spring in comparison with their previously forested state. This conflicts with the suggestion that land use change is responsible for the warming observed over the 20th century. The increase in albedo by 1750 is simulated to exert a negative radiative forcing of approximately -2 W m-2 locally over Europe, China and India, suggesting a potential anthropogenic influence on climate before fossil fuel burning began. The present-day global mean radiative forcing by anthropogenic surface albedo change relative to the natural state is simulated to be -0.2 W m-2, which is comparable with the estimated forcings relative to pre-industrial times by stratospheric and tropospheric ozone, N2O, the halocarbons, and the direct effect of anthropogenic aerosols. In cold regions, afforestation or reforestation would decrease the surface albedo and induce a positive radiative forcing (warming) which could partly or completely offset the negative forcing (cooling) due to carbon sequestration. This suggests that carbon sink plantations could be less effective than expected at reducing warming, and could even cause further warming. However, we note that reforestation (or avoided deforestation) in tropical regions could exert a double cooling effect through carbon sequestration and increased evaporation and cloud cover. © 2006."
"16027868800;6602911098;6701676517;","On the definition of the cloud water content fluctuations and its effects on the computation of a second-order liquid water correlation",2007,"10.1175/JAS3842.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847628315&doi=10.1175%2fJAS3842.1&partnerID=40&md5=16a43b9769ce67e8fea8f5401201403c","In subgrid-scale condensation schemes of cloud models, the majority of previous authors have relied on results presented in a paper by Bougeault. In the present paper, second-order liquid water correlations are restated that differ from the former paper but are coherent with the corrigendum of Mellor. These differences are explained here through two different underlying definitions of cloud water content fluctuations; they can be summarized by whether or not unsaturated air within a grid box contributes to the eddy flux of the cloud water content. Taking into account the issue mentioned above, the ""buoyancy flux"" is also derived. Although the full impact of these changes has not been evaluated here, it may become important for future global cloud-resolving climate models. © 2007 American Meteorological Society."
"7006303509;6603133549;16067960700;35494005000;7003821079;7005877775;7006783796;16069128500;7005171879;7003663305;7402934750;7410041005;","An intercomparison of microphysical retrieval algorithms for upper-tropospheric ice clouds",2007,"10.1175/BAMS-88-2-191","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947694704&doi=10.1175%2fBAMS-88-2-191&partnerID=40&md5=579f310271ba14dfa0c553823e48c2dc","The large horizontal extent, with its location in the cold upper troposphere, and ice composition make cirrus clouds important modulators of the Earth's radiation budget and climate. Cirrus cloud microphysical properties are difficult to measure and model because they are inhomogeneous in nature and their ice crystal size distribution and habit are not well characterized. Accurate retrievals of cloud properties are crucial for improving the representation of cloud-scale processes in large-scale models and for accurately predicting the Earth's future climate. A number of passive and active remote sensing retrieval algorithms exist for estimating the microphysical properties of upper-tropospheric clouds. We believe significant progress has been made in the evolution of these retrieval algorithms in the last decade; however, there is room for improvement. Members of the Atmospheric Radiation Measurement (ARM) program Cloud Properties Working Group are involved in an intercomparison of optical depth (τ) and ice water path in ice clouds retrieved using ground-based instruments. The goals of this intercomparison are to evaluate the accuracy of state-of-the-art algorithms, quantify the uncertainties, and make recommendations for their improvement. Currently, there are significant discrepancies among the algorithms for ice clouds with very small optical depths (τ < 0.3) and those with 1 < τ < 5. The good news is that for thin clouds (0.3 < τ < 1), the algorithms tend to converge. In this first stage of the intercomparison, we present results from a representative case study, compare the retrieved cloud properties with aircraft and satellite measurements, and perform a radiative closure experiment to begin gauging the accuracy of these retrieval algorithms. © 2007 American Meteorological Society."
"6701873414;7202784114;7004242319;15319750700;15318900900;15319239900;56982312900;56170404000;6602550636;7103373860;7402934750;57203233100;7005892627;6603385031;7202043942;57188949475;7006453382;7101984634;7005171879;7003475277;7006783796;57202521470;55390187500;7202589138;7801356574;7003663305;7004715270;7005729142;7006441949;","The mixed-phase arctic cloud experiment",2007,"10.1175/BAMS-88-2-205","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947698889&doi=10.1175%2fBAMS-88-2-205&partnerID=40&md5=2d73828b59dad2d8cb5f056cf7117e76","The Mixed-Phase Arctic Cloud Experiment (M-PACE) was conducted from 27 September through 22 October 2004 over the Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) on the North Slope of Alaska. The primary objectives were to collect a dataset suitable to study interactions between microphysics, dynamics, and radiative transfer in mixed-phase Arctic clouds, and to develop/ evaluate cloud property retrievals from surface-and satellite-based remote sensing instruments. Observations taken during the 1977/98 Surface Heat and Energy Budget of the Arctic (SHEBA) experiment revealed that Arctic clouds frequently consist of one (or more) liquid layers precipitating ice. M-PACE sought to investigate the physical processes of these clouds by utilizing two aircraft (an in situ aircraft to characterize the microphysical properties of the clouds and a remote sensing aircraft to constraint the upwelling radiation) over the ACRF site on the North Slope of Alaska. The measurements successfully documented the microphysical structure of Arctic mixed-phase clouds, with multiple in situ profiles collected in both single- and multilayer clouds over two ground-based remote sensing sites. Liquid was found in clouds with cloud-top temperatures as cold as -30°C, with the coldest cloud-top temperature warmer than -40°C sampled by the aircraft. Remote sensing instruments suggest that ice was present in low concentrations, mostly concentrated in precipitation shafts, although there are indications of light ice precipitation present below the optically thick single-layer clouds. The prevalence of liquid down to these low temperatures potentially could be explained by the relatively low measured ice nuclei concentrations. © 2007 American Meteorological Society."
"6603885684;","Holocene global warming and the origin of the neotropical Gran Sabana in the Venezuelan Guayana",2007,"10.1111/j.1365-2699.2006.01620.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846531307&doi=10.1111%2fj.1365-2699.2006.01620.x&partnerID=40&md5=5bd34cb650bc015d673fad6b03cf360f","Aim: The assumedly anomalous occurrence of savannas and forest-savanna mosaics in the Gran Sabana - a neotropical region under a climate more suitable for tropical rain forests - has been attributed to a variety of historical, climatic, and anthropogenic factors. This paper describes a previously undocumented shift in vegetation and climate that occurred during the early Holocene, and evaluates its significance for the understanding of the origin of the Gran Sabana vegetation. Location: A treeless savanna locality of the Gran Sabana (4°30′-6°45′ N and 60°34′-62°50′ W), in the Venezuelan Guayana of northern South America, at the headwaters of the Caroní river, one of the major tributaries of the Orinoco river. Methods: Pollen and charcoal analysis of a previously dated peat section spanning from about the Pleistocene/Holocene boundary until the present. Results: Mesothermic cloud forests dominated by Catostemma (Bombacaceae) occupied the site around the Pleistocene/Holocene boundary. During the early Holocene, a progressive but relatively rapid trend towards savanna vegetation occurred, and eventually the former cloud forests were replaced by a treeless savanna. Some time after the establishment of savannas, a marked increase in charcoal particles indicates the occurrence of the first local fires. Main conclusions: The occurrence of cloud forests at the Pleistocene/Holocene boundary contradicts the historical hypothesis according to which the Gran Sabana is a relict of the hypothetical widespread savannas that have been assumed to have dominated the region during the last glaciation. The first local fires recorded in the Holocene were on savanna vegetation, which is against the hypothesis of fire as the triggering factor for the establishment of these savannas. Climate change, in the form of global warming and a persistently drier climate, emerges as the most probable cause for the forest-savanna turnover. © 2007 The Author."
"6701548073;6701729202;7401491382;","Cloud cover over the South Pole from visual observations, satellite retrievals, and surface-based infrared radiation measurements",2007,"10.1175/JCLI4005.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847381966&doi=10.1175%2fJCLI4005.1&partnerID=40&md5=ff99552c94de55bcb6332d4f09acbe90","Estimates of cloud cover over the South Pole are presented from five different data sources: routine visual observations (1957-2004; Cvis), surface-based spectral infrared (IR) data (2001; CPAERI), surface-based broadband IR data (1994-2003; Cpyr), the Extended Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder (APP-x) dataset (1994-99; CAPP-x), and the International Satellite Cloud Climatology Project (ISCCP) dataset (1994-2003; CISCCP). The seasonal cycle of cloud cover is found to range from 45%-50% during the short summer to a relatively constant 55%-65% during the winter. Relationships between Cpyr and 2-m temperature, 10-m wind speed and direction, and longwave radiation are investigated. It is shown that clouds warm the surface in all seasons, 0.5-1 K during summer and 3-4 K during winter. The annual longwave cloud radiative forcing is 18 W m-2 for downwelling radiation and 10 W m-2 for net radiation. The cloud cover datasets are intercompared during the time periods in which they overlap. The nighttime bias of Cvis is worse than previously suspected, by approximately -20%; CISCCP shows some skill during the polar day, while CAPP-x shows some skill at night. The polar cloud masks for the satellite data reviewed here are not yet accurate enough to reliably derive surface or cloud properties over the East Antarctic Plateau. The best surface-based source of cloud cover in terms of the combination of accuracy and length of record is determined to be Cpyr. The use of the Cpyr dataset for further tests of satellite retrievals and for tests of polar models is recommended. © 2007 American Meteorological Society."
"8878281700;57201725986;7102965584;","Evolution, structure, cloud microphysical, and surface rainfall processes of monsoon convection during the South China Sea monsoon experiment",2007,"10.1175/JAS3852.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847634707&doi=10.1175%2fJAS3852.1&partnerID=40&md5=066203a9135ec8dbd5df55c9f77a406a","A two-dimensional cloud-resolving simulation is combined with dual-Doppler and polarimetric radar analysis to study the evolution, dynamic structure, cloud microphysics, and rainfall processes of monsoon convection observed during the South China Sea (SCS) summer monsoon onset. Overall, the model simulations show many similarities to the radar observations. The rainband associated with the convection remains at a very stable position throughout its life cycle in the northern SCS. The reflectivity pattern exhibits a straight upward structure with little tilt. The positions of the convective, transition, and stratiform regions produced by the model are consistent with the observations. The major difference from the observations is that the model tends to overestimate the magnitude of updraft. As a result, the maximum reflectivity generated by the model appears at an elevated altitude. The surface rainfall processes and associated thermodynamic, dynamic, and cloud microphysical processes are examined by the model in terms of surface rainfall, temperature and moisture perturbations, circulations, and cloud microphysical budget. At the preformation and dissipating stages, although local vapor change and vapor convergence terms are the major contributors in determining rain rate, they cancel each other out and cause little rain. The vapor convergence/divergence is closely related to the lower-tropospheric updraft/subsidence during the early/ late stages of the convection. During the formation and mature phases, vapor convergence term is in control of the rainfall processes. Meanwhile, water microphysical processes are dominant in these stages. The active vapor condensation process causes a large amount of raindrops through the collection of cloud water by raindrops. Ice microphysical processes including riming are negligible up to the mature phase but are dominant during the weakening stage. Cloud source/sink terms make some contributions to the rain rate at the formation and weakening stages, while the role of surface evaporation term is negligible throughout the life cycle of the convection. © 2007 American Meteorological Society."
"7101752236;7005899086;7005742394;","The influence of time-dependent melting on the dynamics and precipitation production in maritime and continental storm clouds",2007,"10.1175/JAS3832.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847685154&doi=10.1175%2fJAS3832.1&partnerID=40&md5=ea9a5206929c19ef4406a3f2c754fe4a","Simulations of one maritime and four continental observed cases of deep convection are performed with the Hebrew University Cloud Model that has spectral bin microphysics. The maritime case is from observations made on 18 September 1974 during the Global Atmospheric Research Program's Atlantic Tropical Experiment (GATE). The continental storm cases are those of summertime Texas clouds observed on 13 August 1999, and green-ocean, smoky, and pyro-clouds observed during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia-Smoke, Aerosols, Clouds, Rainfall, and Climate (LBA-SMOCC) campaign on 1-4 October 2002. Simulations have been performed for these cases with a detailed melting scheme. This scheme allows calculation of liquid water fraction within each mass bin for the melting of graupel, hail, snowflakes, and crystals, as well as alteration of the sedimentation velocity of ice particles in the course of their melting. The results obtained with the detailed melting scheme are compared with corresponding results from simulations involving instantaneous melting at the freezing (0°C) level. The detailed melting scheme allows penetration of ice from the freezing level down into the boundary layer by distances ranging from a few hundred meters for the numerous, smaller particles to ∼1.5 km for the largest particles, which are much scarcer. In these simulations, most of the mass of ice falling out melts over this short distance of a few hundred meters. The deepening and intensification of the layer of latent cooling enhances the convective destabilization of the troposphere. This effect is especially pronounced under continental conditions, causing significant changes in the accumulated rain amount. © 2007 American Meteorological Society."
"7004364155;7004325649;8891521600;35849753400;35779178900;7403531523;7006075455;10140984600;7406061582;23476370700;","Multi-instrument comparison of top-of-atmosphere reflected solar radiation",2007,"10.1175/JCLI4018.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847407084&doi=10.1175%2fJCLI4018.1&partnerID=40&md5=4bfbbeb7e5f30303205eb52fc714b714","Observations from the Clouds and the Earth's Radiant Energy System (CERES), Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging Spectroradiometer (MISR), and Sea-Viewing Wide-Field-of-View Sensor (Sea WiFS) between 2000 and 2005 are analyzed in order to determine if these data are meeting climate accuracy goals recently established by the climate community. The focus is primarily on top-of-atmosphere (TOA) reflected solar radiances and radiative fluxes. Direct comparisons of nadir radiances from CERES, MODIS, and MISR aboard the Terra satellite reveal that the measurements from these instruments exhibit a year-to-year relative stability of better than 1%, with no systematic change with time. By comparison, the climate requirement for the stability of visible radiometer measurements is 1% decade-1. When tropical ocean monthly anomalies in shortwave (SW) TOA radiative fluxes from CERES on Terra are compared with anomalies in Photosynthetically Active Radiation (PAR) from SeaWiFS - an instrument whose radiance stability is better than 0.07% during its first six years in orbit - the two are strongly anticorrelated. After scaling the Sea WiFS anomalies by a constant factor given by the slope of the regression line fit between CERES and Sea WiFS anomalies, the standard deviation in the difference between monthly anomalies from the two records is only 0.2 W m-2, and the difference in their trend lines is only 0.02 ± 0.3 W m-2 decade-1, approximately within the 0.3 W m-2 decade-1 stability requirement for climate accuracy. For both the Tropics and globe, CERES Terra SW TOA fluxes show no trend between March 2000 and June 2005. Significant differences are found between SW TOA flux trends from CERES Terra and CERES Aqua between August 2002 and March 2005. This discrepancy is due to uncertainties in the adjustment factors used to account for degradation of the CERES Aqua optics during hemispheric scan mode operations. Comparisons of SW TOA flux between CERES Terra and the International Satellite Cloud Climatology Project (ISCCP) radiative flux profile dataset (FD) RadFlux product show good agreement in monthly anomalies between January 2002 and December 2004, and poor agreement prior to this period. Commonly used statistical tools applied to the CERES Terra data reveal that in order to detect a statistically significant trend of magnitude 0.3 W m-2 decade-1 in global SW TOA flux, approximately 10 to 15 yr of data are needed. This assumes that CERES Terra instrument calibration remains highly stable, long-term climate variability remains constant, and the Terra spacecraft has enough fuel to last 15 yr. © 2007 American Meteorological Society."
"7402369164;7402871350;9236061200;6602981991;15840687000;15839436300;7003909199;6603104050;","Processes affecting oxygen isotope ratios of atmospheric and ecosystem sulfate in two contrasting forest catchments in central Europe",2007,"10.1021/es0610028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846786964&doi=10.1021%2fes0610028&partnerID=40&md5=d072a4dc31be08cb67ccad5f780346cc","Sulfate aerosols are harmful as respirable particles. They also play a role as cloud condensation nuclei and have radiative effects on global climate. A combination of δ18O-SO4 data with catchment sulfur mass balances was used to constrain processes affecting S cycling in the atmosphere and spruce forests of the Czech Republic. Extremely high S fluxes via spruce throughfall and runoff were measured at Jezeri (49 and 80 kg S ha -1 yr-1, respectively). The second catchment, Na Lizu, was 10 times less polluted. In both catchments, δ18O-SO 4 decreased in the following order: open-area precipitation &gt; throughfall &gt; runoff. The δ18O-SO4 values of throughfall exhibited a seasonal pattern at both sites, with maxima in summer and minima in winter. This seasonal pattern paralleled δ18O- H2O values, which were offset by -18‰. Sulfate in throughfall was predominantly formed by heterogeneous (aqueous) oxidation of SO2. Wet-deposited sulfate in an open area did not show systematic δ18O-SO4 trends, suggesting formation by homogeneous (gaseous) oxidation and/or transport from large distances. The percentage of incoming S that is organically cycled in soil was similar under the high and the low pollution. High-temperature 18O-rich sulfate was not detected, which contrasts with North American industrial sites. © 2007 American Chemical Society."
"36658658900;6603954179;","Climatic impacts of historical wetland drainage in Switzerland",2007,"10.1007/s10584-006-9120-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846607694&doi=10.1007%2fs10584-006-9120-8&partnerID=40&md5=6e97094e9b8dfb83c38975b5135f5382","The effects of historical land-use and land-cover changes on the climate of the Swiss Plateau in the different seasons were investigated. In the 19th century, a civil engineering project was initiated to reshape the lake and river system on the Swiss Plateau in order to ban the frequent flooding during extreme weather events. The landscape modifications consisted primarily of a conversion of wetlands with extended peat soils into a highly productive agricultural landscape. Historical maps (1800-1850) served as a basis for the reconstruction of the past land use. The ""Lokal-Modell"" of the Consortium for Small-Scale Modelling was used to conduct eight one-month long high-resolution simulations (1.5 × 1.5 km2) with present and past landscape conditions. The modified soil and surface properties led to distinctly altered energy and moisture exchanges at the surface and as a consequence affected the local and regional climate. The climatic changes show different characteristics and magnitudes in the cold (October - March) as compared to the warm season (April - September). The landscape modifications led to an average daytime cooling between -0.12°C (January) and -0.61°C (April) and a night-time warming of 0.19°C-0.34°C. The differences in the mean monthly temperatures show a warming of 0.1°C-0.2°C in the cold season and a cooling of similar magnitude in most of the study area in the warm season. The modification of the radiation budget and the surface energy balance distinctly affected the convective activity in the study area in the warm season, but had only a weak effect on convectivity in the cold season. The cloud coverage in the warm season is therefore distinctly reduced compared to the past. © 2006 Springer Science+Business Media B.V."
"55259325600;7102080550;","Impact of configurations of rapid intermittent assimilation of WSR-88D radar data for the 8 May 2003 Oklahoma City tornadic thunderstorm case",2007,"10.1175/MWR3313.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847418021&doi=10.1175%2fMWR3313.1&partnerID=40&md5=d2baa26aa483a2d1be401602b3469b58","Various configurations of the intermittent data assimilation procedure for Level-II Weather Surveillance Radar-1988 Doppler radar data are examined for the analysis and prediction of a tornadic thunderstorm that occurred on 8 May 2003 near Oklahoma City, Oklahoma. Several tornadoes were produced by this thunderstorm, causing extensive damages in the south Oklahoma City area. Within the rapidly cycled assimilation system, the Advanced Regional Prediction System three-dimensional variational data assimilation (ARPS 3DVAR) is employed to analyze conventional and radar radial velocity data, while the ARPS complex cloud analysis procedure is used to analyze cloud and hydrometeor fields and adjust in-cloud temperature and moisture fields based on reflectivity observations and the preliminary analysis of the atmosphere. Forecasts for up to 2.5 h are made from the assimilated initial conditions. Two one-way nested grids at 9- and 3-km grid spacings are employed although the assimilation configuration experiments are conducted for the 3-km grid only while keeping the 9-km grid configuration the same. Data from the Oklahoma City radar are used. Different combinations of the assimilation frequency, in-cloud temperature adjustment schemes, and the length and coverage of the assimilation window are tested, and the results are discussed with respect to the length and evolution stage of the thunderstorm life cycle. It is found that even though the general assimilation method remains the same, the assimilation settings can significantly impact the results of assimilation and the subsequent forecast. For this case, a 1-h-long assimilation window covering the entire initial stage of the storm together with a 10-min spinup period before storm initiation works best. Assimilation frequency and in-cloud temperature adjustment scheme should be set carefully to add suitable amounts of potential energy during assimilation. High assimilation frequency does not necessarily lead to a better result because of the significant adjustment during the initial forecast period. When a short assimilation window is used, covering the later part of the initial stage of storm and using a high assimilation frequency and a temperature adjustment scheme based on latent heat release can quickly build up the storm and produce a reasonable analysis and forecast. The results also show that when the data from a single Doppler radar are assimilated with properly chosen assimilation configurations, the model is able to predict the evolution of the 8 May 2003 Oklahoma City tornadic thunderstorm well for up to 2.5 h. The implications of the choices of assimilation settings for real-time applications are discussed. © 2007 American Meteorological Society."
"7005528529;","Wind erosion of tailings dams and mitigation of the dust nuisance",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249104135&partnerID=40&md5=3dc720b3618baaf3b074e1ab9ab072cd","Wind erosion can be a major cause of the loss and dispersion of tailings material from a tailings dam into its surrounding environment. Such dust dispersion can be a serious nuisance, as well as a health hazard to inhabitants in nearby settlements, and can also damage the health of animals, degrade crops, making them less marketable, and cause soil and water pollution. The problem of wind erosion can affect tailings dams in all types of climate, but becomes worse as climatic aridity increases. Because clouds of dust are often observed billowing across the top surfaces of tailings dams in dry windy weather, there is a common misconception that the dust arises from wind erosion of the top surface. As a result, much effort and money is vainly spent on treating the tops of tailings dams to prevent dust generation, whereas the slopes of the dams are the true major dust source. This paper briefly reviews what is known of erosion of tailings dams and then proceeds to describe the mechanics of wind erosion in general, and how it affects tailings dams in particular. Finally, recommendations are made for mitigating wind erosion of tailings dams and the resulting blowing dust. © The Southern African Institute of Mining and Metallurgy, 2007."
"57203053317;6602600408;56270311300;7003931528;","Different approaches for constraining global climate models of the anthropogenic indirect aerosol effect",2007,"10.1175/BAMS-88-2-243","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947662528&doi=10.1175%2fBAMS-88-2-243&partnerID=40&md5=fecfe582f735723656daab01cb635c43","Assessments of the influence of aerosol emissions from human activities on the radiation budget, in particular via the modification of cloud properties, have been a challenge. In light of the variability to both aerosol properties and environmental properties affected by aerosols, observational evidence alone cannot provide accurate and global answers, because detailed observations are locally limited and/or lack statistical significance. Thus, current understanding is predominantly derived from simulations with global models. General discrepancies to envelope (backward) modeling, however, suggest that many aerosol processes in global (forward) modeling are not properly considered. Using analytically derived parameterizations is recommended wherever possible. If an analytical method does not exist or is too demanding computationally, laboratory results augmented by field data are the second-best approach. For the constraint of so-derived parameterizations at the GCM scale, evaluating individual parameterizations using statistical relationships of satellite-retrieved quantities relevant to the process is recommended. The set of parameterizations may also be evaluated and improved using the data assimilation technique. To improve the quality of data references to modeling, there is a need to link available atmospheric data from all scales, and establish and support validation networks and experiments, and a commitment to fine-tune and improve satellite retrievals in an iterative process even beyond the anticipated period of the mission. Only then can more reliable estimates of the indirect aerosol effect be expected. © 2007 American Meteorological Society."
"6504750541;36006968000;","Dependence of simulation of boreal summer tropical intraseasonal oscillations on the simulation of seasonal mean",2007,"10.1175/JAS3844.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847648063&doi=10.1175%2fJAS3844.1&partnerID=40&md5=f100e6bc249598d1fb22e096d57b5811","The link between realism in simulation of the seasonal mean precipitation and summer tropical intraseasonal oscillations and their dependence on cumulus parameterization schemes is investigated using the Florida State University Global Spectral Model (FSUGSM). Forty-member model ensemble simulations of the northern summer season are generated for three different cumulus parameterization schemes [namely, Arakawa-Schubert (Naval Research Laboratory; NRL), Zhang and McFarlane (National Center for Atmospheric Research; NCAR), and Emanuel (Massachusetts Institute of Technology; MIT)]. The MIT scheme simulates the regional pattern of seasonal mean precipitation over the Indian monsoon region well but has large systematic bias in simulating the precipitation over the western Pacific and the Maritime Continent. Although the simulation of details of regional distribution of precipitation over the Indian monsoon region by the NRL and NCAR schemes is not accurate, they simulate the spatial pattern of precipitation over the tropical Indo-Pacific domain closer to observation. The NRL scheme seems to captures the observed northward and eastward propagation of intraseasonal precipitation anomalies realistically. However, the simulations of the NCAR and MIT schemes are dominated by a westward propagating component. The westward propagating mode seen in the model as well as observations is indicated to be an equatorial Rossby wave modified by the northern summer mean flow. An examination of the relationship between simulation of the model climatology and eastward propagating character of monsoon intraseasonal oscillations (ISOs) in a limited sample shows that the scheme that simulates better seasonal mean pattern of rainfall over the tropical Indo-Pacific domain also simulates better intraseasonal variance and more realistic eastward propagation of monsoon ISOs. Among the parameters known to be important for meridional propagation of the summer monsoon ISOs, the meridional gradient of mean humidity in the lower atmosphere seems to be crucial in determining the northward propagation in the equatorial Indian Ocean (between 10°S and 10°N). For better prediction of the seasonal mean Indian monsoon, therefore, the model climatology should have minimum bias not only over the Indian monsoon region but also over the entire Indo-Pacific basin. © 2007 American Meteorological Society."
"36907291300;7003329628;7407016988;7102781936;","Ten years of measurements of tropical upper-tropospheric water vapor by MOZAIC. Part I: Climatology, variability, transport, and relation to deep convection",2007,"10.1175/JCLI3997.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847390759&doi=10.1175%2fJCLI3997.1&partnerID=40&md5=fc5c9ee30f6dbfd16df1dd17c7ed0ab1","Ten years (1994-2004) of measurements of tropical upper-tropospheric water vapor (UTWV) by the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) are investigated over three regions - the tropical Atlantic, tropical Africa, and the Asian monsoon region - to determine the UTWV climatology and variability on multiple scales and to understand them in relation to moisture transport and deep convection. The seasonal migration of upper-tropospheric humidity (UTH) keeps pace with that of the ITCZ, indicating the convective influence on UTH distribution. Some significant regional differences are identified with the tropical Africa and the Asian monsoon regions being moister than the tropical Atlantic. UTH generally increases with height by 10%-20% relative humidity with respect to ice (RHi) from about 300 to 200 hPa, and the differences are larger in the deep Tropics than in the subtropics. The probability density functions of tropical UTH are often bimodal. The two modes stay rather constant; differences in the mean value are largely due to the variations in the proportion of the two modes as opposed to changes in the modes themselves. In the deep Tropics, the moisture level frequently reaches ice supersaturation, the most notable case being the near-equatorial Asian monsoon region during the wet season when ice supersaturation is observed 46% of the time. Interannual variations are observed in association with the 1997-98 ENSO event. A warming of about 1-2 K is observed for all three regions equatorward of roughly 15°. Specific humidity also increases somewhat for the tropical Atlantic and tropical Africa, but the increase in temperature outweighs the increase in specific humidity such that RH decreases by 5%-15% RHi. In addition to the ENSO-related variation, MOZAIC also sees increases in both RH and specific humidity over tropical Africa from 2000 onward. Moisture fluxes are computed from MOZAIC data and decomposed into contributions from the mean circulation and from eddies. The flux divergence, which represents the moisture source/sink from horizontal transport, is also estimated. Finally, the MOZAIC climatology and variability are revisited in relation to deep convection obtained from the International Satellite Cloud Climatology Project (ISCCP). © 2007 American Meteorological Society."
"7007184416;7003572826;7006534497;55897579400;8612942500;","Are there connections between the Earth's magnetic field and climate?",2007,"10.1016/j.epsl.2006.10.032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846019256&doi=10.1016%2fj.epsl.2006.10.032&partnerID=40&md5=3a2280854c55ddf8906efb274f46e864","Understanding climate change is an active topic of research. Much of the observed increase in global surface temperature over the past 150 years occurred prior to the 1940s and after the 1980s. The main causes invoked are solar variability, changes in atmospheric greenhouse gas content or sulfur due to natural or anthropogenic action, or internal variability of the coupled ocean-atmosphere system. Magnetism has seldom been invoked, and evidence for connections between climate and magnetic field variations have received little attention. We review evidence for correlations which could suggest such (causal or non-causal) connections at various time scales (recent secular variation ∼ 10-100 yr, historical and archeomagnetic change ∼ 100-5000 yr, and excursions and reversals ∼ 103-106 yr), and attempt to suggest mechanisms. Evidence for correlations, which invoke Milankovic forcing in the core, either directly or through changes in ice distribution and moments of inertia of the Earth, is still tenuous. Correlation between decadal changes in amplitude of geomagnetic variations of external origin, solar irradiance and global temperature is stronger. It suggests that solar irradiance could have been a major forcing function of climate until the mid-1980s, when ""anomalous"" warming becomes apparent. The most intriguing feature may be the recently proposed archeomagnetic jerks, i.e. fairly abrupt (∼ 100 yr long) geomagnetic field variations found at irregular intervals over the past few millennia, using the archeological record from Europe to the Middle East. These seem to correlate with significant climatic events in the eastern North Atlantic region. A proposed mechanism involves variations in the geometry of the geomagnetic field (f.i. tilt of the dipole to lower latitudes), resulting in enhanced cosmic-ray induced nucleation of clouds. No forcing factor, be it changes in CO2 concentration in the atmosphere or changes in cosmic ray flux modulated by solar activity and geomagnetism, or possibly other factors, can at present be neglected or shown to be the overwhelming single driver of climate change in past centuries. Intensive data acquisition is required to further probe indications that the Earth's and Sun's magnetic fields may have significant bearing on climate change at certain time scales. © 2006 Elsevier B.V. All rights reserved."
"55683214500;7402805784;55628550808;","Reflectance seasonality and its relation to the canopy leaf area index in an eastern Siberian larch forest: Multi-satellite data and radiative transfer analyses",2007,"10.1016/j.rse.2006.08.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845951162&doi=10.1016%2fj.rse.2006.08.011&partnerID=40&md5=9d352167245836d4c9777554d5fd25ee","Reliable monitoring of seasonality in the forest canopy leaf area index (LAI) in Siberian forests is required to advance the understanding of climate-forest interactions under global environmental change and to develop a forest phenology model within ecosystem modeling. Here, we compare multi-satellite (AVHRR, MODIS, and SPOT/VEGETATION) reflectance, normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and LAI with aircraft-based spectral reflectance data and field-measured forest data acquired from April to June in 2000 in a larch forest near Yakutsk, Russia. Field data in a 30 × 30-m study site and aircraft data observed around the field site were used. Larch is a dominant forest type in eastern Siberia, but comparison studies that consider multi-satellite data, aircraft-based reflectance, and field-based measurement data are rarely conducted. Three-dimensional canopy radiative transfer calculations, which are based on Antyufeev and Marshak's [Antyufeev, V.S., & Marshak, A.L. (1990). Monte Carlo method and transport equation in plant canopies, Remote Sensing of Environment, 31, 183-191] Monte Carlo photon transport method combined with North's [North, P.R. (1996). Three-dimensional forest light interaction model using a Monte Carlo method, IEEE Transactions on Geoscience and Remote Sensing, 34(4), 946-956] geometric-optical hybrid forest canopy scene, helped elucidate the relationship between canopy reflectance and forest structural parameters, including several forest floor conditions. Aircraft-based spectral measurements and the spectral response functions of all satellite sensors confirmed that biases in reflectance seasonality caused by differences in spectral response functions among sensors were small. However, some reflectance biases occur among the near infrared (NIR) reflectance data from satellite products; these biases were potentially caused by absolute calibration errors or cloud/cloud shadow contamination. In addition, reflectance seasonality in AVHRR-based NIR data was very small compared to other datasets, which was partially due to the spring-to-summer increase in the amount of atmospheric water vapor. Radiative transfer simulations suggest that bi-directional reflectance effects were small for the study site and observation period; however, changes in tree density and forest floor conditions affect the absolute value of NIR reflectance, even if the canopy leaf area condition does not change. Reliable monitoring of canopy LAI is achieved by minimizing these effects through the use of NIR reflectance difference, i.e., the difference in reflectance on the observation day from the reflectance on a snow-free/pre-foliation day. This may yield useful and robust parameters for multi-satellite monitoring of the larch canopy LAI with less error from intersensor biases and forest structure/floor differences. Further validation with field data and combined use of other index (e.g. normalized difference water index, NDWI) data will enable an extension of these findings to all Siberian deciduous forests. © 2006 Elsevier Inc. All rights reserved."
"7003717604;","A new satellite retrieval method for precipitable water vapor over land and ocean",2007,"10.1029/2006GL028019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548031377&doi=10.1029%2f2006GL028019&partnerID=40&md5=40e9e85b8567bce8a9557e0dc52132be","A fundamentally new method is presented for retrieving precipitable water vapor (PWV) using observations from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) satellite instrument. Unlike all existing passive satellite methods, the new technique is applicable both day and night, over ocean and land surfaces, and with little sensitivity to clouds. The method relies on a simple but accurate parameterization for AMSR-E polarization-difference signals at 18.7 and 23.8 GHz. Over land, validation is based on comparisons with the SuomiNet network of ground-based GPS receivers. With quality control measures applied, RMS retrieval errors over land are limited to approximately six mm with a linear correlation coefficient of 0.89. Differences with the operational AMSR-E oceanic PWV product are typically less than two mm. Products based on the new method should prove valuable in weather and climate research. Copyright 2007 by the American Geophysical Union."
"57189255136;7403247998;57201215091;","Moderate resolution imaging spectroradiometer bidirectional reflectance distribution function-based albedo parameterization for weather and climate models",2007,"10.1029/2005JD006736","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547937960&doi=10.1029%2f2005JD006736&partnerID=40&md5=c6a6aaf876bc7d3a8e08fdfeca8df0bb","The albedo of land surfaces is an important parameter for surface energy balance and is dependent on the solar zenith angle and the three-dimensional structure of the canopies. The Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF) algorithm is reformulated to derive a new two-parameter scheme for the computation of land surface albedo and its solar zenith angle (SZA) dependence for use in weather and climate models as well as in the remote sensing retrieval of surface solar fluxes. In this formulation the season- and pixel- dependent black-sky albedo at 60° SZA can be directly prescribed using the MODIS BRDF data while the two parameters are taken as a function of vegetation type only. Comparison of this formulation with those used in weather, climate, and data assimilation models (at NCAR, NCEP, and NASA) reveals the deficiencies in the treatment of SZA dependence and white-sky albedo in these models. Similarly, comparison of this formulation with those computed using the remotely sensed solar flux data from three groups (International Satellite Cloud Climatology Project (ISCCP)-FD, NASA's Clouds and the Earth's Radiant Energy System Tropical Rainfall Measuring Mission (CERES/ TRMM), and University of Maryland) shows that surface albedos from these data sets are at times unrealistic, and suggestions are made regarding how to better treat the surface albedo and its SZA dependence in the retrieval of surface and atmospheric solar fluxes. Copyright 2007 by the American Geophysical Union."
"55732233300;8654225000;56414179400;7404741481;55505923400;7501466543;","A concentric gravity wave structure in the mesospheric airglow images",2007,"10.1029/2005JD006558","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250328955&doi=10.1029%2f2005JD006558&partnerID=40&md5=00d2e83e551d96ebb61efe96f6d72bb3","A concentric gravity wave pattern was observed by an all-sky airglow imager located at Shigaraki, Japan (34.9°N, 136.1°E) on 3 October 2002. The wave pattern was identified over 2.5 hours (1330-1600 UT or 2230-0100 LT) both in the OI (557.7 nm) and OH (720-910 nm) band images. It had a wavelength of about 35 km and propagated concentrically northeastward with a horizontal phase velocity of about 80 m/s. The wave had a short period of about 7 min and a momentum flux of 2.2 m2/s2. We identified the source of the waves as a cumulonimbus in the satellite cloud images and in radar precipitation images near the center of the concentric pattem. We conclude that this rare wave pattern was caused by a weak wind system that extended from the stratosphere to the mesopause region in an autumn transition. Copyright 2007 by the American Geophysical Union."
"18134511700;7004715270;7005968859;6701762451;6603633815;57203776263;7202586843;7003905713;7003568823;7004371379;6701814134;7801653576;","Measurements of heterogeneous ice nuclei in the western United States in springtime and their relation to aerosol characteristics",2007,"10.1029/2006JD007500","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547580438&doi=10.1029%2f2006JD007500&partnerID=40&md5=e5daf5984f5db16a4f0707981cbc33e4","The second Ice Nuclei Spectroscopy (INSPECT-II) campaign was conducted at Storm Peak Laboratory in northwestern Colorado in April and May 2004. The physical and chemical characteristics of springtime atmospheric aerosols, including those which act as heterogeneous ice nuclei (IN), were investigated. The ice formation activity of submicron particles was measured with a continuous-flow diffusion chamber. The concentrations of heterogeneous ice nuclei ([IN]) active at -15 to -50°C and water supersaturations -25% < SSw < 0 typically ranged from 1 to 10 std 1-1. Aerosol mass spectrometry measurements indicated that the composition of IN had much higher contributions from mineral dust /fly ash and metallic particle types compared to ambient particles of similar sizes. While IN concentration and composition measurements are similar to observations from the same site during INSPECT-I in November 2001, there was considerably more variability in [IN] during INSPECT-II associated with periods of sporadically high [IN]. A relation of [IN] to concentrations of larger particles was noted; however, the predictive utility of such a relationship proved limited during non-dust-related increases in accumulation mode number concentrations. We conclude that the observed high variability and extremes in [IN] during spring are attributable primarily to variations in airborne dust concentrations and that the [IN] observed in spring 2004 represent lower bounds on the expected [IN] at SPL in the spring. On the basis of modeled dust vertical profiles, strong impacts of dust on [IN] might be expected at the higher altitudes of cold clouds. Copyright 2007 by the American Geophysical Union."
"6507056427;8842994000;9042684300;8733292100;23866122100;6701450462;7103294731;7004402705;7005804345;23090057700;8412334900;8088667300;8088667200;56572656100;","Nitric acid measurements at Eureka obtained in winter 2001-2002 using solar and lunar Fourier transform infrared absorption spectroscopy: Comparisons with observations at Thule and Kiruna and with results from three-dimensional models",2007,"10.1029/2006JD007096","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547876093&doi=10.1029%2f2006JD007096&partnerID=40&md5=9015070ee8bd08e26793af799b8c49a1","For the first time, vertical column measurements of nitric acid (HNO<inf>3</inf>) above Eureka (80.1°N, 86.4°W), Canada, have been made during polar night using lunar spectra recorded with a Fourier transform infrared (FTIR) spectrometer, from October 2001 to March 2002. This site is part of the primary Arctic station of the Network for the Detection of Stratospheric Change. These measurements were compared with FTIR measurements at two other Arctic sites: Thule, Greenland (76.5°N, 68.8°W), and Kiruna, Sweden (67.8°N, 20.4°E). Eureka lunar measurements are in good agreement with solar ones made with the same instrument. Eureka and Thule HNO<inf>3</inf> columns are consistent within measurement error. Differences between HNO<inf>3</inf> columns at Kiruna and those at Eureka and Thule can be explained on the basis of available sunlight hours and location of the polar vortex. The measurements were also compared with results from a chemistry-climate model, the Canadian Middle Atmosphere Model (CMAM), and from a three-dimensional chemical transport model, SLIMCAT. This is the first time that CMAM HNO<inf>3</inf> columns have been compared with observations in the Arctic. The comparison of CMAM HNO<inf>3</inf> columns with Eureka and Kiruna data shows good agreement. The warm 2001-2002 winter with almost no polar stratospheric clouds makes the comparison with this version of CMAM, which has a known warm bias, a good test for CMAM under these conditions. SLIMCAT captures the magnitude of HNO<inf>3</inf> columns at Eureka, and the day-to-day variability, but generally reports higher values than were measured at Thule and Kiruna. Copyright 2007 by the American Geophysical Union."
"7601318782;7004540083;6602844274;","Comparison of different global information sources used in surface radiative flux calculation: Radiative properties of the surface",2007,"10.1029/2005JD007008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547957086&doi=10.1029%2f2005JD007008&partnerID=40&md5=3b7a4bed6bfdd16d9f9dd85a4050bd81","Direct estimates of surface radiative fluxes that resolve regional and weather-scale variability over the whole globe with reasonable accuracy have only become possible with the advent of extensive global, mostly satellite, data sets within the past couple of decades. The accuracy of these fluxes, estimated to be about 10-15 W/m<inf>2</inf>, is largely limited by the accuracy of the input data sets. The leading uncertainties in the surface fluxes are no longer predominantly induced by clouds but are now as much associated with uncertainties in the surface and near-surface atmospheric properties. This study presents a fuller, more quantitative evaluation of the uncertainties for the surface albedo and emissivity and surface skin temperatures by comparing the main available global data sets from the Moderate-Resolution Imaging Spectroradiometer product, the NASA Global Energy and Water Cycle Experiment Surface Radiation Budget project, the European Centre for Medium-Range Weather Forecasts, the National Aeronautics and Space Administration, the National Centers for Environmental Prediction, the International Satellite Cloud Climatology Project (ISCCP), the Laboratoire de Météorologie Dynamique, NOAA/NASA Pathfinder Advanced Very High Resolution Radiometer project, and the NOAA Optimum Interpolation Sea Surface Temperature Analysis and the Tropical Rainfall Measuring Mission (TRMM) Microwave Image project. The data sets are, in practice, treated as an ensemble of realizations of the actual climate such that their differences represent an estimate of the uncertainty in their measurements because we do not possess global ""truth"" data sets for these quantities. The results are globally representative and may be taken as a generalization of our previous ISCCP-based uncertainty estimates for the input data sets. Surface properties have the primary role in determining the surface upward shortwave (SW) and longwave (LW) flux.From this study the following conclusions are obtained. Although land surface albedos in the near-infrared remain poorly constrained (highly uncertain), they do not cause too much error in total surface SW fluxes; the more subtle regional and seasonal variations associated with vegetation and snow are still in doubt. The uncertainty of the broadband black-sky SW albedo for land surface from this study is about 7%, which can easily induce 5-10 W/m<inf>2</inf> uncertainty in (upwelling) surface SW flux estimates. Even though available surface (broadband) LW emissivity data sets differ significantly (3-5% uncertainty), this disagreement is confined to wavelengths >20 amm so that there is little practical effect (1-3 W/m<inf>2</inf>) on the surface upwelling LW fluxes. The surface skin temperature is one of two leading factors that cause problems with surface LW fluxes. Even though the differences among the various data sets are generally only 2-4 K, this can easily cause 10-15 W/m<inf>2</inf> uncertainty in calculated surface (upwelling) LW fluxes. Significant improvements could be obtained for surface LW flux calculations by improving the retrievals of (in order of decreasing importance): (1) surface skin temperature, (2) surface air and near-surface-layer temperature, (3) column precipitable water amount, and (4) broadband emissivity. In addition, for surface SW fluxes, improvements could be obtained (excluding improved cloud treatment) by improving the retrievals of (1) aerosols (from our sensitivity studies but not discussed in this work) and (2) surface (black-sky) albedo, of which the NIR part of the spectrum has much larger uncertainty. Copyright 2007 by the American Geophysical Union."
"7004157687;55924208000;","Convective forcing fluctuations in a cloud-resolving model: Relevance to the stochastic parameterization problem",2007,"10.1175/JCLI3954.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846917940&doi=10.1175%2fJCLI3954.1&partnerID=40&md5=98e7db0c9be469cfaeae0b7b893cb031","Idealized cloud-resolving model (CRM) simulations spanning a large part of the tropical atmosphere are used to evaluate the extent to which deterministic convective parameterizations fail to capture the statistical fluctuations in deep-convective forcing, and to provide probability distribution functions that may be used in stochastic parameterization schemes for global weather and climate models. A coarse-graining methodology is employed to deduce an effective convective warming rate appropriate to the grid scale of a forecast model, and a convective parameterization scheme is used to bin these computed tendencies into different ranges of convective forcing strength. The dependence of the probability distribution functions for the coarse-grained temperature tendency on parameterized tendency is then examined. An aquaplanet simulation using a climate model, configured with similar horizontal resolution to that of the coarse-grained CRM fields, was used to compare temperature tendency variation (less the effect of advection and radiation) with that deduced as an effective forcing function from the CRM. The coarse-grained temperature tendency of the CRM is found to have a substantially broader probability distribution function than the equivalent quantity in the climate model. The CRM-based probability distribution functions of precipitation rate and convective warming are related to the statistical mechanics theory of Craig and Cohen and the ""stochastic physics"" scheme of Buizza et al. It is found that the standard deviation of the coarse-grained effective convective warming is an approximately linear function of its mean, thereby providing some support for the Buizza et al. scheme, used operationally by ECMWF."
"7103016965;24722339600;","Precipitation and cloud structure in midlatitude cyclones",2007,"10.1175/JCLI3998.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846935190&doi=10.1175%2fJCLI3998.1&partnerID=40&md5=c64258605e47ce569ab4b819a84048b8","Composite mean fields and probability distribution functions (PDFs) of rain rate, cloud type and cover, cloud-top temperature, surface wind velocity, and water vapor path (WVP) are constructed using satellite observations of midlatitude cyclones from four oceanic regions (i.e., the North Pacific, South Pacific, North Atlantic, and South Atlantic). Reanalysis surface pressure fields are used to ascertain the locations of the cyclone centers, onto which the satellite fields are interpolated to give a database of ∼1500 cyclones from a two-year period (2003-04). Cyclones are categorized by their strength, defined here using surface wind speed, and by their WVP, and it is found that these two measures can explain a considerable amount of the intercyclone variability of other key variables. Composite cyclones from each of the four ocean basins exhibit similar spatial structure for a given strength and WVP. A set of nine composites is constructed from the database using three strength and three WVP ranges and is used to demonstrate that the mean column relative humidity of these systems varies only slightly (0.58-0.62) for a doubling in WVP (or equivalently a 7-K rise in sea surface temperature) and a 50% increase in cyclone strength. However, cyclone-mean rain rate increases markedly with both cyclone strength and WVP, behavior that is explained with a simple warm conveyor belt model. Systemwide high cloud fraction (tops above 440 hPa) increases from 0.23 to 0.31 as cyclone strength increases by 50%, but does not vary systematically with WVP. It is suggested that the composite fields constitute useful diagnostics for evaluating the behavior of large-scale numerical models, and may provide insight into how precipitation and clouds in midlatitude cyclones respond under a changed climate. © 2007 American Meteorological Society."
"55618857100;57208346904;","Regional climate model simulations of U.S. precipitation and surface air temperature during 1982-2002: Interannual variation",2007,"10.1175/JCLI4129.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846915334&doi=10.1175%2fJCLI4129.1&partnerID=40&md5=d9d311a7d3ecba48c57e70f190fbb335","The fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5)-based regional climate model (CMM5) capability in simulating the interannual variations of U.S. precipitation and surface air temperature during 1982-2002 is evaluated with a continuous baseline integration driven by the NCEP-Department of Energy (DOE) Second Atmospheric Model Intercomparison Project Reanalysis (R-2). It is demonstrated that the CMM5 has a pronounced downscaling skill for precipitation and temperature inter-annual variations. The EOF and correlation analyses illustrate that, for both quantities, the CMM5 captures the spatial pattern, temporal evolution, and circulation teleconnections much better than the R-2. In particular, the CMM5 more realistically simulates the precipitation pattern centered in the Northwest, where the representation of the orographic enhancement by the forced uplifting during winter (rainy season) is greatly improved over the R-2. The downscaling skill, however, is sensitive to the cumulus parameterization. This sensitivity is studied by comparing the baseline with a branch summer integration replacing the Grell with the Kain-Fritsch cumulus scheme in the CMM5. The dominant EOF mode of the U.S. summer precipitation interannual variation, identified with the out-of-phase relationship between the Midwest and Southeast in observations, is reproduced more accurately by the Grell than the Kain-Fritsch scheme, which largely underestimates the variation in the Midwest. This pattern is associated with east-west movement of the Great Plains low-level jet (LLJ): a more western position corresponds to a stronger southerly flow bringing more moisture and heavier rainfall in the Midwest and less in the Southeast. The second EOF pattern, which describes the consistent variation over the southern part of the Midwest and the South in observations, is captured better by the Kain-Fritsch scheme than the Grell, whose pattern systematically shifts southward. © 2007 American Meteorological Society."
"6507340013;6701417681;15759218800;","A high-resolution satellite-derived sea surface temperature climatology for the western North Atlantic Ocean",2007,"10.1016/j.csr.2006.10.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846057319&doi=10.1016%2fj.csr.2006.10.002&partnerID=40&md5=80c102e1c05050960846d585ac4386ec","Long-term and high-resolution (∼1.2 km) satellite-derived sea surface temperature (SST) fields of a monthly mean time series for the 1985-1999 period, and a daily climatology have been calculated for the North West Atlantic Ocean. The SST fields extend from 78°W to 41°W in longitude, and 30°N to 56°N in latitude, encompassing the region off Cape Hatteras, North Carolina, to the southern Labrador Sea. The monthly mean time series, consists of 180 cloud-masked monthly mean SST fields, derived from a full-resolution NOAA/NASA Pathfinder SST data set for the 1985-1999 period. The satellite-derived monthly mean SST fields, as compared with in situ monthly mean near-surface ocean temperatures from buoys located in the western North Atlantic, yield an overall RMS difference of 1.15 °C. The daily climatology, which consists of 365 fields, was derived by applying a least-squares harmonic regression technique on the monthly mean SST time series for the full study period. The monthly mean and daily climatological SST fields will be useful for studying inter-annual variability related to climate variability of SST over the study domain. © 2006 Elsevier Ltd. All rights reserved."
"7004415966;36342537900;6603858313;","Estimation of the impact of sampling errors in the VOS observations on air-sea fluxes. Part I: Uncertainties in climate means",2007,"10.1175/JCLI4010.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846898007&doi=10.1175%2fJCLI4010.1&partnerID=40&md5=4a75ec0a40983a3725e762d0e36b97bd","Sampling uncertainties in the voluntary observing ship (VOS)-based global ocean-atmosphere flux fields were estimated using the NCEP-NCAR reanalysis and ECMWF 40-yr Re-Analysis (ERA-40) as well as seasonal forecasts without data assimilation. Air-sea fluxes were computed from 6-hourly reanalyzed individual variables using state-of-the-art bulk formulas. Individual variables and computed fluxes were subsampled to simulate VOS-like sampling density. Random simulation of the number of VOS observations and simulation of the number of observations with contemporaneous sampling allowed for estimation of random and total sampling uncertainties respectively. Although reanalyses are dependent on VOS, constituting an important part of data assimilation input, it is assumed that the reanalysis fields adequately reproduce synoptic variability at the sea surface. Sampling errors were quantified by comparison of the regularly sampled (i.e., 6 hourly) and subsampled monthly fields of surface variables and fluxes. In poorly sampled regions random sampling errors amount to 2.5°-3°C for air temperature, 3 m s-1 for the wind speed, 2-2.5 g kg-1 for specific humidity, and 15%-20% of the total cloud cover. The highest random sampling errors in surface fluxes were found for the sensible and latent heat flux and range from 30 to 80 W m-2. Total sampling errors in poorly sampled areas may be higher than random ones by 60%. In poorly sampled subpolar latitudes of the Northern Hemisphere and throughout much of the Southern Ocean the total sampling uncertainty in the net heat flux can amount to 80-100 W m-2. The highest values of the uncertainties associated with the interpolation/extrapolation into unsampled grid boxes are found in subpolar latitudes of both hemispheres for the turbulent fluxes, where they can be comparable with the sampling errors. Simple dependencies of the sampling errors on the number of samples and the magnitude of synoptic variability were derived. Sampling errors estimated from different reanalyses and from seasonal forecasts yield qualitatively comparable spatial patterns, in which the actual values of uncertainties are controlled by the magnitudes of synoptic variability. Finally, estimates of sampling uncertainties are compared with the other errors in air-sea fluxes and the reliability of the estimates obtained is discussed. © 2007 American Meteorological Society."
"57203053317;57208121852;24398842400;16444232500;55916925700;7003979342;55879827400;","Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM",2007,"10.5194/acp-7-3425-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547341225&doi=10.5194%2facp-7-3425-2007&partnerID=40&md5=c240596013273b0907ea4dc8232c7406","The double-moment cloud microphysics scheme from ECHAM4 that predicts both the mass mixing ratios and number concentrations of cloud droplets and ice crystals has been coupled to the size-resolved aerosol scheme ECHAM5-HAM. ECHAM5-HAM predicts the aerosol mass, number concentrations and mixing state. The simulated liquid, ice and total water content and the cloud droplet and ice crystal number concentrations as a function of temperature in stratiform mixed-phase clouds between 0 and -35° C agree much better with aircraft observations in the ECHAM5 simulations. ECHAM5 performs better because more realistic aerosol concentrations are available for cloud droplet nucleation and because the Bergeron-Findeisen process is parameterized as being more efficient. The total anthropogenic aerosol effect includes the direct, semi-direct and indirect effects and is defined as the difference in the top-of-the-atmosphere net radiation between present-day and pre-industrial times. It amounts to -1.9 W m-2 in ECHAM5, when a relative humidity dependent cloud cover scheme and aerosol emissions representative for the years 1750 and 2000 from the AeroCom emission inventory are used. The contribution of the cloud albedo effect amounts to -0.7 W m-2. The total anthropogenic aerosol effect is larger when either a statistical cloud cover scheme or a different aerosol emission inventory are employed because the cloud lifetime effect increases."
"25031430500;6701511321;","The global impact of supersaturation in a coupled chemistry-climate model",2007,"10.5194/acp-7-1629-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947664887&doi=10.5194%2facp-7-1629-2007&partnerID=40&md5=cc73c403a882259e8c7b03e69ac3ea4b","Ice supersaturation is important for understanding condensation in the upper troposphere. Many general circulation models however do not permit supersaturation. In this study, a coupled chemistry climate model, the Whole Atmosphere Community Climate Model (WACCM), is modified to include supersaturation for the ice phase. Rather than a study of a detailed parameterization of supersaturation, the study is intended as a sensitivity experiment, to understand the potential impact of supersaturation, and of expected changes to stratospheric water vapor, on climate and chemistry. High clouds decrease and water vapor in the stratosphere increases at a similar rate to the prescribed supersaturation (20% supersaturation increases water vapor by nearly 20%). The stratospheric Brewer-Dobson circulation slows at high southern latitudes, consistent with slight changes in temperature likely induced by changes to cloud radiative forcing. The cloud changes also cause an increase in the seasonal cycle of near tropopause temperatures, increasing them in boreal summer over boreal winter. There are also impacts on chemistry, with small increases in ozone in the tropical lower stratosphere driven by enhanced production. The radiative impact of changing water vapor is dominated by the reduction in cloud forcing associated with fewer clouds (∼+0.6 Wm -2) with a small component likely from the radiative effect (greenhouse trapping) of the extra water vapor (∼+0.2 Wm-2), consistent with previous work. Representing supersaturation is thus important, and changes to supersaturation resulting from changes in aerosol loading for example, might have a modest impact on global radiative forcing, mostly through changes to clouds. There is no evidence of a strong impact of water vapor on tropical tropopause temperatures."
"16233122400;35512883100;","Infrared properties of cirrus clouds in climate models",2007,"10.1002/qj.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247245679&doi=10.1002%2fqj.1&partnerID=40&md5=a190e48bd2fb2703c2599c28094eba8d","The representation in global climate models of the infrared radiative properties of cirrus clouds is assessed by comparing their radiative forcing calculated using airborne in-situ-measured size distributions and retrievals from combined lidar and Doppler-radar data. The latter are fitted to a bimodal function, allowing the inclusion of the size distribution's shape, normally omitted in the characterization of cirrus. The impact of the particle size distribution's shape on the atmosphere's radiation fields is evaluated using a two-stream radiative code. The comparisons show that the effect of the shape of the size distributions used to calculate the radiative forcing of a cirrus layer composed of hexagonal cylinders is not negligible, evidencing the ambiguity linked to the commonly used two-parameter (effective radius and ice water content) characterization of cirrus, and showing that the inclusion of a simple measure of the relative concentration of small particles improves its radiative parameterization. Copyright © 2007 Royal Meteorological Society."
"7003904922;7201692406;55710671300;","The role of the global electric circuit in solar and internal forcing of clouds and climate",2007,"10.1016/j.asr.2007.01.071","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548708518&doi=10.1016%2fj.asr.2007.01.071&partnerID=40&md5=a8b7844575ec5cb59473c7c5ab66bef4","Reports of a variety of short-term meteorological responses to changes in the global electric circuit associated with a set of disparate inputs are analyzed. The meteorological responses consist of changes in cloud cover, atmospheric temperature, pressure, or dynamics. All of these are found to be responding to changes in a key linking agent, that of the downward current density, J z , that flows from the ionosphere through the troposphere to the surface (ocean and land). As it flows through layer clouds, J z generates space charge in conductivity gradients at the upper and lower boundaries, and this electrical charge is capable of affecting the microphysical interactions between droplets and both ice-forming nuclei and condensation nuclei. Four short-term inputs to the global circuit are due to solar activity and consist of (1) Forbush decreases of the galactic cosmic ray flux; (2) solar energetic particle events; (3) relativistic electron precipitation changes; and (4) polar cap ionospheric convection potential changes. One input that is internal to the global circuit consists of (5) global ionospheric potential changes due to changes in the current output of the highly electrified clouds (mainly deep convective clouds at low latitudes) that act as generators for the circuit. The observed short-term meteorological responses to these five inputs are of small amplitude but high statistical significance for repeated J z changes of order 5% for low latitudes increasing to 25-30% at high latitudes. On the timescales of multidecadal solar minima, such as the Maunder minimum, changes in tropospheric dynamics and climate related to J z are also larger at high latitudes, and correlate with the lower energy component (∼1 GeV) of the cosmic ray flux increasing by as much as a factor of two relative to present values. Also, there are comparable cosmic ray flux changes and climate responses on millennial timescales. The persistence of the longer-term J z changes for many decades to many centuries would produce an integrated effect on climate that could dominate over short-term weather and climate variations, and explain the observed correlations. Thus, we propose that mechanisms responding to J z are a candidate for explanations of sun-weather-climate correlations on multidecadal to millenial timescales, as well as on the day-to-day timescales analyzed here. © 2007 COSPAR."
"7102663296;6603580448;7006107059;16426158500;","Long range transport and fate of a stratospheric volcanic cloud from Soufrière Hills volcano, Montserrat",2007,"10.5194/acp-7-5093-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35148867078&doi=10.5194%2facp-7-5093-2007&partnerID=40&md5=8be1cda257517c0ce5f4d6b717aab8f0","Volcanic eruptions emit gases, ash particles and hydrometeors into the atmosphere, occasionally reaching heights of 20 km or more, to reside in the stratospheric over-world where they affect the radiative balance of the atmosphere and the Earth's climate. Here we use satellite measurements and a Lagrangian particle dispersion model to determine the mass loadings, vertical penetration, horizontal extent, dispersion and transport of volcanic gases and particles in the stratosphere from the volcanic cloud emitted during the 20 May 2006 eruption of Soufrière Hills volcano, Montserrat, West Indies. Infrared, ultraviolet and microwave radiation measurements from two polar orbiters are used to quantify the gases and particles, and track the movement of the cloud for 23 days, over a distance of ∼18000 km. Approximately, 0.1±0.01 Tg(S) was injected into the stratosphere in the form of SO 2: the largest single sulphur input to the stratosphere in 2006. Microwave Limb Sounder measurements indicate an enhanced mass of HCl of ∼0.003-0.01 Tg. Geosynchronous satellite data reveal the rapid nature of the stratospheric injection and indicate that the eruption cloud contained ∼2Tg of ice, with very little ash reaching the stratosphere. These new satellite measurements of volcanic gases and particles can be used to test the sensitivity of climate to volcanic forcing and assess the impact of stratospheric sulphates on climate cooling."
"7404871794;7404369915;","The EU-CLOUDMAP project: Cirrus and contrail cloud-top maps from satellites for weather forecasting climate change analysis",2007,"10.1080/01431160600641913","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249341679&doi=10.1080%2f01431160600641913&partnerID=40&md5=b82810f96fb6d8d807cebe70194f9a60","The EU-CLOUDMAP project took place between 1997-2000 as a collaboration between five university and government research groups in the UK, Germany, the Netherlands and Switzerland. The original scientific motivation of the EU-CLOUDMAP Project was to improve the measurement and characterization of cirrus and contrail cloud properties. IPCC (Penner et al. 1999) demonstrated that contrail clouds could play a small but significant role in changing the radiative balance of the atmosphere based on work from one of the CLOUDMAP partners (DLR) using AVHRR data over Europe. However, the scope was broadened to include properties of clouds at all altitudes as (Cess et al. 1993) had shown that depending on how cloud processes are parameterised can lead to an order of magnitude difference in predictions of surface temperature due to changes in CO2 radiative forcing. This error is by far the largest uncertainty in making accurate forecasts of global warming. The primary technological motivation of the Project was to develop new techniques for deriving cloud-top properties (cloud-top height, amount, microphysics and winds) from a new series of meteorological sensors based on the use of either cloud-top stereo (ATSR-2 and MISR) or Oxygen A-band (MOS) and their application to the generation of new cloud climatology products. A secondary goal was to develop an automated technique, based on fuzzy logic, to detect contrails in non-thermal imagery where contrails can only be detected through their unique spatial characteristics. Validation of cloud products was perceived as a crucial central issue to any adoption of these products by the Numerical Weather Prediction (NWP) and climate forecasting communities. This presents unique challenges as validation must be conducted simultaneously with satellite data acquisition. Ground-based remote sensing techniques exploiting continuously operating radars and lidars were used and a new technique based on visible stereo digital cameras for retrieving cloud-base properties was pioneered. A technology spin-off from the CLOUDMAP work at UCL was the development of an uncooled thermal IR fish-eye lens camera for continuously monitoring cloud cover from the ground to replace existing manual observations of cloud cover (Chapman et al. 2007). Eight papers in this issue show some of the highlights of the project including fundamental aspects of the algorithms for retrieval of cloud-top height using stereo photogrammetry from ATSR-2 (Muller et al. 2007, Denis et al. 2007) and MOMS (Drescher 2007) and Oxygen A-band from MOS (Preusker et al. 2007). Seiz et al. (2007) describe the development of a novel technique for the automated retrieval of cloud-base height from stereo visible digital cameras. Naud et al. (2007) describe the validation of cloud-top heights from ATSR-2 and MOS using ground-based radar and lidar. Hetzheim (2007) shows how fuzzy logic systems can be employed for contrail detection when thermal imagery is not available using MOS and ATSR-2 to demonstrate his techniques. Finally, Meyer et al. (2007) show results from applying the thermal IR contrail detection technique to AVHRR over Asia."
"9246517900;7006689276;","Dependence of frequency of convective cloud occurrence on the orbital drift of satellites",2007,"10.1080/01431160701294646","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547683901&doi=10.1080%2f01431160701294646&partnerID=40&md5=c2a6185bc8f411f03a953c9e06381495","Deriving accurate time-series of cloud cover from satellite sensor data still remains a challenging task. The instruments onboard polar orbiting NOAA satellites offer the opportunity to prepare cloud climatology on a global scale; however, the orbital drifts of these satellites can introduce uncertainty when deriving such cloud climatology. The aim of this letter is to point out the importance and to estimate the impact of orbital drift on long-term time-series of the observation of convective cloud frequency of occurrence. The 20 years of daytime AVHRR data from over the Indian subcontinent for the summer monsoon season is used in this study. All four AVHRRs onboard NOAA-7, -9, -11, and -14 satellites show positive correlation between increased cloud frequency and the delay in equator crossing-times during their lifetime. This increase is significant over land, but over the ocean, there is no discernible effect. This effect should be considered to avoid spurious trends in cloud cover. Further in-depth investigations are needed to make possible corrections."
"8718425100;13402933200;7102988363;15127430500;57203053317;","Global model simulations of the impact of ocean-going ships on aerosols, clouds, and the radiation budget",2007,"10.5194/acp-7-5061-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34948813533&doi=10.5194%2facp-7-5061-2007&partnerID=40&md5=fc7c2892f88a66461db2e2b57e9af3af","International shipping contributes significantly to the fuel consumption of all transport related activities. Specific emissions of pollutants such as sulfur dioxide (SO2) per kg of fuel emitted are higher than for road transport or aviation. Besides gaseous pollutants, ships also emit various types of particulate matter. The aerosol impacts the Earth's radiation budget directly by scattering and absorbing the solar and thermal radiation and indirectly by changing cloud properties. Here we use ECHAM5/MESSy1-MADE, a global climate model with detailed aerosol and cloud microphysics to study the climate impacts of international shipping. The simulations show that emissions from ships significantly increase the cloud droplet number concentration of low marine water clouds by up to 5% to 30% depending on the ship emission inventory and the geographic region. Whereas the cloud liquid water content remains nearly unchanged in these simulations, effective radii of cloud droplets decrease, leading to cloud optical thickness increase of up to 5-10%. The sensitivity of the results is estimated by using three different emission inventories for present-day conditions. The sensitivity analysis reveals that shipping contributes to 2.3% to 3.6% of the total sulfate burden and 0.4% to 1.4% to the total black carbon burden in the year 2000 on the global mean. In addition to changes in aerosol chemical composition, shipping increases the aerosol number concentration, e.g. up to 25% in the size range of the accumulation mode (typically &gt;0.1 μm) over the Atlantic. The total aerosol optical thickness over the Indian Ocean, the Gulf of Mexico and the Northeastern Pacific increases by up to 8-10% depending on the emission inventory. Changes in aerosol optical thickness caused by shipping induced modification of aerosol particle number concentration and chemical composition lead to a change in the shortwave radiation budget at the top of the atmosphere (ToA) under clear-sky condition of about -0.014 W/m2 to -0.038 W/m2 for a global annual average. The corresponding all-sky direct aerosol forcing ranges between -0.011 W/m2 and -0.013 W/m2. The indirect aerosol effect of ships on climate is found to be far larger than previously estimated. An indirect radiative effect of -0.19 W/m2 to -0.60 W/m2 (a change in the atmospheric shortwave radiative flux at ToA) is calculated here, contributing 17% to 39% of the total indirect effect of anthropogenic aerosols. This contribution is high because ship emissions are released in regions with frequent low marine clouds in an otherwise clean environment. In addition, the potential impact of particulate matter on the radiation budget is larger over the dark ocean surface than over polluted regions over land."
"6602940714;","Cosmoclimatology: A new theory emerges",2007,"10.1111/j.1468-4004.2007.48118.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846600802&doi=10.1111%2fj.1468-4004.2007.48118.x&partnerID=40&md5=ae53c1b71a975c08ab7e11efc0410792","Changes in the intensity of galactic cosmic rays alter the Earth's cloudiness. A recent experiment has shown how electrons liberated by cosmic rays assist in making aerosols, the building blocks of cloud condensation nuclei, while anomalous climatic trends in Antarctica confirm the role of clouds in helping to drive climate change. Variations in the cosmic-ray influx due to solar magnetic activity account well for climatic fluctuations on decadal, centennial and millennial timescales. Over longer intervals, the changing galactic environment of the solar system has had dramatic consequences, including Snowball Earth episodes. A new contribution to the faint young Sun paradox is also on offer."
"7004299063;16029719200;6701413579;7006329853;16027966800;7102783229;","Climatic consequences of regional nuclear conflicts",2007,"10.5194/acp-7-2003-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247403485&doi=10.5194%2facp-7-2003-2007&partnerID=40&md5=ffe15e0156d779e994a765355e71ffbd","We use a modern climate model and new estimates of smoke generated by fires in contemporary cities to calculate the response of the climate system to a regional nuclear war between emerging third world nuclear powers using 100 Hiroshima-size bombs (less than 0.03% of the explosive yield of the current global nuclear arsenal) on cities in the subtropics. We find significant cooling and reductions of precipitation lasting years, which would impact the global food supply. The climate changes are large and long-lasting because the fuel loadings in modern cities are quite high and the subtropical solar insolation heats the resulting smoke cloud and lofts it into the high stratosphere, where removal mechanisms are slow. While the climate changes are less dramatic than found in previous ""nuclear winter"" simulations of a massive nuclear exchange between the superpowers, because less smoke is emitted, the changes are more long-lasting because the older models did not adequately represent the stratospheric plume rise."
"57193920163;6603735878;7004028051;7102591209;","A new parametrization for the radiative properties of ice crystals: Comparison with existing schemes and impact in a GCM",2007,"10.1016/j.atmosres.2006.03.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845686609&doi=10.1016%2fj.atmosres.2006.03.002&partnerID=40&md5=e69a204c49623e0ebad33df32e5deacb","A new parametrization of the single scattering properties of ice crystals suitable for use in general circulation models of the atmosphere is presented. The parametrization is developed from a recent treatment of the scattering properties of an ensemble of ice crystals, which has been validated against observational data and is based on a more rigorous treatment of ice optics than has been possible until recently. The new parametrization is compared with existing schemes in idealized test cases and its impact in a climate model is assessed. © 2006 Elsevier B.V. All rights reserved."
"55942083800;7003897194;7005794259;","Kinetic model framework for aerosol and cloud surface chemistry and gas-particle interactions - Part 1: General equations, parameters, and terminology",2007,"10.5194/acp-7-5989-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36949008066&doi=10.5194%2facp-7-5989-2007&partnerID=40&md5=de0447faa8259ec040a9d38df21d4404","Aerosols and clouds play central roles in atmospheric chemistry and physics, climate, air pollution, and public health. The mechanistic understanding and predictability of aerosol and cloud properties, interactions, transformations, and effects are, however, still very limited. This is due not only to the limited availability of measurement data, but also to the limited applicability and compatibility of model formalisms used for the analysis, interpretation, and description of heterogeneous and multiphase processes. To support the investigation and elucidation of atmospheric aerosol and cloud surface chemistry and gas-particle interactions, we present a comprehensive kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters. It enables a detailed description of mass transport and chemical reactions at the gas-particle interface, and it allows linking aerosol and cloud surface processes with gas phase and particle bulk processes in systems with multiple chemical components and competing physicochemical processes. The key elements and essential aspects of the presented framework are: a simple and descriptive double-layer surface model (sorption layer and quasi-static layer); straightforward flux-based mass balance and rate equations; clear separation of mass transport and chemical reactions; well-defined and consistent rate parameters (uptake and accommodation coefficients, reaction and transport rate coefficients); clear distinction between gas phase, gas-surface, and surface-bulk transport (gas phase diffusion, surface and bulk accommodation); clear distinction between gas-surface, surface layer, and surface-bulk reactions (Langmuir-Hinshelwood and Eley-Rideal mechanisms); mechanistic description of concentration and time dependences (transient and steady-state conditions); flexible addition of unlimited numbers of chemical species and physicochemical processes; optional aggregation or resolution of intermediate species, sequential processes, and surface layers; and full compatibility with traditional resistor model formulations. The outlined double-layer surface concept and formalisms represent a minimum of model complexity required for a consistent description of the non-linear concentration and time dependences observed in experimental studies of atmospheric multiphase processes (competitive co-adsorption and surface saturation effects, etc.). Exemplary practical applications and model calculations illustrating the relevance of the above aspects are presented in a companion paper (Ammann and Pöschl, 2007). We expect that the presented model framework will serve as a useful tool and basis for experimental and theoretical studies investigating and describing atmospheric aerosol and cloud surface chemistry and gas-particle interactions. It shall help to end the ""Babylonian confusion"" that seems to inhibit scientific progress in the understanding of heterogeneous chemical reactions and other multiphase processes in aerosols and clouds. In particular, it shall support the planning and design of laboratory experiments for the elucidation and determination of fundamental kinetic parameters; the establishment, evaluation, and quality assurance of comprehensive and self-consistent collections of rate parameters; and the development of detailed master mechanisms for process models and derivation of simplified but yet realistic parameterizations for atmospheric and climate models."
"13405658600;57211106013;","Efficiency of cloud condensation nuclei formation from ultrafine particles",2007,"10.5194/acp-7-1367-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847679389&doi=10.5194%2facp-7-1367-2007&partnerID=40&md5=ff0f3d95e8d5ee4165f9a77a603e6158","Atmospheric cloud condensation nuclei (CCN) concentrations are a key uncertainty in the assessment of the effect of anthropogenic aerosol on clouds and climate. The ability of new ultrafine particles to grow to become CCN varies throughout the atmosphere and must be understood in order to understand CCN formation. We have developed the Probability of Ultrafine particle Growth (PUG) model to answer questions regarding which growth and sink mechanisms control this growth, how the growth varies between different parts of the atmosphere and how uncertainties with respect to the magnitude and size distribution of ultrafine emissions translates into uncertainty in CCN generation. The inputs to the PUG model are the concentrations of condensable gases, the size distribution of ambient aerosol, particle deposition timescales and physical properties of the particles and condensable gases. It was found in most cases that condensation is the dominant growth mechanism and coagulation with larger particles is the dominant sink mechanism for ultrafine particles. In this work we found that the probability of a new ultrafine particle generating a CCN varies from <0.1% to ∼90% in different parts of the atmosphere, though in the boundary layer a large fraction of ultrafine particles have a probability between 1% and 40%. Some regions, such as the tropical free troposphere, are areas with high probabilities; however, variability within regions makes it difficult to predict which regions of the atmosphere are most efficient for generating CCN from ultrafine particles. For a given mass of primary ultrafine aerosol, an uncertainty of a factor of two in the modal diameter can lead to an uncertainty in the number of CCN generated as high as a factor for eight. It was found that no single moment of the primary aerosol size distribution, such as total mass or number, is a robust predictor of the number of CCN ultimately generated. Therefore, a complete description of the emissions size distribution is generally required for global aerosol microphysics models."
"22936711300;7006530103;7202298252;","A new algorithm to estimate sky condition based on 5 minutes-averaged values of clearness index and relative optical air mass",2007,"10.1007/s00704-006-0283-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35448994739&doi=10.1007%2fs00704-006-0283-z&partnerID=40&md5=33713ab2da363328b48f1af6c28ea290","This work describes a new algorithm to characterize sky condition in intervals of 5min using four categories of sun exposition: apparent sun with cloud reflection effects; apparent sun without cloud effects; sun partially concealed by clouds; and sun totally concealed by clouds. The algorithm can also be applied to estimate hourly and daily sky condition in terms of the traditional three categories: clear, partially cloudy and cloudy day. It identifies sky conditions within a confidence interval of 95% by minimizing local climate and measurement effects. This is accomplished by using a logistic cumulative probability function to characterize clear sky and Weibull cumulative probability function to represent cloudy sky. Both probability functions are derived from frequency distributions of clearness index, based on 5 minutes-averaged values of global solar irradiance observed at the surface during a period of 6 years in Botucatu, Southeastern of Brazil. The relative sunshine estimated from the new algorithm is statistically comparable to the one derived from Campbell-Stocks sunshine recorder for both daily and monthly values. The new method indicates that the highest frequency of clear sky days occurs in Botucatu during winter (66%) and the lowest during the summer (38%). Partially cloudy condition is the dominant feature during all months of the year. © Springer-Verlag 2007."
"35580303100;6603196127;7003420726;","Linking glacial and future climates through an ensemble of GCM simulations",2007,"10.5194/cp-3-77-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846901870&doi=10.5194%2fcp-3-77-2007&partnerID=40&md5=d5dceeb025e4a1fd33786dfb9d0f779f","In this paper we explore the relationships between the modelled climate of the Last Glacial Maximum (LGM) and that for doubled atmospheric carbon dioxide compared to the pre-industrial climate by analysing the output from an ensemble of runs from the MIROC3.2 GCM. Our results lend support to the idea in other recent work that the Antarctic is a useful place to look for historical data which can be used to validate models used for climate forecasting of future greenhouse gas induced climate changes, at local, regional and global scales. Good results may also be obtainable using tropical temperatures, particularly those over the ocean. While the greater area in the tropics makes them an attractive area for seeking data, polar amplification of temperature changes may mean that the Antarctic provides a clearer signal relative to the uncertainties in data and model results. Our result for Greenland is not so strong, possibly due to difficulties in accurately modelling the sea ice extent. The MIROC3.2 model shows an asymmetry in climate sensitivity calculated by decreasing rather than increasing the greenhouse gases, with 80% of the ensemble having a weaker cooling than warming. This asymmetry, if confirmed by other studies would mean that direct estimates of climate sensitivity from the LGM are likely to be underestimated by the order of half a degree. Our suspicion is, however, that this result may be highly model dependent. Analysis of the parameters varied in the model suggest the asymmetrical response may be linked to the ice in the clouds, which is therefore indicated as an important area for future research."
"6506928993;15766289100;","Estimation of global solar radiation in arid and semi-arid climates of East and West Iran",2007,"10.1016/j.energy.2006.05.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846253978&doi=10.1016%2fj.energy.2006.05.005&partnerID=40&md5=117e8285684eb0d570405a0db47f7ada","In Iran, most of the models used so far, have provided solar estimation for a few specific locations based on the short-term solar observations. Using different radiation models, (e.g. Sabbagh, Paltridge-Proctor, Daneshyar) and various input parameters (e.g. cloud cover, sunshine duration, relative humidity, temperature, and altitude) we developed a general height-depended formula for the prediction of the direct and diffuse monthly average daily solar radiation for 64 mountainous arid and semi-arid locations in West and East Iran. The models mentioned are modified and new coefficients are defined for the diffuse component based on the long-term observed diffuse data. Model results are validated against up to 13-year daily solar observations at 10 solar radiation sites. In comparison with the previous studies, the newly developed method performs more accurate estimation (less than 3% MPE error) in the arid and semi-arid regions. Comparison of the model results indicates that calibration of the coefficients made to the diffuse formula against the longer period experimental data can improve the estimations of global solar radiation. © 2006 Elsevier Ltd. All rights reserved."
"57201561519;6701555756;55959258000;","On periodicities in long term climatic variations near 68°N, 30°E",2007,"10.5194/adgeo-13-25-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547805576&doi=10.5194%2fadgeo-13-25-2007&partnerID=40&md5=ce3f9d5d8a4a2d42c40cce08ef182434","It is generally believed that the low-frequency variability of climatic parameters seems to be connected to solar cycles. The principal periodicities are: 11-year (Schwabe), 22-year (Hale), 33-year (Bruckner) and 80-100-year (Gleissberg) cycles. The main heliophysical factors acting on climate, the biosphere and the atmosphere are solar irradiance, the intensity of solar and galactic cosmic rays (relativistic charged particles with energies >500MeV) changing the cloud cover of the atmosphere, and UV-B-radiation. The 11-year and 80-90-year solar cycles are apparent in solar radiation and galactic cosmic ray trends. At the same time the bidecadal Hale cycle, related to a reversal of the main solar magnetic field direction is practically absent in either solar radiation or galactic cosmic ray variations. Besides, nobody can identify any physical mechanisms by which a reversal in the solar magnetic field direction could influence climate. However, the 22-year cycle has been identified in rather many regional climatic (droughts, rainfall, tree growth near 68°N, 30°E) and temperature records all over the world. We discuss here three possible cause of the bidecadal periodicity in climatic records, one of which is associated with a variation of stardust flux inside the Solar System. The most recent observations by the DUST experiment on board the Ulysses spacecraft have shown that the solar magnetic field lost its protective power during the last change of its polarity (the most recent solar maximum), so that the stardust level inside of the Solar System has been enhanced by a factor of three. It is possible that the periodic increases of stardust in the Solar System may influence the amount of extraterrestrial material that falls to the Earth and consequently act on the Earth's atmosphere and climate through alteration of atmospheric transparency and albedo. This material (interstellar dust and/or cometary matter) may also provide nucleation sites and thereby influence precipitation."
"16029830700;57215342063;","Climatic satellite monitoring of the external heat balance of the oceans and Black Sea",2007,"10.1007/s11110-008-9000-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55549086131&doi=10.1007%2fs11110-008-9000-z&partnerID=40&md5=3688e198b3be662b576a27f1d2f1fdd9","The long-wave outgoing radiation, effective cloudiness equal to the product of the total cloud amount by their optical density, and the sea-surface temperature determined from the satellites are used to determine the annual course of the components of external heat balance on the sea surface whose climatic anomalies, parallel with the meridional heat and water transfer in the ocean-atmosphere system, specify the intraannual and interannual large-scale variations of weather in different regions of the Earth. The development of these studies is connected with the progress of satellite hydrophysics because the data obtained from the space become sufficiently exact, regular, and global. The increase in the existing data array on the external heat balance of the oceans from ∼15-20 to 100 yr and more would promote the solution of the problem of oscillations of Earth's climate. We present examples of coordinated numerical analysis of the heat balance of the upper (0-100 m) layer of the Black Sea performed on the basis of the shipborne and satellite data. © Springer Science+Business Media, Inc. 2007."
"13405658600;55567649200;57211106013;","Contribution of primary carbonaceous aerosol to cloud condensation nuclei: Processes and uncertainties evaluated with a global aerosol microphysics model",2007,"10.5194/acp-7-5447-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35349022142&doi=10.5194%2facp-7-5447-2007&partnerID=40&md5=28027aa12661595ecf1c87bc651201e5","This paper explores the impacts of primary carbonaceous aerosol on cloud condensation nuclei (CCN) concentrations in a global climate model with size-resolved aerosol microphysics. Organic matter (OM) and elemental carbon (EC) from two emissions inventories were incorporated into a preexisting model with sulfate and sea-salt aerosol. The addition of primary carbonaceous aerosol increased CCN(0.2%) concentrations by 65-90% in the globally averaged surface layer depending on the carbonaceous emissions inventory used. Sensitivity studies were performed to determine the relative importance of organic solubility/hygroscopicity in predicting CCN. In a sensitivity study where carbonaceous aerosol was assumed to be completely insoluble, concentrations of CCN(0.2%) still increased by 40-50% globally over the no carbonaceous simulation because primary carbonaceous emissions were able to become CCN via condensation of sulfuric acid. This shows that approximately half of the contribution of primary carbonaceous particles to CCN in our model comes from the addition of new particles (seeding effect) and half from the contribution of organic solute (solute effect). The solute effect tends to dominate more in areas where there is less inorganic aerosol than organic aerosol and the seeding effect tends to dominate in areas where there is more inorganic aerosol than organic aerosol. It was found that an accurate simulation of the number size distribution is necessary to predict the CCN concentration but assuming an average chemical composition will generally give a CCN concentration within a factor of 2. If a ""typical"" size distribution is assumed for each species when calculating CCN, such as is done in bulk aerosol models, the mean error relative to a simulation with size resolved microphysics is on the order of 35%. Predicted values of carbonaceous aerosol mass and aerosol number were compared to observations and the model showed average errors of a factor of 3 for carbonaceous mass and a factor of 4 for total aerosol number; however, errors in the accumulation mode concentrations were found to be lower in comparisons with European and marine observations.. The errors in CN and carbonaceous mass may be reduced by improving the emission size distributions of both primary sulfate and primary carbonaceous aerosol."
"11339401400;7005219614;","Reformulating atmospheric aerosol thermodynamics and hygroscopic growth into fog, haze and clouds",2007,"10.5194/acp-7-3163-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347210343&doi=10.5194%2facp-7-3163-2007&partnerID=40&md5=5a88d8e61a8d4e4fe8ffbd55b716bffd","Modeling atmospheric aerosol and cloud microphysics is rather complex, even if chemical and thermodynamical equilibrium is assumed. We show, however, that the thermodynamics can be considerably simplified by reformulating equilibrium to consistently include water, and transform laboratory-based concepts to atmospheric conditions. We generalize the thermodynamic principles that explain hydration and osmosis - merely based on solute solubilities - to explicitly account for the water mass consumed by hydration. As a result, in chemical and thermodynamical equilibrium the relative humidity (RH) suffices to determine the saturation molality, including solute and solvent activities (and activity coefficients), since the water content is fixed by RH for a given aerosol concentration and type. As a consequence, gas/liquid/solid aerosol equilibrium partitioning can be solved analytically and non-iteratively. Our new concept enables an efficient and accurate calculation of the aerosol water mass and directly links the aerosol hygroscopic growth to fog, haze and cloud formation. We apply our new concept in the 3rd Equilibrium Simplified Aerosol Model (EQSAM3) for use in regional and global chemistry-transport and climate models. Its input is limited to the species' solubilities from which a newly introduced stoichiometric coefficient for water is derived. Analogously, we introduce effective stoichiometric coefficients for the solutes to account for complete or incomplete dissociation. We show that these coefficients can be assumed constant over the entire activity range and calculated for various inorganic, organic and non-electrolyte compounds, including alcohols, sugars and dissolved gases. EQSAM3 calculates the aerosol composition and gas/liquid/solid partitioning of mixed inorganic/organic multicomponent solutions and the associated water uptake for almost 100 major compounds. It explicitly accounts for particle hygroscopic growth by computing aerosol properties such as single solute molalities, molal based activities, including activity coefficients for volatile compounds, efflorescence and deliquescence relative humidities of single solute and mixed solutions. Various applications and a model inter-comparison indicate that a) the application is not limited to dilute binary solutions, b) sensitive aerosol properties such as hygroscopic growth and the pH of binary and mixed inorganic/organic salt solutions up to saturation can be computed accurately, and c) aerosol water is central in modeling atmospheric chemistry, visibility, weather and climate."
"15828928500;57211106013;56472932500;","Sensitivity of PM2.5 to climate in the Eastern US: A modeling case study",2007,"10.5194/acp-7-4295-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548224223&doi=10.5194%2facp-7-4295-2007&partnerID=40&md5=7ebbf99a9d951bf1d28652e2ae6554c1","The individual effects of various meteorological parameters on PM 2.5 concentrations in the Eastern US are examined using the PMCAMx chemical transport model so that these effects and their relative magnitudes can be better understood. A suite of perturbations in temperature, wind speed, absolute humidity, mixing height, cloud cover, and precipitation are imposed individually on base case conditions corresponding to periods in July 2001 and January 2002 in order to determine the sensitivities of PM2.5 concentrations and composition to these separate meteorological parameters. Temperature had a major effect on average PM2.5 in January (-170 ng m-3 K-1) due largely to the evaporation of ammonium nitrate and organic aerosol at higher temperatures; increases in sulfate production with increased temperature counteracted much of this decrease in July. Changes in mixing height also had major effects on PM2.5 concentrations: 73 ng m-3 (100 m)-1 in January and 210 ng m-3 (100 m)-1 in July. Changes in wind speed (30 to 55 ng m-3 %-1) and absolute humidity (15 to 20 ng m-3 %-1) also had appreciable effects on average PM2.5 concentrations. Precipitation changes had large impacts on parts of the domain (a consequence of the base case meteorology), with sensitivities to changing area of precipitation in July up to 100 ng m-3 %-1. Perturbations in cloud cover had the smallest effects on average PM 2.5 concentrations. The changes in PM2.5 concentrations resulting from changing all eight meteorological parameters simultaneously were approximately within 25% or so of the sum of the changes to the eight individual perturbations. The sensitivities of PM2.5 concentrations to changes in these meteorological parameters indicate that changes in climate could potentially have important impacts on PM2.5 concentrations."
"16317230600;6701633912;57196396429;","Radiation budget estimates over Africa and surrounding oceans: Inter-annual comparisons",2007,"10.5194/acp-7-2617-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249104501&doi=10.5194%2facp-7-2617-2007&partnerID=40&md5=326d367bd385082fe9e86d6e475f4f3a","Three independent datasets of Radiation Budget at the top of the atmosphere (TOA) spanning two decades are compared: the Scanner Narrow Field of View data (from ERBE, ScaRaB, and CERES instruments, 1985-2005), the ERBS Nonscanner Wide Field of View data (1985-1998) and the simulated broadband fluxes from the International Satellite Cloud Climatology Project (ISCCP-FD, 1983-2004). The analysis concerns the shortwave (SW) reflected flux, the longwave (LW) emitted flux and the net flux at the Top Of the Atmosphere (TOA) over Africa and the surrounding oceans (45° S-45° N/60° W-60° E), a region particularly impacted by climate variability. For each month, local anomalies are computed with reference to the average over this large region, and their differences between the 2002-2005 and 1985-1989 periods are analysed. These anomalies are, for a large part, independent on the general observed trends (about 2.5 W m-2 per decade), which may be affected by possible calibration drifts. Although the regional flux anomalies can be related to calibration through the scene identification and the choice of the anisotropy correction, this effect is limited if the calibration drifts remains reasonable. Large inter-annual variations are observed locally. Over a part of the South East Atlantic (35°-10° S/10° W-10° E), including the marine low cloud area off Angola, there is a decrease of the yearly means of net flux estimated to 2.2, 3 and 6 W m-2 respectively for the Scanner, Nonscanner and ISCPP-FD data. Over a narrow strip of the Sahel Zone, the net flux increases by about 5 W m-2. We believe that these observations are real. They could be due to the impact of calibration drift but only if the drifts were significant (&gt;4%) and correlated between the datasets, which is highly improbable."
"7004952586;36692256000;","Climate and land degradation — an overview",2007,"10.1007/978-3-540-72438-4_6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006288051&doi=10.1007%2f978-3-540-72438-4_6&partnerID=40&md5=8b51571768e997e87d2d343893b3819d","The definition of land degradation in the United Nations Convention to Combat Desertification (UNCCD) gives explicit recognition to climatic variations as one of the major factors contributing to land degradation. In order to accurately assess sustainable land management practices, the climate resources and the risk of climate-related or induced natural disasters in a region must be known. Land surface is an important part of the climate system and changes of vegetation type can modify the characteristics of the regional atmospheric circulation and the large-scale external moisture fluxes. Following deforestation, surface evapotranspiration and sensible heat flux are related to the dynamic structure of the low-level atmosphere and these changes could influence the regional, and potentially, global-scale atmospheric circulation. Surface parameters such as soil moisture, forest coverage, transpiration and surface roughness may affect the formation of convective clouds and rainfall through their effect on boundary-layer growth. Land use and land cover changes influence carbon fluxes and GHG emissions which directly alter atmospheric composition and radiative forcing properties. Land degradation aggravates CO2-induced climate change through the release of CO2 from cleared and dead vegetation and through the reduction of the carbon sequestration potential of degraded land. Climate exerts a strong influence over dry land vegetation type, biomass and diversity. Precipitation and temperature determine the potential distribution of terrestrial vegetation and constitute principal factors in the genesis and evolution of soil. Precipitation also influences vegetation production, which in turn controls the spatial and temporal occurrence of grazing and favours nomadic lifestyle. The generally high temperatures and low precipitation in the dry lands lead to poor organic matter production and rapid oxidation. Low organic matter leads to poor aggregation and low aggregate stability leading to a high potential for wind and water erosion. The severity, frequency, and extent of erosion are likely to be altered by changes in rainfall amount and intensity and changes in wind. Impacts of extreme events such as droughts, sand and dust storms, floods, heat waves, wild fires etc., on land degradation are explained with suitable examples. Current advances in weather and climate science to deal more effectively with the impacts of different climatic parameters on land degradation are explained with suitable examples. Several activities promoted by WMO’s programmes around the world help promote a better understanding of the interactions between climate and land degradation through dedicated observations of the climate system; improvements in the application of agrometeorological methods and the proper assessment and management of water resources; advances in climate science and prediction; and promotion of capacity building in the application of meteorological and hydrological data and information in drought preparedness and management. The definition of land degradation adopted by UNCCD assigns a major importance to climatic factors contributing to land degradation, but there is no concerted effort at the global level to systematically monitor the impacts of different climatic factors on land degradation in different regions and for different classes of land degradation. Hence there is an urgent need to monitor the interactions between climate and land degradation. To better understand these interactions, it is also important to identify the sources and sinks of dryland carbon, aerosols and trace gases in drylands. This can be effectively done through regional climate monitoring networks. Such networks could also help enhance the application of seasonal climate forecasting for more effective dryland management. © 2007, Springer-Verlag Berlin Heidelberg."
"7202459859;9249296100;8750834400;8420354200;6701778684;7402452055;55576176900;7003567733;20434196300;","Longwave Infrared Camera onboard the Venus Climate Orbiter",2007,"10.1016/j.asr.2007.05.085","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548221053&doi=10.1016%2fj.asr.2007.05.085&partnerID=40&md5=4a86a7a3226c497ff4956178cf1f1fec","The Longwave Infrared Camera (LIR) onboard the first Japanese Venus mission, PLANET-C, or the Venus Climate Orbiter, operates in the middle infrared region with a single bandpass filter of 8-12 μm, measuring thermal radiation emitted from the cloud tops of the Venusian atmosphere. A horizontal wind vector field at the cloud-top height will be retrieved by means of a cloud tracking method. In addition, absolute temperature will be determined with an accuracy of 3 K. Since solar irradiation scattered by the atmosphere is much weaker than the atmospheric thermal radiation, LIR can continuously monitor a hemispheric wind field independent of the local time of the apocenter throughout the mission life. Wind and temperature fields obtained by LIR will provide key parameters to solve climatological issues related to the Venusian atmosphere. The use of an uncooled micro-bolometer array (UMBA), which requires no cryogenic apparatus, as an image sensor contributes to the reduction of power consumption and the weight of the LIR imager. An instrumental field-of-view of 12° is equal to the angle subtended by Venus when observed from a height of 9.5 Rv. The pixel field-of-view corresponds to a spatial resolution of 70 km viewed from the apocenter. A mechanical shutter functions not only as an optical shutter but also as a reference blackbody. The temperature stability of the sensor is especially important, because fluctuation of thermal radiation from the internal environment of the sensor itself causes background noise. Therefore, the temperature of the UMBA package is stabilized at 313 ± 0.1 K with a feedback controlled Peltier cooler/heater, and a NETD of 0.3 K, which is required for this infrared imager, will be achieved. Flat field images are taken with the shutter closed several seconds before and after 1 s exposure for a Venus thermal image. After a Venus image is taken, the LIR imager takes a cold calibration image of deep space. This measurement sequence is repeated every two hours when the spacecraft is orbiting at apocenter. Image data are transmitted down to the Earth after onboard calibration and data compression by common digital electronics. © 2007 COSPAR."
"57211223914;","Role of land-atmosphere interaction on Asian monsoon climate",2007,"10.2151/jmsj.85B.55","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34848924933&doi=10.2151%2fjmsj.85B.55&partnerID=40&md5=072c93f4e9e0ff621818ed66528f88bf","This paper has discussed the land-atmosphere interaction associated with the Asian monsoon climate and its variability. The snow cover and soil moisture are internal factors of the climate system particularly in the seasonal to interannual time scales, but are suggested to play some important roles in changing large-scale surface energy and water balance, which in turn affect the monsoon circulation and precipitation. From the modeling as well as observational studies it has been suggested that the snow cover is most likely to influence atmosphere essentially through the albedo effect particularly in lower latitudes and on the Tibetan Plateau. The GCM experiments have strongly suggested that soil moisture anomalies efficiently affect the atmosphere under dry or semi-arid condition. Vegetation has also been noted as an important variable for the formation of moist monsoon flow over the continent, in addition to the dynamical and thermo-dynamical effect of the Tibetan Plateau. Through the GCM and RCM experiments the anthropogenically-induced change of land cover/use including the deforestation has proved to be a great impact on regional precipitation and water cycle of the monsoon region by changing characteristics of vegetation control in energy and water cycle, which in turn affect atmospheric boundary layer (ABL) and cloud/ precipitation processes in regional-scale. The discussion has also been made on how the land surface changes could induce change of precipitation through feedback processes of moisture convergence and in-situ evapo-transpiration processes. The critical role of moisture amount near surface and in the ABL is emphasized, to induce positive feedback to change of precipitation over land in the monsoon region. © 2007, Meteorological Society of Japan."
"7402124779;","Evidence for a physical linkage between galactic cosmic rays and regional climate time series",2007,"10.1016/j.asr.2007.02.079","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547407803&doi=10.1016%2fj.asr.2007.02.079&partnerID=40&md5=23806899a8479b0047d36041c48f09f6","The effects of solar variability on regional climate time series were examined using a sequence of physical connections between total solar irradiance (TSI) modulated by galactic cosmic rays (GCRs), and ocean and atmospheric patterns that affect precipitation and streamflow. The solar energy reaching the Earth's surface and its oceans is thought to be controlled through an interaction between TSI and GCRs, which are theorized to ionize the atmosphere and increase cloud formation and its resultant albedo. High (low) GCR flux may promote cloudiness (clear skies) and higher (lower) albedo at the same time that TSI is lowest (highest) in the solar cycle which in turn creates cooler (warmer) ocean temperature anomalies. These anomalies have been shown to affect atmospheric flow patterns and ultimately affect precipitation over the Midwestern United States. This investigation identified a relation among TSI and geomagnetic index aa (GI-AA), and streamflow in the Mississippi River Basin for the period 1878-2004. The GI-AA was used as a proxy for GCRs. The lag time between the solar signal and streamflow in the Mississippi River at St. Louis, Missouri is approximately 34 years. The current drought (1999-2007) in the Mississippi River Basin appears to be caused by a period of lower solar activity that occurred between 1963 and 1977. There appears to be a solar ""fingerprint"" that can be detected in climatic time series in other regions of the world, with each series having a unique lag time between the solar signal and the hydroclimatic response. A progression of increasing lag times can be spatially linked to the ocean conveyor belt, which may transport the solar signal over a time span of several decades. The lag times for any one region vary slightly and may be linked to the fluctuations in the velocity of the ocean conveyor belt."
"55393706100;55965624000;7004168515;9250463400;15127430500;","Nitrogen compounds and ozone in the stratosphere: Comparison of MIPAS satellite data with the chemistry climate model ECHAM5/MESSy1",2007,"10.5194/acp-7-5585-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36048997261&doi=10.5194%2facp-7-5585-2007&partnerID=40&md5=725a2172737b8adafae845905a246601","The chemistry climate model ECHAM5/MESSy1 (E5/M1) in a setup extending from the surface to 80 km with a vertical resolution of about 600 m near the tropopause with nudged tropospheric meteorology allows a direct comparison with satellite data of chemical species at the same time and location. Here we present results out of a transient 10∼years simulation for the period of the Antarctic vortex split in September 2002, where data of MIPAS on the ENVISAT-satellite are available. For the first time this satellite instrument opens the opportunity, to evaluate all stratospheric nitrogen containing species simultaneously with a good global coverage, including the source gas N 2O and ozone which allows an estimate for NOx-production in the stratosphere. We show correlations between simulated and observed species in the altitude region between 10 and 50 hpa for different latitude belts, together with the Probability Density Functions (PDFs) of model results and observations. This is supplemented by global maps on pressure levels showing the comparison between the satellite and the simulated data sampled at the same time and location. We demonstrate that the model in most cases captures the partitioning in the nitrogen family, the diurnal cycles and the spatial distribution within experimental uncertainty. This includes even variations due to tropospheric clouds. There appears to be, however, a problem to reproduce the observed nighttime partitioning between N2O5 and NO 2 in the middle stratosphere using the recommended set of reaction coefficients and photolysis data."
"57208121852;57196499374;56270311300;57203200427;","Aerosol absorption and radiative forcing",2007,"10.5194/acp-7-5237-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35048822891&doi=10.5194%2facp-7-5237-2007&partnerID=40&md5=c383e060206e46d0925a1591a0271d58","We present a comprehensive examination of aerosol absorption with a focus on evaluating the sensitivity of the global distribution of aerosol absorption to key uncertainties in the process representation. For this purpose we extended the comprehensive aerosol-climate model ECHAM5HAM by effective medium approximations for the calculation of aerosol effective refractive indices, updated black carbon refractive indices, new cloud radiative properties considering the effect of aerosol inclusions, as well as by modules for the calculation of long-wave aerosol radiative properties and instantaneous aerosol forcing. The evaluation of the simulated aerosol absorption optical depth with the AERONET sun-photometer network shows a good agreement in the large scale global patterns. On a regional basis it becomes evident that the update of the BC refractive indices to Bond and Bergstrom (2006) significantly improves the previous underestimation of the aerosol absorption optical depth. In the global annual-mean, absorption acts to reduce the shortwave anthropogenic aerosol top-of-atmosphere (TOA) radiative forcing clear-sky from -0.79 to -0.53Wm -2 (33%) and all-sky from -0.47 to -0.13Wm-2 (72%). Our results confirm that basic assumptions about the BC refractive index play a key role for aerosol absorption and radiative forcing. The effect of the usage of more accurate effective medium approximations is comparably small. We demonstrate that the diversity in the AeroCom land-surface albedo fields contributes to the uncertainty in the simulated anthropogenic aerosol radiative forcings: the usage of an upper versus lower bound of the AeroCom land albedos introduces a global annual-mean TOA forcing range of 0.19Wm-2 (36%) clear-sky and of 0.12Wm-2 (92%) all-sky. The consideration of black carbon inclusions on cloud radiative properties results in a small global annual-mean all-sky absorption of 0.05 W m-2 and a positive TOA forcing perturbation of 0.02 Wm-2. The long-wave aerosol radiative effects are small for anthropogenic aerosols but become of relevance for the larger natural dust and sea-salt aerosols."
"55684491100;6602743250;","The global lightning-induced nitrogen oxides source",2007,"10.5194/acp-7-3823-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547503251&doi=10.5194%2facp-7-3823-2007&partnerID=40&md5=571de79b59a55d1c47b625d903891b28","The knowledge of the lightning-induced nitrogen oxides (LNOx) source is important for understanding and predicting the nitrogen oxides and ozone distributions in the troposphere and their trends, the oxidising capacity of the atmosphere, and the lifetime of trace gases destroyed by reactions with OH. This knowledge is further required for the assessment of other important NOx sources, in particular from aviation emissions, the stratosphere, and from surface sources, and for understanding the possible feedback between climate changes and lightning. This paper reviews more than 3 decades of research. The review includes laboratory studies as well as surface, airborne and satellite-based observations of lightning and of NOx and related species in the atmosphere. Relevant data available from measurements in regions with strong LNOx influence are identified, including recent observations at midlatitudes and over tropical continents where most lightning occurs. Various methods to model LNOx at cloud scales or globally are described. Previous estimates are re-evaluated using the global annual mean flash frequency of 44±5 s-1 reported from OTD satellite data. From the review, mainly of airborne measurements near thunderstorms and cloud-resolving models, we conclude that a ""typical"" thunderstorm flash produces 15 (2-40) × 1025 NO molecules per flash, equivalent to 250 mol NOx or 3.5 kg of N mass per flash with uncertainty factor from 0.13 to 2.7. Mainly as a result of global model studies for various LNOx parameterisations tested with related observations, the best estimate of the annual global LNOx nitrogen mass source and its uncertainty range is (5±3) Tg a-1 in this study. In spite of a smaller global flash rate, the best estimate is essentially the same as in some earlier reviews, implying larger flash-specific NOx emissions. The paper estimates the LNOx accuracy required for various applications and lays out strategies for improving estimates in the future. An accuracy of about 1 Tg a-1 or 20%, as necessary in particular for understanding tropical tropospheric chemistry, is still a challenging goal."
"9240649600;6506840408;","Role of the quasi-biweekly oscillation in the onset of convection over the Indochina Peninsula",2007,"10.1002/qj.38","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247262550&doi=10.1002%2fqj.38&partnerID=40&md5=c45eb1e55f6d81d861fb23fc320051bb","The characteristics of convection onset over the Indochina Peninsula and its possible mechanism are investigated using the reanalysis of the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and the black-body temperature at the top of the cloud (TBB). Results show that the convection onset occurs before the systemic northward progression of the tropical convection and is earlier than the onset of the summer monsoon over this region. The prominent difference between the onset of convection and that of the summer monsoon appears in the westmost part of the western Pacific subtropical high. When the convection bursts, the Indochina Peninsula is under the control of the western Pacific subtropical high. However, the summer monsoon onset follows the splitting of the subtropical high belt and the eastward retreat of the western Pacific subtropical high out of the Indochina Peninsula. The climatological features of TBB over the Indochina Peninsula indicate that the convective activities have a close relationship with the quasi-biweekly oscillation (QBWO). Based on the onset dates determined by the TBB data, case-studies and composite analyses are implemented on exploring the possible mechanism of the convection onset. It is found that the onset of convection is mainly influenced by factors as follows. The wet phase of QBWO of the tropical convection propagates northward from Sumatra to the Indochina Peninsula. Over the southern Indochina Peninsula, anomalous southerlies (the Rossby wave response to the tropical convective QBWO) are beneficial to both the northward progression of the convective disturbances and the convergence of the low-level moisture flux. Furthermore, the Indochina Peninsula is easily affected by any cold surge invading southwards from higher latitudes, which intensifies the convective activities when merging with the wet/warm current. Copyright © 2007 Royal Meteorological Society."
"7005340164;7103404891;11939854600;53869217500;11940493400;8306414700;7004322783;8306414900;6602372956;7003548766;55768583400;8306415500;7006630335;6603789210;7006056992;8306416700;55974002300;55888382600;23101961400;15832524500;16402249500;23396194300;13007432800;7003836537;35241110500;6507349253;6507998364;15831054000;25421638300;56184780700;8306416400;6508343331;","HISTALP - Historical instrumental climatological surface time series of the Greater Alpine Region",2007,"10.1002/joc.1377","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846494907&doi=10.1002%2fjoc.1377&partnerID=40&md5=4a2c47a7d47d1573c3261e0370953fcf","This paper describes the HISTALP database, consisting of monthly homogenised records of temperature, pressure, precipitation, sunshine and cloudiness for the 'Greater Alpine Region' (GAR, 4-19°E, 43-49°N, 0-3500m asl). The longest temperature and air pressure series extend back to 1760, precipitation to 1800, cloudiness to the 1840s and sunshine to the 1880s. A systematic QC procedure has been applied to the series and a high number of inhomogeneities (more than 2500) and outliers (more than 5000) have been detected and removed. The 557 HISTALP series are kept in different data modes: original and homogenised, gap-filled and outlier corrected station mode series, grid-1 series (anomaly fields at 1° × 1°, lat × long) and Coarse Resolution Subregional (CRS) mean series according to an EOF-based regionalisation. The leading climate variability features within the GAR are discussed through selected examples and a concluding linear trend analysis for 100, 50 and 25-year subperiods for the four horizontal and two altitudinal CRSs. Among the key findings of the trend analysis is the parallel centennial decrease/increase of both temperature and air pressure in the 19th/20th century. The 20th century increase (+1.2°C/+1.1 hPa for annual GAR-means) evolved stepwise with a first peak near 1950 and the second increase (1.3°C/0.6hPa per 25 years) starting in the 1970s. Centennial and decadal scale temperature trends were identical for all subregions. Air pressure, sunshine and cloudiness show significant differences between low versus high elevations. A long-term increase of the high-elevation series relative to the low-elevation series is given for sunshine and air pressure. Of special interest is the exceptional high correlation near 0.9 between the series on mean temperature and air pressure difference (high-minus low-elevation). This, further developed via some atmospheric statics and thermodynamics, allows the creation of 'barometric temperature series' without use of the measures of temperature. They support the measured temperature trends in the region. Precipitation shows the most significant regional and seasonal differences with, e.g., remarkable opposite 20th century evolution for NW (9% increase) versus SE (9% decrease). Other long- and short-term features are discussed and indicate the promising potential of the new database for further analyses and applications. Copyright © 2006 Royal Meteorological Society."
"7102696820;","Simulation of weather systems over Indian region using mesoscale models",2007,"10.1007/s00703-006-0188-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845268005&doi=10.1007%2fs00703-006-0188-5&partnerID=40&md5=1c2b099596b7819b7b57655a4f7c7446","Simulation studies have been carried out for two weather systems namely; a pre-monsoon thunderstorm over east coast of India and a weak cyclonic circulation associated with feeble low pressure area over south peninsular India. Two sets of forecast results are obtained: one using Advanced Regional Prediction System Model and other using Weather Research and Forecasting Model. The model performances are compared by examining the predicted parameters like mean sea level pressure, wind, moisture fields and rainfall. The rainfall prediction is assessed qualitatively by comparing the spatial distribution with satellite cloud images and quantitatively by comparing rainfall rates with Tropical Rainfall Measuring Mission products and/or the observed station values reported in Indian Daily Weather Reports. It is found that in case of idealized simulation of thunderstorm, Advanced Regional Prediction System Model has well predicted the spatial distribution of rainfall which is consistent with the clouding in satellite cloud images. It also has simulated the diverging winds at lower levels associated with downdraft during mature/dissipation stage of thunderstorm. Weather Research and Forecasting Model failed to predict these features. In case of a weak cyclonic circulation simulation experiment, Advanced Regional Prediction System model is able to simulate the rainy area better compared to those produced by Weather Research and Forecasting Model. Both models failed to produce observed heavy precipitation rates. © Springer-Verlag 2006."
"8982748700;16312624300;","Evaluation of surface water and energy cycles in the Met Office global NWP model using CEOP data",2007,"10.2151/jmsj.85A.43","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248654032&doi=10.2151%2fjmsj.85A.43&partnerID=40&md5=530e5276951af381f4d7f120d1657909","Components of the surface water and energy balance are evaluated in the Met Office global Numerical Weather Prediction (NWP) 00-36 hour forecasts using (i) GEWEX Continental Scale Experiment (CSE) reference site data provided by the Coordinated Enhanced Observing Period (CEOP) project and (ii) other earth observing datasets from satellites and in-situ measurements. The global hydrological cycle in the model is in reasonable balance in recent model versions. However, comparison against available observations suggest that both precipitation and evaporation are overestimated over both land and ocean, with largest errors over the tropical oceans. Comparison of the model's seasonal and diurnal cycles of surface fluxes, temperature, precipitation, and moisture against the GEWEX/CEOP CSE sites during October 2002 to September 2003 reveals several issues concerning model parametrization performance. For the high latitude (Arctic) sites low cloud is overestimated during boreal winter leading to an enhanced greenhouse effect and too warm near surface temperatures in the model. Snow melt occurs too early in boreal spring in the model forecasts which currently have no snow analysis component. Possible reasons for early snow melt are discussed including the specification of albedo over heterogeneous terrain and excessive sublimation of snow in the model. The mid-latitude CEOP sites all show excessive evaporation and precipitation during boreal spring and early summer and comparison with the International Satellite Cloud Climatology (ISCCP) products show systematic under prediction of cloud cover over mid-latitude land in summer. Some of the largest biases in mid-latitude surface fluxes in summer are during daytime on non-precipitating cloudy days where the model overestimates the downward SW radiation, latent and sensible heat fluxes. Finally, over tropical land we see a tendency to underestimate precipitation which is in direct contrast to tropical oceans where precipitation accumulations are too large. We have also used the CEOP data to investigate structural errors in the vertical profiles of tropical humidity which suggest deficiencies in the convection scheme."
"14032451700;11840367400;7201634460;11839001400;57192878672;27067971800;","Smoke plume detection in the eastern United States using MODIS",2007,"10.1080/01431160701236795","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547114995&doi=10.1080%2f01431160701236795&partnerID=40&md5=dfa59bd968439cfcd9c4420bb0e00fc4","In the eastern United States large amounts of smoke emitted from both wildfires and prescribed fires affect the regional air quality and long-term climate and may have an impact on public health. Satellite remote sensing is an effective approach for detecting and monitoring the smoke plume. The spectral characteristics of smoke plume are measurably different from those of other cover types, such as vegetation, cloud, snow, and so on. A multi-threshold method has been developed for detecting smoke plumes with eight MODIS spectral bands based on the analysis of spectral characteristics of different cover types. A series of tests are applied to all pixels in one granule (5-min measurements) to filter out non-smoke pixels step by step with water masking. At each step, specific thresholds are utilized. The results have been validated with true color images for a number of cases from different areas and time, showing that the algorithm works well except for a few missing or incorrect identified smoke pixels."
"6508186167;7005132173;","The oleic acid-ozone heterogeneous reaction system: Products, kinetics, secondary chemistry, and atmospheric implications of a model system - A review",2007,"10.5194/acp-7-1237-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847686286&doi=10.5194%2facp-7-1237-2007&partnerID=40&md5=12b38b8c7c42566e858065052a3e666e","The heterogeneous processing of organic aerosols by trace oxidants has many implications to atmospheric chemistry and climate regulation. This review covers a model heterogeneous reaction system (HRS): the oleic acidozone HRS and other reaction systems featuring fatty acids, and their derivatives. The analysis of the commonly observed aldehyde and organic acid products of ozonolysis (azelaic acid, nonanoic acid, 9-oxononanoic acid, nonanal) is described. The relative product yields are noted and explained by the observation of secondary chemical reactions. The secondary reaction products arising from reactive Criegee intermediates are mainly peroxidic, notably secondary ozonides and α-acyloxyalkyl hydroperoxide oligomers and polymers, and their formation is in accord with solution and liquid-phase ozonolysis. These highly oxygenated products are of low volatility and hydrophilic which may enhance the ability of particles to act as cloud condensation nuclei (CCN). The kinetic description of this HRS is critically reviewed. Most kinetic studies suggest this oxidative processing is either a near surface reaction that is limited by the diffusion of ozone or a surface based reaction. Internally mixed particles and coatings represent the next stage in the progression towards more realistic proxies of tropospheric organic aerosols and a description of the products and the kinetics resulting from the ozonolysis of these proxies, which are based on fatty acids or their derivatives, is presented. Finally, the main atmospheric implications of oxidative processing of particulate containing fatty acids are presented. These implications include the extended lifetime of unsaturated species in the troposphere facilitated by the presence of solids, semi-solids or viscous phases, and an enhanced rate of ozone uptake by particulate unsaturates compared to corresponding gas-phase organics. Ozonolysis of oleic acid enhances its CCN activity, which implies that oxidatively processed particulate may contribute to indirect forcing of radiation."
"56213441200;8581743700;57202099430;9250463400;55906891500;8514315800;8791306500;8667824800;56102017200;9942129100;9233214000;7004168515;26025794900;8309515600;8088667200;36829694300;56278992200;8088667300;6601996394;7005450158;7004005128;8378887500;56572656100;8348401800;16444930500;55947319900;6603102974;6602579458;7007168548;6701324251;55738885600;","Bias determination and precision validation of ozone profiles from MIPAS-Envisat retrieved with the IMK-IAA processor",2007,"10.5194/acp-7-3639-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547375293&doi=10.5194%2facp-7-3639-2007&partnerID=40&md5=2ef2c12312cb9d2fd609bf5cb7ce41eb","This paper characterizes vertical ozone profiles retrieved with the IMK-IAA (Institute for Meteorology and Climate Research, Karlsruhe &ndash; Instituto de Astrofisica de Andalucia) science-oriented processor from high spectral resolution data (until March 2004) measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the environmental satellite Envisat. Bias determination and precision validation is performed on the basis of correlative measurements by ground-based lidars, Fourier transform infrared spectrometers, and microwave radiometers as well as balloon-borne ozonesondes, the balloon-borne version of MIPAS, and two satellite instruments (Halogen Occultation Experiment and Polar Ozone and Aerosol Measurement III). Percentage mean differences between MIPAS and the comparison instruments for stratospheric ozone are generally within ±10%. The precision in this altitude region is estimated at values between 5 and 10% which gives an accuracy of 15 to 20%. Below 18 km, the spread of the percentage mean differences is larger and the precision degrades to values of more than 20% depending on altitude and latitude. The main reason for the degraded precision at low altitudes is attributed to undetected thin clouds which affect MIPAS retrievals, and to the influence of uncertainties in the water vapor concentration."
"16550871500;57197334483;7201361035;","Long-time global radiation for Central Europe derived from ISCCP Dx data",2007,"10.5194/acp-7-5021-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34848889543&doi=10.5194%2facp-7-5021-2007&partnerID=40&md5=49b7afbeb5c5f8e9ba64393022ebad9f","The global Dx dataset of the International Satellite Cloud Climatology Project (ISCCP) with a spatial resolution of about 30×30km2 was analysed to produce spatially highly resolved long-time datasets to describe the radiation budget for Central Europe over the period of 1984-2000. The computation of shortwave and longwave radiant flux densities at top of atmosphere and at surface was based on ID radiative transfer simulations. The simulations were carried out for all relevant atmospheric and surface conditions and the results were inserted into a look-up table. Thus, longtime calculations for all conditions and time slices of the Dx dataset could be realised. The study is focussed on the global radiation at surface. The first examination was carried out for the ISCCP Dl and the ISCCP D2 dataset. These datasets, including cloud and surface information on a different spatial scale (280×280 km2), were applied to the produced look-up table analogue to the Dx data. The calculated global radiation of the Dl and D2 dataset were compared to the Dx dataset. The differences between these datasets mainly range from 5-15 Wm-2 (2-6%) with regional peaks up to 25 Wm-2 (10%). The evaluation with the GEWEX Surface Radiation Budget (SRB) data emphasises differences between 5-25 Wm-2 (6-16%) over land areas. Deviations to an ISCCP provided flux data set vary from 0 Wm-2 in the North up to 35 Wm-2 (0-13%) in the South of Central Europe. The global radiation datasets provided by the Global Energy Balance Archive (GEBA) and the German Meteorological Service (DWD) agree well, but they are 5-25 Wm-2 (7-10%) lower than the Dx results. Annual analyses of global radiation of various regional climate models complete the study. It is figured out that the used models and methods reveal a couple of discrepancies. Especially in wintertime the results of our analysis differ to the considered models. Principally the uncertainties were caused by the determined range of values and simplifications for the computation of the radiative transfer simulation."
"6603958663;16445242100;","A revised linear ozone photochemistry parameterization for use in transport and general circulation models: Multi-annual simulations",2007,"10.5194/acp-7-2183-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247885880&doi=10.5194%2facp-7-2183-2007&partnerID=40&md5=95faf4f4168f67fb207063ad2c9e5e43","This article describes the validation of a linear parameterization of the ozone photochemistry for use in upper tropospheric and stratospheric studies. The present work extends a previously developed scheme by improving the 2-D model used to derive the coefficients of the parameterization. The chemical reaction rates are updated from a compilation that includes recent laboratory work. Furthermore, the polar ozone destruction due to heterogeneous reactions at the surface of the polar stratospheric clouds is taken into account as a function of the stratospheric temperature and the total chlorine content. Two versions of the parameterization are tested. The first one only requires the solution of a continuity equation for the time evolution of the ozone mixing ratio, the second one uses one additional equation for a cold tracer. The parameterization has been introduced into the chemical transport model MOCAGE. The model is integrated with wind and temperature fields from the ECMWF operational analyses over the period 2000-2004. Overall, the results from the two versions show a very good agreement between the modelled ozone distribution and the Total Ozone Mapping Spectrometer (TOMS) satellite data and the ""in-situ"" vertical soundings. During the course of the integration the model does not show any drift and the biases are generally small, of the order of 10%. The model also reproduces fairly well the polar ozone variability, notably the formation of ""ozone holes"" in the Southern Hemisphere with amplitudes and a seasonal evolution that follow the dynamics and time evolution of the polar vortex. The introduction of the cold tracer further improves the model simulation by allowing additional ozone destruction inside air masses exported from the high to the mid-latitudes, and by maintaining low ozone content inside the polar vortex of the Southern Hemisphere over longer periods in spring time. It is concluded that for the study of climate scenarios or the assimilation of ozone data, the present parameterization gives a valuable alternative to the introduction of detailed and computationally costly chemical schemes into general circulation models."
"12768921300;24450713200;6603125064;15071494600;7006941619;","Long-term variations in the correlation between NAO and solar activity: The importance of north-south solar activity asymmetry for atmospheric circulation",2007,"10.1016/j.asr.2007.02.091","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548789043&doi=10.1016%2fj.asr.2007.02.091&partnerID=40&md5=5ce3edbf5c9c27e1e849ce296572d3eb","General atmospheric circulation is the system of atmospheric motions over the Earth on the scale of the whole globe. Two main types of circulation have been identified: zonal - characterized by low amplitude waves in the troposphere moving quickly from west to east, and meridional with stationary high amplitude waves when the meridional transfer is intensified. The prevailing type of circulation is related to global climate. Based on many years of observations, certain ""circulation epochs"" have been defined when the same type of circulation prevails for years or decades. Here we study the relation between long-term changes in solar activity and prevailing type of atmospheric circulation, using NAO index reconstructed for the last four centuries as a proxy for large-scale atmospheric circulation. We find that when the southern solar hemisphere is more active, increasing solar activity in the secular solar cycle results in increasing zonality of the circulation, while when the northern solar hemisphere is more active, increasing solar activity increases meridional circulation. In an attempt to explain the observations, we compare the short-term reaction of NAO and NAM indices to different solar drivers: powerful solar flares, high speed solar wind streams, and magnetic clouds. © 2007 COSPAR."
"35247589400;35609878300;8454193200;15319743700;7003461830;","Comparison of CPTEC GCM and Eta Model results with observational data from the Rondonia LBA reference site, Brazil",2007,"10.2151/jmsj.85A.25","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248632509&doi=10.2151%2fjmsj.85A.25&partnerID=40&md5=fdbf6b47b7127482cd8dd1e0c9fea7ac","We compared forecasts of the Center for Weather Prediction and Climate Studies (Centro de Previsão de Tempo e Estudos Climáticos - CPTEC) General Circulation Model (GCM) and the mesoscale Eta Model with observations undertaken at the Rondonia Coordinated Enhanced Observing Period (CEOP) reference site, Brazil, for the dry period between 1 July and 1 September 2001. The Rondonia site is located in the Jaru Biological Reserve Area in the state of Rondonia within the Amazon region. The site is forested and is one of the Reference Sites of the Large-Scale Biosphere-Atmosphere Experiment in the Amazon Basin (LBA) Continental-Scale Experiment (CSE). Time series and mean diurnal cycles of precipitation, near-surface temperature, latent and sensible heat fluxes, surface incoming shortwave and net radiation fluxes are shown for 24-h and 48-h forecasts. In the global model, the predicted incoming shortwave radiation and net radiation are similar to observed values; however, this is accompanied by large overestimate of deep clouds and precipitation. Partition of the available energy results in an over-estimate of the sensible heat fluxes and an underestimate of the latent heat fluxes. The latent heat fluxes are large shortly after rain, but decay quickly. No clear improvement is noted in the 48-h forecasts compared with the 24-h forecasts. The Eta Model is a grid-point limited-area model. Its precipitation forecasts are similar to observations; however, the model overestimates the incoming shortwave radiation, resulting in excessive net radiation. The Eta sensible and latent heat fluxes are both overestimated, and 48-h forecasts produce small improvements over the 24-h forecasts. Near-surface temperatures are overestimated by both models. The global model requires a reduction in precipitation production, and both models require a reduction in incoming short-wave radiation at the surface. © 2007, Meteorological Society of Japan."
"57203793097;7005135473;","Statistical variability of top of atmosphere cloud-free shortwave aerosol radiative effect",2007,"10.5194/acp-7-2937-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250164666&doi=10.5194%2facp-7-2937-2007&partnerID=40&md5=99b582fed9cc6368566e3ea4e642118d","The statistical variability of globally averaged MODIS aerosol optical thickness at 0.55 μm (AOT) and top of atmosphere CERES cloud-free shortwave radiative effect (SWRE) is presented. Statistical variability is defined as the robustness of globally averaged statistics relative to data distribution. At the CERES footprint level, which we label ""raw data"", both the AOT and SWRE data derived from clear-sky CERES-SSF products show significant deviations from a normal distribution as evidenced by high skewness values. The spatial and temporal distribution of the data is also not uniform, with a greater concentration of data occurring in aerosol heavy-regions. As a result, globally averaged AOT and SWRE are overestimated when derived from raw data alone. To compensate, raw data are gridded into 2×2 degree grid-cells (called ""gridded"" data) to reduce the effect of spatial non-uniformity. However, the underlying non-normal distribution remains and manifests itself by increasing the uncertainty of grid-cell values. Globally averaged AOT and SWRE derived from a gridded dataset are substantially lower than those derived from raw data alone. The range of globally averaged AOT and SWRE values suggests that up to a 50% statistical variability exists, much of which is directly tied to how the data are manipulated prior to averaging. This variability increases when analyzing aerosol components (e.g. anthropogenic) since component AOT (and SWRE) may not exist at all locations were AOT is present. As a result, regions where a particular component AOT does not exist must either not be included in the global average or have data within these regions set to null values. However, each method produces significantly different results. The results of this work indicate simple mean and standard deviation statistics do not adequately describe global aerosol climate forcing data sets like the one used here. We demonstrate that placing raw observations on to a uniform grid is a necessary step before calculating global statistics. However, this by no means eliminates uncertainty in globally averaged AOT and SWRE values, while adding its own set of assumptions. When reporting any globally averaged statistic, it is important to report corresponding distribution and coverage information, in the form of skewness values, probability density functions, and spatial distribution plots, to help quantify its usefulness and robustness."
"7402933297;7409322518;56224155200;","Characteristics of diurnal and seasonal cycles in global monsoon systems",2007,"10.2151/jmsj.85A.403","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248682391&doi=10.2151%2fjmsj.85A.403&partnerID=40&md5=437fcc0873aada84eb394c327f99ce02","In this paper, we characterize the climatological diurnal cycles over monsoon land and ocean regions, and seasonal cycles for six major monsoon systems around the world, from observations and outputs of the NASA Seasonal-to-Interannual Prediction Project (NSIPP) general circulation model outputs. Over monsoon land regions, the diurnal cycle has a pronounced late afternoon peak in rainfall and over the oceans a much weak diurnal signal with an early morning peak. The NSIPP model produces a daily peak in rainfall about 2-3 hours earlier than observed, possibly attributed to a cumulus parameterization which does not include cloud life cycle effects, and which lack detailed treatment of boundary layer processes. The seasonal cycles of all monsoon rain systems are controlled by an ITCZ and a subtropical and/or extratropical component due to the presence of contiguous large continental land mass. Strong climatological intraseasonal oscillations (CISO) are found in the monsoon systems of South Asia and East Asia, Australia, and South America, and to a lesser degree for West Africa and Mexico/North America. The NSIPP model captures the slow component seasonal component reasonably well, but the CISO's are not well simulated. Analysis with reference to a new monsoon index shows that the major monsoon systems can be classified into three major groups (M1-3) according to the relative strength of continental vs. oceanic controls. East Asian and South Asian monsoons belong to a group (M1), where the continental influence is stronger than that from the ITCZ. The North America and South America monsoons show similar characteristics with the ITCZ influence slight stronger than continental influence (M2). The West Africa and Australia monsoons are found to be essentially ITCZ-monsoon systems (M3), with strong oceanic control, and limited poleward excursion of the monsoon rainbelt. We also find a clear trend associated with an increase in continentality for M3 monsoons, i.e., the West African and the Australian monsoons in the last two decades. We speculate that the former is linked to the partially recovery of the Sahel drought since the 1980's. © 2007, Meteorological Society of Japan."
"57206240288;6701497419;6507649684;57213597809;7006762240;","Estimating net primary production for Scandinavian forests using data from Terra/MODIS",2007,"10.1016/j.asr.2006.02.031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847313247&doi=10.1016%2fj.asr.2006.02.031&partnerID=40&md5=b2c0d06a4cedd8cf14f0dc34d88f6273","A model for estimating net primary production (NPP) across Scandinavia has benn developed. The model is based on the light-use efficiency (LUE) concept, where NPP is calculated as a product of the amount of absorbed photosynthetically active radiation (APAR) and a LUE-factor (ε) controlling the efficiency by which vegetation transforms photosynthetically active radiation (PAR) into biomass. The fractional APAR (FAPAR) is obtained by a linear transformation of 250 m normalized difference vegetation index (NDVI) data from the Moderate Resolution Imaging Spectroradiometer (MODIS). Prior to the transformation, the NDVI time series were seasonally adjusted by fitting local asymmetric Gaussian curves to the data thereby minimizing cloud contamination and other noise factors such as BRDF-related variation. The APAR is then calculated as a product of FAPAR and incident PAR, where the latter is obtained from the ""Swedish Regional Climate Modelling Programme"" (SWECLIM). The LUE-factor is modeled as a daily function of temperature, latitude, and day of the year (DOY). The FAPAR dataset was validated against measurements of fractional intercepted PAR (FIPAR) that were carried out at Norunda experimental site in central Sweden (60°5′N, 17°29′E) between August and October, 2001. The calculated FAPAR time series are in good agreement with the measurements. The modeled NPP is evaluated against flux measurements carried out in Norunda 1997-1999. The determination coefficients obtained when comparing modeled with measured data are R 2 = 0.82 for 2000 (RMSE = 2.71 g C m -2 d -1 ), and R 2 = 0.68 for 2001 (RMSE = 3.57 g C m -2 d -1 ) (time series averaged every 10th day). © 2007."
"7005706662;7103271625;","The frequency of extreme rain events in satellite rain-rate estimates and an atmospheric general circulation model",2007,"10.1175/JCLI3987.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846429979&doi=10.1175%2fJCLI3987.1&partnerID=40&md5=ee5a5716fd5506837b083a6ad5259c8e","The frequency distributions of surface rain rate are evaluated in the Tropical Rainfall Measuring Mission (TRMM) and Special Sensor Microwave/ Imager (SSM/I) satellite observations and the NOAA/GFDL global atmosphere model version 2 (AM2). Instantaneous satellite rain-rate observations averaged over the 2.5° latitude × 2° longitude model grid are shown to be representative of the half-hour rain rate from single time steps simulated by the model. Rain-rate events exceeding 10 mm, h-1 are observed by satellites in most regions, with 1 mm h-1 events occurring more than two orders of magnitude more frequently than 10 mm h-1 events. A model simulation using the relaxed Arakawa-Schubert (RAS) formulation of cumulus convection exhibits a strong bias toward many more light rain events compared to the observations and far too few heavy rain events. A simulation using an alternative convection scheme, which includes an explicit representation of mesoscale circulations and an alternative formulation of the closure, exhibits, among other differences, an order of magnitude more tropical rain events above the 5 mm h-1 rate compared to the RAS simulation. This simulation demonstrates that global atmospheric models can be made to produce heavy rain events, in some cases even exceeding the observed frequency of such events. Additional simulations reveal that the frequency distribution of the surface rain rate in the GCM is shaped by a variety of components within the convection parameterization, including the closure, convective triggers, the spectrum of convective and mesoscale clouds, and other parameters whose physical basis is currently only understood to a limited extent. Furthermore, these components interact nonlinearly such that the sensitivity of the rain-rate distribution to the formulation of one component may depend on the formulation of the others. Two simulations using different convection parameterizations are performed using perturbed sea surface temperatures as a surrogate for greenhouse gas-forced climate warming. Changes in the frequency of rain events greater than 2 mm h-1 associated with changing the convection scheme in the model are greater than the changes in the frequency of heavy rain events associated with a 2-K warming using either model. Thus, uncertainty persists with respect to simulating intensity distributions for precipitation and projecting their future changes. Improving the representation of the frequency distribution of rain rates will rely on refinements in the formulation of cumulus closure and the other components of convection schemes, and greater certainty in predictions of future changes in both total rainfall and in rain-rate distributions will require additional refinements in those parameterizations that determine the cloud and water vapor feedbacks. © 2007 American Meteorological Society."
"16443826700;18037007500;6507896695;16445227700;8716128000;6602699151;6603848988;6603425325;","Global distributions of water vapour isotopologues retrieved from IMG/ADEOS data",2007,"10.5194/acp-7-3957-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547469427&doi=10.5194%2facp-7-3957-2007&partnerID=40&md5=d83a24316e347028f0a352f5eb93b138","The isotopologic composition of water vapour in the atmosphere provides valuable information on many climate, chemical and dynamical processes. The accurate measurements of the water isotopologues by remote-sensing techniques remains a challenge, due to the large spatial and temporal variations. Simultaneous profile retrievals of the main water isotopologues (i.e. H 216O, H218O and HDO) and their ratios are presented here for the first time, along their retrieved global distributions. The results are obtained by exploiting the high resolution infrared spectra recorded by the Interferometric Monitor for Greenhouse gases (IMG) instrument, which has operated in the nadir geometry onboard the ADEOS satellite between 1996 and 1997. The retrievals are performed on cloud-free radiances, measured during ten days of April 1997, considering two atmospheric windows (1205-1228 cm-1; 2004-2032 cm-1) and using a line-by-line radiative transfer model and an inversion procedure based on the Optimal Estimation Method (OEM). Characterizations in terms of vertical sensitivity and error budget are provided. We show that a relatively high vertical resolution is achieved for H216O (∼4-5 km), and that the retrieved profiles are in fair agreement with local sonde measurements, at different latitudes. The retrieved global distributions of H216O, H218O, HDO and their ratios are presented and found to be consistent with previous experimental studies and models. The Ocean-Continent difference, the latitudinal and vertical dependence of the water vapour amount and the isotopologic depletion are notably well reproduced. Others trends, possibly related to small-scale variations in the vertical profiles are also discussed. Despite the difficulties encountered for computing accurately the isotopologic ratios, our results demonstrate the ability of infrared nadir sounding for monitoring atmospheric isotopologic water vapour distributions on a global scale."
"8670213100;6507681572;15841350300;6602844274;7004101548;6603395511;6701796418;","Modelling the direct effect of aerosols in the solar near-infrared on a planetary scale",2007,"10.5194/acp-7-3211-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347344983&doi=10.5194%2facp-7-3211-2007&partnerID=40&md5=1427f1d679be94335512666443523b21","We used a spectral radiative transfer model to compute the direct radiative effect (DRE) of natural plus anthropogenic aerosols in the solar near-infrared (IR), between 0.85-10 μm, namely, their effect on the outgoing near1R radiation at the top of atmosphere (TOA, ΔFTOA), on the atmospheric absorption of near-IR radiation (ΔFatmab) and on the surface downward and absorbed near-IR radiation (ΔFsurf, and ΔFsurfnet, respectively). The computations were performed on a global scale (over land and ocean) under all-sky conditions, using detailed spectral aerosol optical properties taken from the Global Aerosol Data Set (GADS) supplemented by realistic data for the rest of surface and atmospheric parameters. The computed aerosol DRE, averaged over the 12-year period 1984-1995 for January and July, shows that on a global mean basis aerosols produce a planetary cooling by increasing the scattered near-IR radiation back to space by 0.48 W m-2, they warm the atmosphere by 0.37 W m-2 and cool the surface by decreasing the downward and absorbed near-IR radiation at surface by 1.03 and 0.85 W m-2, respectively. The magnitude of the near-IR aerosol DRE is smaller than that of the combined ultraviolet (UV) and visible DRE, but it is still energetically important, since it contributes to the total shortwave (SW) DRE by 22-31%. The aerosol-produced near-IR surface cooling combined with the atmospheric warming, may affect the thermal dynamics of the Earth-atmosphere system, by increasing the atmospheric stability, decreasing thus cloud formation, and precipitation, especially over desertification threatened regions such as the Mediterranean basin. This, together with the fact that the sign of near-IR aerosol DRE is sometimes opposite to that of U V-visible DRE, demonstrates the importance of performing detailed spectral computations to provide estimates of the climatic role of aerosols for the Earth-atmosphere system. This was demonstrated by sensitivity tests revealing very large differences (up to 300%) between aerosol DREs computed using detailed spectral and spectrally-averaged aerosol optical properties. Our model results indicate thus that the aerosol direct radiative effect on the near-IR radiation is very sensitive to the treatment of the spectral dependence of aerosol optical properties and solar radiation."
"56288754100;15821870100;56211898600;57210538699;7102807964;7102674341;9940368600;7102578937;","Measurements of O3, NO2 and BrO during the INDOEX campaign using ground based DOAS and GOME satellite data",2007,"10.5194/acp-7-283-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846345653&doi=10.5194%2facp-7-283-2007&partnerID=40&md5=6daca52b4184f8053180f37f9037c777","The INDian Ocean Experiment (INDOEX) was an international, multi-platform field campaign to measure long-range transport of air masses from South and South-East-(SE) Asia towards the Indian Ocean. During the dry monsoon season between January and March 1999, local measurements were carried out from ground based platforms and were compared with satellite based data. The objective of this study was to characterise stratospheric and tropospheric trace gas amounts in the equatorial region, and to investigate the impact of air pollution at this remote site. For the characterisation of the chemical composition of the outflow from the S-SE-Asian region, we performed ground based dual-axis-DOAS (Differential Optical Absorption Spectroscopy) measurements at the KCO (Kaashidhoo Climate Observatory) in the Maldives (5.0° N, 73.5° E). The measurements were conducted using two different observation modes (off-axis and zenith-sky). This technique allows the separation of the tropospheric and stratospheric columns for different trace gases like O3 and NO 2. These dual-axis DOAS data were compared with O3-sonde measurements performed at KCO and satellite based GOME (Global Ozone Measuring Experiment) data during the intensive measuring phase of the INDOEX campaign in February and March 1999. From GOME observations, tropospheric and stratospheric columns for O3 and NO2 were retrieved. In addition, the analysis of the O3-sonde measurements allowed the determination of the tropospheric O3 amount. The comparison shows that the results of all three measurement systems agree within their error limits. During the INDOEX campaign, mainly background conditions were observed, but in a single case an increase of tropospheric NO2 during a short pollution event was observed from the ground and the impact on the vertical columns was calculated. GOME measurements showed evidence for small tropospheric contributions to the BrO budget, probably located in the free troposphere and present over long periods of the year. The amounts of BrO have been investigated by the comparison of satellite pixels influenced by high and low cloud conditions based on GOME data which allows the determination of the detection limit of 3.8×10 13molecules cm-2 of tropospheric BrO columns."
"6602751071;7401837283;35798100800;9233163800;8088667200;55901843200;8881618800;8412336900;35448188800;8385562400;35372808200;6602624109;7403398543;6603758021;8388969200;8948450600;16480646000;57193752496;6603202832;55501442100;55972795200;7003951084;35902595700;6701815977;8412334900;8378887500;6701310825;6603917221;35433083100;6701774457;8677500600;7003961021;6701797047;9248919000;57206421971;56213441200;55398576600;7005233189;15752278200;8684038000;7007168548;56249308700;","Geophysical validation of MIPAS-ENVISAT operational ozone data",2007,"10.5194/acp-7-4807-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34748892912&doi=10.5194%2facp-7-4807-2007&partnerID=40&md5=33ae00d670f713dcb3398250a95376af","The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), on-board the European ENVIronmental SATellite (ENVISAT) launched on 1 March 2002, is a middle infrared Fourier Transform spectrometer measuring the atmospheric emission spectrum in limb sounding geometry. The instrument is capable to retrieve the vertical distribution of temperature and trace gases, aiming at the study of climate and atmospheric chemistry and dynamics, and at applications to data assimilation and weather forecasting. MIPAS operated in its standard observation mode for approximately two years, from July 2002 to March 2004, with scans performed at nominal spectral resolution of 0.025 cm -1 and covering the altitude range from the mesosphere to the upper troposphere with relatively high vertical resolution (about 3 km in the stratosphere). Only reduced spectral resolution measurements have been performed subsequently. MIPAS data were re-processed by ESA using updated versions of the Instrument Processing Facility (IPF v4.61 and v4.62) and provided a complete set of level-2 operational products (geolocated vertical profiles of temperature and volume mixing ratio of H2O, O3, HNO3, CH4, N2O and NO2) with quasi continuous and global coverage in the period of MIPAS full spectral resolution mission. In this paper, we report a detailed description of the validation of MIPAS-ENVISAT operational ozone data, that was based on the comparison between MIPAS v4.61 (and, to a lesser extent, v4.62) O3 VMR profiles and a comprehensive set of correlative data, including observations from ozone sondes, ground-based lidar, FTIR and microwave radiometers, remote-sensing and in situ instruments on-board stratospheric aircraft and balloons, concurrent satellite sensors and ozone fields assimilated by the European Center for Medium-range Weather Forecasting. A coordinated effort was carried out, using common criteria for the selection of individual validation data sets, and similar methods for the comparisons. This enabled merging the individual results from a variety of independent reference measurements of proven quality (i.e. well characterized error budget) into an overall evaluation of MIPAS O3 data quality, having both statistical strength and the widest spatial and temporal coverage. Collocated measurements from ozone sondes and ground-based lidar and microwave radiometers of the Network for the Detection Atmospheric Composition Change (NDACC) were selected to carry out comparisons with time series of MIPAS O 3 partial columns and to identify groups of stations and time periods with a uniform pattern of ozone differences, that were subsequently used for a vertically resolved statistical analysis. The results of the comparison are classified according to synoptic and regional systems and to altitude intervals, showing a generally good agreement within the comparison error bars in the upper and middle stratosphere. Significant differences emerge in the lower stratosphere and are only partly explained by the larger contributions of horizontal and vertical smoothing differences and of collocation errors to the total uncertainty. Further results obtained from a purely statistical analysis of the same data set from NDACC ground-based lidar stations, as well as from additional ozone soundings at middle latitudes and from NDACC ground-based FTIR measurements, confirm the validity of MIPAS O3 profiles down to the lower stratosphere, with evidence of larger discrepancies at the lowest altitudes. The validation against O3 VMR profiles using collocated observations performed by other satellite sensors (SAGE II, POAM III, ODIN-SMR, ACE-FTS, HALOE, GOME) and ECMWF assimilated ozone fields leads to consistent results, that are to a great extent compatible with those obtained from the comparison with ground-based measurements. Excellent agreement in the full vertical range of the comparison is shown with respect to collocated ozone data from stratospheric aircraft and balloon instruments, that was mostly obtained in very good spatial and temporal coincidence with MIPAS scans. This might suggest that the larger differences observed in the upper troposphere and lowermost stratosphere with respect to collocated ground-based and satellite O3 data are only partly due to a degradation of MIPAS data quality. They should be rather largely ascribed to the natural variability of these altitude regions and to other components of the comparison errors. By combining the results of this large number of validation data sets we derived a general assessment of MIPAS v4.61 and v4.62 ozone data quality. A clear indication of the validity of MIPAS O3 vertical profiles is obtained for most of the stratosphere, where the mean relative difference with the individual correlative data sets is always lower than ±10%. Furthermore, these differences always fall within the combined systematic error (from 1 hPa to 5OhPa) and the standard deviation is fully consistent with the random error of the comparison (from 1 hPa to ∼~30-40hPa). A degradation in the quality of the agreement is generally observed in the lower stratosphere and upper troposphere, with biases up to 25% at 100 hPa and standard deviation of the global mean differences up to three times larger than the combined random error in the range 50-100 hPa. The larger differences observed at the bottom end of MIPAS retrieved profiles can be associated, as already noticed, to the effects of stronger atmospheric gradients in the UTLS that are perceived differently by the various measurement techniques. However, further components that may degrade the results of the comparison at lower altitudes can be identified as potentially including cloud contamination, which is likely not to have been fully filtered using the current settings of the MIPAS cloud detection algorithm, and in the linear approximation of the forward model that was used for the a priori estimate of systematic error components. The latter, when affecting systematic contributions with a random variability over the spatial and temporal scales of global averages, might result in an underestimation of the random error of the comparison and add up to other error sources, such as the possible underestimates of the p and T error propagation based on the assumption of a 1K and 2% uncertainties, respectively, on MIPAS temperature and pressure retrievals. At pressure lower than 1 hPa, only a small fraction of the selected validation data set provides correlative ozone data of adequate quality and it is difficult to derive quantitative conclusions about the performance of MIPAS O2 retrieval for the topmost layers."
"8586682800;6603385031;7005968859;7004715270;8640231600;8585525800;7005451928;","Chemical aging and the hydrophobic-to-hydrophilic conversion of carbonaceous aerosol",2006,"10.1029/2006GL027249","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247383105&doi=10.1029%2f2006GL027249&partnerID=40&md5=c81f4e8d9e862af7a440ce07409e6fe8","Laboratory experiments simulating chemical aging of carbonaceous aerosol by atmospheric oxidants demonstrate that oxidative processing increases their ability to activate as cloud droplets. A microphysical model shows, however, that the measured increase in hygroscopicity is insufficient to lead to efficient wet scavenging for sub-100 nm particles that are typically emitted from combustion sources. The absence of an efficient atmospheric oxidation pathway for hydrophobic-to-hydrophilic conversion suggests that the fate of carbonaceous aerosol is instead controlled by its interaction with more hydrophilic species such as sulfates, nitrates, and secondary organic aerosol, leading to longer lifetimes, higher burdens, and greater contributions to climate forcing in the free troposphere than are currently estimated. Copyright 2006 by the American Geophysical Union."
"35221059800;55640225400;7004533232;7006592026;","Convection suppression criteria applied to the MIT cumulus parameterization scheme for simulating the Asian summer monsoon",2006,"10.1029/2006GL028026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548039009&doi=10.1029%2f2006GL028026&partnerID=40&md5=53c127dd5f359f38d769ab795b576a2e","It is shown in this study that applying some convection suppression criteria to the MIT or Emanuel cumulus parameterization scheme may significantly improve the performance of a regional climate model to simulate the Asian summer monsoon precipitation, particularly the precipitation over southeastern China and the Mei-yu rainband over the East Asian region. With the original MIT cumulus scheme, the precipitation over the ocean particularly the South China Sea (SCS) region is generally over-estimated, which may result in the underestimation of precipitation over China. It is found that the relative vorticity criterion (which shuts down the convection when the low-level flow is anticyclonic and stronger than a certain threshold value) has the largest impact on suppressing the over-estimated precipitation over the SCS. Copyright 2006 by the American Geophysical Union."
"55707280000;","A possible cause of a regional climate model's failure in simulating the east Asian summer monsoon",2006,"10.1029/2006GL027654","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548009574&doi=10.1029%2f2006GL027654&partnerID=40&md5=d917bb62c5eae5b9327b88355a385487","The Regional Climate Model RegCM3 has been integrated to simulate the east Asian summer monsoon in 1994 with three cumulus parameterization schemes (CPSs), respectively. Comparisons between simulations and observations suggest that the model can reproduce the regional circulation systems basically with all three individual CPSs. However, it is not so well when tropical cyclones (TCs) are active over the Western Pacific Ocean (WTO). The model exhibits a common feature when TCs are over WTO in model domain, which gives an anticyclonic circulation difference over WPO, and two cyclonic circulation differences centered over eastern China/Yellow Sea and Japan/WPO to the east of Jdpan, depending on the adopted CPS. With a smaller model domain, the model can give a more reasonable result over east Asia forced by reanalysis data. We argue that the unsuccessful simulations in summertime over east Asia are partly caused by the models failure to capture the featutes of TCs over WPO. Copyright 2006 by the American Geophysical Union."
"56283402900;7006993412;6505767272;36829694300;7402548443;7004402705;57192975368;7003930724;8309515600;8447628500;35371325600;6701801931;6603760503;55697341500;6603695169;6603352099;7005900836;8842994000;7003824291;6602624109;7003421954;55272324200;7004005128;8309518900;57198586226;55902740300;15832736400;8434651900;6506098013;6603105196;8309520600;7003765782;7005829052;","Arctic winter 2005: Implications for stratospheric ozone loss and climate change",2006,"10.1029/2006GL026731","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845610873&doi=10.1029%2f2006GL026731&partnerID=40&md5=41fd0e6562044f039c75bd3e3734366d","The Arctic polar vortex exhibited widespread regions of low temperatures during the winter of 2005, resulting in significant ozone depletion by chlorine and bromine species. We show that chemical loss of column ozone (ΔO3) and the volume of Arctic vortex air cold enough to support the existence of polar stratospheric clouds (VPSC) both exceed levels found for any other Arctic winter during the past 40 years. Cold conditions and ozone loss in the lowermost Arctic stratosphere (e.g., between potential temperatures of 360 to 400 K) were particularly unusual compared to previous years. Measurements indicate ΔO3 = 121 ± 20 DU and that ΔO3 versus VPSC lies along an extension of the compact, near linear relation observed for previous Arctic winters. The maximum value of VPSC during five to ten year intervals exhibits a steady, monotonic increase over the past four decades, indicating that the coldest Arctic winters have become significantly colder, and hence are more conducive to ozone depletion by anthropogenic halogens. Copyright 2006 by the American Geophysical Union."
"35779178900;7004364155;23476370700;35849753400;7406061582;","Comparison of MISR and CERES top-of-atmosphere albedo",2006,"10.1029/2006GL027958","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548613592&doi=10.1029%2f2006GL027958&partnerID=40&md5=7707cf1534b4f098339b4a68c7208e61","The Clouds and the Earth's Radiant Energy System (CERES) and the Multi-angle Imaging SpectroRadiometer (MISR) on Terra satellite measure the Earth's top-of-atmosphere (TOA) albedo in broadband and narrowband, respectively. This study presents the first direct comparison of the CERES and MISR albedos. An algorithm for converting the MISR spectral albedos to broadband is derived. The MISR and CERES albedos for overcast ocean scenes are compared between 75°S-75°N for solar zenith angles ≤75°. For overcast 1° × 1° ocean regions, the relative differences and the relative root-mean-square (RMS) differences between the MISR and CERES albedos are ∼0.8% and ∼4.3%, respectively. Accounting for a ∼2.0% error in the MISR albedos due to narrow-to-broadband albedo conversion errors, the RMS difference between the MISR and CERES albedos due to angular distribution model (ADM) differences is estimated to be ∼3.8%. The remarkable consistency between the CERES and MISR albedos for overcast oceans suggests that both instrument teams have derived accurate corrections for the radiance anisotropy of cloud scenes. This consistency will strongly enhance the confidence in the temporal trends of cloud albedo measured by the CERES and have significant impact on climate studies. Copyright 2006 by the American Geophysical Union."
"24722339600;7004479957;","On the relationship between stratiform low cloud cover and lower-tropospheric stability",2006,"10.1175/JCLI3988.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748332650&doi=10.1175%2fJCLI3988.1&partnerID=40&md5=c303f9bbca9666d1801c51d4ad62d9fa","Observations in subtropical regions show that stratiform low cloud cover is well correlated with the lower-troposphere stability (LTS), defined as the difference in potential temperature θ between the 700-hPa level and the surface. The LTS can be regarded as a measure of the strength of the inversion that caps the planetary boundary layer (PBL). A stronger inversion is more effective at trapping moisture within the marine boundary layer (MBL), permitting greater cloud cover. This paper presents a new formulation, called the estimated inversion strength (EIS), to estimate the strength of the PBL inversion given the temperatures at 700 hPa and at the surface. The EIS accounts for the general observation that the free-tropospheric temperature profile is often close to a moist adiabat and its lapse rate is strongly temperature dependent. Therefore, for a given LTS, the EIS is greater at colder temperatures. It is demonstrated that while the seasonal cycles of LTS and low cloud cover fraction (CF) are strongly correlated in many regions, no single relationship between LTS and CF can be found that encompasses the wide range of temperatures occurring in the Tropics, subtropics, and midlatitudes. However, a single linear relationship between CF and EIS explains 83% of the regional/seasonal variance in stratus cloud amount, suggesting that EIS is a more regime-independent predictor of stratus cloud amount than is LTS under a wide range of climatological conditions. The result has some potentially important implications for how low clouds might behave in a changed climate. In contrast to Miller's thermostat hypothesis that a reduction in the lapse rate (Clausius-Clapeyron) will lead to increased LTS and increased tropical low cloud cover in a warmer climate, the results here suggest that low clouds may be much less sensitive to changes in the temperature profile if the vertical profile of tropospheric warming follows a moist adiabat. © 2006 American Meteorological Society."
"7410070663;6603561402;15763329000;7005453346;6603613067;7003365490;","Ocean surface albedo and its impact on radiation balance in climate models",2006,"10.1175/JCLI3973.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846134697&doi=10.1175%2fJCLI3973.1&partnerID=40&md5=b512a1b2475b377f4c21cf81aa63e864","An analysis of several ocean surface albedo (OSA) schemes is undertaken through offline comparisons and through application in the Canadian Centre for Climate Modelling and Analysis (CCCma) fourth-generation atmospheric general circulation model (AGCM4). In general, each scheme requires different input quantities to determine the OSA. Common to all schemes is a dependence on the solar zenith angle (SZA). A direct comparison of the SZA dependence of the schemes reveals significant differences in the predicted albedos. Other input quantities include wind speed and aerosol/cloud optical depth, which are also analyzed. An offline one-dimensional radiative transfer model is used to quantitatively study the impact of ocean surface albedo on the radiative transfer process. It is found that, as a function of SZA and wind speed, the difference in reflected solar flux at the top of the atmosphere is in general agreement between OSA schemes that depend on these quantities, with a difference &lt;10 W m-2. However, for simpler schemes that depend only on SZA the difference in this flux can approach 10-20 W m-2. The impact of the different OSA schemes is assessed through multiyear simulations of present-day climate in AGCM4. Five-year means of the reflected clear-sky flux at the top of the atmosphere reveal local differences of up to several watts per meters squared between any of the schemes. Globally, all schemes display a similar negative bias relative to the Earth Radiation Budget Experiment (ERBE) observations. This negative bias is largely reduced by comparison with the recently released Clouds and the Earth's Radiant Energy System (CERES) data. It is shown that the local upward clear-sky flux at the surface is more sensitive to the OSA formulation than the clear-sky upward flux at the top of atmosphere. It is found that the global energy balance of the model at the top of the atmosphere and at the surface is surprisingly insensitive to which OSA scheme is employed. © 2006 American Meteorological Society."
"56014511300;35611825600;35550043200;","A distribution law for free-tropospheric relative humidity",2006,"10.1175/JCLI3978.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846184099&doi=10.1175%2fJCLI3978.1&partnerID=40&md5=78f5b933495f353890a2d697401327f2","The probability distribution of local relatix e humidity R in the free troposphere is explored by comparing a simple theoretical calculation with observations from the global positioning system (GPS) and the Microwave Limb Sounder (MLS). The calculation is based on a parcel of air that conserves its composition during diabatic subsidence, until it is resaturated by randomly entering a convective system. This simple ""advection-condensation"" model of relative humidity predicts a probability density for R proportional to where Rr-1, where r is the ratio of time scales associated with subsidence drying and random moistening. The observations obey this distribution remarkably well from 600 to 200 hPa in the Tropics and midlatitudes: possible reasons for this are discussed. The lowest values of R are predicted, and observed, to be the most probable. The observed vertical variation of R is well explained by that of the subsidence time scale, which is set by large-scale dynamics and radiation. These results imply that cloud microphysics exerts little control on water vapor's greenhouse effect, but that relativelv subtle dvnamical changes have the potential to alter the strength of its feedback on climate change. © 2006 American Meteorological Society."
"35598959400;7101975283;16642852700;6603406415;","A comparison of sea surface temperatures from microwave remote sensing of the Labrador Sea with in situ measurements and model simulations",2006,"10.1029/2006JC003578","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249099503&doi=10.1029%2f2006JC003578&partnerID=40&md5=2684b7350a300ecff32607b8e205b36a","As one of the few places in the ocean where winter cooling and mixing creates conditions where water from the surface can penetrate into the deep ocean the Labrador Sea is an area of interest to people studying climate change in the ocean. Persistent cloud cover over this area makes it impossible to use infrared satellite imagery to relate space/time changes in sea surface temperature (SST) to changes in surface currents and air-sea interaction. Using passive microwave SSTs from the Advanced Microwave Scanning Radiometer (AMSR-E), we plot space/time changes in SST in the Labrador Sea and relate these changes to both simultaneous in situ measurements of temperature and numerical model SSTs. A direct comparison between the microwave SSTs, infrared SSTs, and in situ temperatures measured from profiling floats reveals that the microwave SSTs are a good representation of space/time changes in infrared SST and in ocean temperatures down to 10 m below the sea surface. Comparisons between the microwave SSTs and time series of temperatures at depths below 50 m reveal that winter/spring surface cooling makes the SST similar to temperatures at these deeper depths in the convection region of the central Labrador Sea. Detailed comparison of the annual cycle between the microwave SSTs and the model SST and 10 m currents reveals overall good agreement and some interesting differences. Copyright 2006 by the American Geophysical Union."
"16427682500;7004683817;","On possible drivers of Sun-induced climate changes",2006,"10.1016/j.jastp.2006.05.019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751179461&doi=10.1016%2fj.jastp.2006.05.019&partnerID=40&md5=3baca5d34b3240f8eaa85a2b025b2129","We tested the validity of two current hypotheses on the dependence of climate change on solar activity. One of them states that variations in the tropospheric temperature are caused directly by changes of the solar radiance (total or spectral). The other suggests that cosmic ray (CR) fluctuations, caused by the solar/heliospheric modulation, affect the climate via cloud formation. Confronting these hypotheses with seven different sets of the global/hemispheric temperature reconstructions for the last 400 years, we found that the former mechanism is in general more prominent than the latter. Therefore, we can conclude that in so far as the Sun-climate connection is concerned tropospheric temperatures are more likely affected by variations in the UV radiation flux rather than by those in the CR flux. © 2006 Elsevier Ltd. All rights reserved."
"7202703351;57213167498;","A perspective on the effect of climate and local environmental variables on the performance of attic radiant barriers in the United States",2006,"10.1016/j.buildenv.2005.07.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746005937&doi=10.1016%2fj.buildenv.2005.07.018&partnerID=40&md5=84dc0bee7e402d1b8ea0831a02f3c82c","This paper offers a perspective on how climate and local environmental variables affect the performance of attic radiant barriers across the United States. Transient heat and mass transfer simulations were performed on a vented triangular attic with insulation level of 3.5 m2 K / W (R-19) and the results were based on integrated hourly ceiling heat fluxes over 3-month periods during the cooling season. The ceiling heat transfer percent reductions ranged from 36.8% in the Tropical Savanna climate to 2.3% in the Mediterranean climate. Peak-hour percent reductions in ceiling heat flux ranged from almost 100% in the Marine West Coast climate to 23% in the Desert climate. The results suggested that local ambient air temperature, humidity, cloud cover index, and altitude had first-order effects. The amount of local solar radiation had no effect on the performance of the systems. © 2005 Elsevier Ltd. All rights reserved."
"35547807400;57210518852;","Climate forcings and climate sensitivities diagnosed from coupled climate model integration",2006,"10.1175/JCLI3974.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845387289&doi=10.1175%2fJCLI3974.1&partnerID=40&md5=cc7b4a51d8da78613d5185d595de35a8","A simple technique is proposed for calculating global mean climate forcing from transient integrations of coupled atmosphere-ocean general circulation models (AOGCMs). This ""climate forcing"" differs from the conventionally defined radiative forcing as it includes semidirect effects that account for certain short time scale responses in the troposphere. First, a climate feedback term is calculated from reported values of 2 × CO2 radiative forcing and surface temperature time series from 70-yr simulations by 20 AOGCMs. In these simulations carbon dioxide is increased by 1% yr-1. The derived climate feedback agrees well with values that are diagnosed from equilibrium climate change experiments of slab-ocean versions of the same models. These climate feedback terms are associated with the fast, quasi-linear response of lapse rate, clouds, water vapor, and albedo to global surface temperature changes. The importance of the feedbacks is gauged by their impact on the radiative fluxes at the top of the atmosphere. Partial compensation is found between longwave and shortwave feedback terms that lessens the intermodel differences in the equilibrium climate sensitivity. There is also some indication that the AOGCMs overestimate the strength of the positive longwave feedback. These feedback terms are then used to infer the shortwave and longwave time series of climate forcing in twentieth- and twenty-first-century simulations in the AOGCMs. The technique is validated using conventionally calculated forcing time series from four AOGCMs. In these AOGCMs the shortwave and longwave climate forcings that are diagnosed agree with the conventional forcing time series within ∼10%. The shortwave forcing time series exhibit order of magnitude variations between the AOGCMs, differences likely related to how both natural forcings and/or anthropogenic aerosol effects are included. There are also factor of 2 differences in the longwave climate forcing time series, which may indicate problems with the modeling of well-mixed greenhouse gas changes. The simple diagnoses presented provides an important and useful first step for understanding differences in AOGCM integrations, indicating that some of the differences in model projections can be attributed to different prescribed climate forcing, even for so-called standard climate change scenarios. © 2006 American Meteorological Society."
"7402328256;6701465132;7005613103;7202888402;","Sulfate aerosols forcing: An estimate using a three-dimensional interactive chemistry scheme",2006,"10.1016/j.atmosenv.2006.07.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751011891&doi=10.1016%2fj.atmosenv.2006.07.010&partnerID=40&md5=28f754209a28b9029c11ab438112c44f","The tropospheric sulfate radiative forcing has been calculated using an interactive chemistry scheme in LMD-GCM. To estimate the radiative forcing of sulfate aerosol on climate, a consistent interaction between atmospheric circulation and radiation computation has been allowed in LMD-GCM. The model results indicate that the change in the sulfate aerosols number concentration is negatively correlated to the indirect radiative forcing. The model simulated annual mean direct radiative forcing ranges from -0.1 to -1.2 W m-2, and indirect forcing ranges from -0.4 to -1.6 W m-2. The global annual mean direct effect estimated by the model is -0.48 W m-2, and that of indirect is -0.68 W m-2. © 2006."
"6701735773;8937991200;35509639400;6603875926;6507671561;7004714030;6602886421;6507033325;6602135031;6602080773;56134359300;10143687400;24511929800;56186932200;","The LMDZ4 general circulation model: Climate performance and sensitivity to parametrized physics with emphasis on tropical convection",2006,"10.1007/s00382-006-0158-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748748862&doi=10.1007%2fs00382-006-0158-0&partnerID=40&md5=1a0f6d98f42bbc81747717e98b379302","The LMDZ4 general circulation model is the atmospheric component of the IPSL-CM4 coupled model which has been used to perform climate change simulations for the 4th IPCC assessment report. The main aspects of the model climatology (forced by observed sea surface temperature) are documented here, as well as the major improvements with respect to the previous versions, which mainly come form the parametrization of tropical convection. A methodology is proposed to help analyse the sensitivity of the tropical Hadley-Walker circulation to the parametrization of cumulus convection and clouds. The tropical circulation is characterized using scalar potentials associated with the horizontal wind and horizontal transport of geopotential (the Laplacian of which is proportional to the total vertical momentum in the atmospheric column). The effect of parametrized physics is analysed in a regime sorted framework using the vertical velocity at 500 hPa as a proxy for large scale vertical motion. Compared to Tiedtke's convection scheme, used in previous versions, the Emanuel's scheme improves the representation of the Hadley-Walker circulation, with a relatively stronger and deeper large scale vertical ascent over tropical continents, and suppresses the marked patterns of concentrated rainfall over oceans. Thanks to the regime sorted analyses, these differences are attributed to intrinsic differences in the vertical distribution of convective heating, and to the lack of self-inhibition by precipitating downdraughts in Tiedtke's parametrization. Both the convection and cloud schemes are shown to control the relative importance of large scale convection over land and ocean, an important point for the behaviour of the coupled model. © Springer-Verlag 2006."
"6701670597;14920137300;7501720647;7005035762;","The mesoscale convection life cycle: Building block or prototype for large-scale tropical waves?",2006,"10.1016/j.dynatmoce.2006.03.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749827492&doi=10.1016%2fj.dynatmoce.2006.03.003&partnerID=40&md5=fb4457299e1dadb22f0ddeadffc8737c","A cumulonimbus cloud may ascend and spawn its anvil cloud, precipitation, and downdrafts within an hour or so. This paper inquires why a similar progression of events (life cycle) is observed for tropical weather fluctuations with time scales of hours, days, and even weeks. Regressions using point data illustrate the characteristic unit of rain production: the mesoscale convective system (MCS), covering tens of kilometers and lasting several hours, with embedded convective rain cells. Meanwhile, averages over larger spatial areas indicate a self-similar progression from shallow to deep convection to stratiform anvils on many time scales. Synthetic data exercises indicate that simple superpositions of fixed-structure MCS life cycles (the Building Block hypothesis) cannot explain why longer period life cycles are similar. Rather, it appears that an MCS may be a small analogue or prototype of larger scale waves. Multiscale structure is hypothesized to occur via a Stretched Building Block conceptual model, in which the widths (durations) of zones of shallow, deep, and stratiform anvil clouds in MCSs are modulated by larger scale waves. Temperature (T) and humidity (q) data are examined and fed into an entraining plume model, in an attempt to elucidate their relative roles in these large-scale convection zone variations. T profile variations, with wavelengths shorter than troposphere depth, appear important for high-frequency (∼ 2-5-day period) convectively coupled waves, as density directly links convection (via buoyancy) and large-scale wave dynamics (via restoring force). Still, the associated q anomalies are several times greater than adiabatic, suggesting a strong amplification by shallow convective feedbacks. For lower frequency (intraseasonal) variability, q anomalies are considerably larger compared to T, and may be dominant. © 2006 Elsevier B.V. All rights reserved."
"56962915800;7102389805;24492188100;57211223914;7401900750;","Boreal summer quasi-monthly oscillation in the global tropics",2006,"10.1007/s00382-006-0163-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749668519&doi=10.1007%2fs00382-006-0163-3&partnerID=40&md5=02d0e993256c6e6a099ec4f83ca75ea5","The boreal summer intraseasonal oscillation (ISO) in the global tropics is documented here using a 7-year suite (1998-2004) of satellite measurements. A composite scenario was made of 28 selected events with reference to the oscillation in the eastern equatorial Indian Ocean (EIO), where the oscillation is most regular and its intensity is indicative of the strength of the subsequent northward propagation. The average oscillation period is about 32 days, and this quasi-monthly oscillation (QMO) is primarily confined to the tropical Indian and Pacific Oceans. Topics that were investigated are the partition of convective versus stratiform clouds, the vertical structure of precipitation rates, and the evolution of cloud types during the initial organization and the development of intraseasonal convective anomalies in the central Indian Ocean. During the initiation of the convective anomalies, the stratiform and convective rains have comparable rates; the prevailing cloud type experiences a trimodal evolution from shallow to deep convection, and finally to anvil and extended stratiform clouds. A major northwest/southeast-slanted rainband forms as the equatorial rainfall anomalies reach Sumatra, and the rainband subsequently propagates northeastward into the west Pacific Ocean. The enhanced precipitation in the west Pacific then rapidly traverses the Pacific along the Intertropical Convergence Zone, meanwhile migrating northward to the Philippine Sea. A seesaw teleconnection in rainfall anomalies is found between the southern Bay of Bengal (5-15°N, 80-100°E) and the eastern Pacific (5-15°N, 85-105°W). Local sea-surface temperature (SST)-rainfall anomalies display a negative simultaneous correlation in the off-equatorial regions but a zero correlation (quadrature phase relationship) near the equator. We propose that atmosphere-ocean interaction and the vertical monsoon easterly shear are important contributors to the northeastward propagation component of the intraseasonal rainband. The observed evidence presented here provides critical information for validating the numerical models, and it supports the self-induction mechanism theory for maintenance of the boreal summer ISO. © Springer-Verlag 2006."
"7403968786;7003811919;7005202019;7006005654;","Seasonal variations in diurnal temperature range from satellites and surface observations",2006,"10.1109/TGRS.2006.871895","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887470399&doi=10.1109%2fTGRS.2006.871895&partnerID=40&md5=57bfa6502226319fd5c37974f0739317","The diurnal temperature range (DTR) is an important climate-change variable and, until recently, it was derived from station observations of surface air temperature (Ta). Station-based observations are sparse and unevenly distributed, making the use of satellites an attractive option for evaluating DTR. In this study, satellite-based estimates of DTR are evaluated against ground measurements of surface skin temperature (Ts) and compared with weather-station observations based on Ta. Geographical and seasonal differences were identified in both ground- and satellite-derived DTRs. Estimates of DTR from station-observed air temperature represent all-sky conditions while satellite estimates of DTR from surface skin temperature represent clear conditions only. For both station observations and satellite estimates, DTRs at rural locations tend to be larger than at urban sites. The DTRs based on Ts are larger than those derived from Ta under both all and clear-sky conditions. Clouds tend to reduce the magnitude of the DTR. The station-observed DTRs are found to be larger in summer than in winter over the entire U.S. The satellite-derived DTRs are larger in spring and fall than in winter and summer over the eastern U.S., while they are larger in spring and summer than in fall and winter over the western part. Evapotranspiration from land vegetation and the effects of water-vapor radiative forcing have a major effect on the detected spatial and seasonal variations in the DTR patterns. © 2006 IEEE."
"55734348403;6506986541;","Position of the Gulf Stream influences lake nitrate concentrations in SW Ireland",2006,"10.1007/s00027-006-0847-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846796280&doi=10.1007%2fs00027-006-0847-0&partnerID=40&md5=64bd6dbbe6a343d761f45a64fe9fb3a5","A positive relationship was observed between winter nitrate concentrations in two lakes in SW Ireland and the latitudinal position of the Gulf Stream in the previous spring. Weaker but statistically significant relationships were apparent between the Gulf Stream position and weather variables, as well as soil moisture levels, in the same year. Wind speed, cloud cover and precipitation in May and June were negatively related to the Gulf Stream position in April. In contrast, air temperature and sunshine hours in May and June and the magnitude of the soil moisture deficit in June were positively related. There was also a positive correlation between the magnitude of the early summer soil moisture deficit and lake nitrate concentrations in the following winter. This three way linkage implies that the concentration of winter nitrate in these lakes is influenced by a sequence of related factors that are initiated by the latitudinal position of the Gulf Stream. In this sequence the position of the Gulf Stream appears to influence early summer weather in SW Ireland which in turn dictates the extent of moisture deficit in catchment soils and, consequently, the degree of nitrate loss to surface waters in the autumn. This connection, between events in the Atlantic Ocean, weather systems in the North West Atlantic and processes in catchment soils in SW Ireland has implications for both the quality and quantity of biota in lakes and catchments in the region. © Eawag, 2006."
"55754495900;7404976222;","Change of cloud amount and the climate warming on the Tibetan Plateau",2006,"10.1029/2006GL027946","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548599711&doi=10.1029%2f2006GL027946&partnerID=40&md5=419e73543ee51579946bd745749bf7d4","Based on the 6-hourly weather observations at 71 Itations across the central and eastern Tibetan Plateau (TP) during 1961-2003, the change of cloud amount and its possible connection with recent climate warming on TP were investigated. The low-level cloud amount exhibits a significant increasing trend during the nighttimes, leading to the enhanced atmospheric counterradiation, weakened effective terrestrial radiation, and the subsequently strong nocturnal surface warming. On the other hand, both the total and low-level cloud amounts during daytime display decreasing trends, resulting in more absorbing of direct solar radiation at the surface and the associated surface warming. Since the increase in nocturnal low-level cloud is more than the decrease of daytime low and total cloud amounts, such changes in cloud amount contribute to at least partly of the increased surface air temperature and its diminished diurnal range on TP. Copyright 2006 by the American Geophysical Union."
"6701518060;7103407382;7004353485;6602787586;","Aerosol variability in the Adriatic Sea from automated optical field measurements and Sea-viewing Wide Field-of-view Sensor (SeaWiFS)",2006,"10.1029/2006JD007226","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548588328&doi=10.1029%2f2006JD007226&partnerID=40&md5=826f7947d3d6713a083c5e07a6075f19","The aerosol optical properties in the Adriatic Sea are presented using a 9-year time series (1996-2005) of automated measurements collected on the Acqua Alta Oceanographic Tower (AAOT) in the northern part of the basin and a coincident satellite record obtained from an atmospheric correction scheme adapted for European seas and applied to the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). At AAOT, the overall averages of aerosol optical thickness τ<inf>a</inf> at 500 nm and Ångström exponent α are 0.29 ± 0.21 and 1.51 ± 0.34, respectively. The average single scattering albedo varies from 0.957 at 440 nm to 0.910 at 1020 nm. The aerosol size distribution derived by optical data inversion exhibits an increase of the radius of the accumulation mode with τ<inf>a</inf>. From 402 coincident data records, the agreement between satellite and field τ<inf>a</inf> is remarkable, with mean absolute percentage differences of 17-20% in the 412-870 nm spectral range. On the other hand, the satellite record tends to filter out occurrences of high τ<inf>a</inf>. The satellite-derived products are used to analyze the seasonal cycle over the Adriatic basin, showing minima in winter and maxima in summer (τ<inf>a</inf>(500) from 0.06 to 0.23). Then, the results of radiative transfer simulations are combined with the satellite-derived seasonal cycles of τ<inf>a</inf> and cloud fraction to determine the clear-sky aerosol direct radiative effect for the Adriatic Sea. At the surface, the aerosol load results in a monthly average cooling effect ranging from - 1 W m-2 in winter up to -9.6 W m-2 in August and a corresponding atmospheric warming from 0.5 to 4.6 W m-2. Copyright 2006 by the American Geophysical Union."
"35998927000;","Particle emissions from aviation: Microphysics, chemistry, and climate impact",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751040921&partnerID=40&md5=f83fb9e8b21173c24591a57fd284414c","Particulate emissions from aviation during cruise, their physical and chemical properties and the potential effects on Earth's atmosphere and climate constitute a rich and complex research area. Their relevance for the global climate system was identified in the early 1990s, and gains today increasing attention because of their likely role in the life cycle of upper tropospheric ice clouds or cirrus, respectively. An understanding of the impact mechanisms of aviation-related particle emissions on atmosphere and climate requires research on particle formation in gas turbines, on particle processing in chemically active exhaust plumes, on atmospheric processing and transformation of particles released into the upper troposphere and lowermost stratosphere, and also on the background aerosol of this particular atmospheric layer which forms the sink for the aircraft engine exhaust particles. Simultaneously, techniques have to be developed for improving the available measurement capabilities for relevant particle properties and constituents. The presented experimental work approaches the scientific subject from all necessary directions: The physical and chemical properties of emitted particles were identified under cruise altitude conditions and with more detailed methods during ground-test studies. The quantification of emissions for various aircraft resulted in a validated average emission index for particulate black carbon which is today widely used for the calculation of the aviation-related particle emissions in climate models and impact studies. The results achieved from this extensive experimental field work contributed considerably to the international assessment of the climate effects of aviation at the turn to the 21 st century. A European research programme on the properties and the processing of particles forming in an aircraft engine under controlled test-stand conditions was defined which built on the knowledge gained during the studies on aviation particle emissions at cruise. The project PartEmis was of high relevance also for the European aircraft engine industry and provided extensive new knowledge on particle emissions from aircraft engines. Particularly the connection of particle chemical and physical properties with the potential activation of combustion particles for the formation of cloud droplets will promote the understanding of the aerosol-cloud interaction concerning combustion particles. Furthermore, a robust method for the measurement of aerosol light absorption and thus for black carbon was developed and evaluated. Multi-Angle Absorption Photometry turned out to be widely applicable for measurements in engine exhaust as well as in the remote background atmosphere on mountain sites. Results from a first 2-years data record on black carbon in the free troposphere over central Europe were used in combination with the determined particle emission factors for aircraft engines for estimating the black carbon load of the free troposphere and for assessing the climate impact of particle emissions from aviation. The estimated magnitude of the expected aerosol radiative forcing is in close agreement with recent results from the European project TRADEOFF which represents today's state of knowledge on the subject of aviation radiative forcing."
"22956930200;7006861646;35729333400;","A clear-sky radiance archive from Meteosat ""water vapor"" observations",2006,"10.1029/2006JD007238","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250822506&doi=10.1029%2f2006JD007238&partnerID=40&md5=425a4f14972be03d43d04a614859cc4e","A long-term archive of clear-sky Meteosat ""water vapor"" observations, covering the July 1983 to February 1997 period with a 3 hourly time step and a spatial resolution of 0.625°, is presented. Cloud clearing is performed using a scene selection procedure based on the International Satellite Cloud Climatology Project DX product. In this procedure low cloud scenes are kept because of the negligible contribution of the low atmospheric layer in this spectral band. Cloud contamination is shown to have little influence on the clear-sky radiance (CSR) field and is mainly confined to the continental Intertropical Convergence Zone with values less than 0.5 K. This scene selection yields to a significantly enhanced sampling with respect to pure clear-sky in the subtropical high regions. Homogenization of the 14 year database is performed in accordance with existing technique. A comparison to the operational radiosondes archive indicates a small bias of 0.3 K that is stable throughout the period. A first analysis of the CSR variability reveals that the intraseasonal variance over the subtropical dry regions has a strong seasonal cycle in the Northern Hemisphere that is not observed in the Southern Hemisphere. Such a data set completes the ones currently available to document the water vapor variability of the troposphere from climatic down to regional and daily scales. Copyright 2006 by the American Geophysical Union."
"7410340979;6603742681;36842724800;56528895600;","Comparison of International Panel on Climate Change Fourth Assessment Report climate model simulations of surface albedo with satellite products over northern latitudes",2006,"10.1029/2005JD006728","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250883537&doi=10.1029%2f2005JD006728&partnerID=40&md5=41f24577be8d484f5b2f8ebc02009333","The surface albedos simulated by seventeen climate models over the northern latitudes of the Western Hemisphere were compared with satellite-derived albedo products provided by the International Satellite Cloud Climatology Project (ISCCP). Model simulations were conducted in support of the International Panel on Climate Change (IPCC) Fourth Assessment Report (AR.4). Results show the following: (1) Annual albedo of the region averaged for all models is fairly close to that provided by the ISCCP (0.351 versus 0.334). The difference between model average and ISCCP albedos is well below the standard deviation in albedo among models. (2) Most models simulated seasonal variations in regional albedo reasonably well. In summer, the models systematically overestimated albedo relative to the ISCCP data by as much as 0.05. In winter, large differences were detected among the climate models. (3) The spatial correlations among models, and between models and ISCCP, depend on geographic location, season and surface type. In general, the spatial correlation coefficients between individual models and the ISCCP data were highest for the land surface in midsummer and for the ocean surface in spring. Model bias was smaller for the ocean surface than for the land surface, and smaller in summer than in winter. (4) Unlike the modeling results, the satellite data showed large interannual variations in albedo and a systematic decreasing trend over the 16 year period of 1984-1999. Depending on season, the standard deviation of albedo interannual variation ranged from 0.036 to 0.074, and the linear regression slope of the decreasing trend ranged from -0.02 to -0.05 per decade according to ISCCP results. The large interannual variation and decreasing trend are not reflected in model simulations. Additional efforts are still required to improve surface albedo simulations in GCMs and its mapping from satellite. Copyright 2006 by the American Geophysical Union."
"16645036600;6603196127;56284545500;","General circulation model study on the green Sahara during the mid-Holocene: An impact of convection originating above boundary layer",2006,"10.1029/2005JD006398","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250835254&doi=10.1029%2f2005JD006398&partnerID=40&md5=b4483be3e1197504cb493e4cfc3a3960","The mechanism maintaining widespread vegetation over the Sahara, 6000 years before present (6kBP), is investigated with an atmospheric general circulation model (GCM) focusing on an impact of convection originating above the planetary boundary layer (PBL). The multiple cloud base Arakawa-Schubert scheme (MCB) is implemented in the GCM, and it is shown that MCB significantly strengthens the impact of vegetation over the Sahara on precipitation in this region. If it is assumed that the whole Sahara was covered by vegetation at 6kBP, the total precipitation is sufficient to maintain vegetation over the south and northwest Sahara. High-valued moist static energy air ranges from surface to the middle troposphere over the northern half of Intertropical Convergence Zone (ITCZ) in summer because of strong northward moisture transport in the lower troposphere. Convection originating above the PBL prevails in this region especially when the PBL top is lowered between night and early morning and strengthens the intrusion of the ITCZ into the Sahara. Then moisture is further transported northward by the African wave disturbances enhancing precipitation over the northwestern Sahara. Copyright 2006 by the American Geophysical Union."
"7005190227;7004241718;","Assessing crop water productivity from field to regional scale",2006,"10.1016/j.agwat.2006.06.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750616099&doi=10.1016%2fj.agwat.2006.06.011&partnerID=40&md5=ef75ae063519d11970e9428190b5a79e","As previous co-workers of Dr. Jans Wesseling, who headed the Department of Water Management of the Institute for Land and Water Management Research, i.e. the 'Instituut voor Cultuurtechniek en Waterhuishouding' (ICW), Wageningen from 1959 to 1987, we have written the present review article. We start with a short description of the hydrological problems, with a particular focus on groundwater, that affect agriculture in humid and temperate climates such as that of the Netherlands as well as in semi-arid climates. We then describe the highlights of the scientific career of Dr. Wesseling, who inspired us and colleagues that have worked with soil water flow under both saturated and unsaturated conditions in relation to the creation of optimal conditions for plant growth and yield. This is followed by an overview of the transient flow modeling of water and solute flow in heterogeneous soil-root systems under a variety of boundary conditions with a focus on the linkage between water use by the crop, and daily crop growth and crop yield, i.e. the so-called 'water productivity' relationship. Then the agreement between long-term predictions made with dynamic land capability models and field measurements are discussed in the context of model utility to establish design criteria for drainage systems for both humid as well as for semi-arid areas. We then review how to scale up from the field scale to the regional scale. Up-scaling from fields to a region can be done by identifying areas that are homogenous with respect to soil and hydrological properties. Effects of spatial heterogeneity can be further analyzed by running a field scale model for all combinations of soil-water-crop and weather combinations, i.e. simulation units for the areas under investigation. The aggregation of the various simulation units can be performed in a GIS-environment by overlaying the thematic maps of spatial variables like weather, land use, soil, irrigation, groundwater level and groundwater quality. In order to analyze water productivity at regional scale the output of the independent model runs can finally be synthesized with the help of post-processors and GIS. On the other hand earth observation satellites provide nowadays interesting information about degree of vegetation cover, leaf area index, crop type, crop yield, crop water stress and crop water use. This information can be regularly obtained under cloud-free conditions for different spatial and time resolutions. Consequently, the accuracy and reliability of spatial aggregation of representative input parameters, evapotranspiration (ET) and biomass simulated by distributed modelling can be compared with data obtained by satellite for different spatial and temporal scales. Once the combined use of model predictions and satellite data is verified, it will be possible to analyze the water productivity of an entire region of interest in detail and to provide specific recommendations for improvement. © 2006 Elsevier B.V. All rights reserved."
"7403508241;7004325649;7006783796;7102731389;7403282069;7407116104;7005673120;","The effect of environmental conditions on tropical deep convective systems observed from the TRMM satellite",2006,"10.1175/JCLI3940.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646341654&doi=10.1175%2fJCLI3940.1&partnerID=40&md5=c23f93d100dbca7d9da74c718803ec71","This study uses measurements of radiation and cloud properties taken between January and August 1998 by three Tropical Rainfall Measuring Mission (TRMM) instruments, the Clouds and the Earth's Radiant Energy System (CERES) scanner, the TRMM Microwave Imager (TMI), and the Visible and Infrared Scanner (VIRS), to evaluate the variations of tropical deep convective systems (DCSs) with sea surface temperature and precipitation. The authors find that DCS precipitation efficiency increases with SST at a rate of ∼2% K-1. Despite increasing rainfall efficiency, the cloud areal coverage rises with SST at a rate of about 7% K-1 in the warm tropical seas. There, the boundary layer moisture supply for deep convection and the moisture transported to the upper troposphere for cirrus anvil cloud formation increase by ∼6.3% and ∼4.0% K-1, respectively. The changes in cloud formation efficiency, along with the increased transport of moisture available for cloud formation, likely contribute to the large rate of increasing DCS areal coverage. Although no direct observations are available, the increase of cloud formation efficiency with rising SST is deduced indirectly from measurements of changes in the ratio of DCS ice water path and boundary layer water vapor amount with SST. Besides the cloud areal coverage, DCS cluster effective sizes also increase with precipitation. Furthermore, other cloud properties, such as cloud total water and ice water paths, increase with SST. These changes in DCS properties will produce a negative radiative feedback for the earth's climate system due to strong reflection of shortwave radiation by the DCS. These results significantly differ from some previously hypothesized dehydration scenarios for warmer climates, partially support the thermostat hypothesis but indicate a smaller magnitude of the negative feedback, and have great potential in testing current cloud-system-resolving models and convective parameterizations of general circulation models. © 2006 American Meteorological Society."
"6602334551;","A study of solar radiation climate at Cairo urban area, Egypt and its environs",2006,"10.1002/joc.1349","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750982127&doi=10.1002%2fjoc.1349&partnerID=40&md5=a4e85f716b2816136448281c1eed9ee9","The measured values of the hourly global solar radiation, G, and its diffuse component, D, on a horizontal surface for a 12-year period (1992-2003) have been collected and used to examine the solar radiation characteristics in the urban area of Cairo, Egypt. The corresponding values of the diffuse fraction of global radiation, K, have been calculated. Diurnal variations of the results have been investigated. Also, the daily total values and their monthly and seasonal means, as well as their frequency distributions, have been calculated and investigated. The results reveal that Cairo has annual mean values of G, D, and K equal to 18.57, 6.10 MJ m-2 and 0.35, respectively. The seasonal and climatic effects on the fluctuation of the results are discussed. These effects were particularly large during the winter and spring months owing to the high fluctuation of the atmospheric conditions with respect to the amount of water content, clouds, and concentration of aerosol and dust particles. It was found that the reduction of G due to the effect of clouds is small (2.8%), which in turn reflects the low degree of cloudiness over Cairo due to the impacts of urbanization. A comparative study has also been done to investigate the effect of urbanization processes on the global radiation values received at urban Cairo. It was found that G values received during the non-urbanized period (1969-1973) highly exceeded the radiation values received during the recent urbanized period (1999-2003) for all months of the year, and the annual mean of the relative reduction was found to be 17.63%. Copyright © 2006 Royal Meteorological Society."
"7201706787;10241985000;","New insight into the disappearing Arctic sea ice",2006,"10.1029/2006EO460001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845563044&doi=10.1029%2f2006EO460001&partnerID=40&md5=4cc1acd34aa9ba5025ba943c58e937c8",[No abstract available]
"7101959253;55843404000;7403233841;7005626683;7202619752;","A bootstrap technique for testing the relationship between local-scale radar observations of cloud occurrence and large-scale atmospheric fields",2006,"10.1175/JAS3772.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845237622&doi=10.1175%2fJAS3772.1&partnerID=40&md5=12d0ff002895ab332f27a71195c66d79","A classification scheme is created to map the synoptic-scale (large scale)atmospheric state to distributions of local-scale cloud properties. This mapping is accomplished by a neural network that classifies 17 months of synoptic-scale initial conditions from the rapid update cycle forecast model into 25 different states. The corresponding data from a vertically pointing millimeter-wavelength cloud radar (from the Atmospheric Radiation Measurement Program Southern Great Plains site at Lamont, Oklahoma) are sorted into these 25 states, producing vertical profiles of cloud occurrence. The temporal stability and distinctiveness of these 25 profiles are analyzed using a bootstrap resampling technique. A stable-state-based mapping from synoptic-scale model fields to local-scale cloud properties could be useful in three ways. First, such a mapping may improve the understanding of differences in cloud properties between output from global climate models and observations by providing a physical context. Second, this mapping could be used to identify the cause of errors in the modeled distribution of clouds - whether the cause is a difference in state occurrence (the type of synoptic activity) or the misrepresentation of clouds for a particular state. Third, robust mappings could form the basis of a new statistical cloud parameterization. © 2006 American Meteorological Society."
"55339298600;6701895637;16444240700;6602176524;6603868770;7404369915;57203423392;6603873829;12801836100;6603341831;","Comparison of model predicted low-level cloud parameters with satellite remote sensing observations during the BALTEX Bridge Campaigns",2006,"10.1016/j.atmosres.2005.12.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749124929&doi=10.1016%2fj.atmosres.2005.12.005&partnerID=40&md5=83b8046752eaa3c9d0e6cf482b03900f","A pressing task in numerical weather prediction and climate modelling is the evaluation of modelled cloud fields. Recent progress in spatial and temporal resolution of satellite remote sensing increases the potential of such evaluation efforts. This paper presents new methodologies to compare satellite remote sensing observations of clouds and output of atmospheric models and demonstrates their usefulness for evaluation. The comparison is carried out for two MODerate resolution Imaging Spectrometer (MODIS) scenes from the BALTEX Bridge Campaigns. Both scenes are characterised by low-level clouds with a substantial amount of liquid water. Cloud cover and cloud optical thickness of five different models, LM, Méso-NH, MM5 (non-hydrostatic models), RACMO2, and RCA (regional climate models) as well as corresponding retrievals from high resolution remote sensing observations of MODIS onboard the Terra satellite form the basis of a statistical analysis to compare the data sets. With the newly introduced patchiness parameters it is possible to separate differences between the two scenes on the one hand and between the models and the satellite on the other hand. We further introduce a new approach to spatially aggregate cloud optical thickness. Generally the models overestimate cloud optical thickness which can in part be ascribed to the lack of subgrid-scale variability. However, LM underestimates the frequency of occurrence of cloud optical thickness at values around 25. Furthermore, we compare the standard operational output of the non-hydrostatic models to simulations of the same models including parameterised shallow convection. However, clear improvements in the representation of low-level clouds are not found for these models. A change of the coefficients for autoconversion in RCA shows that LWP and precipitation strongly depend on this parameter. Refined vertical resolution, implemented in RACMO2, leads to a better agreement between model and satellite but still leaves room for further improvements. In general, this study reveals deficiencies of the models in representing low-level clouds, in particular for a stratiform cloud. © 2006 Elsevier B.V. All rights reserved."
"8900751100;7501757094;57198472289;","Model and observational analysis of the northeast U.S. regional climate and its relationship to the PNA and NAO patterns during early winter",2006,"10.1175/MWR3234.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845451213&doi=10.1175%2fMWR3234.1&partnerID=40&md5=1d2373a6680e8ce03b38f293dd7175b0","The relationship between the large-scale circulation and regional climate of the northeast United States is investigated for early winter using observational data and the State University of New York at Albany regional climate model. Simulated patterns of temperature, precipitation, and atmospheric circulation compare well with observations, despite a cold, dry bias. Ten December runs are analyzed to investigate the impact of the Pacific-North American (PNA) pattern on temperature, precipitation, clouds, and circulation features. During a positive PNA pattern, the simulated and observed eastern U.S. jet shifts to the southeast, coinciding with cold, dry conditions in the Northeast. This shift and intensification of the upper-level jet stream during a positive PNA pattern coincides with a greater frequency of cyclones and anticyclones along a distinct southwest-northeast track. Despite increased cyclone activity, total wintertime precipitation is below normal during a positive PNA pattern because of enhanced stability and subsidence over land, along with lower-atmospheric moisture content. Lower surface air temperatures during a positive PNA pattern result in enhanced simulated cloud cover over the Great Lakes and Atlantic Ocean due to increased thermal contrast and fluxes of sensible and latent heat, and a reduction in clouds over land. Interactions between the PNA and North Atlantic Oscillation (NAO) patterns impact the Northeast winter climate. Observed frontal passages through New York are most abundant during a negative PNA and positive NAO pattern, with a zonal upper-level jet positioned over New York. A positive PNA pattern is frequently characterized by an earlier observed Great Lakes ice season, while the greatest lake-effect snowfall occurs during a positive PNA and negative NAO pattern. The NAO pattern has the largest impact on northeast U.S. temperatures and the eastern U.S. upper-level jet during a positive PNA pattern. © 2006 American Meteorological Society."
"6701895637;55339298600;6603868770;16444240700;6602176524;6603196991;57203423392;6603873829;7003728829;6603341831;14720453100;","Model predicted low-level cloud parameters. Part I: Comparison with observations from the BALTEX Bridge Campaigns",2006,"10.1016/j.atmosres.2006.01.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749155220&doi=10.1016%2fj.atmosres.2006.01.010&partnerID=40&md5=b561b14e56834d65c444e856a9fc003d","The BALTEX Bridge Campaigns (BBC), which were held in the Netherlands in 2001 and 2003 around the Cabauw Experimental Site for Atmospheric Research (CESAR), have provided detailed information on clouds. This paper is an illustration of how these measurements can be used to investigate whether 'state-of-the-art' atmospheric models are capable of adequately representing clouds. Here, we focus on shallow low-level clouds with a substantial amount of liquid water. In situ, ground-based and satellite remote sensing measurements were compared with the output of three non-hydrostatic regional models (Lokal-Modell, LM; Méso-NH; fifth-generation Mesoscale Model, MM5) and two hydrostatic regional climate models (Regional Atmospheric Climate Model version 2, RACMO2; Rossby Centre Atmospheric Model, RCA). For the two selected days, Méso-NH and MM5 reproduce the measured vertical extent of the shallow clouds, but the liquid water content of the clouds is generally overestimated. In LM and the climate models the inversion is too weak and located at a level too close to the surface resulting in an overestimation of the vertical extent of the clouds. A sensitivity integration with RACMO2 shows that the correspondence between model output and measurements can be improved by a doubling of the vertical resolution; this induces an increase in the modelled inversion strength and cloud top pressure. LM and Méso-NH underestimate the lifetime of clouds. A comparison between model output and cloud cover derived from the Moderate Resolution Imaging Spectrometer (MODIS) indicates that this deficiency is not due to advection of too small cloud systems; it is rather due to an overestimation of the variability in the vertical velocity. All models overestimate the specific humidity near the surface and underestimate it at higher atmospheric levels, indicating that the models underestimate the mixing of moisture in the boundary layer. This deficiency is slightly reduced by inclusion of parameterised shallow convection in the non-hydrostatic models, which enhances the mixing of heat and moisture in the boundary layer. Consequently, the explicitly resolved updrafts weaken resulting in reduced condensation rates and lower liquid water path. The temporal variability of cloud occurrence is hardly affected by inclusion of parameterised shallow convection. © 2006 Elsevier B.V. All rights reserved."
"7004055178;57199054070;","Radiative transfer in shallow cumulus cloud fields: Observations and first analysis with the Diram instrument during the BBC-2 field campaign in May 2003",2006,"10.1016/j.atmosres.2005.09.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749343342&doi=10.1016%2fj.atmosres.2005.09.006&partnerID=40&md5=d9176de0395d88e0e3f9bc620012a759","The cloud albedo is a crucial parameter in radiation budget studies, and is one of the main forcings in climate. We have designed and made a device, Diram (directional radiance distribution measurement device), which not only measures reflection and transmission of solar radiation through clouds, but which also determines the radiance distribution. The construction contains 42 sensors, consisting of a collimation system and a detector, which are mounted in two domes (21 in each). The collimators reduce the field of view of each sensor to ∼7°. The domes were mounted on top and below of the Meteo France Merlin IV research aircraft. The 42 signals were continuously logged with a frequency of 10 Hz during a number of flights in the framework of the Baltex Bridge-2 campaign at Cabauw (The Netherlands) in May 2003. The Diram instrument provided radiances during in situ observations of cumulus and (broken) stratocumulus clouds and detected anisotropic effects in solar radiation scattered by clouds which are due to different cloud geometries and which are related to microphysical cloud properties. Microphysical cloud properties were obtained from the Gerber PVM100A optical sensor aboard the aircraft. Liquid water content and particle surface area were logged with a frequency of 200 Hz. Data have been collected from a total of 10 days in different weather conditions (clear sky, broken cumulus, stratocumulus and multilayered cloud). A clear sky test of the Diram indicated that the device was able to reproduce the Rayleigh scattering pattern. During flights in stratocumulus fields, strongly anisotropic patterns were observed. The DIRAM observations confirm that in thin clouds a strong preference for forward scattering is observed in the transmitted radiation field while for thicker clouds the pattern becomes more isotropic, with a slightly brighter centre relative to the limb direction. © 2006 Elsevier B.V. All rights reserved."
"7006377579;7006235542;35552588700;14720303100;7005858663;","Computational assessment of a proposed technique for global warming mitigation via albedo-enhancement of marine stratocumulus clouds",2006,"10.1016/j.atmosres.2005.11.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749147663&doi=10.1016%2fj.atmosres.2005.11.013&partnerID=40&md5=fbf8c6873ef0b0266efe5a450367ed55","A simplified version of the model of marine stratocumulus clouds developed by Bower, Jones and Choularton [Bower, K.N., Jones, A., and Choularton, T.W., 1999. A modeling study of aerosol processing by stratocumulus clouds and its impact on GCM parameterisations of cloud and aerosol. Atmospheric Research, Vol. 50, Nos. 3-4, The Great Dun Fell Experiment, 1995-special issue, 317-344.] was used to examine the sensitivity of the albedo-enhancement global warming mitigation scheme proposed by Latham [Latham, J., 1990. Control of global warming? Nature 347, 339-340; Latham, J., 2002. Amelioration of global warming by controlled enhancement of the albedo and longevity of low-level maritime clouds. Atmos. Sci. Letters (doi:10.1006/Asle.2002.0048).] to the cloud and environmental aerosol characteristics, as well as those of the seawater aerosol of salt-mass ms and number concentration ΔN, which-under the scheme-are advertently introduced into the clouds. Values of albedo-change ΔA and droplet number concentration Nd were calculated for a wide range of values of ms, ΔN, updraught speed W, cloud thickness ΔZ and cloud-base temperature TB: for three measured aerosol spectra, corresponding to ambient air of negligible, moderate and high levels of pollution. Our choices of parameter value ranges were determined by the extent of their applicability to the mitigation scheme, whose current formulation is still somewhat preliminary, thus rendering unwarranted in this study the utilisation of refinements incorporated into other stratocumulus models. In agreement with earlier studies: (1) ΔA was found to be very sensitive to ΔN and (within certain constraints) insensitive to changes in ms, W, ΔZ and TB; (2) ΔA was greatest for clouds formed in pure air and least for highly polluted air. In many situations considered to be within the ambit of the mitigation scheme, the calculated ΔA values exceeded those estimated by earlier workers as being necessary to produce a cooling sufficient to compensate, globally, for the warming resulting from a doubling of the atmospheric carbon dioxide concentration. Our calculations provide quantitative support for the physical viability of the mitigation scheme and offer new insights into its technological requirements. © 2006."
"23065650200;7102591209;35585698100;7202057166;","Testing and comparing the modified anomalous diffraction approximation",2006,"10.1175/JAS3775.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845255804&doi=10.1175%2fJAS3775.1&partnerID=40&md5=034e75887cee9382ba328054f01cbcd1","The modified anomalous diffraction approximation (MADA) is used to predict absorption and extinction in water and ice clouds, but it does not predict the scattering phase function or asymmetry parameter g. In conjunction with g parameterizations, it has been used in satellite remote sensing and to treat the radiative properties of ice clouds in global climate models. However, it has undergone only limited testing. This study 1) compares extinction efficiencies (Qext) predicted by MADA for a laboratory grown ice cloud against corresponding Qext measurements over the wavelength range 2-14 μm; 2) tests absorption efficiencies (Qabs) and Qext predicted by MADA against those predicted by T-matrix theory and the finite difference time domain (FDTD) method; and 3) compares MADA with three popular schemes used for predicting the radiative properties of cirrus clouds. In addition, the photon tunneling process may contribute up to 45% of the absorption in water clouds at some terrestrial wavelengths, but its role in ice clouds is uncertain since it depends on particle shape. For the first time, the efficiency of photon tunneling was parameterized in terms of ice particle shape. Finally, an alternate formulation of MADA that offers some physical insights is presented. MADA errors relative to the Qext measurements were 3.0% on average, while mean MADA errors relative to Qabs from T-matrix, over the wavelength range 2-18 μm (size parameter range 2-22), were 5.9%. The mean error for the single scattering albedo relative to T-matrix calculations was 2.5%. MADA absorption errors relative to FDTD over the wavelength range 3-100 μm were no greater than 15% for six ice particle shapes. Finally, the absorption coefficients predicted by MADA and two other popular parameterizations generally agreed within 5%. © 2006 American Meteorological Society."
"26657775800;7403253358;7102080550;","Short-range prediction of a heavy precipitation event by assimilating Chinese CINRAD-SA radar reflectivity data using complex cloud analysis",2006,"10.1007/s00703-005-0177-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750516270&doi=10.1007%2fs00703-005-0177-0&partnerID=40&md5=83388eb140d6b5e2388d8a184577e7ad","With the ARPS (Advanced Regional Prediction System) Data Analysis System (ADAS) and its complex cloud analysis scheme, the reflectivity data from a Chinese CINRAD-SA Doppler radar are used to analyze 3D cloud and hydrometeor fields and in-cloud temperature and moisture. Forecast experiments starting from such initial conditions are performed for a northern China heavy rainfall event to examine the impact of the reflectivity data and other conventional observations on short-range precipitation forecast. The full 3D cloud analysis mitigates the commonly known spin-up problem with precipitation forecast, resulting a significant improvement in precipitation forecast in the first 4 to 5 hours. In such a case, the position, timing and amount of precipitation are all accurately predicted. When the cloud analysis is used without in-cloud temperature adjustment, only the forecast of light precipitation within the first hour is improved. Additional analysis of surface and upper-air observations on the native ARPS grid, using the 1 degree real-time NCEP AVN analysis as the background, helps improve the location and intensity of rainfall forecasting slightly. Hourly accumulated rainfall estimated from radar reflectivity data is found to be less accurate than the model predicted precipitation when full cloud analysis is used. © Springer-Verlag 2006."
"15031035100;7202162685;35264351500;7102389805;","Transition between suppressed and active phases of intraseasonal oscillations in the Indo-Pacific warm pool",2006,"10.1175/JCLI3924.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751429242&doi=10.1175%2fJCLI3924.1&partnerID=40&md5=b03488cf7c5a18753c9f854d2fd52f2d","Intraseasonal oscillations (ISOs) are important large-amplitude and large-scale elements of the tropical Indo-Pacific climate with time scales in the 20-60-day period range, during which time they modulate higher-frequency tropical weather. Despite their importance, the ISO is poorly simulated and predicted by numerical models. A joint diagnostic and modeling study of the ISO is conducted, concentrating on the period between the suppressed and active (referred to as the ""transition"") period that is hypothesized to be the defining stage for the development of the intraseasonal mode and the component that is most poorly simulated. The diagnostic study uses data from the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). It is found that during the transition period, the ocean and the atmosphere undergo gradual but large-scale and high-amplitude changes, especially the moistening of the lower troposphere caused jointly by the anomalously warm sea surface temperature arising from minimal cloud and low winds during the suppressed phase and the large-scale subsidence that inhibits the formation of locally deep convection. Using a cloud classification scheme based on microwave and infrared satellite data, it is observed that midtop (cloud with a top in the middle troposphere) non-precipitating clouds are a direct response of the low-level moisture buildup. To investigate the sensitivity of ISO simulations to the transitional phase, the European Centre for Medium-Range Weather Forecasts (ECMWF) coupled ocean-atmosphere climate model is used. The ECMWF was run serially in predictive ensemble mode (five members) for 30-day periods starting from 1 December 1992 to 30 January 1993, encompassing the ISO occurring in late December. Predictability of the active convective period of the ISO is poor when initialized before the transitional phases of the ISO. However, when initialized with the correct lower-tropospheric moisture field, predictability increases substantially, although the model convective parameterization appears to trigger convection too quickly without allowing an adequate buildup of convective available potential energy during the transition period. © 2006 American Meteorological Society."
"6701394887;56250117600;56999946500;","A model to predict cloud density from midlatitude atmospheric soundings for microwave radiative transfer applications",2006,"10.1029/2006RS003463","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847074658&doi=10.1029%2f2006RS003463&partnerID=40&md5=ebbcef403f2811195c2012f897c6614e","A new model for computing cloud liquid density from vertical profiles of meteorological variables, provided by either radio soundings or atmospheric analyses, is proposed. It has been developed for local-scale applications, in particular for a midlatitude environment such as the Mediterranean area, although the methodology can be easily extended to other climatic zones. The model has been derived from a numerical simulation of a cloudy event that occurred in the Mediterranean basin, performed by means of a microphysical mesoscale meteorological simulation package. The validation has been mainly carried out through a comparison between brightness temperature simulations in cloudy conditions and satellite microwave radiometric data over the Mediterranean Sea. The simulations have been performed by applying a radiative transfer scheme to a set of atmospheric profiles consisting of both European Centre for Medium-Range Weather Forecasts (ECMWF) analyses and radiosonde measurements. Two literature models have been considered as benchmarks. The new model reproduces the Special Sensor Microwave Imager brightness temperature statistics in the Mediterranean area fairly well. Furthermore, it predicts an integrated liquid water content which is in agreement with that supplied by the ECMWF analyses. Copyright 2006 by the American Geophysical Union."
"56000281400;56780565800;6603109490;","A new visibility parameterization for warm-fog applications in numerical weather prediction models",2006,"10.1175/JAM2423.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846008399&doi=10.1175%2fJAM2423.1&partnerID=40&md5=b525bcf90027972516d8a96ad482d9f2","The objective of this work is to suggest a new warm-fog visibility parameterization scheme for numerical weather prediction (NWP) models. In situ observations collected during the Radiation and Aerosol Cloud Experiment, representing boundary layer low-level clouds, were used to develop a parameterization scheme between visibility and a combined parameter as a function of both droplet number concentration Nd and liquid water content (LWC). The current NWP models usually use relationships between extinction coefficient and LWC. A newly developed parameterization scheme for visibility, Vis = f(LWC, Nd), is applied to the NOAA Nonhydrostatic Mesoscale Model. In this model, the microphysics of fog was adapted from the 1D Parameterized Fog (PAFOG) model and then was used in the lower 1.5 km of the atmosphere. Simulations for testing the new parameterization scheme are performed in a 50-km innermost-nested simulation domain using a horizontal grid spacing of 1 km centered on Zurich Unique Airport in Switzerland. The simulations over a 10-h time period showed that visibility differences between old and new parameterization schemes can be more than 50%. It is concluded that accurate visibility estimates require skillful LWC as well as Nd estimates from forecasts. Therefore, thel current models can significantly over-/underestimate Vis (with more than 50% uncertainty) depending on environmental conditions. Inclusion of Nd as a prognostic (or parameterized) variable in parameterizations would significantly improve the operational forecast models. © 2006 American Meteorological Society."
"7005793077;7202987319;","The origin of the savanna biome",2006,"10.1111/j.1365-2486.2006.01239.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749984184&doi=10.1111%2fj.1365-2486.2006.01239.x&partnerID=40&md5=a1d57e65377049ae585af218e1fb64ca","Savannas are a major terrestrial biome, comprising of grasses with the C4 photosynthetic pathway and trees with the C3 type. This mixed grass-tree biome rapidly appeared on the ecological stage 8 million years ago with the near-synchronous expansion of C4 grasses around the world. We propose a new hypothesis for this global event based on a systems analysis that integrates recent advances in how fire influences cloud microphysics, climate and savanna ecology in a low carbon dioxide (CO2) world. We show that fire accelerates forest loss and C4 grassland expansion through multiple positive feedback loops that each promote drought and more fire. A low CO2 atmosphere amplifies this cycle by limiting tree recruitment, allowing the ingress of C4 grasses to greatly increase ecosystem flammability. Continued intensification of land use could enhance or moderate the network of feedbacks that have initiated, promoted and sustained savannas for millions of years. We suggest these alterations will overprint the effects of anthropogenic atmospheric change in coming decades. © 2006 Blackwell Publishing Ltd."
"7401635168;36728924100;7402892323;57206619545;7005964407;6603889085;","Seasonal variations in SO2 plume transport over Japan: Observations at the summit of Mt. Fuji from winter to summer",2006,"10.1016/j.atmosenv.2006.06.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748797391&doi=10.1016%2fj.atmosenv.2006.06.017&partnerID=40&md5=5818fe067d34d1d181fa1eb4809d0333","We undertook continuous measurements of SO2 concentrations at the summit of Mt. Fuji, Japan (3776 m above sea level), during the period January to July, 2004. These data include the first data set that fills the previous gap in SO2 time series for the springtime middle troposphere over Japan. The time series shows trends in high-SO2 long-range transport events from winter to spring. Elevated SO2 concentrations are always accompanied by elevated CO and 222Rn concentrations, and backward trajectories for such events indicate a continental origin. These data display clear sporadic signatures of Asian outflow over Japan to the North Pacific. Such high-SO2 events decline in strength and frequency during spring. The observed seasonal variation of SO2 events may in fact have nothing to do with seasonality in SO2 emissions from the Asian continent, as seasonal patterns in SO2 events show a similar phase shift to that of the prevailing wind direction and relative humidity (RH) observed on-site. The changes in air mass indicated by daily backward trajectory analysis may also explain the observed temporal changes in SO2 events. A major factor appears to be the removal of SO2 from the continental pollution plume during long-range transport. The SO2-bearing polluted air is dry during the depths of winter; accordingly, little SO2 is removed by cloud processes at this time of year. The nature of the air mass changes during spring when increasing humidity levels lead to the increased removal of SO2 by cloud processes. RH data along the air mass travel path also support the importance of cloud processes in reducing SO2 concentrations within the pollution plume. © 2006 Elsevier Ltd. All rights reserved."
"7404211378;7403681584;","Physical processes associated with the tropical Atlantic SST meridional gradient",2006,"10.1175/JCLI3923.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751399492&doi=10.1175%2fJCLI3923.1&partnerID=40&md5=86c57546049ed9124e1921d680db9e85","The major modes of seasonal sea surface temperature (SST) meridional gradient and their connection with some regional mean SST indices in the Atlantic Ocean are examined using reanalysis data. The focus of the work is on the evolution of the dominant mode of the meridional SST gradient in boreal spring and the associated physical processes. The spatial distribution of the dominant mode in boreal spring is a seesaw pattern, reflecting the opposite variation of the meridional SST gradient between the subtropical and tropical North Atlantic, which resulted from a coherent warming or cooling with maxima along 10°-15°N. It is confirmed that this mode is dominated by the wind-evaporation-SST feedback. The feedback persists a longer time in the western Atlantic than in the eastern. The contribution to the SST variation is mainly from latent heat flux. The surface longwave and shortwave cloud radiative forcings are mainly determined by low cloud cover variations. The authors also found that the thermodynamic mode that peaked in boreal spring becomes weak in the following boreal summer. A similar thermodynamic mode appears in a northward position in boreal autumn, and its life cycle is shorter than the one in boreal spring. In contrast to the leading mode in boreal spring, it is shown that the leading mode in boreal summer is a dynamical air-sea feedback mode, reflecting a coherent warming or cooling pattern extending from the Angolan coast toward the equator in the Gulf of Guinea. The thermodynamic processes act as a negative feedback. The net surface latent heat flux anomalies are the leading damping factor, while the sensible heat flux plays the same role on a smaller scale. © 2006 American Meteorological Society."
"8529447300;7006563002;6603134964;56702490400;","Climate is affected more by maritime than by continental land use change: A multiple scale analysis",2006,"10.1016/j.gloplacha.2006.05.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750517559&doi=10.1016%2fj.gloplacha.2006.05.005&partnerID=40&md5=9b09ed44e5094a5390f100a89d0fb61f","Tropical deforestation appears to have larger impacts on local, regional and global climate when it occurs under maritime conditions rather then under continental conditions. At the local scale, we compare results from a field experiment in Puerto Rico with other long-term studies of the changes in surface fluxes after deforestation. Changes in surface fluxes are larger in maritime situations because a number of feedback mechanisms appears less relevant (e.g. the dependency of soil moisture on recycling of water and the larger reduction of net radiation in the wet season due to clouds in continental regions). Pastures may evaporate at similarly high rates as forests when soil moisture is sufficient, which has a strong reducing effect on the sensible heat flux after deforestation. At the regional scale (∼ 102 km2), model simulations show that the meso-scale sea breeze circulation under maritime conditions is more effective in transporting heat and moisture to the upper troposphere than convection is in the continental case. Thus islands function as triggers of convection, whereas the intensity of the sea breeze-trigger is sensitive to land use change. At the global scale, using satellite-derived latent heating rates of the upper troposphere, it is shown that 40% of the latent heating associated with deep convection takes place in the Maritime Continent (Indonesia and surroundings) and may be produced mostly by small islands. Continents contribute only 20% of the latent heating of the upper troposphere. Thus, sea breeze circulations exert significant influence on the Hadley cell circulation. These results imply that, from a climate perspective, further deforestation studies would do well to focus more on maritime conditions. © 2006 Elsevier B.V. All rights reserved."
"7101735729;6603125722;36815358800;","Seasonal variation in the stable isotopic composition of precipitation in the tropical montane forests of Monteverde, Costa Rica",2006,"10.1029/2005WR004535","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846356118&doi=10.1029%2f2005WR004535&partnerID=40&md5=1fa49d83dad62ace00b5ba6e0a144206","Climate and land use change may diminish orographic clouds over tropical montane forests, stressing biota and water resources during dry seasons. From 2003 to 2005 we measured the stable isotopic composition of precipitation and throughfall in Monteverde, Costa Rica, to distinguish convective, wet season rainfall associated with the Intertropical Convergence Zone (ITCZ) from dry season, orographic rain produced by northeasterly trade winds. While event-to-event fluctuations of δ18O and δ2H are high, monthly samples reveal a seasonal signal that may be used to trace water through the hydrologic cycle. Deuterium excess indicates that water evaporated from land is an important flux to the region during the transitional and dry seasons when winds from the Caribbean slope dominate. Following the shift to convective rainfall at the start of the wet season, when the western equatorial winds influence the Pacific slope of Costa Rica, d excess values become depressed. Yet as the wet season progresses, d excess begins to climb. These data suggest that several months of rain are needed following an acute dry season on the northern Pacific slope before a terrestrial evaporative signal is detected in wet season precipitation. The evaporative flux may result from a wet season expansion of surface water bodies and flooding of seasonal wetlands. Copyright 2006 by the American Geophysical Union."
"7005903001;13907206700;","Gigantic volcanic eruptions and climatic change in the early Eocene",2006,"10.1007/s00531-006-0085-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751088521&doi=10.1007%2fs00531-006-0085-7&partnerID=40&md5=aac1fff1b2a9ba2230ad35b016df9fcf","23 layers of altered volcanic ash (bentonites) originating from the North Atlantic Igneous Province have been recorded in early Eocene deposits of the Austrian Alps, about 1,900 km away from the source area. The Austrian bentonites are distal equivalents of the ""main ash-phase"" in Denmark and the North Sea basin. We have calculated the total eruption volume of this series as 21,000 km3, which occurred in 600,000 years. The most powerful single eruption of this series took place 54.0 million years ago (Ma) and ejected ca. 1,200 km3 of ash material, which makes it one of the largest basaltic pyroclastic eruptions in geological history. The clustering of eruptions must have significantly affected the incoming solar radiation in the early Eocene by the continuous production of stratospheric dust and aerosol clouds. This hypothesis is corroborated by oxygen isotope values, which indicate a global decrease of sea surface temperatures between 1 and 2°C during this major phase of explosive volcanism. © Springer-Verlag 2006."
"57197341152;6602624109;7101899588;7102059695;6602638842;26426079600;9841756200;56187256200;7005124488;55272324200;56016103100;6506182860;55914429700;35430463900;35445938100;7005126327;36829694300;","High resolution simulation of recent Arctic and Antarctic stratospheric chemical ozone loss compared to observations",2006,"10.1007/s10874-006-9028-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750599495&doi=10.1007%2fs10874-006-9028-8&partnerID=40&md5=ddb2b35693ef2b75afea085a7cc6aa88","Simulations of polar ozone losses were performed using the three-dimensional high-resolution (1° × 1°) chemical transport model MIMOSA-CHIM. Three Arctic winters 1999-2000, 2001-2002, 2002-2003 and three Antarctic winters 2001, 2002, and 2003 were considered for the study. The cumulative ozone loss in the Arctic winter 2002-2003 reached around 35% at 475 K inside the vortex, as compared to more than 60% in 1999-2000. During 1999-2000, denitrification induces a maximum of about 23% extra ozone loss at 475 K as compared to 17% in 2002-2003. Unlike these two colder Arctic winters, the 2001-2002 Arctic was warmer and did not experience much ozone loss. Sensitivity tests showed that the chosen resolution of 1° × 1° provides a better evaluation of ozone loss at the edge of the polar vortex in high solar zenith angle conditions. The simulation results for ozone, ClO, HNO3, N2O, and NOy for winters 1999-2000 and 2002-2003 were compared with measurements on board ER-2 and Geophysica aircraft respectively. Sensitivity tests showed that increasing heating rates calculated by the model by 50% and doubling the PSC (Polar Stratospheric Clouds) particle density (from 5 × 10-3 to 10-2 cm-3) refines the agreement with in situ ozone, N2O and NOi levels. In this configuration, simulated ClO levels are increased and are in better agreement with observations in January but are overestimated by about 20% in March. The use of the Burkholder et al. (1990) Cl2O2 absorption cross-sections slightly increases further ClO levels especially in high solar zenith angle conditions. Comparisons of the modelled ozone values with ozonesonde measurement in the Antarctic winter 2003 and with Polar Ozone and Aerosol Measurement III (POAM III) measurements in the Antarctic winters 2001 and 2002, shows that the simulations underestimate the ozone loss rate at the end of the ozone destruction period. A slightly better agreement is obtained with the use of Burkholder et al. (1990) Cl2O2 absorption cross-sections. © Springer Science+Business Media B.V. 2006."
"6603962101;7202619752;57210379777;","The behavior of synoptic-scale errors in the Eta Model",2006,"10.1175/MWR3238.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845402344&doi=10.1175%2fMWR3238.1&partnerID=40&md5=7f2d66a2196c524dfefb6259ebccbeab","A previous study of the mean spatial bias errors associated with operational forecast models motivated an examination of the mechanisms responsible for these biases. One hypothesis for the cause of these errors is that mobile synoptic-scale phenomena are partially responsible. This paper explores this hypothesis using 24-h forecasts from the operational Eta Model and an experimental version of the Eta run with Kain-Fritsch convection (EtaKF). For a sample of 44 well-defined upper-level short-wave troughs arriving on the west coast of the United States, 70% were underforecast (as measured by the 500-hPa geopotential height), a likely result of being undersampled by the observational network. For a different sample of 45 troughs that could be tracked easily across the country, consecutive model runs showed that the height errors associated with 44% of the troughs generally decreased in time, 11% increased in time, 18% had relatively steady errors, 2% were uninitialized entering the West Coast, and 24% exhibited some other kind of behavior. Thus, landfalling short-wave troughs were typically underforecast (positive errors, heights too high), but these errors tended to decrease as they moved across the United States, likely a result of being better initialized as the troughs became influenced by more upper-air data. Nevertheless, some errors in short-wave troughs were not corrected as they fell under the influence of supposedly increased data amount and quality. These results indirectly show the effect that the amount and quality of observational data has on the synoptic-scale errors in the models. On the other hand, long-wave ridges tended to be underforecast (negative errors, heights too low) over a much larger horizontal extent. These results are confirmed in a more systematic manner over the entire dataset by segregating the model output at each grid point by the sign of the 500-hPa relative vorticity. Although errors at grid points with positive relative vorticity are small but positive in the western United States, the errors become large and negative farther east. Errors at grid points with negative relative vorticity, on the other hand, are generally negative across the United States. A large negative bias observed in the Eta and EtaKF over the southeast United States is believed to be due to an error in the longwave radiation scheme interacting with water vapor and clouds. This study shows that model errors may be related to the synoptic-scale flow, and even large-scale features such as long-wave troughs can be associated with significant large-scale height errors. © 2006 American Meteorological Society."
"7102963655;7003543851;","Does convectively-detrained cloud ice enhance water vapor feedback?",2006,"10.1029/2006GL027260","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845666570&doi=10.1029%2f2006GL027260&partnerID=40&md5=1d28ea6a51a80cb2314266765b0ea4f1","We demonstrate that coupled Global Climate Models (GCMs) can reproduce observed correlations among ice water path (IWP), upper tropospheric water vapor (UTWV), and sea surface temperature (SST), and that the presence/strength of this correlation has no direct bearing on the strength of water vapor feedback in the model. The models can accurately reproduce a strong positive correlation between IWP and UTWV, a rapid increase of IWP with increasing SST and a 2-3 times increase in the slope of UTWV versus SST for SSTs warmer than ∼300 K. We argue that the relative concentrations of IWP to UTWV in both observations and models is too small to significantly influence the observed moistening of the upper troposphere (UT). Copyright 2006 by the American Geophysical Union."
"15726335100;6602806333;7003861526;","Cloud property retrievals for climate monitoring: Implications of differences between Spinning Enhanced Visible and Infrared Imager (SEVIRI) on METEOSAT-8 and Advanced Very High Resolution Radiometer (AVHRR) on NOAA-17",2006,"10.1029/2005JD006990","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845652607&doi=10.1029%2f2005JD006990&partnerID=40&md5=1ac049ccdf49bdf6836182c7f0f621a2","In the framework of the Satellite Application Facility on Climate Monitoring (CM-SAF) an algorithm was developed to retrieve Cloud Physical Properties (CPP) from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board the Meteosat Second Generation (METEOSAT-8) and the Advanced Very High Resolution Radiometer (AVHRR) on board the National Oceanic and Atmospheric Administration (NOAA) satellites. This paper presents the CPP algorithm and determines if SEVIRI can be used together with AVHRR to build a consistent and accurate data set of cloud optical thickness (COT) and cloud liquid water path (CLWP) over Europe for climate research purposes. After quantifying the differences in 0.6 and 1.6 μm operational calibrated reflectances of SEVIRI and AVHRR, a recalibration procedure is proposed to normalize and absolutely calibrate these reflectances. The effects of recalibration, spatial resolution, and viewing geometry differences on the SEVIRI and AVHRR cloud property retrievals are evaluated. The intercomparison of 0.6 and 1.6 μm operationally calibrated reflectances indicates ∼6 and ∼26% higher reflectances for SEVIRI than for AVHRR. These discrepancies result in retrieval differences between AVHRR and SEVIRI of ∼8% for COT and ∼60% for CLWP. Owing to recalibration these differences reduce to ∼5%, while the magnitude of the median COT and CLWP values of AVHRR decrease ∼2 and ∼60% and the SEVIRI values increase ∼10 and ∼55%, respectively. The differences in spatial resolution and viewing geometry slightly influence the retrieval precision. Thus the CPP algorithm can be used to build a consistent and high-quality data set of SEVIRI and AVHRR retrieved cloud properties for climate research purposes, provided the instrument reflectances are recalibrated, preferably guided by the satellite operators. Copyright 2006 by the American Geophysical Union."
"57196817178;13406672500;","Abrupt transition from natural to anthropogenic aerosol radiative forcing: Observations at the ABC-Maldives Climate Observatory",2006,"10.1029/2006JD007063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845655955&doi=10.1029%2f2006JD007063&partnerID=40&md5=3ab06207f31779b0b1d53eb4732e8c14","Using aerosol-radiation observations over the north Indian Ocean, we show how the monsoon transition from southwest to northeast flow gives rise to a similar transition in the direct aerosol radiative forcing from natural to anthropogenic forcing. These observations were taken at the newly built aerosol-radiation-climate observatory at the island of Hanimaadhoo (6.776°N, 73.183°E) in the Republic of Maldives. This observatory is established as a part of Project Atmospheric Brown Clouds (ABC) and is referred to as the ABC-Maldives Climate Observatory at Hanimaadhoo (ABC_MCOH). The transition from the southwest monsoon during October to the northeast monsoon flow during early November occurs abruptly over a period of few weeks over ABC-MCOH and reveals a dramatic contrast between the natural marine aerosols transported from the south Indian Ocean by the southwest monsoon and that of the polluted aerosols transported from the south and Southeast Asian region by the northeast monsoon. We document the change in the microphysical properties and the irradiance at the surface, to identify the human signature on aerosol radiative forcing. We first establish the precision of surface radiometric observations by comparing simultaneous observations using calibrated Kipp & Zonen and Eppley pyrheliometers and pyranometers for direct, diffuse and global solar radiation. We show that the direct, diffuse and global radiation can be measured within a precision of about 3 to 5 Wm-2. Furthermore, when we include the observed aerosol optical properties as input into the Monte Carlo Aerosol Cloud Radiation (MACR) model (developed by us using Indian Ocean Experiment data), the simulated fluxes agree with the observed direct, diffuse and global fluxes within the measurement accuracy. A steady southwest monsoon flow of about 5 to 7 ms-1 persists until middle of October which switches to an abrupt change in direction to northeast flow of similar speeds bringing in polluted air from south Asia. However, it is not until end of November that a steady northeasterly flow is well established. The abrupt transition is accompanied by a large increase in aerosol optical depth from about 0.1 in October to as high as 0.4 during January, the SSA decreases from 1 to about 0.9, and the Angstrom coefficient increases from about 0.5 (suggesting large particles > 1 micron) to about 1.2 in January (submicron particles) and an increase in aerosol extinction below 3 km altitude. These changes are consistent with the transport of continental pollution from south and Southeast Asia (about 1000 to several 1000 km away from ABC_MCOH) to the north Indian Ocean during the northeast monsoon. The direct aerosol forcing, determined solely from radiometric observations without resorting to models, changes from -5 Wm-2 during October to -22 Wm-2 during January. About 50% of this forcing occurs in the photosynthetically active part of the solar spectrum (0.4 to 0.7 micron). MACR shows that the decrease in SSA from 1 to 0.9 changes the aerosol forcing efficiency by a factor of about 2 from about -40 Wm-2 (per AOD) in October to -80 Wm-2 (per AOD) in January. Thus the arrival of the brown clouds from south and Southeast Asia has a large seasonal dimming effect over remote parts of the north Indian Ocean. The observational results presented here should be used for validating climate models that attempt to simulate the anthropogenic effects of aerosol forcing on climate. The observational and model results presented in this study shows how near continuous surface based observations can be used to differentiate the human impact on aerosol forcing which is a major challenge for models. Copyright 2006 by the American Geophysical Union."
"56097010700;7403577184;35453054300;7004114883;","Effects of biomass-burning-derived aerosols on precipitations and clouds in the Amazon Basin: A satellite-based empirical study",2006,"10.1029/2005JD006884","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845520002&doi=10.1029%2f2005JD006884&partnerID=40&md5=7e024846398930d5922ea6e6a6f45dd2","Biomass burning in the Amazon provides strong input of aerosols into the atmosphere, with potential effects on precipitation, cloud properties, and radiative balance. However, few studies to date have systematically examined these effects at the scale of the Amazon Basin, over an entire burning season, using available data gets. We empirically study the relationships of aerosol optical depth (τ<inf>a</inf>) versus rainfall and cloud properties measured from satellites over the entire Brazilian Amazon during the dry, biomass burning seasons (August-October) of 2000 and 2003. Elevated τ<inf>a</inf> was associated with increased rainfall in both 2000 and 2003. With enhanced τ<inf>a</inf>, cloud cover increased significantly, and cloud top temperaturd/pressure decreased, suggesting higher cloud tops. The cloud droplet effective radius (R<inf>e</inf>) exhibited minimal growth with cloud height under background levels of τ<inf>a</inf>, while distinct increases in R<inf>e</inf> at cloud top temperatures below -10°C, indicative of ice formation, were observed with aerosol loading. Although empirical correlations do not unequivocally establish the causal link from aerosols, these results are consistent with. previous observational and modeling studies that pointed to dynamical effects from aerosols that invigorate convection, leading to higher clouds, enhanced cloud cover, and stronger rainfall. We speculate that changes in precipitation and cloud properties associated with aerosol loading observed in this study could have important radiative and hydrological effects on the Amazonian climate system. The accelerated forest burning for agricultural land clearing and the resulting enhancements in aerosols and rainfall may even partially account for the observed positive trend in Amazonian precipitation over the past several decades. Copyright 2006 by the American Geophysical Union."
"10640192200;6603054636;7004570901;57193157754;9235235300;7005755464;7007039218;7003984086;35461255500;","Condensation of water vapor: Experimental determination of mass and thermal accommodation coefficients",2006,"10.1029/2006JD007194","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547999031&doi=10.1029%2f2006JD007194&partnerID=40&md5=cb28917bb14be887151ad57a7ed75a84","Experimental determinations of mass and thermal accommodation coefficients α<inf>m</inf> and α<inf>t</inf> for condensation of water vapor in air have been conducted covering a temperature range from about 250 to 290 K. For the first time, both coefficients have been determined directly and simultaneously. To this end, growth of water droplets in air has been observed at different total gas pressures ranging from about 1000 down to 100 hPa. Monodispersed seed particles have been used as condensation nuclei. After addition of water vapor with well-defined partial vapor pressure, supersaturation was achieved by adiabatic expansion in an expansion chamber. Most experiments reported in the present paper were performed at vapor saturation ratios ranging from 1.30 to 1.50. Monodispersed Ag particles with a diameter of 9 nm have been used as condensation nuclei, and for humidification a diffusion humidifier was applied. One experiment was performed at the saturation ratio of 1.02, which resembles conditions observed in the Earth's lower atmosphere. In this experiment, monodispersed DEHS particles with a diameter of 80 nm were used as condensation nuclei, and water vapor was generated by quantitative evaporation of a liquid jet. Droplet growth was monitored using the CAMS method. For determination of the accommodation coefficients, experimental droplet growth curves were compared to corresponding theoretical curves. Quantitative comparison was performed by varying the respective accommodation coefficient and the starting time of droplet growth in a two-parameter best fit procedure. Considering the uncertainty with respect to the starting time of droplet growth and the uncertainties of the experimental water vapor supersaturation, corresponding maximum errors have been determined. From the results obtained it can be stated that α<inf>t</inf>, is larger than 0.85 over the whole considered temperature range. For 250-270 K, values of α<inf>m</inf>, below 0.8 are excluded, and for higher temperatures up to 290 K we can exclude values of α<inf>m</inf>, below 0.4. Both coefficients are likely to be unity for all studied conditions. The results of this study enable accurate predictions of the formation and growth of cloud droplets required to parameterize cloud light scattering/absorption and precipitation properties in climate models. Copyright 2006 by the American Geophysical Union."
"18935790900;6603623117;57194493209;","Isotopic composition of the precipitations in the central mediterranean: Origin marks and orographic precipitation effects",2006,"10.1029/2005JD006818","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547966896&doi=10.1029%2f2005JD006818&partnerID=40&md5=db46899803fab35696ef87578f4828e7","The isotopic composition of the rainfall in northwestern Sicily (Italy, central Mediterranean) was investigated in the period February 2002 to March 2003. A rain gauge network was installed and sampled monthly. The monthly values of the D and 18O ratios showed a wide range that reflected seasonal climatic variations. Mean weighted values were used to define an isotopic model of precipitation. Temporal variations in deuterium excess were also investigated. Using mean volume weighted values, the Local Meteoric Water Line (LMWL) can be represented by the equation: δD = 4.7δ18O - 8.2 (r2 = 0.96). Deuterium excess (d = δD - 8δ18O) was found to be strongly related to orography. The coastline samples were characterized by mean weighted deuterium excess values close to 12.5‰ samples from inland areas showed values of 169‰, while samples taken from the main reliefs showed values close to 19%· In inland areas, isotopic exchange between raindrops and moisture could shift the deuterium excess values slightly. On the higher reliefs, the interaction between falling raindrops and orographic clouds could shift the deuterium excess values significantly. The low slope of the LMWL could be referred to the high deuterium excess values of the higher sites and is related to orographic precipitation rather than to evaporation processes during the fall of the raindrops. The results obtained suggest that local orographic features may significantly change the isotopic composition of precipitation. Copyright 2006 by the American Geophysical Union."
"7004893330;57193132723;57191598636;","Observational constraints on the cloud thermodynamic phase in midlatitude storms",2006,"10.1175/JCLI3919.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750803493&doi=10.1175%2fJCLI3919.1&partnerID=40&md5=464f7ae57a7226d515ea3f43206b206e","The conditions under which supercooled liquid water gradually gives way to ice in the mixed-phase regions of clouds are still poorly understood and may be an important source of cloud feedback uncertainty in general circulation model projections of long-term climate change. Two winters of cloud phase discrimination, cloud-top temperature, sea surface temperature, and precipitation from several satellite datasets (the NASA Terra and Aqua Moderate Resolution Imaging Spectroradiometer, and the Tropical Rainfall Measuring Mission) for the North Atlantic and Pacific Ocean basins are analyzed to better understand these processes. Reanalysis surface pressures and vertical velocities are used in combination with a synoptic storm-tracking algorithm to define storm tracks, create composite storm dynamical and cloud patterns, and examine changes in storm characteristics over their life cycles. Characteristically different storm cloud patterns exist in the Atlantic and Pacific and on the west and east sides of each ocean basin. This appears to be related to the different spatial patterns of sea surface temperature in the two ocean basins. Glaciation occurs at very warm temperatures in the high, thick, heavily precipitating clouds typical of frontal ascent regions, except where vertical velocities are strongest, similar to previous field experiments. Outside frontal regions, however, where clouds are shallower, supercooled water exists at lower cloud-top temperatures. This analysis is the first large-scale assessment of cloud phase and its relation to dynamics on climatologically representative time scales. It provides a potentially powerful benchmark for the design and evaluation of mixed-phase process parameterizations in general circulation models and suggests that assumptions made in some existing models may negatively bias their cloud feedback estimates."
"24331052400;7005784518;","Integration of weather system variability to multidecadal regional climate change: The West African Sudan-Sahel zone, 1951-98",2006,"10.1175/JCLI4020.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750812762&doi=10.1175%2fJCLI4020.1&partnerID=40&md5=6f20cb1ffc8f4267c05d0b984ca2e90f","Since the late 1960s, the West African Sudan-Sahel zone (10°-18°N) has experienced persistent and often severe drought, which is among the most undisputed and largest regional climate changes in the last half-century. Previous documentation of the drought generally has used monthly, seasonal, and annual rainfall totals and departures, in a standard ""climate"" approach that overlooks the underlying weather system variability. Most Sudan-Sahel rainfall occurs during June-September and is delivered by westward-propagating, linear-type, mesoscale convective systems [disturbance lines (DLs)] that typically have much longer north-south (102-103 km) than east-west (10-102 km) dimensions. Here, a large set of daily rainfall data is analyzed to relate DL and regional climate variability on intraseasonal-to-multidecadal time scales for 1951-98. Rain gauge-based indices of DL frequency, size, and intensity are evaluated on a daily basis for four 440-km square ""catchments"" that extend across most of the West African Sudan-Sahel (18°W-4°E) and are then distilled into 1951-98 time series of 10-day and seasonal frequency/magnitude summary statistics. This approach is validated using Tropical Applications of Meteorology Using Satellite Data (TAMSAT) satellite IR cold cloud duration statistics for the same 1995-98 DLs. Results obtained for all four catchments are remarkably similar on each time scale. Long-term (1951-98) average DL size/organization increases monotonically from early June to late August and then decreases strongly during September. In contrast, average DL intensity maximizes 10-30 days earlier than DL size/organization and is distributed more symmetrically within the rainy season for all catchments except the westernmost, where DL intensity tracks DL size/organization very closely. Intraseasonal and interannual DL variability is documented using sets of very deficient (8) and much more abundant (7) rainy seasons during 1951-98. The predominant mode of rainfall extremes involves near-season-long suppression or enhancement of the seasonal cycles of DL size/ organization and intensity, especially during the late July-late August rainy season peak. Other extreme seasons result solely from peak season anomalies. On the multidecadal scale, the dramatic decline in seasonal rainfall totals from the early 1950s to the mid-1980s is shown to result from pronounced downtrends in DL size/organization and intensity. Surprisingly, this DL shrinking-fragmentation-weakening is not accompanied by increases in catchment rainless days (i.e., total DL absence). Like the seasonal rainfall totals, DL size/organization and intensity increase slightly after the mid-1980s. © 2006 American Meteorological Society."
"14825023600;7005734412;14825178100;","Assessing daytime downward longwave radiation estimates for clear and cloudy skies in Southern Brazil",2006,"10.1016/j.agrformet.2006.06.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749346979&doi=10.1016%2fj.agrformet.2006.06.008&partnerID=40&md5=f52baf7c963d3f75f2346368a1562d04","Several well-known parameterisations for clear-sky and cloudy-sky downward longwave radiation were tested for an experimental site at Ponta Grossa (Paraná State, Brazil) where all radiation components and meteorological data were measured during 279 days in spring, summer, fall and winter (2003/2004). The existing clear-sky parameterisations usually overestimate the measured values, whereas the cloudy-sky formulations underestimate measurements. Best results for clear-sky downward longwave radiation were obtained with Brutsaert's [Brutsaert, W.H., 1975. On a derivable formula for long-wave radiation from clear skies. Water Resour. Res. 11 (5), 742-744] formulation. Jacobs' [Jacobs, J.D., 1978. Radiation climate of Broughton Island. in: Barry, R.G., Jacobs, J.D. (Eds.), Energy budget studies in relation to fast-ice breakup processes in Davis Strait. Inst. of Arctic and Alp. Res. Occas. Paper No. 26. University of Colorado, Boulder, CO, pp. 105-120] and Crawford and Duchon's [Crawford, T.M., Duchon, C.E., 1999. An improved parameterization for estimating effective atmospheric emissivity for use in calculating daytime downwelling longwave radiation. J. Appl. Meteorol. 38, 474-480] equations gave the best results for cloudy skies. The parameterisations that generated the best fits were further locally calibrated, providing a useful tool for applications requiring downward longwave radiation estimates in Southern Brazil. No significant differences between spring/summer and autumn/winter were found for the coefficients of the Brutsaert's clear-sky parameterisation, whereas some seasonality may be present in Jacobs' cloudy-sky parameterisation. For practical purposes, however, little is gained in error reduction, and it is sufficient to use year-round calibrated coefficients. © 2006 Elsevier B.V. All rights reserved."
"7401796996;8629713500;7006783796;","Observational evidence of changes in water vapor, clouds, and radiation at the ARM SGP site",2006,"10.1029/2006GL027132","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34047223154&doi=10.1029%2f2006GL027132&partnerID=40&md5=b0692c9b3b3ec3678d5a025c876c2509","Characterizing water vapor and cloud effects on the surface radiation budget is critical for understanding the current climate because water vapor is the most important greenhouse gas in the atmosphere and clouds are one of the largest sources of uncertainty in predicting potential future climate change. Several studies have shown that insolation over land declined until 1990 then increased until the present. Using 8 years of data collected at the ARM Southern Great Plains (SGP) surface site, we found that the insolation increased from 1997 to 2000, but significantly decreased from 2001 to 2004, changes that exactly mirror the variation in the second-order fit of cloud fraction. Under clear-sky conditions, the rates of change of water vapor, insolation and downwelling longwave (LW) flux are -0.0166 cm/yr, 0.48 Wm-2/yr, and -1.16 Wm-2/yr, respectively, indicating that water vapor changes are more important for LW flux than for insolation. Copyright 2006 by the American Geophysical Union."
"6506837510;7007108728;","Bulk microphysics parametrization of ice fraction for application in climate models",2006,"10.1256/qj.05.04","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751511477&doi=10.1256%2fqj.05.04&partnerID=40&md5=d856d22990b251110ae40c1b8c54842b","Using in situ aircraft measurements of cloud microphysical properties collected in extratropical stratiform clouds during several field programs, a parametrization of the ice-particle spectrum that includes small ice particles has been developed. This parametrization has been tested using a single prognostic equation developed by Tremblay et al. (1996) for application in a regional model. The addition of small ice-particles significantly increases the vapour deposition-rate when the natural atmosphere is assumed to be water saturated, and thus enhances the glaciation of simulated mixed-phase cloud via the Bergeron-Findeisen process without significantly affecting the other cloud microphysical processes such as riming and particle-sedimentation rates. After the water vapour pressure in mixed-phase cloud was modified, based on the scheme of Lord et al. (1984), by weighting the saturation water vapour pressure with ice fraction, it was possible to simulate a more stable mixed-phase cloud. It was also noted that the ice-particle concentration (maximum dimension L > 100 μm) in mixed-phase cloud is lower on average by a factor of three, and, consequently, the parametrization should be corrected for this effect. After accounting for this effect, the parametrized ice-fraction agreed well with observation. © Royal Meteorological Society, 2006."
"7005692186;7403254320;6602484429;7005413462;","Historical instrumental climate data for Australia - Quality and utility for palaeoclimatic studies",2006,"10.1002/jqs.1054","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750382079&doi=10.1002%2fjqs.1054&partnerID=40&md5=43300ba7befb10d7fbcd9a42880ec086","The quality and availability of climate data suitable for palaeoclimatic calibration and verification for the Australian region are discussed and documented. Details of the various datasets, including problems with the data, are presented. High-quality datasets, where such problems are reduced or even eliminated, are discussed. Many climate datasets are now analysed onto grids, facilitating the preparation of regional-average time series. Work is under way to produce such high-quality, gridded datasets for a variety of hitherto unavailable climate data, including surface humidity, pan evaporation, wind, and cloud. An experiment suggests that only a relatively small number of palaeoclimatic time series could provide a useful estimate of long-term changes in Australian annual average temperature. Copyright © 2006 John Wiley & Sons, Ltd."
"56493740900;7004364155;7006783796;7201706787;6701859365;55942502100;7006204393;6506827279;","Seasonal and interannual variations of top-of-atmosphere irradiance and cloud cover over polar regions derived from the CERES data set",2006,"10.1029/2006GL026685","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34047202437&doi=10.1029%2f2006GL026685&partnerID=40&md5=d85f4e9de05f75663fb334d4612fc7c0","The daytime cloud fraction derived by the Clouds and the Earth's Radiant Energy System (CERES) cloud algorithm using Moderate Resolution Imaging Spectroradiometer (MODIS) radiances over the Arctic from March 2000 through February 2004 increases at a rate of 0.047 per decade. The trend is significant at an 80% confidence level. The corresponding top-of-atmosphere (TOA) shortwave irradiances derived from CERES radiance measurements show less significant trend during this period. These results suggest that the influence of reduced Arctic sea ice cover on TOA reflected shortwave radiation is reduced by the presence of clouds and possibly compensated by the increase in cloud cover. The cloud fraction and TOA reflected shortwave irradiance over the Antarctic show no significant trend during the same period. Copyright 2006 by the American Geophysical Union."
"7101752236;7103271625;","Cloud microphysics, radiation and vertical velocities in two- and three-dimensional simulations of deep convection",2006,"10.1256/qj.05.171","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38349147886&doi=10.1256%2fqj.05.171&partnerID=40&md5=265b0ea7bf8db6f2bd514d69af3c4eeb","This study investigates the importance of dimensionality for the characteristics of simulations performed with cloud-system resolving models (CSRMs). In addition to intrinsic questions related to dimensionality in CSRMs, the issue has gained added interest since CSRMs can be utilized instead of conventional cloud parametrizations to represent deep convection within global climate models. Such CSRMs may be either two- or three-dimensional. CSRM simulations of five observed cases of deep convection are performed in both two and three dimensions (2D and 3D) with the aim of elucidating the impact of dimensionality on overall cloud statistics. Observed profiles of the large-scale average of advection of temperature and humidity are applied to initiate and maintain the convection. Two of the cases are from tropical oceanic regions. The other three cases are continental. The average ascent rate in deep convective, cloudy updraughts is about 20-50% higher at mid-levels of the troposphere in 3D than in 2D, for all cases. This corresponds to an increase by a similar percentage in the vertical mass flux of deep updraughts in the oceanic cases. Furthermore, the weak ascent (0.1 &lt; w &lt; 1 m s-1) outside the deep convective updraughts is much less prevalent in 3D than in 2D, with vertical velocities being about 20% lower for a given cumulative frequency and a lower vertical mass flux. Downdraughts are weaker in 3D, for most cases. There is a substantial sensitivity of the vertical profiles of cloud liquid and cloud ice, and of other microphysical species, to dimensionality. This is consistent with the sensitivity of the dynamics of convection. Corresponding changes in radiative transfer, especially in the short-wave band, result from the cloud-radiative interactions. In particular, the peak in domain-averaged cloud liquid content in the melting layer is about 50% higher in most of the 2D simulations. The land cases display more sensitivity of the short-wave radiative flux to the choice of orientation of the vertical plane of 2D simulations. © Royal Meteorological Society, 2006."
"7103100397;35783045500;","Microclimatic factors associated with elevational changes in army ant density in tropical montane forest",2006,"10.1111/j.1365-2311.2006.00805.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748630262&doi=10.1111%2fj.1365-2311.2006.00805.x&partnerID=40&md5=4291c138cb58df5ac10553e2b27600e3","1. The density (rate of encountering foraging raids) and species richness of army ants (Formicidae: Ecitoninae, and behaviourally convergent Ponerinae) was measured in montane tropical forest. Above-ground and subterranean army ant raids were sampled using standard protocols at four sites across an elevational gradient (1200-1650 m above mean sea level) in and near cloud forest in the area of Monteverde, Costa Rica. 2. Mean ambient temperature differed among sites, and decreased with elevation. For the above-ground foraging army ant species, raid rates also declined with elevation. Surface army ant raid rates, however, were not affected by day to day weather variation within sites (temperature, cloud cover, or precipitation). 3. For the underground foraging army ant species, raid rates did not vary directionally with elevation, and subterranean raid rates were not affected by day to day weather variation within sites. 4. Army ant species richness was not directionally related to elevation, and species sharing among sites was generally high. 5. Army ant community structure changes with elevation in Neotropical montane forest, and the results suggest that the strongest effects are of temperature regimes on the density of raids. These findings provide a baseline against which to detect changes in army ant communities that may accompany directional climate change in tropical cloud forests. © 2006 The Authors."
"7003627515;6602598448;6602506180;36928248800;","Daily cycle of the surface energy balance in Antarctica and the influence of clouds",2006,"10.1002/joc.1323","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750306138&doi=10.1002%2fjoc.1323&partnerID=40&md5=cd329119a754405ca3bb51fe9098d5a9","We present the summertime daily cycle of the Antarctic surface energy balance (SEB) and its sensitivity to cloud cover. We use data of automatic weather stations (AWS) located in four major Antarctic climate zones: the coastal ice shelf, the coastal and interior katabatic wind zone and the interior plateau. Absorbed short wave radiation drives the daily cycle of the SEB, in spite of the high surface albedo (0.84-0.88). The dominant heat sink is the cooling by long wave radiation, but this flux is distributed more evenly throughout the day so that a pronounced daily cycle in net all-wave radiation remains with all-sky night-time heat losses of 20-30 W m-2 and noontime heat gains of 30-40 W m-2. During the night, heat is re-supplied to the snow surface by the sensible heat flux, especially in the katabatic wind zone, and the sub-surface heat flux. Daytime radiative energy excess is removed from the surface by sublimation (except at the high plateau) and sub-surface heat transport. Daytime convection occurs at all sites around solar noon but is generally weak. Spatial differences in the SEB are largely controlled by differences in cloud cover. Clouds are associated with higher surface temperatures and near-surface wind speeds. This especially limits nocturnal cooling, so that the strongest daytime convection is found during overcast conditions on the interior plateau. Copyright © 2006 Royal Meteorological Society."
"57203078745;7003440089;7801416679;6602472532;","The 1988-2003 Greenland ice sheet melt extent using passive microwave satellite data and a regional climate model",2006,"10.1007/s00382-006-0150-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33747511122&doi=10.1007%2fs00382-006-0150-8&partnerID=40&md5=a8a3ad737f6f0612d5790d9dd555a915","Measurements from ETH-Camp and JAR1 AWS (West Greenland) as well as coupled atmosphere-snow regional climate simulations have highlighted flaws in the cross-polarized gradient ratio (XPGR) technique used to identify melt from passive microwave satellite data. It was found that dense clouds (causing notably rainfall) on the ice sheet severely perturb the XPGR melt signal. Therefore, the original XPGR melt detection algorithm has been adapted to better incorporate atmospheric variability over the ice sheet and an updated melt trend for the 1988-2003 period has been calculated. Compared to the original algorithm, the melt zone area increase is eight times higher (from 0.2 to 1.7% year-1). The increase is higher with the improved XPGR technique because rainfall also increased during this period. It is correlated to higher atmospheric temperatures. Finally, the model shows that the total ice sheet runoff is directly proportional to the melt extent surface detected by satellites. These results are important for the understanding of the effect of Greenland melting on the stability of the thermohaline circulation. © Springer-Verlag 2006."
"9638398100;7101787483;","Urban lightning climatology and GIS: An analytical framework from the case study of Atlanta, Georgia",2006,"10.1016/j.apgeog.2006.09.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751190322&doi=10.1016%2fj.apgeog.2006.09.008&partnerID=40&md5=ff72d2608be59722837c2e68c5b5753e","There are three underdeveloped components of urban cloud-to-ground lightning studies: (1) the integration of multiple flash descriptors into more informative summary metrics of flash production, (2) the comparison of flash patterns by thunderstorm type, and (3) the correspondence of urban flashes with underlying land use. We used a GIS to integrate these components as part of an analysis of warm season (May-September) flashes for Atlanta, Georgia, a sprawling region in the thunderstorm-prone southeastern US. Our integrated metric of flash counts and flash days demarcated two large contiguous areas of high flash production in northeast Atlanta. Flashes which developed under conditions related to local surface heating and air mass instability more closely corresponded to urban land uses. Frontally-produced lightning was infrequent over the central city. Instead, peaks in production shifted to the periphery of the urban core, an observation suggestive of building barrier effects. © 2006 Elsevier Ltd. All rights reserved."
"57200530823;25227357000;7102018821;","The impact of direct aerosol radiative forcing on surface insolation and spring snowmelt in the southern Sierra Nevada",2006,"10.1175/JHM541.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750960804&doi=10.1175%2fJHM541.1&partnerID=40&md5=ec5a2f4715b2a3c0efb7d465ca56078c","To understand the regional impact of the atmospheric aerosols on the surface energy and water cycle in the southern Sierra Nevada characterized by extreme variations in terrain elevation, the authors examine the aerosol radiative forcing on surface insolation and snowmelt for the spring of 1998 in a regional climate model experiment. With a prescribed aerosol optical thickness of 0.2, it is found that direct aerosol radiative forcing influences spring snowmelt primarily by reducing surface insolation and that these forcings on surface insolation and snowmelt vary strongly following terrain elevation. The direct aerosol radiative forcing on surface insolation is negative in all elevations. It is nearly uniform in the regions below 2000 m and decreases with increasing elevation in the region above 2000 m. This elevation dependency in the direct aerosol radiative forcing on surface insolation is related to the fact that the amount of cloud water and the frequency of cloud formation are nearly uniform in the lower elevation region, but increase with increasing elevation in the higher elevation region. This also suggests that clouds can effectively mask the direct aerosol radiative forcing on surface insolation. The direct aerosol radiative forcing on snowmelt is notable only in the regions above 2000 m and is primarily via the reduction in the surface insolation by aerosols. The effect of this forcing on low-level air temperature is as large as -0.3°C, but its impact on snowmelt is small because the sensible heat flux change is much smaller than the insolation change. The direct aerosol radiative forcing on snowmelt is significant only when low-level temperature is near the freezing point, between -3° and 5°C. When low-level temperature is outside this range, the direct aerosol radiative forcing on surface insolation has only a weak influence on snowmelt. The elevation dependency of the direct aerosol radiative forcing on snowmelt is related with this low-level temperature effect as the occurrence of the favored temperature range is most frequent in high elevation regions. © 2006 American Meteorological Society."
"11840367400;11839001400;7003811919;55721431800;","Asian dust storm monitoring combining terra and aqua MODIS SRB measurements",2006,"10.1109/LGRS.2006.877752","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750594602&doi=10.1109%2fLGRS.2006.877752&partnerID=40&md5=970d320eb0c7a11a4cd4537989e046c6","Sand and dust storms (SDSs), which present environmental risks and affect the regional climate, have been worsened in the East Asian regions over the last decade. Monitoring SDS from space using satellite remote sensing (RS) has become one of the most important issues in this field. At present, satellite RS of SDS is limited to using true-color images or aerosol optical thickness (AOT), or a new algorithm called ""Deep Blue."" Using current existing approaches makes it difficult to identify SDS from clouds. The authors have detected SDS by combining Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) solar reflectance band (SRB) measurements. Based on the dust spectral characteristic, this letter proposes a normalized difference dust index (NDDI) using MODIS reflectance measurements and applies it to the Asian SDS cases. The simple NDDI index is found to be able to identify SDS and clouds easily. The results suggest that NDDI could be used to detect SDS over bright surfaces where the MODIS AOT product is not available. © 2006 IEEE."
"6506944086;6603123442;9740124600;6701900493;","Palynology of the Paleogene Cuayuca Formation (stratotype sections), southern Mexico: Chronostratigraphical and palaeoecological implications",2006,"10.1016/j.revpalbo.2006.04.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748490679&doi=10.1016%2fj.revpalbo.2006.04.006&partnerID=40&md5=0d1ea82203f7f8baf3ef8fb199e0437c","Palynological markers such as Aglaoreidia pristina, Armeria, Bombacacidites, Corsinipollenites, Ephedripites claricristatus, Eucommia, Favitricolporites, Intratriporopollenites, Lymingtonia, Magnaperiporites, Malvacipollis spinulosa, Margocolporites vanwijhei, Momipites tenuipolus, Polyadopollenites aff. pflugii, and Thomsonipollis sabinetownensis recovered from the Cuayuca Formation permit it to be assigned a late Eocene-early Oligocene age. The evaporitic horizons of the Cuayuca Formation were deposited in a continental basin located south of Mexico City. The palynological assemblages indicate temperate-humid to dryer climates. The Cuayuca Formation was probably deposited in a shallow lacustrine basin under local xeric conditions with a semiarid climate that allowed the development of grassland (with Chenopodiaceae-Amaranthaceae, Gramineae, and Ephedra) and thorn shrub community (with Acacia, Leguminosae, Linum, and Plumbaginaceae). The neighboring communities were probably chaparral, tropical deciduous forest, low tropical deciduous forest, and thorn forest. In addition, there was regional temperate vegetation like Pinus forest and cloud forest. © 2006 Elsevier B.V. All rights reserved."
"14828591400;7004640724;6701361414;","Early Holocene water budget of the Nakuru-Elmenteita basin, Central Kenya Rift",2006,"10.1007/s10933-006-9003-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749473170&doi=10.1007%2fs10933-006-9003-z&partnerID=40&md5=9f91e01c05b0e5144d36029ed0ed914e","The Nakuru-Elmenteita basin in the Central Kenya Rift, contains two shallow, alkaline lakes, Lake Nakuru (1770 m above sea level) and Lake Elmenteita (1786 m). Ancient shorelines and lake sediments at 1940 m suggest that these two lakes formed a single large and deep lake as a result of a wetter climate during the early Holocene. Here, we used a hydrological model to compare the precipitation-evaporation balance during the early Holocene to today. Assuming that the Nakuru-Elmenteita basin was hydrologically closed, as it is today, the most likely climate scenario includes a 45% increase in mean-annual precipitation, a 0.5°C decrease in air temperature, and an increase of 9% in cloud coverage from the modern values. Compared to the modeling results from other East African lake basins, this dramatic increase in precipitation seems to be unrealistic. Therefore, we propose a significant flow of water from the early Holocene Lake Naivasha in the south towards the Nakuru-Elmenteita basin to compensate the extremely negative hydrological budget of this basin. Since we did not find any field evidence for a surface connection, as often proposed during the last 70 years, the hydrological deficit of the Nakuru-Elmenteita basin could have also been compensated by a subsurface water exchange. © 2006 Springer Science+Business Media, Inc."
"15049835500;7005821477;","A statistical procedure to forecast warm season lightning over portions of the Florida peninsula",2006,"10.1175/WAF954.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750506736&doi=10.1175%2fWAF954.1&partnerID=40&md5=da9539453e6657ef5fe5ae14b7f2098a","Sixteen years of cloud-to-ground lightning data from the National Lightning Detection Network and morning radiosonde-derived parameters are used to develop a statistical scheme to provide improved forecast guidance for warm season afternoon and evening lightning for 11 areas of the Florida peninsula serviced by Florida Power and Light Corporation (FPL). Logistic regression techniques are used to develop equations predicting whether at least one flash will occur during the noon-midnight period in each area, as well as the amount of lightning that can be expected during this same period, conditional on at least one flash occurring. For the amount of lightning, the best results are achieved by creating four quartile categories of flash count based on climatology, and then using three logistic equations and a decision tree approach to determine the most likely quartile. A combination of forward stepwise screening and cross validation are used to select the best combination of predictors that are most likely to generalize to independent data. Results show the guidance equations to be superior to persistence on both the dependent dataset and during cross validation. The greatest skill scores are achieved for predicting whether at least one flash will occur, as well as predicting the number of flashes to within one quartile of that observed. These results demonstrate that the equations possess forecast skill and will provide useful guidance for the probability and amount of lightning in each of the 11 FPL service areas. © 2006 American Meteorological Society."
"36934610300;7005231450;7005578774;6603901951;","Simulation of global land surface conditions from 1948 to 2004. Part I: Forcing data and evaluations",2006,"10.1175/JHM540.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750954695&doi=10.1175%2fJHM540.1&partnerID=40&md5=f28272396982aee9eebb014f6e9f64ca","Because of a lack of observations, historical simulations of land surface conditions using land surface models are needed for studying variability and changes in the continental water cycle and for providing initial conditions for seasonal climate predictions. Atmospheric forcing datasets are also needed for land surface model development. The quality of atmospheric forcing data greatly affects the ability of land surface models to realistically simulate land surface conditions. Here a carefully constructed global forcing dataset for 1948-2004 with 3-hourly and T62 (∼1.875°) resolution is described, and historical simulations using the latest version of the Community Land Model version 3.0 (CLM3) are evaluated using available observations of streamflow, continental freshwater discharge, surface runoff, and soil moisture. The forcing dataset was derived by combining observation-based analyses of monthly precipitation and surface air temperature with intramonthly variations from the National Centers for Environmental Prediction- National Center for Atmospheric Research (NCEP-NCAR) reanalysis, which is shown to have spurious trends and biases in surface temperature and precipitation. Surface downward solar radiation from the reanalysis was first adjusted for variations and trends using monthly station records of cloud cover anomaly and then for mean biases using satellite observations during recent decades. Surface specific humidity from the reanalysis was adjusted using the adjusted surface air temperature and reanalysis relative humidity. Surface wind speed and air pressure were interpolated directly from the 6-hourly reanalysis data. Sensitivity experiments show that the precipitation adjustment (to the reanalysis data) leads to the largest improvement, while the temperature and radiation adjustments have only small effects. When forced by this data set, the CLM3 reproduces many aspects of the long-term mean, annual cycle, interannual and decadal variations, and trends of streamflow for many large rivers (e.g., the Orinoco, Changjiang, Mississippi, etc.), although substantial biases exist. The simulated long-term-mean freshwater discharge into the global and individual oceans is comparable to 921 river-based observational estimates. Observed soil moisture variations over Illinois and parts of Eurasia are generally simulated well, with the dominant influence coming from precipitation. The results suggest that the CLM3 simulations are useful for climate change analysis. It is also shown that unrealistically low intensity and high frequency of precipitation, as in most model-simulated precipitation or observed time-averaged fields, result in too much evaporation and too little runoff, which leads to lower than observed river flows. This problem can be reduced by adjusting the precipitation rates using observed-precipitation frequency maps. © 2006 American Meteorological Society."
"8875548400;12806862100;57203053317;6701567154;7006593624;7003329635;6602504147;6603747326;56140087300;6506643480;","Characterization of the aerosol over the sub-arctic north east Pacific Ocean",2006,"10.1016/j.dsr2.2006.05.044","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751170473&doi=10.1016%2fj.dsr2.2006.05.044&partnerID=40&md5=02963214d364971289fba605838badd7","Time series measurements of the size and composition of aerosol particles made near Ocean Station Papa during the Canadian SOLAS SERIES experiment in July 2002 indicate major contributions to the aerosol mass from the oxidation of dimethyl sulphide, from primary emissions of sea salt, and from ship emissions. The high temporal resolution of the AMS revealed significant variability in the fine mode species mass concentrations in this area. The background fine mode composition was dominated by non-sea-salt-sulphate (nss-SO4), sea salt, organics, and methanesulphonic acid (MSA), with average mass concentrations of 0.74±0.04, 0.6±0.1, 0.3±0.1, and 0.16±0.05 μg m-3, respectively. The fine mode MSA:nss-SO4 ratio varied from 0.01 to 3.19±0.2, with a mean of 0.23. The average fine mode mass distribution was internally mixed with a mode vacuum aerodynamic diameter of 475 nm. The concentration of MSA was an order of magnitude higher than previously reported values in the North Pacific, indicating significant oxidation of DMS. A diurnal signal in particulate products of DMS oxidation (i.e. MSA and sulphate) and in gaseous DMS and SO2 indicates daytime photochemistry and in-cloud oxidation. A simple examination of chemical reaction pathways is used to help elucidate the relationships among the sulphur species and oxidants. The relationship between sea salt mass and wind speed is examined. This study marks the first time atmospheric measurements have been included in an iron enrichment experiment, and the first time an Aerodyne Aerosol Mass Spectrometer (AMS) has been deployed in a remote marine setting. Due to the proximity of the ship to the fertilized patch and the relatively high wind speeds, no impact of the SERIES iron fertilization on the local aerosol was observed. © 2006 Elsevier Ltd. All rights reserved."
"15841350300;8670213100;55665366600;6507681572;7004639116;6603395511;6602137840;6701796418;","Spatial and temporal distribution of long-term short-wave surface radiation over Greece",2006,"10.1256/qj.05.163","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846892481&doi=10.1256%2fqj.05.163&partnerID=40&md5=003c3580cd6a154fc2bc93b18c59656f","The short-wave (SW) surface radiation budget (SRB, downward and absorbed fluxes) over Greece and surrounding areas has been computed for the first time, using a physical deterministic radiative-transfer model. The model computations were performed on a monthly-mean basis and at 2.5° × 2.5° latitude-longitude resolution over the 17-year period 1984-2000. Higher spatial resolution of 1° × 1° was achieved using the new NASA-Langley dataset but only for the shorter period 1985-1995. In the first case (2.5° × 2.5° resolution), the model input data were taken from global datasets, such as the International Satellite Cloud Climatology Project (ISCCP), the TIROS Operational Vertical Sounder (TOVS) or the Global Aerosol Dataset (GADS), as well as from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) and European Centre for Medium Range Weather Forecasts (ECMWF) Global Re-analysis Projects. In the second case (1° × 1° resolution), the model input data were taken from the NASA-Langley dataset supplemented by others (e.g., GADS). It is found that the annual mean values of the downward SW radiation at the surface (DSR) increase from about 150 W m-2 in the north of Greece to 210 W m-2 in the south. (Seasonal means are 50 and 100 W m-2, respectively, in the winter and 270 and 330 W m-2 in summer). The 1° × 1° DSR fluxes reveal significant geographical features, indicating an important longitudinal variation, with smaller values along the central mountain axis and in the northern part of the country. The annual mean DSR flux, averaged over the study area, is 181.9 ± 14.4 W m-2, calculated using the ISCCP-D2 (1984-2000) data or 188.8 ± 14.2 W m-2 using the NASA-Langley (1985-1995) data. The corresponding averaged mean surface absorbed fluxes are 164.7 ± 13.1 W m-2 and 170.7 ± 13.2 W m-2. Computed time series of annual mean solar radiation arriving at the surface, and a linear fit applied to them, show an increase with time which may possibly be related to climatic change. Time series of annual amplitude of DSR (maximum minus minimum monthly values) indicate a year-to-year variation of DSR of about 245 W m-2, whereas a linear fit shows an increase with time but no systematic increase in summer maxima or decrease in winter minima. The model-computed DSR fluxes are in good agreement with surface measurements, made at eight stations of the Hellenic National Meteorological Service and four other high-standard stations run by Greek research organizations, with correlation coefficients in the range 0.91-0.99 and standard deviations smaller than 20 W m-2. The ratio of direct to diffuse DSR (an indicator of clear skies) peaks during the summer months at a value of 1.5 in Thessaloniki (northern Greece), at about three in Athens and nine in Crete. © Royal Meteorological Society, 2006."
"56229328000;6603610616;","Simulation of surface energy fluxes using high-resolution non-hydrostatic simulations and comparisons with measurements for the LITFASS-2003 experiment",2006,"10.1007/s10546-006-9107-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750396402&doi=10.1007%2fs10546-006-9107-z&partnerID=40&md5=b7675cec012396497ff6a1354c691ebc","Land-surface heterogeneity effects on the subgrid scale of regional climate and numerical weather prediction models are of vital interest for the energy and mass exchange between the surface and the atmospheric boundary layer. High-resolution numerical model simulations can be used to quantify these effects, and are a tool used to obtain area-averaged surface fluxes over heterogeneous land surfaces. We present high-resolution model simulations for the LITFASS area near Berlin during the LITFASS-2003 experiment, which were carried out using the non-hydrostatic model FOOT3DK of the University of Köln with horizontal resolutions of 1 km and 250 m. The LITFASS-2003 experimental dataset is used for comparison. The screen level quantities show good quality for the simulated pressure, temperature, humidity and wind speed and direction. Averaged over the four week experimental period, simulated surface energy fluxes at land stations show a small bias for the turbulent heat fluxes and an underestimation of the net radiation caused by excessive cloudiness in the simulations. For eight selected days with low cloud amounts, the net radiation bias is close to zero, but the sensible heat flux shows a strong positive bias. Large differences are found for latent heat fluxes over a lake, which are partly due to local effects on the measurements, but an additional problem seems to be the overestimation of the turbulent exchange under stable conditions in the daytime internal boundary layer over the lake. In the area average over the LITFASS area of 20 × 20 km2, again a strong positive bias of 70 W m-2 for the sensible heat is present. For the low soil moisture conditions during June 2003, the simulation of the turbulent heat fluxes is sensitive to variations in the soil type and its hydrological properties. Under these conditions, the supply of ground water to the lowest soil layer should be accounted for. Different area-averaging methods are tested. The experimental set-up of the LITFASS-2003 experiment is found to be well suited for the computation of area-averaged turbulent heat fluxes. © Springer Science+Business Media B.V. 2006."
"6602665711;","Does the Last Glacial Maximum constrain climate sensitivity?",2006,"10.1029/2006GL027137","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846910933&doi=10.1029%2f2006GL027137&partnerID=40&md5=84b9aca25c7ecc054fc2e73478b28ee1","Four simulations with atmosphere-ocean climate models have been produced using identical Last Glacial Maximum ice sheets, topography and greenhouse gas concentrations. Compared to the pre-industrial, the diagnosed radiative feedback parameter ranges between -1.30 and -1.18 Wm-2 K-1, the tropical ocean sea-surface temperature decreases between 1.7 and 2.7°C, and Antarctic surface air temperature decreases by 7 to 11°C. These values are all compatible with observational estimates, except for a tendency to underestimate the tropical ocean cooling. On the other hand, the same models have a climate sensitivity to CO2 concentration doubling ranging between 2.1 and 3.9 K. It is therefore inappropriate to simply scale an observational estimate of LGM temperature to predict climate sensitivity. This is mainly a consequence of the non-linear character of the cloud (mainly shortwave) feedback at low latitudes. Changes in albedo and cloud cover at mid and high latitudes are also important, but less so."
"8909993500;55895104800;","Polar stratospheric ice cloud above Spitsbergen",2006,"10.1029/2005JD006967","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547694628&doi=10.1029%2f2005JD006967&partnerID=40&md5=0913bcc1a3df3f19d04fed395a43e049","Within the extremely cold and stable polar vortex of winter 2004-2005 a polar stratospheric ice cloud was observed from Ny-Ålesund (Spitsbergen) on 26 January 2005. The observation of a cloud with backscatter ratios up to 23 and volume depolarization larger than 50% is unique in our 15 year ground-based lidar data record. Simultaneous balloon-borne water vapor measurements indicate the presence of mesoscale ice clouds nearby. Normally, low horizontal wind speeds inside the inner vortex prevent vertical wave propagation. However, the rare coincidence of different meteorological processes occurring during a poleward-breaking Rossby wave event caused favorable conditions for the vertical propagation of mountain waves excited by the flow past Spitsbergen. Detailed meteorological analysis shows that the ice particle formation processes on 26 January 2005 were most likely provoked by mesoscale stratospheric temperature anomalies, leading to a local reduction in water vapor. Copyright 2006 by the American Geophysical Union."
"7102687667;55716406600;7404653593;","Weekend effect in diurnal temperature range in China: Opposite signals between winter and summer",2006,"10.1029/2006JD007068","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547766891&doi=10.1029%2f2006JD007068&partnerID=40&md5=e70bcf12eb781bacd51605976b8a7163","Intense human activity can impact weather and climate in many ways. One possible important consequence is the weekly cycle (so-called weekend effect) in the diurnal temperature range (DTR). The weekend effect is defined as the average DTR for Saturday through Monday minus the average DTR for Wednesday through Friday. In the present study, the weekend effect in the DTR over east China combined with station observations of maximum and minimum temperatures, relative humidity, and total solar irradiance for the period 1955-2000 was analyzed. Results show that the weekend effect in the DTR has the opposite signal between winter (December, January, and February) and summer (June, July, and August). Wintertime DTR tends to have a positive weekend effect (i.e., larger DTR in weekend days compared to weekdays), in association with increased maximum temperature and total irradiance but decreased relative humidity. While summertime DTR displays a much stronger and significantly negative weekend effect (i.e., smaller DTR in weekend days), in association with decreased maximum temperature and total solar irradiance but increased relative humidity and a greater number of rainy days. This study indicates that the DTR difference between weekend and weekdays is predominantly related to weekly changes in the maximum temperature. The weekend effect in the DTR and maximum temperature is also found in the Reanalysis 2 data. The weekend effect in winter is supported by an analogous holiday (Spring Festival) effect. Since the late 1970s, the weekend effect has been enhanced in both winter and summer, concurrent with rapid development and enhanced human activity in China. The direct and indirect effects of human-related aerosols on radiation, cloud, precipitation, and so on, might play an important role in generating the opposite signal in the weekend effect for different seasons. During a dry winter, the reduction of aerosol concentrations may overwhelmingly impact on the DTR through a direct effect, i.e., by increasing total solar irradiance near the surface and raising the daytime temperature and maximum temperature and lowering relative humidity. By contrast, in summer the indirect effect of aerosols, i.e., reduction in precipitation efficiency caused by more numerous and smaller cloud droplets, would largely be responsible for the increased numbers of rainy days, the reduction of the total solar irradiance, and the lowering of the maximum temperature and DTR. Copyright 2006 by the American Geophysical Union."
"7202711754;7006471143;7102011023;57218130381;6507496639;6602600129;7003620360;56184892000;56628742100;8663598300;6701518904;7402838215;6603666624;7003712786;6507819912;6701774457;8395782400;7004839466;23477923600;57193261640;7004249622;7003765782;","Tropopause and hygropause variability over the equatorial Indian Ocean during February and March 1999",2006,"10.1029/2005JD006639","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35349026761&doi=10.1029%2f2005JD006639&partnerID=40&md5=f77052272cde071a87da2ad1d20dcaba","Measurements of temperature, water vapor, total water, ozone, and cloud properties were made above the western equatorial Indian Ocean in February and March 1999. The cold-point tropopause was at a mean pressure-altitude of 17 km, equivalent to a potential temperature of 380 K, and had a mean temperature of 190 K. Total water mixing ratios at the hygropause varied between 1.4 and 4.1 ppmv. The mean saturation water vapor mixing ratio at the cold point was 3.0 ppmv. This does not accurately represent the mean of the measured total water mixing ratios because the air was unsaturated at the cold point for about 40% of the measurements. As well as unsaturation at the cold point, saturation was observed above the cold point on almost 30% of the profiles. In such profiles the air was saturated with respect to water ice but was free of clouds (i.e., backscatter ratio <2) at potential temperatures more than 5 K above the tropopause and hygropause. Individual profiles show a great deal of variability in the potential temperatures of the cold point and hygropause. We attribute this to short timescale and space-scale perturbations superimposed on the seasonal cycle. There is neither a clear and consistent ""setting"" of the tropopause and hygropause to the same altitude by dehydration processes nor a clear and consistent separation of tropopause and hygropause by the Brewer-Dobson circulation. Similarly, neither the tropopause nor the hygropause provides a location where conditions consistently approach those implied by a simple ""tropopause freeze drying"" or ""stratospheric fountain"" hypothesis. Copyright 2006 by the American Geophysical Union."
"36343109300;7402717381;9239331500;7006864972;","On the simulation of winter precipitation types",2006,"10.1029/2005JD006665","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947499332&doi=10.1029%2f2005JD006665&partnerID=40&md5=c4097c4a616e4adcaacf953cfc33829c","Winter storms produce major problems for society, and the key responsible factor is often the varying types of precipitation. The objective of this study is to better understand the formation of different types of winter precipitation (freezing rain, ice pellets, snow, slush, wet snow and refrozen wet snow) within the varying and interacting environmental conditions in many winter storms. To address this issue, a one-dimensional cloud model utilizing a double-moment bulk microphysics scheme has been developed. Temperature and moisture profiles favorable for the formation of different winter precipitation types were varied in a systematic manner in an environment where snow is falling continuously through a temperature inversion. The ensuing precipitation evolved as a result of the variations in atmospheric temperature and moisture arising from phase changes such as melting and freezing. This study underlines the often complex manner through which different precipitation types form. It also demonstrates that the formation of semimelted particles can have a profound effect on the evolution of precipitation types aloft and at the surface. Furthermore, some types of precipitation only form within a narrow range of environmental conditions. Copyright 2006 by the American Geophysical Union."
"56247691800;7404247296;56234308500;55919935700;","Critique of the tracer-tracer correlation technique and its potential to analyze polar ozone loss in chemistry-climate models",2006,"10.1029/2006JD007298","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38549171308&doi=10.1029%2f2006JD007298&partnerID=40&md5=09aa19b28a8abe27d6506c2fcadbefa6","The tracer-tracer correlation technique (TRAC) has been widely employed to infer chemical ozone loss from observations. Yet, its applicability to chemistry-climate model (CCM) data is disputed. Here, we report the successful application of TRAC on the results of a CCM simulation. By comparing TRAC-calculated ozone loss to ozone loss derived with the passive ozone method in a chemistry transport model we differentiate effects of internal mixing and cross vortex boundary mixing on a TRAC reference correlation. As a test case, we consider results of a cold Arctic winter/spring episode from an E39/C experiment, where typical features, for example, sufficient polar stratospheric cloud formation potential, denitrification and dehydration, and intermittent and final stratospheric warming events, are simulated. We find that internal mixing does not impact the TRAC-derived reference correlation at all. Mixing across the vortex boundary would lead to an underestimation of ozone loss by ∼10% when calculated with TRAC. We provide arguments that TRAC is a consistent and conservative method to derive chemical ozone loss and can be used to extract its chemical signature also from CCM simulations. As a consequence, we will be able to provide a lower bound for chemical ozone loss for model simulations where a passive ozone tracer is not available. Copyright 2006 by the American Geophysical Union."
"7005858285;13406672500;7006383649;","Impact of monsoon transitions on the physical and optical properties of aerosols",2006,"10.1029/2005JD006370","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845676905&doi=10.1029%2f2005JD006370&partnerID=40&md5=c861aa42680f867cedf07829a774ab69","Project Atmospheric Brown Cloud (ABC-Asia) has focused on measuring the anthropogenic influence of aerosols, including black carbon, to determine the extent of sunlight dimming and radiative forcing over the Asian region. As part of this project, an observatory was built in the Republic of Maldives for the long-term monitoring of climate. An inaugural campaign was conducted to investigate the influence of the shifting monsoon seasons on aerosols and climate change. The presence of black carbon and other anthropogenic aerosols over the Indian Ocean varies with the cyclic nature of the Indian Monsoon. Roughly every 6 months, the winds change directions from southwest to northeast or vice versa. From June to October the wet monsoon brings clean air into the region from the Southern Hemisphere. Conversely, the dry monsoon brings polluted air from the Indian subcontinent and Southeast Asia from November through April. As a result, the region becomes charged with black carbon and other anthropogenic pollutants during the dry monsoon. In 2004 the transition between the clean and polluted seasons resulted in nearly an order of magnitude increase of scattering and absorbing aerosols. The change was foreshadowed with small events over a 1 month period prior to the abrupt arrival of pollution over a period of a few days as air from India and Southeast Asia arrived in the Maldives at the surface level. The new, polluted aerosol was characteristically darker since the black carbon concentration increased more substantially than the overall aerosol scattering. As a result, the aerosol coalbedo at a wavelength of 550 nm showed an increase from an average of 0.028 to 0.07. Black carbon mass concentrations increased by an order of magnitude from 0.03 to 0.47 μg/m3. These measurements suggest a large increase in the aerosol radiative forcing of the region with the arrival of the dry monsoon. Copyright 2006 by the American Geophysical Union."
"9249627300;55671920100;55918418100;","A general circulation model study of the orographic gravity waves over Antarctica excited by katabatic winds",2006,"10.1029/2005JD006851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547705657&doi=10.1029%2f2005JD006851&partnerID=40&md5=52cd9a685c319e3c93cb1da08e50c583","In this study, we simulated orographic gravity waves (OGWs) over Antarctica using a T213L250 general circulation model (GCM). The GCM has a fine vertical resolution of 300 m throughout the middle atmosphere. The simulation was run for a 1-year period. Results from 21-28 June were primarily considered. OGWs are excited by katabatic winds that travel down the surface slopes of the Antarctic ice sheet. A strong eastward katabatic wind blows over the west coast of the Ross Sea at the approach of the synoptic-scale upper tropospheric westerly jets. A quasi-stationary OGW is then excited above the coast and propagates upward into the mesosphere. An OGW appears sporadically during the Antarctic winter and spring. Its amplitude is determined by the strength of the eastward katabatic wind. Dissipation of OGWs within the middle atmosphere results in a localized deceleration of westerly winds, greater than - 30 m s-1 d-1. This in turn modifies the horizontal circulation in the polar vortex. Strong vertical mixing occurs withmi the mesosphere and is associated with wave breaking. Large temperature fluctuations associated with the OGWs affect the formation or suppression of polar stratospheric clouds in the lower stratosphere. Katabatic wind excitation is the most powerful source of gravity waves over Antarctica around the time of the winter solstice. Copyright 2006 by the American Geophysical Union."
"55729083100;7403968239;","Response of water vapor and clouds to El Niño warming in three National Center for Atmospheric Research atmospheric models",2006,"10.1029/2005JD006700","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847061248&doi=10.1029%2f2005JD006700&partnerID=40&md5=490781502ae9ed41fce49313b2e9abda","The response of water vapor and clouds to El Niño warming over the tropical Pacific in the most recent three versions of the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM2, T42 CAM3, and T85 CAM3) is quantified and compared to observations. It is found that all three models have a stronger response in the greenhouse effect of water vapor than that indicated in Earth Radiation Budget Experiment (ERBE) observations. The overestimate is most severe in the T85 CAM3 (up to 36%). Compared with National Centers for Environmental Prediction (NCEP) reanalysis, all three models have an excessive response of atmospheric moisture content in the upper troposphere, suggesting a cause for the excessive response in the greenhouse effect of water vapor. The response in the greenhouse effect of clouds (the longwave forcing of clouds) in two of the models (CAM2 and T42 CAM3) is significantly weaker than that indicated in ERBE observations, but it is comparable to the observed in the T85 CAM3. The improvement in the T85 CAM3 in simulating the response in the greenhouse effect is helped by a stronger response in the middle level clouds in the model (compared to CAM2 and T42 CAM3). In contrast to the strong negative response in the shortwave forcing seen in the ERBE observations, the response of the shortwave forcing of clouds in the CAM2 and the T42 CAM3 is weak and even has a sign opposite to observations when it is averaged over the entire region of surface warming. The simulation of the response of the shortwave forcing in the T85 CAM3 is considerably improved, though the negative response over the equatorial Pacific is still not strong enough compared to ERBE observations. The stronger negative response in the shortwave forcing in the T85 CAM3 is apparently linked to a stronger response in the middle level cloud cover. All three models fail to simulate the observed pattern of the response in the low cloud cover over the central and eastern Pacific, resulting in deficiency in the response of the shortwave cloud forcing in that region. The deficiency in the low cloud cover response suggests that the low cloud cover scheme has room for improvement."
"7005035762;6701670597;7501720647;22975069200;7202625046;","The interaction of clouds and dry air in the eastern tropical Pacific",2006,"10.1175/JCLI3836.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749621375&doi=10.1175%2fJCLI3836.1&partnerID=40&md5=cb57688c83fabe04ed3bc3ee465b284a","Cloud radar observations of eastern Pacific intertropical convergence zone cloud vertical structure are interpreted in light of soundings, 100-km-scale divergence profiles calculated from precipitation radar Doppler velocities, and surface rain gauge data, from a ship at 10°N, 95°W during the 2001 East Pacific Investigation of Climate (EPIC) experiment. The transition from convective to stratiform rain is clear in all four datasets, indicating a coherence from local to 100-km scale. A novel finding is dry air intrusions at altitudes of 6-8 km, often undercutting upper-level ice clouds. Two distinct dry air source regions are identified. One is a relatively dry area overlying the cooler waters of the Costa Rica oceanic thermocline dome, centered approximately 400 km east-northeast of the ship site. The other is the even drier near-equatorial subsidence zone south of 6°-7°N. The former source is somewhat peculiar to this specific ship location, so that the ship sample is not entirely representative of the region. The 20-25 Septembe r period is studied in detail, as it depicts two influences of the dry air on cloud vertical structure. One is the modulation of small-scale surface-based convection, evident as a weakening and narrowing of cloud radar reflectivity features. The other springs from intense sublimation cooling as differential advection brought snowing anvil clouds over the dry layers. During one half-day period of strong sublimation, the cooling rate is inferred to be several tens of degrees per day over a 100-hPa layer, based on a heat budget estimate at 100-km scale involving the horizontal wind divergence data. This is consistent with fluxing ice water contents of 0.05-0.10 g m-3 derived from the cloud radar reflectivities. The temperature profile shows the dynamically expected response to this cooling, a positive-negative-positive temperature anomaly pattern centered on the sublimating layer. A buoyancy-sorting diagnostic model of convection indicates that these upper-troposphere temperature anomalies can cause premature detrainment of updrafts into the lower part of the cloudy layer, a feedback that may actively maintain these long-lasting dense anvils. Middle-troposphere southerly dry air inflow is also evident in large-scale analysis. Given the proximity of the dry equatorial subsidence zone to the eastern tropical Pacific, the differential advection of dry and cloudy air, the ensuing sublimation, and its dynamical aftereffects may play a role in establishing the region's climate, although the extent of their significance needs to be further established. © 2006 American Meteorological Society."
"7406091975;7402933297;7102517130;7409322518;7004160106;7402390191;","Atmospheric teleconnection over Eurasia induced by aerosol radiative forcing during boreal spring",2006,"10.1175/JCLI3871.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749629383&doi=10.1175%2fJCLI3871.1&partnerID=40&md5=05badd38c5cd5153843efad40311902a","The direct effects of aerosols on global and regional climate during boreal spring are investigated based on numerical simulations with the NASA Global Modeling and Assimilation Office finite-volume general circulation model (fvGCM) with Microphysics of Clouds with the Relaxed-Arakawa Schubert Scheme (McRAS), using aerosol forcing functions derived from the Goddard Ozone Chemistry Aerosol Radiation and Transport model (GOCART). The authors find that anomalous atmospheric heat source s induced by absorbing aerosols (dust and black carbon) excite a planetary-scale teleconnection pattern in sea level pressure, temperature, and geopotential height spanning North Africa through Eurasia to the North Pacific. Surface cooling due to direct effects of aerosols is found in the vicinity and downstream of the aerosol source regions, that is, South Asia, East Asia, and northern and western Africa. Significant atmospheric heating is found in regions with large loading of dust (over northern Africa and the Middle East) and black carbon (over Southeast Asia). Paradoxically, the most pronounced feature in aerosol-induced surface temperature is an east-west dipole anomaly with strong cooling over the Caspian Sea and warming over central and northeastern Asia, where aerosol concentrations are low. Analyses of circulation anomalies show that the dipole anomaly is a part of an atmospheric teleconnection pattern driven by atmospheric heating anomalies induced by absorbing aerosols in the source regions, but the influence was conveyed globally through barotropic energy dispersion and sustained by feedback processes associated with the regional circulations. The surface temperature sign ature associated with the aerosol-induced teleconnection bears striking resemblance to the spatial pattern of observed long-term trend in surface temperature over Eurasia. Additionally, the boreal spring wave train pattern is similar to that reported by Fukutomi et al. associated with the boreal summer precipitation seesaw between eastern and western Siberia. The results of this study raise the possibility that global aerosol forcing during boreal spring may play an important role in spawning atmospheric teleconnections that affect regional and global climates. © 2006 American Meteorological Society."
"36238722200;57203367163;7402584913;7202162685;","Intercomparison of Arctic regional models: Modeling clouds and radiation for SHEBA in May 1998",2006,"10.1175/JCLI3854.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749069295&doi=10.1175%2fJCLI3854.1&partnerID=40&md5=360f80c52c372f73c041448832ff2eba","To improve simulations of the Arctic climate and to quantify climate model errors, four regional climate models [the Arctic Regional Climate System Model (ARCSYM), the Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS), the High-Resolution Limited-Area Model (HIRHAM), and the Rossby Center Atmospheric Model (RCA)] have simulated the annual Surface Heat Budget of the Arctic Ocean (SHEBA) under the Arctic Regional Climate Model Intercomparison Project (ARCMIP). The same lateral boundary and ocean surface boundary conditions (i.e., ice concentration and surface temperature) drive all of the models. This study evaluated modeled surface heat fluxes and cloud fields during May 1998, a month that included the onset of the surface icemelt. In general, observations agreed with simulated surface pressure and near-surface air properties. Simulation errors due to surface fluxes and cloud effects biased the net simulated surface heat flux, which in turn affected the timing of the simulated icemelt. Modeled cloud geometry and precipitation suggest that the RCA model produced the most accurate cloud scheme, followed by the HIRHAM model. Evaluation of a relationship between cloud water paths and radiation showed that a radiative transfer scheme in ARCSYM was closely matched with the observation when liquid clouds were dominant. Clouds and radiation are of course closely linked, and an additional comparison of the radiative transfer codes for ARCSYM and COAMPS was performed for clear-sky conditions, thereby excluding cloud effects. Overall, the schemes for radiative transfer in ARCSYM and for cloud microphysics in RCA potentially have some advantages for modeling the springtime Arctic. © 2006 American Meteorological Society."
"7005495256;7103060756;","Relationship between shortwave cloud radiative forcing and local meteorological variables compared in observations and several global climate models",2006,"10.1175/JCLI3875.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749068690&doi=10.1175%2fJCLI3875.1&partnerID=40&md5=34fcd011ae0687e9595d51e5e86c24ae","The relations between local monthly mean shortwave cloud radiative forcing and aspects of the resolved-scale meteorological fields are investigated in hindcast simulations performed with 12 of the global coupled models included in the model intercomparison conducted as part of the preparation for Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). In particular, the connection of the cloud forcing over tropical and subtropical ocean areas with resolved midtropospheric vertical velocity and with lower-level relative humidity are investigated and compared among the models. The model results are also compared with observational determinations of the same relationships using satellite data for the cloud forcing and global reanalysis products for the vertical velocity and humidity fields. In the analysis the geographical variability in the long-term mean among all grid points and the interannual variability of the monthly mean at each grid point are considered separately. The shortwave cloud radiative feedback (SWCRF) plays a crucial role in determining the predicted response to large-scale climate forcing (such as from increased greenhouse gas concentrations), and it is thus important to test how the cloud representations in current climate models respond to unforced variability. Overall there is considerable variation among the results for the various models, and all models show some substantial differences from the comparable observed results. The most notable deficiency is a weak representation of the cloud radiative response to variations in vertical velocity in cases of strong ascending or strong descending motions. While the models generally perform better in regimes with only modest upward or downward motions, even in these regimes there is considerable variation among the models in the dependence of SWCRF on vertical velocity. The largest differences between models and observations when SWCRF values are stratified by relative humidity are found in either very moist or very dry regimes. Thus, the largest errors in the model simulations of cloud forcing are prone to be in the western Pacific warm pool area, which is characterized by very moist strong upward currents, and in the rather dry regions where the flow is dominated by descending mean motions. © 2006 American Meteorological Society."
"8582278100;","Desert storms",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750340297&partnerID=40&md5=35a77cc84c7a7404a3f379f15ec4eb58","Dust from the Sahara has an enormous influence on how the sunlight is scattered and absorbed. Dust storm has a huge impact on radiation in the atmosphere. More modest aerosol clouds that typify the dry season are important for the local climate. Understanding how greenhouse gases, aerosols and clouds control the radiative heating and cooling of this planet is vital in building more accurate climate models."
"7201837768;6603809220;","The radiative influence of aerosol effects on liquid-phase cumulus and stratiform clouds based on sensitivity studies with two climate models",2006,"10.1007/s00382-006-0139-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745698744&doi=10.1007%2fs00382-006-0139-3&partnerID=40&md5=492065d1f688e7980d76573f13cd8b5a","Aerosol effects on warm (liquid-phase) cumulus cloud systems may have a strong radiative influence via suppression of precipitation in convective systems. A consequence of this suppression of precipitation is increased liquid water available for large-scale stratiform clouds, through detrainment, that in turn affect their precipitation efficiency. The nature of this influence on radiation, however, is dependent on both the treatment of convective condensate and the aerosol distribution. Here, we examine these issues with two climate models - CSIRO and GISS, which treat detrained condensate differently. Aerosol-cloud interactions in warm stratiform and cumulus clouds (via cloud droplet formation and autoconversion) are treated similarly in both models. The influence of aerosol-cumulus cloud interactions on precipitation and radiation are examined via simulations with present-day and pre-industrial aerosol emissions. Sensitivity tests are also conducted to examine changes to climate due to changes in cumulus cloud droplet number (Nc); the main connection between aerosols and cumulus cloud microphysics. Results indicate that the CSIRO GCM is quite sensitive to changes in aerosol concentrations such that an increase in aerosols increases Nc cloud cover, total liquid water path (LWP) and reduces total precipitation and net cloud radiative forcings. On the other hand, the radiative fluxes in the GISS GCM appear to have minimal changes despite an increase in aerosols and Nc. These differences between the two models - reduced total LWP in the GISS GCM for increased aerosols, opposite to that seen in CSIRO - appear to be more sensitive to the detrainment of convective condensate, rather than to changes in Nc. If aerosols suppress convective precipitation as noted in some observationally based studies (but not currently treated in most climate models), the consequence of this change in LWP suggests that: (1) the aerosol indirect effect (calculated as changes to net cloud radiative forcing from anthropogenic aerosols) may be higher than previously calculated or (2) lower than previously calculated. Observational constrains on these results are difficult to obtain and hence, until realistic cumulus-scale updrafts are implemented in models, the logic of detraining non-precipitating condensate at appropriate levels based on updrafts and its effects on radiation, will remain an uncertainty. © Springer-Verlag 2006."
"8247122100;7601492669;57202301596;7005170782;","Effect of shallow cumulus convection on the eastern Pacific climate in a coupled model",2006,"10.1029/2006GL026715","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845609143&doi=10.1029%2f2006GL026715&partnerID=40&md5=15f6f1674f2208a85e6201ccbc69bc63","Shallow cumulus convection evaporates stratocumulus clouds in the atmospheric boundary layer. The effect of shallow convection on the large-scale climate of the eastern tropical Pacific is investigated with a coupled ocean-atmosphere model by disabling the shallow convection parameterization (noSC). Without shallow convection, the stratiform cloud fraction increases and surface solar radiation decreases. The sea surface temperature (SST) cools on average by 2°C. The cooling in noSC is larger under the low cloud deck south of the equator than north of the equator, resulting in an increase in the climatic meridional asymmetry. In the control run an ITCZ forms south of the equator in March-April. In noSC the SST- is at most 24°C south of the equator and an ITCZ does not form. The perennial northern-hemisphere ITCZ in noSC is accompanied by year-round southerlies of at least ∼3 m s -1 on the equator, considerably reducing the seasonal cycle of equatorial SST. Copyright 2006 by the American Geophysical Union."
"15822643700;23061019000;57209147154;","Cloud type climatology over the Tibetan Plateau: A comparison of ISCCP and MODIS/TERRA measurements with surface observations",2006,"10.1029/2006GL026890","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845646295&doi=10.1029%2f2006GL026890&partnerID=40&md5=87eaeb4338f3a7c0c3a0fa98b35299c7","Area averaged seasonal climatology of high, middle and low clouds over the Tibetan Plateau was obtained from the International Satellite Cloud Climatology Project (ISCCP) D2 and the Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra products, and was compared with climatology calculated by using the Carbon Dioxide Information Analysis Center (CDIAC) Cloud Climatology for Land Station Worldwide. From all three data sets, there is a large degree of consistency for the high cloud climatology in terms of amount and occurrence frequency. A great amount of high clouds exists over the Tibetan Plateau and its seasonal cycle is evident with the largest amount and highest frequency in spring and summer. However, compared with the surface observations, both the ISCCP D2 and the MODIS/Terra products largely underestimated low clouds over the Tibetan Plateau. Approximately, the underestimation of cloud amount from the ISCCP D2 is more than 20% and cloud frequency bias from the MODIS/Terra up to 50%; moreover, a quite large discrepancy in the seasonal cycle is shown. For middle clouds, the ISCCP D2 and the MODIS/Terra products overestimate amount and occurrence frequency, and present rather weak seasonal variation compared with the weather station data. When using satellite data to analyze cloud cover the Tibetan Plateau, certain issues about large potential bias must be taken into consideration, and particularly, great caution is needed while using the ISCCP D2 and MODIS data to study middle and low clouds, especially when high and thick clouds exist. Copyright 2006 by the American Geophysical Union."
"35232873900;7006417494;8544421800;7501956187;","Regional tropical precipitation change mechanisms in ECHAM4/OPYC3 under global warming",2006,"10.1175/JCLI3858.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749044809&doi=10.1175%2fJCLI3858.1&partnerID=40&md5=ffc19d9186975e8b771d9c1ea3f9c96b","Mechanisms of global warming impacts on regional tropical precipitation are examined in a coupled atmosphere-ocean general circulation model (ECHAM4/OPYC3). The pattern of the regional tropical precipitation changes, once established, tends to persist, growing in magnitude as greenhouse gases increase. The sulfate aerosol induces regional tropical precipitation anomalies similar to the greenhouse gases but with opposite sign, thus reducing the early signal. Evidence for two main mechanisms, the upped-ante and the anomalous gross moist stability (M′) mechanisms (previously proposed in an intermediate complexity model), is found in this more comprehensive coupled general circulation model. Preferential moisture increase occurs in convection zones. The upped-ante mechanism signature of dry advection from nonconvective regions is found in tropical drought regions on the margins of convection zones. Here advection in both the atmospheric boundary layer and lower free troposphere are found to be important, with an additional contribution from horizontal temperature transport in some locations. The signature of the M' mechanism-moisture convergence due to increased moisture in regions of large mean vertical motion - enhances precipitation within strong convective regions. Ocean dynamical feedbacks can be assessed by net surface flux, the main example being the El Niño-like shift of the equatorial Pacific convection zone. Cloud-radiative feedbacks are found to oppose precipitation anomalies over ocean regions. © 2006 American Meteorological Society."
"15032788000;7006358256;7103119050;","Effects of cirrus near the tropopause on anvil cirrus dynamics",2006,"10.1029/2006GL027071","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750599732&doi=10.1029%2f2006GL027071&partnerID=40&md5=9aaa71894e1b32804a5f4a3f12f21439","Recent space and airborne observations have noted tenuous cirrus near the tropopause and above deep convective anvil outflow. We use a cloud-resolving model, initialized with aircraft observations taken during the CRYSTAL-FACE experiment, to explore the effects of such cirrus layers on anvil evolution. Numerical simulations demonstrate that anvil cirrus spreads because strong absorption of thermal radiation and emission at cloud base and top creates horizontal heating gradients between the cloud and its environment. The presence of a second layer of cirrus near the tropopause forces the upper part of the anvil to equilibrate to wanner radiative temperatures than would normally be associated with a clear upper atmosphere. Compared to a case without thin cirrus, the associated reduction to heating gradients at anvil cloud top corresponds to reduced anvil spreading and turbulent kinetic energy, by as much as 19% and 40%, respectively. These results suggest that tropopause cirrus can affect climate indirectly, by altering anvil cirrus dynamics. Copyright 2006 by the American Geophysical Union."
"7103172539;21735966500;55222940900;7004759191;57199843170;7003371432;","On the simulation of regional scale sublimation over boreal and agricultural landscapes in a climate model",2006,"10.3137/ao.440306","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750691700&doi=10.3137%2fao.440306&partnerID=40&md5=9e6b0a3ec5772c5b3d84a01a6154936c","In this study, a detailed evaluation of regional scale sublimation over two contrasting surface types is performed, based on observations and simulations from a regional climate model. New observed estimates of regional scale evaporative fractions (sublimation/precipitation) based on remotely sensed and gridded surface climate data suggest values of 0.16 and 0.09 respectively for boreal forest and agricultural regions during mid-winter. While not dominating the water balance, this does indicate that sublimation is a significant component at the regional scale. On the other hand, simulated results were substantially less: 0.02 and -0.02 (i.e., net vapour deposition) respectively. Further analysis revealed that in both cases a net vapour deposition onto the ground snowpack was found, though in the forested case this was offset by a positive vapour flux off the canopy yielding a small net positive flux overall. Even over the agricultural region, sublimation was simulated during daytime in January, but this was overwhelmed by night-time frost, resulting in a net daily vapour deposition. The source of the surface vapour flux bias was further investigated. An attempt was made to enhance sublimation by increasing the sensible heat flux based on the ""windless exchange"" concept, which has been found helpful in studies of stand-alone snowpack models. However, in the coupled atmosphere-land surface model used here, increases in sensible heat flux into the snow were largely offset by increases in upward surface longwave flux: the net impact on sublimation and surface temperature bias was small. A proposed cold snow-vapour deposition feedback mechanism, under clear sky conditions, was determined to be unlikely for the simulation under consideration. The impact of cloud cover appears to be much more relevant to our simulation of the surface energy balance over snow. Satellite and limited surface radiation observations suggest that insufficient cloud radiative forcing simulated in the model was responsible for the excessive night-time frost."
"35554446700;7201953443;6701859365;35549146800;24322892500;7003484057;14826922900;14826874700;","Offshore radiation observations for climate research at the CERES Ocean validation experiment: A New ""laboratory"" for retrieval algorithm testing",2006,"10.1175/BAMS-87-9-1211","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749412302&doi=10.1175%2fBAMS-87-9-1211&partnerID=40&md5=9efe2a30e1384c811fea601c852f917d","When radiometers on satellites point toward Earth with the goal of sensing an important variable quantitatively, rather than just creating a pleasing image, the task at hand is often not simple. The electromagnetic energy detected by the radiometers is a puzzle of various signals; it must be solved to quantify the specific physical variable. This task, called the retrieval or remote-sensing process, is important to most satellite-based observation programs. It would be ideal to test the algorithms for retrieval processes in a sealed laboratory, where all the relevant parameters could be easily measured. The size and complexity of the Earth make this impractical. NASA's Clouds and the Earth's Radiant Energy System (CERES) project has done the next-best thing by developing a long-term radiation observation site over the ocean. The relatively low and homogeneous surface albedo of the ocean make this type of site a simpler environment for observing and validating radiation parameters from satellite-based instruments. To characterize components of the planet's energy budget, CERES uses a variety of retrievals associated with several satellite-based instruments onboard NASA's Earth Observing System (EOS). A new surface observation project called the CERES Ocean Validation Experiment (COVE), operating on a rigid ocean platform, is supplying data to validate some of these instruments and retrieval products. This article describes the ocean platform and the types of observations being performed there, and highlights of some scientific problems being addressed. © 2006 American Meteorological Society."
"7201498373;7005557215;7004126618;","Soil moisture feedbacks to precipitation in Southern Africa",2006,"10.1175/JCLI3856.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749055946&doi=10.1175%2fJCLI3856.1&partnerID=40&md5=02afd36b29612cc33ef1bffe1ff23b22","The effects of increased soil moisture on wet season (October-March) precipitation in southern Africa are investigated using the Community Climate System Model version 3 (CCSM3). In the CTRL case, soil moisture is allowed to interact dynamically with the atmosphere. In the MOIST case, soil moisture is set so that evapotranspiration is not limited by the supply of water. The MOIST scenario actually results in decreased precipitation over the region of perturbed soil moisture, compared to CTRL. The increased soil moisture alters the surface energy balance, resulting in a shift from sensible to latent heating. This manifests in two ways relevant for precipitation processes, First, the shift from sensible to latent heating cools the surface, causing a higher surface pressure, a reduced boundary layer height, and an increased vertical gradient in equivalent potential temperature. These changes are indicative of an increase in atmospheric stability, inhibiting vertical movement of air parcels and decreasing the ability of precipitation to form. Second, the surface changes induce anomalous surface divergence and increased subsidence. This causes a reduction in cloud cover and specific humidity above 700 hPa and results in a net decrease of column-integrated precipitable water, despite the increased surface water flux, indicating a reduction in moisture convergence. Based on this and a previous study, soil moisture may act as a negative feedback to precipitation in southern Africa, helping to buffer the system against any external forcing of precipitation (e.g.,ENSO). © 2006 American Meteorological Society."
"14071914800;56179033200;56848611900;","Measurements of the HONO photodissociation constant",2006,"10.1007/s10874-006-9021-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33747493037&doi=10.1007%2fs10874-006-9021-2&partnerID=40&md5=e47dc38e872c1783921b4996e6a3e92b","Measurements of the photodissociation constant for nitrous acid (jHONO) were made at an urban site in Toronto, Canada, during the months of May-July 2005, using an optically thin actinometer. Operating details of the jHONO monitor are reported, along with laboratory tests. Measurements of jHONO were obtained for solar zenith angles ranging from 20-75°, under clear and cloudy skies. Maximum error estimates on jHONO under clear skies range from 11% at sunrise, to 4% at solar noon, with a minimum detection limit of 5.7 × 10-4/sec for our actinometer. Measured clear-sky values of jHONO were compared with values calculated by a four-stream discrete ordinate radiative transfer (RT) model (ACD TUV version 4.1), and were found to be within better than 10% agreement for solar zenith angles &lt;65°. For conditions of scattered cloud, enhancement and suppression of the jHONO values occurred by as much as 16%-70%, and 59%-80%, respectively. The integrated band area of the nπ* transition for gas-phase nitrous acid yields an oscillator strength, f = (1.06 ± 0.044) × 10-3 (based on clear-sky data), 19.1% higher than the value reported by Bongartz et al. (1991). © Springer Science+Business Media B.V. 2006."
"25227357000;7102018821;7402270607;7004544454;7501797728;56139519000;","Climatic effects of different aerosol types in China simulated by the UCLA general circulation model",2006,"10.1029/2005JD006312","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845917295&doi=10.1029%2f2005JD006312&partnerID=40&md5=3fc8213e3adbb474b2cde7e536f51ded","The climatic effects of various types of aerosol in China have been investigated by 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 specifically developed for application to clouds and aerosols. Simulation results show that inclusion of a background aerosol optical depth of 0.2 reduces the global mean net surface solar flux by about 5 W m-2 and produces a decrease in precipitation in the tropics as a result of decreased temperature contrast between this area and the middle to high latitudes, which suppresses tropical convection. These decreases have partially corrected the overestimates in the surface solar flux and precipitation in the UCLA AGCM simulations without the aerosol effect. The experiment with increased aerosol optical depths in China shows a noticeable increase in precipitation in the southern part of China in July due to the cooling in the midlatitudes that leads to the strengthening of the Hadley circulation. Aerosol types play an important role in the determination of the global mean radiation budget and regional climate. While sulfates mainly reflect solar radiation and induce negative forcing at the surface, black carbon and large dust particles absorb substantial solar radiation and have a positive solar forcing at the top of the atmosphere, but reduce the solar radiation reaching the surface. Large dust particles also have a significant effect on thermal IR radiation under clear conditions, but this effect is largely masked by clouds generated from the model in AGCM simulations. Black carbon and large dust particles in China would heat the air column in the middle to high latitudes and tend to move the simulated precipitation inland, i.e., toward the Himalayas. The inclusion of black carbon in our simulations has not produced the ""north drought/south flooding"" precipitation pattern that has frequently occurred in China during the past 50 years. Copyright 2006 by the American Geophysical Union."
"7006133602;36719571800;","Extreme wet years over southern Africa: Role of Indian Ocean sea surface temperatures",2006,"10.1029/2005JD006724","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845920315&doi=10.1029%2f2005JD006724&partnerID=40&md5=41999deacb5231abe38c7512bdfce237","Southern Africa is a predominantly semiarid region with a high degree of interannual rainfall variability. Although much of the recent climate research has focused on the causes of drought events, the region has also experienced extremes of above average rainfall, the most recent examples being the major flooding episodes that devastated Mozambique during 2000 and 2001. This paper investigates extremely wet years over southern Africa during the twentieth century. Focusing on the two most extreme years, 1974 and 1976, we show that while ENSO serves as an important control on rainfall variability, a specific pattern of SSTs in the SW Indian Ocean, with warm anomalies in the subtropical SW Indian Ocean and cool anomalies in the northern SW Indian Ocean that is statistically independent of ENSO, plays a crucial role in generating extreme conditions. To do this, we use a series of multimodel experiments, to demonstrate first the importance of global sea surface temperatures. Through additional idealized experiments with HadAM3, we then isolate the role of SST anomalies in the Indian Ocean. The anomalies are based on the observed SSTs with the ENSO signal linearly removed. The critical influence is tied to cold SST anomalies in the Mascarene region which induce an anomalous anticyclonic circulation driving an anomalous low-level easterly moisture flux along 10-20°S into eastern southern Africa. This results in enhanced moist convective uplift, conducive to enhanced rainfall, over a large part of southern Africa. Near surface humidity and 500-hPa omega fields extend from eastern southern Africa into the Agulhas region in a tropical-temperate cloud band like structure. The similarity between the reanalysis fields for the extreme years and the model experiments is striking. Copyright 2006 by the American Geophysical Union."
"36851768400;6603934441;7201706787;55547129338;","Observed relationships between Arctic longwave cloud forcing and cloud parameters using a neural network",2006,"10.1175/JCLI3839.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748793650&doi=10.1175%2fJCLI3839.1&partnerID=40&md5=1bd06ebe7ae6d5c0eb810cbfd1fbae20","A neural network technique is used to quantify relationships involved in cloud-radiation feedbacks based on observations from the Surface Heat Budget of the Arctic (SHEBA) project. Sensitivities of longwave cloud forcing (CFL) to cloud parameters indicate that a bimodal distribution pattern dominates the histogram of each sensitivity. Although the mean states of the relationships agree well with those derived in a previous study, they do not often exist in reality. The sensitivity of CFL to cloud cover increases as the cloudiness increases with a range of 0.1-0.9 W m-2 %-1. There is a saturation effect of liquid water path (LWP) on CFL. The highest sensitivity of CFL to LWP corresponds to clouds with low LWP, and sensitivity decreases as LWP increases. The sensitivity of CFL to cloud-base height (CBH) depends on whether the clouds are below or above an inversion layer. The relationship is negative for clouds higher than 0.8 km at the SHEBA site. The strongest positive relationship corresponds to clouds with low CBH. The dominant mode of the sensitivity of CFL to cloud-base temperature (CBT) is near zero and corresponds to warm clouds with base temperatures higher than -9°C. The low and high sensitivity regimes correspond to the summer and winter seasons, respectively, especially for LWP and CBT. Overall, the neural network technique is able to separate two distinct regimes of clouds that correspond to different sensitivities; that is, it captures the nonlinear behavior in the relationships. This study demonstrates a new method for evaluating nonlinear relationships between climate variables. It could also be used as an effective tool for evaluating feedback processes in climate models. © 2006 American Meteorological Society."
"6603144464;7005137442;55165863400;6603374472;","Modelling the primary control of paleogeography on Cretaceous climate",2006,"10.1016/j.epsl.2006.06.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746481737&doi=10.1016%2fj.epsl.2006.06.007&partnerID=40&md5=7f9807ff7a8fcfe6268df91b23c4b512","The low thermal gradients and clement winters characterizing climates of the Cretaceous period reveal that the climate system has modes of behaviour quite different from the present. Recent proxy data analyses suggest that some aspects of climate change within the Cretaceous appear to be decoupled from CO2 evolution at the geological time scale. Here, we investigate the impact of paleogeography on the global climate with the climate model FOAM, using a Early, Mid and Late Cretaceous continental configuration. We find that changes in geography from the Early to Mid-to-Late Cretaceous cause a large decrease of the seasonal cycle. First order identified processes are the decreased continentality of the mid-to-high latitudes from the Mid Cretaceous and the increase of the latent heat transport into the winter hemisphere which induce a wetter and a cloudier atmosphere capable of diminishing the winter cooling of the continents. Owing to the modifications of the seasonal cycle in response to the tectonic forcing, the equator-to-pole thermal gradient is reduced from the Early to Mid-to-Late Cretaceous. We nevertheless still do not succeed in simulating warm enough polar temperatures and a definitive theory still waits for an integrated approach explicitly accounting for each factor influencing the thermal gradient (ocean dynamics, stratospheric clouds, and vegetation). Our study also suggests a mechanism that can weaken the correlation between CO2 and climate changes during the Cretaceous as evolving geography from the Early to Late Cretaceous, through the response of the water cycle and the changes in the thermal gradient, results in a 3.8 °C global warming at a constant atmospheric CO2 level. This demonstrates that the paleogeography may affect the relation between pCO2 and the climate history and consequently has to be accounted for when linking the atmospheric CO2 evolution and the climate record at geological time scales. © 2006 Elsevier B.V. All rights reserved."
"7403968239;55729083100;57206546845;7402064802;56520921400;7005814217;7005513582;7006518289;7005808242;35497573900;","Radiative and dynamical feedbacks over the equatorial cold tongue: Results from nine atmospheric GCMs",2006,"10.1175/JCLI3835.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645837615&doi=10.1175%2fJCLI3835.1&partnerID=40&md5=5f807b2994ec2b238f2ab0a776b20388","The equatorial Pacific is a region with strong negative feedbacks. Yet coupled general circulation models (GCMs) have exhibited a propensity to develop a significant SST bias in that region, suggesting an unrealistic sensitivity in the coupled models to small energy flux errors that inevitably occur in the individual model components. Could this ""hypersensitivity"" exhibited in a coupled model be due to an underestimate of the strength of the negative feedbacks in this region? With this suspicion, the feedbacks in the equatorial Pacific in nine atmospheric GCMs (AGCMs) have been quantified using the interannual variations in that region and compared with the corresponding calculations from the observations. The nine AGCMs are the NCAR Community Climate Model version 1 (CAM1), the NCAR Community Climate Model version 2 (CAM2), the NCAR Community Climate Model version 3 (CAM3), the NCAR CAM3 at T85 resolution, the NASA Seasonal-to-Interannual Prediction Project (NSIPP) Atmospheric Model, the Hadley Centre Atmospheric Model (HadAM3), the Institut Pierre Simon Laplace (IPSL) model (LMDZ4), the Geophysical Fluid Dynamics Laboratory (GFDL) AM2p10, and the GFDL AM2p12. All the corresponding coupled runs of these nine AGCMs have an excessive cold tongue in the equatorial Pacific. The net atmospheric feedback over the equatorial Pacific in the two GFDL models is found to be comparable to the observed value. All other models are found to have a weaker negative net feedback from the atmosphere - a weaker regulating effect on the underlying SST than the real atmosphere. Except for the French (IPSL) model, a weaker negative feedback from the cloud albedo and a weaker negative feedback from the atmospheric transport are the two leading contributors to the weaker regulating effect from the atmosphere. The underestimate of the strength of the negative feedbacks by the models is apparently linked to an underestimate of the equatorial precipitation response. All models have a stronger water vapor feedback than that indicated in Earth Radiation Budget Experiment (ERBE) observations. These results confirm the suspicion that an underestimate of the regulatory effect from the atmosphere over the equatorial Pacific region is a prevalent problem. The results also suggest, however, that a weaker regulatory effect from the atmosphere is unlikely solely responsible for the hypersensitivity in all models. The need to validate the feedbacks from the ocean transport is therefore highlighted. © 2006 American Meteorological Society."
"7007021059;8979277400;10243650000;7102857642;7201485519;7404142321;7003976079;7003543851;26643217800;7004033942;","Importance of the mixed-phase cloud distribution in the control climate for assessing the response of clouds to carbon dioxide increase: A multi-model study",2006,"10.1007/s00382-006-0127-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744745307&doi=10.1007%2fs00382-006-0127-7&partnerID=40&md5=53e3bf87091fa1ea9ad680b01b0a2899","We have conducted a multi-model intercomparison of cloud-water in five state-of-the-art AGCMs run for control and doubled carbon dioxide climates. The most notable feature of the differences between the control and doubled carbon dioxide climates is in the distribution of cloud-water in the mixed-phase temperature band. The difference is greatest at mid and high latitudes. We found that the amount of cloud ice in the mixed phase layer in the control climate largely determines how much the cloud-water distribution changes for the doubled carbon dioxide climate. Therefore evaluation of the cloud ice distribution by comparison with data is important for future climate sensitivity studies. Cloud ice and cloud liquid both decrease in the layer below the melting layer, but only cloud liquid increases in the mixed-phase layer. Although the decrease in cloud-water below the melting layer occurs at all latitudes, the increase in cloud liquid in the mixed-phase layer is restricted to those latitudes where there is a large amount of cloud ice in the mixed-phase layer. If the cloud ice in the mixed-phase layer is concentrated at high latitudes, doubling of carbon dioxide might shift the center of cloud water distribution poleward which could decrease solar reflection because solar insolation is less at higher latitude. The magnitude of this poleward shift of cloud water appears to be larger for the higher climate sensitivity models, and it is consistent with the associated changes in cloud albedo forcing. For the control climate there is a clear relationship between the differences in cloud-water and relative humidity between the different models, for both magnitude and distribution. On the other hand the ratio of cloud ice to cloud-water follows the threshold temperature which is determined in each model. Improved measurements of relative humidity could be used to constrain the modeled representation of cloud water. At the same time, comparative analysis in global cloud resolving model simulations is necessary for further understanding of the relationships suggested in this paper. © Springer-Verlag 2006."
"6602878057;7004479957;6701431208;7005513582;7005808242;57218978147;7402064802;7003543851;","A comparison of low-latitude cloud properties and their response to climate change in three AGCMs sorted into regimes using mid-tropospheric vertical velocity",2006,"10.1007/s00382-006-0138-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646440016&doi=10.1007%2fs00382-006-0138-4&partnerID=40&md5=c67367343b23e76b62fbb04f04cde3d4","Low-latitude cloud distributions and cloud responses to climate perturbations are compared in near-current versions of three leading U.S. AGCMs, the NCAR CAM 3.0, the GFDL AM2.12b, and the NASA GMAO NSIPP-2 model. The analysis technique of Bony et al. (Clim Dyn 22:71-86, 2004) is used to sort cloud variables by dynamical regime using the monthly mean pressure velocity ω at 500 hPa from 30S to 30N. All models simulate the climatological monthly mean top-of-atmosphere longwave and shortwave cloud radiative forcing (CRF) adequately in all ω-regimes. However, they disagree with each other and with ISCCP satellite observations in regime-sorted cloud fraction, condensate amount, and cloud-top height. All models have too little cloud with tops in the middle troposphere and too much thin cirrus in ascent regimes. In subsidence regimes one model simulates cloud condensate to be too near the surface, while another generates condensate over an excessively deep layer of the lower troposphere. Standardized climate perturbation experiments of the three models are also compared, including uniform SST increase, patterned SST increase, and doubled CO2 over a mixed layer ocean. The regime-sorted cloud and CRF perturbations are very different between models, and show lesser, but still significant, differences between the same model simulating different types of imposed climate perturbation. There is a negative correlation across all general circulation models (GCMs) and climate perturbations between changes in tropical low cloud cover and changes in net CRF, suggesting a dominant role for boundary layer cloud in these changes. For some of the cases presented, upper-level clouds in deep convection regimes are also important, and changes in such regimes can either reinforce or partially cancel the net CRF response from the boundary layer cloud in subsidence regimes. This study highlights the continuing uncertainty in both low and high cloud feedbacks simulated by GCMs. © Springer-Verlag 2006."
"55258950300;7003437716;57203078473;7005088845;7404243086;55624487580;7404865816;14012040000;55108267700;15725583500;7005071789;","Aircraft measurements of cloud droplet spectral dispersion and implications for indirect aerosol radiative forcing",2006,"10.1029/2006GL026653","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845633827&doi=10.1029%2f2006GL026653&partnerID=40&md5=32b6717300de3cd2ff879fe7ff9ef4c6","Using a large amount of aircraft measurements of cloud droplet size distributions, the relationship between cloud spectral relative dispersion (ε) and cloud droplet number concentration (N<inf>c</inf>) is studied. The results indicate that the value of ε varies between 0.2 to 0.8 when the cloud droplet number concentration is low (about 50 cm-3), and converges toward a narrow range of 0.4 to 0.5 when the cloud number concentration is higher. Because the distribution of the cloud droplet size is an important parameter in estimating the first indirect radiative effect of aerosols on the climate system, the uncertainty in the corresponding radiative forcing can be reduced by 10-40% (depending on cloud droplet number density) under high aerosol loading. This finding is important for improving climate change projections, especially for the regions where aerosol loading is high and continues to increase. Copyright 2006 by the American Geophysical Union."
"7005135473;24482777300;35464731600;7004174939;","Satellite-based assessment of top of atmosphere anthropogenic aerosol radiative forcing over cloud-free oceans",2006,"10.1029/2005GL025535","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845673297&doi=10.1029%2f2005GL025535&partnerID=40&md5=6018bfb9c609da98eccedf295d52440c","Most assessments of the direct climate forcing (DCF) of anthropogenic aerosols are from numerical simulations. However, recent advances in remote sensing techniques allow the separation of fine mode aerosols (anthropogenic aerosol is mostly fine aerosol) from coarse mode aerosols (largely marine and dust, which are mostly natural) from satellite data such as the Moderate Resolution Imaging SpectroRadiometer (MODIS). Here, by combining MODIS narrowband measurements with broadband radiative flux data sets from the Clouds and the Earth's Radiant Energy System (CERES), we provide a measurement-based assessment of the global direct climate forcing (DCF) of anthropogenic aerosols at the top of atmosphere (TOA) only for cloud free oceans. The mean TOA DCF of anthropogenic aerosols over cloud-free oceans [60N-60S] is -1.4 ± 0.9 Wm-2, which is in excellent agreement (mean value of -1.4 Wm 2) with a recent observational study by Kaufman et al. [2005]. Copyright 2006 by the American Geophysical Union."
"22936388600;7003266014;","Instantaneous cloud overlap statistics in the tropical area revealed by ICESat/GLAS data",2006,"10.1029/2005GL024350","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845669442&doi=10.1029%2f2005GL024350&partnerID=40&md5=a60e9128668999f4069c2cee6406bc44","This study uses ICESat/GLAS instantaneous observations from 29 September to 18 November 2003 to investigate cloud overlap statistics between 10°S-20°N. The results show that 75.1% of profiles detect clouds: 46.5% are single layer and 28.6% multilayer clouds (cloud layers are separated by 0.5km). Using a definition of cloud type based on cloud heights and laser attenuation information, cloud overlap statistics are derived by analyzing 96.4% of the cloudy profiles. The most frequent overlap occurs between cirrus clouds and boundary layer clouds, which accounts for 31.88% of boundary clouds. 23.8% of deep convection has overlying cirrus clouds. We find that differences exist between the cloud overlap fraction from the GLAS observations and one calculated from the random overlap assumption commonly used by climate models. Copyright 2006 by the American Geophysical Union."
"6504173221;55947319900;","Interhemispheric differences in polar mesospheric clouds observed by the HALOE instrument",2006,"10.1016/j.jastp.2006.05.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746192065&doi=10.1016%2fj.jastp.2006.05.014&partnerID=40&md5=b91ea2871dd1d36d24f92475540fbcc8","HALOE data have been used to study Polar Mesospheric Clouds (PMCs) and to investigate differences in the characteristics of the clouds between the northern and southern hemispheres. HALOE has been observing the high latitude summer regions since the fall of 1991, which has provided observations of 14 northern hemisphere and southern hemisphere PMC seasons. HALOE infrared extinction profiles are used to extract PMC extinction and the altitude of the PMC for each cloud observation. We present evidence of higher PMC occurrence frequencies, lower cloud altitudes and larger PMC extinction in the NH compared to the SH. When the PMC data are combined for all years between the latitudes of 55° and 70°, we find that the northern hemisphere clouds are brighter by 29±5% and the peak altitude occurs at 0.9±0.1 km lower than the southern hemisphere clouds. In addition, we find that PMCs occur twice as frequently in the northern hemisphere. Seasonal distributions of PMC extinction and occurrence frequency for the combined multi-year datasets reveal an offset between the two hemispheres with the SH season starting about 10 days earlier than for the NH. Interhemispheric PMC altitude differences are supported by a lower altitude region of saturation in the NH and by a lower H2O peak altitude in the NH. HALOE mean temperature profiles for PMC events alone reveal a colder NH up to ∼82 km, but NH and SH profile error bars overlap above this altitude. Analysis of all temperature profiles (PMC and non-PMC) measured during the high-altitude polar summer reveal a colder NH at all altitudes suggesting this as one possible cause for the observed interhemispheric differences in PMC properties. © 2006 Elsevier Ltd. All rights reserved."
"12765389800;6701659989;","Influence of increased greenhouse gases and sulphate aerosols concentration upon diurnal temperature range over Africa at the end of the 20th century",2006,"10.1029/2006GL026381","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845664829&doi=10.1029%2f2006GL026381&partnerID=40&md5=3dde5d92c7243e78ff199535fb9d94e1","In order to investigate the diurnal temperature range response under enhanced greenhouse gases and sulphate aerosols concentrations over Africa, two ensembles of 19 integrations are conducted using the ARPEGE climate model. The ensembles are forced with the same observed changes in sea surface temperature and sea-ice extents but differ in terms of the anthropogenic direct effect included. When accounting for the additional anthropogenic effect due to the direct radiative forcing, diurnal temperature range significantly decreases during the last two decades of the 20th century over Africa. Over North and Southern Africa, this decrease is related to a significant increase of minimum temperatures mainly due to the additional greenhouse effect. Over West Africa, an increase of cloud albedo causes the daily maximum temperature to decrease resulting in a weakening of the diurnal temperature range. Simulated diurnal temperature ranee is then compared to the observed one to assess confidence in the results. Copyright 2006 by the American Geophysical Union."
"7003640407;56033135100;","Mesozoic climates: General circulation models and the rock record",2006,"10.1016/j.sedgeo.2006.05.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746335050&doi=10.1016%2fj.sedgeo.2006.05.013&partnerID=40&md5=30bc59887710ffcae22a792bfbe6c026","General circulation models (GCMs) use the laws of physics and an understanding of past geography to simulate climatic responses. They are objective in character. However, they tend to require powerful computers to handle vast numbers of calculations. Nevertheless, it is now possible to compare results from different GCMs for a range of times and over a wide range of parameterisations for the past, present and future (e.g. in terms of predictions of surface air temperature, surface moisture, precipitation, etc.). GCMs are currently producing simulated climate predictions for the Mesozoic, which compare favourably with the distributions of climatically sensitive facies (e.g. coals, evaporites and palaeosols). They can be used effectively in the prediction of oceanic upwelling sites and the distribution of petroleum source rocks and phosphorites. Models also produce evaluations of other parameters that do not leave a geological record (e.g. cloud cover, snow cover) and equivocal phenomena such as storminess. Parameterisation of sub-grid scale processes is the main weakness in GCMs (e.g. land surfaces, convection, cloud behaviour) and model output for continental interiors is still too cold in winter by comparison with palaeontological data. The sedimentary and palaeontological record provides an important way that GCMs may themselves be evaluated and this is important because the same GCMs are being used currently to predict possible changes in future climate. The Mesozoic Earth was, by comparison with the present, an alien world, as we illustrate here by reference to late Triassic, late Jurassic and late Cretaceous simulations. Dense forests grew close to both poles but experienced months-long daylight in warm summers and months-long darkness in cold snowy winters. Ocean depths were warm (8 °C or more to the ocean floor) and reefs, with corals, grew 10° of latitude further north and south than at the present time. The whole Earth was warmer than now by 6 °C or more, giving more atmospheric humidity and a greatly enhanced hydrological cycle. Much of the rainfall was predominantly convective in character, often focused over the oceans and leaving major desert expanses on the continental areas. Polar ice sheets are unlikely to have been present because of the high summer temperatures achieved. The model indicates extensive sea ice in the nearly enclosed Arctic seaway through a large portion of the year during the late Cretaceous, and the possibility of sea ice in adjacent parts of the Midwest Seaway over North America. The Triassic world was a predominantly warm world, the model output for evaporation and precipitation conforming well with the known distributions of evaporites, calcretes and other climatically sensitive facies for that time. The message from the geological record is clear. Through the Phanerozoic, Earth's climate has changed significantly, both on a variety of time scales and over a range of climatic states, usually baldly referred to as ""greenhouse"" and ""icehouse"", although these terms disguise more subtle states between these extremes. Any notion that the climate can remain constant for the convenience of one species of anthropoid is a delusion (although the recent rate of climatic change is exceptional). © 2006 Elsevier B.V. All rights reserved."
"7005231450;","Recent climatology, variability, and trends in global surface humidity",2006,"10.1175/JCLI3816.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748314787&doi=10.1175%2fJCLI3816.1&partnerID=40&md5=4f26d232951b597eace9ecf202a23dfa","In situ observations of surface air and dewpoint temperatures and air pressure from over 15 000 weather stations and from ships are used to calculate surface specific (q) and relative (RH) humidity over the globe (60°S-75°N) from December 1975 to spring 2005. Seasonal and interannual variations and linear trends are analyzed in relation to observed surface temperature (T) changes and simulated changes by a coupled climate model [namely the Parallel Climate Model (PCM)] with realistic forcing. It is found that spatial patterns of long-term mean q are largely controlled by climatological surface temperature, with the largest q of 17-19 g kg-1 in the Tropics and large seasonal variations over northern mid- and high-latitude land. Surface RH has relatively small spatial and interannual variations, with a mean value of 75%-80% over most oceans in all seasons and 70%-80% over most land areas except for deserts and high terrain, where RH is 30%-60%. Nighttime mean RH is 2%-15% higher than daytime RH over most land areas because of large diurnal temperature variations. The leading EOFs in both q and RH depict long-term trends, while the second EOF of q is related to the El Niño-Southern Oscillation (ENSO). During 1976-2004, global changes in surface RH are small (within 0.6% for absolute values), although decreasing trends of -0.11% ∼ -0.22% decade-1 for global oceans are statistically significant. Large RH increases (0.5%-2.0% decade-1) occurred over the central and eastern United States, India, and western China, resulting from large q increases coupled with moderate warming and increases in low clouds over these regions during 1976-2004. Statistically very significant increasing trends are found in global and Northern Hemispheric q and T. From 1976 to 2004, annual q (T) increased by 0.06 g kg-1 (0.16°C) decade-1 globally and 0.08 g kg-1 (0.20°C) decade-1 in the Northern Hemisphere, while the Southern Hemispheric q trend is positive but statistically insignificant. Over land, the q and T trends are larger at night than during the day. The largest percentage increases in surface q (∼1.5% to 6.0% decade-1) occurred over Eurasia where large warming (∼0.2° to 0.7°C decade-1) was observed. The q and T trends are found in all seasons over much of Eurasia (largest in boreal winter) and the Atlantic Ocean. Significant correlation between annual q and T is found over most oceans (r = 0.6-0.9) and most of Eurasia (r = 0.4-0.8), whereas it is insignificant over subtropical land areas. RH-T correlation is weak over most of the globe but is negative over many arid areas. The q-T anomaly relationship is approximately linear so that surface q over the globe, global land, and ocean increases by ∼4.9%, 4.3 %, and 5.7% per 1°C warming, respectively, values that are close to those suggested by the Clausius-Clapeyron equation with a constant RH. The recent q and T trends and the q-T relationship are broadly captured by the PCM; however, the model overestimates volcanic cooling and the trends in the Southern Hemisphere. © 2006 American Meteorological Society."
"14041650700;6602600493;","Seasonal climate sensitivity to the sea-ice cover in an intermediate complexity AGCM",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746084058&partnerID=40&md5=7e1a56b1f30799214215aa6ac73ca330","The sensitivity of the atmospheric circulation to a different specification of sea-ice temperature and its seasonal cycle is analysed from the 50-year long integrations with SPEEDY, an intermediate complexity atmospheric general circulation model (AGCM). This impact is inferred from the difference between model atmospheric states obtained with and without the inclusion of the thermodynamic effects of sea ice. The two experiments with sea ice were made - the first one used climatological monthly mean temperatures for sea ice (derived from ERA-15 data), whereas in the second experiment the sea-ice temperature was determined by a thermodynamic model embedded into the SPEEDY code. It is shown that the thermodynamic model tends to amplify the seasonal cycle of temperature. In the boreal winter, the inclusion of the thermodynamic model for sea-ice temperature leads to a general cooling of the model atmosphere at high latitudes (when compared with the experiment with climatological sea ice), associated with the reduction in geopotential heights and the strengthening of zonal winds. It also reduces the extent and amount of cloud cover in the mid- and high latitudes. Atmospheric cooling could be directly linked to the increased sea-ice seasonal cycle, because the increased albedo over sea ice reduces incoming solar radiation and further stabilises already cold air. Some of the changes induced by sea ice extend throughout the whole depth of the model atmosphere and could be linked directly to strong meridional differential temperature gradients. In addition, some seasonally varying symmetry between the Northern and the Southern Hemisphere is also found. In summer when the receding sea ice is included in model integration, the opposite effects are seen: differential temperature gradients are of the opposite sign, the atmosphere is warmed thus effecting a reduction in zonal winds and an increase in cloudiness. These effects are stronger in amplitude than those associated with the maximum winter extent of sea ice, suggesting that ocean heat flux from the ice-free water together with increased solar radiation and convection bear a strong mark on the model atmosphere."
"7601318782;7004540083;6602844274;","Comparison of different global information sources used in surface radiative flux calculation: Radiative properties of the near-surface atmosphere",2006,"10.1029/2005JD006873","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751076261&doi=10.1029%2f2005JD006873&partnerID=40&md5=24222d8657c13781f83cf759a7bda7ba","Direct estimates of surface radiative fluxes that resolve regional and weather-scale variability over the whole globe with reasonable accuracy have only become possible with the advent of extensive global, mostly satellite, data sets within the past couple of decades. The accuracy of these fluxes, estimated to be about 10-15 W/m2, is largely limited by the uncertainties of the input data sets. This study presents a fuller, more quantitative evaluation of these uncertainties, mainly for the near-surface air temperature and humidity, by comparing the main available global data sets from the European Centre for Medium-Range Weather Forecasts, NASA, the National Centers for Environmental Prediction, the International Satellite Cloud Climatology Project (ISCCP) and the Laboratoire de Météorologie Dynamique that are treated as ensemble realizations of actual climate such that their differences represent an estimate of the uncertainty in their measurements (because we do not know the absolute truth). The results are globally representative and may be taken as a generalization of our previous ISCCP-based uncertainty estimates for the input data sets. Near-surface atmospheric properties have the primary role in determining the surface downward longwave (LW) flux. From this study, the most important quantity, the surface air temperature, has a uncertainty of about 2-4 K (3 K on average), which would easily induce about 15 W/m2 uncertainty for surface downward LW flux. The humidity profile comparison suggests an uncertainty of 20-25% for the atmospheric column precipitable water below the 300 hPa level, which would cause ≲ 10 W/m2 uncertainty for surface downward LW flux, making it the second largest source of uncertainty. The comparison for the difference between surface skin and air temperature shows its uncertainty is about 2-3 K, which translates into 10-15 W/m2 uncertainty for surface net LW flux. The used atmospheric data set from ISCCP represents the diurnal variations better than the other available sources (as it was designed to do) and the synoptic variations only slightly better than the other sources, but it still has notable clear-cloudy sky biases and interannual variations that are dominated by spurious changes introduced by methodology changes in the original TOVS product. In a companion paper, the work is extended to evaluate the uncertainties of surface radiative properties. Copyright 2006 by the American Geophysical Union."
"7003543851;7005808242;","An assessment of climate feedbacks in coupled ocean-atmosphere models",2006,"10.1175/JCLI3799.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646848186&doi=10.1175%2fJCLI3799.1&partnerID=40&md5=8f288d7d65067b95eb42729e1932a7cc","The climate feedbacks in coupled ocean-atmosphere models are compared using a coordinated set of twenty-first-century climate change experiments. Water vapor is found to provide the largest positive feedback in all models and its strength is consistent with that expected from constant relative humidity changes in the water vapor mixing ratio. The feedbacks from clouds and surface albedo are also found to be positive in all models, while the only stabilizing (negative) feedback comes from the temperature response. Large intermodel differences in the lapse rate feedback are observed and shown to be associated with differing regional patterns of surface warming. Consistent with previous studies, it is found that the vertical changes in temperature and water vapor are tightly coupled in all models and, importantly, demonstrate that intermodel differences in the sum of lapse rate and water vapor feedbacks are small. In contrast, intermodel differences in cloud feedback are found to provide the largest source of uncertainty in current predictions of climate sensitivity. © 2006 American Meteorological Society."
"24467868900;55939316400;55576515800;","Changes in land surface temperatures and NDVI values over Europe between 1982 and 1999",2006,"10.1016/j.rse.2006.03.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744999214&doi=10.1016%2fj.rse.2006.03.011&partnerID=40&md5=22b57d582da988e571972b433ab86f41","We used land surface temperature (LST) algorithms and NDVI values to estimate changes in vegetation in the European continent between 1982 and 1999 from the Pathfinder AVHRR Land (PAL) dataset. These two parameters are monitored through HANTS (Harmonic ANalysis of Time Series) software, which allows the simultaneous observation of mean value, first harmonic amplitude and phase behaviors in the same image. These results for each complete year of data show the effect of volcanic aerosols and orbital drift on PAL data. Comparison of time series of HANTS cloud-free time series with the original time series for various land cover proves that this software is useful for LST analysis, although primarily designed for NDVI applications. Comparison of yearly averages of HANTS LST over the whole Europe with air temperature confirms the validity of the results. Maps of the evolution for both parameters between periods 1982/1986 and 1995/1999 have been elaborated: NDVI data show the well confirmed trend of increase over Europe (up to 0.1 in NDVI), Southern Europe seeing a decrease in NDVI (- 0.02). LST averages stay stable or slightly decrease (up to - 1.5 K) over the whole continent, except for southern areas for which the increase is up to 2.5 K. These results evidence that arid and semi-arid areas of Southern Europe have become more arid, the rest of Europe seeing an increase in its wood land proportion, while seasonal amplitude in Northern Europe has decreased. © 2006 Elsevier Inc. All rights reserved."
"14009374600;7409077047;7404865258;","A direct method for estimating net surface shortwave radiation from MODIS data",2006,"10.1016/j.rse.2006.04.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744986754&doi=10.1016%2fj.rse.2006.04.008&partnerID=40&md5=0add2de711e86173c1bb16812dc97325","The Net Surface Shortwave Radiation (NSSR) is of primary interest in climate research because it controls the total energy exchange between the atmosphere and the land/ocean surface. The conventional methods for estimating NSSR rely on broadband satellite data such as Earth Radiation Budget Experiment (ERBE) wide-field-of-view planetary albedo. The spatial resolution of the current ERBE satellite data having nadir footprints larger than 30 km is too coarse. The primary objective of this study is to estimate NSSR using multispectral narrowband data such as Moderate Resolution Imaging Spectroradiometer (MODIS) data. A direct method was developed for narrowband-to-broadband albedo conversion, which links the narrowband apparent reflectance at the Top Of Atmosphere (TOA) to shortwave broadband albedo for clear and cloudy skies without performing any surface angular modeling. The conversion coefficients were derived as functions of the secant Viewing Zenith Angle (VZA) for a given Solar Zenith Angle (SZA) and a given interval of Relative Azimuth angle (RAA). The result of comparing the values of estimated MODIS TOA shortwave broadband albedos with those of the Clouds and the Earth's Radiant Energy System (CERES) data indicated that this direct method could predict TOA shortwave broadband albedo accurately with Root Mean Square (RMS) error between CERES observations and the estimated instantaneous MODIS TOA albedos less than 0.02. Based on more accurate radiative transfer model MODTRAN 4, the parameterization coefficients of Masuda et al. for the estimation of the NSSR from TOA broadband albedo were recalculated. The result showed that the coefficients should be categorized by land surfaces, ocean surface and snow/ice surface, respectively. Finally, the NSSR estimated from MODIS data was compared with the measurements of meteorological data for an extended period of time covering all seasons in a year 2003. The RMS error is less than 20 W/m2 for clear skies and 35 W/m2 for cloudy skies. © 2006 Elsevier Inc. All rights reserved."
"21935606200;14623368100;56537237200;7403906746;","Computationally efficient expressions for the collision efficiency between electrically charged aerosol particles and cloud droplets",2006,"10.1256/qj.05.125","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746591324&doi=10.1256%2fqj.05.125&partnerID=40&md5=6c14f0d81c4d53e532d9c635c31f1426","A multiple factor parametrization is described to permit the efficient calculation of collision efficiency (E) between electrically charged aerosol particles and neutral cloud droplets in numerical models of cloud and climate. The four-parameter representation summarizes the results obtained from a detailed microphysical model of E, which accounts for the different forces acting on the aerosol in the path of failing cloud droplets. The parametrization's range of validity is for aerosol particle radii of 0.4 to 10 μm, aerosol particle densities of 1 to 2.0 g cm-3, aerosol particle charges from neutral to 100 elementary charges and drop radii from 18.55 to 142 μm. The parametrization yields values of E well within an order of magnitude of the detailed model's values, from a dataset of 3978 E values. Of these values 95% have modelled to parametrized ratios between 0.5 and 1.5 for aerosol particle sizes ranging between 0.4 and 2.0 μm, and about 96% in the second size range. This parametrization speeds up the calculation of E by a factor of ∼103 compared with the original microphysical model, permitting the inclusion of electric charge effects in numerical cloud and climate models. © Royal Meteorological Society, 2006."
"7102882592;15724295200;","Geomagnetic modulation of clouds effects in the Southern Hemisphere Magnetic Anomaly through lower atmosphere cosmic ray effects",2006,"10.1029/2006GL026389","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845609095&doi=10.1029%2f2006GL026389&partnerID=40&md5=28487e397c65bef09d673f8bfe644c8b","The study of the physical processes that drive the variability of the Earth's climate system is one of the most fascinating and challenging topics of research today. Perhaps the largest uncertainties in our ability to predict climate change are the cloud formation process and the interaction of clouds with radiation. Here we show that in the southern Pacific Ocean cloud effects on the net radiative flux in the atmosphere are related to the intensity of the Earth's magnetic field through lower atmosphere cosmic ray effects. In the inner region of the Southern Hemisphere Magnetic Anomaly (SHMA) it is observed a cooling effect of approximately 18 W/m2 while in the outer region it is observed a heating effect of approximately 20 W/m2. The variability in the inner region of the SHMA of the net radiative flux is correlated to galactic cosmic rays (GCRs) flux observed in Huancayo, Peru (r = 0.73). It is also observed in the correlation map that the correlation increases in the inner region of the SHMA. The geomagnetic modulation of cloud effects in the net radiative flux in the atmosphere in the SHMA is, therefore, unambiguously due to GCRs and/or highly energetic solar proton particles effects. Copyright 2006 by the American Geophysical Union."
"56316474800;7004940109;35857960400;6701427386;","Effects of an assumed cosmic ray-modulated low global cloud cover on the Earth's temperature",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746413329&partnerID=40&md5=63f547eb704b5713d92e36c882639c26","We have used the Thermodynamic Model of the Climate to estimate the effect of variations in the low cloud cover on the surface temperature of the Earth in the Northern Hemisphere during the period 1984-1994. We assume that the variations in the low cloud cover are proportional to the variation of the cosmic ray flux measured during the same period. The results indicate that the effect in the surface temperature is more significant in the continents, where for July of 1991, we have found anomalies of the order of 0.7 °C for the southeastern of Asia and 0.5 °C for the northeast of México. For an increase of 0.75% in the low cloud cover, the surface temperature computed by the model in the North Hemisphere presents a decrease of ∼0.11 °C; however, for a decrease of 0.90% in the low cloud cover, the model gives an increase in the surface temperature of ∼0.15 °C, these two cases correspond to a climate sensitivity factor of 0.14 °C/Wm-2, which is almost half of the climate sensitivity factor for the case of forcing by duplication of atmospheric CO2. These decreases or increases in surface temperature by increases or decreases in low clouds cover are ten times greater than the overall variability of the non-forced model time series."
"7402612084;","Does model sensitivity to changes in CO2 provide a measure of sensitivity to other forcings?",2006,"10.1175/JCLI3791.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746848476&doi=10.1175%2fJCLI3791.1&partnerID=40&md5=f9c0e68be552238d72174dfffe4c0ca6","Simulation of both the climate of the twentieth century and a future climate change requires taking into account numerous forcings, while climate sensitivities of general circulation models are defined as the equilibrium surface warming due to a doubling of atmospheric CO2 concentration. A number of simulations with the Massachusetts Institute of Technology (MIT) climate model of intermediate complexity with different forcings have been carried out to study to what extent sensitivity to changes in CO2 concentration (SCO2) represent sensitivities to other forcings. The MIT model, similar to other models, shows a strong dependency of the simulated surface warming on the vertical structure of the imposed forcing. This dependency is a result of ""semidirect"" effects in the simulations with localized tropospheric heating. A method for estimating semidirect effects associated with different feedback mechanisms is presented. It is shown that forcing that includes these effects is a better measure of expected surface warming than a forcing that accounts for stratospheric adjustment only. Simulations with the versions of the MIT model with different strengths of cloud feedback show that, for the range of sensitivities produced by existing GCMs, SCO2 provides a good measure of the model sensitivity to other forcings. In the case of strong cloud feedback, sensitivity to the increase in CO2 concentration overestimates model sensitivity to both negative forcings, leading to the cooling of the surface and ""black carbon""-like forcings with elevated heating. This is explained by the cloud feedback being less efficient in the case of increasing sea ice extent and snow cover or by the above-mentioned semidirect effects, which are absent in the CO2 simulations, respectively. © 2006 American Meteorological Society."
"7101726289;57199296506;","Seasonal cycle of Martian climate: Experimental data and numerical simulation",2006,"10.1134/S001095250604006X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33747670176&doi=10.1134%2fS001095250604006X&partnerID=40&md5=ae8eab150bfe5ea86e6c234fd4aa6709","The most adequate theoretical method of investigating the present-day Martian climate is numerical simulation based on a model of general circulation of the atmosphere. First and foremost, such models encounter the greatest difficulties in description of aerosols and clouds, which in turn essentially influence temperature fields, the atmosphere circulation, and transport of water in the atmosphere. On the basis of the method of moments, we proposed and implemented as a model of general circulation of the Martian atmosphere a mathematical tool which allows one to calculate ab initio microphysical processes in water clouds and their macroscopic properties. We present some examples of comparing the model with the data of recent Martian missions and consider the influence of separate elements of the climate system on the seasonal hydrologic cycle of the planet. © Pleiades Publishing, Inc., 2006."
"15070038800;57192107995;7006347751;","Aerosol chemistry and climate: Laboratory studies of the carbonate component of mineral dust and its reaction products",2006,"10.1029/2006GL026386","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845667384&doi=10.1029%2f2006GL026386&partnerID=40&md5=a936ca7ed5652b1cc4d90a7a7da0e0c0","The hygroscopicity, cloud condensation nucleation (CCN) activity and infrared optical extinction of CaCO3, a reactive component of mineral dust aerosol, and Ca(NO3)2, a product of atmospherically-aged CaCO3 through reaction with nitrogen oxides, have been measured. The hygroscopic growth and CCN activity of Ca(NO 3)2 are orders of magnitude greater than CaCO3 and more similar to ammonium sulfate. Ca(NO3)2 particles also reflect a greater amount of near infrared radiation at higher relative humidity. These measurements provide the first quantitative assessment of the important changes in climate forcing that can occur as mineral dust aerosol is transported, reacted and aged in the atmosphere. Copyright 2006 by the American Geophysical Union."
"22956930200;7005137442;","Using microwave observations to assess large-scale control of free tropospheric water vapor in the mid-latitudes",2006,"10.1029/2006GL026240","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845642073&doi=10.1029%2f2006GL026240&partnerID=40&md5=c86d80ae512216bd3e27ef108554ca65","The hypothesis of large scale control of midlatitude water vapor is evaluated through reconstructions of the water vapor field using a Lagrangian advectioncondensation model without microphysics or diffusion. The reconstruction is validated against satellite observations in the 183.31 ± 1 GHz band from the AMSU-B radiometer following a model-to-satellite approach. Because microwave radiation can penetrate clouds, the validation can be performed for cloudy as well as clear sky scenes, with the exception of very cold or precipitating clouds, which are screened out. The results show very good agreement between the simulated top of the atmosphere radiation and the observations, in clear as well as cloudy regions, with a general bias of less than 2K. The results suggest that cloud microphysics and small scale mixing play at most a secondary role in determining midlatitude free tropospheric humidity except perhaps indirectly through their effect on large scale circulation. Copyright 2006 by the American Geophysical Union."
"55576251200;38362385200;7006159471;7103079019;7005447447;7102197889;7404614089;10739772300;7102292241;55703127400;7103313899;7201496735;7404830554;9249605700;7003884902;6603215444;9249590200;56239324000;34974040400;8584085100;49161131000;7005808524;57206012251;7201997905;7202873880;55471445000;56068376200;24462694900;10144630800;57203440119;57201282288;56269368100;7201588628;55628567265;","Aeolian dust experiment on climate impact: An overview of Japan-China joint project ADEC",2006,"10.1016/j.gloplacha.2006.03.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745008470&doi=10.1016%2fj.gloplacha.2006.03.001&partnerID=40&md5=f5f908fcb3270a3d07b2ba5e6769e2b3","The Aeolian Dust Experiment on Climate Impact (ADEC) was initiated in April 2000 as a joint five-year Japan-China project. The goal was to understand the impact of aeolian dust on climate via radiative forcing (RF). Field experiments and numerical simulations were conducted from the source regions in northwestern China to the downwind region in Japan in order to understand wind erosion processes temporal and spatial distribution of dust during their long-range transportation chemical, physical, and optical properties of dust and the direct effect of radiative forcing due to dust. For this, three intensive observation periods (IOP) were conducted from April 2002 to April 2004. The in situ and network observation results are summarized as follows: (1) In situ observations of the wind erosion process revealed that the vertical profile of moving sand has a clear size dependency with height and saltation flux and that threshold wind velocity is dependent on soil moisture. Results also demonstrated that saltation flux is strongly dependent on the parent soil size distribution of the desert surface. (2) Both lidar observations and model simulations revealed a multiple dust layer in East Asia. A numerical simulation of a chemical transport model, CFORS, illustrated the elevated dust layer from the Taklimakan Desert and the lower dust layer from the Gobi Desert. The global-scale dust model, MASINGAR, also simulated the dust layer in the middle to upper free troposphere in East Asia, which originated from North Africa and the Middle East during a dust storm in March 2003. Raman lidar observations at Tsukuba, Japan, found the ice cloud associated with the dust layer at an altitude of 6 to 9 km. Analysis from lidar and the radio-sonde observation suggested that the Asian dust acted as ice nuclei at the ice-saturated region. These results suggest the importance of dust's climate impact via the indirect effect of radiative forcing due to the activation of dust into ice nuclei. (3) Studies on the aerosol concentration indicated that size distributions of aerosols in downwind regions have bimodal peaks. One peak was in the submicron range and the other in the supermicron range. The main soluble components of the supermicron peak were Na+, Ca2+, NO3-, and Cl-. In the downwind region in Japan, the dust, sea salt, and a mixture of the two were found to be dominant in coarse particles in the mixed boundary layer. (4) Observation of the optical properties of dust by sky-radiometer, particle shoot absorption photometer (PSAP), and Nephelometer indicated that unpolluted dust at source region has a weaker absorption than originally believed. A sensitivity experiment of direct RF by dust indicated that single scattering albedo is the most important of the optical properties of dust and that the sensitivity of instantaneous RF in the shortwave region at the top of the atmosphere to the refractive index strongly depends on surface albedo. A global scale dust model, MASINGAR, was used for evaluation of direct RF due to dust. The results indicated the global mean RF at the top and the bottom of the atmosphere were - 0.46 and - 2.13 W m- 2 with cloud and were almost half of the RF with cloud-free condition. © 2006 Elsevier B.V. All rights reserved."
"35494005000;7202652226;57213733545;","Cirrus clouds and the large-scale atmospheric state: Relationships revealed by six years of ground based data",2006,"10.1175/JCLI3786.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746798047&doi=10.1175%2fJCLI3786.1&partnerID=40&md5=bd6198a5c3d83b2dda4e5ff4ac677ce7","The properties of cirrus clouds observed at the Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) in Oklahoma are documented from a nearly continuous 6-yr record of 35-GHz cloud radar data. Cirrus frequency over the ACRF is 23% and 28% of the time in the warm (May-September) and cold seasons (November-March), respectively, with maxima and minima during the period studied of 30% and 16% in the warm season and 34% and 24% in the cold seasons. Cirrus, as defined here, reveal a seasonal oscillation in their macroscale properties that can be traced to the seasonal deepening of the troposphere in the Southern Plains region. While the average bulk microphysical properties do not change significantly from season to season, the variability of certain parameters demonstrates seasonal change. It is shown that the properties of cirrus clouds vary perceptively with the large-scale vertical motion. Using NCEP-NCAR reanalysis data to define the large-scale meteorological state when cirrus are observed at the ACRF, the authors find that cirrus tend to exist within a maximum in upper-tropospheric humidity and downstream of the peak upper-tropospheric vertical motion. Cirrus that exist in large-scale ascent upstream of the synoptic-scale middle-tropospheric ridge axis are shown to have higher water contents than cirrus that exist in large-scale subsidence downstream of the ridge axis, although the overall nature of the statistical distributions of water contents do not change greatly, suggesting that it may be difficult to parameterize the properties of cirrus based solely on large-scale vertical motion. The layer-mean particle size, on the other hand, shows no such sensitivity to the large-scale vertical motion. © 2006 American Meteorological Society."
"6505932008;6507731482;25953950400;7004715270;6603385031;","Impacts of nucleating aerosol on Florida storms. Part I: Mesoscale simulations",2006,"10.1175/JAS3713.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746932441&doi=10.1175%2fJAS3713.1&partnerID=40&md5=0c54bec73c402d46e83a6645b9fefd72","Toward the end of the Cirrus Regional Study of Tropical Anvils and Cirrus Layer-Florida Area Cirrus Experiment (CRYSTAL-FACE) field campaign held during July 2002, high concentrations of Saharan dust, which can serve as cloud condensation nuclei (CCN), giant CCN (GCCN), and ice-forming nuclei (IFN) were observed over the peninsula of Florida. To investigate the impacts of enhanced aerosol concentrations on the characteristics of convective storms and their subsequent anvil development, sensitivity tests are conducted using the Regional Atmospheric Modeling System (RAMS) model, in which the initialization profiles of CCN, GCCN, and IFN concentrations are varied. These variations are found to have significant effects on the storm dynamics and microphysical processes, as well as on the surface precipitation. Updrafts are consistently stronger as the aerosol concentrations are increased. The anvils cover a smaller area but are better organized and have larger condensate mixing ratio maxima in the cases with greater aerosol concentrations. Cloud water mass tends to increase with increasing aerosol concentrations, with enhanced GCCN concentrations having the most significant influence. Increasing either the GCCN or IFN concentrations produces the most rainfall at the surface whereas enhanced CCN concentrations reduce surface rainfall. Higher IFN concentrations produce ice at warmer temperatures and deeper anvils, but simultaneously increasing the concentrations of CCN and GCCN leads to more supercooled liquid water available for freezing and greater ice mixing ratios. Graupel mixing ratios decrease and hail mixing ratios increase with increasing aerosol concentrations. Higher concentrations of GCCN and IFN result in greater accumulated surface precipitation initially. By the end of the simulation period, however, the accumulated precipitation is the greatest for the case in which the aerosol concentrations are lowest. Such changes in the dynamical and microphysical characteristics of convective storms as a result of the variations in aerosol concentrations have potential climate consequences, both through cloud radiative effects and the hydrological cycle. The impacts of varying CCN, GCCN, and IFN concentrations on the anvils will be discussed more fully in Part II. © 2006 American Meteorological Society."
"7406423537;7202456388;7005000019;7101783397;35588596400;","Changes in DMS production and flux in relation to decadal shifts in ocean circulation",2006,"10.1111/j.1600-0889.2006.00183.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745028817&doi=10.1111%2fj.1600-0889.2006.00183.x&partnerID=40&md5=976bf8140318a2f223634e7fb179bcfe","A fundamental question is are the biological processes regulating dimethylsulphide (DMS) production by the marine ecosystem interconnected and responding to atmospheric or ocean signals at decadal timescales? Related to this is a need to quantify how climate change affects these interconnections and understand the expected levels of natural variability on decadal timescales. To explore this we have used indicators of climate variability [the Gulf Stream North Wall (GSNW) and the North Atlantic Oscillation (NAO) indices] as probes to demonstrate that a marine ecosystem model, incorporating DMS production, can extract and amplify a climatic signal, which is spread across a variety of meteorological variables. The GSNW signal is imparted through the wind and cloud forcing, despite the fact there was not significant relationship observed between the GSNW index and the meteorological forcing data. The model simulations appear to reproduce observed decadal variability in phytoplankton community structure in the eastern North Atlantic and imply that DMS(P) biogeochemistry may vary on decadal timescales as a consequence of changes in community structure. The GSNW index is a potential indicator of such changes and there may have been a regime shift in DMSP production in the eastern North Atlantic coincident with that observed for plankton. Sensitivity analysis indicates that the impact of climate variability on DMS biogeochemistry may potentially be damped by the ability of microbial communities to adapt physiologically to the effects of changes in light and nutrients. Copyright © Blackwell Munksgaard, 2006."
"14519137000;7201926991;7004315126;7004372407;7102490770;6602272789;6602489366;15751749200;","Seasonal and interannual variations of diurnal cycles of wind and cloud activity observed at Serpong, west Jawa, Indonesia",2006,"10.2151/jmsj.84A.171","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748444900&doi=10.2151%2fjmsj.84A.171&partnerID=40&md5=1407d445705a38024c1549e979eb52c9","In this paper, the seasonal changes in the diurnal variations of wind and the cloud activity at Serpong (106.7°E, 6.4°S), near Jakarta, are climatologically described. In the dry season (May-October), diurnal variation of wind accompanied with sea-land breeze circulation was prominent. In the rainy season (November-April), the diurnal variation was consistent with sea-land breeze circulation, but was not as clear as that in the dry season. The peak time of the northerly in the rainy season, similarly to that of the sea breezes at Serpong in the low level (below 1.0 km height), was earlier than that in the dry season. The maximum time in the climatological diurnal variation of the surface temperature at Serpong in the rainy season was earlier than that in the dry season. The vertical structure which was consistent with sea breeze circulation was clearer when the prevailing (daily-mean) wind was weaker in the rainy season. These results are consistent with the features of the local circulation; in other words, the local circulation depend on the diurnal variation of surface temperature and its prominent when the prevailing wind is weak. The typical diurnal variation of the wind in the rainy season was unclear when the prevailing northwesterly to westerly was strong around Serpong. Interannual variation of the diurnal variation could be detected in the transitional period from the dry to the rainy season. Cloud activity had prominent diurnal variation over West Jawa in the rainy season and was active in the early evening over land, particularly, in the mountainous area in the south of Serpong. When cloud activity was active over the mountainous areas, the northerly below 1.0 km in height was prominent at Serpong, which is consistent with the feature that the development of local cloud system is accompanied with local circulation. © 2006, Meteorological Society of Japan."
[No author id available],"Global atmospheric pollution forum. Atmospheric pollution: Developing a global approach",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247376456&partnerID=40&md5=4ee672076dc0a79678061f03affd2105","Prior to the 1970s atmospheric pollution was considered to be a local, urban, problem that was best tackled through national or local initiatives. As scientific knowledge increased, it became clear that emissions to the atmosphere were also leading to significant transboundary problems through the long-range transport of pollutants. Such regional impacts of sulphur and nitrogen compounds were clearly problems which no one country could tackle on its own. It is now clear that transboundary pollution is an important issue in all parts of the globe and some pollutants are travelling hemispherically and globally with issues such as the Atmospheric Brown Cloud coming to the fore. The transfer of pollutants across the Northern Hemisphere, especially of tropospheric ozone, is now a significant issue affecting the ability of regions to tackle the pollution problems through activities within their region alone. Carbon monoxide from biomass burning is an issue across the Southern Hemisphere. In addition, there are an increasing number of atmospheric pollutant problems that have a global dimension such as the transfer of persistent organic pollutants (POPs) and mercury and interactions with global climate balance through the increase in aerosol concentrations in the atmosphere leading to a ""global dimming"". The emission, transport and transformation, and deposition of long-range transboundary air pollution is having dramatic impacts on human health and well-being, economies, livelihoods, ecosystem integrity and productivity in all parts of the globe. The question is: how can we develop systems that can comprehensively tackle these emerging issues? The Global Atmospheric Pollution Forum was established to encourage wider debate and innovative solutions to the challenges of air pollution at the regional, hemispheric and global scales. This summary discussion document derives from a series of inter-regional dialogues for scientists and administrators held during 2005. It is a working document intended to elicit views and suggestions."
"55879681300;57192912623;","Regional climate change and its impact on photooxidant concentrations in southern Germany: Simulations with a coupled regional climate-chemistry model",2006,"10.1029/2005JD006748","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750611791&doi=10.1029%2f2005JD006748&partnerID=40&md5=35d7c9c21337af2badced7307a536a0f","In order to investigate possible effects of global climate change on the near-surface concentrations of photochemical compounds in southern Germany, nested regional simulations with a coupled climate-chemistry model were carried out. The simulations with a horizontal resolution of 60 km for Europe and 20 km for central Europe were driven by meteorological boundary conditions provided by a long-term simulation of the global climate model ECHAM4. Two time slices of about 10 years were compared, one representing the 1990s and one representing the 2030s. For the region of southern Germany the simulations show an increase of the mean summer temperature by almost 2° along with a decrease of cloud water and ice and a corresponding increase of the photolysis frequencies and the emissions of biogenic hydrocarbons. Under the model assumption of unchanged anthropogenic emissions this leads to an increase of the mean mixing ratios of most photooxidants. Because of the complex topography and the heterogeneous distribution of precursor emissions all parameters show pronounced regional patterns. The average daily maximum ozone concentrations in southern Germany increase for the considered scenario by nearly 10% in the summer months. Depending on the region, the increase of the mean daily maximum ranges between 2 and 6 ppb. As a consequence, the number of days when the 8-hour mean of the ozone concentration exceeds the threshold value of 120 μg m-3 increases by 5 to 12 days per year. Copyright 2006 by the American Geophysical Union."
"16029719200;7004299063;6701413579;35612904200;56249704400;7004214645;15053007900;","Modeling the distribution of the volcanic aerosol cloud from the 1783-1784 Laki eruption",2006,"10.1029/2005JD006899","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750617042&doi=10.1029%2f2005JD006899&partnerID=40&md5=de7eafaf03a73918fdcae644728b462b","We conducted simulations of the atmospheric transformation and transport of the emissions of the 1783-1784 Laki basaltic flood lava eruption (64.10°N, 17.15°W) using the NASA Goddard Institute for Space Studies modelE climate model coupled to a sulfur cycle chemistry model. The model simulations successfully reproduced the aerosol clouds of the 1912 Katmai and 1991 Mount Pinatubo eruptions, giving us confidence in the Laki simulations. Simulations of the Laki eruption produce peak zonal mean sulfate (SO<inf>4</inf>) concentrations of over 70 ppbv during August and into September 1783 in the upper troposphere and lower stratosphere at high latitudes. While the majority of the sulfate aerosol was removed during the fall and early winter, a significant aerosol perturbation remained into 1784. The peak SO<inf>2</inf> gas loading was just over 37 megatons (Mt) in late June with the sulfate loading peaking in late August 1783 at 60 Mt over the average of 3 runs. This yielded a peak sulfate aerosol (75% H<inf>2</inf>SO<inf>4</inf>, 25% H<inf>2</inf>O) loading of over 80 Mt with the total aerosol produced during the entire eruption being about 165 Mt. The resulting sulfate deposition compares well with ice cores taken across Greenland. The top of atmosphere net radiative forcing peaks at -27 W/m2 over the high latitudes during late summer 1783 and produces a global mean forcing of -4 W/m2. The model results confirm that Northern Hemisphere high-latitude volcanic eruptions produce aerosols that remain mostly confined north of 30°N latitude. Copyright 2006 by the American Geophysical Union."
"8570871900;6603400519;","Linking snowpack microphysics and albedo evolution",2006,"10.1029/2005JD006834","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750623275&doi=10.1029%2f2005JD006834&partnerID=40&md5=cd073bd7fd6ae82296f3ee1fc41b15fa","Snow aging causes reflectance to vary significantly on timescales of days. This variability influences the strength of snow albedo feedback and can affect the timing of snowmelt. However, climate models have yet to incorporate important controls on snow aging and albedo evolution. We develop a physically based model that predicts evolution of dry, pure snow specific surface area, and apply aspherical ice particle theory to link these results with albedo evolution. This is the first theoretical study to quantify the relative roles of initial size distribution, vertical temperature gradient, and snow density in snow albedo evolution. Vapor diffusion caused by curvature differences causes rapid albedo decay in the first day following snowfall. Vertical temperature gradient generally dominates grain growth processes afterward but is modulated by snow density, irregularity in particle spacing, and temperature. These processes operate as a coupled system, which we uniquely represent without abrupt transitions between regimes. Model results agree very well with measurements of isothermal snow evolution and are within reasonable range of temperature gradient observations. We show that different snow state regimes cause albedo of nonmelting snow surfaces with identical initial albedo to vary by 0.12 or more after 14 days. Lack of quality observational data illuminates the need for well-controlled snow studies that simultaneously monitor specific surface area, temperature gradient, and albedo. Accounting for snow aging processes, especially temperature gradient, will improve understanding and assessment of snow albedo feedback and climate sensitivity. The modeling framework we develop will also be useful for air-snow chemistry studies that consider specific surface area. Copyright 2006 by the American Geophysical Union."
"56611366900;7005862399;7005263785;55740664200;","Generalized threshold function accounting for effect of relative dispersion on threshold behavior of autoconversion process",2006,"10.1029/2005GL025500","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746467497&doi=10.1029%2f2005GL025500&partnerID=40&md5=c116243b56f49bfe0732007bccb69df9","The recently derived theoretical threshold function associated with the autoconversion process is generalized to account for the effect of the relative dispersion of the cloud droplet size distribution. This generalized threshold function theoretically demonstrates that the relative dispersion, which has been largely neglected to date, essentially controls the cloud-to-rain transition if the liquid water content and the droplet concentration are fixed. Comparison of the generalized threshold function to existing ad hoc threshold functions further reveals that the essential role of the spectral shape of the cloud droplet size distribution in rain initiation has been unknowingly buried in the arbitrary use of ad hoc threshold functions in atmospheric models such as global climate models, and that commonly used ad hoc threshold functions are unable to fully describe the threshold behavior of the autoconversion process that likely occurs in ambient clouds. Copyright 2006 by the American Geophysical Union."
"35494005000;7202652226;56493740900;","Cloud radiative forcing at the Atmospheric Radiation Measurement Program Climate Research Facility: 2. Vertical redistribution of radiant energy by clouds",2006,"10.1029/2005JD005922","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746550253&doi=10.1029%2f2005JD005922&partnerID=40&md5=497bd8603a663d96558e9c079a11e96a","Documentation of the effects of clouds on the radiant energy balance of the surface and atmosphere represents a shortcoming in the set of observations that are needed to ascertain the validity of climate model simulations. While clouds are known to cool the climate system from top of atmosphere (TOA) radiation budget studies, the redistribution of energy between the surface and atmosphere and within the atmosphere by clouds has not been examined in detail with observations. Using data collected at the Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) site, we use measurements of cloud occurrence and structure together with a scheme to characterize the cloud microphysical and radiative properties to estimate the uncertainty in our ability to calculate the radiative forcing and effect of clouds at the top of atmosphere, the surface and within the atmosphere. We find that overcast clouds during 2000 tended to have a small net influence on the atmosphere (6 W m-2 ± 3 W m-2 of heating) with net TOA and surface cooling (25 W m-2 ± 3 W m-2 and 32 ± 3 W m-2, respectively). These statistics mask a significant redistribution of radiant energy within the atmosphere by clouds where low overcast clouds resulted in strong atmospheric cooling (37 W m-2 ± 9 W m-2), and thin high clouds resulted in warming (21 W m-2 ± 6 W m-2) Suggesting that accurate prediction of the phasing of these cloud types within meteorological features is important for capturing the essential feedbacks by clouds to the general circulation. Copyright 2006 by the American Geophysical Union."
"6701754792;14049802000;6602137606;8206969400;7006577245;23017945100;6506416572;","Impact of conditional sampling and instrumental limitations on the statistics of cloud properties derived from cloud radar and lidar at SIRTA",2006,"10.1029/2005GL025340","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746398913&doi=10.1029%2f2005GL025340&partnerID=40&md5=1d7865fbf54293d44365e4314b90dd67","Clouds represent the largest uncertainty in future climate projections. As a result, unbiased long-term vertically-resolved cloud observations must be collected and analyzed in order to produce regional cloud climatologies. In the present study, we use model outputs to evaluate the impact of conditional temporal sampling and instrumental effects on the 2-year statistics of frequency of cloud occurrence and cloud fraction. We then quantify the radiative significance of the ice clouds undetected by cloud radars. We find that in order to evaluate the representation of all types of clouds in operational models both a cloud radar and a lidar must be used. The cloud radar alone can do a reasonable job at describing cloud properties up to 8-9 km, however the lidar is mandatory to detect most of the high-altitude clouds above 9 km. The sampling should be regular but not necessarily continuous, and should not be driven by meteorological conditions. This result applies to all sites having a lidar without a radome. It is finally suggested that a cloud radar of around -60 dBZ sensitivity at 1 km range would be required to detect almost all radiatively-significant ice clouds. Copyright 2006 by the American Geophysical Union."
"23027811500;7005449794;","Forest on the edge: Seasonal cloud forest in Oman creates its own ecological niche",2006,"10.1029/2006GL026022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746433986&doi=10.1029%2f2006GL026022&partnerID=40&md5=91c5eefafb643fed8e5b6265e8abf85a","Cloud forests usually grow in the moist tropics where water is not a limiting factor to plant growth. Here, for the first time, we describe the hydrology of a water limited seasonal cloud forest in the Dhofar mountains of Oman. This ecosystem is under significant stress from camels feeding on tree canopies. The Dhofar forests are the remnants of a moist vegetation belt, which once spread across the Arabian Peninsula. According to our investigation the process of cloud immersion during the summer season creates within this desert a niche for moist woodland vegetation. Woodland vegetation survives in this ecosystem, sustained through enhanced capture of cloud water by their canopies (horizontal precipitation). Degraded land lacks this additional water source, which inhibits re-establishment of trees. Our modeling results suggest that cattle feeding may lead to irreversible destruction of one of the most diverse ecosystems in Arabia. Copyright 2006 by the American Geophysical Union."
"56652365500;6701843355;","Shifts in ENSO coupling processes under global warming",2006,"10.1029/2006GL026196","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746418902&doi=10.1029%2f2006GL026196&partnerID=40&md5=ed80c513ec04d810d36dba3f4d913192","Global warming may shift the properties and dynamics of El Niño. We study the shifts in ENSO couplings in IPCC-AR4 coupled general circulation climate models. First, we compare period, pattern, amplitude and mean state of the Pacific Ocean between the current climate and a high CO2 climate. Next, shifts in ENSO couplings between sea surface temperature (SST), thermocline depth and wind stress are discussed. Although the mean state shifts, the overall ENSO properties do not change much. Changes in the mean state affect the feedback loop. Higher mean SST provides higher damping through cloud feedback. The shallower thermocline and mixed layer depth increase SST sensitivity to thermocline variability and wind stress. Wind response to SST variability increases where the mean SST has increased the most. However, the higher damping and more stable atmosphere compensate the other changes and the residual change in ENSO properties is relatively small. Copyright 2006 by the American Geophysical Union."
"35494005000;7202652226;14052911500;56493740900;7004057920;7006783796;7004198777;6602550636;7401796996;7402480218;14053374800;6603546080;","Cloud radiative forcing at the Atmospheric Radiation Measurement Program Climate Research Facility: 1. technique, validation, and comparison to satellite-derived diagnostic quantities",2006,"10.1029/2005JD005921","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746472902&doi=10.1029%2f2005JD005921&partnerID=40&md5=65773899bf735de0b4050fff3fd9d298","It has been hypothesized that continuous ground-based remote sensing measurements from collocated active and passive remote sensors combined with regular soundings of the atmospheric thermodynamic structure can be combined to describe the effects of clouds on the clear sky radiation fluxes. We critically test that hypothesis in this paper and a companion paper (part 2). Using data collected at the Southern Great Plains (SGP) Atmospheric Radiation Measurement (ARM) site sponsored by the U.S. Department of Energy, we explore an analysis methodology that results in the characterization of the physical state of the atmospheric profile at time resolutions of 5 min and vertical resolutions of 90 m. The description includes thermodynamics and water vapor profile information derived by merging radiosonde soundings with ground-based data and continues through specification of the cloud layer occurrence and microphysical and radiative properties derived from retrieval algorithms and parameterizations. The description of the atmospheric physical state includes a calculation of the clear and cloudy sky solar and infrared flux profiles. Validation of the methodology is provided by comparing the calculated fluxes with top of atmosphere (TOA) and surface flux measurements and by comparing the total column optical depths to independently derived estimates. We find over a 1-year period of comparison in overcast uniform skies that the calculations are strongly correlated to measurements with biases in the flux quantities at the surface and TOA of less than 6% and median fractional errors ranging from 12% to as low as 2%. In the optical depth comparison for uniform overcast skies during the year 2000 where the optical depth varies over more than 3 orders of magnitude we find a mean positive bias of less than 1% and a 0.6 correlation coefficient. In addition to a case study where we examine the cloud radiative effects at the TOA, surface and atmosphere by a middle latitude cyclone, we examine the cloud top pressure and optical depth retrievals of ISCCP and LBTM over a period of 1 year. Using overcast periods from the year 2000, we find that the satellite algorithms tend to compare well with data overall but there is a tendency to bias cloud tops info the middle troposphere and underestimate optical depth in high optical depth events. Copyright 2006 by the American Geophysical Union."
"7402480218;7005626683;6507865754;8397494800;","Estimation of fractional sky cover from broadband shortwave radiometer measurements",2006,"10.1029/2005JD006475","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746545598&doi=10.1029%2f2005JD006475&partnerID=40&md5=d7ec8ad46af538cc74d5c64fdb1d4be7","We outline a methodology for estimating fractional sky cover for an effective 160° field of view from an analysis of surface measurements of downwelling total and diffuse shortwave (SW) irradiance. The data are screened for optically thicker overcast cases, after which an empirically derived formulation is used to estimate the fractional sky cover for the remaining data. The retrieved fractional sky cover time series is then evaluated to mitigate times of anomalous behavior caused by the thick overcast screening. The resultant sky cover estimates show a high degree of repeatability given nominally well maintained and operated radiometer systems and the use of the Long and Ackerman (2000) methodology for estimating the clear-sky total and diffuse SW. Thus the resultant fractional sky-cover estimates appear to be fairly independent of the particular climate regime and model of radiometers used, at least for the climate regimes we have tested so far. The sky-cover estimates agree to better than 10% root mean square sky cover amount with sky imager retrievals and human observations, which is as good as the agreement between sky imaging systems and observers themselves. As such, this methodology becomes a powerful tool for satellite and model validations and climatological analyses including the study of trends in cloud amount. Analysis shows that the technique also produces realistic frequency distributions, showing that the continental midlatitude regimes included in the study are typified by clear-sky occurring about 1/3 of the time, overcast about 1/3 of the time, and partly cloudy skies to varying extent occurring the remaining 1/3 of the time. By contrast, the tropical western Pacific oceanic regime during the Nauru99 field experiment exhibits far more frequent occurrence of partly cloudy skies, with sky cover amounts of 20% to 50% occurring about half the time. Copyright 2006 by the American Geophysical Union."
"22836973600;55715917500;25030776200;9272538400;6507355747;7103248807;7004028051;","Transient climate simulations with the HadGEM1 climate model: Causes of past warming and future climate change",2006,"10.1175/JCLI3731.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646356573&doi=10.1175%2fJCLI3731.1&partnerID=40&md5=a062ed8f48756717b116d628f1d4e77d","The ability of climate models to simulate large-scale temperature changes during the twentieth century when they include both anthropogenic and natural forcings and their inability to account for warming over the last 50 yr when they exclude increasing greenhouse gas concentrations has been used as evidence for an anthropogenic influence on global warming. One criticism of the models used in many of these studies is that they exclude some forcings of potential importance, notably from fossil fuel black carbon, biomass smoke, and land use changes. Herein transient simulations with a new model, the Hadley Centre Global Environmental Model version 1 (HadGEM1), are described, which include these forcings in addition to other anthropogenic and natural forcings, and a fully interactive treatment of atmospheric sulfur and its effects on clouds. These new simulations support previous work by showing that there was a significant anthropogenic influence on near-surface temperature change over the last century. They demonstrate that black carbon and land use changes are relatively unimportant for explaining global mean near-surface temperature changes. The pattern of warming in the troposphere and cooling in the stratosphere that has been observed in radiosonde data since 1958 can only be reproduced when the model includes anthropogenic forcings. However, there are some discrepancies between the model simulations and radiosonde data, which are largest where observational uncertainty is greatest in the Tropics and high latitudes. Predictions of future warming have also been made using the new model. Twenty-first-century warming rates, following policy-Televant emissions scenarios, are slightly greater in HadGEM1 than in the Third Hadley Centre Coupled Ocean-Atmosphere General Circulation Model (HadCM3) as a result of the extra forcing in HadGEM1. An experiment in which greenhouse gases and other anthropogenic forcings are stabilized at 2100 levels and held constant until 2200 predicts a committed twenty-second-century warming of less than 1 K, whose spatial distribution resembles that of warming during the twenty-first century, implying that the local feedbacks that determine the pattern of warming do not change significantly."
"57203540849;7004029924;27168081700;55895105500;","Influences of the Atlantic warm pool on western hemisphere summer rainfall and Atlantic hurricanes",2006,"10.1175/JCLI3770.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646370641&doi=10.1175%2fJCLI3770.1&partnerID=40&md5=f838603db6674f526904c95923b6b4a8","The Atlantic warm pool (AWP) of water warmer than 28.5°C comprises the Gulf of Mexico, the Caribbean Sea, and the western tropical North Atlantic (TNA). The AWP reaches its maximum size around September, with large AWPs being almost 3 times larger than small ones. Although ENSO teleconnections are influential on the AWP, about two-thirds of the large and small AWP variability appears unrelated to ENSO. The AWP is usually geographically different from the TNA; however, the AWP size is correlated with the TNA SST anomalies. During August to October, large AWPs and warm TNA are associated with increased rainfall over the Caribbean, Mexico, the eastern subtropical Atlantic, and the southeast Pacific, and decreased rainfall in the northwest United States, Great Plains, and eastern South America. In particular, rainfall in the Caribbean, Central America, and eastern South America from August to October is mainly related to the size of the AWP. Large (small) AWPs and warm (cold) TNA correspond to a weakening (strengthening) of the northward surface winds from the AWP to the Great Plains that disfavors (favors) moisture transport for rainfall over the Great Plains. On the other hand, large (small) AWPs and warm (cold) TNA strengthen (weaken) the summer regional Atlantic Hadley circulation that emanates from the warm pool region into the southeast Pacific, changing the subsidence over the southeast Pacific and thus the stratus cloud and drizzle there. The large AWP, associated with a decrease in sea level pressure and an increase in atmospheric convection and cloudiness, corresponds to a weak tropospheric vertical wind shear and a deep warm upper ocean, and thus increases Atlantic hurricane activity."
"7005814217;35984036000;6602688130;6603901951;6602558284;7801492228;","CCSM-CAM3 climate simulation sensitivity to changes in horizontal resolution",2006,"10.1175/JCLI3764.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745088918&doi=10.1175%2fJCLI3764.1&partnerID=40&md5=b0b4a430ec907373f01bf48d9dea58ba","The latest version of the Community Climate System Model (CCSM) Community Atmosphere Model version 3 (CAM3) has been released to allow for numerical integration at a variety of horizontal resolutions. One goal of the CAM3 design was to provide comparable large-scale simulation fidelity over a range of horizontal resolutions through modifications to adjustable coefficients in the parameterized treatment of clouds and precipitation. Coefficients are modified to provide similar cloud radiative forcing characteristics for each resolution. Simulations with the CAM3 show robust systematic improvements with higher horizontal resolution for a variety of features, most notably associated with the large-scale dynamical circulation. This paper will focus on simulation differences between the two principal configurations of the CAM3, which differ by a factor of 2 in their horizontal resolution. © 2006 American Meteorological Society."
"7005513582;7201520140;7005814217;56520921400;","The climate sensitivity of the Community Climate System Model version 3 (CCSM3)",2006,"10.1175/JCLI3747.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646374791&doi=10.1175%2fJCLI3747.1&partnerID=40&md5=6cfde91a54b9998d7f8bb3b3358b9a31","The climate sensitivity of the Community Climate System Model (CCSM) is described in terms of the equilibrium change in surface temperature due to a doubling of carbon dioxide in a slab ocean version of the Community Atmosphere Model (CAM) and the transient climate response, which is the surface temperature change at the point of doubling of carbon dioxide in a 1% yr-1 CO2 simulation with the fully coupled CCSM. For a fixed atmospheric horizontal resolution across model versions, we show that the equilibrium sensitivity has monotonically increased across CSM1.4, CCSM2, to CCSM3 from 2.01° to 2.27° to 2.47°C, respectively. The transient climate response for these versions is 1.44° to 1.09° to 1.48°C, respectively. Using climate feedback analysis, it is shown that both clear-sky and cloudy-sky processes have contributed to the changes in transient climate response. The dependence of these sensitivities on horizontal resolution is also explored. The equilibrium sensitivity of the high-resolution (T85) version of CCSM3 is 2.71°C, while the equilibrium response for the low-resolution model (T31) is 2.32°C. It is shown that the shortwave cloud response of the high-resolution version of the CCSM3 is anomalous compared to the low-and moderate-resolution versions. © 2006 American Meteorological Society."
"56520921400;6602558284;6603805048;7005557215;7004479957;7006245928;7403573190;35498837200;7005814217;36246081300;7005513582;7006739521;7103178094;7004222705;57201972361;","The Community Climate System Model version 3 (CCSM3)",2006,"10.1175/JCLI3761.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744490657&doi=10.1175%2fJCLI3761.1&partnerID=40&md5=9e11c62e01a917a1cd37d0ae918d83ba","The Community Climate System Model version 3 (CCSM3) has recently been developed and released to the climate community. CCSM3 is a coupled climate model with components representing the atmosphere, ocean, sea ice, and land surface connected by a flux coupler. CCSM3 is designed to produce realistic simulations over a wide range of spatial resolutions, enabling inexpensive simulations lasting several millennia or detailed studies of continental-scale dynamics, variability, and climate change. This paper will show results from the configuration used for climate-change simulations with a T85 grid for the atmosphere and land and a grid with approximately 1° resolution for the ocean and sea ice. The new system incorporates several significant improvements in the physical parameterizations. The enhancements in the model physics are designed to reduce or eliminate several systematic biases in the mean climate produced by previous editions of CCSM. These include new treatments of cloud processes, aerosol radiative forcing, land-atmosphere fluxes, ocean mixed layer processes, and sea ice dynamics. There are significant improvements in the sea ice thickness, polar radiation budgets, tropical sea surface temperatures, and cloud radiative effects. CCSM3 can produce stable climate simulations of millennial duration without ad hoc adjustments to the fluxes exchanged among the component models. Nonetheless, there are still systematic biases in the ocean-atmosphere fluxes in coastal regions west of continents, the spectrum of ENSO variability, the spatial distribution of precipitation in the tropical oceans, and continental precipitation and surface air temperatures. Work is under way to extend CCSM to a more accurate and comprehensive model of the earth's climate system. © 2006 American Meteorological Society."
"7202660824;7403288995;","Assessing snow albedo feedback in simulated climate change",2006,"10.1175/JCLI3750.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645801809&doi=10.1175%2fJCLI3750.1&partnerID=40&md5=d46bf630212c3801b339c1b66059cbdc","In this paper, the two factors controlling Northern Hemisphere springtime snow albedo feedback in transient climate change are isolated and quantified based on scenario runs of 17 climate models used in the Intergovernmental Panel on Climate Change Fourth Assessment Report. The first factor is the dependence of planetary albedo on surface albedo, representing the atmosphere's attenuation effect on surface albedo anomalies. It is potentially a major source of divergence in simulations of snow albedo feedback because of large differences in simulated cloud fields in Northern Hemisphere land areas. To calculate the dependence, an analytical model governing planetary albedo was developed. Detailed validations of the analytical model for two of the simulations are shown, version 3 of the Community Climate System Model (CCSM3) and the Geophysical Fluid Dynamics Laboratory global coupled Climate Model 2.0 (CM2.0), demonstrating that it facilitates a highly accurate calculation of the dependence of planetary albedo on surface albedo given readily available simulation output. In all simulations it is found that surface albedo anomalies are attenuated by approximately half in Northern Hemisphere land areas as they are transformed into planetary albedo anomalies. The intermodel standard deviation in the dependence of planetary albedo on surface albedo is surprisingly small, less than 10% of the mean. Moreover, when an observational estimate of this factor is calculated by applying the same method to the satellite-based International Satellite Cloud Climatology Project (ISCCP) data, it is found that most simulations agree with ISCCP values to within about 10%, despite further disagreements between observed and simulated cloud fields. This suggests that even large relative errors in simulated cloud fields do not result in significant error in this factor, enhancing confidence in climate models. The second factor, related exclusively to surface processes, is the change in surface albedo associated with an anthropogenically induced temperature change in Northern Hemisphere land areas. It exhibits much more intermodel variability. The standard deviation is about 1/3 of the mean, with the largest value being approximately 3 times larger than the smallest. Therefore this factor is unquestionably the main source of the large divergence in simulations of snow albedo feedback. To reduce the divergence, attention should be focused on differing parameterizations of snow processes, rather than intermodel variations in the attenuation effect of the atmosphere on surface albedo anomalies. © 2006 American Meteorological Society."
"7003684963;7006705919;7005814217;14013504500;","Representation of clouds and precipitation processes in the Community Atmosphere Model version 3 (CAM3)",2006,"10.1175/JCLI3749.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744483795&doi=10.1175%2fJCLI3749.1&partnerID=40&md5=b9f47e64a73f13f51528ce7240214af1","The parameterizations of clouds and precipitation processes have been revised considerably in the Community Atmosphere Model version 3 (CAM3) compared to its predecessors, CAM2 and the Community Climate Model version 3 (CCM3). The parameterizations in CAM3 are more realistic in their representation of processes affecting cloud liquid and ice particles and represent the linkages between processes more completely. This paper describes the changes to the representation of clouds in CAM3, including the partitioning of cloud water between liquid and ice phases, the determination of particle sizes and sedimentation rates, the phase and evaporation rate of precipitation, and the calculation of the cloud fraction. Parameterization changes between CCM3 and CAM2 introduced a significant cold bias at the tropical tropopause, resulting in a dry bias for stratospheric water vapor. Tests of the sensitivity of the tropical temperature profile and the tropical tropopause temperature to individual process changes suggested that the radiative balance at the tropopause was altered by improvements in both clouds and relative humidity below. Radiative equilibrium calculations suggested that the cold bias could be removed by improving the representation of subvisible, cirrus clouds. These results motivated the complete separation of the representation of liquid and ice cloud particles and an examination of the processes that determine their sources and sinks. As a result of these changes, the tropopause cold bias has been almost eliminated in CAM3. The total cloud condensate variable, used in CAM2, has been separated into cloud liquid and cloud ice variables in CAM3. Both sedimentation and large-scale transport of the condensate variables are now included. Snowfall is computed explicitly and the latent heat of fusion has been included for all freezing and melting processes. Both deep and shallow convection parameterizations now detrain cloud condensate directly into the stratiform clouds instead of evaporating the detrained condensate into the environment. The convective parameterizations are not easily modified to include the latent heat of fusion. Therefore, the determination of the phase of convective precipitation, and of detrained condensate, is added as a separate step. Evaporation is included for sedimenting cloud particles and for all sources of precipitation. © 2006 American Meteorological Society."
"14024348500;7102829666;55505923400;","Small-scale cloud activity over the Maritime Continent and the Western Pacific as revealed by satellite data",2006,"10.1175/MWR3132.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745442967&doi=10.1175%2fMWR3132.1&partnerID=40&md5=ec97489cbc9807e21ca385e5c5618b2e","Cloud systems over the Maritime Continent and the tropical western Pacific defined by the Geostationary Meteorological Satellite (GMS) were tracked, and their evolution was compared with cloud parameters [e.g., minimum blackbody brightness temperature (TBB), cloud area size, TBB gradient at cloud edges]. In addition, cloud systems observed by the Tropical Rainfall Measuring Mission (TRMM) were examined, and the relationship with precipitation was investigated. Analysis areas were divided into four regions: open ocean, coastal sea, coasts, and land. Cloud systems that did not split from or merge with other systems (28% of a total of 290 717 cloud systems) showed common features on cloud parameters in spite of different lifetimes or their locations. While the minimum TBB appeared in the beginning of their lifetimes, the cloud area was still expanding. At the time of first detection, the TBB gradient at the edge of the cloud system was the maximum and decreased with time. The rain rate was maximized when the TBB was at a minimum or earlier. For example, a system with the lifetime of 5 h over the ocean has a minimum TBB 2 h after the occurrence, a maximum area at 3 h, a maximum TBB gradient at 1 h, and a maximum rain rate at 1 h. Vertical development was significant in coasts, while remarkable horizontal expansion appeared over land. In particular, precipitation ice and storm height profiles showed differences among regions. © 2006 American Meteorological Society."
"6602833930;6603238282;6507880319;","The role of sublimational cooling in a late-season midwestern snow event",2006,"10.1175/WAF919.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745829417&doi=10.1175%2fWAF919.1&partnerID=40&md5=e2beaf2d48f66e05385d1448560eb65e","Analysis is provided of a surprise late-season snow event over eastern Missouri and western Illinois. While snow totals failed to exceed 15 cm (6 in.) at any single location, the system was noteworthy because of the poor performance of public, private, and media forecasts in anticipating the event. Using observed data and a successful simulation with a mesoscale numerical model, the event is scrutinized to determine the forcing mechanisms for the precipitation over a small area. A region of enhanced frontogenesis is diagnosed over the region both in the observed data as well as the model output. That the precipitation fell as snow is shown to be the result of a dry layer of air between the surface and the cloud base that saturated and cooled due largely to snow sublimation-evaporation in just a few hours to permit the fall of snow uninhibited from the cloud base to the ground. © 2006 American Meteorological Society."
"7003803916;8565323700;7006711251;38461378900;7005794379;7004372407;15823290900;55398698300;7201926991;","Multiscale aspects of convective systems associated with an intraseasonal oscillation over the Indonesian Maritime Continent",2006,"10.1175/MWR3152.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646447061&doi=10.1175%2fMWR3152.1&partnerID=40&md5=015a67d13dbba60658301b9ed3dbe14f","Multiscale aspects of convective systems over the Indonesian Maritime Continent in the convectively active phase of an intraseasonal oscillation (ISO) during November 2002 are studied using Geostationary Meteorological Satellite infrared data and ground-based observational data from X-band rain radar, equatorial atmosphere radar, L-band boundary layer radar, and upper-air soundings at Koto Tabang (KT; 0.20°S, 100.32°E; 865 m above mean sea level), West Sumatera, Indonesia. In the analysis period, four super cloud clusters (SCCs; horizontal scale of 2000-4000 km), associated with an ISO, are seen to propagate eastward from the eastern Indian Ocean to the Indonesian Maritime Continent. The SCCs are recognized as envelopes of convection, composed of meso-α-scale cloud clusters (MαCCs; horizontal scale of 500-1000 km) propagating westward. When SCCs reach the Indonesian Maritime Continent, the envelopes disappear but MαCCs are clearly observed. Over Sumatera, the evolution and structure of a distinct MαCC is closely related to the organization of localized cloud systems with a diurnal cycle. The cloud systems are characterized by westward-propagating meso-β-scale cloud clusters (MβCCs; horizontal scale of ∼100 km) developed in eastern Sumatera, and an orographic cloud system formed over a mountain range in western Sumatera. Ground-based observations further revealed the internal structure of the orographic cloud system around KT. A meso-β-scale convective precipitation system with eastward propagation (E-MβCP; horizontal scale of ∼40 km) is found with the formation of the orographic cloud system. This is associated with a low-level wind change from easterly to westerly, considered to be local circulation over the mountain range. The E-MβCP also indicates a multicell structure composed of several meso-γ-scale convective precipitation systems (horizontal scale of <10 km) with multiple evolution stages (formation, development, and dissipation). © 2006 American Meteorological Society."
"56520921400;7006705919;7003684963;7005814217;14013504500;7402435469;6603451961;6602558284;57208455668;55745955800;","The formulation and atmospheric simulation of the Community Atmosphere Model version 3 (CAM3)",2006,"10.1175/JCLI3760.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744472524&doi=10.1175%2fJCLI3760.1&partnerID=40&md5=05b26ed082f7f763f7889263693681d3","A new version of the Community Atmosphere Model (CAM) has been developed and released to the climate community. CAM Version 3 (CAM3) is an atmospheric general circulation model that includes the Community Land Model (CLM3), an optional slab ocean model, and a thermodynamic sea ice model. The dynamics and physics in CAM3 have been changed substantially compared to implementations in previous versions. CAM3 includes options for Eulerian spectral, semi-Lagrangian, and finite-volume formulations of the dynamical equations. It supports coupled simulations using either finite-volume or Eulerian dynamics through an explicit set of adjustable parameters governing the model time step, cloud parameterizations, and condensation processes. The model includes major modifications to the parameterizations of moist processes, radiation processes, and aerosols. These changes have improved several aspects of the simulated climate, including more realistic tropical tropopause temperatures, boreal winter land surface temperatures, surface insolation, and clear-sky surface radiation in polar regions. The variation of cloud radiative forcing during ENSO events exhibits much better agreement with satellite observations. Despite these improvements, several systematic biases reduce the fidelity of the simulations. These biases include underestimation of tropical variability, errors in tropical oceanic surface fluxes, underestimation of implied ocean heat transport in the Southern Hemisphere, excessive surface stress in the storm tracks, and offsets in the 500-mb height field and the Aleutian low. © 2006 American Meteorological Society."
"7402333910;7401693308;57203406068;6602439986;26031912400;6603031108;7403459291;7401776640;55477039800;7103399784;","Extratropical atmosphere-ocean variability in CCSM3",2006,"10.1175/JCLI3743.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745105638&doi=10.1175%2fJCLI3743.1&partnerID=40&md5=a7c9beee441c43da7e132b43c8bb4644","Extratropical atmosphere-ocean variability over the Northern Hemisphere of the Community Climate System Model version 3 (CCSM3) is examined and compared to observations. Results are presented for an extended control integration with a horizontal resolution of T85 (1.4°) for the atmosphere and land and ∼1° for the ocean and sea ice. Several atmos pheric phenomena are investigated including storms, clouds, and patterns of variability, and their relationship to both tropical and extratropical SST anomalies. The mean storm track, the leading modes of storm track variability, and the relationship of the latter to tropical and midlatitude sea surface temperature (SST) anomalies are fairly well simulated in CCSM3. The positive correlations between extratropical SST and low-cloud anomalies in summer are reproduced by the model, but there are clear biases in the relationship between clouds and the near-surface meridional wind. The model accurately represents the circulation anomalies associated with the jet stream waveguide, the Pacific-North American (PNA) pattern, and fluctuations associated with the Aleutian low, including how the latter two features are influenced by the El Niño-Southern Oscillation (ENSO). CCSM3 has a reasonable depiction of the Pacific decadal oscillation (PDO), but it is not strongly connected to tropical Pacific SSTs as found in nature. There are biases in the position of the North Atlantic Oscillation (NAO) and other Atlantic regimes, as the mean Icelandic low in CCSM3 is stronger and displaced southeastward relative to observations. Extratropical ocean processes in CCSM3, including upper-ocean mixing, thermocline variability, and extratropical to tropical flow within the thermocline, also influence climate variability. As in observations, the model includes the ""reemergence mechanism"" where seasonal variability in mixed layer depth (MLD) allows SST anomalies to recur in consecutive winters without persisting through the intervening summer. Remote wind stress curl anomalies drive thermocline variability in the Kuroshio-Oyashio Extension region, which influences SST, surface heat flux anomalies, and the local wind field. The interior ocean pathways connecting the subtropics to the equator in both the Pacific and Atlantic are less pronounced in CCSM3 than in nature or in ocean-only simulations forced by observed atmospheric conditions, and the flow from the subtropical North Atlantic does not appear to reach the equator through either the western boundary or interior pathways. © 2006 American Meteorological Society."
"7006518289;7005965757;7004222705;56520921400;6701508272;7202699757;7402207328;55259660400;9845516300;6701581880;","Climate change projections for the twenty-first century and climate change commitment in the CCSM3",2006,"10.1175/JCLI3746.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645214285&doi=10.1175%2fJCLI3746.1&partnerID=40&md5=b2665c6bac2c5facc2d4cac63dd636e2","Climate change scenario simulations with the Community Climate System Model version 3 (CCSM3), a global coupled climate model, show that if concentrations of all greenhouse gases (GHGs) could have been stabilized at the year 2000, the climate system would already be committed to 0.4°C more warming by the end of the twenty-first century. Committed sea level rise by 2100 is about an order of magnitude more, percentage-wise, compared to sea level rise simulated in the twentieth century. This increase in the model is produced only by thermal expansion of seawater, and does not take into account melt from ice sheets and glaciers, which could at least double that number. Several tenths of a degree of additional warming occurs in the model for the next 200 yr in the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) B1 and A1B scenarios after stabilization in the year 2100, but with twice as much sea level rise after 100 yr, and doubling yet again in the next 100 yr to 2300. At the end of the twenty-first century, the warming in the tropical Pacific for the A2, A1B, and B1 scenarios resembles an El Niño-like response, likely due to cloud feedbacks in the model as shown in an earlier version. Greatest warming occurs at high northern latitudes and over continents. The monsoon regimes intensify somewhat in the future warmer climate, with decreases of sea level pressure at high latitudes and increases in the subtropics and parts of the midlatitudes. There is a weak summer midlatitude soil moisture drying in this model as documented in previous models. Sea ice distributions in both hemispheres are somewhat over-extensive, but with about the right ice thickness at the end of the twentieth century. Future decreases in sea ice with global warming are proportional to the temperature response from the forcing scenarios, with the high forcing scenario, A2, producing an ice-free Arctic in summer by the year 2100. © 2006 American Meteorological Society."
"15043174300;7101936669;","Seasonal climate summary southern hemisphere (winter 2005): Neutral conditions in the tropical Pacific and a wet and warm winter across Australia",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749653098&partnerID=40&md5=3d9c81fc0e38492b34290acee1be2b28","Southern hemisphere circulation patterns and associated anomalies are reviewed for the austral winter (June - August) 2005. Emphasis is given to the Pacific Basin climate indicators and Australian rainfall and temperature patterns. After a very dry start to the year, winter rainfall was above normal. In June, the Australian area-averaged rainfall was 44.5 mm (91 per cent above normal), the sixth-highest June rainfall on record and the highest since 1951. Overall, Australian winter rainfall was the highest since the 1998 La Niña event. Despite increased rainfall and hence cloudiness, maximum temperatures continued to be above average over virtually the entire continent. Large areas of eastern, northern and central Australia experienced minimum temperatures between 1°C and 3°C warmer than average during winter with peak anomalies of between +3°C and +4°C over parts of central Queensland. Following neutral conditions during autumn, both atmospheric and oceanic ENSO indicators were generally neutral throughout the winter."
"7006705919;55435769200;6507370012;7005231450;7101736036;24722339600;7003684963;7102645933;7005814217;","A characterization of tropical transient activity in the CAM3 atmospheric hydrologic cycle",2006,"10.1175/JCLI3752.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745074947&doi=10.1175%2fJCLI3752.1&partnerID=40&md5=a3fecfa371db74459ac695dd0779373b","The Community Atmosphere Model version 3 (CAM3) is the latest generation of a long lineage of general circulation models produced by a collaboration between the National Center for Atmospheric Research (NCAR) and the scientific research community. Many aspects of the hydrological cycle have been changed relative to earlier versions of the model. It is the goal of this paper to document some aspects of the tropical variability of clouds and the hydrologic cycle in CAM3 on time scales shorter than 30 days and to discuss the differences compared to the observed atmosphere and earlier model versions, with a focus on cloud-top brightness temperature, precipitation, and cloud liquid water path. The transient behavior of the model in response to changes in resolution to various numerical methods used to solve the equations for atmospheric dynamics and transport and to the underlying lower boundary condition of sea surface temperature and surface fluxes has been explored. The ratio of stratiform to convective rainfall is much too low in CAM3, compared to observational estimates. It is much higher in CAM3 (10%) than the Community Climate Model version 3 (CCM3; order 1%-2%) but is still a factor of 4-5 too low compared to observational estimates. Some aspects of the model transients are sensitive to resolution. Higher-resolution versions of CAM3 show too much variability (both in amplitude and spatial extent) in brightness temperature on time scales of 2-10 days compared to observational estimates. Precipitation variance is underestimated on time scales from a few hours to 10 days, compared to observations over ocean, although again the biases are reduced compared to previous generations of the model. The diurnal cycle over tropical landmasses is somewhat too large, and there is not enough precipitation during evening hours. The model tends to produce maxima in precipitation and liquid water path that are a few hours earlier than that seen in the observations over both oceans and land. © 2006 American Meteorological Society."
"55883036400;7003627420;6701724255;","Climatic instability in west equatorial Africa during the Mid- and Late Holocene",2006,"10.1016/j.quaint.2006.01.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33747335945&doi=10.1016%2fj.quaint.2006.01.008&partnerID=40&md5=e0d602fd7c948834c7fecf6e5826edf6","Millennial-scale climatic variations have punctuated the Holocene characterised by abrupt changes from warm to cool or wetter to drier conditions. Amongst these climatic events, there is increased evidence for an abrupt multicentennial shift of climatic conditions around 3.8/3.7 kyr BP (4.1 cal. kyr BP) in mid- to low-latitude regions which had a profound impact on landscape and population migration. In the Mediterranean region, subtropical, tropical and equatorial Africa, a number of continental proxies (lake-levels, pollen sequences, stable isotopes) record this abrupt change towards drier conditions. However, regionalism in climatic conditions is reflected in the vegetation records, possibly in relation to orographic conditions and the influence of sea-surface conditions. Hitherto there have been very few marine sequences that record this particular climatic shift at high-resolution. We present here new data from the Congo deep-sea fan containing integrated marine and terrestrial proxies. Around 5-4 cal. kyr BP, shifts in surface conditions off the Congo River mouth are observed, with possible establishment of seasonal coastal upwelling, and lower sea-surface temperatures. In parallel, pollen data indicate fluctuations of herbaceous, afromontane taxa and charred grass cuticles, suggesting more open vegetation in the lowland regions and an increase in cloud forest and/or afromontane vegetation at higher altitudes within the Congolese region. © 2006 Elsevier Ltd and INQUA."
"24331295800;7006248174;35571173100;56229316900;","The effects of sea-ice and land-snow concentrations on planetary albedo from the earth radiation budget experiment",2006,"10.3137/ao.440206","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745598552&doi=10.3137%2fao.440206&partnerID=40&md5=5e43b1eb742f98461028d4ef283f84c6","The high-latitude ice/snow-albedo feedback is a principal element in many paleoclimate theories and global warming scenarios. The strength of this feedback is determined by the ice/snow effects on the top-of-atmosphere (TOA) albedo, which is also strongly affected by clouds. Using currently available satellite observations, we estimate the radiative effectiveness (RE) of ice and snow with regards to the TOA albedo, which we define as the change in the TOA albedo corresponding to changes of 0% to 100% in the ice or snow cover. The REs of the northern hemisphere (NH) sea ice, land snow, and southern hemisphere (SH) sea ice are found to be 0.22, 0.23 and 0.16, respectively. This means that, for an incident solar flux of about 400 W m-2 reaching the TOA in the polar latitudes in summer, local reduction in ice/snow concentrations from 100% to 0% will result in a decrease in reflected short wave radiation of approximately 80 W m-2. These changes in the TOA albedo are significant, yet smaller than the associated changes in the surface albedo. Comparison of the TOA albedo values with available surface albedo observations helps to identify the role of clouds in the RE of ice/snow. The analysis is based on the whole time-space domain where the sea ice and land snow appear, and reveals a remarkable similarity in the ice and snow RE in the areas with high sea-ice and land-snow cover variability, despite the varying nature of the surface cover, seasonality, and locations. These estimates provide a useful constraint to test current climate models. © Canadian Meteorological and Oceanographic Society."
"7004998184;7003705025;7005610890;","Permanent Quaternary hyperaridity in the Negev, Israel, resulting from regional tectonics blocking Mediterranean frontal systems",2006,"10.1130/G22354.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745311323&doi=10.1130%2fG22354.1&partnerID=40&md5=d150279c04440ae6f5cc280c73350e8d","Although various episodes of wet Quaternary climates have been suggested in studies of the Negev Desert, here we demonstrate that Reg soils, developed on flat alluvial surfaces and sensitive to minor changes in precipitation, indicate that the southern Negev has been permanently hyperarid at least since the middle Pleistocene. The wetter episodes were restricted to the northern Negev, currently mildly arid. Gypsic-saline Reg soils that developed on stable surfaces during &gt;200 k.y. in the southern Negev are cumulative and polygenetic, but none exhibits even the weakest development of calcic horizons. Under current climate conditions in the Negev, calcic soils are widespread in areas with rainfall &gt;80 mm yr-1. The fact that the hyperarid (&lt;50 mm yr-1) southern Negev lacks any calcic horizons indicates that it never experienced an average rainfall of ≥80 mm yr-1 during the middle-late Pleistocene, whereas the northern Negev was wetter. This Negev dichotomy is explained by the main physical features controlling rainfall over the Negev, i.e, the southward-decreasing depth of the atmospheric boundary layer with distance from the Mediterranean, and the altitude of the central Negev Highland (1000 m). The interaction between these two features often prevents the passage of rain clouds into the southern Negev. The Holocene and Pleistocene gypsic-salic soil distribution across the Negev closely matches the current circumstances. We suggest that hyperaridity has prevailed over the southern Negev since the last stages of the uplift of the central Negev Highland in the late Pliocene-early Pleistocene. © 2006 Geological Society of America."
"57203053317;35887706900;35464731600;","Disentangling the role of microphysical and dynamical effects in determining cloud properties over the Atlantic",2006,"10.1029/2005GL024625","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745713477&doi=10.1029%2f2005GL024625&partnerID=40&md5=c108a64e8be245a4a009ee17c4e1523e","MODIS satellite data reveal that over the Atlantic Ocean (20°S-30°N) in June-August 2002 indirect aerosol effects cause a decrease in the cloud top effective radius of stratiform clouds of 2.9 μm and an increase in cloud fraction of 21%, when increasing the aerosol optical thickness (AOT) from the cleanest 5 percentile to an AOT of 0.2. Thus, indirect aerosol effects are responsible for 72% (-8.8 W m-2) of the -12.2 W m-2 decrease in the shortwave radiation at the top-of-the atmosphere (TOA). Global climate model simulations with and without indirect aerosol effects confirm a decrease in TOA shortwave cloud forcing of -9 W m-2 over the Atlantic from the cleanest to the highest AOT due to indirect aerosol effects. While MODIS shows an increase in cloud fraction due to aerosols, in the model aerosols cause primarily an increase in cloud water. Thus, unlike the analysis from MODIS, the increase in cloud fraction with increasing AOT is dominated by changes in dynamical regimes, not by aerosol indirect effects. Copyright 2006 by the American Geophysical Union."
"57199936302;6506545080;35445938100;7006709050;7203034123;7004165697;7003529785;8255698000;35595682100;7102551927;6507952920;7003763119;14023953700;7201951829;","CO signatures in subtropical convective clouds and anvils during CRYSTAL-FACE: An analysis of convective transport and entrainment using observations and a cloud-resolving model",2006,"10.1029/2005JD006104","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745471712&doi=10.1029%2f2005JD006104&partnerID=40&md5=fad347c66db2cc9dfba6638a85e606f4","Convective systems are an important mechanism in the transport of boundary layer air into the upper troposphere. The Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) campaign, in July 2002, was developed as a comprehensive atmospheric mission to improve knowledge of subtropical cirrus systems and their roles in regional and global climate. In situ measurements of carbon monoxide (CO), water vapor (H<inf>2</inf>OV), and total water (H<inf>2</inf>Ot) aboard NASA's WB-57F aircraft and CO aboard the U.S. Navy's Twin Otter aircraft were obtained to study the role of convective transport. Three flights sampled convective outflow on 11, 16 and 29 July found varying degrees of CO enhancement relative to the free troposphere. A cloud-resolving model used the in situ observations and meteorological fields to study these three systems. Several methods of filtering the observations were devised here using ice water content, relative humidity with respect to ice, and particle number concentration as a means to statistically sample the model results to represent the flight tracks. A weighted histogram based on ice water content observations was then used to sample the simulations for the three flights. In addition, because the observations occurred in the convective outflow cirrus and not in the storm cores, the model was used to estimate the maximum CO within the convective systems. In general, anvil-level air parcels contained an estimated 20-40% boundary layer air in the analyzed storms. Copyright 2006 by the American Geophysical Union."
"6602185473;6603955469;35419152500;7003426743;57193559238;7202577029;","Absolute accuracy of water vapor measurements from six operational radiosonde types launched during AWEX-G and implications for AIRS validation",2006,"10.1029/2005JD006083","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745435491&doi=10.1029%2f2005JD006083&partnerID=40&md5=3c37b06d90d1e0d2d7e193a65d840c4b","A detailed assessment of radiosonde water vapor measurement accuracy throughout the tropospheric column is needed for assessing the impact of observational error on applications that use the radiosonde data as input, such as forecast modeling, radiative transfer calculations, remote sensor retrieval validation, climate trend studies, and development of climatologies and cloud and radiation parameterizations. Six operational radiosonde types were flown together in various combinations with a reference-quality hygrometer during the Atmospheric Infrared Sounder (AIRS) Water Vapor Experiment-Ground (AWEX-G), while simultaneous measurements were acquired from Raman lidar and microwave radiometers. This study determines the mean accuracy and variability of the radiosonde water vapor measurements relative to simultaneous measurements from the University of Colorado (CU) Cryogenic Frostpoint Hygrometer (CFH), a reference-quality standard of known absolute accuracy. The accuracy and performance characteristics of the following radiosonde types are evaluated: Vaisala RS80-H, RS90, and RS92; Sippican Mark IIa; Modem GL98; and the Meteolabor Snow White hygrometer. A validated correction for sensor time lag error is found to improve the accuracy and reduce the variability of upper tropospheric water vapor measurements from the Vaisala radiosondes. The AWEX data set is also used to derive and validate a new empirical correction that improves the mean calibration accuracy of Vaisala measurements by an amount that depends on the temperature, relative humidity, and sensor type. Fully corrected Vaisala radiosonde measutements are found to be suitably accurate for AIRS validation throughout the troposphere, whereas the other radiosonde types are suitably accurate under only a subset of tropospheric conditions. Although this study focuses on the accuracy of nighttime radiosonde measurements, comparison of Vaisala RS90 measurements to water vapor retrievals from a microwave radiometer reveals a 6-8% dry bias in daytime RS90 measurements that is caused by solar heating of the sensor. An AWEX-like data set of daytime measurements is highly desirable to complete the accuracy assessment, ideally from a tropical location where the full range of tropospheric temperatures can be sampled. Copyright 2006 by the American Geophysical Union."
"57198616562;57193132723;","Factors limiting convective cloud-top height at the ARM Nauru Island climate research facility",2006,"10.1175/JCLI3722.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745270578&doi=10.1175%2fJCLI3722.1&partnerID=40&md5=b075b04563ee151d06398651ba7d0198","Cumulus congestus clouds, with moderate shortwave albedos and cloud-top temperatures near freezing, occur fairly often in the Tropics. These clouds may play an important role in the evolution of the Madden-Julian oscillation and the regulation of relative humidity in the midtroposphere. Despite this importance they are not necessarily simulated very well in global climate models. Surface remote sensing observations and soundings from the Atmospheric Radiation Measurement (ARM) climate research facility at Nauru Island are coupled with a simple parcel model in order to address the following questions about these cloud types: 1) Which environmental factors play a role in determining the depth of tropical convective clouds? 2) What environmental parameters are related to entrainment rate in cumulus congestus clouds? The results presented herein suggest that at Nauru Island a drying of the midtroposphere is more likely to be responsible for limiting congestus cloud-top heights than is a stabilizing of the freezing level. It is also found that low-level CAPE and the RH profile account for the largest portion of the variance in cumulus congestus entrainment rates, consistent with the idea that entrainment rate depends on the buoyant production of turbulent kinetic energy. If the analysis is limited to cases where there is a sounding during the hour preceding the cumulus congestus observations, it is found that the low-level CAPE accounts for 85% of the total variance in entrainment rate. © 2006 American Meteorological Society."
"6603333885;7005626683;7101959253;6701346974;","Evaluation of the multiscale modeling framework using data from the Atmospheric Radiation Measurement Program",2006,"10.1175/JCLI3699.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744465029&doi=10.1175%2fJCLI3699.1&partnerID=40&md5=de245e7cb213f19db886c8952a18057c","In a recently developed approach to climate modeling, called the multiscale modeling framework (MMF), a two-dimensional cloud-resolving model (CRM) is embedded into each grid column of the Community Atmospheric Model (CAM), replacing traditional cloud and radiation parameterizations. This study presents an evaluation of the MMF through a comparison of its output with the output from the CAM and with data from two observational sites operated by the Atmospheric Radiation Measurement Program, one at the Southern Great Plains (SGP) in Oklahoma and one at the island of Nauru in the tropical western Pacific (TWP) region. Two sets of one-year-long simulations are considered: one using climatological sea surface temperatures (SSTs) and another using 1999 SST. Each set includes a run with the MMF as well as a CAM run with traditional or standard cloud and radiation treatments. Time series of cloud fraction, precipitation intensity, and downwelling solar radiation flux at the surface are analyzed. For the TWP site, the distributions of these variables from the MMF run are shown to be more consistent with observation than those from the CAM run. This change is attributed to the improved representation of convective clouds in the MMF compared to the conventional climate model. For the SGP, the MMF shows little to no improvement in predicting the same quantities. Possible causes of this lack of improvement are discussed. © 2006 American Meteorological Society."
"7404136779;12767369600;57192570834;57219367606;55872047000;7402872647;7006275544;8331328200;57217340777;","Multi-year simulations and experimental seasonal predictions for rainy seasons in China by using a nested regional climate model (RegCM_NCC). Part I: Sensitivity study",2006,"10.1261/rna.2274106","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646838377&doi=10.1261%2frna.2274106&partnerID=40&md5=098dfeb98f2ef76dc94563715923243f","A modified version of the NCAR/RegCM2 has been developed at the National Climate Center (NCC), China Meteorological Administration, through a series of sensitivity experiments and multi-year simulations and hindcasts, with a special emphasis on the adequate choice of physical parameterization schemes suitable for the East Asian monsoon climate. This regional climate model is nested with the NCC/IAP (Institute of Atmospheric Physics) T63, coupled GCM to make an experimental seasonal prediction for China and East Asia. The four-year (2001 to 2004) prediction results are encouraging. This paper is the first part of a two-part paper, and it mainly describes the sensitivity study of the physical process parameterization represented in the model. The systematic errors produced by the different physical parameterization schemes such as the land surface processes, convective precipitation, cloud-radiation transfer process, boundary layer process and large-scale terrain features have been identified based on multi-year and extreme flooding event simulations. A number of comparative experiments has shown that the mass flux scheme (MFS) and Betts-Miller scheme (BM) for convective precipitation, the LPMI (land surface process model I) and LPMII (land surface process model II) for the land surface process, the CCM3 radiation transfer scheme for cloud-radiation transfer processes, the TKE (turbulent kinetic energy) scheme for the boundary layer processes and the topography treatment schemes for the Tibetan Plateau are suitable for simulations and prediction of the East Asia monsoon climate in rainy seasons. Based on the above sensitivity study, a modified version of the RegCM2 (RegCM_NCC) has been set up for climate simulations and seasonal predictions."
"6602115068;56268127800;6603037727;6603436132;7005473082;6701498473;7103156669;6603957672;","Science objectives of the ozone monitoring instrument",2006,"10.1109/TGRS.2006.872336","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646388445&doi=10.1109%2fTGRS.2006.872336&partnerID=40&md5=0391128e2a34b3faa43018516cc0aec3","The Ozone Monitoring Instrument (OMI) flies on NASA's Earth Observing System AURA satellite, launched in July 2004. OMI is an ultraviolet/visible (UV/VIS) nadir solar backscatter spectrometer, which provides nearly global coverage in one day, with a spatial resolution of 13 km × 24 km. Trace gases measured include O3, NO2, SO2, HCHO, BrO, and OClO. In addition OMI measures aerosol characteristics, cloud top heights and cloud coverage, and UV irradiance at the surface. OMI's unique capabilities for measuring important trace gases with daily global coverage and a small footprint will make a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change along with Aura's other three instruments. OMI's high spatial resolution enables detection of air pollution at urban scales. Total Ozone Mapping Spectrometer and differential optical absorption spectroscopy heritage algorithms, as well as new ones developed by the international (Dutch, Finnish, and U.S.) OMI science team, are used to derive OMI's advanced backscatter data products. In addition to providing data for Aura's prime objectives, OMI will provide near-real-time data for operational agencies in Europe and the U.S. Examples of OMI's unique capabilities are presented in this paper. © 2006 IEEE."
"13103281000;57201570597;7004958888;36041280100;","Model simulation of meteorology and air quality during the summer PUMA intensive measurement campaign in the UK West Midlands conurbation",2006,"10.1016/j.scitotenv.2005.08.054","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646111211&doi=10.1016%2fj.scitotenv.2005.08.054&partnerID=40&md5=00d97d79bcd06fad15ad1efec209eaf8","The Regional Atmospheric Modeling System (RAMS) and Urban Airshed Model (UAM IV) have been implemented for prediction of air pollutant concentrations within the West Midlands conurbation of the United Kingdom. The modelling results for wind speed, direction and temperature are in reasonable agreement with observations for two stations, one in a rural area and the other in an urban area. Predictions of surface temperature are generally good for both stations, but the results suggest that the quality of temperature prediction is sensitive to whether cloud cover is reproduced reliably by the model. Wind direction is captured very well by the model, while wind speed is generally overestimated. The air pollution climate of the UK West Midlands is very different to those for which the UAM model was primarily developed, and the methods used to overcome these limitations are described. The model shows a tendency towards under-prediction of primary pollutant (NOx and CO) concentrations, but with suitable attention to boundary conditions and vertical profiles gives fairly good predictions of ozone concentrations. Hourly updating of chemical concentration boundary conditions yields the best results, with input of vertical profiles desirable. The model seriously underpredicts NO2 / NO ratios within the urban area and this appears to relate to inadequate production of peroxy radicals. Overall, the chemical reactivity predicted by the model appears to fall well below that occurring in the atmosphere. © 2005 Elsevier B.V. All rights reserved."
"57191598636;57193132723;","Composite analysis of winter cyclones in a GCM: Influence on climatological humidity",2006,"10.1175/JCLI3690.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644666458&doi=10.1175%2fJCLI3690.1&partnerID=40&md5=8c4be368ca165402d59590843a646119","The role of midlatitude baroclinic cyclones in maintaining the extratropical winter distribution of water vapor in an operational global climate model is investigated. A cyclone identification and tracking algorithm is used to compare the frequency of occurrence, propagation characteristics, and composite structure of 10 winters of storms in the Goddard Institute for Space Studies general circulation model (GCM) and in two reanalysis products. Cyclones are the major dynamical source of water vapor over the extratropical oceans in the reanalyses. The GCM produces fewer, generally weaker, and slower-moving cyclones than the reanalyses and is especially deficient in storms associated with secondary cyclogenesis. Composite fields show that GCM cyclones are shallower and drier aloft than those in the reanalyses and that their vertical structure is less tilted in the frontal region because of the GCM's weaker ageostrophic circulation. This is consistent with the GCM's underprediction of midlatitude cirrus. The GCM deficiencies do not appear to be primarily due to parameterization errors; the model is too dry despite producing less storm precipitation than is present in the reanalyses and in an experimental satellite precipitation dataset, and the weakness and shallow structure of GCM cyclones is already present at storm onset. These shortcomings may be common to most climate GCMs that do not resolve the mesoscale structure of frontal zones, and this may account for some universal problems in climate GCM midlatitude cloud properties."
"6602115068;6603436132;6602290588;6505897603;7102644711;55956029300;7003861526;7005693940;7003922988;","The ozone monitoring instrument",2006,"10.1109/TGRS.2006.872333","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646422253&doi=10.1109%2fTGRS.2006.872333&partnerID=40&md5=9abe6086db0055efdcda972959d1d4ea","The Ozone Monitoring Instrument (OMI) flies on the National Aeronautics and Space Adminsitration's Earth Observing System Aura satellite launched in July 2004. OMI is a ultraviolet/visible (UV/VIS) nadir solar backscatter spectrometer, which provides nearly global coverage in one day with a spatial resolution of 13 km × 24 km. Trace gases measured include O3, NO2, SO2, HCHO, BrO, and OClO. In addition, OMI will measure aerosol characteristics, cloud top heights, and UV irradiance at the surface. OMI's unique capabilities for measuring important trace gases with a small footprint and daily global coverage will be a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change. OMI's high spatial resolution is unprecedented and will enable detection of air pollution on urban scale resolution. In this paper, the instrument and its performance will be discussed. © 2006 IEEE."
"7003554208;6701379896;7102620639;7005808242;57111001300;56744278700;35514163500;6701413579;7101632204;","Assessment of twentieth-century regional surface temperature trends using the GFDL CM2 coupled models",2006,"10.1175/JCLI3709.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644766606&doi=10.1175%2fJCLI3709.1&partnerID=40&md5=71fe9b32c487a01ba0cb50fc67c83594","Historical climate simulations of the period 1861-2000 using two new Geophysical Fluid Dynamics Laboratory (GFDL) global climate models (CM2.0 and CM2.1) are compared with observed surface temperatures. All-forcing runs include the effects of changes in well-mixed greenhouse gases, ozone, sulfates, black and organic carbon, volcanic aerosols, solar flux, and land cover. Indirect effects of tropospheric aerosols on clouds and precipitation processes are not included. Ensembles of size 3 (CM2.0) and 5 (CM2.1) with all forcings are analyzed, along with smaller ensembles of natural-only and anthropogenic-only forcing, and multicentury control runs with no external forcing. Observed warming tr ends on the global scale and in many regions are simulated more realistically in the all-forcing and anthropogenic-only forcing runs than in experiments using natural-only forcing or no external forcing. In the all-forcing and anthropogenic-only forcing runs, the model shows some tendency for too much twentieth-century warming in lower latitudes and too little warming in higher latitudes. Differences in Arctic Oscillation behavior between models and observations contribute substantially to an underprediction of the observed warming over northern Asia. In the all-forcing and natural-only forcing runs, a temporary global cooling in the models during the 1880s not evident in the observed temperature records is volcanically forced. El Niño interactions complicate comparisons of observed and simulated temperature records for the El Chichón and Mt. Pinatubo eruptions during the early 1980s and early 1990s. The simulations support previou s findings that twentieth-century global warming has resulted from a combination of natural and anthropogenic forcing, with anthropogenic forcing being the dominant cause of the pronounced late-twentieth-century warming. The regional results provide evidence for an emergent anthropogenic warming signal over many, if not most, regions of the globe. The warming signal has emerged rather monotonically in the Indian Ocean/western Pacific warm pool during the past half-century. The tropical and subtropical North Atlantic and the tropical eastern Pacific are examples of regions where the anthropogenic warming signal now appears to be emerging from a background of more substantial multidecadal variability. © 2006 American Meteorological Society."
"13005625100;6506128535;7102314673;","Microclimate, light adaptation and desiccation tolerance of epiphytic bryophytes in two Venezuelan cloud forests",2006,"10.1111/j.1365-2699.2006.01468.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646015682&doi=10.1111%2fj.1365-2699.2006.01468.x&partnerID=40&md5=c74659996c6817c479c3019aa85851e7","Aim: Analysis of microclimate factors and physiological responses determining survival and growth of epiphytic bryophytes in the lower canopy and trunk space of north-Andean cloud forests. Location: Two cloud forests at 2000-2400 m in the northern Andes near Mérida, Venezuela. Methods: Data-logging of dry and wet-season temperature, relative humidity (r.h.) and photosynthetically-active radiation (PAR) for month-long periods, and laboratory measurements of desiccation tolerance and light responses of selected epiphytic bryophytes. Results: Rainfall averages 20 mm or less in January and February, and 200 mm or more from August to October, but is very variable at all seasons. The proportion of time 'wet' (continuous 100% r.h.) in the months sampled ranged from 8.5% to 52.2% or more; a dry/wet-season range between 20% and 40% is probably commoner. The length of 'wet' and 'dry' periods approximated log-normal distributions, with mid-points for wet periods ranging from 2.8 to 10.7 h, and dry periods from 6.2 to 17.1 h. The longest recorded dry period was 143 h. Humidity typically rose during the night to &gt; 90% r.h., reaching 100% for significant periods (implying cloudwater (fog) deposition) on about one night in two in all seasons. Of six bryophytes of pendulous growth form, all survived periods of at least a few days' desiccation; most recovered better from high than low humidities. Measured 95% light-saturation values ranged from 110 to 256 μmol m -2 s -1, somewhat but not greatly higher than ambient light levels Main conclusions: Environmental conditions in the cloud forests are probably near-optimal for epiphytic bryophytes, but in even the wettest forest these plants must tolerate at least short periods of drying at any time of year, and longer periods seasonally. Interception of cloudwater droplets from moving air is likely to be an important source of water for bryophytes of pendant and other diffuse life forms, especially in periods of low rainfall. Absorption of water from near-saturated air is probably of little physiological significance. Bryophytes of these life-forms are notably conspicuous in tropical-montane cloud forests. They remain prominent into humid temperate regions such as southern Chile, New Zealand and Macaronesia, but progressively disappear at higher latitudes with the stresses of increasing seasonality. © 2006 Blackwell Publishing Ltd."
"35551376300;13404905600;7102925250;7005473082;7404291795;","Band residual difference algorithm for retrieval of so2 from the aura Ozone Monitoring Instrument (OMI)",2006,"10.1109/TGRS.2005.861932","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646395986&doi=10.1109%2fTGRS.2005.861932&partnerID=40&md5=ab2d2816767bdb013cbf61eae8553fa6","The Ozone Monitoring Instrument (OMI) on EOS/Aura offers unprecedented spatial and spectral resolution, coupled with global coverage, for space-based UV measurements of sulfur dioxide (SO2). This paper describes an OMI SO2 algorithm (the band residual difference) that uses calibrated residuals at SO2 absorption band centers produced by the NASA operational ozone algorithm (OMTO3). By using optimum wavelengths for retrieval of SO2, the retrieval sensitivity is improved over NASA predecessor Total Ozone Mapping Spectrometer (TOMS) by factors of 10 to 20, depending on location. The ground footprint of OMI is eight times smaller than TOMS. These factors produce two orders of magnitude improvement in the minimum detectable mass of SO2. Thus, the diffuse boundaries of volcanic clouds can be imaged better and the clouds can be tracked longer. More significantly, the improved sensitivity now permits daily global measurement of passive volcanic degassing of SO2 and of heavy anthropogenic SO2 pollution to provide new information on the relative importance of these sources for climate studies. © 2006 IEEE."
"7003741536;7003840159;14031427400;8408994300;7202377054;6603231831;6603541351;7102962393;8658853400;6602252422;6603085134;7401742385;6507257768;","13th AMS conference on satellite meteorology and oceanography",2006,"10.1175/BAMS-87-5-633","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744505688&doi=10.1175%2fBAMS-87-5-633&partnerID=40&md5=10bf8523c0782b3cc1d48f83b58192ec","The American Meteorological Society (AMS) 13th Conference on Satellite Meteorology and Oceanography was held at the Nortfolk Waterside Marriot in Norfolk, Virginian from 20-23 September 2004. The special theme for the event was ""Next Generation Environmental Sensors and Emerging Applications in Satellite Meteorology and Oceanography."" The more than 200 submitted abstracts strongly reflected the continued application of research and operational environmental satellites in a variety of disciplines and suggest exciting new opportunities for monitoring Earth with future sensors. The opening session focused on new and future sensors and applications. The second day of the conference was divided into two sessions: data assimilation and environmental applications. The sessions on the third day focused on operational products and climatology and long-term satellite studies. The final day of the conference was devoted to the session on retrivals and cloud products."
"6508380559;","Continuum or zonation? Altitudinal gradients in the forest vegetation of Mt. Kilimanjaro",2006,"10.1007/s11258-005-9049-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745047511&doi=10.1007%2fs11258-005-9049-4&partnerID=40&md5=08a6b9e53741f0717797c2e8da9f067d","Based on the analysis of 600 vegetation plots using the method of Braun-Blanquet (1964) the composition of the whole vascular forest plant flora with about 1220 species was studied in the forests of Mt. Kilimanjaro. The altitudinal distribution of all strata (trees, shrubs, epiphytes, lianas and herbs) along a transect of 2400 m is discussed with respect to altitudinal zonation and ecological factors. With uni-dimensionally constraint clustering significant discontinuities were revealed that occurred simultaneously in the different strata. Thus even in structurally highly complex, multilayered tropical montane forests distinct community units exist that can be surveyed and classified by the Braun-Blanquet approach. This observed zonation was significantly correlated with altitude, temperature and soil acidity (pH); rainfall was of importance in particular for the zonation of epiphytes. Other key factors were humidity (influenced by stable cloud condensation belts) and minimum temperature (in particular the occurrence of frost at 2700 m altitude upslope). The contrary results of other transect studies in East Africa in respect to continuity of change in floristic composition appear to be caused by different sampling methods and intensities or mixing of data from areas with different climate conditions, whereas species richness did not influence the clarity of floristic discontinuities on Kilimanjaro and other parts of East Africa. © Springer 2005."
"7102505167;7006839993;13406211800;","Synoptic climatological influences on the spatial and temporal variability of aerosols over North America",2006,"10.1002/joc.1277","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646455198&doi=10.1002%2fjoc.1277&partnerID=40&md5=7d03227d0067f7f403ea2ffe2c4c2ed3","The spatial and temporal variability of atmospheric aerosols is not well understood, as most studies have been constrained to data sets that include few stations and are of short duration. Furthermore, all methods for quantifying atmospheric turbidity suffer from a major constraint in that they require cloudless sky conditions. This restriction produces gaps in the turbidity record and sampling bias, which has led to questionable inferences about the variability of aerosols. In this research, we address these concerns via analyses at scales broader than all previous studies. We analyzed the spectral aerosol optical depth at 500 nm (τa5) and Angström's wavelength exponent (α), which represents the relative size distribution of aerosols. A total of 27 sites, with a mean period of record of 7.3 years, are included. Beyond seasonal and spatial summaries of aerosol variability, we have divided observations by synoptic condition, utilizing the Spatial Synoptic Classification (SSC). Our results show that atmospheric turbidity across North America is greatest over the east. Seasonality of both parameters was shown, most notably a greater τa5 during summertime. Utilizing the SSC, we have uncovered significant differences across weather types. Moist weather types, especially moist tropical, display considerably higher turbidity, while the colder, drier dry polar weather type is associated with low aerosol optical depth. Certain weather types show considerable seasonal variability; the dry tropical weather type is associated with relatively low values in winter, but high values in summer, when convection is significant. Cluster analyses of stations yielded three general regions, each with similar synoptic variability: a western cluster with low aerosol optical depth and minimal synoptic variability, an eastern cluster with higher turbidity and variability, and a cluster located on the periphery of the eastern cluster, associated with moderate levels of turbidity but very high variability, suggesting a varied influence of nearby industrial areas. Copyright © 2006 Royal Meteorological Society."
"14012502000;8700026700;35600749500;7201706659;6602101632;","Validation of the AATSR Meteo product Sea Surface Temperature",2006,"10.1175/JTECH1876.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745039009&doi=10.1175%2fJTECH1876.1&partnerID=40&md5=27e949a59403dec284f2da246bb76a44","The Advanced Along Track Scanning Radiometer (AATSR) Sea Surface Temperature (SST) Meteo product, a fast-delivery level-2 product at 10 arc min spatial resolution, has been available from the European Space Agency (ESA) since 19 August 2002. Validation has been performed on these data at the Met Office on a daily basis, with a 2-day lag from data receipt. Meteo, product skin SSTs have been compared with point measurements of buoy SST, a 1° climate SST analysis field compiled from in situ measurements and Advanced Very High Resolution Radiometer (AVHRR) SSTs, and a 5° latitude-longitude 5-day averaged in situ dataset. Comparisons of the AATSR Meteo product against Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) SSTs are also presented. These validation results have confirmed the AATSR Meteo product skin SST to be within ±0.3 K of in situ data. Comparisons of the AATSR skin SSTs against buoy SSTs, from 19 August 2002 to 20 August 2003, give a mean difference (AATSR - buoy) of 0.04 K (standard deviation = 0.28 K) during nighttime, and a mean difference of 0.02 K (standard deviation = 0.39 K) during the day. Analyses of the buoy matchups have shown that there is no cool skin effect observed in the nighttime observations, implying that the three-channel AATSR product skin SST may be 0.1-0.2 K too warm. Comparisons with TMI SSTs confirm that the lower-latitude SSTs are not significantly affected by residual cloud contamination."
"12801992200;7004920873;7006307463;7005304841;7004364155;","22 views of the global albedo - Comparison between 20 GCMs and two satellites",2006,"10.1111/j.1600-0870.2006.00181.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645569821&doi=10.1111%2fj.1600-0870.2006.00181.x&partnerID=40&md5=4a1bd26e4ae1757ad0558de7be044cdf","A comprehensive comparison of characteristics of the planetary albedo (α) in data from two satellite measurement campaigns (ERBE and CERES) and output from 20 GCMs, simulating the 20th-century climate, is performed. Discrepancies between different data sets and models exist; thus, it is clear that conclusions about absolute magnitude and accuracy of albedo should be drawn with caution. Yet, given the present calibrations, a bias is found between different estimates of α, with modelled global albedos being systematically higher than the observed. The difference between models and observations is larger for the more recent CERES measurements than the older ERBE measurements. Through the study of seasonal anomalies and space and time distribution of correaltions between models and observations, specific regions with large discrepancies can be identified. It is hereby found that models appear to over-estimate the albedo during boreal summer and under-estimate it during austral summer. Furthermore, the seasonal variations of albedo in subtropical areas dominated by low stratiform clouds, as well as in dry desert regions in the subtropics, seem to be poorly simulated by the models. Copyright © Blackwell Munksgaard, 2006."
"7202796519;7004129856;7101978698;6602176067;7003852382;35550043200;35549804700;7006721718;8914870300;7005706036;10140373600;26660644800;6701525565;7006747377;6701834461;6701581258;7404297096;13404700100;7004166092;8781752100;8781752600;10141883400;6508391028;8781753000;8781751800;56209549900;13405351300;7406543293;8050090700;13405672000;24536733500;57197441903;7404829395;7404833617;13405811300;7004878841;57217344288;57196250561;57198888996;7101878445;13405729700;7801386398;6602121417;13405632200;6506304687;13405191100;7402964124;6603830708;","The Earth Observing System Microwave Limb Sounder (EOS MLS) on the aura satellite",2006,"10.1109/TGRS.2006.873771","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644620380&doi=10.1109%2fTGRS.2006.873771&partnerID=40&md5=a2a6a1ae91260ed3986384a6e2265799","The Earth Observing System Microwave Limb Sounder measures several atmospheric chemical species (OH, HO 2, H 2O, O 3, HCl, ClO, HOCl, BrO, HNO 3, N 2O, CO, HCN, CH 3CN, volcanic SO 2), cloud ice, temperature, and geopotential height to improve our understanding of stratospheric ozone chemistry, the interaction of composition and climate, and pollution in the upper troposphere. All measurements are made simultaneously and continuously, during both day and night. The instrument uses heterodyne radiometers that observe thermal emission from the atmospheric limb in broad spectral regions centered near 118, 190, 240, and 640 GHz, and 2.5 THz. It was launched July 15, 2004 on the National Aeronautics and Space Administration's Aura satellite and started full-up science operations on August 13, 2004. An atmospheric limb scan and radiometric calibration for all bands are performed routinely every 25 s. Vertical profiles are retrieved every 165 km along the suborbital track, covering 82°S to 82°N latitudes on each orbit. Instrument performance to date has been excellent; data have been made publicly available; and initial science results have been obtained. © 2006 IEEE."
"55607020000;6603613067;","Dynamics of the sulphate aerosol size distribution on a global scale",2006,"10.1029/2005JD006620","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745258211&doi=10.1029%2f2005JD006620&partnerID=40&md5=75aab87e80f5ccabdd436aa57ae98f8f","Parameterizations for size-dependent aerosols have been implemented in the Canadian Centre for Climate Modelling and Analysis (CCCma) atmospheric general circulation model (AGCM). This new model version considers comprehensive physical and chemical processes that are associated with the sulphate aerosol size distribution, including nucleation, condensation, hygroscopic growth, aqueous-phase chemistry, and dry and wet deposition. Results from in situ surface and airborne observations and remote sensing were used to validate the model. The comparisons give evidence for realistic sulphate size distributions over the regions where sulphate is the dominant aerosol type. In agreement with earlier published studies, it is found in sensitivity tests that the global sulphate burden is predominantly affected by wet deposition. However, the mass size distribution is mainly affected by coagulation, condensation, and below-cloud scavenging on the global scale. There is only weak sensitivity of the simulated mass size distribution to changes in in-cloud oxidation and the efficiency of nucleation. It is shown that the low sensitivities are caused by a compensating effect of coagulation in the former and low sensitivity of the mass size distribution to changes in nucleation rate and condensation efficiency for the latter case. Copyright 2006 by the American Geophyical Union."
"7003976079;6701715507;7004033942;9845516300;6701689939;7004169476;26643217800;13609930400;7003979342;7004764167;7003543851;7003532926;7201485519;7404142321;","Global mean cloud feedbacks in idealized climate change experiments",2006,"10.1029/2005GL025370","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646844490&doi=10.1029%2f2005GL025370&partnerID=40&md5=4657faca8eca270a84796d2b96c591bf","Global mean cloud feedbacks in ten atmosphere-only climate models are estimated in perturbed sea surface temperature (SST) experiments and the results compared to doubled CO2 experiments using mixed-layer ocean versions of these same models. The cloud feedbacks in any given model are generally not consistent: the sign of the net cloud radiative feedback may vary according to the experimental design. However, both sets of experiments indicate that the variation of the total climate feedback across the models depends primarily on the variation of the net cloud feedback. Changes in different cloud types show much greater consistency between the two experiments for any individual model and amongst the set of models analyzed here. This suggests that the SST perturbation experiments may provide useful information on the processes associated with cloud changes which is not evident when analysis is restricted to feedbacks defined in terms of the change in cloud radiative forcing."
"6701889097;6506545666;7403303191;7407104838;7801465482;6506416205;","Climate sensitivity to ocean dimethylsulphide emissions",2006,"10.1029/2005GL024982","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646846326&doi=10.1029%2f2005GL024982&partnerID=40&md5=5478a7b4e38f9b92fd27528e13a0f1d2","The production of dimethylsulphide (DMS) by ocean phytoplankton is hypothesized to form part of a feedback process on global climate. Changes in the DMS flux to the atmosphere cause changes to aerosols for cloud formation, leading to changes in the amount of radiation reaching the ocean, and hence on the planktonic production of DMS. This hypothesis has been investigated using a coupled ocean-atmosphere general circulation model (COAGCM) that includes an ocean ecosystem model and an atmospheric sulphur cycle. Ocean DMS concentrations are parameterised as a function of chlorophyll, nutrient, and light. The results of several sensitivity experiments are presented showing significant global climate change responses to perturbations in ocean DMS production. A small negative feedback from climate change onto ocean DMS production is found and the implications are discussed."
"55602027700;57209147154;","Cloud types associated with the Asian summer monsoons as determined from MODIS/TERRA measurements and a comparison with surface observations",2006,"10.1029/2006GL026004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646827690&doi=10.1029%2f2006GL026004&partnerID=40&md5=467a42d3c8152316b0155b71dcf76aa0","Using a 6-year June-July-August MODIS/Terra-measured cloud properties data set, the characteristics of clouds associated with the Asian summer monsoons are examined. The results indicate that a large amount of high clouds exists in the Indian monsoon region and account for approximately 65% of all cloud grids. Moreover, the interannual variation of high clouds is not apparent. In the East Asian monsoon region, high clouds show a relatively strong interannual variation and account for roughly 38.5% of all cloud grids. The overall percentages of middle and low clouds are comparable to each other within the East Asian monsoon region. Moreover three high cloud types have been identified to coexist in the Indian monsoon regions, i.e., cirrus, cirrostratus and deep convective clouds. Among them, cirrostratus has the largest percentage. In the East Asian monsoon region, the most frequently occurring cloud type is stratocumulus. However, compared with cloud climatology of surface observations, middle and low clouds are severely underestimated in the Asian monsoon regions by the MODIS/Terra measurements; in particular, the underestimation for low clouds is up to 80% in the Indian monsoon region. Therefore, great caution is needed when using the MODIS data to analyze middle and low clouds, especially when high and thick clouds exist. Copyright 2006 by the American Geophysical Union."
"7003854810;57203774512;6507100517;6603758021;57202128735;6603685334;7004801727;7102435748;7004206409;13610655700;55717441600;","First light from the Far-Infrared Spectroscopy of the Troposphere (FIRST) instrument",2006,"10.1029/2005GL025114","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646834954&doi=10.1029%2f2005GL025114&partnerID=40&md5=fcd51404da72f231f799da365a35db13","We present first light spectra that were measured by the newly-developed Far-Infrared Spectroscopy of the Troposphere (FIRST) instrument during a high-altitude balloon flight from Ft. Sumner, NM on 7 June 2005. FIRST is a Fourier Transform Spectrometer designed to measure accurately the far-infrared (15 to 100 μm; 650 to 100 wavenumbers, cm-1) emission spectrum of the Earth and its atmosphere. The flight data successfully demonstrated the FIRST instrument's ability to observe the entire energetically significant infrared emission spectrum (50 to 2000 cm-1) at high spectral and spatial resolution on a single focal plane in an instrument with one broad spectral bandpass beamsplitter. Comparisons with radiative transfer calculations demonstrate that FIRST accurately observes the very fine spectral structure in the far-infrared. Comparisons also show excellent agreement between the atmospheric window radiance measured by FIRST and by instruments on the NASA Aqua satellite that overflew the FIRST flight. FIRST opens a new window on the spectrum that can be used for studying atmospheric radiation and climate, cirrus clouds, and water vapor in the upper troposphere. Copyright 2006 by the American Geophysical Union."
"36955999600;6701370412;7003561442;13406672500;7005858285;","Optical properties of soot-water drop agglomerates: An experimental study",2006,"10.1029/2005JD006389","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646760644&doi=10.1029%2f2005JD006389&partnerID=40&md5=452b1b860a92b0d1e7a6b921b7ac1a66","Black carbon (BC) and organic carbon (OC) are the largest contributors to the aerosol absorption in the atmosphere, yet the absorption cross sections of BC and OC per unit mass are subject to a large uncertainty due to morphology, physicochemical properties, and the mixing state of carbonaceous particles. Theoretical studies suggest the possibility of an enhanced absorption by soot-cloud drop agglomerates; however, the magnitude of the effect has never been measured directly and remains highly uncertain. This study is a laboratory experiment aimed at the modeling of direct radiation forcing due to soot-water interaction in the presence of glutaric acid, a water-soluble OC. Specifically, we generate, in the laboratory, hydrophobic soot (acetylene soot) and hydrophilic soot (mixture of acetylene soot and glutaric acid) and investigate the structural and optical properties of hydrophobic and hydrophilic soot particles in dry and water-saturated air. Hydrophobic soot (HBS) particles do not exhibit any structural or morphological differences under dry and saturated conditions, whereas hydrophilic soot (HLS) particles, i.e., BC with a monolayer of glutaric acid, collapse into globules when relative humidity (RH) is increased to saturation. The optical properties of HBS show very little dependence on RH while HLS scattering and absorption coefficient increase markedly with RH. For the cases considered here, the maximum enhancement in absorption for a soot-water drop mixture was as much as a factor of 3.5, very similar to theoretical predictions. The data provided in this study should advance the treatment of polluted cloud layers in climate models. Copyright 2006 by the American Geophysical Union."
"6701606453;7006614696;7004114883;","Variability in the characteristics of precipitation systems in the tropical Pacific. Part II: Implications for atmospheric heating",2006,"10.1175/JCLI3698.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646809014&doi=10.1175%2fJCLI3698.1&partnerID=40&md5=46fdebb8e4108e3ff8524db0519b0b78","This paper explores changes in the principal components of observed energy budgets across the tropical Pacific in response to the strong 1998 El Niño event. Multisensor observations from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), Visible and Infrared Scanner (VIRS), and precipitation radar (PR) instruments aboard TRMM are used to quantify changes in radiative and latent heating in the east and west Pacific in response to the different phases of the El Niño-Southern Oscillation. In periods of normal east-west SST gradients there is substantial heating in the west Pacific and cooling in the east, implying strong eastward atmospheric energy transport. During the active phase of the El Niño, both the east and west Pacific tend toward local radiative-convective equilibrium resulting in their temporary energetic decoupling. It is further demonstrated that the response of these regions to ENSO-induced SST variability is directly related to changes in the characteristics of clouds and precipitation in each region. Through quantitative analysis of the radiative and latent heating properties of shallow, midlevel, and deep precipitation events and an equivalent set of nonprecipitating cloud systems, times of reduced atmospheric heating are found to be associated with a shift toward shallow and midlevel precipitation systems and associated low-level cloudiness. The precipitation from such systems is typically less intense, and they do not trap outgoing longwave radiation as efficiently as their deeper counterparts, resulting in reduced radiative and latent heating of the atmosphere. The results also suggest that the net effect of precipitating systems on top-of-the-atmosphere (TOA) fluxes and the efficiency with which they heat the atmosphere and cool the surface exhibit strong dependence on their surroundings. The sensitivity of cloud radiative impacts to the atmospheric and surface properties they act to modify implies the existence of strong feedbacks whose representation may pose a significant challenge to the climate modeling community. © 2006 American Meteorological Society."
"57203053317;","Aerosol effects on clouds and climate",2006,"10.1007/s11214-006-9051-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847297672&doi=10.1007%2fs11214-006-9051-8&partnerID=40&md5=9657ec246f29cc74a19fa88565433072","Aerosols affect the climate system by changing cloud characteristics in many ways. They act as cloud condensation and ice nuclei, they may inhibit freezing and they could have an influence on the hydrological cycle. While the cloud albedo enhancement (Twomey effect) of warm clouds received most attention so far and traditionally is the only indirect aerosol forcing considered in transient climate simulations, here I discuss the multitude of effects. © Springer Science+Business Media, Inc. 2007."
"6603412788;36848436500;57211224269;35997064100;7402345338;15761630100;7403544649;36655323000;7102193013;","Present-day climate and climate sensitivity in the Meteorological Research Institute coupled GCM version 2.3 (MRI-CGCM2.3)",2006,"10.2151/jmsj.84.333","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745189806&doi=10.2151%2fjmsj.84.333&partnerID=40&md5=0b981b77bbfc359eedf10df6a5827f3e","A new version of the Meteorological Research Institute (MRI) coupled general circulation model MRI-CGCM2 (MRI2.3) is developed and compared with the previous version (MRI2.0). The cloud scheme includes diagnostic function for cloud amount separately specified for convective and layer clouds, which is one of the major modifications contributing to the improved model performance. MRI2.3 exhibits better agreement with the observations in many aspects of present-day climate simulations, including the global energy budget, meridional distributions of shortwave and longwave radiation at the top of the atmosphere, and geographical distributions of surface air temperature and precipitation. The effective climate sensitivity of each version is evaluated based on an experiment with a transient (1%/year) increase of carbon dioxide concentration. The effective climate sensitivity of MRI2.3 (2.9 K) is about twice that of MRI2.0 (1.4 K). The change in the cloud-forcing response, particularly for shortwave cloud forcing, is essential for increasing climate sensitivity. A difference in tropical low-level clouds over the subsidence regions contributes significantly to the difference in cloud-forcing changes in response to a climate change. Analyses based on circulation regimes, defined by the vertical velocity at the mid-troposphere, suggest that the cloud-forcing response in the tropics is controlled more by thermodynamic characteristics, such as changes of the stability in the lower troposphere, rather than by large-scale circulation changes, such as a change in the subsidence strength. © 2006, Meteorological Society of Japan."
"13204619900;7401559815;","Atmospheric hydrological cycle in the tropics in twentieth century coupled climate simulations",2006,"10.1002/joc.1279","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646245205&doi=10.1002%2fjoc.1279&partnerID=40&md5=cb935b96bd2f2896dfc609fd9d22b9e8","The objective of this study is to identify and understand the long-term change of the tropical hydrological cycle in twentieth-century climate simulations provided by 16 Coupled General Circulation Models (CGCMs) participating in the Intergovernmental Panel on Climate Change (IPCC), Fourth Assessment Report (AR4). This work is focused on trends of precipitation and clouds over the tropical ocean and land. We find that the CGCMs are reasonably consistent in depicting aspects of long-term changes in twentieth century climate and the tropical hydrological cycle, including (1) a relatively good simulation of trends in surface warming over both the tropical ocean and land, in agreement with observations; (2) increasing precipitation over the tropical ocean and decreasing precipitation over tropical land; (3) an increasing trend in heavy and light rain, but a decreasing trend in moderate rain, over the tropical ocean; and (4) a reduction in total cloud cover in the tropics. These successful simulations are encouraging and enhance our confidence in the future climate projections provided by these models. On the other hand, the current generation of CGCMs still has a number of deficiencies, particularly in modeling clouds and their interactions with radiation. Although most CGCMs are able to simulate the correct sign of trends in precipitation and clouds, they significantly underestimate the magnitudes of the observations. These underestimations likely cause gross errors in model simulations of the global water and energy balance. A better understanding of physical processes and an improvement in the CGCM representations of physical processes associated with clouds and their interaction with radiation are needed. Copyright © 2005 Royal Meteorological Society."
"35464731600;","Satellite observations of natural and anthropogenic aerosol effects on clouds and climate",2006,"10.1007/s11214-006-9052-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847291962&doi=10.1007%2fs11214-006-9052-7&partnerID=40&md5=5762b94df4f3069ddb476b5824a4ee32","Anthropogenic aerosols affect the climate system and the hydrological cycle. The net effect of aerosols is to cool the climate system, directly by reflecting sunlight to space, and indirectly by increasing the brightness and cover of clouds that in turn also reflect more sunlight to space. The uncertainty in the aerosol effect on climate is 5 times greater than that of the greenhouse gases. The reason for this is the short aerosol lifetime and chemical complexity, that makes it difficult to represent the global aerosol budget from surface or aircraft measurements. Satellites provide daily global information about the aerosol content, generating large statistics with excellent regional and global representation of the aerosol column concentration, and differentiating fine from coarse aerosol. Here we use observations performed with the MODIS instrument onboard the Terra and Aqua satellites to differentiate natural from anthropogenic aerosols, and to measure the aerosol effect on cloud properties and on the reflectivity of sunlight. © Springer Science+Business Media, Inc. 2007."
"6603463143;7003459035;7004357098;","The effects of climate change on the long-term conservation of Fagus grandifolia var. mexicana, an important species of the Cloud Forest in Eastern Mexico",2006,"10.1007/s10531-004-1868-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745457990&doi=10.1007%2fs10531-004-1868-4&partnerID=40&md5=e5db39af876fae8f0d77ae48b3583bbe","We examined the effects of climate change on the future conservation and distribution patterns of the cloud forests in eastern Mexico, by using as a species model to Fagus grandifolia Ehr. var. mexicana (Martínez) Little which is mainly located in this vegetation type, at the Sierra Madre Oriental. This species was selected because it is restricted to the cloud forest, where it is a dominant element and has not been considered for protection in any national or international law. It is probably threatened due to the fact that it plays an important social role as a source of food and furnishing. We used a floristic database and a bioclimatic modeling approach including 19 climatic parameters, in order to obtain the current potential distribution pattern of the species. Currently, its potential distribution pattern shows that it is distributed in six different Mexican Priority Regions for Conservation. In addition, we also selected a future climate scenario, on the basis of some climate changes predictions already proposed. The scenario proposed is characterized by +2 °C and -20% rainfall in the region. Under this predicted climatic condition, we found a drastic distribution contraction of the species, in which most of the remaining populations will inhabit restricted areas located outside the boundaries of the surrounding reserves. Consequently, our results highlight the importance of considering the effects of possible future climate changes on the selection of conservation areas and the urgency to conserve some remaining patches of existing cloud forests. Accordingly, we believe that our bioclimatic modeling approach represents a useful tool to undertake decisions concerning the definition of protected areas, once the current potential distribution pattern of some selected species is known. © Springer 2006."
"7102084129;","Aerosol-cloud interactions control of earth radiation and latent heat release budgets",2006,"10.1007/s11214-006-9053-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847321222&doi=10.1007%2fs11214-006-9053-6&partnerID=40&md5=7ef8ce57fc4ef5aa136b0c8d4e202704","Aircraft observations and model simulations show that cloud development is strongly modulated by the impact of cloud-aerosol interactions on precipitation forming processes. New insights into the mechanisms by which aerosols dominate the cloud cover of marine shallow clouds suggest that feedbacks between the cloud microstructure and cloud dynamics through precipitation processes play a major role in determining when a solid cloud cover will break up into a field of trade wind cumulus. Cloud-aerosol interactions dominate not only the dynamics of marine shallow clouds, but also the lifetime and the vertical disposition of latent heat of deep convective clouds over ocean and even more strongly over land. Recent coincident satellite measurements of aerosols and cloud properties quantify the aerosol effects on cloud cover and radiative forcing on regional and global scales. The shapes of the satellite retrieved relations between aerosols and cloud properties are consistent with the suggested ways by which aerosols affect clouds via precipitation processes, particularly by affecting the intensity of the cloud vertical air motions and its vertical development. © Springer Science+Business Media, Inc. 2007."
"8923624600;57211223914;","Changes in low cloudiness over China between 1971 and 1996",2006,"10.1175/JCLI3679.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646357754&doi=10.1175%2fJCLI3679.1&partnerID=40&md5=446a7f87579002ebb647371e3a091668","The climatology and long-term trends of low-cloud conditions over China were examined using the Extended Edited Cloud Report Archive data from 1971 to 1996. Linear regression analysis was applied to time series of clear-sky frequencies and low-cloud frequencies, and low-cloud amounts when present. Over the 26-yr study period, the clear-sky frequency increased over northern China. During summer, the frequency of cumuliform clouds decreased over almost all of China. A significant decrease characterized the trend in cumulonimbus (Cb) frequency; however, the Cb cloud amount when present increased over the Yangtze River basin and southern China. Increasing trends in stratocumulus (Sc) cloud amount when present were also observed over much of China. © 2006 American Meteorological Society."
"7103248807;6507355747;35986800300;7404029779;56232430600;7006766881;7004764167;7404142321;7407104838;6602131529;56363371300;7004169476;6602665711;7103373205;35570389600;7103180783;7201921725;55451545500;57203049177;7006261583;6506592395;25030776200;13402835300;14623255000;13403080600;","The new Hadley Centre Climate Model (HadGEM1): Evaluation of coupled simulations",2006,"10.1175/JCLI3712.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646381345&doi=10.1175%2fJCLI3712.1&partnerID=40&md5=d8a7be02058c63ac6f2dd95da9dd3d67","A new coupled general circulation climate model developed at the Met Office's Hadley Centre is presented, and aspects of its performance in climate simulations run for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) documented with reference to previous models. The Hadley Centre Global Environmental Model version 1 (HadGEM1) is built around a new atmospheric dynamical core; uses higher resolution than the previous Hadley Centre model, HadCM3; and contains several improvements in its formulation including interactive atmospheric aerosols (sulphate, black carbon, biomass burning, and sea salt) plus their direct and indirect effects. The ocean component also has higher resolution and incorporates a sea ice component more advanced than HadCM3 in terms of both dynamics and thermodynamics. HadGEM1 thus permits experiments including some interactive processes not feasible with HadCM3. The simulation of present-day mean climate in HadGEM1 is significantly better overall in comparison to HadCM3, although some deficiencies exist in the simulation of tropical climate and El Niño variability. We quantify the overall improvement using a quasi-objective climate index encompassing a range of atmospheric, oceanic, and sea ice variables. It arises partly from higher resolution but also from greater fidelity in modeling dynamical and physical processes, for example, in the representation of clouds and sea ice. HadGEM1 has a similar effective climate sensitivity (2.8 K) to a CO2 doubling as HadCM3 (3.1 K), although there are significant regional differences in their response patterns, especially in the Tropics. HadGEM1 is anticipated to be used as the basis both for higher-resolution and higher-complexity Earth System studies in the near future."
"7202488998;","Atmospheric aerosol and cloud condensation nuclei formation: A possible influence of cosmic rays?",2006,"10.1007/s11214-006-9055-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847313758&doi=10.1007%2fs11214-006-9055-4&partnerID=40&md5=4cace4f293d7fede9044d4ea67513b50","A physical mechanism which may have a potential to connect climate with cosmic rays (CR) involves aerosol particle formation by CR generated atmospheric ions followed by new particle growth. Only grown particles can scatter sunlight efficiently and can eventually act as cloud condensation nuclei (CCN) and thereby may influence climate. Moreover grown particles live longer as they are less rapidly scavenged by pre-existing larger particles. The present paper discusses aerosol particle formation and growth in the light of new measurements recently made by our MPIK Heidelberg group. Emphasis is placed upon the upper troposphere where very low temperatures tend to facilitate new particle formation by nucleation. The new measurements include: laboratory measurements of cluster ions, aircraft measurements of ambient atmospheric ions, and atmospheric measurements of the powerful nucleating gas H2SO 4 and its precursor SO2. The discussion also addresses model simulations of aerosol formation and growth. It is concluded that in the upper troposphere new aerosol formation by CR generated ions is a frequent process with relatively large rates. However new particle formation by homogeneous nucleation (HONU) which is not related to CR also seems to be efficient. The bottleneck in the formation of upper troposphere aerosol particles with sizes sufficiently large to be climate relevant is not nucleation but growth of small particles. Our recent upper troposphere SO2 measurements suggest that particle growth by gaseous sulphuric acid condensation is at least occasionally efficient. If so CR mediated formation of CCN sized particles should at least occasionally be operative in the upper troposphere. © Springer Science+Business Media, Inc. 2007."
"7404678955;7003976079;7005500582;7407104838;35740180800;13404245200;","The physical properties of the atmosphere in the new Hadley Centre Global Environmental Model (HadGEM1). Part 1: Model description and global climatology",2006,"10.1175/JCLI3636.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646348458&doi=10.1175%2fJCLI3636.1&partnerID=40&md5=a2adc60ddbccbf9f00706b8560a928f9","The atmospheric component of the new Hadley Centre Global Environmental Model (HadGEM1) is described and an assessment of its mean climatology presented. HadGEM1 includes substantially improved representations of physical processes, increased functionality, and higher resolution than its predecessor, the Third Hadley Centre Coupled Ocean-Atmosphere General Circulation Model (HadCM3). Major developments are the use of semi-Lagrangian instead of Eulerian advection for both dynamical and tracer fields; new boundary layer, gravity wave drag, microphysics, and sea ice schemes; and major changes to the convection, land surface (including tiled surface characteristics), and cloud schemes. There is better coupling between the atmosphere, land, ocean, and sea ice subcomponents and the model includes an interactive aerosol scheme, representing both the first and second indirect effects. Particular focus has been placed on improving the processes (such as clouds and aerosol) that are most uncertain in projections of climate change. These developments lead to a significantly more realistic simulation of the processes represented, the most notable improvements being in the hydrological cycle, cloud radiative properties, the boundary layer, the tropopause structure, and the representation of tracers."
"7101939964;14046153700;36015299300;","On the origin of the tropical Atlantic decadal oscillation based on the analysis of the ICOADS",2006,"10.1256/qj.05.01","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746239477&doi=10.1256%2fqj.05.01&partnerID=40&md5=8f465f19b3de27d3f96a714e4578a24f","From an analysis of the International Comprehensive Ocean-Atmosphere Data Set, we were able to confirm salient features of the tropical Atlantic decadal oscillation illustrated in previous works. These features include antisymmetric behaviour of surface air pressure and sea surface temperature with two centres of action residing in the tropical North and South Atlantic Oceans. In addition to the recognized features of the oscillation, we found a new aspect: the principal mechanism regulating the oscillation differs between the north and south centres of action. Decadal components of the relative humidity time series show a maximum value of lag cross-correlation at a lag of - 2 years. Such a temporal evolution was irrespective of the centres of action and the reference time series. The two reference series employed are the sunspot numbers and the southerlies over the western equatorial Atlantic. Associated with this, statistically significant phase shifts between the decadal components of variables exist, especially in the tropical North Atlantic Ocean. For the decadal oscillation, relative humidity change was dominated by specific humidity change over the tropical North Atlantic and by air temperature change over the tropical South Atlantic. For the frequency band of the solar cycle, the variation of relative humidity seemed to amplify the Earth's response to the sun's radiation changes that had previously been considered too small to affect the Earth's climate. By incorporating our new findings with the known features of the oscillation, we can suggest that the variability of solar radiation may be crucial as an originator, or at least as a regulator, of the oscillation in combination with the climate distribution of clouds and water vapour over the tropical Atlantic. © Royal Meteorological Society, 2006."
"6506537159;7410255460;7006432091;","Momentum transport processes in the stratiform regions of mesoscale convective systems over the western Pacific warm pool",2006,"10.1256/qj.04.141","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745010419&doi=10.1256%2fqj.04.141&partnerID=40&md5=60db5838296dc63ea5d9d822cb9f6da2","Momentum transport by the stratiform components of mesoscale convective systems (MCSs) during the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment in December 1992 is investigated using a cloud-resolving model. The mesoscale momentum transport by the stratiform regions of MCSs is examined in two distinct large-scale flow regimes associated with the intraseasonal oscillation over the western Pacific warm pool. Model simulations for 14 December 1992 characterize the 'westerly onset' period, which has relatively weak low-level westerlies with easterlies above. Simulations for 23-24 December represent the 'strong westerly' regime, when westerlies extend from the upper troposphere to the surface, with a jet 2-3 km above the surface. In the westerly onset simulation, the extensive stratiform region of a MCS contained a broad region of descent that transported easterly momentum associated with the mid-level easterly jet downward. Thus, the stratiform regions acted as a negative feedback to decrease the large-scale mean westerly momentum developing at low levels. In the strong westerly regime, the mesoscale downward air motion in the stratiform regions of large MCSs transported westerly momentum downward and thus acted as a positive feedback, strengthening the already strong westerly momentum at low levels. Momentum fluxes by the mesoscale stratiform region downdraughts are shown to have a systematic and measurable impact on the large-scale momentum budget. © Royal Meteorological Society, 2006."
"7101631674;","What do cosmogenic isotopes tell us about past solar forcing of climate?",2006,"10.1007/s11214-006-9049-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847266923&doi=10.1007%2fs11214-006-9049-2&partnerID=40&md5=96ba6f321cd4751f21b8264028c7bb76","In paleoclimate studies, cosmogenic isotopes are frequently used as proxy indicators of past variations in solar irradiance on centennial and millennial timescales. These isotopes are spallation products of galactic cosmic rays (GCRs) impacting Earth's atmosphere, which are deposited and stored in terrestrial reservoirs such as ice sheets, ocean sediments and tree trunks. On timescales shorter than the variations in the geomagnetic field, they are modulated by the heliosphere and thus they are, strictly speaking, an index of heliospheric variability rather than one of solar variability. Strong evidence of climate variations associated with the production (as opposed to the deposition) of these isotopes is emerging. This raises a vital question: do cosmic rays have a direct influence on climate or are they a good proxy indicator for another factor that does (such as the total or spectral solar irradiance)? The former possibility raises further questions about the possible growth of air ions generated by cosmic rays into cloud condensation nuclei and/or the modulation of the global thunderstorm electric circuit. The latter possibility requires new understanding about the required relationship between the heliospheric magnetic fields that scatter cosmic rays and the photospheric magnetic fields which modulate solar irradiance. © Springer Science+Business Media, Inc. 2007."
"57202413846;","Observed long-term variations of solar irradiance at the earth's surface",2006,"10.1007/s11214-006-9050-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847255533&doi=10.1007%2fs11214-006-9050-9&partnerID=40&md5=7e0392ce195a0ddc3b7860ddaf21c327","The variation of global radiation (sum of direct solar and diffuse sky radiation) at the Earth's surface is examined based on pyranometer measurements at about 400~sites. The period of the study covers in general the last 50 years. For Europe the study is extended to the beginning of observations in the 1920s and 1930s. Global radiation generally increased in Europe from the 1920s to the 1950s. After the late 1950s and early 1960s global radiation began to decrease in most areas of the world at a mean rate of 0.7 Wm-2a-1 until 1980s, thereafter 75%; of the stations showed a recovery at a mean rate of 0.7 Wm-2a-1. All stations in the Polar region, which are far from aerosol sources, also show this pattern of change. At the remaining 25% of the stations the decrease has continued to present. These regions are a part of China, most of India, and Central Africa. Both during the declining and recovering phases global radiation observed under the cloudless condition also followed the same tendency, indicating the simultaneous and parallel changes of aerosol and cloud conditions. Long-term observations of total zenith transmittance of the atmosphere indicate a decrease in transmittance to the mid 1980s and an increase after this period. Since the brighter and darker periods correspond to relatively warmer and colder periods, the present study offers the possibility to quantitatively evaluate the mutual relationships between the solar irradiance, atmospheric transmittance, cloud conditions and air temperature. © Springer Science+Business Media, Inc. 2007."
"7005485117;14047829400;","Transitions in the surface energy balance dufring the life cycle of a monsoon season",2006,"10.1007/BF02702033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746323920&doi=10.1007%2fBF02702033&partnerID=40&md5=2a5ba0ed5dbea03f87e6fae4954bbf6b","In this observational/diagnostic study, we illustrate the time history of some important parameters of the surface energy balance during the life cycle of a single monsoon season. This chronology of the surface energy balance portrays the differential equilibrium state from the preonset phase to the withdrawal phase. This includes an analysis of the time history of base variables such as soil moisture, ground temperature, cloud cover, precipitation and humidity. This is followed by an analysis of the components of the surface energy balance where we note subtle changes in the overall balances as we proceed from one epoch of the monsoon to the next. Of interest here is the transition sequence: preonset, onset, break, revival, break, revival and withdrawal during the year 2001. Computations are all illustrated for a box over central India where the coastal effects were small, data coverage was not sparse and where the semi-arid land mass changes drastically to a lush green area. This region exhibited large changes in the components of surface energy balance. The principal results pertain to what balances the difference among the incoming short wave radiation (at the earth's surface) and the long wave radiation exhibited by the ground. That difference is balanced by a dominant sensible heat flux and the reflected short wave radiation in the preonset stage. A sudden change in the Bowen ratio going from > 1 to < 1 is noted soon after the onset of monsoon. Thereafter the latent heat flux from the land surface takes an important role and the sensible heat flux acquires a diminishing role. We also examine the subtle changes that occur in the components of surface energy balance between the break and the active phases. The break phases are seen to be quite different from the preonset phases. This study is aimed to illustrate the major importance of moisture and clouds in the radiative transfer computations that are central to the surface energy balance during each epoch. These sensitivities (of moisture and clouds) have major consequences for weather and climate forecasts. © Printed in India."
"7005292238;","Measurement of total and spectral solar irradiance",2006,"10.1007/s11214-006-9045-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847288399&doi=10.1007%2fs11214-006-9045-6&partnerID=40&md5=57d499a15ee8b6e16abe265bc9a48982","The Sun's electromagnetic radiation powers our solar system. In the case of the Earth it heats the lands and ocean, maintains our atmosphere, generates clouds, and cycles water. For other planets and minor bodies, similar and appropriate physical processes occur, also powered by the Sun. The Sun varies on all time scales and a precise knowledge of the Sun's irradiance and its variation is essential to our understanding of environments and physical conditions throughout our solar system. Measurements of solar irradiance and its variation can only be made from space, and almost thirty years of observation have now established that the total solar irradiance (TSI) varies by only 0.1 to 0.3%, while certain portions of the solar spectrum, the ultraviolet for example, vary by orders of magnitude more. This paper provides an overview of TSI observations and of spectral irradiance observations from the ultraviolet to the near infrared. © Springer Science+Business Media, Inc. 2007."
"55243231000;36728564200;","Seasonal heating processes over the Indochina Peninsula and the Bay of Bengal prior to the monsoon onset in 1998",2006,"10.2151/jmsj.84.375","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745212878&doi=10.2151%2fjmsj.84.375&partnerID=40&md5=3db1b3fb2ab3dbdca226ab42786fdf91","Using GAME reanalysis upper-air data, we attempt to reveal the seasonal evolution of the heat source (Q1), and moisture sink (Q2) over and around the Indochina Peninsula (IP), from April to June 1998. Pre-monsoon rainfall occurs inland of IP prior to the large-scale monsoon onset in middle May. In this period, positive Q1, in excess of 3 K day-1 appears around the middle-lower Mekong River basin (MLMRB) centered around 500-600 hPa, which is accompanied by positive Q2, slightly below the peak level of Q1. This suggests that the pre-monsoon rainfall is associated with a cumulus-type convection. The horizontal distribution of vertically integrated Q1 (&lt;Q1&gt;) and Q2 (&lt;Q2&gt;) over MLMRB is similar, suggesting that the contribution of latent heating is nearly equivalent to sensible heat supply from the land surface. In contrast, negative &lt;Q1&gt;, less than -100 W m-2, is discernible over the Bay of Bengal (BoB), which is collocated with a strong downward motion. Once the large-scale monsoon commences, the value of &lt;Q1&gt; in MLMRB becomes roughly the same magnitude as those in the pre-monsoon season. The vertical profile of Q1 and Q2 are indicative of the existence of stratiform and cumulus-type clouds. On the other hand, the whole troposphere over BoB is abruptly occupied by deep heating, associated with convective activities as implied by positive &lt;Q1 &gt; and &lt;Q2&gt;. The se atmospheric heat and moisture budget analysis indicate the presence of a large regional difference between MLMRB and BoB, especially in the pre-monsoon season. The qualitative heating difference, which may be attributable to the structure of the cumulus-type convection, is recognizable even after the monsoon onset. © 2006, Meteorological Society of Japan."
"14018647300;25223207200;7801578855;","Characteristics of the Yamase winds over oceans around Japan observed by the scatterometer-derived ocean surface vector winds",2006,"10.2151/jmsj.84.365","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745223482&doi=10.2151%2fjmsj.84.365&partnerID=40&md5=7aabce7e37c8903a9fb6b4ce614343c8","Yamase is the name for local northeasterly winds that blow from the Pacific Ocean to the east coasts of Hokkaido, and the Tohoku District from May to August. They are cool and moist winds accompanied by low-level clouds. In the present study, we investigate the Yamase winds over the oceans around Japan, using ocean surface vector winds observed by a satellite-scatterometer. In order to define the Yamase Phenomena, we employed an Empirical Orthogonal Function (EOF) analysis of the AMeDAS surface air temperatures over the Tohoku District from May to August. Daily mean temperature anomaly (ΔT), which is a deviation from the climatological daily mean temperature, is calculated for the 167 AMeDAS stations. The spatial coefficient function of the EOF first mode (EOF1), shows synchronous temperature changes in the whole Tohoku District, while that of the EOF second mode (EOF2), shows a seesaw pattern of temperature variation, between the Pacific and Japan Sea sides. The EOF-decomposed temperature variation, and ΔT at the Hachinohe station (a Yamase index), has high correlations; for EOF1, the correlation is 0.78, and for EOF1+2, it becomes 0.89. The Yamase Phenomena represented by the Hachinohe negative ΔT, is thus associated with two different patterns of the temperature variations in the Tohoku District. The composite wind map made through the sampling of days, with the Hachinohe ΔT < -2°C, shows northeasterly ocean winds blowing toward the Sanriku coast, an anti-cyclonic circulation center in the eastern Okhotsk Sea, and northeasterly surface winds along the Kuril Islands. When the winds approach the Tohoku District in the Pacific Ocean, they separate two flows around 40°N off Miyako. The surface wind fields associated with the cold phenomena of EOF1 and EOF2 corresponding to the Hachinohe negative ΔT are different. The former indicates the northeasterly wind blowing toward the Sanriku coast, and the latter that the northeasterly winds from the sea south of the Kuril Islands, change their direction around 145°E and the easterly winds blow toward the Sanriku coast. The Kitakami Mountains influence significantly on the Yamase winds, over the coastal Pacific Ocean. © 2006, Meteorological Society of Japan."
"6602878057;6701346974;7004479957;","Climate sensitivity and cloud response of a GCM with a superparameterization",2006,"10.1029/2005GL025464","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646457563&doi=10.1029%2f2005GL025464&partnerID=40&md5=23d6f9789990350940beb64cc3c8e7ac","The climate sensitivity of an atmospheric GCM that uses a cloud-resolving model as a convective superparameterization is analyzed by comparing simulations with specified climatological sea surface temperature (SST) and with the SST increased by 2 K. The model has weaker climate sensitivity than most GCMs, but comparable climate sensitivity to recent aqua-planet simulations of a global cloud-resolving model. The weak sensitivity is primarily due to an increase in low cloud fraction and liquid water in tropical regions of moderate subsidence as well as substantial increases in high-latitude cloud fraction. Copyright 2006 by the American Geophysical Union."
"55738957800;45761547800;","Toward mitigating the double ITCZ problem in NCAR CCSM3",2006,"10.1029/2005GL025229","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646461889&doi=10.1029%2f2005GL025229&partnerID=40&md5=c45fa87cd6fdb647faa146103dfb7a13","The appearance of a spurious Inter-Tropical Convergence Zone south of the equator in the eastern and central equatorial Pacific, in addition to the observed one north of the equator, is a common problem in coupled global climate models. The present study investigates this ""double ITCZ"" problem in the NCAR CCSM3. It shows that use of a modified Zhang-McFarlane convection scheme significantly mitigates the double ITCZ problem in boreal summer. This has a profound impact on the simulated sea surface temperature through cloud radiative forcing feedback. Both the warm bias in the southern ITCZ region and the cold bias in the cold tongue over the equator are reduced. Examination of the time series of precipitation, SST and surface energy fluxes shows that, depending on the convection parameterization used, double or single ITCZ emerges quickly within the first few months after the model start. Copyright 2006 by the American Geophysical Union."
"7007067997;7004346367;57203053317;13406672500;35464731600;6603452105;7402565763;13406162800;35273334200;","Aerosol indirect effect over the Indian Ocean",2006,"10.1029/2005GL025397","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646444906&doi=10.1029%2f2005GL025397&partnerID=40&md5=ec5131c7c9c7ea07541de754347c25f7","We analyze the MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data over the seas adjacent to the Indian sub-continent to investigate the effect of aerosols on the size distribution of cloud droplets and ice crystals (indirect aerosol effect). During the winter months of increased anthropogenic pollution we observe smaller sizes of cloud droplets in water clouds in agreement with the expected aerosol indirect effect. However, contrary to our expectations, we find that during episodes of increased pollution the effective radius of ice crystals is shifted toward the larger rather than smaller sizes. We propose a combination of natural seasonal variability of meteorological conditions and an ""inverse aerosol indirect effect"" caused by heterogeneous ice nucleation as a possible explanation of observed ice crystal growth. The ECHAM4 (European Center for Medium-Range Weather Forecast Hamburg version 4th generation GCM) results with heterogeneous ice nucleation reproduce the observed increase in ice crystal size during the enhanced pollution episodes. Copyright 2006 by the American Geophysical Union."
"6701450462;7006356035;","Amplification of the mesospheric diurnal tide in a doubled CO2 atmosphere",2006,"10.1029/2005GL025345","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646448763&doi=10.1029%2f2005GL025345&partnerID=40&md5=5a9a90a45d52d7c233bb5f2142096f65","The impact of doubled CO2 on the vertically propagating migrating diurnal tide in the mesosphere is studied using the Canadian Middle Atmosphere Model (CMAM), a coupled chemistry-climate model that extends from the Earth's surface to the lower thermosphere. A linear tidal model forced by the tidal heating from the CMAM is used to attribute cause and effect. The CMAM results exhibit a tidal temperature amplitude increase of up to 2 K in the equatorial upper mesosphere. This is attributed primarily to an increase in tropospheric solar heating which results from an increase in water vapor. Changes in stratospheric solar heating, radiative damping, tropospheric latent heating, background atmosphere, and clouds are found to have little impact. Copyright 2006 by the American Geophysical Union."
"6602244257;56744278700;7202252296;","Differing regional responses to a perturbation in solar cloud absorption in the SKYHI general circulation model",2006,"10.1029/2005JD006491","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646402035&doi=10.1029%2f2005JD006491&partnerID=40&md5=a5dd86375f3f5f7bba0eaaf8e4d7e76b","In this study we perform an idealized experiment to investigate the effect of solar absorption in clouds on climate using a general circulation model with prescribed sea surface temperatures, focusing on the manner of regional changes during the northern summer season. The response arising from this type of perturbation is akin to ""semidirect"" effects of absorbing aerosols, namely, dissipation of clouds owing to a high aerosol absorption in the cloud layers. In the experiment, we apply a similar perturbation to all low-cloud layers, reducing their single-scattering albedo to a value of 0.99, which enables us to isolate the effect of such solar absorption from other aerosol related influences. We find that in both midlatitude and equatorial regions, the reduction in low-cloud single-scattering albedo causes a reduction in low-cloud amount and a warming of the surface. However, the dynamical response of the system varies from one continental region to another. In the midlatitude regions of the United States and Europe/east Asia, the diabatic heating perturbation leads to the dissipation of low clouds, an increase in shortwave flux to the surface, an increase in horizontal heat advection, and an increase in atmospheric stability. In the tropical region of North Africa, the diabatic heating perturbation translates into an increase in convection, a decrease in stability, an increase in middle- and high-level clouds, and a reduction in shortwave flux to the surface. In agreement with previous studies, these results demonstrate the distinctive response of the tropical versus midlatitude regions to a similar solar perturbation. Copyright 2006 by the American Geophysical Union."
"7004160106;6602995001;57208455668;","Performance of two cloud-radiation parameterization schemes in the finite volume general circulation model for anomalously wet May and June 2003 over the continental United States and Amazonia",2006,"10.1029/2005JD006246","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646402583&doi=10.1029%2f2005JD006246&partnerID=40&md5=05f0db00e6c79f6a093459cb7aec3208","An objective assessment of the impact of a new cloud scheme, called Microphysics of Clouds with Relaxed Arakawa-Schubert Scheme (McRAS) (together with its radiation modules), on the finite volume general circulation model (fvGCM) was made with a set of ensemble forecasts that invoke performance evaluation over both weather and climate timescales. The performance of McRAS (and its radiation modules) was compared with that of the National Center for Atmospheric Research Community Climate Model (NCAR CCM3) cloud scheme (with its NCAR physics radiation). We specifically chose the boreal summer months of May and June 2003, which were characterized by an anomalously wet eastern half of the continental United States as well as northern regions of Amazonia. The evaluation employed an ensemble of 70 daily 10-day forecasts covering the 61 days of the study period. Each forecast was started from the analyzed initial state of the atmosphere and spun-up soil moisture from the first-day forecasts with the model. Monthly statistics of these forecasts with up to 10-day lead time provided a robust estimate of the behavior of the simulated monthly rainfall anomalies. Patterns of simulated versus observed rainfall, 500-hPa heights, and top-of-the-atmosphere net radiation were recast into regional anomaly correlations. The correlations were compared among the simulations with each of the schemes. The results show that fvGCM with McRAS and its radiation package performed discernibly better than the original fvGCM with CCM3 cloud physics plus its radiation package. The McRAS cloud scheme also showed a reasonably positive response to the observed sea surface temperature on mean monthly rainfall fields at different time leads. This analysis represents a method for helpful systematic evaluation prior to selection of a new scheme in a global model. Copyright 2006 by the American Geophysical Union."
"35180730000;6701378450;7004496562;6603798706;","Effects of aqueous organosulfur chemistry on particulate methanesulfonate to non-sea salt sulfate ratios in the marine atmosphere",2006,"10.1029/2005JD006326","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646350513&doi=10.1029%2f2005JD006326&partnerID=40&md5=e3136f4cc951fc250c2f364b135aba99","The oxidation of dimethyl sulfide (DMS, CH<inf>3</inf>SCH<inf>3</inf>) in the atmosphere could influence climate by affecting cloud condensation nuclei concentrations and cloud properties. This work focuses on elucidating the importance of DMS-cloud interactions, especially the poorly understood aqueous phase chemical transformations of DMS oxidation products. For this purpose, we incorporate an oxidation mechanism of atmospheric DMS and its products within the modeling framework of a trajectory ensemble model (TEM). Both marine cumulus and stratocumulus clouds are considered. It is found that the aqueous phase reactions of sulfur compounds contribute >97% of methanesulfonate (MS, CH<inf>3</inf>(O)S(O)O-) and >80% of non-sea salt sulfate (NSS) production in particles and that about 30% of total MS and NSS production is from the aqueous phase oxidation of the organosulfur compounds. The aqueous phase methanesulfinate (MSI, CH<inf>3</inf>S(O)O-) + Cl<inf>2</inf>- reaction is found to be more important than MSI + OH as an MS source. The MS + OH reaction could consume almost 20% of MS and produce about 8% of total NSS within 3 days under typical marine atmospheric conditions. Copyright 2006 by the American Geophysical Union."
"6506360840;57213743966;","How does climate change contribute to surface ozone change over the United States?",2006,"10.1029/2005JD005873","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646339923&doi=10.1029%2f2005JD005873&partnerID=40&md5=6f9140b851a76fdbe7dbe62c8caae0a1","The impact of climate change on U.S. surface ozone levels is investigated. We simulated two 10 year periods using the global chemical transport model MOZART-2 (Model of Ozone and Related chemical Tracers version 2): 1990-2000 and 2090-2100. In each case, MOZART-2 is driven by meteorology from the National Center for Atmospheric Research (NCAR) coupled Climate Systems Model (CSM) 1.0 forced with the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A1 scenario. During both periods the chemical emissions are fixed at 1990s levels, so that only changes in climate are allowed to impact ozone. The simulated surface ozone concentration during the 1990s is compared with observations from the Environmental Protection Agency's Aerometric Information Retrieval System (EPA AIRS) monitoring sites. Model-measurement correlations are high, but MOZART-2 overpredicts ozone especially over the eastern United States. The impact of climate change is calculated separately for background ozone and for the ozone generated through U.S. NO<inf>x</inf> emissions. Our results show that the response of ozone to climate change in polluted regions is not the same as in remote regions. MOZART-2 predicts a 0-2 ppbv decrease in background ozone in the future simulation over the United States but an increase in ozone produced internally within the United States of up to 6 ppbv. The decrease in background ozone is attributed to a future decrease in the lifetime of ozone in regions of low NO<inf>x</inf>. Over the western United States the decrease in background ozone approximately cancels the increase in locally produced ozone. As a result, the main impact of future climate change on ozone is centered over the eastern United States, where future ozone increases up to 5 ppbv. We predict that in the future over the northeast United States, up to 12 additional days each year will exceed the maximum daily 8-hour averaged ozone limit of 80 ppbv. Various climatic factors are identified which impact the net future increase in ozone over the United States including changes in temperature, water vapor, clouds, transport, and lightning NO<inf>x</inf>. Significant future changes are generally not found in planetary boundary layer height and precipitation. Copyright 2006 by the American Geophysical Union."
"35302065900;6603068094;7102084129;6701316460;25722217000;","Violent pyro-convective storm devastates Australia's capital and pollutes the stratosphere",2006,"10.1029/2005GL025161","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646352704&doi=10.1029%2f2005GL025161&partnerID=40&md5=d125416d889348a215712cc25d1e2651","Headline-making firestorms in southeast Australia in 2003, responsible for at least 500 destroyed buildings and four lost lives, culminated with pyro-cumulonimbus (pyroCb) ""eruptions"" that ravaged Canberra on 18 January. Here we reveal that in their 3-hour lifetime, the Canberra pyroCbs also produced a stratospheric smoke injection that perturbed the hemispheric background analogous to the theorized ""nuclear winter."" We use an unprecedented array of data to analyze the Canberra pyroCbs' distinctive stratospheric impact, microphysics, energetics, and surface manifestations - including suppressed precipitation, an F2 tornado, and black hail. Copyright 2006 by the American Geophysical Union."
"6603873573;7003591311;57200679067;36000595000;7006634316;36076994600;57203798762;7003729315;7402934750;","Comparison between lidar and nephelometer measurements of aerosol hygroscopicity at the Southern Great Plains Atmospheric Radiation Measurement site",2006,"10.1029/2004JD005646","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646364046&doi=10.1029%2f2004JD005646&partnerID=40&md5=a21e4d348e979d01c9f390bb12dafc6a","Aerosol hygroscopicity has a significant effect on radiative properties of aerosols. Here a lidar method, applicable to cloud-capped, well-mixed atmospheric boundary layers, is employed to determine the hygroscopic growth factor f(RH) under unperturbed, ambient atmospheric conditions. The data used for the analysis were collected under a wide range of atmospheric aerosol levels during both routine measurement periods and during the intensive operations period (IOP) in May 2003 at the Southern Great Plains (SGP) Climate Research Facility in Oklahoma, USA, as part of the Atmospheric Radiation Measurement (ARM) program. There is a good correlation (∼0.7) between a lidar-derived growth factor (measured over the range 85% RH to 96% RH) with a nephelometer-derived growth factor measured over the RH range 40% to 85%. For these RH ranges, the slope of the lidar-derived growth curve is much steeper than that of the nephelometer-derived growth curve, reflecting the rapid increase in particle size with increasing RH. The results are corroborated by aerosol model calculations of lidar backscatter and nephelometer equivalent f(RH) based on in situ aerosol size and composition measurements during the IOP. It is suggested that the lidar method can provide useful measurements of the dependence of aerosol optical properties on relative humidity and under conditions closer to saturation than can currently be achieved with humidified nephelometers. Copyright 2006 by the American Geophysical Union."
"35585698100;13610168000;55666342400;6505486068;7101846027;6603684590;6602097544;7006572336;57196499374;","Photoacoustic insight for aerosol light absorption aloft from meteorological aircraft and comparison with particle soot absorption photometer measurements: DOE Southern Great Plains climate research facility and the coastal stratocumulus imposed perturbation experiments",2006,"10.1029/2005JD005964","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646384944&doi=10.1029%2f2005JD005964&partnerID=40&md5=fbbc49f50c29516b63608eaf72852fae","Aerosol light absorption can be intense close to local sources such as wildland and oil fires, with smoke that disperses into the boundary layer and, with enough lift, into the upper atmosphere where it may be transported around the globe. Filter-based methods such as the Particle Soot Absorption Photometer (PSAP) are most commonly used to quantify aerosol light absorption aloft. This paper reports first measurements of aerosol light absorption aloft with photoacoustic instrumentation (PA). Three examples of aerosol light absorption are presented. The first one illustrates a case of detached layers aloft arising from intercontinental, interoceanic transport of smoke from wildland fires in Siberia to the North American continent and the measurement campaign held at the Department of Energy Atmospheric Radiation Measurement Program Climate Research Facility in north central Oklahoma. Then, two examples of intense local fire smoke light absorption from the Coastal Stratocumulus Imposed Perturbation Experiment near Marina, California, USA, are presented. The first local fire was an oil fire burning in a storage tank near Moss Landing, California, USA, and smoke from this fire was very dark, indicating a low single scattering albedo. By contrast, the second local fire was predominantly burning wood, vegetation, and structures near Fort Ord in Marina, California, USA, and the smoke was very bright, indicating a high single scattering albedo. In all examples, PA measurements at 676 nm were compared with those from a PSAP modified to measure at three wavelengths, including 660 nm. Copyright 2006 by the American Geophysical Union."
"6603211582;7003969611;7102546082;","The effect of chemical composition and size distribution of aerosol particles on droplet formation and albedo of stratocumulus clouds",2006,"10.1016/j.atmosenv.2005.11.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-32544455988&doi=10.1016%2fj.atmosenv.2005.11.012&partnerID=40&md5=946c576383bd0efe61c34ac2453673f2","A numerical model was applied to simulate the evolution of water droplets on aerosol particles with different sizes and chemical compositions. The detailed microphysical model was incorporated into a one-dimensional parcel model to investigate the indirect effects of aerosol particles on climate. The calculations were initiated with different aerosol size distributions observed during the field measurements in 1973-1976 and at the end of the 20th century in rural Hungary. The effect of changes in the characteristics of aerosol particles during this time period on the number concentration of water droplets formed was calculated at different cloud base updraft velocities. It was found that about 10% of sulfate particles and about 1% of organic aerosol particles with radius larger than 0.025 μm take part in drop formation if the updraft velocity is weak (0.1 m s-1). Mostly haze particles form on this type of aerosol particles in this case: the majority of cloud droplets come into being on sulfate particles. If the updraft velocity is 1 m s-1 at the cloud base, a larger fraction (≈30%) of the organic aerosol particles become activated. On the basis of our calculations, it is concluded that the observed modification of aerosol content resulted in a decrease in albedo of stratocumulus clouds of about 0.02 in the Central European region. If only the sulfate particles are considered, the corresponding albedo decrease is higher, about 0.03. The presence of soot in the aerosol particles, to some extent, mitigates the decrease of the albedo caused by the decrease of sulfate content. © 2005 Elsevier Ltd. All rights reserved."
"57191504846;16643212300;6603627233;6701905330;","The effect of the sea-ice zone on the development of boundary-layer roll clouds during cold air outbreaks",2006,"10.1007/s10546-005-6434-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746209328&doi=10.1007%2fs10546-005-6434-4&partnerID=40&md5=e055882dff8a86a78f2a26558fc63426","High latitude air-sea interaction is an important component of the earth's climate system and the exchanges of mass and energy over the sea-ice zone are complicated processes that, at present, are not well understood. In this paper, we perform a series of numerical experiments to examine the effect of sea-ice concentration on the development of high latitude boundary-layer roll clouds. The experiments are performed at sufficiently high spatial resolution to be able to resolve the individual convective roll clouds, and over a large enough domain to be able to examine the roll's downstream development. Furthermore the high spatial resolution of the experiments allows for an explicit representation of heterogeneity within the sea-ice zone. The results show that the sea-ice zone has a significant impact on the atmospheric boundary-layer development, which can be seen in both the evolution of the cloud field and the development of heat and moisture transfer patterns. In particular, we find the air-sea exchanges of momentum, moisture and heat fluxes are modified by the presence of the roll vortices (typically a 10% difference in surface heat fluxes between updrafts and downdrafts) and by the concentration and spatial distribution of the sea-ice. This suggests that a more realistic representation of processes over the sea-ice zone is needed to properly calculate the air-sea energy and mass exchange budgets. © Springer Science+Business Media, Inc. 2006."
"7102329065;6701606453;7004114883;","Rainfall climate regimes: The relationship of regional TRMM rainfall biases to the environment",2006,"10.1175/JAM2331.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646567812&doi=10.1175%2fJAM2331.1&partnerID=40&md5=52835dd815619ac205794bb2ca512eb0","Intercomparisons of satellite rainfall products have historically focused on the issue of global mean biases. Regional and temporal variations in these biases, however, are equally important for many climate applications. This has led to a critical examination of rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and precipitation radar (PR). Because of the time-dependent nature of these biases, it is not possible to apply corrections based on regionally defined characteristics. Instead, this paper seeks to relate PR-TMI differences to physical variables that can lead to a better understanding of the mechanisms responsible for the observed differences. To simplify the analysis, issues related to differences in rainfall detection and intensity are investigated separately. For clouds identified as raining by both sensors, differences in rainfall intensity are found to be highly correlated with column water vapor. Adjusting either TMI or PR rain rates based on this simple relationship, which is relatively invariant over both seasonal and interannual time scales, results in a 65%-75% reduction in the rms difference between seasonally averaged climate rainfall estimates. Differences in rainfall detection are most prominent along the midlatitude storm tracks, where widespread, isolated convection trailing frontal systems is often detected only by the higher-resolution PR. Conversely, over the East China Sea clouds below the ∼18-dBZ PR rainfall detection threshold are frequently identified as raining by the TMI. Calculations based on in situ aerosol data collected south of Japan support a hypothesis that high concentrations of sulfate aerosols may contribute to abnormally high liquid water contents within nonprecipitating clouds in this region. © 2006 American Meteorological Society."
"57203053317;7005465800;","Sensitivity studies of the importance of dust ice nuclei for the indirect aerosol effect on stratiform mixed-phase clouds",2006,"10.1175/JAS3662.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645986716&doi=10.1175%2fJAS3662.1&partnerID=40&md5=4588ded9cc82ff13fb71a8d915ae5999","New parameterizations of contact freezing and immersion freezing in stratiform mixed-phase clouds (with temperatures between 0° and -35°C) for black carbon and mineral dust assumed to be composed of either kaolinite (simulation KAO) or montmorillonite (simulation MON) are introduced into the ECHAM4 general circulation model. The effectiveness of black carbon and dust as ice nuclei as a function of temperature is parameterized from a compilation of laboratory studies. This is the first time that freezing parameterizations take the chemical composition of ice nuclei into account. The rather subtle differences between these sensitivity simulations in the present-day climate have significant implications for the anthropogenic indirect aerosol effect. The decrease in net radiation in these sensitivity simulations at the top of the atmosphere varies from 1 ± 0.3 to 2.1 ± 0.1 W m-2 depending on whether dust is assumed to be composed of kaolinite or montmorillonite. In simulation KAO, black carbon has a higher relevancy as an ice nucleus than in simulation MON, because kaolinite is not freezing as effectively as montmorillonite. In simulation KAO, the addition of anthropogenic aerosols results in a larger ice water path, a slightly higher precipitation rate, and a reduced total cloud cover. On the contrary, in simulation MON the increase in ice water path is much smaller and globally the decrease in precipitation is dominated by the reduction in warm-phase precipitation due to the indirect cloud lifetime effect. © 2006 American Meteorological Society."
"6701379896;7003922138;7006199823;7101632204;9939102400;7005213997;7102665209;7102620639;7101823091;7004343004;12809675900;6603275645;57208462871;6701385171;7401477391;6603715895;6506103893;7401595141;7005808242;6701618837;7103206141;7402064802;7003554208;7006735547;57081464900;57054407300;57208455668;57111001300;7005884486;7006003831;56744278700;7404210007;35514163500;8733579000;6508004743;6701631872;7103366892;7003802133;6602864692;8733579800;54382704000;55570248000;","GFDL's CM2 global coupled climate models. Part I: Formulation and simulation characteristics",2006,"10.1175/JCLI3629.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645219567&doi=10.1175%2fJCLI3629.1&partnerID=40&md5=e8eec3e3bd20e2a10e8d4e8fbba41979","The formulation and simulation characteristics of two new global coupled climate models developed at NOAA's Geophysical Fluid Dynamics Laboratory (GFDL) are described. The models were designed to simulate atmospheric and oceanic climate and variability from the diurnal time scale through multicentury climate change, given our computational constraints. In particular, an important goal was to use the same model for both experimental seasonal to interannual forecasting and the study of multicentury global climate change, and this goal has been achieved. Tw o versions of the coupled model are described, called CM2.0 and CM2.1. The versions differ primarily in the dynamical core used in the atmospheric component, along with the cloud tuning and some details of the land and ocean components. For both coupled models, the resolution of the land and atmospheric components is 2° latitude × 2.5° longitude; the atmospheric model has 24 vertical levels. The ocean resolution is 1° in latitude and longitude, with meridional resolution equatorward of 30° becoming progressively finer, such that the meridional resolution is 1/3° at the equator. There are 50 vertical levels in the ocean, with 22 evenly spaced levels within the top 220 m. The ocean component has poles over North America and Eurasia to avoid polar filtering. Neither coupled model employs flux adjustments. The co ntrol simulations have stable, realistic climates when integrated over multiple centuries. Both models have simulations of ENSO that are substantially improved relative to previous GFDL coupled models. The CM2.0 model has been further evaluated as an ENSO forecast model and has good skill (CM2.1 has not been evaluated as an ENSO forecast model). Generally reduced temperature and salinity biases exist in CM2.1 relative to CM2.0. These reductions are associated with 1) improved simulations of surface wind stress in CM2.1 and associated changes in oceanic gyre circulations; 2) changes in cloud tuning and the land model, both of which act to increase the net surface shortwave radiation in CM2.1, thereby reducing an overall cold bias present in CM2.0; and 3) a reduction of ocean lateral viscosity in the extratropics in CM2.1, which reduces sea ice biases in the North Atlantic. Both models have be en used to conduct a suite of climate change simulations for the 2007 Intergovernmental Panel on Climate Change (IPCC) assessment report and are able to simulate the main features of the observed warming of the twentieth century. The climate sensitivities of the CM2.0 and CM2.1 models are 2.9 and 3.4 K, respectively. These sensitivities are defined by coupling the atmospheric components of CM2.0 and CM2.1 to a slab ocean model and allowing the model to come into equilibrium with a doubling of atmospheric CO2. The output from a suite of integrations conducted with these models is freely available online (see http://nomads.gfdl.noaa.gov/). © 2006 American Meteorological Society."
"7005956183;7004692414;55254798500;7102490158;","The radiation budget of the atmosphere over the Arctic compiled from the ISCCP-FD data sets (preliminary results)",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745759772&partnerID=40&md5=17aec7b56963293e6d84b60b9ca75c82","The technological advancements of the past two to three decades enabled the establishment of space-borne observational systems to measure worldwide clouds and related radiation fields at the top of the atmosphere. This data when combined with further information on the thermodynamic state of the atmosphere and ground allows for estimates of the radiation budget at ground and within the atmosphere. This information is urgently required to calibrate the output of climate models and to understand current changes in the climate system. Results of the International Satellite Cloud Climatology Project (ISCCP) are here presented and compared with another but similar data set of the Global Energy and Water Cycle Experiment (GEWEX-SRB) and with ground-based measurements. This data describes details in space and time of the variability of radiation budget parameters at the surface and at the top of the atmosphere over the entire globe. Over the Arctic ice fields - our studies concern areas poleward of about 60°N - considerable uncertainties of more than 20 Wm-2 still exist in both the long-wave and short-wave budget components at ground. © 2006 National Institute of Polar Research."
"7403076976;6506825008;","Can lightning observations be used as an indicator of upper-tropospheric water vapor variability?",2006,"10.1175/BAMS-87-3-291","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645552412&doi=10.1175%2fBAMS-87-3-291&partnerID=40&md5=0f4f36611b0d8a1e3c5afffcf5331f8e","Lightning activity in thunderstorms is closely related to the intensity of vertical updrafts in deep convective clouds that also transport large amounts of moisture into the upper troposphere. Small changes in the amount of upper-tropospheric water vapor (UTWV) can have major implications for the Earth's climate. New evidence is presented showing a strong connection between the daily variability of tropical lightning activity and daily upper-tropospheric water vapor concentrations from the NCEP-NCAR reanalysis. Our results over the African continent show that the NCEP upper-tropospheric water vapor peaks one day after intense lightning activity in the Tropics. Given the many caveats related to the NCEP UTWV product over Africa, these results need to be interpreted with caution. However, since global lightning activity can be monitored from a few ground stations around the world via the Schumann resonances, we suggest the possible use of continuous lightning observations for studying the daily variability of upper-tropospheric water vapor. Whether lightning is related to UTWV on other spatial and temporal scales needs further investigation. ©2006 American Meteorological Society."
"55944537900;7005742190;","Experimental calibration of a cost-effective X-band weather radar for climate ecological studies in southern Ecuador",2006,"10.1016/j.atmosres.2005.06.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31844439164&doi=10.1016%2fj.atmosres.2005.06.005&partnerID=40&md5=f62ac6d37251b48e5428ad62be8701e1","In this paper setup, operational problems and a straightforward calibration approach for a cost-effective X-Band radar are presented. The LAWR (Local Area Weather Radar) system is based on conventional ship radar technology which is adapted to register rainfall within a range of about 60 km with a spatial resolution of 500 m per pixel. The instrument offers neither Doppler processing nor vertical scan capabilities but uses 20° wide (vertical) beam. The calibration suffers from an unfavorably distributed and very sparse rain gauge network, heavy clutter contamination of the signal and obstructions by surrounding terrain. A specific scaling approach is developed, that includes satellite data on cloud frequency and distribution, to overcome these limitations. Observed clutter is removed and missing values are replaced by bilinear interpolation of the undisturbed signals. A temporal and spatial bias of the radar signal is corrected using an omni-directional spatial distribution hypothesis. This is possible because of the location of the radar site in the transition zone between high rainfall on the eastern Andean slopes and low rainfall on the leeward side. A further limitation of the system is that the LAWR does not provide information on the measured reflectivity Z but dimensionless counts (8 bit resolution). Calibration is performed assuming a linear relation between radar output and rainfall as recommended by the systems manufacturer. The intercomparison of rain gauge and scatterometer data with calibrated radar rainfall reveals a good performance of the developed calibration approach. © 2005 Elsevier B.V. All rights reserved."
"13606163100;7102111067;57203596463;","What controls CCN seasonality in the Southern Ocean? A statistical analysis based on satellite-derived chlorophyll and CCN and model-estimated OH radical and rainfall",2006,"10.1029/2005GB002597","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646708557&doi=10.1029%2f2005GB002597&partnerID=40&md5=54f99185e9e7156cb37957c9cefa95cf","A 3-year time series set (from January 2002 to December 2004) of monthly means of satellite-derived chlorophyll (CHL) and cloud condensation nuclei (CCN), as well as model outputs of hydroxyl radical (OH), rainfall amount (RAIN), and wind speed (WIND) for the Southern Ocean (SO, 40°S-60°S) is analyzed in order to explain CCN seasonality. Chlorophyll is used as a proxy for oceanic dimethylsulfide (DMS) emissions since both climatological aqueous DMS and atmospheric methanesulfonate (MSA) concentrations are tightly coupled with chlorophyll seasonality over the Southern Ocean. OH is included as the main atmospheric oxidant of DMS to produce CCN, and rainfall amount as the main loss factor for CCN through aerosol scavenging. Wind speed is used as a proxy for sea salt (SS) particles production. The CCN concentration seasonality is characterized by a clear pattern of higher values during austral summer and lower values during austral winter. Linear and multiple regression analyses reveal high significant correlations between CCN and the product of chlorophyll and OH (in phase) and rainfall amount (in antiphase). Also, CCN concentrations are anticorrelated with wind speed, which shows very little variability and a slight wintertime increase, in agreement with the sea salt seasonality reported in the literature. Finally, the fraction of the total aerosol optical depth contributed by small particles (ETA) exhibits a seasonality with a 3.5-fold increase from austral winter to austral summer. The biogenic contribution to CCN is estimated to vary between 35% (winter) and 80% (summer). Sea salt particles, although contributing an important fraction of the CCN burden, do not play a role in controlling CCN seasonality over the SO. These findings support the central role of biogenic DMS emissions in controlling not only the number but also the variability of CCN over the remote ocean. Copyright 2006 by the American Geophysical Union."
"55707547000;14025414100;35254692200;","Predicting the temporal and spatial probability of orographic cloud cover in the Luquillo Experimental Forest in Puerto Rico using generalized linear (mixed) models",2006,"10.1016/j.ecolmodel.2005.07.031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31944440709&doi=10.1016%2fj.ecolmodel.2005.07.031&partnerID=40&md5=9f04f334ab92958c2a77e26440895e9d","We predicted the spatial pattern of hourly probability of cloud cover in the Luquillo Experimental Forest (LEF) in North-Eastern Puerto Rico using four different models. The probability of cloud cover (defined as ""the percentage of the area covered by clouds in each pixel on the map"" in this paper) at any hour and any place is a function of three topographic variables: aspect, slope and the difference between elevation and lifting condensation level. We chose the best models based on multiple statistics including the Akaike Information Criterion (AIC), scaled deviance and extra-dispersion scale. As a result, the generalized linear model (GLM) and one generalized linear mixed model (GLMM) with exponential spatial structure were the best candidate models. The probabilities of cloud cover in both our simulations and the observations increased with elevation, and were higher at night. They decreased in the morning after the sun rose until early afternoon, and then increased again for the rest of the day until night, apparently in response to the movement of the lifting condensation level. Two types of satellite images were available to calibrate our models: the higher spatial resolution, but expensive and infrequent Landsat-7 Enhanced Thermal Mapper plus (ETM+) images and the frequent, free, but low spatial resolution Moderate Resolution Imaging Spectroradiometer (MODIS) images. The derived probabilities of cloud cover when calibrated to the two types of remote sensing images were very similar, which justifies our using the free MODIS images instead of the Landsat images to calibrate the models. We applied the model to all months and the results indicated in agreement with the data that the probability of cloud cover is less during the dry season, higher in wet season and moderate for the rest of the year. We found our models could usually predict the probability of cloud cover for each 100 m in elevation level at a certain time with an index of agreement (IoA) of 0.560-0.919 and at a certain location over a day with an IoA of 0.940-0.994, indicating a medium to good model simulation at that particular time or location. © 2005 Elsevier B.V. All rights reserved."
"7005742190;55944537900;12795094500;55628589750;","Cloud occurrence and cloud properties in Ecuador",2006,"10.3354/cr030133","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645295482&doi=10.3354%2fcr030133&partnerID=40&md5=411c861e412c1e490283256c492cdbe7","We used a 3 yr data set of NOAA-AVHRR (Advanced Very High Resolution Radiometer) imagery to investigate cloud frequency, cloud-top height and cloud liquid water path for the Ecuadorean area, with special reference to a specific region in the Andes of southern Ecuador. In general, the seasonal cycle of cloudiness is significantly correlated to the spatial occurrence of the rainy seasons. However, we found that the complex topography of the Andes with dynamic effects at the windward and lee sides, as well as thermal breeze-systems, cause a specific spatial structure of cloud frequency and cloud properties. For instance, the eastern Andean slopes are mainly affected by a strong dynamic barrage effect of the easterlies, where a line of high cloud frequency occurs in the area of the Andes-occurring system (AOS) rain band. Average cloud-top height reveals a clear division between the Pacific area west of the western Cordillera chain, characterised by lower and more stratiform clouds, and the eastern parts of the country where an increase in average cloud-top height towards the Amazon indicates an intensification of convective cloud formation processes. This corresponds with the higher amounts of cloud liquid path over the Amazon, which illustrates that the cloud water cycle is more intensive in comparison to the Ecuadorian coastal plains. © Inter-Research 2006."
"6603585313;7406741310;55495155800;6602844274;","Annual cycles of surface shortwave radiative fluxes",2006,"10.1175/JCLI3625.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645220387&doi=10.1175%2fJCLI3625.1&partnerID=40&md5=7b90e050e6ea0c89ee8a222f8532917d","The annual cycles of surface shortwave flux are investigated using the 8-yr dataset of the surface radiation budget (SRB) components for the period July 1983-June 1991. These components include the downward, upward, and net shortwave radiant fluxes at the earth's surface. The seasonal cycles are quantified in terms of principal components that describe the temporal variations and empirical orthogonal functions (EOFs) that describe the spatial patterns. The major part of the variation is simply due to the variation of the insolation at the top of the atmosphere, especially for the first term, which describes 92.4% of the variance for the downward shortwave flux. However, for the second term, which describes 4.1% of the variance, the effect of clouds is quite important and the effect of clouds dominates the third term, which describes 2.4% of the variance. To a large degree the second and third terms are due to the response of clouds to the annual cycle of solar forcing. For net shortwave flux at the surface, similar variances are described by each term. The regional values of the EOFs are related to climate classes, thereby defining the range of annual cycles of shortwave radiation for each climate class."
"7404142321;7003976079;7004764167;7201485519;6701715507;7004033942;35509639400;7004714030;8979277400;6506103893;7003554208;26643217800;12241892400;8937991200;8924140900;7004034323;7406514318;","Evaluation of a component of the cloud response to climate change in an intercomparison of climate models",2006,"10.1007/s00382-005-0067-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-32444443394&doi=10.1007%2fs00382-005-0067-7&partnerID=40&md5=1f276eb38c36e106a4cb861522ce663b","Most of the uncertainty in the climate sensitivity of contemporary general circulation models (GCMs) is believed to be connected with differences in the simulated radiative feedback from clouds. Traditional methods of evaluating clouds in GCMs compare time-mean geographical cloud fields or aspects of present-day cloud variability, with observational data. In both cases a hypothetical assumption is made that the quantity evaluated is relevant for the mean climate change response. Nine GCMs (atmosphere models coupled to mixed-layer ocean models) from the CFMIP and CMIP model comparison projects are used in this study to demonstrate a common relationship between the mean cloud response to climate change and present-day variability. Although atmosphere-mixed-layer ocean models are used here, the results are found to be equally applicable to transient coupled model simulations. When changes in cloud radiative forcing (CRF) are composited by changes in vertical velocity and saturated lower tropospheric stability, a component of the local mean climate change response can be related to present-day variability in all of the GCMs. This suggests that the relationship is not model specific and might be relevant in the real world. In this case, evaluation within the proposed compositing framework is a direct evaluation of a component of the cloud response to climate change. None of the models studied are found to be clearly superior or deficient when evaluated, but a couple appear to perform well on several relevant metrics. Whilst some broad similarities can be identified between the 60°N-60°S mean change in CRF to increased CO2 and that predicted from present-day variability, the two cannot be quantitatively constrained based on changes in vertical velocity and stability alone. Hence other processes also contribute to the global mean cloud response to climate change. © Springer-Verlag 2005."
"36812255500;7003708056;7006211890;7003880283;","Development of a detailed microphysics cirrus model tracking aerosol particles' histories for interpretation of the recent INCA campaign",2006,"10.1175/JAS3656.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645095920&doi=10.1175%2fJAS3656.1&partnerID=40&md5=e859fdfaca84da9c880989d6b1de558a","Cirrus clouds play an important role in the earth's energy balance. To quantify their impact, information is needed on their microstructure and more precisely on the number and size of the ice crystals. With the anthropogenic activity, more and more aerosol particles and water vapor are released even at the altitude where cirrus clouds are formed. Cirrus clouds formed in a polluted air mass may have different microphysical properties and, therefore, a different impact on the climate system via the changed radiative properties compared to background cirrus clouds. To study this aspect, the European project called the Interhemispheric Differences in Cirrus Properties due to Anthropogenic Emissions (INCA) measured the microphysical properties of cirrus clouds together with the physical and chemicals properties of aerosol particles in clean air (at Punta Arenas, Chile) and polluted air (at Prestwick, Scotland). The goal of the present work was to develop a detailed microphysics model for cirrus clouds for the interpretation and the generalization of the INCA observations. This model considers moist aerosol particles through the Externally Mixed (EXMIX) model, so that the chemical composition of solution droplets can be followed. Ice crystal formation is described through homogeneous or heterogeneous nucleation. The crystals then grow by deposition. With this model, the interactions between the microphysical processes, simulated ice crystal concentrations, and dimensional distributions of the INCA observations were studied, and explanations were provided for the observed differences between background and polluted cirrus clouds. © 2006 American Meteorological Society."
"7203085045;7007160862;22975069200;57201235812;","Surface cloud forcing in the east Pacific stratus deck/cold tongue/ITCZ complex",2006,"10.1175/JCLI3620.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645236726&doi=10.1175%2fJCLI3620.1&partnerID=40&md5=a97577c203c619c129d727b045a83275","Data from the Eastern Pacific Investigation of Climate Studies (EPIC) mooring array are used to evaluate the annual cycle of surface cloud forcing in the far eastern Pacific stratus cloud deck/cold tongue/ intertropical convergence zone complex. Data include downwelling surface solar and longwave radiation from 10 EPIC-enhanced Tropical Atmosphere Ocean (TAO) moorings from 8°S, 95°W to 12°N,95°W, and the Woods Hole Improved Meteorology (IMET) mooring in the stratus cloud deck region at 20°S, 85°W. Surface cloud forcing is defined as the observed downwelling radiation at the surface minus the clear-sky value. Solar cloud forcing and longwave cloud forcing are anticorrelated at all latitudes from 12°N to 20°S: clouds tended to reduce the downward solar radiation and to a lesser extent increase the downward longwave radiation at the surface. The relative amount of solar radiation reduction and longwave increase depends upon cloud type and varies with latitude. A statistical relationship between solar and longwave surface cloud forcing is developed for rainy and dry periods and for the full record length in six latitudinal regions: northeast tropical warm pool, ITCZ, frontal zone, cold tongue, southern, and stratus deck regions. The buoy cloud forcing observations and empirical relations are compared with the International Satellite Cloud Climatology Project (ISCCP) radiative flux data (FD) dataset and are used as benchmarks to evaluate surface cloud forcing in the NCEP Reanalysis 2 (NCEP2) and 40-yr ECMWF Re-Analysis (ERA40). ERA-40 and NCEP2 cloud forcing (both solar and longwave) showed large discrepancies with observations, being too large in the ITCZ and equatorial regions and too weak under the stratus deck at 20°S and north to the equator during the cool season from July to December. In particular the NCEP2 cloud forcing at the equator was nearly identical to the ITCZ region and thus had significantly larger solar cloud forcing and smaller longwave cloud forcing than observed. The net result of the solar and longwave cloud forcing deviations is that there is too little radiative warming in the ITCZ and southward to 8°S during the warm season and too much radiative warming under the stratus deck at 20°S and northward to the equator during the cold season."
"12144461400;7004390158;12143775300;12143985500;36870160800;14123161200;12143017100;8558968300;7102193013;13404664500;7402345338;13404531500;36848436500;","Changes in the Baiu frontal activity in the future climate simulated by super-high-resolution global and cloud-resolving regional climate models",2006,"10.2151/jmsj.84.199","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646399466&doi=10.2151%2fjmsj.84.199&partnerID=40&md5=c5d9920ecd9359a8ba8190bd17428ca1","Changes in the Baiu frontal activity in the future climate are examined, making use of super-high-resolution global and cloud-resolving regional climate models (20-km-mesh AGCM and 5-km-mesh NHM). In the present study, the focus is on the lengthened duration of the Baiu, and the characteristics of the precipitation during the Baiu season in the future climate. First, 10-year global-scale simulations of the present, and future climates are conducted by the 20-km-mesh AGCM. The present climate simulation accurately reproduces the northward shift of the Baiu front with time, and the end of the Baiu season around Japan. In the future climate, the Pacific anticyclone remains at the south of the Japan islands even late in July, resulting in the obscure migration of the Baiu front to the north and the lengthened Baiu season. Second, regional climate simulations are conducted by the 5-km-mesh NHM covering East Asia, in order to investigate the small-scale response to large-scale conditions, simulated by the 20-km-mesh AGCM. While the rainfall does not vary in June between the present and future climates, there is more rainfall in July in the future climate. Moreover, the frequency of the precipitation greatly increases with the intensity of the precipitation in July in the future climate simulation. In order to investigate the typical size of the precipitation systems that bring rainfall during the Baiu season, precipitation systems are classified according to the area coverage of the systems. Precipitation systems with an area larger than 90,000 km2 are more frequently seen in July in the future climate, than in the present climate, which corresponds to more rainfall. The increase of the large system in July is most remarkable in the vicinity of Kyushu Island, and the baroclinicity in that area is stronger in the future climate. © 2006, Meteorological Society of Japan."
"26643251000;","Modeling of light depolarization by cubic and hexagonal particles in noctilucent clouds",2006,"10.1016/j.atmosres.2005.06.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30544432618&doi=10.1016%2fj.atmosres.2005.06.002&partnerID=40&md5=3927c6f5342e70c5ff5b6ce707bcbdfb","Noctilucent clouds (NLCs) play an important indicative role in the physics of the summer polar mesopause. They consist of tiny ice crystals with characteristic dimensions generally smaller than 200 nm. However, the predominant shape of particles is not known. Therefore, biases in the size of crystals obtained from ground and space by light scattering and polarimetric techniques in the assumption of spherical scatterers can be considerable. This is due to the influence of shape effects on the scattering characteristics of particles. We test the assumption of the hexagonal and cubical particles as candidates for the predominant shapes of particles in NLCs using Maxwell electromagnetic theory to calculate the linear depolarization ratio (LDR). We compare results of recent measurements of LDRs with our calculations. Generally, theory and experiments agree very well at the NLC peak. The shape of crystals close to the cloud top cannot be explained by the model of compact particles. Relatively high light depolarization ratios detected from the upper part of the NLC are in agreement with models of elongated needle-like particles or particles having dimensions much larger than those usually attributed to NLC events. © 2005 Elsevier B.V. All rights reserved."
"6603789748;55423922000;13008018200;7102875670;","The COST 720 temperature, humidity, and cloud profiling campaign: TUC",2006,"10.1127/0941-2948/2006/0095","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646072162&doi=10.1127%2f0941-2948%2f2006%2f0095&partnerID=40&md5=c901c6b770994354b0acf245062ba96e","The international COST 720 Temperature, hUmidity, and Cloud (TUC) profiling experiment was organized over three months in winter 2003/2004 at Payerne, Switzerland. Various in-situ and active/passive ground-based remote sensing systems, including three microwave radiometers, a cloud radar and a wind profiler, were operated at the same location. The experiment has delivered a dataset for ground-based remote sensing measurements of winter conditions in the lower troposphere, including fog formation, development and erosion in the boundary layer. The data are being used to test atmospheric profiling products derived from integration of the various measurements. One example is fog/low cloud top and base derived from 78 GHz frequency-modulated continuous wave (FMCW) cloud radar and laser ceilometer measurements. The paper first describes the TUC experiment and the systems involved, including a brief analysis of the radiosoundings quality. An example is then used to show the ability of ground-based remote sensing systems to automatically determine the stratus base and top. Finally an overview of the publications related to the experiment is presented. © Gebrüder Borntraeger, Berlin, Stuttgart 2006."
"7102128820;6603463248;7007114756;","The retrieval of ice water content from radar reflectivity factor and temperature and its use in evaluating a mesoscale model",2006,"10.1175/JAM2340.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645284930&doi=10.1175%2fJAM2340.1&partnerID=40&md5=c1a1ab593ffcdca887b8ef126050d2f6","Ice clouds are an important yet largely unvalidated component of weather forecasting and climate models, but radar offers the potential to provide the necessary data to evaluate them. First in this paper, coordinated aircraft in situ measurements and scans by a 3-GHz radar are presented, demonstrating that, for stratiform midlatitude ice clouds, radar reflectivity in the Rayleigh-scattering regime may be reliably calculated from aircraft size spectra if the ""Brown and Francis"" mass-size relationship is used. The comparisons spanned radar reflectivity values from -15 to +20 dBZ, ice water contents (IWCs) from 0.01 to 0.4 g m-3, and median volumetric diameters between 0.2 and 3 mm. In mixed-phase conditions the agreement is much poorer because of the higher-density ice particles present. A large midlatitude aircraft dataset is then used to derive expressions that relate radar reflectivity and temperature to ice water content and visible extinction coefficient. The analysis is an advance over previous work in several ways: the retrievals vary smoothly with both input parameters, different relationships are derived for the common radar frequencies of 3, 35, and 94 GHz, and the problem of retrieving the long-term mean and the horizontal variance of ice cloud parameters is considered separately. It is shown that the dependence on temperature arises because of the temperature dependence of the number concentration ""intercept parameter"" rather than mean particle size. A comparison is presented of ice water content derived from scanning 3-GHz radar with the values held in the Met Office mesoscale forecast model, for eight precipitating cases spanning 39 h over southern England. It is found that the model predicted mean IWC to within 10% of the observations at temperatures between -30° and -10°C but tended to underestimate it by around a factor of 2 at cooler temperatures. © 2006 American Meteorological Society."
"6603398116;7005453346;6603561402;","Variability of precipitation intensity: Sensitivity to treatment of moist convection in an RCM and a GCM",2006,"10.1007/s00382-005-0076-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-32444442980&doi=10.1007%2fs00382-005-0076-6&partnerID=40&md5=0dc80284e7a34a88a300ecaaa6e873e4","The present study investigates the sensitivity of the frequency distribution of precipitation rates to the closure employed in the penetrative mass flux cumulus parameterization of Zhang and McFarlane in the Canadian regional climate model (CRCM) and in the Canadian Centre for Climate Modelling and Analysis third generation global atmospheric general circulation model (AGCM3). The effects of an alternative prognostic closure for mass flux cumulus parameterization in place of the original diagnostic closure are investigated. A set of experiments is performed in which changes in the frequency distribution of precipitation rates and cloud base mass-flux are examined as a function of the parameters that define each closure scheme. The relationship between the frequency distribution of precipitation and cloud base mass flux is examined and a self-consistent relation is found when the depth of convection is taken into account. Experiments performed with the prognostic closure favor relatively strong cloud base mass-flux and deep penetrative convection with relatively more intense convective precipitation. The mean of the frequency distribution of convective precipitation is larger and the heavier events become more intense. Also, experiments performed with the prognostic closure favor less frequent convective activity. However these changes in the distribution of convective component of precipitation are generally offset by opposite changes in the distribution of the resolved large-scale component of precipitation, resulting in relatively smaller changes in total precipitation. The altered partition of precipitation between convective and large-scale components is found to alter the energy balance and the thermodynamic equilibrium structure of the troposphere. The robustness found in the CRCM results regarding the sensitivity of the frequency distribution of precipitation to changes in the closure of the deep convection parameterization is investigated by performing a similar analysis of AGCM3 simulations. A remarkable similarity of AGCM3 and CRCM results is found suggesting that the closure sensitivity identified in this study is robust. © Springer-Verlag 2005."
"7005246513;7404574877;6603246540;35609878300;6701633085;6603858896;","Impact of new solar radiation parameterization in the Eta model on the simulation of summer climate over South America",2006,"10.1175/JAM2342.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646567485&doi=10.1175%2fJAM2342.1&partnerID=40&md5=71552433006dacaf1a3f099245cdc175","The regional Eta workstation (WS) model with horizontal resolution of 40 km has been integrated over South America for January 2003. The NCEP-DOE Reanalysis II was used for initial and lateral boundary conditions. The comparison of the model-simulated and satellite-derived values of monthly mean incident solar radiation at the surface demonstrates that the former values are larger by 20%-30% over the entire region. To improve the surface flux representation in the model, a new solar radiation scheme has been implemented in it. An offline comparison of the original and the new radiation schemes with the detailed line-by-line method demonstrates a higher accuracy for the new scheme. With the new scheme, the model-simulated incident solar radiation at the surface is in a better agreement with the satellite-derived data. Nevertheless, a noticeable systematic difference of 10%-20% still remains, probably because of the incorrect description of cloud parameters in the model. The lower incident solar radiation in the new version of the model causes a decrease of near-surface air temperature by 0.1°-1°C and a decrease of precipitation rate by up to 20%-30% over most of the continent. The increase in the simulated incident solar radiation and temperature is found in the region of the South Atlantic convergence zone, which is responsible for the enhanced cloudiness and precipitation in the central and southeastern parts of Brazil during summer. The model results are compared with observational data of meteorological stations, the Global Precipitation Climatology Project (GPCP), and the South American Low-Level Jet Experiment (SALLJEX) and are discussed. © 2006 American Meteorological Society."
"7006789912;7004179648;","Solar flux in Saturn's atmosphere: Penetration and heating rates in the aerosol and cloud layers",2006,"10.1016/j.icarus.2005.10.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30744464394&doi=10.1016%2fj.icarus.2005.10.009&partnerID=40&md5=b396fc46232279d163df7cbfca4eaf23","In this work, we describe an analysis of the internal solar radiation fields in Saturn's atmosphere. The aim of this paper is to study how the solar radiation flux in optical wavelengths (0.25-1.0 μm) is attenuated, primarily by the effect of the aerosols located close to the tropopause level, retrieving also the corresponding solar heating rates. We use a doubling-adding method and previous results on the vertical cloud and haze structure of Saturn's atmosphere. Our study shows that the maximum penetration level (∼250 mbar) for these wavelengths is substantially higher than previously expected because of the huge optical thickness of the tropospheric haze described in all vertical cloud structure models. We compare our results with previous estimates and parameterizations for seasonal climate models and propose a new approach for future models, with an intense and concentrated heating rate close to the top level of the tropospheric haze. Given that our spectral range accounts for about the 70% of the total solar flux, and using previous estimates for the penetration levels of infrared radiation in Saturn's atmosphere, we conclude solar radiation effect is negligible at levels below 600 mbar. This result is fundamental for understanding the role of solar radiation in the general atmospheric circulation of Saturn. © 2005 Elsevier Inc. All rights reserved."
"6602159464;6701656335;7202803069;7005206687;6603504366;","Daily precipitation over Southern Africa: A new resource for climate studies",2006,"10.1175/JHM477.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645543012&doi=10.1175%2fJHM477.1&partnerID=40&md5=9f41a55a8097fb79e20e7bc80ff04199","This paper describes a new high-resolution multiplatform multisensor satellite rainfall product for southern Africa covering the period 1993-2002. The microwave infrared rainfall algorithm (MIRA) employed to generate the rainfall estimates combines high spatial and temporal resolution Meteosat infrared data with infrequent Special Sensor Microwave Imager (SSM/I) overpasses. A transfer function relating Meteosat thermal infrared cloud brightness temperatures to SSM/I rainfall estimates is derived using collocated data from the two instruments and then applied to the full coverage of the Meteosat data. An extensive continental-scale validation against synoptic station data of both the daily MIRA precipitation product and a normalized geostationary IR-only Geostationary Operational Environmental Satellite (GOES) precipitation index (GPI) demonstrates a consistent advantage using the former over the latter for rain delineation. Potential uses for the resulting high-resolution daily rainfall dataset are discussed. © 2006 American Meteorological Society."
"6701633609;57214689006;7404941532;8502048800;55603015900;","Transgenic Spartina alterniflora for phytoremediation",2006,"10.1007/s10653-005-9019-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745870140&doi=10.1007%2fs10653-005-9019-8&partnerID=40&md5=214fe106d4bcccb06aab52b009b6aaa9","Perennial monoculture forming grasses are very important natural remediators of pollutants. Their genetic improvement is an important task because introduction of key transgenes can dramatically improve their remediation potential. Transfer of key genes for mercury phytoremediation into the salt marsh cordgrass (Spartina alterniflora) is reported here. S. alterniflora plays an important role in the salt marsh by cycling of elements, both nutrients and pollutants, protects the coastline from erosion, is a keystone species in the salt marsh supporting a large food web, which in turn supports a significant segment of economy, including tourism, has an impact on cloud formation and consequently on global weather, and is thus an ecologically important species relevant for our life-support systems. Embryogenic callus of S. alterniflora was co-inoculated with a pair of Agrobacterium strains LBA4404 carrying the organomercurial lyase (merB) and mercuric reductase (merA) genes, respectively, in order to co-introduce both the merA and the merB genes. Seven stable geneticin resistant lines were recovered. The presence of merA and merB genes was verified by PCR and Southern blotting. All but one transgenic lines contained both the merA and the merB sequences proving that co-introduction into Spartina of two genes from separate Agrobacterium strains is feasible and frequent, although the overall frequency of transformation is low. Northern blotting showed differences in relative expression of the two transgenes among individual transformants. The steady-state RNA levels appeared to correlate with the phenotype. Line #7 showed the highest resistance to HgCl2 (up to 500 μM), whereas line #3 was the most resistant to phenylmercuric acetate (PMA). Wild-type (WT) callus is sensitive to PMA at 50μM and to HgCl2 at 225μM. © Springer Science+Business Media, Inc. 2006."
"56611366900;7005862399;7003842561;","Analytical expression for the relative dispersion of the cloud droplet size distribution",2006,"10.1029/2005GL024052","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644753139&doi=10.1029%2f2005GL024052&partnerID=40&md5=b246e4949c6bc8bd50e89f20e86880af","An analytical expression that relates the relative dispersion (ratio of standard deviation to mean radius) of the cloud droplet size distribution to CCN spectra and updraft velocity is derived from adiabatic growth theory of cloud droplets. Coupled with the Twomey expression for droplet concentration, the analytical expression is used to examine the relationship of relative dispersion to droplet concentration under different combinations of CCN spectra and updraft velocities. These analytical results compare favorably with the corresponding simulations of an adiabatic parcel model. The analytical expression theoretically demonstrates that an increase in aerosol loading (CCN concentration) leads to concurrent increases in the droplet concentration and relative dispersion whereas a larger updraft velocity leads to a higher droplet concentration but a smaller relative dispersion. Copyright 2006 by the American Geophysical Union."
"6603422104;7004540083;","Climate feedback implied by observed radiation and precipitation changes with midlatitude storm strength and frequency",2006,"10.1029/2005GL024513","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644763282&doi=10.1029%2f2005GL024513&partnerID=40&md5=7a667792066421df172b768baa6813ef","Current climate observations are used to quantify the relationships between midlatitude storm strength and frequency and radiation and precipitation properties. Then, the derived radiation/ precipitation-storm relationships along with the midlatitude storm changes with climate-warming predicted by a climate model are used to determine the radiation and precipitation changes resulting from an increase in midlatitude storm intensity and a decrease in midlatitude storm frequency. Increases in midlatitude storm intensity produce shortwave cooling and longwave warming while decreases in storm frequency produce the opposite effects. When the two changes are added together the increase in storm strength dominates producing a shortwave cooling effect of 0-3.5 W/m2 and a longwave warming effect of 0.1-2.2 W/ m2. For precipitation, the increase in storm intensity also dominates the decrease in storm frequency and produces an increase in precipitation of 0.05-0.08 mm/day. Copyright 2006 by the American Geophysical Union."
"12781521700;7003772221;13611202300;56235579400;7201472576;6602775390;","Clouds and 7Be: Perusing connections between cosmic rays and climate",2006,"10.1029/2005JD005903","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644932640&doi=10.1029%2f2005JD005903&partnerID=40&md5=8662e4e8238e34a46b52bc409d52e643","Time series data on 7Be, precipitation, temperature, and satellite imagery of cloud cover over Scandinavia, together with cosmic ray and sunspot activity, were used to elucidate the relationship between cosmic rays and clouds, and ultimately climate change. The results indicate a coherent negative correlation between total cloud cover and 7Be on intrdseasonal, seasonal, and decadal scales. Although the reasons behind this correlation are unclear, a full-scale implication of this feature is in the possible use of 7Be and 10Be records for proxy paleo-reconstruction of total cloud cover. This is a strongly needed, but generally difficult to quantify parameter in climate models. Copyright 2006 by the American Geophysical Union."
"36627352900;7203054240;7202155374;","Rainfall and its seasonality over the Amazon in the 21st century as assessed by the coupled models for the IPCC AR4",2006,"10.1029/2005JD006355","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644936408&doi=10.1029%2f2005JD006355&partnerID=40&md5=bc8974f764821ea622f5511936101b5a","The global climate models for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) predict very different changes of rainfall over the Amazon under the SRES A1B scenario for global climate change. Five of the eleven models predict an increase of annual rainfall, three models predict a decrease of rainfall, and the other three models predict no significant changes in the Amazon rainfall. We have further examined two models. The UKMO-HadCM3 model predicts an El Niño-like sea surface temperature (SST) change and warming in the northern tropical Atlantic which appear to enhance atmospheric subsidence and consequently reduce clouds over the Amazon. The resultant increase of surface solar absorption causes a stronger surface sensible heat flux and thus reduces relative humidity of the surface air. These changes decrease the rate and length of wet season rainfall and surface latent heat flux. This decreased wet season rainfall leads to drier soil during the subsequent dry season, which in turn can delay the transition from the dry to wet season. GISS-ER predicts a weaker SST warning in the western Pacific and the southern tropical Atlantic which increases moisture transport and hence rainfall in the Amazon. In the southern Amazon and Nordeste where the strongest rainfall increase occurs, the resultant higher soil moisture supports a higher surface latent heat flux during the dry and transition season and leads to an earlier wet season onset. Copyright 2006 by the American Geophysical Union."
"57200926681;55505923400;","A climatological-dynamical analysis associated with precipitation around the southern part of the Himalayas",2006,"10.1029/2005JD006197","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644944355&doi=10.1029%2f2005JD006197&partnerID=40&md5=28d2ac9f9ccb7efba71ce6133d9fff49","The precipitation variability and circulation characteristics around the Himalayas are examined using the Tropical Rainfall Measuring Mission (TRMM) data, the Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment (GAME) reanalysis, National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis, and some of the Indian radiosonde data sets. The observation by precipitation radar on board the TRMM satellite reveals an afternoon maximum of precipitation during the premonsoon season and midnight-early morning maximum during the summer monsoon season over the southern slopes of the Himalayas. The data also shows that the morning precipitation moves southward in the mature monsoon season. The GAME reanalysis reveals a robust diurnal cycle of the atmospheric system that is coherent with the diurnal cycle of precipitation around the southern slopes of the Himalayas. The significant increase of moisture due to the southeasterly wind in the mature monsoon season seems to produce favorable conditions for the midnight-early morning rain. The down-valley wind at midnight probably triggers moist convection. The radiative cooling at the top of clouds may enhance the convection. The precipitation associated with the moist convection seems to generate a cold pool, which results in a density current. The downslope movement of the density current probably induces the southward movement of the precipitation system in the morning. Copyright 2006 by the American Geophysical Union."
"57202891769;","An alternative method to calculate cloud radiative forcing: Implications for quantifying cloud feedbacks",2006,"10.1029/2005GL024723","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644631351&doi=10.1029%2f2005GL024723&partnerID=40&md5=123ed1054dc3c2309f92eef2e8743c7d","A modification to the traditional cloud radiative forcing (CRF) formula is presented. This alternative approach uses incident rather than absorbed-solar radiation to calculate shortwave cloud radiative forcing at the surface. By removing the competing influence of surface albedo on CRF, the new formula more effectively isolates the impact of clouds and cloud changes under different climatic regimes. The removal of surface albedo effects makes the change in CRF a more useful measure of cloud feedback, although other factors (such as changes in clearsky solar absorption) can still muddle the interpretation. I present examples from GCM greenhouse simulations that demonstrate how this new formula can help to differentiate between actual cloud feedbacks versus apparent ones induced by snow and ice meltback using the traditional CRF equation. The results suggest that changes in surface albedo contribute approximately 20 to 40% of the high-latitude CRF anomaly using the standard formula applied to an equilibrium 2 × CO2 simulation and about 50% to the greater Arctic when used on 21st-century transient greenhouse experiments. Copyright 2006 by the American Geophyical Union."
"26643250500;7102988363;57203053317;","Physically based parameterization of cirrus cloud formation for use in global atmospheric models",2006,"10.1029/2005JD006219","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33144489565&doi=10.1029%2f2005JD006219&partnerID=40&md5=bc814b24f7db2c552b40cf839aab5fb1","Motivated by the need to study the climatic impact of aerosol-related cirrus cloud changes, a physically based parameterization scheme of ice initiation and initial growth of ice crystals in young cirrus clouds has been developed. The scheme tracks the number density and size of nucleated ice crystals as a function of vertical wind speed, temperature, ice saturation ratio, aerosol number size distributions, and preexisting cloud ice, allowing for competition between heterogeneous ice nuclei and liquid aerosol particles during freezing. Predictions of the parameterization are compared with numerical parcel simulations of ice nucleation and growth from atmospheric aerosols, with a special focus on explaining the indirect effects of ice nuclei on the properties of young cirrus clouds. The uncertainties of the parameterization are discussed and its implementation in a general circulation model is briefly outlined. This new scheme establishes a flexible framework for a comprehensive assessment of indirect aerosol effects on and properties of cirrus clouds in global climate, chemistry transport, and weather forecast models. Copyright 2006 by the American Geophysical Union."
"11139640100;35376591700;6602478960;7004178759;","Odin/OSIRIS limb observations of polar mesospheric clouds in 2001-2003",2006,"10.1016/j.jastp.2005.08.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30344484562&doi=10.1016%2fj.jastp.2005.08.004&partnerID=40&md5=6f4dbddf8307f204f3c196fc5a3297cd","Two years of Odin/OSIRIS measurements of the limb-scattered solar radiance are analyzed with respect to polar mesospheric clouds (PMCs) in both the southern hemisphere (SH) and the northern hemisphere (NH). Spatial and temporal distributions, tangent altitudes (TAs) and the brightness of PMCs during two SH summers of 2001/2002 and 2002/2003, and two NH summers of 2002 and 2003 are presented. The Odin/OSIRIS data clearly indicate inter-annual and inter-hemispheric differences in both PMC altitudes and brightness. Most of the SH clouds were detected between 70°S and 82°S, the lowest PMC latitude was 61.4°S in 2001/2002 and 54.7°S in 2002/2003, and only eight clouds were observed equatorward of 70°S in 2001/2002 compared to 33 clouds in 2002/2003. In 2002, NH clouds were observed later (by about 9 days), were in general less frequent and their maximum detection frequency was registered 2 weeks later than in 2003. The number of PMCs observed equatorward of 60°N in 2003 was almost twice as high as in 2002. The inter-annual variability of PMC properties in the NH was generally lower than in the SH. The PMC detection frequency in the SH was about 40% lower than in the NH. The inter-hemispheric difference in the mean PMC TA was between 1.1 and 2.3 km with NH clouds lower than SH clouds. The inter-hemispheric difference in the mean PMC brightness was about ∼35-40% with the NH clouds being brighter. © 2005 Elsevier Ltd. All rights reserved."
"7004239939;7004159070;7404577357;35481796400;","A quarter-century of satellite polar mesospheric cloud observations",2006,"10.1016/j.jastp.2005.08.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30344472126&doi=10.1016%2fj.jastp.2005.08.003&partnerID=40&md5=d8228fa17bc01a73edf1eb5f98fe852a","Satellite observations of polar mesospheric clouds (PMCs) are extremely valuable because they typically have daily coverage to characterize seasonal variations, sufficient detections for each season to give good statistics, quantitative information for physical analysis, and coverage of both hemispheres to evaluate global behavior. Continuous spectral measurements in the ultraviolet provide information about particle size distributions. A typical PMC season begins approximately 20 days before summer solstice at 80° latitude, rises rapidly in occurrence frequency to 80-90%, and remains at that level until 50-60 days after solstice. Both occurrence frequency and brightness are latitude dependent, with higher values observed toward the poles. PMCs are normally observed at altitudes of 82-83 km, with higher altitudes at the start and end of each season. Hemispheric differences in behavior are also observed. Northern Hemisphere PMCs are consistently both more frequent and brighter than Southern Hemisphere clouds. Cloud height is generally anti-correlated with cloud brightness. The availability of extended PMC data sets from satellites provides the opportunity to evaluate long-term PMC variations over the past few decades. Analysis of these lengthy data sets shows a clear anti-correlation between seasonally averaged PMC parameters (occurrence frequency and brightness) and solar UV activity over the past two solar cycles, in agreement with model predictions. A time lag of ∼1 year between the solar cycle and the PMC response is present in several data sets (solar variation leads PMC response). The cause is unknown. Multiple regression analysis also indicates long-term increases in both occurrence frequency and brightness, although there is not yet a consensus on the magnitude of the increase. These results are compared with information about concurrent variations in plausible source mechanisms such as mesospheric water vapor and temperature. © 2005 Elsevier Ltd. All rights reserved."
"7102953444;7402480218;57202413846;","Evaluation of clear-sky solar fluxes in GCMs participating in AMIP and IPCC-AR4 from a surface perspective",2006,"10.1029/2005JD006118","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33144487830&doi=10.1029%2f2005JD006118&partnerID=40&md5=d1698f4f081c152a1b0a2e80ada5e567","Solar fluxes at the Earth's surface calculated in General Circulation Models (GCMs) contain large uncertainties, not only in the presence of clouds but, as shown here, even under clear-sky (i.e., cloud-free) conditions. Adequate observations to constrain the uncertainties in these clear-sky fluxes have long been missing. The present study provides newly derived observational clear-sky climatologies at worldwide distributed anchor sites with high-accuracy measurements from the Baseline Surface Radiation Network (BSRN) and the Atmospheric Radiation Measurement Program (ARM). These data are used to systematically assess the performance of a total of 36 GCMs with respect to their surface solar clear-sky fluxes. These models represent almost 2 decades of model development, from the atmospheric model intercomparison projects AMIP I and AMIP II to the state of the art models participating in the 4th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC-AR4). Results show that earlier model versions tend to largely overestimate the surface insolation under cloud-free conditions. This identifies an overly transparent cloud-free atmosphere as a key error source for the excessive surface insolation in GCMs noted in previous studies. Possible origins are an underestimated water vapor absorption and a lack of adequate aerosol forcing. Similar biases remain in a number of current models with comparatively low atmospheric clear-sky solar absorption (around 60 Wm-2 in the global mean). However, there are now several models participating in IPCC-AR4 with higher atmospheric clear-sky absorption (70 Wm-2 and up, globally averaged) and more realistic aerosol treatment, which are in excellent agreement with the newly derived observational clear-sky climatologies. This underlines the progress made in radiative transfer modeling as well as in the observation and diagnosis of solar radiation under cloudless atmospheres and puts the most likely value of solar radiation absorbed in the cloud-free atmosphere slightly above 70 Wm-2. Copyright 2006 by the American Geophysical Union."
"7005495256;7103060756;7005890514;","Local and global climate feedbacks in models with differing climate sensitivities",2006,"10.1175/JCLI3613.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644699286&doi=10.1175%2fJCLI3613.1&partnerID=40&md5=37211d47e4a1401b4a6a0ef18605cd51","The climatic response to a 5% increase in solar constant is analyzed in three coupled global ocean-atmosphere general circulation models, the NCAR Climate System Model version 1 (CSM1), the Community Climate System Model version 2 (CCSM2), and the Canadian Centre for Climate Modelling and Analysis (CCCma) Coupled General Circulation Model version 3 (CGCM3). For this simple perturbation the quantitative values of the radiative climate forcing at the top of the atmosphere can be determined very accurately simply from a knowledge of the shortwave fluxes in the control run. The climate sensitivity and the geographical pattern of climate feedbacks, and of the shortwave, longwave, clear-sky, and cloud components in each model, are diagnosed as the climate evolves. After a period of adjustment of a few years, both the magnitude and pattern of the feedbacks become reasonably stable with time, implying that they may be accurately determined from relatively short integrations. The global -mean forcing at the top of the atmosphere due to the solar constant change is almost identical in the three models. The exact value of the forcing in each case is compared with that inferred by regressing annual-mean top-of-the-atmosphere radiative imbalance against mean surface temperature change. This regression approach yields a value close to the directly diagnosed forcing for the CCCma model, but a value only within about 25% of the directly diagnosed forcing for the two NCAR models. These results indicate that this regression approach may have some practical limitation in its application, at least for some models. The global climate sensitivities differ among the models by almost a factor of 2, and, despite an overall apparent similarity, the spatial patterns of the climate feedbacks are only modestly correlated among the three models. An exception is the clear-sky shortwave feedback, which agrees well in both magnitude and spatial pattern among the models. The biggest discrepancies are in the shortwave cloud feedback, particularly in the tropical and subtropical regions where it is strongly negative in the NCAR models but weakly positive in the CCCma model. Almost all of the difference in the global-mean total feedback (and climate sensitivity) among the models is attributable to the shortwave cloud feedback component. All three models exhibit a region of positive feedb ack in the equatorial Pacific, which is surrounded by broad areas of negative feedback. These positive feedback regions appear to be associated with a local maximum of the surface warming. However, the models differ in the zonal structure of this surface warming, which ranges from a mean El Niño-like warming in the eastern Pacific in the CCCma model to a far-western Pacific maximum of warming in the NCAR CCSM2 model. A separate simulation with the CCSM2 model, in which these tropical Pacific zonal gradients of surface warming are artificially suppressed, shows no region of positive radiative feedback in the tropical Pacific. However, the global-mean feedback is only modestly changed in this constrained run, suggesting that the processes that produce the positive feedback in the tropical Pacific region may not contribute importantly to global-mean feedback and climate sensitivity. © 2006 American Meteorological Society."
"57203012011;57215455233;","Two- and three-dimensional cloud-resolving model simulations of the mesoscale enhancement of surface heat fluxes by precipitating deep convection",2006,"10.1175/JCL3610.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548257857&doi=10.1175%2fJCL3610.1&partnerID=40&md5=9095b9abb2d9f9e8cf8b91cf25597234","Two-dimensional (2D) and three-dimensional (3D) cloud-resolving model (CRM) simulations are conducted to quantify the enhancement of surface sensible and latent heat fluxes by tropical precipitating cloud systems for 20 days (10-30 December 1992) during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). The mesoscale enhancement appears to be analogous across both 2D and 3D CRMs, with the enhancement for the sensible heat flux accounting for 17% of the total flux for each model and the enhancement for the latent heat flux representing 18% and 16% of the total flux for 2D and 3D CRMs, respectively. The convection-induced gustiness is mainly responsible for the enhancement observed in each model simulation. The parameterization schemes of the mesoscale enhancement by the gustiness in terms of convective updraft, downdraft, and precipitation, respectively, are examined using each version of the CRM. The scheme utilizing the precipitation was found to yield the most desirable estimations of the mean fluxes with the smallest rms error. The results together with previous findings from other studies suggest that the mesoscale enhancement of surface heat fluxes by the precipitating deep convection is a subgrid process apparent across various CRMs and is imperative to incorporate into general circulation models (GCMs) for improved climate simulation. © 2006 American Meteorological Society."
"35547807400;57203049177;","The climate sensitivity and its components diagnosed from earth radiation budget data",2006,"10.1175/JCLI3611.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846135845&doi=10.1175%2fJCLI3611.1&partnerID=40&md5=c94728a9f799dc0cd20c9119921a42ac","One of the major uncertainties in the ability to predict future climate change, and hence its impacts, is the lack of knowledge of the earth's climate sensitivity. Here, data are combined from the 1985-96 Earth Radiation Budget Experiment (ERBE) with surface temperature change information and estimates of radiative forcing to diagnose the climate sensitivity. Importantly, the estimate is completely independent of climate model results. A climate feedback parameter of 2.3 ± 1.4 W m -2 K -1 is found. This corresponds to a 1.0-4.1-K range for the equilibrium warming due to a doubling of carbon dioxide (assuming Gaussian errors in observable parameters, which is approximately equivalent to a uniform ""prior"" in feedback parameter). The uncertainty range is due to a combination of the short time period for the analysis as well as uncertainties in the surface temperature time series and radiative forcing time series, mostly the former. Radiative forcings may not all be fully accounted for; however, an argument is presented that the estimate of climate sensitivity is still likely to be representative of longer-term climate change. The methodology can be used to 1) retrieve shortwave and longwave components of climate feedback and 2) suggest clear-sky and cloud feedback terms. There is preliminary evidence of a neutral or even negative longwave feedback in the observations, suggesting that current climate models may not be representing some processes correctly if they give a net positive longwave feedback. © 2006 American Meteorological Society."
"57202891769;8900751100;7406671641;","A mechanism for abrupt climate change associated with tropical Pacific SSTs",2006,"10.1175/JCLI3608.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644677093&doi=10.1175%2fJCLI3608.1&partnerID=40&md5=49e502c484200326d8b6581a91461f8c","The tropical Pacific's response to transiently increasing atmospheric CO2 is investigated using three ensemble members from a numerically efficient, coupled atmosphere-ocean GCM. The model is forced with a 1% yr-1 increase in CO2 for 110 yr, when the concentration reaches 3 times the modern concentration. The transient greenhouse forcing causes a regionally enhanced warming of the equatorial Pacific, particularly in the far west. This accentuated equatorial heating, which is slow to arise but emerges abruptly during the last half of the simulations, results from both atmospheric and oceanic processes. The key atmospheric mechanism is a rapid local increase in the super-greenhouse effect, whose emergence coincides with enhanced convection and greater high cloud amount once the SST exceeds an apparent threshold around 27°C. The primary oceanic feedback is greater Ekman heat convergence near the equator, due to an anomalous near-equatorial westerly wind stress created by increased rising (sinking) air to the east (west) of Indonesia. The potential dependence of these results on the specific model used is discussed. The suddenness and far-ranging impact of the e nhanced, near-equatorial warming during these simulations suggests a mechanism by which abrupt climate changes may be triggered within the Tropics. The extratropical atmospheric response in the Pacific resembles anomalies during present-day El Niño events, while the timing and rapidity of the midlatitude changes are similar to those in the Tropics. In particular, a strengthening of the Pacific jet stream and a spinup of the wintertime Aleutian low seem to be forced by the changes in the tropical Pacific, much as they are in the modern climate. © 2006 American Meteorological Society."
"35509639400;57212781009;6603639908;7201443624;7004479957;7004714030;7403288995;23392612400;57205885015;7004169476;7202208382;7003543851;6603422104;7201485519;","How well do we understand climate change feedbacks?",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845363449&partnerID=40&md5=c6137fbebc2248665bd362e8cd2a457b","By reviewing recent observational, numerical, and theoretical studies, progress in understanding the physics of climate change feedbacks is achieved as well as some of the reasons for the intermodel differences. Intermodel differences in cloud feedbacks have been confirmed as the primary source of climate-sensitivity uncertainty, and recent studies suggest that these differences stem primarily from the response of low-level clouds. New methodologies of model-data comparison and of decomposition of the global cloud feedbacks into dynamical and thermodynamical components should help to determine which of the model cloud feedbacks seem more reliable."
"7004159166;57208121852;7003931528;56370934200;8666820400;","Aerosol activation and cloud processing in the global aerosol-climate model ECHAM5-HAM",2006,"10.5194/acp-6-2389-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745531945&doi=10.5194%2facp-6-2389-2006&partnerID=40&md5=6b458d2b27388fd748bad2051877dbd0","A parameterization for cloud processing is presented that calculates activation of aerosol particles to cloud drops, cloud drop size, and pH-dependent aqueous phase sulfur chemistry. The parameterization is implemented in the global aerosol-climate model ECHAM5-HAM. The cloud processing parameterization uses updraft speed, temperature, and aerosol size and chemical parameters simulated by ECHAM5-HAM to estimate the maximum supersaturation at the cloud base, and subsequently the cloud drop number concentration (CDNC) due to activation. In-cloud sulfate production occurs through oxidation of dissolved SO2 by ozone and hydrogen peroxide. The model simulates realistic distributions for annually averaged CDNC although it is underestimated especially in remote marine regions. On average, CDNC is dominated by cloud droplets growing on particles from the accumulation mode, with smaller contributions from the Aitken and coarse modes. The simulations indicate that in-cloud sulfate production is a potentially important source of accumulation mode sized cloud condensation nuclei, due to chemical growth of activated Aitken particles and to enhanced coalescence of processed particles. The strength of this source depends on the distribution of produced sulfate over the activated modes. This distribution is affected by uncertainties in many parameters that play a direct role in particle activation, such as the updraft velocity, the aerosol chemical composition and the organic solubility, and the simulated CDNC is found to be relatively sensitive to these uncertainties."
"7005321613;7004683817;7005648636;","Different response of clouds to solar input",2006,"10.1029/2006GL027820","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248557479&doi=10.1029%2f2006GL027820&partnerID=40&md5=663c84853bfca5187b31d9389b45a5bb","There is evidence that solar activity variations can affect the cloud cover at Earth. However, it is still unclear which solar driver plays the most important role in the cloud formation. Here we use partial correlations to distinguish between the effects of two solar drivers (cosmic rays and the UV irradiance) and the mutual relations between clouds at different altitudes. We find that the solar influence on cloud cover is not uniquely defined by one solar driver, but both seem to play a role depending on the climatic conditions and altitude. In particular, low clouds are mostly affected by UV irradiance over oceans and dry continental areas and by cosmic rays over some mid-high latitude oceanic areas and moist lands with high aerosol concentration. High clouds respond more strongly to cosmic ray variations, especially over oceans and moist continental areas. These results provide observational constraints on related climate models. Copyright 2006 by the American Geophysical Union."
"7004375028;","Long-term cosmic ray intensity variation and part of global climate change, controlled by solar activity through cosmic rays",2006,"10.1016/j.asr.2005.06.032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646835392&doi=10.1016%2fj.asr.2005.06.032&partnerID=40&md5=7bb5e3a5f85a6be33cf52c35327d962a","In this paper, we investigate properties long-term variations in galactic cosmic ray intensity as an important possible link in the connection between solar activity variation and global climate change. There are two main aims of the paper: (1) to estimate how solar activity influences on galactic CR long-term variations, what are the relative role in this influence of convection-diffusion modulation and drift modulation and (2) to estimate the expected part of global climate change which may be caused by the influence of solar activity cycle on climate through 11- and 22-year cosmic ray variations. © 2005."
"7102084129;35464731600;35887706900;","Switching cloud cover and dynamical regimes from open to closed Benard cells in response to the suppression of precipitation by aerosols",2006,"10.5194/acp-6-2503-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745576062&doi=10.5194%2facp-6-2503-2006&partnerID=40&md5=70c2d02d71799ab1668faaf637462408","The dynamic structure of the weakly sheared atmospheric marine boundary layer (MBL) supports three distinct states of cloud cover, which are associated with the concentrations of cloud condensation nuclei (CCN) aerosols in the MBL: (i) CCN rich MBL with closed Benard cellular convection that forms nearly full cloud cover; (ii) CCN depleted MBL with open cellular convection that forms <40% cloud cover; and, (iii) CCN starved MBL where clouds cannot form due to insufficient CCN, with near zero cloud cover. Here we propose a mechanism for the transition between these three states that involves the aerosol impacts on precipitation and the feedbacks on the dynamics of the clouds and on the aerosols deposition. By suppressing precipitation aerosols can reverse the direction of the airflow, converting the cloud structure from open to closed cells and more than doubling the cloud cover. The three states possess positive feedbacks for self maintenance, so that small changes of the conditions can lead to bifurcation of the MBL cloud regime. The transition between the closed and open cells occur at near pristine background level of aerosols, creating a large sensitivity of cloud radiative forcing to very small changes in aerosols at the MBL. The third state of super clean air can occur as the more efficient precipitation in cleaner air deposits the aerosols ever faster in a runaway positive feedback process. The proposed mechanism suggests that very small changes in the aerosols input to the MBL can have large impacts on the oceanic cloud cover and likely in turn on the global temperature, in ways that are not yet accounted for in the climate models."
"25227357000;7102018821;","Cirrus cloud horizontal and vertical inhomogeneity effects in a GCM",2006,"10.1007/s00703-004-0099-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31044450985&doi=10.1007%2fs00703-004-0099-2&partnerID=40&md5=8a731990be1c1ffe4fc1e96013d7b53b","A set of the inhomogeneity factor for high-level clouds derived from the ISCCP D1 dataset averaged over a five-year period has been incorporated in the UCLA atmospheric GCM to investigate the effect of cirrus cloud inhomogeneity on climate simulation. The inclusion of this inhomogeneous factor improves the global mean planetary albedo by about 4% simulated from the model. It also produces changes in solar fluxes and OLRs associated with changes in cloud fields, revealing that the cloud inhomogeneity not only affects cloud albedo directly, but also modifies cloud and radiation fields. The corresponding difference in the geographic distribution of precipitation is as large as 7 mm day-1. Using the climatology cloud inhomogeneity factor also produces a warmer troposphere related to changes in the cloudiness and the corresponding radiative heating, which, to some extent, corrects the cold bias in the UCLA AGCM. The region around 14 km, however, is cooler associated with increase in the reflected solar flux that leads to a warmer region above. An interactive parameterization for mean effective ice crystal size based on ice water content and temperature has also been developed and incorporated in the UCLA AGCM. The inclusion of the new parameterization produces substantial differences in the zonal mean temperature and the geographic distribution of precipitation, radiative fluxes, and cloud cover with respect to the control run. The vertical distribution of ice crystal size appears to be an important factor controlling the radiative heating rate and the consequence of circulation patterns, and hence must be included in the cloud-radiation parameterization in climate models to account for realistic cloud processes in the atmosphere. © Springer-Verlag/Wien 2006."
"16029830700;","Greenhouse effect of the atmosphere and its influence on Earth's climate (satellite data)",2006,"10.1007/s11110-006-0036-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847645890&doi=10.1007%2fs11110-006-0036-7&partnerID=40&md5=fe455ff004cfd5291c3a6efbdbe9e580","On the basis of the radiation-cloudiness model and the available long-term satellite data, we study the correlations of the greenhouse effect with the surface temperature of air and effective cloudiness equal to the product of the cloud amount by the conditional optical density of the clouds. We deduce the relations of satellite monitoring of the behavior of the anomalies of global air temperature caused by the excess amounts of volcanic products and greenhouse gases (formed as a result combustion of the fossil fuel) in the atmosphere. Realistic estimates of the processes of cooling and warming of the currently existing climate are obtained. Under the condition of preservation of the existing linear trends in the behaviors of the short-and long-wave flows of radiation into the outer space (observed according to satellite data for the last 20 yr), the global temperature in the second part of the current century can increase by 1.6-2.0°C. © Springer Science+Business Media, Inc. 2006."
"6701606453;7004899626;8600098200;8600097900;7202899330;","Objective assessment of the information content of visible and infrared radiance measurements for cloud microphysical property retrievals over the global oceans. Part I: Liquid clouds",2006,"10.1175/JAM2326.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646562854&doi=10.1175%2fJAM2326.1&partnerID=40&md5=6e206c67801eb36acf0b42fd8bcf5c1e","The importance of accurately representing the role of clouds in climate change studies has become increasingly apparent in recent years, leading to a substantial increase in the number of satellite sensors and associated algorithms that are devoted to measuring the global distribution of cloud properties. The physics governing the radiative transfer through clouds is well understood, but the impact of uncertainties in algorithm assumptions and the true information content of the measurements in the inverse retrieval problem are generally not as clear, making it difficult to determine the best product to adopt for any particular application. This paper applies information theory to objectively analyze the problem of liquid cloud retrievals from an observing system modeled after the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument currently operating on the Aqua and Terra platforms. It is found that four diagnostics - the retrieval error covariance, the information content, the number of degrees of freedom for signal, and the effective rank of the problem - provide a rigorous test of an observing system. Based on these diagnostics, the combination of the 0.64- and 1.64-μm channels during the daytime and the 3.75- and 11.0-μm channels at night provides the most information for retrieving the properties of the wide variety of liquid clouds modeled. With an eye toward developing a coherent representation of the global distribution of cloud microphysical and radiative properties, these four channels may be integrated into a suitable multichannel inversion methodology such as the optimal estimation or Bayesian techniques to provide a common framework for cloud retrievals under varying conditions. The expected resolution of the observing system for such liquid cloud microphysical property retrievals over a wide variety of liquid cloud is also explored. © 2006 American Meteorological Society."
"13403622000;7005955015;7003777747;8708955900;7003614389;","Combined observational and modeling based study of the aerosol indirect effect",2006,"10.5194/acp-6-3583-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748298912&doi=10.5194%2facp-6-3583-2006&partnerID=40&md5=faba03cdaed29f245f36bf78ce262219","The indirect effect of aerosols via liquid clouds is investigated by comparing aerosol and cloud characteristics from the Global Climate Model CAM-Oslo to those observed by the MODIS instrument onboard the TERRA and AQUA satellites (http://modis.gsfc.nasa.gov). The comparison is carried out for 15 selected regions ranging from remote and clean to densely populated and polluted. For each region, the regression coefficient and correlation coefficient for the following parameters are calculated: Aerosol Optical Depth vs. Liquid Cloud Optical Thickness, Aerosol Optical Depth vs. Liquid Cloud Droplet Effective Radius and Aerosol Optical Depth vs. Cloud Liquid Water Path. Modeled and observed correlation coefficients and regression coefficients are then compared for a 3-year period starting in January 2001. Additionally, global maps for a number of aerosol and cloud parameters crucial for the understanding of the aerosol indirect effect are compared for the same period of time. Significant differences are found between MODIS and CAM-Oslo both in the regional and global comparison. However, both the model and the observations show a positive correlation between Aerosol Optical Depth and Cloud Optical Depth in practically all regions and for all seasons, in agreement with the current understanding of aerosol-cloud interactions. The correlation between Aerosol Optical Depth and Liquid Cloud Droplet Effective Radius is variable both in the model and the observations. However, the model reports the expected negative correlation more often than the MODIS data. Aerosol Optical Depth is overall positively correlated to Cloud Liquid Water Path both in the model and the observations, with a few regional exceptions."
"7004683817;7005321613;7004272837;7005648636;","Correlation between clouds at different altitudes and solar activity: Fact or Artifact?",2006,"10.1016/j.jastp.2006.08.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751188924&doi=10.1016%2fj.jastp.2006.08.005&partnerID=40&md5=773c51c8a74c545325db2545222e89c8","Studies of the relation between cosmic rays (CR) (solar activity) and atmospheric cloudiness are mostly based on the satellite ISCCP cloud data. However, doubts have been cast that these relations can be an artifact of instrumental effects, i.e., of the masking/obscuring low clouds by higher clouds in the satellite view. If this is the case, most of the earlier results based on ISCCP data would be devaluated. Here, we reanalyze the ISCCP cloud coverage data and its relation with the cosmic ray-induced ionization, and show that the correlation between low clouds and CR is affected by higher clouds in some geographical regions, but not everywhere. In turn, our results show that low clouds also may affect the relation of higher clouds with CR in some regions. Accordingly, correlation analysis can be performed only when the strong relation between clouds of different types is taken into account. In particular, studies based on global or latitudinal (zonally averaged) cloud data should be revised. © 2006 Elsevier Ltd. All rights reserved."
"6603172418;7004864963;7005069415;7006837187;7005601996;7003591311;7006354036;14034301300;7006712143;57203053317;6602354484;7404062492;7006708207;7004838931;7006434689;","The effect of physical and chemical aerosol properties on warm cloud droplet activation",2006,"10.5194/acp-6-2593-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745790060&doi=10.5194%2facp-6-2593-2006&partnerID=40&md5=38a5520a0a58498e9646efee750d4d16","The effects of atmospheric aerosol on climate forcing may be very substantial but are quantified poorly at present; in particular, the effects of aerosols on cloud radiative properties, or the ""indirect effects"" are credited with the greatest range of uncertainty amongst the known causes of radiative forcing. This manuscript explores the effects that the composition and properties of atmospheric aerosol can have on the activation of droplets in warm clouds, so potentially influencing the magnitude of the indirect effect. The effects of size, composition, mixing state and various derived properties are assessed and a range of these properties provided by atmospheric measurements in a variety of locations is briefly reviewed. The suitability of a range of process-level descriptions to capture these aerosol effects is investigated by assessment of their sensitivities to uncertainties in aerosol properties and by their performance in closure studies. The treatment of these effects within global models is reviewed and suggestions for future investigations are made."
"56158622800;12239740000;7402162859;57204999963;","Temporal structures of the North Atlantic Oscillation and its impact on the regional climate variability",2006,"10.1007/s00376-006-0003-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-32144464897&doi=10.1007%2fs00376-006-0003-8&partnerID=40&md5=337ee3b0d0b6e8f3d1abe52c522f63e5","In this study, the temporal structure of the variation of North Atlantic Oscillation (NAO) and its impact on regional climate variability are analyzed using various datasets. The results show that blocking formations in the Atlantic region are sensitive to the phase of the NAO. Sixty-seven percent more winter blocking days are observed during the negative phase compared to the positive phase of the NAO. The average length of blocking during the negative phase is about 11 days, which is nearly twice as long as the 6-day length observed during the positive phase of the NAO. The NAO-related differences in blocking frequency and persistence are associated with changes in the distribution of the surface air temperature anomaly, which, to a large extent, is determined by the phase of the NAO. The distribution of regional cloud amount is also sensitive to the phase of the NAO. For the negative phase, the cloud amounts are significant, positive anomalies in the convective zone in the Tropics and much less cloudiness in the mid latitudes. But for the positive phase of the NAO, the cloud amount is much higher in the mid-latitude storm track region. In the Whole Atlantic region, the cloud amount shows a decrease with the increase of surface air temperature. These results suggest that there may be a negative feedback between the cloud amount and the surface air temperature in the Atlantic region."
"8600097900;6701606453;7004899626;7102591209;7202899330;","Objective assessment of the information content of visible and infrared radiance measurements for cloud microphysical property retrievals over the global oceans. Part II: Ice clouds",2006,"10.1175/JAM2327.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646571209&doi=10.1175%2fJAM2327.1&partnerID=40&md5=9870162460cad6a96203bd3cfffae0fd","Cirrus clouds play an important yet poorly determined role in the earth's climate system and its various feedback mechanisms. As such, a significant amount of work has been accomplished both in understanding the physics of the ice clouds and in using this knowledge to estimate global distributions of ice cloud properties from satellite-based instruments. This work seeks to build on these past efforts by offering a reexamination of the ice cloud retrieval problem in context of recent advancements in the understanding of optical properties for a variety of realistic ice crystal shapes. In this work, the formal information content analysis outlined in Part I is used to objectively select the optimal combination of measurements for an ice cloud microphysical property retrieval scheme given a realistic assessment of the uncertainties that govern the ice cloud retrieval problem. Although this analysis is for a theoretical retrieval combining simulated measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) with the CloudSat Cloud Profiling Radar (CPR) above an ocean surface, the general methodology is applicable to any instrument package. Channel selection via information content is determined through a realistic characterization of not only the sensitivity of top-of-the-atmosphere radiances to desired retrieval parameters but also to the uncertainties resulting from both the measurements themselves and from the forward model assumptions used in relating observational' and retrieval space. Results suggest that the channels that maximize retrieval information are strongly dependent upon the state of the atmosphere, meaning that no combination of two or three channels will always ensure an accurate retrieval. Because of the complexities of this state-dependent nature and the need for a consistent retrieval scheme for an operational retrieval, a five-channel retrieval approach consisting of a combination of error-weighted visible, near-infrared, and infrared channels is suggested. Such an approach ensures high information content regardless of cloud and atmospheric properties through use of the inherent sensitivities in each of these spectral regions. © 2006 American Meteorological Society."
"56219284300;26643251000;13402933200;6506606807;55893487700;57202531041;8724549600;7102578937;","Impact of ship emissions on the microphysical, optical and radiative properties of marine stratus: A case study",2006,"10.5194/acp-6-4925-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750526649&doi=10.5194%2facp-6-4925-2006&partnerID=40&md5=822cb1c28db7ff604c7ece8ed0998c34","Modifications of existing clouds by the exhaust of ships are well-known but inadequately quantified impacts, which could contribute to climate change. The perturbation of a cloud layer by ship-generated aerosol changes the cloud reflectivity and is identified by long curves in satellite images, known as ship tracks. As ship tracks indicate a pollution of a very clean marine environment and also affect the radiation budget below and above the cloud, it is important to investigate their radiative and climatic effects. Satellite-data from MODIS on Terra are used to examine a scene from 10 February 2003 where ship tracks were detected close to the North American West-Coast. The cloud optical and microphysical properties are derived using a semi-analytical retrieval technique combined with a look-up-table approach. An algorithm is presented to distinguish ship-track-pixels from the unperturbed cloud pixels in the scene and from this the optical properties of the former are compared to those of the latter. Within the ship tracks a significant change in the droplet number concentration, the effective radius and the optical thickness are found compared to the unaffected cloud. The resulting cloud properties are used to calculate the radiation budget below and above the cloud. Assuming a mean solar zenith angle of 63° for the selected scene, the mean solar surface radiation below the ship track is decreased by 43.2 Wm-2 and the mean reflectance at top of atmosphere (TOA) is increased by 40.8 Wm-2. For the entire analyzed scene the ship emission decreases the solar radiation at the surface by 2.1 Wm-2 and increases the backscattered solar radiation at TOA by 2.0 Wm-2, whereas no significant effect on thermal radiation was detected."
"7004559579;7003886299;","The effects of aerosols on precipitation and dimensions of subtropical clouds: A sensitivity study using a numerical cloud model",2006,"10.5194/acp-6-67-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33144462939&doi=10.5194%2facp-6-67-2006&partnerID=40&md5=79a5620946c2c4765c61774c65803d5c","Numerical experiments were carried out using the Tel-Aviv University 2-D cloud model to investigate the effects of increased concentrations of Cloud Condensation Nuclei (CCN), giant CCN (GCCN) and Ice Nuclei (IN) on the development of precipitation and cloud structure in mixedphase sub-tropical convective clouds. In order to differentiate between the contribution of the aerosols and the meteorology, all simulations were conducted with the same meteorological conditions. The results show tha t under the same meteorological conditions, polluted clouds (with high CCN concentrations) produce less precipitation than clean clouds (with low CCN concentrations), the initiation of precipitation is delayed and the lifetimes of the clouds are longer. GCCN enhance the total precipitation on the ground in polluted clouds but they have no noticeable effect on cleaner clouds. The increased rainfall due to GCCN is mainly a result of the increased graupel mass in the cloud, but it only partially offsets the decrease in rainfall due to pollution (increased CCN). The addition of more effective IN, such as mineral dust particles, reduces the total amount of precipitation on the ground. This reduction is more pronounced in clean clouds than in polluted ones. Polluted clouds reach higher altitudes and are wider than clean clouds and both produce wider clouds (anvils) when more IN are introduced. Since under the same vertical sounding the polluted clouds produce less rain, more water vapor is left aloft after the rain stops. In our simulations about 3.5 times more water evaporates after the rain stops from the polluted cloud as compared to the clean cloud. The implication is that much more water vapor is transported from lower levels to the mid troposphere under polluted conditions, something that should be considered in climate models. © 2006 Author(s). This work is licensed under a Creative Commons License."
"6701410329;36523706800;6507040878;","CM-SAF surface radiation budget: First results with AVHRR data",2006,"10.1016/j.asr.2005.10.044","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745617858&doi=10.1016%2fj.asr.2005.10.044&partnerID=40&md5=cc6de12eb1607fd5acb97ba4b86b88aa","In the phase of redefinition of the EUMETSAT ground segment seven so called Satellite Application Facilities (SAF) each of them serving dedicated user groups have been established in Europe. The SAF on climate monitoring (CM-SAF) will deliver a comprehensive set of climate variables, including from different cloud products, radiation budget at the top of the atmosphere, surface radiation budget and tropospheric humidity. A consistent dataset of cloud and radiation products in a high spatial resolution on a uniform grid is derived. The CM-SAF is a joint project of the German Meteorological Service, EUMETSAT and five other European Meteorological Services. It is dedicated to produce climate datasets using data from instruments onboard of METEOSAT Second Generation and polar orbiting satellites NOAA and METOP. After the development phase, the CM-SAF has started its initial operational phase in the end of 2003. In this context, the algorithms have been implemented at the processing centres and the processing of satellite data from the polar orbiting satellites of NOAA has commenced. This paper gives an overview of the first products of surface radiative fluxes and their validation with selected surface sites. © 2005 COSPAR."
"6602122304;6508335288;7006182491;15045276500;6701891391;","Scavenging of ultrafine particles by rainfall at a boreal site: Observations and model estimations",2006,"10.5194/acp-6-4739-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750284146&doi=10.5194%2facp-6-4739-2006&partnerID=40&md5=b83c11b101d5838e0630618889cc94c8","Values of the scavenging coefficient determined from observations of ultrafine particles (with diameters in the range 10-510nm) during rain events at a boreal forest site in Southern Finland between 1996 and 2001 were reported by Laakso et al. (2003a). The estimated range of the median values of the scavenging coefficient was [7×10-6-4×10-5] s-1, which is generally higher than model calculations based only on below-cloud processes (Brownian diffusion, interception, and typical phoretic and charge effects). In the present study, in order to interpret these observed data on scavenging coefficients from Laakso et al. (2003a), we use a model that includes below-cloud scavenging processes, mixing of ultrafine particles from the boundary layer (BL) into cloud, followed by cloud condensation nuclei activation and in-cloud removal by rainfall. The range of effective scavenging coefficient predicted by the new model, corresponding to wide ranges of values of its input parameters, are compared with observations. Results show that ultrafine particle removal by rain depends on aerosol size, rainfall intensity, mixing processes between BL and cloud elements, in-cloud scavenged fraction, in-cloud collection efficiency, and in-cloud coagulation with cloud droplets. The scavenging coefficients predicted by the new model are found to be significantly sensitive to the choice of representation of: (1) mixing processes; (2) raindrop size distribution; (3) phoretic effects in aerosol-raindrop collisions; and (4) cloud droplet activation. Implications for future studies of BL ultrafine particles scavenging are discussed."
"6603191095;13106003700;6603538344;","Impact of increased vertical resolution on simulation of tropical climate",2006,"10.1007/s00704-005-0174-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646205680&doi=10.1007%2fs00704-005-0174-8&partnerID=40&md5=c0456548a8b21eec25a221fd36d254a4","The aim of this study is to describe the behaviour of tropical dynamics in the ECHAM4 model when increased vertical resolution around the tropopause and in the planetary boundary layer is used. In this work we perform experiments with the ECHAM4 model using T30 horizontal resolution and 19 and 42 vertical levels. The impact of the increased vertical resolution on the simulation of tropical clouds and precipitation has been investigated. Therefore, the dynamic fields related to tropical convection have been analyzed. The results suggest a beneficial effect of the increased number of vertical levels on the convective scheme performance and on the related dynamic fields over the Tropics. The improvement of the rainfall climatologies in the 42-level model has been explained via the impact of vertical resolution on the cloud structure. In the cloud spectrum of the L42 simulation, a third peak appears around 600hPa, revealing that when using higher vertical resolution the convective parametrization starts to represent cumulus congestus clouds. © Springer-Verlag 2006."
"6701832491;6701915334;6602926744;7402504552;7202162685;12764954600;7003908632;12763461700;55637266800;8670472000;12764661900;7004279859;7102636922;23482558100;7003455444;55708356600;7003875148;6602178158;6701728368;","Evaluation of an ensemble of Arctic regional climate models: Spatiotemporal fields during the SHEBA year",2006,"10.1007/s00382-005-0095-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644696800&doi=10.1007%2fs00382-005-0095-3&partnerID=40&md5=bb868e32696f284ad752ae14845f5764","Simulations of eight different regional climate models (RCMs) have been performed for the period September 1997-September 1998, which coincides with the Surface Heat Budget of the Arctic Ocean (SHEBA) project period. Each of the models employed approximately the same domain covering the western Arctic, the same horizontal resolution of 50 km, and the same boundary forcing. The models differ in their vertical resolution as well as in the treatments of dynamics and physical parameterizations. Both the common features and differences of the simulated spatiotemporal patterns of geopotential, temperature, cloud cover, and long-/shortwave downward radiation between the individual model simulations are investigated. With this work, we quantify the scatter among the models and therefore the magnitude of disagreement and unreliability of current Arctic RCM simulations. Even with the relatively constrained experimental design we notice a considerable scatter among the different RCMs. We found the largest across-model scatter in the 2 m temperature over land, in the surface radiation fluxes, and in the cloud cover which implies a reduced confidence level for these variables. © Springer-Verlag 2006."
"7006735010;7005663552;36852686700;7201990763;6602940179;6504043100;7004787833;7202480306;6603299004;8445732300;8371200500;7004372835;7004762055;7006920633;","Interstellar-terrestrial relations: Variable cosmic environments, the dynamic heliosphere, and their imprints on terrestrial archives and climate",2006,"10.1007/s11214-006-9126-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947528528&doi=10.1007%2fs11214-006-9126-6&partnerID=40&md5=d1a1138d875a95e6787f1d1aa3bc076a","In recent years the variability of the cosmic ray flux has become one of the main issues interpreting cosmogenic elements and especially their connection with climate. In this review, an interdisciplinary team of scientists brings together our knowledge of the evolution and modulation of the cosmic ray flux from its origin in the Milky Way, during its propagation through the heliosphere, up to its interaction with the Earth's magnetosphere, resulting, finally, in the production of cosmogenic isotopes in the Earth' atmosphere. The interpretation of the cosmogenic isotopes and the cosmic ray - cloud connection are also intensively discussed. Finally, we discuss some open questions. © Springer Science+Business Media, Inc. 2007."
"13403704800;22959144500;7003488532;13403916800;57190000878;6603850285;6602354484;7003897194;","Cloud condensation nuclei properties of model and atmospheric HULIS",2006,"10.5194/acp-6-2465-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745532341&doi=10.5194%2facp-6-2465-2006&partnerID=40&md5=0e4296e774fd30fcfc4b645e86d15fb6","Humic like substances (HULIS) have been identified as a major fraction of the organic component of atmospheric aerosols. These large multifunctional compounds of both primary and secondary sources are surface active and water soluble. Hence, it is expected that they could affect activation of organic aerosols into cloud droplets. We have compared the activation of aerosols containing atmospheric HULIS extracted from fresh, aged and pollution particles to activation of size fractionated fulvic acid from an aquatic source (Suwannee River Fulvic Acid), and correlated it to the estimated molecular weight and measured surface tension. A correlation was found between CCN-activation diameter of SRFA fractions and number average molecular weight of the fraction. The lower molecular weight fractions activated at lower critical diameters, which is explained by the greater number of solute species in the droplet with decreasing molecular weight. The three aerosol-extracted HULIS samples activated at lower diameters than any of the size-fractionated or bulk SRFA. The Köhler model was found to account for activation diameters, provided that accurate physico-chemical parameters are known."
"6602600408;57203200427;57203053317;","Constraining the total aerosol indirect effect in the LMDZ and ECHAM4 GCMs using MODIS satellite data",2006,"10.5194/acp-6-947-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646492457&doi=10.5194%2facp-6-947-2006&partnerID=40&md5=8fdd8401657631637dbdff36b587d92b","Aerosol indirect effects are considered to be the most uncertain yet important anthropogenic forcing of climate change. The goal of the present study is to reduce this uncertainty by constraining two different general circulation models (LMDZ and ECHAM4) with satellite data. We build a statistical relationship between cloud droplet number concentration and the optical depth of the fine aerosol mode as a measure of the aerosol indirect effect using MODerate Resolution Imaging Spectroradiometer (MODIS) satellite data, and constrain the model parameterizations to match this relationship. We include here ""empirical"" formulations for the cloud albedo effect as well as parameterizations of the cloud lifetime effect. When fitting the model parameterizations to the satellite data, consistently in both models, the radiative forcing by the combined aerosol indirect effect is reduced considerably, down to -0.5 and -0.3 Wm-2, for LMDZ and ECHAM4, respectively. © Author(s) 2006. This work is licensed under a Creative Commons License."
"57193882808;7003554893;8977001000;7102425008;12800536400;6701346974;7401701196;9535769800;7003582587;7202772927;12800106700;57203012011;7403282069;","Daytime convective development over land: A model intercomparison based on LBA observations",2006,"10.1256/qj.04.147","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645501144&doi=10.1256%2fqj.04.147&partnerID=40&md5=8bc24dbcff3b86223f84671597e254ea","This paper investigates daytime convective development over land and its representation in single-column models (SCMs) and cloud-resolving models (CRMs). A model intercomparison case is developed based on observations of the diurnal cycle and convection during the rainy season in Amazonia. The focus is on the 6 h period between sunrise and early afternoon which was identified in previous studies as critical for the diurnal cycle over summertime continents in numerical weather prediction and climate models. This period is characterized by the formation and growth of a well-mixed convective boundary layer from the early morning temperature and moisture profiles as the surface sensible- and latent-heat fluxes increase after sunrise. It proceeds with the formation of shallow convective clouds as the convective boundary layer deepens, and leads to the eventual transition from shallow to deep precipitating convection around local noon. To provide a benchmark for other models, a custom-designed set of simulations, applying increasing in time computational domain and decreasing spatial resolution, was executed. The SCMs reproduced the previously identified problem with premature development of deep convection, less than two hours after sunrise. The benchmark simulations suggest a possible route to improve SCMs by considering a time-evolving cumulus entrainment rate as convection evolves from shallow to deep and the cloud width increases up to an order of magnitude. The CRMs featuring horizontal grid length around 500 m are capable of capturing the qualitative aspects of the benchmark simulations, but there are significant differences among the models. Two-dimensional CRMs tend to simulate too rapid a transition from shallow to deep convection and too high a cloud cover. © Royal Meteorological Society, 2006."
"6602806682;35592560600;","The initial dispersal and radiative forcing of a Northern Hemisphere mid-latitude super volcano: A model study",2006,"10.5194/acp-6-35-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33144479528&doi=10.5194%2facp-6-35-2006&partnerID=40&md5=7fbd7f8b652481a3b61d9f181f3b36df","The chemistry climate model MAECHAM4/CHEM with interactive and prognostic volcanic aerosol and ozone was used to study the initial dispersal and radiative forcing of a possible Northern Hemisphere mid-latitude super eruption. Tropospheric climate anomalies are not analysed since sea surface temperatures are kept fixed. Our experiments show that the global dispersal of a super eruption located at Yellowstone, Wy. is strongly dependent on the season of the eruption. In Northern Hemisphere summer the volcanic cloud is transported westward and preferentially southward, while in Northern Hemisphere winter the cloud is transported eastward and more northward compared to the summer case. Aerosol induced heating leads to a more global spreading with a pronounced cross equatorial transport. For a summer eruption aerosol is transported much further to the Southern Hemisphere than for a winter eruption. In contrast to Pinatubo case studies, strong cooling tendencies appear with maximum peak values of less than -1.6 K/day three months after the eruption in the upper tropical stratosphere. This strong cooling effect weakens with decreasing aerosol density over time and initially prevents the aerosol laden air from further active rising. All-sky net radiative flux changes of less than -32 W/m2 at the surface are about a factor of 6 larger than for the Pinatubo eruption. Large positive flux anomalies of more than 16 W/m2 are found in the first months in the tropics and sub tropics. These strong forcings call for a fully coupled ocean/atmosphere/chemistry model to study climate sensitivity to such a super-eruption. © 2006 Author(s). This work is licensed under a Creative Commons License."
"6602360081;6507871748;7003461830;35501613900;7005793702;7005399437;","Effect of smoke and clouds on the transmissivity of photosynthetically active radiation inside the canopy",2006,"10.5194/acp-6-1645-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746865613&doi=10.5194%2facp-6-1645-2006&partnerID=40&md5=15ed8dacfe4e15ed0afeb99490b73cb8","Biomass burning activities emit high concentrations of aerosol particles to the atmosphere. Such particles can interact with solar radiation, decreasing the amount of light reaching the surface and increasing the fraction of diffuse radiation through scattering processes, and thus has implications for photosynthesis within plant canopies. This work reports results from photosynthetically active radiation (PAR) and aerosol optical depth (AOD) measurements conducted simultaneously at Reserva Biológica do Jaru (Rondonia State, Brazil) during LBA/SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia/ Smoke, Aerosols, Clouds, Rainfall, and Climate) and RaCCI (Radiation, Cloud, and Climate Interactions in the Amazon during the Dry-to-Wet Transition Season) field experiments from 15 September to 15 November 2002. AOD values were retrieved from an AERONET (Aerosol Robotic Network) radiometer, MODIS (Moderate Resolution Spectroradiometer) and a portable sunphotometer from the United States Department of Agriculture - Forest Service. Significant reduction of PAR irradiance at the top of the canopy was observed due to the smoke aerosol particles layer. This radiation reduction affected turbulent fluxes of sensible and latent heats. The increase of AOD also enhanced the transmission of PAR inside the canopy. As a consequence, the availability of diffuse radiation was enhanced due to light scattering by the aerosol particles. A complex relationship was identified between light availability inside the canopy and net ecosystem exchange (NEE). The results showed that the increase of aerosol optical depth corresponded to an increase of CO2 uptake by the vegetation. However, for even higher AOD values, the corresponding NEE was lower than for intermediate values. As expected, water vapor pressure deficit (VPD), retrieved at 28 m height inside the canopy, can also affect photosynthesis. A decrease in NEE was observed as VPD increased. Further studies are needed to better understand these findings, which were reported for the first time for the Amazon region under smoky conditions."
"7004174939;35464731600;","Aerosol direct radiative effect at the top of the atmosphere over cloud free ocean derived from four years of MODIS data",2006,"10.5194/acp-6-237-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33144465935&doi=10.5194%2facp-6-237-2006&partnerID=40&md5=67d62ec2e10773ff75a65a5aa7e7e998","A four year record of MODIS spaceborne data provides a new measurement tool to assess the aerosol direct radiative effect at the top of the atmosphere. MODIS derives the aerosol optical thickness and microphysical properties from the scattered sunlight at 0.55-2.1 μm. The monthly MODIS data used here are accumulated measurements across a wide range of view and scattering angles and represent the aerosol's spectrally resolved angular properties. We use these data consistently to compute with estimated accuracy of ±0.6 Wm-2 the reflected sunlight by the aerosol over global oceans in cloud free conditions. The MODIS high spatial resolution (0.5 km) allows observation of the aerosol impact between clouds that can be missed by other sensors with larger footprints. We found that over the clearsky global ocean the aerosol reflected 5.3±0.6 Wm-2 with an average radiative efficiency of -49±2 Wm-2 per unit optical thickness. The seasonal and regional distribution of the aerosol radiative effects are discussed. The analysis adds a new measurement perspective to a climate change problem dominated so far by models. © 2006 Author(s). This work is licensed under a Creative Commons License."
"7201432984;57189585133;11440963500;7005809959;57203200427;7102294773;7403682442;6602244257;57208698992;7103206141;57213358341;26427744500;6701636053;14035836100;6603735912;7005088845;7006708207;7006634316;7102604282;7202429440;7101959920;7004898221;55207447000;7003359002;7404592426;7403384594;23493942300;","Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: Estimates based on in-situ chemical and optical measurements and chemical transport modeling",2006,"10.5194/acp-6-1657-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746890915&doi=10.5194%2facp-6-1657-2006&partnerID=40&md5=5c3ea6726fda86dcd83d54d727145262","The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar) radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001). Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regionsdownwind of major urban/population centers (North Indian Ocean (NIO) during INDOEX, the Northwest Pacific Ocean (NWP) during ACE-Asia, and the Northwest Atlantic Ocean (NWA) during ICARTT), incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART). Measurements of burdens, extinction optical depth (AOD), and direct radiative effect of aerosols (ORE - change in radiative flux due to total aerosols) are used as measurement-model check points to assess uncertainties. ln-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity) are used as input parameters to two radiative transfer models (GFDL and Universityof Michigan) to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative transfer calculations by observational inputs increases the clear-sky, 24-h averaged AOD (34×8%), top of atmosphere (TOA) DRE (32×12%), and TOA direct climate forcing of aerosols (DCF - change in radiative flux due to anthropogenic aerosols) (37×7%) relative to values obtained with ""a priori"" parameterizations of aerosol loadings and properties (GFDL RTM). The resulting constrained clear-sky TOA DCF is -3.3×0.47, -14×2.6, -6.4×2.1 Wm-2 for the NIO, NWP, and NWA, respectively. With the use of constrained quantities (extensive and intensive parameters) the calculated uncertainty in DCF was 25% less than the ""structural uncertainties"" used in the IPCC-2001 global estimates of direct aerosol climate forcing. Such comparisons with observations and resultant reductions in uncertainties are essential for improving and developing confidence in climate model calculations incorporating aerosol forcing."
"6701743200;55207447000;57198616562;55740664200;","Attribution of modeled atmospheric sulfate and SO2 in the Northern Hemisphere for June-July 1997",2006,"10.5194/acp-6-4723-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750362645&doi=10.5194%2facp-6-4723-2006&partnerID=40&md5=2effcadea8da41aaa98f823c607d2424","Anthropogenic sulfate aerosol is a major contributor to shortwave radiative forcing of climate change by direct light scattering and by perturbing cloud properties and to local concentrations of atmospheric particulate matter. Here we analyze results from previously published calculations with an Eulerian transport model for atmospheric sulfur species in the Northern Hemisphere in June-July, 1997 to quantify the absolute and relative contributions of specific source regions (North America, Europe, and Asia) and SO2-to-sulfate conversion mechanisms (gas-phase, aqueous-phase and primary sulfate) to sulfate and SO2 column burdens as a function of location and time. Although material emitted within a given region dominates the sulfate and SO2 column burden in that region, examination of time series at specific locations shows that material imported from outside can make a substantial and occasionally dominant contribution. Frequently the major fraction of these exogenous contributions to the sulfate column burden was present aloft, thus minimally impacting air quality at the surface, but contributing substantially to the burden and, by implication, to radiative forcing and diminution of surface irradiance. Although the dominant sulfate formation pathway in the domain as a whole is aqueous-phase reaction in clouds (62%), in regions with minimum opportunity for aqueous-phase reaction gas-phase oxidation is dominant, albeit with considerable temporal variability depending on meteorological conditions. These calculations highlight the importance of transoceanic transport of sulfate, especially at the western margins of continents under the influence of predominantly westerly transport winds."
"8693265000;14321355000;8921632800;6603860837;6701366594;","On the potential of sub-mm passive MW observations from geostationary satellites to retrieve heavy precipitation over the Mediterranean Area",2006,"10.5194/adgeo-7-387-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751576190&doi=10.5194%2fadgeo-7-387-2006&partnerID=40&md5=f765ca13fef95d1589a5b0cd8dcfc48a","The general interest in the potential use of the mm and sub-mm frequencies up to 425 GHz resolution from geostationary orbit is increasing due to the fact that the frequent time sampling and the comparable spatial resolution relative to the ""classical"" (≤89GHz) microwave frequencies would allow the monitoring of precipitating intense events for the assimilation of rain in now-casting weather prediction models. In this paper, we use the simulation of a heavy precipitating event in front of the coast of Crete island (Greece) performed by the University of Wisconsin - Non-hydrostatic Modeling System (UW-NMS) cloud resolving model in conjunction with a 3D-adjusted plane parallel radiative transfer model to simulate the upwelling brightness temperatures (TB's) at mm and sub-mm frequencies. To study the potential use of high frequencies, we first analyze the relationships of the simulated TB's with the microphysical properties of the UW-NMS simulated precipitating clouds, and then explore the capability of a Bayesian algorithm for the retrieval of surface rain rate, rain and ice water paths at such frequencies."
"57205638870;13404141800;56270311300;6701597468;22978151200;6603749963;7801647745;6701465132;7003851845;14060155500;7003927831;24347548900;56249704400;12139043600;55717074000;13404107300;7003777747;7102604282;7003800456;57206759288;12139310900;57208121852;7202079615;","Radiative forcing by aerosols as derived from the AeroCom present-day and pre-industrial simulations",2006,"10.5194/acp-6-5225-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746891396&doi=10.5194%2facp-6-5225-2006&partnerID=40&md5=b314a5ef984219d8f1ba25e27b887be9","Nine different global models with detailed aerosol modules have independently produced instantaneous direct radiative forcing due to anthropogenic aerosols. The anthropogenic impact is derived from the difference of two model simulations with prescribed aerosol emissions, one for present-day and one for pre-industrial conditions. The difference in the solar energy budget at the top of the atmosphere (ToA) yields a new harmonized estimate for the aerosol direct radiative forcing (RF) under all-sky conditions. On a global annual basis RF is -0.22 Wm-2, ranging from +0.04 to -0.41 Wm -2, with a standard deviation of ±0.16 Wm-2. Anthropogenic nitrate and dust are not included in this estimate. No model shows a significant positive all-sky RF. The corresponding clear-sky RF is -0.68 Wm-2. The cloud-sky RF was derived based on all-sky and clear-sky RF and modelled cloud cover. It was significantly different from zero and ranged between -0.16 and +0.34 Wm~2. A sensitivity analysis shows that the total aerosol RF is influenced by considerable diversity in simulated residence times, mass extinction coefficients and most importantly forcing efficiencies (forcing per unit optical depth). The clear-sky forcing efficiency (forcing per unit optical depth) has diversity comparable to that for the all-sky/ clear-sky forcing ratio. While the diversity in clear-sky forcing efficiency is impacted by factors such as aerosol absorption, size, and surface albedo, we can show that the all-sky/clear-sky forcing ratio is important because all-sky forcing estimates require proper representation of cloud fields and the correct relative altitude placement between absorbing aerosol and clouds. The analysis of the sulphate RF shows that long sulphate residence times are compensated by low mass extinction coefficients and vice versa. This is explained by more sulphate particle humidity growth and thus higher extinction in those models where short-lived sulphate is present at lower altitude and vice versa. Solar atmospheric forcing within the atmospheric column is estimated at +0.82±0.17 Wm-2. The local annual average maxima of atmospheric forcing exceed +5 Wm-2 confirming the regional character of aerosol impacts on climate. The annual average surface forcing is -1.02±0.23 Wm-2. With the current uncertainties in the modelling of the radiative forcing due to the direct aerosol effect we show here that an estimate from one model is not sufficient but a combination of several model estimates is necessary to provide a mean and to explore the uncertainty."
"14825561100;7004862771;","Validation of MODIS snow cover images over Austria",2006,"10.5194/hess-10-679-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749318365&doi=10.5194%2fhess-10-679-2006&partnerID=40&md5=8b4be6cb69a889dc2d73bb23e281e261","This study evaluates the Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover product over the territory of Austria. The aims are (a) to analyse the spatial and temporal variability of the MODIS snow product classes, (b) to examine the accuracy of the MODIS snow product against in situ snow depth data, and (c) to identify the main factors that may influence the MODIS classification accuracy. We use daily MODIS grid maps (version 4) and daily snow depth measurements at 754 climate stations in the period from February 2000 to December 2005. The results indicate that, on average, clouds obscured 63% of Austria, which may significantly restrict the applicability of the MODIS snow cover images to hydrological modelling. On cloud-free days, however, the classification accuracy is very good with an average of 95%. There is no consistent relationship between the classification errors and dominant land cover type and local topographical variability but there are clear seasonal patterns to the errors. In December and January the errors are around 15% while in summer they are less than 1%. This seasonal pattern is related to the overall percentage of snow cover in Austria, although in spring, when there is a well developed snow pack, errors tend to be smaller than they are in early winter for the same overall percent snow cover. Overestimation and underestimation errors balance during most of the year which indicates little bias. In November and December, however, there appears to exist a tendency for overestimation. Part of the errors may be related to the temporal shift between the in situ snow depth measurements (07:00 a.m.) and the MODIS acquisition time (early afternoon). The comparison of daily air temperature maps with MODIS snow cover images indicates that almost all MODIS overestimation errors are caused by the misclassification of cirrus clouds as snow."
"57212869747;14017658500;15062208600;7003533081;57194864794;6601974406;14018346900;15062614400;57203774435;6601972608;","Multipolarized radar for delineating within-field variability in corn and wheat",2006,"10.5589/m06-026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751017097&doi=10.5589%2fm06-026&partnerID=40&md5=1c636458b6ce84aaa6a278aba1451de8","In agriculture, there is growing interest in determining field spatial variability for implementing differential management practices, which should generate economic and environmental benefits. To date, the majority of studies involving remote sensing and differential management have focused on optical sensor systems. Less attention has been paid to synthetic aperture radar (SAR), despite the advantages of “all-weather” acquisition enabling information to be collected under cloud cover. This study examined the information content of multipolarization (HH, HV, VV, RR, LL, RL), multitemporal, and multiangle radar for delineating within-field spatial variability. On three dates in 2001, airborne C-band SAR data (35° and 55° incident angles) were acquired over four experimental fields. A series of fuzzy K-means analyses showed that the ability to differentiate zones was dependent upon the crop, the date in the growing season, and the pedodiversity of the field. Consistent with the soil and plant biophysical data, two of the four fields showed no spatial variability in radar backscatter. In the high-pedodiversity cornfield (Zea mays L.), three zones of productivity were discriminated early in the growing season and two zones of productivity in mid-season. Late in the season as a result of saturation of the radar signal, no spatial variability was evident. In corn, the results were similar regardless of the radar polarization. In the wheat (Triticum aestivum L.) field, which was of lower pedodiversity, two zones were identified in early-, mid-, and late-season images. Differences were evident among polarizations, with VV and HV being most sensitive to within-field variation. The delineated zones in both fields were shown to relate to plant and soil parameters, suggesting that radar may be a valuable tool in delineating spatial variation in producer fields and delineating differential management units. © 2006 Canadian Aeronautics and Space Institute."
"6602199581;8310425000;","Geographical and seasonal characteristics of the relationship between lightning ground flash density and rainfall within the continent of Australia",2006,"10.1016/j.atmosres.2005.03.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30044443155&doi=10.1016%2fj.atmosres.2005.03.004&partnerID=40&md5=499950e62ebad6d7ef4eb74a07b77242","Ground-based observations of annual rainfall and lightning incidence collected over periods ranging from 9 to 22 years at 23 stations around the continent of Australia were used to compute values of 'rain yield', defined as the mass of rain produced per lightning ground flash (units: kg fl-1) over a given area of ground. The rain yield was found to vary considerably with geographical location, season and climatic conditions. Of the 23 stations, 5 were mid-continental and these showed a mean rain yield of 2.64 × 108 kg fl-1 in contrast to the coastal and near-coastal stations that showed a corresponding mean value of 9.91 × 108 kg fl-1. The difference was statistically significant at the confidence level of 95%. When the stations were classified according to seasonal climate zones, the winter and winter-dominant rainfall stations showed a rain yield of 1.28 × 109 kg fl-1 while the summer and summer-dominant rainfall stations showed a significantly lower value of 5.44 × 108 kg fl-1. Again the difference was statistically significant at the 95% confidence level. Every one of the 23 stations showed mean winter rain yields that were significantly higher than the summer values. These differences are attributed to surface heating which controls such parameters as cloud base height and convective available potential energy in the atmosphere. In terms of the behaviour of the rain yield with geographical, seasonal and climatic conditions, the Australian observations are in good agreement with studies in other parts of the world. © 2005 Published by Elsevier B.V. All rights reserved."
"7005115667;6505884703;8683604700;56370460300;7005025749;7006131504;","Verification and application of a bio-optical algorithm for Lake Michigan using sea WiFS: A 7-year inter-annual analysis",2006,"10.3394/0380-1330(2006)32[258:VAAOAB]2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746179145&doi=10.3394%2f0380-1330%282006%2932%5b258%3aVAAOAB%5d2.0.CO%3b2&partnerID=40&md5=9f076fa44ae45189809746b450a93024","In this paper we utilize 7 years of SeaWiFS satellite data to obtain seasonal and inter-annual time histories of the major water color-producing agents (CPAs), phytoplankton chlorophyll (chl), dissolved organic carbon (doc), and suspended minerals (sm) for Lake Michigan. We first present validation of the Great Lakes specific algorithm followed by correlations of the CPAs with coincident environmental observations. Special attention is paid to the satellite observations of the extensive episodic event of sediment resuspension and calcium carbonate precipitation out of the water. We then compare the obtained time history of the CPA's spatial and temporal distributions throughout the lake to environmental observations such as air and water temperature, wind speed and direction, significant wave height, atmospheric precipitation, river runoff, and cloud and lake ice cover. Variability of the onset, duration, and spatial extent of both episodic events and seasonal phenomena are documented from the SeaWiFS time series data, and high correlations with relevant environmental driving factors are established. The relationships between the CPAs retrieved from satellite data and environmental observations are then used to speculate on the future of Lake Michigan under a set of climate change scenarios."
"13607461800;6603409139;7004142910;7202607188;7404062492;57203053317;14049331400;7003314595;56184892000;6701762451;6506539438;57192107995;7202586843;7102011023;","Oxalic acid as a heterogeneous ice nucleus in the upper troposphere and its indirect aerosol effect",2006,"10.5194/acp-6-3115-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746608879&doi=10.5194%2facp-6-3115-2006&partnerID=40&md5=8da8ce57813788a61a2caf41ebfb91f9","Heterogeneous ice freezing points of aqueous solutions containing various immersed solid dicarboxylic acids (oxalic, adipic, succinic, phthalic and fumaric) have been measured with a differential scanning calorimeter. The results show that only the dihydrate of oxalic acid (OAD) acts as a heterogeneous ice nucleus, with an increase in freezing temperature between 2 and 5 K depending on solution composition. In several field campaigns, oxalic acid enriched particles have been detected in the upper troposphere with single particle aerosol mass spectrometry. Simulations with a microphysical box model indicate that the presence of OAD may reduce the ice particle number density in cirrus clouds by up to ∼50% when compared to exclusively homogeneous cirrus formation without OAD. Using the ECHAM4 climate model we estimate the global net radiative effect caused by this heterogeneous freezing to result in a cooling as high as -0.3 Wm-2."
"6601927695;6701828494;14050912800;","The climate of Lago Maggiore area during the last fifty years [Il clima dell'areale del Lago Maggiore durante gli ultimi cinquant'anni]",2006,"10.4081/jlimnol.2006.s1.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746456374&doi=10.4081%2fjlimnol.2006.s1.1&partnerID=40&md5=299040a339ff94a5c400b54509d52082","Data collected in over 50 years' activity at the C.N.R meteorological station of Pallanza were analysed to see whether any changes have taken place in some climatic elements and to quantify the extent of such changes. A statistical analysis of the respective historical series was performed on nine meteorological parameters (solar radiation, insolation, air temperature, atmospheric pressure, humidity, cloud cover, precipitation, evaporation and wind), and on two other strictly limnological features: the level of Lago Maggiore and its water temperature at six different depths. In particular, we evaluated the means and the extremes (maxima and minima) on an annual, seasonal, monthly and daily level, with the results presented uniformly for all the parameters, also in graphic form. We especially highlighted the trend lines, even though they were not always statistically significant owing to the extreme variability of the meteorological data; in the absence of statistical validity, their significance is an approximate indication of their increasing or decreasing trend. Results showed that insolation, air temperature and atmospheric pressure had increased markedly over time, at least on an annual level, with the trends for solar radiation, humidity and cloud cover also showing an increase, though very slight. Evaporation and wind showed a steady, marked decrease, while precipitation and lake level were essentially stable. Water temperature showed a more varied picture, with the temperature of the topmost levels (to a depth of 10 m) continuing to increase."
"7202473760;","Sky view and weather controls on nocturnal surface moisture deposition on grass at urban sites",2006,"10.2747/0272-3646.27.1.70","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33747433802&doi=10.2747%2f0272-3646.27.1.70&partnerID=40&md5=f2c180912a4a99522519a1988e830d66","Water from dew has relevance to several topics in physical geography, including climatology, pollution deposition, and plant-water relations. There is growing scientific interest in urban dew, but urban dew data are rare. Weather is a primary control on dew wherever it forms but, especially in cities, site geometry can be important. In this paper sky view and weather controls on nocturnal surface moisture deposition are explored using data collected in Vancouver, British Columbia, Canada, during summer. For residential lawns and grassed parks in the city, similar spatial trends were evident in surface moisture amount measured at dawn by blotting and the sky view factor ψ. That is, more water accumulated where sky view was large, less under trees, and near buildings. Moisture accumulation at open sites was strongly controlled by weather conditions. Correlation was seen between moisture accumulation and wind and cloud conditions expressed as the semi-empirical ""weather factor,"" Φw. Results suggest ψ and Φw may together have potential to predict surface moisture accumulation, provided humidity is not limiting. Given the several important implications of surface moisture for urban physical systems, more studies of urban dew seem warranted. Copyright © 2006 by V. H. Winston &amp; Son, Inc. All rights reserved."
"15836242200;56343961900;","Spectral radiance and sky luminance in Antarctica: A case study",2006,"10.1007/s00704-005-0188-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745823078&doi=10.1007%2fs00704-005-0188-2&partnerID=40&md5=6add8f876c9312fe4890270223b07829","Sky luminance and spectral radiance has been characterised at Neumayer, Antarctica for selected situations during the austral summer 2003/04. Luminance has also been measured at Boulder, Colorado, USA in June 2003. The high reflectivity of the surface (albedo) in Antarctica, reaching values up to 100% in the ultraviolet (UV) and visible part of the solar spectrum due to snow cover, modifies the radiation field considerably when compared to mid-latitudes. A dependence of luminance and spectral radiance on solar zenith angle (SZA) and surface albedo has been identified. For snow and cloudless sky, the horizon luminance exceeds the zenith luminance by as much as a factor of 8.2 and 7.6 for a SZA of 86° and 48°, respectively. In contrast, over grass this factor amounts to 4.9 for a SZA of 86° and a factor of only 1.4 for a SZA of 48°. Thus, a snow surface with high albedo can enhance horizon brightening compared to grass by a factor of 1.7 for low sun at a SZA of 86° and by a factor of 5 for high sun at a SZA of 48°. For cloudy cases, zenith luminance and radiance exceed the cloudless value by a factor of 10 due to multiple scattering between the cloud base and high albedo surface. Measurements of spectral radiance show increased horizon brightening for increasing wavelengths and generally confirm the findings for luminance. Good agreement with model results is found for some cases; however there are also large deviations between measured and modelled values especially in the infrared. These deviations can only partly be explained by measurement uncertainties; to completely resolve the differences between model and measurement further studies need to be performed, which will require an improvement of modelling the spectral radiance. From the present study it can be concluded that a change in albedo conditions, which is predicted as a consequence of climate change, will significantly change the radiation conditions in polar regions as well. © Springer-Verlag 2006."
"6603258995;6701700126;","Application of nearest-neighbor resampling for homogenizing temperature records on a daily to sub-daily level",2006,"10.1002/joc.1236","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31944437373&doi=10.1002%2fjoc.1236&partnerID=40&md5=5eaada2e38e05e11de5ac38a579998ee","Nearest-neighbor resampling is introduced as a means for homogenizing temperature records on a daily to sub-daily level. Homogenization refers here to the problem of calculating daily mean and sub-daily temperatures from a time series subject to irregular observation frequencies and changing observation schedules. The method resamples diurnal temperature cycles from an observed hourly temperature subrecord at the station. Unlike other methods, the technique maintains the variance in a natural way. This property is especially important for the analysis of trends and variability of extremes. For a given day, the resampling technique does not generate a single-valued solution but this peculiarity is of no effect in the applications considered here. The skills of the nearest-neighbor resampling technique, in terms of bias, RMSE, and variability, are compared with those of four other methods: a sine-exponential model, a model that uses the climatological mean daily cycle, a regression model for calculating daily values, and a deterministic version of the nearest-neighbor technique. The series used in the tests is the 1951-2000 meteorological record of De Bilt (The Netherlands). The emphasis in the comparisons is on the reconstruction of daily mean temperatures. The analysis shows important differences in performance between the models. The regression-based method performs best with respect to the calculation of the individual daily mean temperatures; the day-to-day variability is best reproduced with the nearest-neighbor resampling technique. The performance of the models improves when cloudiness is used as an extra predictor. The improvement is, however, small compared to the intermodel differences. The type of model that should be used depends on the desired application. For trend and variability studies, the nearest-neighbor resampling technique performs best. Nearest-neighbor resampling can successfully be performed even in situations where the length of the hourly subrecord is an order of magnitude less than the length of the series to be homogenized. Copyright © 2005 Royal Meteorological Society."
"6507189548;57213381883;13403510100;6603729297;7007039218;7006708207;7006712143;","The composition of nucleation and Aitken modes particles during coastal nucleation events: Evidence for marine secondary organic contribution",2006,"10.5194/acp-6-4601-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749987963&doi=10.5194%2facp-6-4601-2006&partnerID=40&md5=a0cca850dd4a8d2999225984c530073e","Newly-formed nanometer-sized particles have been observed at coastal and marine environments world wide. Organic species have so far not been detected in those newly-formed nucleation mode particles. In this study, we applied the ultrafine organic tandem differential mobility analyzer method to study the possible existence of an organic fraction in recently formed coastal nucleation mode particles (d <20nm) at the Mace Head research station. Furthermore, effects of those nucleation events on potential cloud condensation nuclei were studied. The coastal events were typical for the Mace Head region and they occurred at low tide conditions during efficient solar radiation and enhanced biological activity in spring 2002. Additionally, a pulse height analyzer ultrafine condensation particle counter technique was used to study the composition of newly-formed particles formed in low tide conditions during a lower biological activity in October 2002. The overall results of the ultrafine organic tandem differential mobility analyzer and the pulse height analyzer ultrafine condensation particle counter measurements indicate that those coastally/marinely formed nucleation mode particles include a remarkable fraction of secondary organic products, beside iodine oxides, which are likely to be responsible for the nucleation. During clean marine air mass conditions, the origin of those secondary organic oxidation compounds can be related to marine coast and open ocean biota and thus a major fraction of the organics may originate from biosynthetic production of alkenes such as isoprene and their oxidation driven by iodine radi cals, hydroxyl radicals, acid catalysis, and ozone during efficient solar radiation. During modified marine conditions, also anthropogenic secondary organic compounds may contribute to the nucleation mode organic mass, in addition to biogenic secondary organic compounds. Thus, the ultrafine organic tandem differential mobility analyzer results suggest that the secondary organic compounds may, in addition to being significant contributors to the nucleation mode processes, accelerate the growth of freshly nucleated particles and increase their survival probability to cloud condensation nuclei and even larger radiatively active particle sizes. The results give new insights to the marine/coastal particle formation, growth, and properties. The marine biota driven secondary organic contributions to marine/coastal particle formation and composition can be anticipated in other species specific biologically active oceans and fresh-waters areas around the world and thus, they may be significant also to the global radiative bugdet, atmosphere-biosphere feedbacks, and climate change."
"7102692123;56501802200;7007148434;7101830914;8931293800;7401891176;7004864963;35461763400;","Optical properties of humic-like substances (HULIS) in biomass-burning aerosols",2006,"10.5194/acp-6-3563-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748292801&doi=10.5194%2facp-6-3563-2006&partnerID=40&md5=bc9be2a13c5ef76eda4a7572cfd7b84a","We present here the optical properties of humic-like substances (HULIS) isolated from the fine fraction of biomass-burning aerosol collected in the Amazon basin during the LBA-SMOCC (Large scale Biosphere atmosphere experiment in Amazonia - SMOke aerosols, Clouds, rainfall and Climate) experiment in September 2002. From the isolated HULIS, aerosol particles were generated and their scattering and absorption coefficients measured. The size distribution and mass of the particles were also recorded. The value of the index of refraction was derived from ""closure"" calculations based on particle size, scattering and absorption measurements. On average, the complex index of refraction at 532 nm of HULIS collected during day and nighttime was 1.65-0.0019i and 1.69-0.0016i, respectively. In addition, the imaginary part of the complex index of refraction was calculated using the measured absorption coefficient of the bulk HULIS. The mass absorption coefficient of the HULIS at 532 nm was found to be quite low (0.031 and 0.029 m2 g-1 for the day and night samples, respectively). However, due to the high absorption Angstrom exponent (6-7) of HULIS, the specific absorption increases substantially towards shorter wavelengths (∼2-3 m2 g -1 at 300 nm), causing a relatively high (up to 50%) contribution to the light absorption of our Amazonian aerosol at 300 nm. For the relative contribution of HULIS to light absorption in the entire solar spectrum, lower values (6.4-8.6%) are obtained, but those are still not negligible."
"11340215800;8631019200;7402727711;8364396600;56349223500;","A study on the aerosol extinction-to-backscatter ratio with combination of micro-pulse LIDAR and MODIS over Hong Kong",2006,"10.5194/acp-6-3243-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746889743&doi=10.5194%2facp-6-3243-2006&partnerID=40&md5=1261e2d8b70cdbdb0095e8cef723e3e4","The aerosol extinction-to-backscatter ratio is an important parameter for inverting LIDAR signals in the LI-DAR equation. It is a complicated function of the aerosol microphysical characteristics. In this paper, a method to retrieve the column-averaged aerosol extinction-to-backscatter ratio by constraining the aerosol optical depths (AOD) from a Micro-pulse LIDAR (MPL) by the AOD measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) is presented. Both measurements were taken on cloud free days between 1 May 2003 and 30 June 2004 over Hong Kong, a coastal city in south China. Simultaneous measurements of aerosol scattering coefficients with a forward scattering visibility sensor are compared with the LI-DAR retrieval of aerosol extinction coefficients. The data are then analyzed to determine seasonal trends of the aetrosol extinction-to-backscatter ratio. In addition, the relationships between the extinction-to-backscatter ratio and wind conditions as well as other aerosol microphysical parameters are presented. The mean aerosol extinction-to-backscatter ratio for the whole period was found to be 29.1 ± 5.8 sr, with a minimum of 18 sr in July 2003 and a maximum of 44 sr in March 2004. The ratio is lower in summer because of the dominance of oceanic aerosols in association with the prevailing southwesterly monsoon. In contrast, relatively larger ratios are noted in spring and winter because of the increased impact of local and regional industrial pollutants associated with the northerly monsoon. The extended LIDAR measurements over Hong Kong provide not only a more accurate retrieval of aerosol extinction coefficient profiles, but also significant substantial information for air pollution and climate studies in the region."
"6603463229;6506965345;55409869300;","Proxy-based reconstruction of erythemal UV doses over Estonia for 1955-2004",2006,"10.5194/angeo-24-1767-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751072920&doi=10.5194%2fangeo-24-1767-2006&partnerID=40&md5=fc24141469ab7d0414b50bec1ed9aeb9","A proxy-based reconstruction of the erythemally-weighted UV doses for 1955-2004 has been performed for the Tartu-T&#245;ravere Meteorological Station (58°16' N, 26°28' E, 70 m a.s.l.) site. The pyrheliometer- measured daily sum of direct irradiance on partly cloudy and clear days, and the pyranometer-measured daily sum of global irradiance on overcast days were used as the cloudiness influence related proxies. The TOMS ozone data have been used for detecting the daily deviations from the climatic value (averaged annual cycle). In 1998-2004, the biases between the measured and reconstructed daily doses in 55.5% of the cases were within ±10% and in 83.5% of the cases within ±20%, on average. In the summer half-year these amounts were 62% and 88%, respectively. In most years the results for longer intervals did not differ significantly, if no correction was made for the daily deviations of total ozone from its climatic value. The annual and summer half-yearly erythemal doses (contributing, on average, 89% of the annual value) agreed within ±2%, except for the years after major volcanic eruptions and one extremely fine weather year (2002). Using the daily relative sunshine duration as a proxy without detailed correction for atmospheric turbidity results in biases of 2-4% in the summer half-yearly dose in the years after major volcanic eruptions and a few other years of high atmospheric turbidity. The year-to-year variations of the summer half-yearly erythemal dose in 1955-2004 were found to be within 92-111% relative to their average value. Exclusion of eight extreme years reduces this range for the remaining to 95-105.5%. Due to the quasi-periodic alternation of wet and dry periods, the interval of cloudy summers 1976-1993 regularly manifests summer half-yearly erythemal dose values lower than the 1955-2004 average. Since 1996/1997 midwinters have been darker than on average."
"7006643234;7007148434;7004864963;8931293800;7401891176;7102830450;6602765265;8786620100;35461763400;","Optical and physical properties of aerosols in the boundary layer and free troposphere over the Amazon Basin during the biomass burning season",2006,"10.5194/acp-6-2911-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746237496&doi=10.5194%2facp-6-2911-2006&partnerID=40&md5=3a57a76fab49ee4ef4027d3ca4c1b8cc","As part of the Large Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke, Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) campaign, detailed surface and airborne aerosol measurements were performed over the Amazon Basin during the dry to wet season from 16 September to 14 November 2002. Optical and physical properties of aerosols at the surface, and in the boundary layer (BL) and free troposphere (FT) during the dry season are discussed in this article. Carbon monoxide (CO) is used as a tracer for biomass burning emissions. At the surface, good correlation among the light scattering coefficient (σs at 545 nm), PM2.5, and CO indicates that biomass burning is the main source of aerosols. Accumulation of haze during some of the large-scale biomass burning events led to high PM2.5 (225 μgm-3), σs, (1435 Mm-1), aerosol optical depth at 500 nm (3.0), and CO (3000ppb). A few rainy episodes reduced the PM2.5, number concentration (CN) and CO concentration by two orders of magnitude. The correlation analysis between σs and aerosol optical thickness shows that most of the optically active aerosols are confined to a layer with a scale height of 1617m during the burning season. This is confirmed by aircraft profiles. The average mass scattering and absorption efficiencies (545 nm) for small particles (diameter Dp &lt; 1.5 μm) at surface level are found to be 5.0 and 0.33 m2 g-1, respectively, when relating the aerosol optical properties to PM2.5 aerosols. The observed mean single scattering albedo (ω&gt;0 at 545 nm) for submicron aerosols at the surface is 0.92±0.02. The light scattering by particles (Δσs/ΔCN) increase 2-10 times from the surface to the FT, most probably due to the combined affects of coagulation and condensation."
"8558549500;6505784661;7006051077;57210521266;7006497723;6701618694;7004289682;13008018200;36124109400;","The STARTWAVE atmospheric water database",2006,"10.5194/acp-6-2039-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745552507&doi=10.5194%2facp-6-2039-2006&partnerID=40&md5=6bf98435116f57e6393c8544b887d362","The STARTWAVE (STudies in Atmospheric Radiative Transfer and Water Vapour Effects) project aims to investigate the role which water vapour plays in the climate system, and in particular its interaction with radiation. Within this framework, an ongoing water vapour database project was set up which comprises integrated water vapour (IWV) measurements made over the last ten years by ground-based microwave radiometers, Global Positioning System (GPS) receivers and sun photometers located throughout Switzerland at altitudes between 330 and 3584 m. At Bern (46.95° N, 7.44° E) tropospheric and stratospheric water vapour profiles are obtained on a regular basis and integrated liquid water, which is important for cloud characterisation, is also measured. Additional stratospheric water vapour profiles are obtained by an airborne microwave radiometer which observes large parts of the northern hemisphere during yearly flight campaigns. The database allows us to validate the various water vapour measurement techniques. Comparisons between IWV measured by the Payerne radiosonde with that measured at Bern by two microwave radiometers, GPS and sun photometer showed instrument biases within ±0.5 mm. The bias in GPS relative to sun photometer over the 2001 to 2004 period was -0.8mm at Payerne (46.81° N, 6.94° E, 490m), which lies in the Swiss plains north of the Alps, and +0.6 mm at Davos (46.81° N, 9.84° E, 1598m), which is located within the Alps in the eastern part of Switzerland. At Locarno (46.18° N, 8.78° E, 366 m), which is located on the south side of the Alps, the bias is +1.9 mm. The sun photometer at Locarno was found to have a bias of -2.2mm (13% of the mean annual IWV) relative to the data from the closest radiosonde station at Milano. This result led to a yearly rotation of the sun photometer instruments between low and high altitude stations to improve the calibrations. In order to demonstrate the capabilites of the database for studying water vapour variations, we investigated a front which crossed Switzerland between 18 November 2004 and 19 November 2004. During the frontal passage, the GPS and microwave radiometers at Bern and Payerne showed an increase in IWV of between 7 and 9 mm. The GPS IWV measurements were corrected to a standard height of 500 m, using an empirically derived exponential relationship between IWV and altitude. A qualitative comparison was made between plots of the IWV distribution measured by the GPS and the 6.2μm water vapour channel on the Meteosat Second Generation (MSG) satellite. Both showed that the moist air moved in from a northerly direction, although the MSG showed an increase in water vapour several hours before increases in IWV were detected by GPS or microwave radiometer. This is probably due to the fact that the satellite instrument is sensitive to an atmospheric layer at around 320 hPa, which makes a contribution of one percent or less to the IWV."
"57214957751;11141872500;7005287667;7005206400;7405551904;7004864963;35461763400;","Size distribution and hygroscopic properties of aerosol particles from dry-season biomass burning in Amazonia",2006,"10.5194/acp-6-471-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645638445&doi=10.5194%2facp-6-471-2006&partnerID=40&md5=1440218035fb350c0c2332bf32c6ce32","Aerosol particle number size distributions and hygroscopic properties were measured at a pasture site in the southwestern Amazon region (Rondonia). The measurements were performed 11 September-14 November 2002 as part of LBA-SMOCC (Large scale Biosphere atmosphere experiment in Amazonia - SMOke aerosols, Clouds, rainfall and Climate), and cover the later part of the dry season (with heavy biomass burning), a transition period, and the onset of the wet period. Particle number size distributions were measured with a DMPS (Differential Mobility Particle Sizer, 3-850nm) and an APS (Aerodynamic Particle Sizer), extending the distributions up to 3.3 μm in diameter. An H-TDMA (Hygroscopic Tandem Differential Mobility Analyzer) measured the hygroscopic diameter growth factors (Gf) at 90% relative humidity (RH), for particles with dry diameters (dp) between 20-440 nm, and at several occasions RH scans (30-90% RH) were performed for 165 nm particles. These data provide the most extensive characterization of Amazonian biomass burning aerosol, with respect to particle number size distributions and hygroscopic properties, presented until now. The evolution of the convective boundary layer over the course of the day causes a distinct diel variation in the aerosol physical properties, which was used to get information about the properties of the aerosol at higher altitudes. The number size distributions averaged over the three defined time periods showed three modes; a nucleation mode with geometrical median diameters (GMD) of ∼12 nm, an Aitken mode (GMD=61-92 nm) and an accumulation mode (GMD=128-190 nm). The two larger modes were shifted towards larger GMD with increasing influence from biomass burning. The hygroscopic growth at 90% RH revealed a somewhat external mixture with two groups of particles; here denoted nearly hydrophobic (Gf ∼1.09 for 100 nm particles) and moderately hygroscopic (Gf ∼1.26). While the hygroscopic growth factors were surprisingly similar over the periods, the number fraction of particles belonging to each hygroscopic group varied more, with the dry period aerosol being more dominated by nearly hydrophobic particles. As a result the total particle water uptake rose going into the cleaner period. The fraction of moderately hygroscopic particles was consistently larger for particles in the accumulation mode compared to the Aitken mode for all periods. Scanning the H-TDMA over RH (30-90% RH) showed no deliquescence behavior. A parameterization of both Gf(RH) and Gf(dp), is given. © 2006 Author(s). This work is licensed under a Creative Commons License."
"7102080550;35450467000;","A high-resolution modeling study of the 24 May 2002 dryline case during IHOP. Part II: Horizontal convective rolls and convective initiation",2006,"10.1175/MWR3072.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644761111&doi=10.1175%2fMWR3072.1&partnerID=40&md5=556b907e3ae0a2ba78a743df49d57a6f","In Part I of this paper, the timing and location of convective initiation along a dryline on 24 May 2002 were accurately predicted, using a large 1-km-resolution nested grid. A detailed analysis of the convective initiation processes, which involve the interaction of the dryline with horizontal convective rolls, is presented here. Horizontal convective rolls (HCRs) with aspect ratios (the ratio of roll spacing to depth) between 3 and 7 develop in the model on both sides of the dryline, with those on the west side being more intense and their updrafts reaching several meters per second. The main HCRs that interact with the primary dryline convergence boundary (PDCB) are those from the west side, and they are aligned at an acute angle with the dryline. They intercept the PDCB and create strong moisture convergence bands at the surface and force the PDCB into a wavy pattern. The downdrafts of HCRs and the associated surface divergence play an important role in creating localized maxima of surface convergence that trigger convection. The downward transport of westerly, southwesterly, or northwesterly momentum by the HCR downdrafts creates asymmetric surface divergence patterns that modulate the exact location of maximum convergence. Most of the HCRs have a partially cellular structure at their mature stage. The surface divergence flows help concentrate the background vertical vorticity and the vorticity created by tilting of environmental horizontal vorticity into vortex centers or misocyclones, and such concentration is often further helped by cross-boundary shear instability. The misocyclones, however, do not in general collocate with the maximum updrafts and, therefore, the points of convective initiation, but can help enhance surface convergence to their south and north. Sequences of convective cells develop at the locations of persistent maximum surface convergence, then move away from the source with the midlevel winds. When the initial clouds propagate along the convergence bands that trigger them, they grow faster and become more intense. While the mesoscale convergence of dryline circulation preconditions the boundary layer by deepening the mixed layer and lifting moist air parcels to their LCL, it is the localized forcing by the HCR circulation that determines the exact locations of convective initiation. A conceptual model summarizing the findings is proposed. © 2006 American Meteorological Society."
"8333761100;6701689811;7102021223;","Dust aerosols over India and adjacent continents retrieved using METEOSAT infrared radiance Part I: Sources and regional distribution",2006,"10.5194/angeo-24-37-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751095626&doi=10.5194%2fangeo-24-37-2006&partnerID=40&md5=0f42ac4714cfbe69537b4f28c19b1f71","Mineral dust constitutes the single largest contributor to continental aerosols. To accurately assess the impact of dust aerosols on climate, the spatial and temporal distribution of dust radiative properties is essential. Regional characteristics of dust radiative properties, however, are poorly understood. The magnitude and even sign of dust radiative forcing is uncertain, as it depends on a number of parameters, such as vertical distribution of dust, cloud cover and albedo of the underlying surface. In this paper, infrared radiance (10.5-12.5 &micro;m), acquired from the METEOSAT-5 satellite ( resolution), was used to retrieve regional characteristics of dust aerosols for all of 1999. The infrared radiance depression, due to the presence of dust in the atmosphere, has been used as an index of dust load, known as the Infrared Difference Dust Index (IDDI). There have been several studies in the past carried out over the Sahara using IDDI as a measure of dust load. Over the Indian region, however, studies on dust aerosols are sparse. Spatial and temporal variability in dust loading and its regional distribution over various arid and semiarid regions of India and adjacent continents (0-35° N; 30° E-100° E) (excluding Sahara) have been studied and the results are examined along with surface soil conditions (such as vegetation cover and soil moisture). The advantage of the IDDI method is that information on aerosol properties, such as chemical composition or microphysical properties, is not needed. A large day-to-day variation in IDDI was observed over the entire study region, with values ranging from 4 to 22 K. It was observed that dust activity starts by March over the Indian deserts, as well as over deserts of the Africa and Arabian regions. The IDDI reaches maximum during the period of May to August. Regional maps of IDDI, in conjunction with biomass burning episodes (using TERRA satellite fire pixel counts), suggest that large IDDI values observed during the winter months over Northern India could be due to a possible deposition of black carbon on larger dust aerosols. The IDDI values have been compared with another year (i.e. 2003), with a large number of dust storms reported by meteorological departments based on visibility data. During the dry season, the magnitude of the monthly average IDDI during 2003 was slightly higher than that of 1999. The monthly mean IDDI was in the range from 4 to 9 K over the Indian deserts, as well as over the deserts of Africa and Arabia. The maximum IDDI during a month was in the range from 6 to 18 K. Large IDDI values were observed even over vegetated regions (such as the vegetated part of Africa and central India), attributed to the presence of transported dust from nearby deserts."
"8931293800;7004864963;35585698100;7006643234;8786620100;7401891176;7102692123;6601961859;35461763400;","Spectral light absorption by ambient aerosols influenced by biomass burning in the Amazon Basin. I: Comparison and field calibration of absorption measurement techniques",2006,"10.5194/acp-6-3443-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33747629223&doi=10.5194%2facp-6-3443-2006&partnerID=40&md5=7995372ad6e272245d59c825a6e5eb14","Spectral aerosol light absorption is an important parameter for the assessment of the radiation budget of the atmosphere. Although on-line measurement techniques for aerosol light absorption, such as the Aethalometer and the Particle Soot Absorption Photometer (PSAP), have been available for two decades, they are limited in accuracy and spectral resolution because of the need to deposit the aerosol on a filter substrate before measurement. Recently, a 7-wavelength (λ) Aethalometer became commercially available, which covers the visible (VIS) to near-infrared (NIR) spectral range (λ=450-950 nm), and laboratory calibration studies improved the degree of confidence in these measurement techniques. However, the applicability of the laboratory calibration factors to ambient conditions has not been investigated thoroughly yet. As part of the LBA-SMOCC (Large scale Biosphere atmosphere experiment in Amazonia - SMOke aerosols, Clouds, rainfall and Climate) campaign from September to November 2002 in the Amazon basin we performed an extensive field calibration of a 1-λ. PSAP and a 7-λ, Aethalometer utilizing a photoacoustic spectrometer (PAS, 532 nm) as reference device. Especially during the dry period of the campaign, the aerosol population was dominated by pyrogenic emissions. The most pronounced artifact of integrating-plate type attenuation techniques (e.g. Aethalometer, PSAP) is due to multiple scattering effects within the filter matrix. For the PSAP, we essentially confirmed the laboratory calibration factor by Bond et al. (1999). On the other hand, for the Aethalometer we found a multiple scattering enhancement of 5.23 (or 4.55, if corrected for aerosol scattering), which is significantly larger than the factors previously reported (∼2) for laboratory calibrations. While the exact reason for this discrepancy is unknown, the available data from the present and previous studies suggest aerosol mixing (internal versus external) as a likely cause. For Amazonian aerosol, we found no absorption enhancement due to hygroscopic particle growth in the relative humidity (RH) range between 40% and 80%. However, a substantial bias in PSAP sensitivity that correlated with both RH and temperature (T) was observed for 20%<RH<30% and 24°C<T<26°C, respectively. In addition, both PSAP and Aethalometer demonstrated no sensitivity to gaseous adsorption. Although very similar in measurement principle, the PSAP and Aethalometer require markedly different correction factors, which is probably due to the different filter media used. Although on-site calibration of the PSAP and Aethalometer is advisable for best data quality, we recommend a set of ""best practice"" correction factors for ambient sampling based on the data from the present and previous studies. For this study, the estimated accuracies of the absorption coefficients determined by the PAS, PSAP and Aethalometer were 10, 15 and 20% (95% confidence level), respectively."
"57203012011;57208346904;","Effect of subgrid cloud-radiation interaction on climate simulations",2005,"10.1029/2005GL024432","https://www.scopus.com/inward/record.uri?eid=2-s2.0-32644434197&doi=10.1029%2f2005GL024432&partnerID=40&md5=b69028442ded7458bc5dadc7797c1e13","The mosaic representation of subgrid cloud-radiation interaction is implemented in the radiation scheme of the NCAR Community Climate Model version 3 (CCM3) to investigate its impacts on global climate simulations. It is found that the CCM3 with the modified radiation scheme enables the use of more realistic cloud amounts as well as cloud water contents while producing net radiative fluxes closer to observations. The improved vertical distribution of cloud water path based on the cloud-resolving model (CRM) simulations increases the radiative heating in the upper troposphere over the tropics, which reduces the long-standing cold bias in the temperature field. Consequently, not only the representation of cloud-radiation interactions is more physically consistent and accurate, but also the climate simulations are significantly affected and improved. Copyright 2005 by the American Geophysical Union."
"7005955015;24347548900;12139043600;12139310900;6506436908;","Response of the climate system to aerosol direct and indirect forcing: Role of cloud feedbacks",2005,"10.1029/2005JD006299","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31644442337&doi=10.1029%2f2005JD006299&partnerID=40&md5=a7ea4a199463df596341da872a4b3471","In this study, the response of the climate system to aerosol direct and indirect radiative forcing is investigated. Several multidecadal equilibrium simulations are carried out, using the NCAR CCM3 framework coupled to a separately developed aerosol treatment. The aerosol treatment includes, e.g., a life cycle scheme for particulate sulfate and black carbon (natural and anthropogenic), calculations of aerosol size distributions and CCN activation, as well as computations of direct and indirect forcing (1st and 2nd indirect effect). In all the simulations the full aerosol treatment is run online, hence responding interactively to changes in climate. By far the largest response is caused by the indirect forcing, with a globally averaged cooling of -1.25 K due to anthropogenic aerosols. The largest temperature reduction is found in the Northern Hemisphere because of a larger aerosol burden there. As a result of this cooling pattern, the Intertropical Convergence Zone is displaced southward by a few hundred kilometers. Interestingly, a similar, though less significant displacement is also found in the experiments with the direct effect alone, even though the globally averaged aerosol induced cooling is much weaker in that case, i.e., -0.08 K. The direct radiative forcing is much stronger at the surface than at the top of the atmosphere, and this leads to a slight weakening of the hydrological cycle. Comparing simulations with direct and indirect forcing combined to those with indirect and direct forcing separately, a residual, caused by nonlinear model feedbacks, is manifested through a reduction in precipitation. This reduction amounts to -0.5% in a global average and exceeds -2.5% in the Arctic, highlighting the role of high-latitude climate feedbacks. Globally, cloud feedback is negative in the sense that in the colder climate resulting from anthropogenic aerosol forcing, net cloud forcing is reduced by 15% compared to the original climate state. This is caused by a general cloud thinning, especially at high latitudes, while in the most polluted regions, clouds are thicker through the 2nd indirect effect. The 1st indirect effect, on the other hand, remains intact in the presence of climate feedbacks, yielding a similar signature of cloud droplet reduction as in the pure forcing simulations. Copyright 2005 by the American Geophysical Union."
"6602164207;7401776640;","An examination of the differences between surface and free-air temperature trend at high-elevation sites: Relationships with cloud cover, snow cover, and wind",2005,"10.1029/2005JD006150","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31644435340&doi=10.1029%2f2005JD006150&partnerID=40&md5=2607b5bdfc05c0c728263045c835b6aa","Contrasts in high-elevation surface and free-tropospheric temperatures between 1971 and 1996 are examined by comparing surface temperatures from a subset of 72 stations in the GHCN (Global Historical Climate Network) and CRU (Climatic Research Unit) homogeneity adjusted surface data sets with free-air temperatures interpolated to the same locations from NCEP/NCAR Reanalysis R1. The selected stations are above the mean elevation of the surrounding topography, often located on mountain summits. Surface temperatures, free-air temperatures, and their difference (ΔT) are found to be related to independent surface cloud observations from the NDP-026C archive, local wind speed, satellite records of snow cover (NSIDC), and reanalysis wind components. Significant correlations are observed at most stations, and correlation spatial patterns are consistent for different subperiods of the record (e.g., presatellite era versus satellite era). Stepwise regression models built to predict surface temperatures, free-air temperatures, and ΔT from the above meteorological parameters typically explain 20-40% of the temperature variability on an annual basis and more for individual seasons. The stationarity of relationships between temperature and snow/cloud/wind is examined by comparing the temporal trends in the original temperatures with predicted trends from the best fit regression model and trends in model residuals. This provides an assessment of how much of any ΔT trends can be accounted for by changes in meteorology. Significant daytime ΔT residual trends occur primarily in Turkey and eastern China, but significant nighttime ΔT residual trends are more geographically widespread. While daytime residual trends may be the result of surface radiative cooling by increasing anthropogenic aerosol, attribution of nighttime residual trends is uncertain. Copyright 2005 by the American Geophysical Union."
"7102055821;7401436524;55715215300;7406250414;","A statistically-based low-level cloud scheme and its tentative application in a general circulation model",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-29144519821&partnerID=40&md5=805f53118d2fc1483eff2c07e80aa574","In this study, a statistical cloud scheme is first introduced and coupled with a first-order turbulence scheme with second-order turbulence moments parameterized by the timescale of the turbulence dissipation and the vertical turbulent diffusion coefficient. Then the ability of the scheme to simulate cloud fraction at different relative humidity, vertical temperature profile, and the timescale of the turbulent dissipation is examined by numerical simulation. It is found that the simulated cloud fraction is sensitive to the parameter used in the statistical cloud scheme and the timescale of the turbulent dissipation. Based on the analyses, the introduced statistical cloud scheme is modified. By combining the modified statistical cloud scheme with a boundary layer cumulus scheme, a new statistically-based low-level cloud scheme is proposed and tentatively applied in NCAR (National Center for Atmospheric Research) CCM3 (Community Climate Model version 3). It is found that the simulation of low-level cloud fraction is markedly improved and the centers with maximum low-level cloud fractions are well simulated in the cold oceans off the western coasts with the statistically-based low-level cloud scheme applied in CCM3. It suggests that the new statistically-based low-level cloud scheme has a great potential in the general circulation model for improving the low-level cloud parameterization."
"55760862100;7404136779;","Multi-year simulation of the East Asian monsoon and precipitation in China using a regional climate model and evaluation",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-29144444641&partnerID=40&md5=53b43a599167364eb212a2174a1a453c","By using the regional climate model (RegCM_NCC), East Asian monsoon and precipitation over China during 1998 to 2002 are simulated. Results show that the model can well reproduce the seasonal patterns of mean circulation as well as the intensity and seasonal march of the East Asian monsoon. The simulated onset or retreat time of the West Pacific subtropical high, and the intensity and location of the South Asian high are consistent with the fact. The spatial distribution and transport of moisture in lower layer are also well simulated. The seasonal variations of regional rainfall and temperature are reproduced in the model, with three northward shift time and intensity of the rain belts over the sub-regions (such as Mid-Lower Yangtze basins and South China) well corresponding to the observation. However, the simulated summer monsoon is stronger compared with NCEP reanalysis fields, with the location of subtropical high being further north by 2-3 degrees than normal. Error evaluation shows that there is a discernible systematic bias in the simulated mean circulation pattern, with air temperature bias being positive over the land and negative over the ocean in the lower troposphere in summer. The systematic bias exaggerates the summer temperature difference between the land and ocean, which may be a main responsible factor for the stronger simulated summer monsoon, thus resulting in the overestimated rainfall in North China and it can not reflect well the abnormal rainfall distribution in these 5 years. The deficiency may be mainly contributed to the complex topography and cloud-radiation parameterization scheme. The analyses also indicate that it is difficult to simulate the persistent abnormal precipitation pattern over China. It is necessary to improve the model's capability further."
"8245528300;8610905400;18437501600;7004060748;","ICESat's new perspective on ice shelf rifts: The vertical dimension",2005,"10.1029/2005GL025070","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31544464037&doi=10.1029%2f2005GL025070&partnerID=40&md5=666aa9b344f11212fdc7e737b219b74b","The small footprint (∼70 m) and ∼172 m alongtrack spacing of the Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud and land Elevation Satellite (ICESat) provides unprecedented horizontal resolution for a satellite altimeter. This enables ICESat to map many previously unresolved features on ice shelves, such as crevasses, rifts, grounding zones and ice fronts. We present examples of ICESat-derived elevation data showing topography over rifts on the Amery and Ross ice shelves, widths of rifts and as estimates of the thickness of mélange (a collection of ice and snow trapped inside the rifts). We show that mélange thickness remains constant over the ICESat data period and tends to be thicker in older rifts. We validate the ICESat-derived mélange depth estimate with an in situ measurement on the Ross Ice Shelf. Copyright 2005 by the American Geophysical Union."
"7005956183;6603247427;56270311300;7102953444;","How accurate did GCMs compute the insolation at TOA for AMIP-2?",2005,"10.1029/2005GL024411","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31544476518&doi=10.1029%2f2005GL024411&partnerID=40&md5=3e99a3650a5f6b1bf78b1754a6de5e27","Monthly averages of solar radiation reaching the Top of the Atmosphere (TOA) as simulated by 20 General Circulation Models (GCMs) during the period 1985-1988 are compared. They were part of submissions to AMIP-2 (Atmospheric Model Intercomparison Project). Monthly averages of ISCCP-FD (International Satellite Cloud Climatology Project - Flux Data) are considered as reference. Considerable discrepancies are found: Most models reproduce the prescribed Total Solar Irradiance (TSI) value within ±0.7 Wm-2. Monthly zonal averages disagree between ±2 to ±7 Wm-2, depending on latitude and season. The largest model diversity occurs near polar regions. Some models display a zonally symmetric insolation, while others and ISCCP show longitudinal deviations of the order of ±1 Wm-2. With such differences in meridional gradients impacts in multiannual simulations cannot be excluded. Sensitivity studies are recommended. Copyright 2005 by the American Geophysical Union."
"6603035763;12041219200;12041288200;7005348433;35618697400;7201368967;7202245396;55476061600;8360601400;","ICESat measurements reveal complex pattern of elevation changes on Siple Coast ice streams, Antarctica",2005,"10.1029/2005GL024289","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31544469752&doi=10.1029%2f2005GL024289&partnerID=40&md5=13338d15bda17b0d7e4e1a94e0b6ba16","We compare ICESat data (2003-2004) to airborne laser altimetry data (1997-98 and 1999-2000) to monitor surface changes over portions of Van der Veen (VdVIS), Whillans (WIS) and Kamb ice streams (KIS) in the Ross Embayment of the West Antarctic Ice Sheet. The spatial pattern of detected surface changes is generally consistent with earlier observations. However, important changes have occurred during the past decade. For example, areas on the VdVIS and WIS, where large thinning was detected by the airborne surveys, are now closer to being in balance. The upper trunk of KIS continues to build up with thickening rates reaching 0.4 m/year. Our results provide new evidence that the overall mass balance of the region is becoming more positive, but a significant spatial variability exists. They also demonstrate the potential of ICESat data for detecting spatial patterns of surface elevation change in Antarctica. Copyright 2005 by the American Geophysical Union."
"7202660824;7403288995;","Surface contribution to planetary albedo variability in cryosphere regions",2005,"10.1175/JCLI3555.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31544451828&doi=10.1175%2fJCLI3555.1&partnerID=40&md5=054a1cb22ea09e895bd754b796a90f87","Climatological planetary albedo obtained from the International Satellite Cloud Climatology Project (ISCCP) D-series flux dataset is broken down into contributions from the surface and atmosphere in cryosphere regions. The atmosphere accounts for much more of climatological planetary albedo (≥75%) than the surface at all times of the year. The insignificance of the surface contribution over highly reflective cryosphere regions is attributed mostly to the damping effect of the atmosphere. The overlying atmosphere attenuates the surface's contribution to climatological planetary albedo by reducing the number of solar photons initially reaching the surface and the number of photons initially reflected by the surface that actually reach the top of the atmosphere. The ISCCP datasets were also used to determine the relative contributions of the surface and atmosphere to seasonal and interannual planetary albedo variability in cryosphere regions. Even damped by the atmosphere to the same degree as in the climatological case, the surface contribution dominates the variability in planetary albedo on seasonal and interannual time scales. The surface accounts for about 75% of the change in climatological planetary albedo from one season to another with similar zenith angle and more than 50% of its interannual variability at nearly all times of the year, especially during seasons with extensive snow and sea ice extent. The dominance of the surface in planetary albedo variability is because surface albedo variability associated with snow and ice fluctuations is significantly larger than atmospheric albedo variability due to cloud fluctuations. The large effect of snow and ice variations on planetary albedo variability suggests that if cloud fields do not change much in a future warmer climate, a retreat of snow cover or sea ice would lead to a significant increase in net incoming solar radiation, resulting in an enhancement of high-latitude climate sensitivity. © 2005 American Meteorological Society."
"23082420800;7003531755;8884425800;","Why are there tropical warm pools?",2005,"10.1175/JCLI3582.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31544475690&doi=10.1175%2fJCLI3582.1&partnerID=40&md5=60de22f0b98423aa4d1840863cce6ec5","Tropical warm pools appear as the primary mode in the distribution of tropical sea surface temperature (SST). Most previous studies have focused on the role of atmospheric processes in homogenizing temperatures in the warm pool and establishing the observed statistical SST distribution. In this paper, a hierarchy of models is used to illustrate both oceanic and atmospheric mechanisms that contribute to the establishment of tropical warm pools. It is found that individual atmospheric processes have competing effects on the SST distribution: atmospheric heat transport tends to homogenize SST, while the spatial structure of atmospheric humidity and surface wind speeds tends to remove homogeneity. The latter effects dominate, and under atmosphere-only processes there is no warm pool. Ocean dynamics counter this effect by homogenizing SST, and it is argued that ocean dynamics is fundamental to the existence of the warm pool. Under easterly wind stress, the thermocline is deep in the west and shallow in the east. Because of this, poleward Ekman transport of water at the surface, compensated by equatorward geostrophic flow below and linked by equatorial upwelling, creates a cold tongue in the east but homogenizes SST in the west, creating a warm pool. High clouds may also homogenize the SST by reducing the surface solar radiation over the warmest water, but the strength of this feedback is quite uncertain. Implications for the role of these processes in climate change are discussed. © 2005 American Meteorological Society."
"6507681572;12139476000;8670213100;6603395511;6602137840;7004639116;6602844274;6701796418;","Seasonal heat budget of the Mediterranean Sea",2005,"10.1029/2004JC002566","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31644445830&doi=10.1029%2f2004JC002566&partnerID=40&md5=7966c6c2b76a5c34792418257c9762bd","We calculate the monthly components of the Mediterranean Sea heat budget, namely the net shortwave, net longwave, latent, sensible heat fluxes, and heat storage change, for years 1984-2000. The radiative components of the seasonal heat budget are derived by a radiation transfer model, while in most other studies bulk formulae are used. A variety of data are required to run the model, among which are cloud data from International Satellite Cloud Climatolog Project (ISCCP) D2 data set, aerosol data from Global Aerosol Data Set (GADS), temperature and humidity from National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and European Centre for Medium-range Weather Forecasts (ECMWF) Re-Analysis (ERA-40), and oceanographical data from Mediterranean Data Archaeology and Rescue (MEDAR) MEDATLAS database and the World Ocean Atlas 2001. We compare two methods for the estimation of the monthly latent heat flux and evaporation: the bulk aerodynamic and the heat balance. The average annual evaporation rate for the Mediterranean Sea, based on the heat balance method, is estimated at 1500 ± 190 mm yr-1. The bulk aerodynamic method produces estimates of the annual evaporation rate in the range 1060-1280 mm yr-1, depending on the source of the input data. The analysis of the heat content shows that the solar heat absorbed by the sea during summer is redistributed to winter evaporation via heat storage by the sea. Thus the peak evaporation occurs in winter and is mainly driven by energy released (100-150 Wm-2) from sea heat storage. Copyright 2005 by the American Geophysical Union."
"7401581934;","A global profiling system for improved weather and climate prediction",2005,"10.1175/BAMS-86-12-1747","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31644448153&doi=10.1175%2fBAMS-86-12-1747&partnerID=40&md5=36cd38d0105c0a9049327c4333b2df48","A new long-term global observing system is proposed that would provide routine, detailed vertical profiles of measurements in the atmosphere and oceans. The system, which would need to be designed, developed, and operated by a consortium of nations, would consist of 240 equally spaced, fixed locations over oceans and polar regions. It would use unmanned aerial vehicles (UAVs) in lower stratosphere to drop sondes every 72 h, and buoys in the ocean to report surface and subsurface data. In addition, the UAVs could descend routinely at a few locations detailed profiles of clouds, aerosols, and chemistry. The objective of the observing system would be to improve weather and climate prediction. It would address the important long-term climate issue by providing better monitoring of global and regional change, better measurement of climate feedbacks, and data that can be used to improve long-term climate models. It is argued that the combination of fixed and adaptive soundings over oceans and polar regions would significantly reduce initial analysis error, thus, leading to better weather prediction. The system. which should be designed to complement planned satellite and surface systems, could be operational by the middle of the next decade."
"7404147955;7404136779;55712637800;48361871200;","Recent studies on attributions of climate change in China",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644745470&partnerID=40&md5=0b4789d0c49b6502b3e8f252ae4e6f49","Attributions of floods/cooler along the Yangtze River Valley and droughts/warmer in North China for the last 25 years have been reviewed in this paper. Both natural climate variability and human activities are considered. Some stronger evidences contributed to the natural climate variability, such as decadal and interdecadal variabilities of East Asian summer monsoon, the periodicities and transitions of rainfall and temperature changes in China, abrupt climate change, NAO, AO, AAO, ENSO, and snow cover. The signals produced by the human activities such as greenhouse gases and ""brown clouds"" likely play the role for the patterns. But the physical feedbacks and mechanisms still keep ambiguous and vague. More researches should be carried out in future to solve this issue."
"6603081424;7003398947;","Cloud inhomogeneity from MODIS",2005,"10.1175/JCLI3591.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31344475952&doi=10.1175%2fJCLI3591.1&partnerID=40&md5=2d439c675f70f6d5dd4503b86b6d7ec7","Two full months (July 2003 and January 2004) of Moderate Resolution Imaging Spectroradiometer (MODIS) Atmosphere Level-3 data from the Terra and Aqua satellites are analyzed in order to characterize the horizontal variability of vertically integrated cloud optical thickness (""cloud inhomogeneity"") at global scales. The monthly climatology of cloud inhomogeneity is expressed in terms of standard parameters, initially calculated for each day of the month at spatial scales of 1° × 1° and subsequently averaged at monthly, zonal, and global scales. Geographical, diurnal, and seasonal changes of inhomogeneity parameters are examined separately for liquid and ice phases and separately over land and ocean. It is found that cloud inhomogeneity is overall weaker in summer than in winter. For liquid clouds, it is also consistently weaker for local morning than local afternoon and over land than ocean. Cloud inhomogeneity is comparable for liquid and ice clouds on a global scale, but with stronger spatial and temporal variations for the ice phase, and exhibits an average tendency to be weaker for near-overcast or overcast grid points of both phases. Depending on cloud phase, hemisphere, surface type, season, and time of day, hemispheric means of the inhomogeneity parameter v (roughly the square of the ratio of optical thickness mean to standard deviation) have a wide range of ∼1.7 to 4, while for the inhomogeneity parameter X (the ratio of the logarithmic to linear mean) the range is from ∼0.65 to 0.8. The results demonstrate that the MODIS Level-3 dataset is suitable for studying various aspects of cloud inhomogeneity and may prove invaluable for validating future cloud schemes in large-scale models capable of predicting subgrid variability."
"35464731600;7004174939;55947099700;57198938123;7801610570;7006421484;7404061081;7005793702;7005399437;7003397919;24578264300;35887706900;","A critical examination of the residual cloud contamination and diurnal sampling effects on MODIS estimates of aerosol over ocean",2005,"10.1109/TGRS.2005.858430","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29044438735&doi=10.1109%2fTGRS.2005.858430&partnerID=40&md5=9d0fb14678c61d8f98a802715be18be1","Observations of the aerosol optical thickness (AOT) by the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard Terra and Aqua satellites are being used extensively for applications to climate and air quality studies. Data quality is essential for these studies. Here we investigate the effects of unresolved clouds on the MODIS measurements of the AOT. The main cloud effect is from residual cirrus that increases the AOT by 0.015 ± 0.003 at 0.55 μm. In addition, lower level clouds can add contamination. We examine the effect of lower clouds using the difference between simultaneously measured MODIS and AERONET AOT. The difference is positively correlated with the cloud fraction. However, interpretation of this difference is sensitive to the definition of cloud contamination versus aerosol growth. If we consider this consistent difference between MODIS and AERONET to be entirely due to cloud contamination we get a total cloud contamination of 0.025 ± 0.005, though a more likely estimate is closer to 0.020 after accounting for aerosol growth. This reduces the difference between MODIS-observed global aerosol optical thickness over the oceans and model simulations by half, from 0.04 to 0.02. However it is insignificant for studies of aerosol cloud interaction. We also examined how representative are the MODIS data of the diurnal average aerosol. Comparison to monthly averaged sunphotometer data confirms that either the Terra or Aqua estimate of global AOT is a valid representation of the daily average. Though in the vicinity of aerosol sources such as fires, we do not expect this to be true. © 2005 IEEE."
"6603613067;7005453346;15763329000;","The role of shallow convection in the water and energy cycles of the atmosphere",2005,"10.1007/s00382-005-0051-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29244444210&doi=10.1007%2fs00382-005-0051-2&partnerID=40&md5=bd7209b3d14fa1523acff7056fb10522","The Canadian Centre for Climate Modelling and Analysis atmospheric general circulation model (AGCM4) is used to study the role of shallow convection in the hydrologic and energy cycles of the atmosphere. Sensitivity tests with AGCM4 show a marked effect of the parameterization of shallow convection in the model. In particular, including the parameterization of shallow convection produces considerably enhanced vertical mixing and decreased stratiform cloud amounts in the lower subtropical atmosphere over the oceans. The differences in simulated stratiform cloud amounts are associated with a change in the globally averaged outgoing shortwave radiative flux at the top of the atmosphere of about 11 W m-2. Additionally, precipitation rates are considerably reduced for stratiform clouds and enhanced for convective clouds in the subtropics, if the parameterization of shallow convection is included in the model. Additional tests show that the simulated responses in cloud amounts and precipitation to the treatment of shallow convection are robust. Additional simulations with modified closures for deep convection and other changes to the treatment of convection in the model still lead to similar responses of the model results. © Springer-Verlag 2005."
"57189585133;7006307463;10139397300;57203200427;7102517130;7005135473;7102805852;35464731600;56270311300;7006634316;7004174939;7202079615;55947099700;57203174863;7004678728;7004325649;7003865921;37032346000;","An ""a-train"" strategy for quantifying direct climate forcing by anthropogenic aerosols",2005,"10.1175/BAMS-86-12-1795","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31644436460&doi=10.1175%2fBAMS-86-12-1795&partnerID=40&md5=7d503fd1b42c806edf38c710aec08847","This document outlines a practical strategy for achieving an observationally based quantification of direct climate forcing by anthropogenic aerosols. The strategy involves a four-step program for shifting the current assumption-laden estimates to an increasingly empirical basis using satellite observations coordinated with suborbital remote and in situ measurements and with chemical transport models. Conceptually, the problem is framed as a need for complete global mapping of four parameters: clear-sky aerosol optical depth σ radiative efficiency per unit optical depth E, fine-mode fraction of optical depth ff, and the anthropogenic fraction of the fine mode faf. The first three parameters can be retrived from satellites, but correlative, suborbital measurements are required for quantifying the aerosol properties that control E, for validating the retrieval of ff and for partitioning fine-mode σ between natural and anthropogenic components. The satellite focus is on the ""A-Train,"" a constellation of six spacecraft that will fly in informtion from about 2005 to 2008. Key satellite instruments for this report are the Moderate Resolution Imaging Spectroradiometer (MODIS) and Clouds and the Earth's Radian Energy System (CERES) radiometers on Aqua the Onzone Monitoring Instrument (OMI) radiometer on the Polarization and anistropy of reflectances for Atmospheric Sciences coupled with obervations from a lidar (PARASOL), and the Cloud and Aeroso lide with othogonal Polarization (CALIOP) lidar on the Cloud-Aerosol Lidar on the Cloud-Aerosol Lidar and Infared Pathfinder Satellite Obervations (CALIPSO). This strategy is offered as an initial framework-subject to improvement over time-for scientists around the world to participate the A-Train opportunity. It is a specific implementations of the Progressive Aerosol Retrieval and Assimilation Global Observing Network (PARAGON) program, presented earlier in this journal, which identified the integration of diverse data as the central challenge to progress in quantifying global-scale aerosol effects. By designing a strategy around this need for integration, we develop recommendations for both satellite data interpretation and correlative suborbital activities that represent, in many respects, departures from current practice."
"6506612024;11939464600;6602675795;7201389451;","Thermal bioclimate conditions in the alpine regions of Austria",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-31344455424&partnerID=40&md5=921ecd261914ed940de62c4585b7874d","Data of 46 climate stations located from 1000 in to 3105 m a.s.l. were used to describe the thermal human bioclimate conditions in the alpine regions of Austria. Austria possesses a dense network of climate stations with daily measurements and observations of air temperature, relative humidity, wind velocity and mean cloud cover at 7, 14 and 19 LMT. To show the special climate conditions in alpine regions the behaviour of this parameters in relationship to the human energy balance is used to give a description of the effect of the thermal environment on humans. The importance of topography leading to inversions during the cold seasons and clothing resistance to modify the individual thermal bioclimate will be shown exemplarily."
"24168181300;7006232979;7102546082;8940115800;","Estimation of uncertainty of direct radiative forcing of the aerosol for a rural site in central Europe",2005,"10.1016/j.atmosenv.2005.08.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27544451182&doi=10.1016%2fj.atmosenv.2005.08.012&partnerID=40&md5=0efbe74be919bd722bacc17f58f82dec","Direct climate forcing due to scattering and absorption of the main aerosol components (ammonium sulfate and total carbon) was estimated seasonally in Hungary by a box model. Ammonium sulfate played an important role in the direct forcing while the carbonaceous aerosol contributed significantly to the development of extinction. In summer, the scattering effect of both species showed a maximum (ammonium sulfate: -2.21±1.73 W m-2, total carbon: -0.88±0.73 W m-2), while the absorption of carbon was the most significant in autumn (+0.40±0.41 W m-2). Uncertainty of these data was obtained by using the theory of error propagation and by taking into consideration the standard deviation of the experimental parameters. The relatively high values of the calculated relative standard deviations of the climate forcing data were attributed partly to the large number of the model parameters (9 and 11) and partly to their large uncertainty. The calculated uncertainties of various forcings were found to be in between the factors of 1.7 and 2.1 which were lower than those generally applied in forcing calculations. Parameter sensitivity analysis of the model equation proved that the reliability of the calculated data could be improved if attention is paid to the measurement of certain parameters such as: mass concentration, cloud coverage, surface albedo, upscattered fraction, single-scattering albedo and the fractional transmittance of the atmosphere. © 2005 Elsevier Ltd. All rights reserved."
"57210531887;7102355142;","A numerical approach to evaluate the risk of differential surface icing on pavements with insulated sections",2005,"10.1016/j.coldregions.2005.05.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28244446975&doi=10.1016%2fj.coldregions.2005.05.004&partnerID=40&md5=ff46c075746f02f6147cf1127b2f5811","This paper presents the results of a numerical study on the differential icing risk at the surface of pavements with insulated sections in the Province of Quebec, Canada. Differential icing situations occur when slippery conditions form on the surface of insulated pavement sections while adjacent conventional pavement sections maintain dry surface conditions. A heat transfer model that considers the climate conditions and the pavement properties is used to compute the surface temperature of conventional and insulated pavements. Variations of climate conditions on daily cycles are obtained from a new ideal climate model developed on the basis of 30-year period monthly data of solar radiation, air temperature, wind speed and cloud cover. It was established that the period with the highest icing risk on all pavements (insulated or not) occurs during the late Fall season. However, as soon as the frost front reaches the insulating layer, the icing risks on insulated pavement sections increase drastically. In the Province of Quebec, the current insulated pavement design method prevents most of the differential icing situations only for the warmest regions of the Province. Future design method will have to relate the thickness of the granular layer placed atop of the insulating layer to mean climate conditions and pavement properties. © 2005 Elsevier B.V. All rights reserved."
"55511340100;9271448600;55193284100;7201791739;","Analysis to significant climate change in aerosol influence domain of Beijing and its peripheral areas by EOF mode",2005,"10.1360/05yd0392","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845927681&doi=10.1360%2f05yd0392&partnerID=40&md5=2a96b8bc36ce5e9bceb0bf9efc8e5ae2","Using the total ozone mapping spectrometer (TOMS) aerosol optical depth (AOD) data and the sunshine duration, fog days, low cloud cover (LCC), etc. meteorological data in 1979-2000 in North China, as well as empirical orthogonal function (EOF) mode statistical analyses method, the winter aerosol distributive character of Beijing and peripheral city agglomeration and its influence effect on regional climate are investigated in this paper, especially the relation between aerosol influence effect and distinct change regions of eigenvectors of EOF mode. It is found from analyzing the regional distribution of the long-term averaged winter TOMS AOD that there is a large-scale relatively stable high value zone of aerosol concentration in the valley of the Beijing and peripheral U-shape megarelief. A high correlation area of AOD between Beijing and its southern peripheralexists in winter, and in this significant region of aerosol interaction, there is ""in-phase"" character of the interannual variations of winter AOD, fog days, and LCCs. It indicates that the variations of aerosol in Beijing and its peripheral areas have impacts on interannual changes of fog days and LCCs in this area. The EOF analyses of the meteorological data further reveal the climate change regions and long-term trends of winter sunshine duration-reducing, and LCC- and fog days-increasing in North China. The areas of significant changes of the first EOF eigenvectors (FEE) of sunshine duration, fog days, LCCs almost superpose on corresponding marked regions of interdecadal differences between the 1990s and 1980s, and all accord with the S-N zonal high value pattern and high correlation region of winter AOD in Beijing and its peripheral areas. Interannual variations of their associated time coefficients (ATC) are in phase with that of regional mean AOD, and both of them have a secular rising trend. Results by EOF mode analyses depict the regional climatic change principal character of winter sunshine duration-reducing, and LCC- and fog days-increasing in peripheral areas to the south of Beijing, and reveal the regional influence effect of aerosol, i.e. the high value zone of long-term averaged winter AOD, significant change regions of FEE of sunshine duration, fog days, and LCC all lie in peripheral city agglomeration to the south of Beijing. These distributive features above suggest that there exists a regional strengthening trend of aerosol climatic effect within influence domain in peripheral city agglomeration to the south of Beijing. Copyright by Science in China Press 2005."
"9276067100;7007015435;24578134500;","Using remote-sensing data to determine equilibrium-line altitude and mass-balance time series: Validation on three French glaciers, 1994-2002",2005,"10.3189/172756505781829106","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644674530&doi=10.3189%2f172756505781829106&partnerID=40&md5=c855bbc53c6108d8955a37df2607cc91","Alpine glaciers are very sensitive to climate fluctuations, and their mass balance can be used as an indicator of regional-scale climate change. Here, we present a method to calculate glacier mass balance using remote-sensing data. Snowline measurements from remotely sensed images recorded at the end of the hydrological year provide an effective proxy of the equilibrium line. Mass balance can be deduced from the equilibrium-line altitude (ELA) variations. Three well-documented glaciers in the French Alps, where the mass balance is measured at ground level with a stake network, were selected to assess the accuracy of the method over the 1994-2002 period (eight mass-balance cycles). Results obtained by ground measurements and remote sensing are compared and show excellent correlation (r2 &gt; 0.89), both for the ELA and for the mass balance, indicating that the remote-sensing method can be applied to glaciers where no ground data exist, on the scale of a mountain range or a given climatic area. The main differences can be attributed to discrepancies between the dates of image acquisition and field measurements. Cloud cover and recent snowfalls constitute the main restrictions of the image-based method."
"7102913661;35451476400;8689674700;6602352339;7004885872;7403253796;35320163700;7004176296;8941151400;8534751800;7801634218;7004126618;7005669183;6603711967;7403339846;36901512000;7003545995;6701378450;8596044600;8917907300;7410177774;35277762300;7005361537;","Coupling between land ecosystems and the atmospheric hydrologic cycle through biogenic aerosol pathways",2005,"10.1175/BAMS-86-12-1738","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31644449366&doi=10.1175%2fBAMS-86-12-1738&partnerID=40&md5=4f0ffeb8f5e445a615a90010a1b58dbb","Important land surface characteristics affect the way in which water is transferred to the atmosphere, processed in the atmosphere, and eventually returned to the surface. In turn, the amount of water in the atmosphere and returning to Earth affects many of the key properties of the land surface. It is hypothesized that feedbacks between the terrestrial biosphere and the atmosphere by way of biogenic aerosol pathways exist, and that these feedbacks can be important in both direct and indirect radiative processes. By investigating this coupled cycle, a better understanding of the Earth system, including climate change, regional and global atmospheric chemistry, haze and visibility, weather, and changes in land cover is obtained."
"12243432700;7003631214;7005399437;","Optical properties of the atmospheric aerosol during forest fires of 2002 in the Moscow region",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645824749&partnerID=40&md5=65906777d0a8971103ef4d65b22edcfc","Data from the CIMEL sun photometer, operating in Moscow as part of the AERONET program, and HAZEMETER sun photometer measurements at the Zvenigorod research station of Moscow State University are used to analyze optical properties of aerosols during forest fires in the Moscow region in July-September 2002. The changes in aerosol loading in Moscow and Zvenigorod were consistent, demonstrating the propagation of a smoke aerosol ""cloud"" over a large area, and were in agreement with numbers of fires and with flammability indices in the Moscow region. The aerosol optical thickness during a fire period is shown to reach extremely large values (up to 2.94). The probability of cases with τ500 &gt; 0.8, which actually do not occur under typical Moscow conditions, is about 24%. Relatively large values of the single-scattering albedo ω0,673 = 0.92-0.95) indicate that the smoke from fires scatter far more than absorb particles. The optical properties of the smoke aerosol in Moscow agree with those measured at other AERONET stations, where the dominant emission source is smoldering from wood fuels rather than active burning."
"6602675795;6506612024;11939464600;7201389451;","Thermal human bioclimatic conditions for Austria and the Alps",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-31344453539&partnerID=40&md5=b3b69149174c5699e2f685baf70916a5","Daily measurements and observations at numerous times of air temperature, relative humidity, wind velocity and mean cloud cover are the required data for the calculation of the Physiological Equivalent Temperature PET. PET represents a thermal index, which is based on the human energy balance of the human body, for the description of the effect of the thermal environment on humans. We analysed the thermal human bioclimate in Austria using the data from the dense climate network with daily measurements and observations at 7, 14 and 19 LST of 201 stations covering the period 1991 to 2000 as input to compute PET. The results were compared with the outcome of the computation using the synoptic data not only from Austria but also from the surrounding countries and the Alps region. The obtained results give fundamental information often demanded by the tourism and recreation authorities."
"12142292800;7004154240;","Evaluation of snow depth and soil temperatures predicted by the hydro-thermodynamic soil-vegetation scheme coupled with the fifth-generation Pennsylvania State University-NCAR mesoscale model",2005,"10.1175/JAM2311.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31944441761&doi=10.1175%2fJAM2311.1&partnerID=40&md5=445974e1b4248eb896a3599f03caffbd","The Hydro-Thermodynamic Soil-Vegetation Scheme (HTSVS) coupled in a two-way mode with the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (NCAR) Mesoscale Meteorological Model (MM5) is evaluated for a typical snowmelt episode in the Baltic region by means of observations at 25 soil temperature, 355 snow-depth, and 344 precipitation sites that have, in total, 1000, 1775, and 1720 measurements, respectively. The performance with respect to predicted near-surface meteorological fields is evaluated using reanalysis data. Snow depth depends on snow metamorphism, sublimation, and snowfall. Because in the coupled model these processes are affected by the predicted surface radiation fluxes and cloud and precipitation processes, sensitivity studies are performed with two different cloud microphysical schemes and/or radiation schemes. Skill scores are calculated as a quality measure for the coupled model's performance for a typical forecast range of 120 h for a typical spring (snowmelt) weather situation in the Baltic region. Discrepancies between predicted and observed snowdepth changes relate to the coupling. Enhanced water supply to the atmosphere, which results from water that was assumed to be open in MM5 but was actually ice covered in nature, finally leads to an overestimation of snowfall (input to HTSVS) and changes in snow depth (output). The resolution-dependent discrepancies between the terrain height in the model and real world also lead to snowfall where none occurred. For heavy snowfall the performance of the coupled model with respect to predicted snow-depth changes becomes nearly independent of the choice of the cloud microphysical and radiation schemes. As compared with observed changes in snow depth, the coupled model simulation using the Schultz scheme in conjunction with the radiation scheme from the Community Climate Model, version 2, (CCM2) predicts snow-depth changes of less than 2.5 mm considerably better than the other combinations that were tested. For thick snowpacks, the accuracy of the snow-depth decrease resulting from metamorphism strongly depends on the initial value of snow density. The coupled model acceptably captures the soil temperature diurnal cycles, the observed soil temperature increase with time, and the soil temperature behavior with depth. In general, discrepancies between simulated and observed soil temperatures decrease with soil depth. Simulations performed with the so-called CLOUD radiation scheme capture soil temperature minima and maxima better than do simulations performed with the CCM2 scheme. © 2005 American Meteorological Society."
"7005869171;7101958466;6602247304;35596112700;","A comparison of the conservation of number concentration for the continuous collection and vapor diffusion growth equations using one- and two-moment schemes",2005,"10.1175/JAM2314.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31944438912&doi=10.1175%2fJAM2314.1&partnerID=40&md5=71c17c7a4782a5a06f4c84b022fb5f51","Once- and two-moment parameterizations are integrated over hydrometeor diameters D(0, ∞) for vapor diffusion and the continuous collection growth processes. For the conditions specified, the total number concentration of collector particles should be conserved. To address the problem, the gamma distribution function is used for the spectral density function. Predicted variables can include total mixing ratio q, total number concentration Nt, and characteristic diameter Dn (inverse of the distribution slope λ). In all of the cases, the slope intercept no is diagnosed or specified. The popular one- and two-moment methods that are explored include the one-moment method in which q is predicted, no is specified, and Nt and Dn are diagnosed; the one-moment method in which q is predicted, Dn is specified, and Nt and no are diagnosed; the two-moment method in which q and Dn are predicted and Nt and no are diagnosed; and the two-moment method in which q and Nt are predicted and no and Dn are diagnosed. It is demonstrated for the processes examined that all of the schemes 1) fail to conserve Nt for the collector particles when Nt should be conserved and 2) have other unphysical attributes, except for the two-moment method in which q and Nt are predicted. In recent years there has been a dramatic increase in the use of more-sophisticated microphysical parameterizations in cloud, mesoscale, and climate models, and it is increasingly important for a model user to be cognizant of the strengths and weaknesses of the parameterizations in complex models. © 2005 American Meteorological Society."
"16427682500;","Solar forcing of climate. 1: Solar variability",2005,"10.1007/s11214-005-7046-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29344438621&doi=10.1007%2fs11214-005-7046-5&partnerID=40&md5=e075c7718d6e89e1e6b5ea440f28f6d6","We describe the properties of the Sun, those of its Active Regions (Centres of Activity, ARs or CAs) and the 11 and 22-year cycles as observed via the variable numbers of sunspots. We describe the variations with time of the solar irradiance and of the flux of ejected magnetised plasma. We discuss the probable cause of solar variability. Planetary influences are ruled out; the variability is intrinsic and is described by the solar dynamo. The dynamo is characterised by internal toroidal and more superficial poloidal fields, interchanging and alternating in a 22-year periodicity. From these two components in the solar magnetic fields emanate two possible scenarios for the Sun-climate interaction. Solar irradiance variations are related to those in the solar toroidal magnetic fields. The fraction of the solar irradiance that reaches the Earth's ground level and low troposphere is emitted by the solar photosphere. That fraction does not significantly vary since the quiet photosphere does not significantly vary during the cycle. The variable part of the solar radiation flux is mainly emitted by the chromospheric parts of the CAs. That radiation component does not reach the Earth's troposphere since it is absorbed in the higher, stratospheric terrestrial layers. Tropospheric solar-driven variations should therefore be due to stratosphere-troposphere coupling. The Group Sunspot number R Gs is a proxy for the variable irradiance component and for the toroidal field variations. Ejected solar plasma clouds such as the Coronal Mass Ejections (CMEs) and plasma ejected from Ephemeral Solar Regions and from the polar facular regions are related to variations in the poloidal magnetic fields. On the average they have their maximum intensity about a year after the maximum number of spots: we call this interval the Energetic Emissions Delay. These gas clouds fill the heliosphere with magnetised plasma. Thus, by emitting magnetised plasma, the Sun influences the Earth's atmosphere indirectly, by heliospheric modulation of the component of the galactic cosmic radiation (CR) that reaches tropospheric levels. Modulation is only important for cosmic ray particles with energies below about 50 GeV. Cosmic ray ionisation plays a minor role at ground level but it is the predominant ionising agent in higher atmospheric layers, already above a few kilometres. The amplitudes of the CR variations depend on those of the solar cycle. The atmospheric rate of ionisation varies with CR-intensity. A current hypothesis is that the variable ionisation may affect the degree of cloudiness. Cosmogenic radionuclides such as 10Be are proxies for this influence and for the poloidal field variations. The R G and cosmogenic radionuclide proxies, although loosely correlated, refer to the two different aspects of the solar dynamo with their different terrestrial effects; they do not reach maximum intensity simultaneously and should therefore neither be confused nor be interchanged. Cases have occurred in which the one varied strongly while the other did hardly or not at all. The explanation must be intrinsic in dynamo theory. There is a significant solar signal in the troposphere; it depends on latitude and longitude. A physical investigation of the cause of the Sun-climate relationship based on one unique ΔT(time)-curve, assumed valid for the whole Earth's surface, is therefore basically incorrect. Never during the past 10,000 years has the Sun been as active in ejecting magnetised plasma as during the past few decades. Estimates suggest that the level of solar activity may recently have passed its maximum and that it may decrease in coming decades. Solar activity is variable with six well-determined quasi-periodicities. Attempts to theoretically describe the solar dynamo have so far succeeded only in explaining the qualitative aspects. They fail in a numerical description and notably in one that would permit one to forecast solar activity with acceptable precision. This is so because the solar dynamo is a non-linear system that occasionally shows phase catastrophes. It is a quasi-periodic engine with the properties of deterministic chaos. ""The future of such a chaotic system is intrinsically unpredictable"". © Springer 2005."
"7006934305;57206526404;57211105491;7006589757;6602641633;35574839400;","Detection of mesoscale seasonal and interannual variation in the vegetation of the Amazon Basin",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-77249175351&partnerID=40&md5=0ab63a195c8e70590448ea657f9a175b","In the Amazon basin, seasonal and interannual spectral changes measured by satellites result from anthropogenic disturbance and from the interaction between climate variation and the surface cover. Measurements of spectral change, and the characterization of that change, provide information concerning the physical processes evident at this mesoscale. A 17-yr sequence of daily Advanced Very High Resolution Radiometer (AVHRR) global area coverage (GAC) images were analyzed to produce a monthly record of surface spectral change encompassing El Niño-Southern Oscillation (ENSO) cycles. Monthly cloud-free composite images from daily AVHRR data were produced by linear filters that minimized the finescale spatial variance and allowed for a wide range analysis within a consistent mathematical framework. Here the use of a minimized local variance (MLV) filter that produced spatially smooth images in which major land-cover boundaries and spatial gradients are clearly represented is discussed. Changes in the configuration of these boundaries and the composition of the landscape elements they defined are described in terms of quantitative changes in landscape pattern. The time series produced with the MLV filter revealed a marked seasonal difference in the pattern of the landscape and structural differences over the length of the time series. Strikingly, the response of the region to drier El Niño years appears to be delayed in the MLV series, the maximum response being in the year following El Niño with little or no change seen during El Niño."
"9271448600;55388515800;55511340100;","Spatial structure and scale feature of the atmospheric pollution source impact of city agglomeration",2005,"10.1360/03YD0125","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845917355&doi=10.1360%2f03YD0125&partnerID=40&md5=b2017394a6cdcdbe022b653400791c22","The spatial structure and multi-scale feature of the atmospheric pollution influence domain of Beijing and its peripheral areas (a rapidly developed city agglomeration) is dissected and analyzed in this paper on the basis of the atmospheric pollution dynamic-chemical process observation data of the urban building ensemble boundary layer of the Beijing City Air Pollution Observation Experiment (BECAPEX) in winter (February) and summer (August) 2003, and relevant meteorological elements and satellite retrieval aerosol optical depth (AOD), etc. comprehensive data with the dynamic-statistical integrated analysis of ""point-surface"" spatial structure. Results show that there existed significant difference in the contribution of winter/summer different pollution emission sources to the component character of atmospheric pollution, and the principal component analysis (PCA) results of statistical model also indicate that SO2 and NOx dominated in the component structure of winter aerosol particle; instead, CO and NOxdominated in summer. Surface layer atmospheric dynamic and thermal structures and various pollutant species at the upper boundary of building ensembles at urban different observational sites of Beijing in winter and summer showed an ""in-phase"" variation and its spatial scale feature of ""influence domain"". The power spectrum analysis (PSA) shows that the period spectrum of winter/summer particle concentration accorded with those of atmospheric wind field: the longer period was dominative in winter, but the shorter period in summer, revealing the impact of the seasonal scale feature of winter/summer atmospheric general circulation on the period of atmospheric pollution variations. It is found that from analyzing urban area thermal heterogeneity that the multi-scale effect of Beijing region urban heat island (UHI) was associated with the heterogeneous expansion of tall buildings area. In urban atmospheric dynamical and thermal characteristic spatial structures, the turbulent scale feature of the urban boundary layer (UBL) of architectural complexes had important impact on the multi-scale feature of urban atmospheric pollution. The comprehensive analyses of the variational analysis field of Moderate Resolution Imaging Spectroradiometer (MODIS) AOD-surface PM 10 under the condition of clear sky and the correlation resultant wind vector field for pollution source-tracing suggest that the emission sources for winter Beijing atmospheric pollution aerosols particle might be remotely traced to the south peripheral greater-scale spatial range of Hebei, Shandong, Tianjin, etc., and the spatial distribution of the high value area of AOD was associated with that of the high value area of resident family number (heating surface source). The backward trajectory feature of winter/ summer air particles exhibits analogous multi-scale feature, and depicts the difference in the scale feature of the pollution sources spatial distribution in different seasons. The peripheral source trajectory paths of urban atmospheric pollution (UAP) mainly come from the fixed industrial surface source or heating surface source in the outskirt of Beijing, and the diffusion and transport distance of peripheral sources in winter is larger than one in summer. The above conclusions depict the multi-scale spatial influence domain and seasonal features caused by UAP source influence and atmospheric dynamical structure. The high value area of the winter Total Ozone Mapping Spectrometer (TOMS) AOD lay in the Beijing region and its south peripheral area, an S-N zonal pattern, which reflects the dynamical effect of peripheral topographic pattern on the diffusion of regional scale atmospheric pollution sources. Study suggests that the extent of winter atmospheric pollution within the ""valley"" megarelief in Beijing and periphery was close related with the pollution emission sources of the south peripheral area; and the significant ""anti-phase"" variation feature of winter AOD and sunshine duration in Beijing and its peripheral areas, and the regional scale correlation of low cloud cover, fog days, and aerosols reflects the local climatic effect of aerosol influence in this region. Besides, analysis of the impacts of atmospheric dry/wet deposition distributions within a valley-scale on the regional water body of Miyun reservoir also reveals the possible influence of the multi-scale spatial structure of summer water, soil and atmospheric pollution sources on the water quality of Miyun reservoir. Copyright by Science in China Press 2005."
"56203249800;7201837768;","Varying trends in surface energy fluxes and associated climate between 1960 and 2002 based on transient climate simulations",2005,"10.1029/2005GL024089","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30744452706&doi=10.1029%2f2005GL024089&partnerID=40&md5=5570c5741037d67465c40628e532bb55","The observed reduction in land surface radiation over the last several decades (1960-1990), the so-called ""dimming effect,"" and the more recent evidence of a reversal in ""dimming"" over some locations beyond 1990 suggest several consequences on climate, notably on the hydrological cycle. Such a reduction in radiation should imply reduced surface temperature (Ts) and precipitation, which have not occurred. We have investigated the possible causes for the above climate features using a climate model coupled to a dynamic ocean model under natural and anthropogenic conditions. To isolate the aerosol influence on surface radiation trends, we have analyzed transient climate simulations from 1960 to 2002 with and without anthropogenic aerosols. Based on a linear trend with aerosol effects included, the global mean change in the surface solar radiation absorbed over land is -0.021 ± 0.0033 Wm-2yr-1. Although the overall trend is negative, we do note a reversal in dimming after 1990, consistent with observations. Without aerosol effects, the surface solar radiation absorbed over land increases throughout 1960 to 2002, mainly due to the decrease in cloud cover associated with increased greenhouse warming. In spite of a simulated increase in Ts of 0.012 K yr-1 for 1960 to 2002, the global mean latent heat flux and associated intensity of the hydrological cycle decrease overall, however with increases over some land locations due mainly to moisture advection. Simulated changes correspond more closely to observed changes when accounting for aerosol effects on climate. Copyright 2005 by the American Geophysical Union."
"56157800800;8329897000;11440352500;","Late 20th century attribution of drying trends in the Sahel from the Regional Climate Model (RegCM3)",2005,"10.1029/2005GL024225","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30744465906&doi=10.1029%2f2005GL024225&partnerID=40&md5=f3a9f4b64a35fc41799aae918a3da197","The RegCM3 has been integrated for the period of 1960-2002 using initial and lateral boundary conditions from the NCEP re-analyses at 6-hour intervals. Greenhouse gas concentrations remain fixed and the land-use/ soil properties are not altered. The RegCM3 accurately portrays a trend from wetter conditions in the 1960s to very dry conditions in the 1980s. The dry 1980s temperatures in the Sahel are approximately 3°K warmer than the wet 1960s, caused by a reduction in precipitation and clouds leading to an increase in the net absorbed solar radiation at the surface. This anomalous warming maintains the steepest meridional temperature gradient and therefore the African Easterly Jet in lower latitudes. The initiation of dry conditions starts in June and persists through July and August in the model simulations. The initiation of dry conditions appears to be related to a weaker Tropical Easterly Jet which may be linked to warmer Indian Ocean temperatures over the past several decades. Copyright 2005 by the American Geophysical Union."
"7004540083;6603422104;10242482700;7006698304;","Tropical climate described as a distribution of weather states indicated by distinct mesoscale cloud property mixtures",2005,"10.1029/2005GL024584","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29344471030&doi=10.1029%2f2005GL024584&partnerID=40&md5=7dd1b0d959adeb389f554bf2f96c18f4","An analysis approach that uses the patterns of cloud property joint distributions at mesoscale (cloud type mixtures) from the International Satellite Cloud Climatology Project to identify distinct weather states of the tropical atmosphere is extended to the whole tropics covering the period 1983-2004. These patterns can be used as the basis for multi-scale, multi-variate compositing of other observations to understand how tropical cloud systems affect the atmospheric diabatic heating and interact with the large scale circulation. We illustrate how variations of the tropical climate on longer time scales can be described in terms of the changes in the frequency of occurrence of these weather states with their associated multivariate relationships. Copyright 2005 by the American Geophysical Union."
"10241462700;8979277400;10240710000;7007021059;10243650000;7102857642;","Climate response to volcanic forcing: Validation of climate sensitivity of a coupled atmosphere-ocean general circulation model",2005,"10.1029/2005GL023542","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144436452&doi=10.1029%2f2005GL023542&partnerID=40&md5=5161f9c9c04118e7c1d9d56ab872aa79","Two versions of a coupled atmosphere-ocean general circulation model (GCM) with different climate sensitivities are tested on global cooling following the Pinatubo volcanic eruption to investigate the validity of high climate sensitivities. The higher-sensitivity version, with climate sensitivity of 6.3 K for doubled CO2 forcing, overestimates cooling due to the volcanic eruption, whereas the lower-sensitivity version (4.0 K) produces results consistent with observations. A simple scheme for climate feedback analysis is devised and it is found that the difference between the two versions is attributed to cloud-albedo feedback. This validation method is expected to provide additional constraints on climate sensitivity and possibly lead to reduced uncertainties in climate prediction. Copyright 2005 by the American Geophysical Union."
"55887849100;55887389300;22982762300;24546705400;7102953444;56151984200;","A multi-data comparison of shortwave climate forcing changes",2005,"10.1029/2005GL023847","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29344434467&doi=10.1029%2f2005GL023847&partnerID=40&md5=d65fe10a36ab7ba0c405563d712f64bd","Traditionally the Earth's reflectance has been assumed to be roughly constant, but large decadal variability, not reproduced by current climate models, has been reported lately from a variety of sources. We compare here the available data sets related to Earth's reflectance, in order to assess the observational constraints on the models. We find a consistent picture among all data sets of an albedo decreased during 1985-2000 between 2-3 and 6-7 W/m2, which is highly climatically significant. The largest discrepancy among the data sets occurs during 2000-2004, when some present an increasing reflectance trend, while CERES observations show a steady decrease of about 2 W/m2. Copyright 2005 by the American Geophysical Union."
"7401776640;","Trends in upper-level cloud cover and surface divergence over the tropical Indo-Pacific Ocean between 1952 and 1997",2005,"10.1029/2005JD006183","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29244461457&doi=10.1029%2f2005JD006183&partnerID=40&md5=98536d99dbfb86eec12aab20198b8cf5","This study investigates the spatial pattern of linear trends in surface-observed upper-level combined midlevel and high-level) cloud cover, precipitation, and surface divergence over the tropical Indo-Pacific Ocean during 1952-1997. Cloud values were obtained from the Extended Edited Cloud Report Archive (EECRA), precipitation values were obtained from the Hulme/Climate Research Unit data set, and surface divergence was alternatively calculated from wind reported by Comprehensive Ocean-Atmosphere Data Set and from wind derived from Smith and Reynolds Extended Reconstructed sea level pressure data. Between 1952 and 1997, upper-level cloud cover increased by about 4%-sky-cover over the central equatorial South Pacific and decreased by about 4-6%-sky-cover over the adjacent subtropics, the western Pacific, and the equatorial Indian Ocean. Trends in precipitation and surface convergence are usually positive where upper-level cover trends are positive and negative where they are negative. Consistency between time series of upper-level cloud cover reported by EECRA and the International Satellite Cloud Climatology Project (ISCCP) during 1984-1997 for various subregions provides further confirmation that the surface-observed upper cloud trends are real. Estimated radiative effects of surface-observed cloud cover anomalies are also well correlated with all-sky radiation flux anomalies reported by the Earth Radiation Budget Satellite in most areas. Contrastingly, EECRA and ISCCP low-level cloud cover regional time series exhibit little correspondence, and EECRA low-level cloud cover trends are uniformly positive across the tropical Indo-Pacific with no apparent relationship to changes in surface divergence, Although the spatial pattern of upper-level cloud trends resembles that associated with El Niño, the trends are approximately three times larger than those predicted by a linear relationship to sea surface temperature in the Niño 3.4 region. Copyright 2005 by the American Geophysical Union."
"7004714030;6602600408;57203200427;10243911900;6602886421;","Contrasts in the effects on climate of anthropogenic sulfate aerosols between the 20th and the 21st century",2005,"10.1029/2005GL023619","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29344448024&doi=10.1029%2f2005GL023619&partnerID=40&md5=900499cd82dde777450595a66577f7e1","In this study, we examine the time evolution of the relative contribution of sulfate aerosols and greenhouse gases to anthropogenic climate change. We use the new IPSL-CM4 coupled climate model for which the first indirect effect of sulfate aerosols has been calibrated using POLDER satellite data. For the recent historical period the sulfate aerosols play a key role on the temperature increase with a cooling effect of 0.5 K, to be compared to the 1.4 K warming due to greenhouse gas increase. In contrast, the projected temperature change for the 21st century is remarkably independent of the effects of anthropogenic sulfate aerosols for the SRES-A2 scenario. Those results are interpreted comparing the different radiative forcings, and can be extended to other scenarios. We also highlight that the first indirect effect of aerosol strongly depends on the land surface model by changing the cloud cover. Copyright 2005 by the American Geophysical Union."
"8068314800;26643408200;7006783796;7004174939;","Comparison and analysis of two aerosol retrievals over the ocean in the Terra/Clouds and the Earth's Radiant Energy System-Moderate Resolution Imaging Spectroradiometer single scanner footprint data: 1. Global evaluation",2005,"10.1029/2005JD005851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29244460671&doi=10.1029%2f2005JD005851&partnerID=40&md5=d1dbd8fd0075afb9df59bf77cf22dc82","Satellite aerosol remote sensing entered a new era with the deployment of advanced satellite imaging instruments such as the Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Terra and Aqua satellites. These new instruments provide the opportunity to learn more about aerosol properties than was possible using the simpler NOAA Advanced Very High Resolution Radiometer (AVHRR), which has been used to retrieve aerosol optical thickness for more than 20 years. Combining historical AVHRR and the more advanced MODIS aerosol retrievals to form a long-term aerosol data record is critical for studying aerosol climate forcing. To achieve this objective, it is necessary to build a connection and establish consistency between the two retrievals through a careful evaluation of the two retrieval methods applied to the same data. As a first step in this effort, this paper exploits the potential of the Clouds and the Earth's Radiant Energy System'(CERES) Single-Scanner Footprint (SSF) data set that includes aerosol products derived from Terra MODIS data at the same locations using both the multichannel MODIS and the two-channel AVHRR aerosol retrieval algorithms. The analysis examines the differences in the results seen over oceans on a global scale. It was found in a global mean sense. that advancement in the aerosol retrieval over ocean from the MODIS algorithm relative to the AVHRR method is realized mostly in the improvement of the aerosol size parameter (ASP) rather than in the aerosol optical thickness (AOT). However, regional differences were observed in both AOT and ASP retrieved from the MODIS and AVHRR algorithms. These are examined further in the second part of this two-part paper. Cloud contamination and surface roughness appear to affect both aerosol retrievals, effects that need further investigation. Copyright 2005 by the American Geophysical Union."
"56604618200;7003786872;34979232000;7201695641;55461837700;","Four decades of ozonesonde measurements over Antarctica",2005,"10.1029/2005JD005971","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29244488276&doi=10.1029%2f2005JD005971&partnerID=40&md5=22d092061eee5d11fa553e6bd669e6d3","Ozonesonde observations from Syowa and the South Pole over more than 40 years are described and intercompared. Observations from the two sites reveal remarkable agreement, supporting and extending the understanding gained from either individually. Both sites exhibit extensive Antarctic ozone losses in a relatively narrow altitude range from about 12 to 24 km in October, and the data are consistent with temperature-dependent chemistry involving chlorine on polar stratospheric clouds as the cause of the ozone hole. The maximum October ozone losses at higher altitudes near 18 km (70 hPa) appear to be transported to lower levels near the tropopause on a timescale of a few months, which is likely to affect the timing of the effects of ozone depletion on possible tropospheric climate changes. Both sites also show greater ozone losses in the lowermost stratosphere after the volcanic eruption of Mt. Pinatubo, supporting the view that surface chemistry can be enhanced by volcanic perturbations and that the very deep ozone holes observed in the early 1990s reflected such enhancements. Sparse data from the Syowa station in the early 1980s also suggest that enhanced ozone losses due to the El Chichon eruption may have contributed to the beginning of a measurable ozone hole. Observations at both locations show that some ozone depletion now occurs during much if not all year at lower altitudes near 12-14 km. Correlations between temperature and ozone provide new insights into ozone losses, including its nonlinear character, maximum effectiveness, and utility as a tool to distinguish dynamical effects from chemical processes. These data also show that recent changes in ozone do not yet indicate ozone recovery linked to changing chlorine abundances but provide new tools to probe observations for the first such future signals. Copyright 2005 by the American Geophysical Union."
"55899884100;7401436524;7402989545;56962915800;","Why is there an early spring colling shift downstream of the Tibetan Plateau?",2005,"10.1175/JCLI3568.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30144445942&doi=10.1175%2fJCLI3568.1&partnerID=40&md5=46fe85d6902c11a30e8cdc0c1ea54433","The temperature shift over the eastern flank of the Tibetan Plateau is examined using the last 50 yr of Chinese surface station observations. It was found that a strong cooling shift occurs in early spring (March and April) and late summer (July, August, and September) in contrast to the warming shift in other seasons. The cause of the March-April (MA) cooling is investigated in this study. The MA cooling shift on the lee side of the Tibetan Plateau is found to be not a local phenomenon, but rather it is associated with an eastward extension of a cooling signal originating from North Africa that is related to the North Atlantic Oscillation (NAO) in the previous winter. The midtropospheric westerlies over the North Atlantic and North Africa tend to intensify during positive NAO phases. The enhanced westerlies, after passing over the Tibetan Plateau, result in strengthened ascending motion against the lee side of the plateau, which favors the formation of midlevel stratiform clouds. The increased amount of stratus clouds induces a negative net cloud-radiative forcing, which thereby cools the surface air and triggers a positive cloud-temperature feedback. In this way, the cooling signal from the upstream could ""jump"" over the Tibetan Plateau and leave a footprint on its lee side. The continental stratiform cloud-climate feedback plays a significant role in the amplification of the cooling shift downstream of the Tibetan Plateau. © 2005 American Meteorological Society."
"7401776640;6603568514;","North Pacific cloud feedbacks inferred from synoptic-scale dynamic and thermodynamic relationships",2005,"10.1175/JCLI3558.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30144434489&doi=10.1175%2fJCLI3558.1&partnerID=40&md5=524b4251a6e7c9c835a6c968899d4de5","Daily satellite cloud observations and reanalysis dynamical parameters are analyzed to determine how midtropospheric vertical velocity and advection over the sea surface temperature gradient control midlatitude North Pacific cloud properties. Optically thick clouds with high tops are generated by synoptic ascent, but two different cloud regimes occur under synoptic descent. When vertical motion is downward during summer, extensive stratocumulus cloudiness is associated with near-surface northerly wind, while frequent cloudless pixels occur with southerly wind. Examination of ship-reported cloud types indicates that midlatitude stratocumulus breaks up as the boundary layer decouples when it is advected equatorward over warmer water. Cumulus is prevalent under conditions of synoptic descent and cold advection during winter. Poleward advection of subtropical air over colder water causes stratification of the near-surface layer that inhibits upward mixing of moisture and suppresses cloudiness until a fog eventually forms. Averaging of cloud and radiation data into intervals of 500-hPa vertical velocity and advection over the SST gradient enables the cloud response to changes in temperature and the stratification of the lower troposphere to be investigated independent of the dynamics. Vertically uniform warming results in decreased cloud amount and optical thickness over a large range of dynamical conditions. Further calculations indicate that a decrease in the variance of vertical velocity would lead to a small decrease in mean cloud optical thickness and cloud-top height. These results suggest that reflection of solar radiation back to space by midlatitude oceanic clouds will decrease as a direct response to global warming, thus producing an overall positive feedback on the climate system. An additional decrease in solar reflection would occur were the storm track also to weaken, whereas an intensification of the storm track would partially cancel the cloud response to warming. © 2005 American Meteorological Society."
"26427916400;7409080503;","A near-global climatology of single-layer and overlapped clouds and their optical properties retrieved from Terra/MODIS data using a new algorithm",2005,"10.1175/JCLI3553.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28844456826&doi=10.1175%2fJCLI3553.1&partnerID=40&md5=678720414974e066de21d10691fa4e4b","Cloud overlapping has been a major issue in climate studies owing to a lack of reliable information available over both oceans and land. This study presents the first near-global retrieval and analysis of single-layer and overlapped cloud vertical structures and their optical properties retrieved by applying a new method to the Moderate Resolution Imaging Spectroradiometer (MODIS) data. Taking full advantage of the MODIS multiple channels, the method can differentiate cirrus overlapping lower water clouds from single-layer clouds. Based on newly retrieved cloud products using daytime Terra/MODIS 5-km overcast measurements sampled in January, April, July, and October 2001, global statistics of the frequency of occurrence, cloud-top pressure/temperature (Pc/Tc), visible optical depth (τVIs), and infrared emissivity (ε) are presented and discussed. Of all overcast scenes identified over land (ocean), the MODIS data show 61% (52%) high clouds (Pc &lt; 500 hPa), 39% (48%) lower clouds (Pc &gt; 500 hPa), and an extremely low occurrence (&lt;4%) of Pc between 500 and 600 hPa. A distinct bimodal distribution of Pc is found and peaks at ∼275 and ∼725 hPa for high and low clouds, thus leaving a minimum in cloud in the middle troposphere. Out of the 61% (52%) of high clouds identified by MODIS, retrievals reveal that 41% (35%) are thin cirrus clouds (ε &lt; 0.85 and Pc &lt; 500 hPa) and the remaining 20% (17%) are thick high clouds (ε ≥ 0.85). Out of the 41% (35%) of thin cirrus, 29% (27%) are found to overlap with lower water clouds and 12% (8%) are single-layer cirrus. Total low-cloud amount (single-layer plus overlapped) out of all overcast scenes is thus 68% (39% + 29%) over land and 75% (48% + 27%) over ocean, which is greater than the cloud amounts reported by the MODIS and the International Satellite Cloud Climatology Project (ISCCP). Both retrieved overlapping and nonoverlapping cirrus clouds show similar mean τVIS of ∼1.5 and mean ε of ∼0.5. The optical properties of single-layer cirrus and single-layer water clouds agree well with the MODIS standard retrievals. Because the MODIS retrievals do not differentiate between cirrus and lower water clouds in overlap situations, large discrepancies are found for emissivity, cloud-top height, and optical depth for high cirrus overlapping lower water clouds. © 2005 American Meteorological Society."
"7402933297;7405584618;7004160106;7402390191;","Effects of cloud microphysics on tropical atmospheric hydrologic processes and intraseasonal variability",2005,"10.1175/JCLI3561.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30144444974&doi=10.1175%2fJCLI3561.1&partnerID=40&md5=fbed61aacf07059ab4d54748d6c85863","The sensitivity of tropical atmospheric hydrologic processes to cloud microphysics is investigated using NASA Goddard Earth Observing System (GEOS) general circulation model (GCM). Results show that a faster autoconversion rate leads to (a) enhanced deep convection in the climatological convective zones anchored to tropical land regions; (b) more warm rain, but less cloud over oceanic regions; and (c) an increased convective-to-stratiform rain ratio over the entire Tropics. Fewer clouds enhance longwave cooling and reduce shortwave heating in the upper troposphere, while more warm rain produces more condensation heating in the lower troposphere. This vertical differential heating destabilizes the tropical atmosphere, producing a positive feedback resulting in more rain and an enhanced atmospheric water cycle over the Tropics. The feedback is maintained via secondary circulations between convective tower and anvil regions (cold rain), and adjacent middle-to-low cloud (warm rain) regions. The lower cell is capped by horizontal divergence and maximum cloud detrainment near the freezing-melting (0°C) level, with rising motion (relative to the vertical mean) in the warm rain region connected to sinking motion in the cold rain region. The upper cell is found above the 0°C level, with induced subsidence in the warm rain and dry regions, coupled to forced ascent in the deep convection region. It is that warm rain plays an important role in regulating the time scales of convective cycles, and in altering the tropical large-scale circulation through radiative-dynamic interactions. Reduced cloud-radiation feedback due to a faster autoconversion rate results in intermittent but more energetic eastward propagating Madden-Julian oscillations (MJOs). Conversely, a slower autoconversion rate, with increased cloud radiation produces MJOs with more realistic westward-propagating transients embedded in eastward-propagating supercloud clusters. The implications of the present results on climate change and water cycle dynamics research are discussed. © 2005 American Meteorological Society."
"7406671641;57202891769;36991619500;36166130900;8321853700;","Rethinking tropical ocean response to global warming: The enhanced equatorial warming",2005,"10.1175/JCLI3579.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30144437350&doi=10.1175%2fJCLI3579.1&partnerID=40&md5=54ce6e5658bb829e2c5027a82394101f","The response of tropical Pacific SST to increased atmospheric CO2 concentration is reexamined with a new focus on the latitudinal SST gradient. Available evidence, mainly from climate models, suggests that an important tropical SST fingerprint to global warming is an enhanced equatorial warming relative to the subtropics. This enhanced equatorial warming provides a fingerprint of SST response more robust than the traditionally studied El Niño-like response, which is characterized by the zonal SST gradient. Most importantly, the mechanism of the enhanced equatorial warming differs fundamentally from the El Niño-like response; the former is associated with surface latent heat flux, shortwave cloud forcing, and surface ocean mixing, while the latter is associated with equatorial ocean upwelling and wind-upwelling dynamic ocean-atmosphere feedback. © 2005 American Meteorological Society."
"6701511324;25941200000;8397494800;","The Monte Carlo Independent Column Approximation's conditional random noise: Impact on simulated climate",2005,"10.1175/JCLI3556.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30144441543&doi=10.1175%2fJCLI3556.1&partnerID=40&md5=fbbf739522a72ce7ba832e8d06e02ab4","The Monte Carlo Independent Collumn Approximation (McIca) method for computing domain-average radiative fluxes is unbiased with resopect to the full ICA, but its flux estimates contain conditional random noise. Results for five experiments are used to asses the impact of McICA-related noise on simulation of global climate made by NCAR Community Atmosphere Model (CAM). The experiment with the least noise (an order of magnitude below that of basic McICA) is taken as the reference. Two additional experiments help demonstrated how the impact of noise depends on the time interval between calls to the radiation code. Each experiment is an ensemble of seven 15-month simulations. Experiment with very high noise levels feature significane reductions of cloudiness in the lowermost model layer over tropical oceans as well as changes in highly related quantities. This bias appears immediately, stabilizes after a couple of models days and appears to stem from non linear interactions between clouds and radiative heating. Outside the Tropics, insignificant differences prevail. When McICA sampling is confined to cloudy subcollums and when, on average, 50% more samples relative to basic McICA, are drawn for selected spectrals intervals, McICA noise is much reduced and the results of the simulation are almost statistically indistinguishable from the reference. This is true both for main fields and for the nature of fluctuations on scales ranging from 1 day to at least 30 days. While calling the radiation code every 3 h instead of every hour allows the CAM additional time to incorporate McICA-related noise, the impact of noise is enhanced only slightly. In contrast, changing the radiative time step by itself produces effects that generally exceed the impact of McICA' noise. © 2005 American Meteorological Society."
"7005354212;6506942596;55465604600;6603631763;14014252200;6603025800;7201607592;","Automated cloud detection and classification of data collected by the Visible Infrared Imager Radiometer Suite (VIIRS)",2005,"10.1080/01431160500196786","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745086956&doi=10.1080%2f01431160500196786&partnerID=40&md5=d325961fef0022ee4707486e60a34d33","The Visible Infrared Imager Radiometer Suite (VIIRS) is a high-resolution Earth imager of the United States National Polar-orbiting Operational Environmental Satellite System (NPOESS). VIIRS has its heritage in three sensors currently collecting imagery of the Earth - the Advanced Very High Resolution Radiometer, the Moderate Resolution Imaging Spectroradiometer, and the Operational Linescan Sensor. The first launch of the VIIRS sensor is on NASA's NPOESS Preparatory Project (NPP). Data collected by VIIRS will provide products to a variety of users, supporting applications from real-time to long-term climate change timescales. VIIRS has been uniquely designed to satisfy this full range of requirements. Cloud masks derived from the automated analyses of VIIRS data are critical data products for the NPOESS program. In this paper, the VIIRS cloud mask (VCM) performance requirements are highlighted, along with the algorithm developed to satisfy these requirements. The expected performance of the VCM algorithm is established using global synthetic cloud simulations and manual cloud analyses of VIIRS proxy imagery. These results show the VCM analyses will satisfy the performance expectations of products created from it, including land and ocean surface products, cloud microphysical products, and automated cloud forecast products. Finally, minor deficiencies that remain in the VCM algorithm logic are identified along with a mitigation plan to resolve each prior to NPP launch or shortly thereafter. © 2005 Taylor & Francis."
"57197516460;","Remarkable surface synoptic maps from the 1930s",2005,"10.1175/BAMS-86-11-1603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144458483&doi=10.1175%2fBAMS-86-11-1603&partnerID=40&md5=2cb602f82ba40f33a7785def1c179e8f","A set of high-resolution maps depicting the temperature, wind, cloud, and precipitation (2.5 previous hours) have been digitized and reproduced for 1500 LT 12 October 1937 for an area in eastern Ohio. These are only one time sample of map sequences that exist. They are an almost unmined source for research into mesoscale surface weather changes and associated hydrologic phenomena. © 2005 American Meteorological Society."
"9336087000;7405460591;7102142846;","Three-dimensional nonhydrostatic simulations of summer thunderstorms in the humid subtropics versus High Plains",2005,"10.1016/j.atmosres.2005.03.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27944471390&doi=10.1016%2fj.atmosres.2005.03.005&partnerID=40&md5=12439c58c10a8c00a8b3c8ebd6b519cb","This article presents a detailed comparison of cloud microphysical evolution among six warm-season thunderstorm simulations using a time-dependent three-dimensional model WISCDYMM. The six thunderstorms chosen for this study consist of three apiece from two contrasting climate zones, the US High Plains (one supercell and two multicells) and the humid subtropics (two in Florida, US and one in Taipei, Taiwan, all multicells). The primary goal of this study is to investigate the differences among thunderstorms in different climate regimes in terms of their microphysical structures and how differently these structures evolve in time. A subtropical case is used as an example to illustrate the general contents of a simulated storm, and two examples of the simulated storms, one humid subtropical and one northern High Plains case, are used to describe in detail the microphysical histories. The simulation results are compared with the available observational data, and the agreement between the two is shown to be at least fairly close overall. The analysis, synthesis and implications of the simulation results are then presented. The microphysical histories of the six simulated storms in terms of the domain-integrated masses of all five hydrometeor classes (cloud water, cloud ice, rain, snow, graupel/hail), along with the individual sources (and sinks) of the three precipitating hydrometeor classes (rain, snow, graupel/hail) are analyzed in detail. These analyses encompass both the absolute magnitudes and their percentage contributions to the totals, for the condensate mass and their precipitation production (and depletion) rates, respectively. Comparisons between the hydrometeor mass partitionings for the High Plains versus subtropical thunderstorms show that, in a time-averaged sense, ice hydrometeors (cloud ice, snow, graupel/hail) account for μ 70-80% of the total hydrometeor mass for the High Plains storms but only μ 50% for the subtropical storms, after the systems have reached quasi-steady mature states. This demonstrates that ice processes are highly important even in thunderstorms occurring in warm climatic regimes. The dominant rain sources are two of the graupel/hail sinks, shedding and melting, in both High Plains and subtropical storms, while the main rain sinks are accretion by hail and evaporation. The dominant graupel/hail sources are accretion of rain, snow and cloud water, while its main sinks are shedding and melting. The dominant snow sources are the Bergeron-Findeisen process and accretion of cloud water, while the main sinks are accretion by graupel/hail and sublimation. However, the rankings of the leading production and depletion mechanisms differ somewhat in different storm cases, especially for graupel/hail. The model results indicate that the same hydrometeor types in the different climates have their favored microphysical sources and sinks. These findings not only prove that thunderstorm structure depends on local dynamic and thermodynamic atmospheric conditions that are generally climate-dependent, but also provide information about the partitioning of hydrometeors in the storms. Such information is potentially useful for convective parameterization in large-scale models. © 2005 Elsevier B.V. All rights reserved."
"7005725199;","Secular oscillations in the stratigraphic record - An acute debate",2005,"10.1007/s10347-005-0066-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29944442212&doi=10.1007%2fs10347-005-0066-5&partnerID=40&md5=9da92f43f6c1ee8ce875fbe743534e23","Work on secular oscillations of the ocean-atmosphere system has reached a particularly interesting stage, characterized by competing models that alternately invoke endogenic and celestial drivers. The most widely accepted concept is the icehouse-greenhouse cycle with an approximate length of 300 Ma. The concept holds that in the past 600 Ma the Earth has oscillated between a glacial mode and one of rather warm, equable climate; correlative changes in mineralogy of marine carbonates and evaporites as well as abundance of igneous intrusions point to an endogenic cause, most probably variations in the rates of plate motion and mantle convection that modulate sea level and the level of atmospheric CO2 and thus climate. However, the 300-Ma icehouse-greenhouse cycle leaves important data unexplained. The history of glaciations as well as certain climate indicators, such as sea-surface temperatures derived from oxygen isotopes, indicate oscillations with wave lengths of 130-150 Ma. Such oscillations have been observed in the reconstructed cosmic-ray flux of the past 1000 Ma; they may modulate climate via low-level cloud cover. The debate about long-term climate oscillations poses several distinct questions for sedimentary geologists. © Springer-Verlag 2005."
"7003279098;7103386012;6603577900;7007107813;","The simulated response of dimethylsulfide production in the Arctic Ocean to global warming",2005,"10.1111/j.1600-0889.2005.00163.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28244461522&doi=10.1111%2fj.1600-0889.2005.00163.x&partnerID=40&md5=543887f1c51a6ed92787902b1da77496","Sulfate aerosols (of both biogenic and anthropogenic origin) play a key role in the Earth's radiation balance both directly through scattering and absorption of solar and terrestrial radiation, and indirectly by modifying cloud microphysical properties. However, the uncertainties associated with radiative forcing of climate due to aerosols substantially exceed those associated with the greenhouse gases. The major source of sulfate aerosols in the remote marine atmosphere is the biogenic compound dimethylsulflde (DMS), which is ubiquitous in the world's oceans and is synthesized by plankton. Climate models point to significant future changes in sea-ice cover in the Arctic Ocean due to warming. This will have consequences for primary production and the sea-to-air flux of a number of biogenic compounds, including DMS. In this paper we discuss the impact of warming on the future production of DMS in the Arctic Ocean. A DMS production model has been calibrated to current climate conditions with satellite ocean colour data (SeaWiFS) using a genetic algorithm, an efficient non-derivative based optimization technique. We use the CSIRO Mk 2 climate model to force the DMS model under enhanced greenhouse climate conditions. We discuss the simulated change in DMS flux and its consequences for future aerosol production and the radiative budget of the Arctic. Significant decreases in sea-ice cover (by 18.5% annually and 61% in summer-autumn), increases in mean annual sea surface temperature of 1°C, and a decrease of mixed layer depth by 13% annually are predicted to result in annual DMS flux increases of over 80% by the time of equivalent CO2 tripling (2080). Estimates of the impact of this increase in DMS emissions suggest significant changes to summer aerosol concentrations and the radiative balance in the Arctic region. Copyright © Blackwell Munksgaard, 2005."
"55628565151;","Cosmogenic ion production rate in the high-middle-low altitude troposphere and its influence on the terrestrial cloud properties",2005,"10.1016/j.jastp.2005.09.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28544432567&doi=10.1016%2fj.jastp.2005.09.004&partnerID=40&md5=063850d4c1c714eeeff04c8d2d2bced6","Cosmic-ray-induced ion production rate in the atmosphere is important to evaluate the influence of the galactic cosmic ray (GCR) modulations on cloud properties, which control the global climate on the Earth. An air shower Monte Carlo simulation was carried out to estimate the amount of cosmic-ray-produced low-energy electrons (δ-ray) at the high-middle-low troposphere. At low altitudes, energetic knock-on electrons by gamma rays, muons, and electrons/positrons produced by a muon decay process contribute to the total amount of electrons, whereas cascade generations initiated by neutral pions play a big role at higher altitudes. The total ion production rate was estimated by considering δ-ray production, initiated by gamma rays, low-energy electrons, knock-on electrons, muons, and muon-decay positrons. Other charged components such as protons rapidly decrease with atmospheric depth, and thus they cannot produce many ion pairs at low altitudes. Calculated ion production rates within the atmospheric depth intervals d=50-100 g cm-2, 350-400 g cm-2, and 650-700 g cm-2 were n = 13.72, 7.88, and 2.41 s-1 cm-3, respectively. Our simulation indicates that the high-energy component of the primaries controls the ion production rate at low altitudes. We found that very high-energy GCRs play an important role in the ion production rate at low altitudes. These results are consistent with the previously reported values (∼2 ion pairs s-1 cm-3 at ground level and up to ∼20-30 ion pairs s-1 cm-3 in the upper troposphere). Based on the simulation results, we estimated the influence of GCR modulation on the ion production rate during the last 11-year solar cycle. The estimated variation in the nucleation rate was ∼1.0% between the solar maximum and minimum. The simulation result may explain the observed variation of low clouds by ∼1.7%. We also discussed other possibilities to change the cosmic-ray intensity, including the galactic spiral arm crossings. We propose a possible method to find evidence of the correlation between cosmic-ray intensity and the climate change in the past by comparing cosmogenic radionuclides recorded in the seafloor to that in the glacial layer. © 2005 Elsevier Ltd. All rights reserved."
"7006432537;8872947700;","Temperature trends in twentieth century at Pune, India",2005,"10.1016/j.atmosenv.2005.07.032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26444450531&doi=10.1016%2fj.atmosenv.2005.07.032&partnerID=40&md5=d5a32a3d29c80b889ea0f61ee402f5a5","Climatic change is one of the most important issues of present times. Unlike the greenhouse gases, which have a predominantly warming effect, atmospheric aerosols could either warm or cool the atmosphere depending upon the size, distribution and optical properties. Of all the climatic elements, temperature plays a major role in detecting climatic change brought about by urbanization and industrialization. This paper, therefore, attempts to study temporal variation in temperature over Pune city, India, during the period 1901-2000. The long-term change in temperature has been evaluated by Mann-Kendall rank statistics and linear trend. The analysis reveals significant decrease in mean annual and mean maximum temperature. This decrease in temperature is more pronounced during the winter season, which can be ascribed to a significant increase in the amount of suspended particulate matter (SPM) in the ambient air during the last decade. On the contrary, monsoon season shows warming. This warming can be attributed to a significant increase in the low cloud amount. © 2005 Elsevier Ltd. All rights reserved."
"57203297479;7403968632;8698049300;36441950300;","Cloudiness regime shift during 1946-1992 recorded by coral in the South China Sea",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-27144519856&partnerID=40&md5=edca3d164f74aca5f1977999a859e809","By extracting and comparing long-term trend components of coral gray value, sea surface temperature, cloudiness, and net heat flux for the period of 1946-1992, the relationships among them are addressed. There exists a prominent regime shift in the cloudiness associated with the corresponding variabilities of sea surface temperature and net heat flux occurred in the mid-1960s, which can be successfully recorded by coral gray value, a climatic proxy. Long-term cloudiness variations in the South China Sea are completely opposite to the equatorial western Pacific in the past five decades, whereas they share a similar trend to that over Asian monsoon prevailing waters. The fact that the coral gray value is highly correlated to cloudiness provides a unique perspective on utilizing this coral to study cloudiness variations in the pre-instrumental period."
"6603820600;7201862430;8287100700;55962364100;6508314561;7403869722;","Paleoclimate changes during the last 100,000 yr from a record in the Brazilian Atlantic rainforest region and interhemispheric comparison",2005,"10.1016/j.yqres.2005.08.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27944508664&doi=10.1016%2fj.yqres.2005.08.006&partnerID=40&md5=e37b46ed61ccd80147fc4c48913ee05a","A long terrestrial record, Colônia CO-3, from the Atlantic rainforest region in Brazil (23°52′S, 46°42′20 ″W, 900 m a.s.l.) registrates variations in the forest expansion during the last 100,000 yr. The 780-cm depth core was analyzed at 2-cm intervals and arboreal pollen frequencies were compared to nearby speleothem stable isotope records and neighboring marine records from the tropical Atlantic. To evaluate regional versus global climate forcing, our record was compared with Greenland and Antarctic ice-core records. These comparisons suggest that changes in temperature seen in polar latitudes relate to moisture changes: e.g., to changes in the length of the dry season, in tropical and subtropical latitudes during glacial as well as interglacial times. These climatic changes result from changes in the frequency of polar air incursions to these latitudes inducing a permanent cloud cover and precipitation. This is an important result that should help define paleoclimatic features in the Southern Hemisphere for the last glaciation. © 2005 University of Washington. All rights reserved."
"55717244800;7003843648;7402333910;","Estimation of the surface heat flux response to sea surface temperature anomalies over the global oceans",2005,"10.1175/JCLI3521.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29144513533&doi=10.1175%2fJCLI3521.1&partnerID=40&md5=2fe094950ab68890b301b8592436bacf","The surface heat flux response to underlying sea surface temperature (SST) anomalies (the surface heat flux feedback) is estimated using 42 yr (1956-97) of ship-derived monthly turbulent heat fluxes and 17 yr (1984-2000) of satellite-derived monthly radiative fluxes over the global oceans for individual seasons. Net surface heat flux feedback is generally negative (i.e., a damping of the underlying SST anomalies) over the global oceans, although there is considerable geographical and seasonal variation. Over the North Pacific Ocean, net surface heat flux feedback is dominated by the turbulent flux component, with maximum values (28 W m-2 K-1) in December-February and minimum values (5 W m-2 K-1) in May-July. These seasonal variations are due to changes in the strength of the climatological mean surface wind speed and the degree to which the near-surface air temperature and humidity adjust to the underlying SST anomalies. Similar features are observed over the extratropical North Atlantic Ocean with maximum (minimum) feedback values of approximately 33 W m-2 K-1 (9 W m-2 K-1) in December-February (June-August). Although the net surface heat flux feedback may be negative, individual components of the feedback can be positive depending on season and location. For example, over the midlatitude North Pacific Ocean during late spring to midsummer, the radiative flux feedback associated with marine boundary layer clouds and fog is positive, and results in a significant enhancement of the mouth-to-month persistence of SST anomalies, nearly doubling the SST anomaly decay time from 2.8 to 5.3 months in May-July. Several regions are identified with net positive heat flux feedback: the tropical western North Atlantic Ocean during boreal winter, the Namibian stratocumulus deck off West Africa during boreal fall, and the Indian Ocean during boreal summer and fall. These positive feedbacks are mainly associated with the following atmospheric responses to positive SST anomalies: 1) reduced surface wind speed (positive turbulent heat flux feedback) over the tropical western North Atlantic and Indian Oceans, 2) reduced marine boundary layer stratocumulus cloud fraction (positive shortwave radiative flux feedback) over the Namibian stratocumulus deck, and 3) enhanced atmospheric water vapor (positive longwave radiative flux feedback) in the vicinity of the tropical deep convection region over the Indian Ocean that exceeds the negative shortwave radiative flux feedback associated with enhanced cloudiness. © 2005 American Meteorological Society."
"7406589460;25722619000;7403559174;","Origin and propagation of a disturbance associated with an African easterly wave as a precursor of Hurricane Alberto (2000)",2005,"10.1175/MWR3035.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28944440818&doi=10.1175%2fMWR3035.1&partnerID=40&md5=01fff977a91ccebc9bf85911a6dd8b34","In this study, it is proposed that mesoscale convective complexes (MCCs) and a mesovortex (MV) were embedded within a wavelike disturbance over North Africa that led to the genesis of Hurricane Alberto (2000). The wavelike disturbance observed may be classified as an African easterly wave (AEW). Based on the cloud-top area and brightness values observed from infrared satellite data, four genesis and three lysis stages are identified within a cycle of moist convection associated with the pre-Alberto disturbance. The availability of water vapor is the most essential factor controlling the convective cycle of the pre-Alberto disturbance over the African continent. The presence of significant topography also contributes to the generation or decay of the associated MCCs through regulation of the water vapor supply. Further analysis of Meteosat satellite imagery reveals that the incipient disturbances for 23 of 34 eastern Atlantic tropical cyclones originated from the Ethiopian highlands (EH) region during the period of 1990-2001. The pre-Alberto disturbance was found to have exhibited characteristics of an AEW. At the EH, there existed two modes of disturbance development: a stationary mode and a propagating mode. The stationary mode corresponded with the generation of moist convection over the EH triggered by diurnally variant sensible heating, while the propagating mode corresponded with the generation and propagation of MVs and mesoscale convective systems (MCSs) from the lee side of the EH over a period of about 2 to 3 days. These components of the disturbance propagated westward together within an AEW train at an average speed of 11.6 m s-1. The average wavelength was roughly estimated to be about 2200 km. To prove that disturbances generated at the EH are indeed AEWs, the NCAR Regional Climate Model Version 3.0 is adopted to simulate the event. The simulated fields showed that both the propagating wave and stationary mountain wave modes were present, the convection was generated over the EH, and the pre-Alberto disturbance was generated near the lee of the EH. In addition, the convective cycle detected from NCEP reanalysis data was also reflected in the simulated fields. The simulated AEW possesses similar wave characteristics as the observed pre-Alberto disturbance. © 2005 American Meteorological Society."
"35509639400;7004714030;","Marine boundary layer clouds at the heart of tropical cloud feedback uncertainties in climate models",2005,"10.1029/2005GL023851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28944450038&doi=10.1029%2f2005GL023851&partnerID=40&md5=f09513bd74190bea6ce77cf8586336c6","The radiative response of tropical clouds to global warming exhibits a large spread among climate models, and this constitutes a major source of uncertainty for climate sensitivity estimates. To better interpret the origin of that uncertainty, we analyze the sensitivity of the tropical cloud radiative forcing to a change in sea surface temperature that is simulated by 15 coupled models simulating climate change and current interannual variability. We show that it is in regimes of large-scale subsidence that the model results (1) differ the most in climate change and (2) disagree the most with observations in the current climate (most models underestimate the interannual sensitivity of clouds albedo to a change in temperature). This suggests that the simulation of the sensitivity of marine boundary layer clouds to changing environmental conditions constitutes, currently, the main source of uncertainty in tropical cloud feedbacks simulated by general circulation models. Copyright 2005 by the American Geophysical Union."
"25647939800;7202954964;9535769800;8962699100;7401945370;7101883060;","A climate sensitivity test using a global cloud resolving model under an aqua planet condition",2005,"10.1029/2005GL023672","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144442423&doi=10.1029%2f2005GL023672&partnerID=40&md5=c6ac266b9c1bf71153222061d04813f7","A global Cloud Resolving Model (CRM) is used in a climate sensitivity test for an aqua planet in this first attempt to evaluate climate sensitivity without cumulus parameterizations. Results from a control experiment and an experiment with global sea surface temperature (SST) warmer by 2 K are examined. Notable features in the simulation with warmer SST include a wider region of active convection, a weaker Hadley circulation, midtropospheric moistening in the subtropics, and more clouds in the extratropics. Negative feedback from shortwave radiation reduces the climate sensitivity parameter compared to a result in a more conventional model with a cumulus parameterization. Copyright 2005 by the American Geophysical Union."
"7004198777;57202521210;7007074942;","Nitrogenated organic aerosols as cloud condensation nuclei",2005,"10.1029/2005GL023605","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144463576&doi=10.1029%2f2005GL023605&partnerID=40&md5=347df27b7a100a86f09b5c2025694b38","One important role of anthropogenic aerosol particles is their influence on climate by acting as cloud condensation nuclei. However, these particles are diverse in composition and mixing state, and our knowledge of which particle types act as cloud condensation nuclei is incomplete. Here we present direct measurements of individual organic particles that nucleated cloud droplets in the atmosphere. These results indicate that nitrogenated organic aerosol particles can act as cloud condensation nuclei without being mixed with inorganic material, and thus influence climate through cloud formation. Copyright 2005 by the American Geophysical Union."
"7003740015;55667068400;","Source and evolution of the marine aerosol - A new perspective",2005,"10.1029/2005GL023651","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144459793&doi=10.1029%2f2005GL023651&partnerID=40&md5=658a3e8efb1b66b270a7786be1b168a3","The ""indirect effect of aerosols"" refers to their ability to influence cloud radiative properties, and is considered to be one of the larger uncertainties in climate prediction. Oceans cover about 70% of the world's surface and the aerosols that they produce are therefore likely to represent an important part of the indirect effect. A description of the ultimate sources of all aerosol constituents and their susceptibility to climate change is then required in order to assess the potential of an aerosol-cloud-climate feedback. Here we argue that in the high Arctic in summer, cloud condensation nuclei (CCN) concentration is not determined by the oxidation products of dimethyl-sulfide as has usually been assumed but by the concentration in the air of small insoluble organic particles derived from the surface microlayer of the ocean by bubble bursting, on which the acid gases condense. Examination of the aerosol over lower latitude oceans suggests that similar processes occur over all oceans. Copyright 2005 by the American Geophysical Union."
"8397494800;25941200000;6602356307;7006204393;6701346974;7202208382;","Atmospheric radiative transfer through global arrays of 2D clouds",2005,"10.1029/2005GL023329","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144438375&doi=10.1029%2f2005GL023329&partnerID=40&md5=194bce1a5e9d2830a9bb22be2c6a3f05","Shortwave and longwave 2D radiative transfer calculations were performed using Monte Carlo radiative transfer models and output from a global climate model (GCM) that employed, in each of its columns, a 2D cloud system-resolving model (CSRM) with a horizontal gridspacing Δx of 4 km. CSRM output were sampled every 9 hours for December 2000. Radiative fluxes were averaged to the GCM's grid. Monthly-mean top of atmosphere (TOA) shortwave flux differences between 2D radiative transfer and the Independent Column Approximation (ICA) are at most 5 W m-2 in the tropics with a zonal-average of 1.5 W m-2. These differences are 2 to 10 times smaller than those stemming from the maximum-random overlap model and neglect of horizontal variability of cloud. Corresponding longwave differences are approximately 3 times smaller than their shortwave counterparts. Use of CSRM data with Δx &lt; 4 km may roughly double the reported differences between 2D and ICA TOA SW fluxes. Copyright 2005 by the American Geophysical Union."
"10241462700;8979277400;10240710000;7007021059;10243650000;7102857642;","A simple scheme for climate feedback analysis",2005,"10.1029/2005GL023673","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144463828&doi=10.1029%2f2005GL023673&partnerID=40&md5=0be02af8bcecaacfc0931da46a9b1f7b","In this study we present a simple scheme for the diagnosis of the strength of climate feedback. The scheme is based on straightforward calculations using the conventional output of a general circulation model (GCM), and evaluates the major radiative feedbacks concerning the surface, clear-sky atmosphere, and clouds. We place an emphasis on evaluating shortwave (SW) feedbacks. Assumptions involved in extracting the SW surface feedback are validated by accurate calculations and considered to be acceptable. The performance of our scheme is demonstrated via a doubled CO2 experiment. Compared to conventional methods, we can evaluate SW feedbacks more accurately while the evaluation of LW feedbacks is essentially similar between the two methods. The ready application of our scheme to the output of various GCMs should be of great use for multi-model ensemble analyses, which contribute to reducing the uncertainty in future climate projections. Copyright 2005 by the American Geophysical Union."
"55905970100;7801344746;57202413846;9534896800;","Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe",2005,"10.1029/2005GL023624","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144456676&doi=10.1029%2f2005GL023624&partnerID=40&md5=1c10968e75f42e8cd808cc60b008aba7","Europe's temperature increases considerably faster than the northern hemisphere average. Detailed month-by-month analyses show temperature and humidity changes for individual months that are similar for all Europe, indicating large-scale weather patterns uniformly influencing temperature. However, superimposed to these changes a strong west-east gradient is observed for all months. The gradual temperature and humidity increases from west to east are not related to circulation but must be due to non-uniform water vapour feedback. Surface radiation measurements in central Europe manifest anthropogenic greenhouse forcing and strong water vapor feedback, enhancing the forcing and temperature rise by about a factor of three. Solar radiation decreases and changing cloud amounts show small net radiative effects. However, high correlation of increasing cloud-ftee longwave downward radiation with temperature (r = 0.99) and absolute humidity (r = 0.89), and high correlation between ERA-40 integrated water vapor and CRU surface temperature changes (r = 0.84), demonstrates greenhouse forcing with strong water vapor feedback. Copyright 2005 by the American Geophysical Union."
"56377612000;7004479957;","A simplified model of the Walker circulation with an interactive ocean mixed layer and cloud-radiative feedbacks",2005,"10.1175/JCLI3534.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28244459627&doi=10.1175%2fJCLI3534.1&partnerID=40&md5=c0414d27daec536e64227232f82a4c31","Cloud-climate feedbacks between precipitation, radiation, circulation strength, atmospheric temperature and moisture, and ocean temperature are studied with an idealized model of the Walker circulation in a nonrotating atmosphere coupled to an ocean mixed layer. This study has two main purposes: 1) to formulate a conceptual framework that includes the dominant feedbacks between clouds and a large-scale divergent circulation; and 2) to use this framework to investigate the sensitivity of the climate system to these interactions. Two cloud types - high, convective anvils and low, nonprecipitating stratus - are included and coupled to the large-scale dynamics. The atmosphere is coupled to an ocean mixed layer via a consistent surface energy budget. Analytic approximations with a simplified radiation scheme are derived and used to explain numerical results with a more realistic radiation scheme. The model simplicity allows interactions between different parts of the ocean-atmosphere system to be cleanly elucidated, yet also allows the areal extent of deep convection and the horizontal structure of the Walker circulation to be internally determined by the model. Because of their strong top-of-atmosphere radiative cancellation, high clouds are found to have little overall effect on the circulation strength and convective area fraction. Instead, to leading order, these are set by the horizontally varying ocean heat transport and clear-sky radiative fluxes. Low clouds are found to cool both the ocean and atmosphere, to slightly increase the circulation strength, and to shrink the convective area significantly. The climate is found to be less sensitive to doubled greenhouse gas experiments with low clouds than without. © 2005 American Meteorological Society."
"7404325680;8944544000;36966898400;7404040259;","Analysis of along track scanning radiometer-2 (ATSR-2) data for clouds, glint and sea surface temperature using neural networks",2005,"10.1016/j.rse.2005.05.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844432934&doi=10.1016%2fj.rse.2005.05.022&partnerID=40&md5=10802fe2d3fd57a2fd1e622c0cb71c03","Improved oceanic cloud climatologies and more accurate sea surface temperature (SST) from satellite data (e.g., the Along Track Scanning Radiometer-2 (ATSR-2)) depend upon the identification, and in the case of SST, masking of cloud from the data. Few cloud-screening algorithms for ATSR-2 data, however, have been published. This is unfortunate because, unlike the original ATSR (hereafter referred to as ATSR-1), ATSR-2 has three bands of visible data in addition to its traditional suite of near-to-far thermal infrared bands. A new neural network-based cloud detection algorithm, which accommodates both the nadir and forward views of the ATSR-2, is presented. It evaluates every pixel in the scene, is statistically reproducible, computationally efficient, and requires no knowledge of cloud type. Moreover, the algorithm accurately detects glint radiance, which is often seen in at least one of the 1.6 μm (and/or visible) views, subpixel cloud near cloud boundaries, low-lying marine stratiform cloud, and does not misinterpret actual ocean thermal gradients as cloud. These latter issues have interfered with many SST retrievals in the past. Dual view/dual channel SST retrievals were derived and validated against buoy data (1 m depth). RMS error between retrieved SST and the buoy data is typically about 0.3 K in regions of minimum SST gradient. Pre-processing of the data is done prior to analysis because some artifacts not seen in ATSR-1 data can seriously compromise both cloud detection and SST retrieval. Detailed comparison between the ATSR operational cloud detection scheme and that developed herein, based upon 1077 scenes, shows that the operational product consistently misinterprets regions of cold but cloud-free oceanic thermal gradient as cloud, leading to a sampling-related warm bias in many of the operational SST products. The basis for this misinterpretation has been identified and quantified. Thus, the operational cloud detection scheme may have to be revised if a fully representative global ocean SST dataset is to be obtained from ATSR data. © 2005 Elsevier Inc. All rights reserved."
"9635764200;7004114883;7102329065;9633685900;","An evaluation of the proposed mechanism of the adaptive infrared iris hypothesis using TRMM VIRS and PR measurements",2005,"10.1175/JCLI3528.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28244466283&doi=10.1175%2fJCLI3528.1&partnerID=40&md5=b6985e9cfece26088f1e8a871d150bd1","Significant controversy surrounds the adaptive infrared iris hypothesis put forth by Lindzen et al., whereby tropical anvil cirrus detrainment is hypothesized to decrease with increasing sea surface temperature (SST). This dependence would act as an iris, allowing more infrared radiation to escape into space and inhibiting changes in the surface temperature. This hypothesis assumes that increased precipitation efficiency in regions of higher sea surface temperatures will reduce cirrus detrainment. Tropical Rainfall Measuring Mission (TRMM) satellite measurements are used here to investigate the adaptive infrared iris hypothesis. Pixel-level Visible and Infrared Scanner (VIRS) 10.8-μm brightness temperature data and precipitation radar (PR) rain-rate data from TRMM are collocated and matched to determine individual convective cloud boundaries. Each cloudy pixel is then matched to the underlying SST. This study examines single- and multicore convective clouds separately to directly determine if a relationship exists between the size of convective clouds, their precipitation, and the underlying SSTs. In doing so, this study addresses some of the criticisms of the Lindzen et al. study by eliminating their more controversial method of relating bulk changes of cloud amount and SST across a large domain in the Tropics. The current analysis does not show any significant SST dependence of the ratio of cloud area to surface rainfall for deep convection in the tropical western and central Pacific. Results do, however, suggest that SST plays an important role in the ratio of cloud area and surface rainfall for warm rain processes. For clouds with brightness temperatures between 270 and 280 K, a net decrease in cloud area normalized by rainfall of 5% per degree SST was found. © 2005 American Meteorological Society."
"7004384155;6504018529;7006537399;","Cloud heights from TOVS Path-B: Evaluation using LITE observations and distributions of highest cloud layers",2005,"10.1029/2004JD005447","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28044461276&doi=10.1029%2f2004JD005447&partnerID=40&md5=3f8fd6c21a87cfcc4f4be51eb712cd6e","Cloud height from the TIROS-N Operational Vertical Sounder (TOVS) Path-B climate data set has been evaluated by using vertical profiles of the backscattered radiation at 532 nin from quasi-simultaneous Lidar In-space Technology Experiment (LITE) observations. Two averaging methods for the LITE inversion have been studied. Because of the LITE noise level and the difficulty in determining the vertical structure of thick clouds, we have chosen to apply the inversion on the average backscatter signal of the LITE spots over regions of 1° latitude × 1° longitude, which is also the spatial resolution of the TOVS Path-B data set. The cloud height determined by TOVS corresponds well in general to the height of the ""apparent middle"" of the cloud system with coincidences for 53% of TOVS Path-B low-level clouds within 1 km and for 49% of TOVS Path-B high-level clouds within 1.5 km. In addition, 22.5% of TOVS Path-B low-level clouds are covered by a very thin high cloud layer not detectable by TOVS. Comparing for these cases the TOVS cloud height with the second LITE cloud layer increases the overall agreement for low-level clouds to about 64%. High-level clouds appear more often in multilayer systems (about 75%) and are also vertically more extended. Differences in average cloud height of high-level clouds appear only to be significant (13.3 km from LITE compared to 11.3 km from TOVS Path-B) in the tropics with a large extent of laminar cirrus situated near the tropopause. fhe height of maximum backscatter of most thick clouds is several hundred meters above ""apparent cloud midlevel,"" whereas thin high-level clouds with underlying lower clouds provide a backscatter signal nearer to apparent cloud midlevel. In the latter case, the retrieved TOVS Path-B cloud height is on average 280 m underestimated. Pressure distributions of the highest cloud layer weighted by effective cloud amount confirmed that high clouds have the lowest pressure in the tropics because of a higher tropopause, and in these regions there are nearly no cloud systems with the highest cloud layer in the middle troposphere. The Southern Hemisphere midlatitudes are mostly covered by low-level clouds. Seasonal differences in the Northern Hemisphere (midlatitudes, with more equally distributed cloud altitudes in winter) are mostly caused by changes over land. Copyright 2005 by the American Geophysical Union."
"36658658900;6603954179;","Historical land use changes and mesoscale summer climate on the Swiss Plateau",2005,"10.1029/2004JD005215","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28044470773&doi=10.1029%2f2004JD005215&partnerID=40&md5=4a6cb8c8090e52228a5798155885ebd7","The impacts of historical land use changes on the Swiss Plateau on the summer climate were investigated. The land use changes consist primarily of a conversion of wetlands with extended peat soils into highly productive agricultural lands. We used the ""Lokal-Modell"" of the Consortium for Small-Scale Modeling to conduct several 1-month-long high-resolution simulations (1.5 × 1.5 km2) with present and past landscape conditions. The past land use was reconstructed from historical maps (1800-1850) over a relatively small perturbed area of ≈400 km2 embedded in an otherwise unchanged present-day landscape. The documented changes in land use and land cover lead to a daytime cooling of up to 0.3°C and a nocturnal warming of the same magnitude, thereby decreasing the diurnal temperature range by 0.6°C. The alteration of the radiation budget and the surface energy balance leads to a shallower daytime mixed layer under present compared to past conditions, with a reduction in the convective upward transport of moisture. The cloud coverage over the study area decreased by up to 5% on average under present conditions. The regional precipitation is most strongly affected in the mean downwind areas and not so much over the area of land use changes. Because of orographic effects in the downwind area a decrease in precipitation in lower-elevation areas was modeled, while precipitation in the adjacent higher-elevation downwind areas increased. In contrast to our expectations the soil water status did not play a dominant role in this area because of the high water table. Even under present conditions the availability of soil moisture and the accessibility of the groundwater to plant roots is, on average, still not a limiting factor for plant transpiration. Copyright 2005 by the American Geophysical Union."
"12785824300;","An object-oriented approach to simulating convective rainfall over an island heat source",2005,"10.1002/asl.114","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645020352&doi=10.1002%2fasl.114&partnerID=40&md5=241e30dcd1235bb78367c526b6a146d7","A model for simulating the life cycle of convective cloud formation through daytime heating over a small island is developed. Resulting precipitation is also simulated. The evolution of the cloud cells is represented as a sequence of stages, with both the main and supporting cells described by attributes whose values change as the atmospheric environment evolves. Copyright © 2006 Royal Meteorological Society."
"25941200000;6701511324;","Radiative sensitivities for cloud structural properties that are unresolved by conventional GCMs",2005,"10.1256/qj.04.174","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31944440057&doi=10.1256%2fqj.04.174&partnerID=40&md5=026f438dbb6f0b9b977103e98f039527","The Independent Column Approximation (ICA), a stochastic subgrid-scale cloudy column generator, and a dataset produced by an array of two-dimensional cloud system-resolving models are used to estimate radiative sensitivities and uncertainties for parameters that describe the macrostructure of layered cloud at scales unresolved by conventional global climate models (GCMs). Three cloud structural parameters are considered: vertical overlap of fractional cloud, vertical overlap of cloud condensate, and horizontal variability of condensate. Radiative sensitivity is the derivative of top of atmosphere (TOA) fluxes with respect to a cloud structural parameter. Radiative uncertainty is defined as the product of radiative sensitivity and corresponding uncertainty in structural parameter. It is argued that radiative sensitivities and uncertainties can help direct and prioritize development of subgrid-scale parametrizations. Using estimates of sensitivities and uncertainties for structural parameters, it is shown that uncertainties in TOA short-wave fluxes for cloud fraction overlap and horizontal variability are of similar magnitude averaged over the globe but display distinct spatial differences. Corresponding values for overlap of condensate are smaller and thus less important. For long-wave radiation, cloud horizontal variability is generally the most important of the three parameters considered here, but sensitivities, and thus uncertainties, are smaller than those for short-wave radiation. It is estimated that uncertainties associated with overlap of fractional cloud and horizontal variability are approximately as large as those associated with effective size of cloud particles. These results reinforce prior claims that GCM parametrizations for cloud overlap and horizontal variability should be addressed together, especially at solar wavelengths. These results are echoed in the appendix which examines TOA forcings that would arise in a GCM if the maximum-random overlap of homogeneous clouds model was replaced by a model that addresses the cloud parameters mentioned above. © Royal Meteorological Society, 2005."
"9534896800;55905970100;","TURAC - A new instrument package for radiation budget measurements and cloud detection",2005,"10.1175/JTECH1800.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744439888&doi=10.1175%2fJTECH1800.1&partnerID=40&md5=f189a89ad6c5e8e6bc08fc4ffb03db33","Atmospheric radiation flux measurements and the resulting surface radiation budget are important quantities for greenhouse effect and climate change investigations. Accurate net shortwave and longwave fluxes, in conjunction with numerical algorithms, also allow monitoring of the radiative effect of clouds and the nowcasting of the cloud amount. To achieve certain advantages on the accuracy of flux measurements a new instrument is developed that measures downward and upward shortwave and longwave radiation with the same sensors. Two high-quality instruments - a pyranometer for shortwave and a pyrgeometer for longwave measurements - are mounted on a pivotable sensor head, which is rotated up and down in 10-min intervals. To keep the instrument domes free from dew and ice, and to minimize the pyranometer thermal offset, both sensors are ventilated with slightly heated air. Additionally, a ventilated temperature and humidity sensor is integrated in the new instrument. The combination of measurements of radiation fluxes, temperature, and humidity allows for instrument use for autonomous and automatic cloud amount detection. The Temperature, Humidity, Radiation and Clouds (TURAC) sensor has been successfully tested under harsh alpine winter conditions, as well as under moderate lowland conditions. Comparisons to reference instruments showed all radiation fluxes to be within a maximum bias and rms difference of 1.6% or 1.4 W m-2 on daily averages. © 2005 American Meteorological Society."
"6701850538;7004479957;35584010200;","Mesoscale variability and drizzle in southeast Pacific stratocumulus",2005,"10.1175/JAS3567.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744519094&doi=10.1175%2fJAS3567.1&partnerID=40&md5=6b72ba8648976f1737578bf2ba18b123","Observations from the East Pacific Investigation of Climate (EPIC) 2001 field campaign are well suited for exploring the relationships among the diurnal cycle, mesoscale (10-100 km) structure, and precipitation in the stratocumulus region in the southeast Pacific. Meteorological time series and observations from a scanning C-band radar, vertically pointing cloud radar, and ceilometer, as well as satellite data, are used to show that drizzle is associated with increased variability in cloud and boundary layer properties compared to nondrizzling periods. The stratocumulus-topped boundary layer is typically well mixed at night, transitioning to less well mixed in the afternoon, with drizzle most frequently occurring in the early morning. Coherent patches of drizzle, or ""cells,"" can have large areas with radar reflectivities of greater than 5 dBZ of up to about 100 km2. Individual cells have long lifetimes, up to 2 h, and appear to be replenished by moisture in the boundary layer. © 2005 American Meteorological Society."
"57201725986;7006329926;7401559815;7202772927;","Tropical convective responses to microphysical and radiative processes: A sensitivity study with a 2-D cloud resolving model",2005,"10.1007/s00703-004-0088-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27144481025&doi=10.1007%2fs00703-004-0088-5&partnerID=40&md5=9921f020361c98c9330e387c50ce1c34","Prognostic cloud schemes are increasingly used in weather and climate models in order to better treat cloud-radiation processes. Simplifications are often made in such schemes for computational efficiency, like the scheme being used in the National Centers for Environment Prediction models that excludes some microphysical processes and precipitation-radiation interaction. In this study, sensitivity tests with a 2-D cloud resolving model are carried out to examine effects of the excluded microphysical processes and precipitation-radiation interaction on tropical thermodynamics and cloud properties. The model is integrated for 10 days with the imposed vertical velocity derived from the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. The experiment excluding the depositional growth of snow from cloud ice shows anomalous growth of cloud ice and more than 20% increase of fractional cloud cover, indicating that the lack of the depositional snow growth causes unrealistically large mixing ratio of cloud ice. The experiment excluding the precipitation-radiation interaction displays a significant cooling and drying bias. The analysis of heat and moisture budgets shows that the simulation without the interaction produces more stable upper troposphere and more unstable mid and lower troposphere than does the simulation with the interaction. Thus, the suppressed growth of ice clouds in upper troposphere and stronger radiative cooling in mid and lower troposphere are responsible for the cooling bias, and less evaporation of rain associated with the large-scale subsidence induces the drying in mid and lower troposphere. © Springer-Verlag 2004."
"9536505300;7006561559;56098354400;","A climatology of snow-to-liquid ratio for the Contiguous United States",2005,"10.1175/WAF856.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144452105&doi=10.1175%2fWAF856.1&partnerID=40&md5=fb363488ed26f97640e4e82646cecafd","A 30-yr climatology of the snow-to-liquid-equivalent ratio (SLR) using the National Weather Service (NWS) Cooperative Summary of the Day (COOP) data is presented. Descriptive statistics are presented for 96 NWS county warning areas (CWAs), along with a discussion of selected histograms of interest. The results of the climatology indicate that a mean SLR value of 13 appears more appropriate for much of the country rather than the often-assumed value of 10, although considerable spatial variation in the mean exists. The distribution for the entire dataset exhibits positive skewness. Histograms for individual CWAs are both positively and negatively skewed, depending upon the variability of the in-cloud, subcloud, and ground conditions. © 2005 American Meteorological Society."
"25630111000;7102615791;","Indian Ocean sea surface temperature variability and winter rainfall: Eastern Australia",2005,"10.1029/2004WR003845","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27644495623&doi=10.1029%2f2004WR003845&partnerID=40&md5=0b050f84dde01ee0d1daf813fb45725d","[1] This study investigates the relationship between sea surface temperature (SST) variability occurring over the Indian Ocean and winter rainfall variability in eastern Australia. Six indices of SST variability are compared and their relationship to rainfall over eastern Australia is determined. An analysis of historical rainfall data for Queensland, New South Wales, and Victoria reveals that a strong relationship exists between a number of these indices and winter rainfall. In particular, anomalous SSTs over the Indonesian region provide a good indication of winter rainfall variability in eastern Australia. Additionally, this relationship is shown to hold true irrespective of potential impacts on rainfall by the El Niño-Southern Oscillation (ENSO). A possible physical process by which the Indian Ocean SST anomalies may influence winter rainfall is proposed, involving their impact on the nature of the northwest Australian cloud band. This study demonstrates marked controls on winter climate variability comparable to that induced in summer by the better known ENSO processes and hence offers improved understanding of year-round seasonal climates. Copyright 2005 by the American Geophysical Union."
"55951088700;7403018641;6603748044;7004602432;7402601230;7005500144;7103086662;6602205640;55881697700;","A 17 000-year history of Andean climate and vegetation change from Laguna de Chochos, Peru",2005,"10.1002/jqs.983","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29744432667&doi=10.1002%2fjqs.983&partnerID=40&md5=dd840d6784e1faa0329db79be94a6b6f","The manifestation of major climatic events such as the timing of deglaciation and whether, or not, the Younger Dryas affected Andean systems has garnered considerable recent attention. Even the Holocene is rapidly emerging as a time of considerable interest in Neotropical palaeoclimatology and palaeoecology. The Holocene of the Neotropics is now revealed as a time of some temperature change with precipitation:evaporation ratios fluctuating markedly. Major changes in lake level, ice-accumulation, and vegetation are indicative of changes both in precipitation and temperature regimes. Although global-scale forcing mechanisms may underlie some of these changes, e.g. the precessional rhythm, other variability appears to be localised. In a record from near the upper forest limit of the eastern Peruvian Andes, pollen, charcoal, and sedimentary data suggest that the deglaciational period from ca. 17 000 to ca. 11 500 cal. yr BP was a period of rapid climatic oscillations, set against an overall trend of warming. A warm-dry event is evident between ca. 9500 and ca. 7300 cal. yr BP, and comparisons with other regional archives suggest that it was regional in scale. A ca. 1500-yr periodicity in the magnetic susceptibility data is evident between 12 000 and 6000 cal.yr BP, reaching a peak intensity during the dry event. A weaker oscillation with a 500-600-yr periodicity is present throughout much of the Holocene. The uppermost sample of the pollen analysis reveals deforestation as modern human land use simplified the landscape. Copyright © 2005 John Wiley & Sons, Ltd."
"36856321600;7004479957;24722339600;","Mixed-layer budget analysis of the diurnal cycle of entrainment in southeast Pacific stratocumulus",2005,"10.1175/JAS3561.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744556446&doi=10.1175%2fJAS3561.1&partnerID=40&md5=49ff1dd8ff67b0fcf9f20bc64bbebafd","Mixed-layer budgets of boundary layer mass, moisture, and liquid water static energy are estimated from 6 days of data collected at 20°S, 85°W (a region of persistent stratocumulus) during the East Pacific Investigation of Climate (EPIC) stratocumulus cruise in 2001. These budgets are used to estimate a mean diurnal cycle of entrainment and, by diagnosing the fluxes of humidity and liquid water static energy necessary to maintain a mixed-layer structure, of buoyancy flux. Although the entrainment rates suggested by each of the budgets have significant uncertainty, the various methods are consistent in predicting a 6-day mean entrainment rate of 4 ± 1 mm s-1, with higher values at night and very little entrainment around local noon. The diurnal cycle of buoyancy flux suggests that drizzle, while only a small term in the boundary layer moisture budget, significantly reduces subcloud buoyancy flux and may induce weak decoupling of surface and cloud-layer turbulence during the early morning hours, a structure that is maintained throughout the day by shortwave warming. Finally, the diurnal cycle of entrainment diagnosed from three recently proposed entrainment closures is found to be consistent with the observationally derived values. © 2005 American Meteorological Society."
"6602501796;7006711251;35515569200;7404463654;7004234960;","Estimation of vertical profiles of raindrop size distribution from the VHF wind profiler radar Doppler spectra",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749378317&partnerID=40&md5=3d7c66a968efe23a14e43f9a4accc61c","This paper describes research on a new form of gamma drop size distribution (DSD) model that employs two arbitrary moments as free DSD parameters to enhance the flexibility in studying the characteristics of gamma DSD model to fit the spectrum. The validity of a DSD model is evaluated in terms of the stability in solving non-linear least-squares (NLLS) problem and the accuracy in DSD moment estimates. The microphysical [i.e., raindrop size distributions (DSD)] parameters are retrieved during stratiform precipitating cloud system passed (on 23 Oct. 1997) overhead of 53-MHz VHP wind profiler radar at Gadanki. The retrieved rain integral parameters were compared to the corresponding disdrometer data and a reasonably good agreement between the measurements has been found, lending credence to the VHP wind profiler radar retrievals of DSD parameters. Wind profiler radar estimated DSD during stratiform precipitation has been compared with the lognormal Indian climate model. It is observed that the pattern of DSD agrees closely with both models."
"36783231600;7004991320;7005034568;55493559100;","The improved AMSU rain-rate algorithm and its evaluation for a cool season event in the western United States",2005,"10.1175/WAF880.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144452931&doi=10.1175%2fWAF880.1&partnerID=40&md5=942ff3e49b40bb91279737684444f820","Rain-rate retrievals from passive microwave sensors are useful for a number of applications related to weather forecasting. For example, in the United States, such estimates are useful for offshore rainfall systems approaching land and in regions where the Weather Surveillance Radar-1988 Doppler (WSR-88D) network is inadequate. Improvements have been made to the rain-rate retrieval from the Advanced Microwave Sounding Unit (AMSU) on board the National Oceanic and Atmospheric Administration (NOAA) Polar Orbiting Environmental Satellites (POESs). The new features of the improved rain-rate algorithm include a two-stream correction of the satellite brightness temperatures at 89 and 150 GHz, cloud-and rain-type classification for better retrieval of rain rate, and removal of the two ad hoc thresholds in the ice water path (IWP) and effective diameter (De) retrieval where the scattering signals are very small. In this paper, the new algorithm has been compared to the previous NOAA operational algorithm. In particular, the better utilization of the measurements at and above 150 GHz is shown to produce improved sensitivity to light rainfall associated with winter season storm systems. This improvement is demonstrated through a wintertime case study over southern California during February 2003. © 2005 American Meteorological Society."
"9249239700;7003278104;7404829395;7404297096;35550043200;7202796519;7003406400;7103271625;7101801476;7202772927;35425197200;25227357000;7102018821;57193132723;6701346974;9249241200;","Comparisons of EOS MLS cloud ice measurements with ECMWF analyses and GCM simulations: Initial results",2005,"10.1029/2005GL023788","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744526018&doi=10.1029%2f2005GL023788&partnerID=40&md5=8436504bd37db1ebdc69f345aa381898","To assess the status of global climate models (GCMs) in simulating upper-tropospheric ice water content (IWC), a new set of IWC measurements from the Earth Observing System's Microwave Limb Sounder (MLS) are used. Comparisons are made with ECMWF analyses and simulations from several GCMs, including two with multi-scale-modeling framework. For January 2005 monthly and daily mean values, the spatial agreement between MLS and ECMWF is quite good, although MLS estimates are higher by a factor of 2-3 over the Western Pacific, tropical Africa and South America. For the GCMs, the model-data agreement is within a factor of 2-4 with larger values of disagreement occurring over Eastern Pacific and Atlantic ITCZs, tropical Africa and South America. The implications arising from sampling and uncertainties in the observations, the modeled values and their comparison are discussed. These initial results demonstrate the potential usefulness of this data set for evaluating GCM performance and guiding development efforts. Copyright 2005 by the American Geophysical Union."
"57196934613;6701540733;","The role of convective plumes and vortices on the global aerosol budget",2005,"10.1029/2005GL023420","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744455592&doi=10.1029%2f2005GL023420&partnerID=40&md5=35368830f484cfd318db33cb04bd92ce","Atmospheric aerosols produce both a direct radiative forcing by scattering and absorbing solar and infrared radiation, and an indirect radiative forcing by altering cloud processes. Therefore, it is essential to understand the physical processes that contribute to the global aerosol budget. The International Panel on Climate Change (IPCC) reports that mineral dust contributes to ∼1/3 of all primary particle emissions to the atmosphere. The significance of mineral dust aerosol becomes evident when one considers the large surface area of arid and semi-arid regions on most continents. It is evident from observations in the U.S. Southwest that convective plumes and vortices lift large quantities of desert dust. Here, we use a combination of observational data and theory to determine the role of convective plumes and vortices on the global aerosol budget. We show that convective plumes and vortices contribute to about 35% of the global budget of mineral dust. Copyright 2005 by the American Geophysical Union."
"6603936062;6506537159;7102743829;","Assessment of variability in continental low stratiform clouds based on observations of radar reflectivity",2005,"10.1029/2005JD006158","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744607094&doi=10.1029%2f2005JD006158&partnerID=40&md5=946c483319fd2213adb9c091e729a841","The variability of overcast low stratiform clouds observed over the ARM Climate Research Facility Southern Great Plains (ACRF SGP) site is analyzed, and an approach to characterizing subgrid variability based on assumed statistical distributions is evaluated. The analysis is based on a vast (>1000 hours) radar reflectivity database collected by the Millimeter-Wave Cloud Radar at ACRF SGP site. The radar data are classified into two low cloud categories and stratified by scale and the presence of precipitation. Cloud variability is analyzed by studying statistical distributions for the first two moments of the probability distribution functions (PDF) of radar reflectivity. Results indicate that variability for a broadly defined low-altitude stratiform cloud type exhibits on average 40% greater standard deviation than canonical boundary layer clouds topped by an inversion. Cloud variability also dramatically depends on microphysical processes (as manifested in radar reflectivity) and increases by 2-5 times within a typical reflectivity range. Finally, variability is a strong function of scale and almost doubles in the 20-100 min temporal scale range. Formulations of subgrid variability, based on PDFs of reflectivity, are evaluated for the two cloud types and two scales of 10 and 30 km, taken to be representative of mesoscale and NWP model grid sizes. The results show that for these cloud types and scales the PDF of reflectivity can be reasonably well approximated by a truncated Gaussian function, specified by mean and standard deviation with the latter parameterized as a linear function of the mean. Copyright 2005 by the American Geophysical Union."
"9249605700;6603215444;","Dust storms and cyclone tracks over the arid regions in east Asia in spring",2005,"10.1029/2004JD004698","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744505386&doi=10.1029%2f2004JD004698&partnerID=40&md5=896fbdb2a1abf4a24296998e9b48d29e","It has been argued that frequent dust storm developments in east Asia in spring are closely related to midlatitude synoptic-scale cyclone activity. This study investigates the relationship of springtime dust storms and other dust-related phenomena in east Asia to the tracks and locations of synoptic-scale cyclones by conducting statistical analyses of surface weather data, cyclone track data, and satellite data. Through these analyses, we discuss the role of cyclone activity on dust weather phenomena in east Asia. In the Gobi Desert and northeast China regions, strong cyclonic winds associated with strong cyclones are responsible for the dust weather developments, and the dust weather preferably occurs in the southwestern sector of the cyclone, where frontal activity and cold air action are significant. Despite the extremely dry climate, the formation of frontal cloud systems is evident particularly over the Gobi Desert, which will contribute to the higher frequency of severer dust weather. On the other hand, in the Taklamakan Desert severe dust weather (i.e., dust storm) is not so much affected by synoptic-scale cyclones, but weaker dust phenomena such as dust haze occur around the centers of cyclones that do not propagate farther eastward out of the Taklamakan region. Copyright 2005 by the American Geophysical Union."
"7402005920;10243922700;55649026100;","Biologically effective UV-B exposures of an oak-hickory forest understory during leaf-out",2005,"10.1016/j.agrformet.2005.06.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24944588659&doi=10.1016%2fj.agrformet.2005.06.008&partnerID=40&md5=5cec1ae852a195231f4d16e5793b2f3e","Although it is known that many plant species that are sensitive to solar UV radiation exist in low radiation environments, little is known about the sensitivity of young tree seedlings and herbaceous forest vegetation that inhabits the low radiation environment of the forest understory. Furthermore, little is known about the UV radiation environment of this vegetation during the deciduous forest leaf-out period when solar radiation levels are the highest. The development of the forest canopy and the penetration of solar UV radiation through the canopy to the understory of a deciduous upland forest was studied between 15 April and 1 June of 2004. During the early part of the leaf-out period, the mean canopy transmittance in the PAR exceeded that in the UV-A or UV-B. By 20 days into the leaf-out period, the PAR transmittance was nearly equal to that of the UV. As the leaves in the canopy reached full expansion, the PAR, UV-A and UV-B penetration was essentially equal and small. Canopy transmittance during leaf-out was not dependent on cloud cover. Greater penetration of solar radiation in longer wavelengths within the UV was probably a result of scattering of direct beam radiation off tree bark in the canopy. The effective canopy transmittance from 15 March through the canopy leaf-out was 47%. For an expected period of UV exposure for the herbaceous layer of 15 March through 15 May, the tree seedlings and herbaceous plants received 41 kJ m -2 of biologically effective UV-B radiation. It is projected that the herbaceous layer vegetation will receive approximately 27% more UVB BE radiation on clear days with a decreased stratospheric ozone of 20 DU and approximately 3% more UVBBE radiation with increased temperatures causing leaf-out to begin 10 days earlier than 2004. More research is needed to understand the potential interactions of these and other climate change components on the deciduous forest. © 2005 Elsevier B.V. All rights reserved."
"7005696579;8871497700;8758100000;8871498000;7004047498;6603948265;7006595513;35461255500;","The contribution of sulfuric acid and non-volatile compounds on the growth of freshly formed atmospheric aerosols",2005,"10.1029/2005GL023827","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27544466393&doi=10.1029%2f2005GL023827&partnerID=40&md5=66dd825eac8384c81692c7890bdbccd4","The formation of atmospheric aerosol particles (homogeneous nucleation, forming of stable clusters ∼1 nm in size), their subsequent growth to detectable sizes (>3 nm), and to the size of cloud condensation nuclei, remains one of the least understood atmospheric processes upon which global climate change critically depends. However, a quantitative model explanation for the growth of freshly formed aerosols has been missing. In this study, we present observations explaining the nucleation mode (3-25 nm) growth. Aerosol particles typically grow from 3 nm to 60-70 nm during a day, while their non-volatile cores grow by 10-20 nm as well. The total particle growth rate is 2-8 nm/h while the non-volatile core material can explain 20-40%. According to our results, sulfuric acid can explain the remainder of the growth, until the particle diameter is around 10-20 nm. After that secondary organic compounds significantly take part in growth process. Copyright 2005 by the American Geophysical Union."
"6602600408;57203200427;","Constraining the first aerosol indirect radiative forcing in the LMDZ GCM using POLDER and MODIS satellite data",2005,"10.1029/2005GL023850","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27544439576&doi=10.1029%2f2005GL023850&partnerID=40&md5=711845df2d2017f97876aecc0ee98a67","The indirect effects of anthropogenic aerosols are expected to cause a significant radiative forcing of the Earth's climate whose magnitude, however, is still uncertain. Most climate models use parameterizations for the aerosol indirect effects based on so-called ""empirical relationships"" which link the cloud droplet number concentration to the aerosol concentration. New satellite datasets such as those from the POLDER and MODIS instruments are well suited to evaluate and improve such parameterizations at a global scale. We derive statistical relationships of cloud-top droplet radius and aerosol index (or aerosol optical depth) from satellite retrievals and fit an empirical parameterization in a general circulation model to match the relationships. When applying the fitted parameterizations in the model, the simulated radiative forcing by the first aerosol indirect effect is reduced by 50% as compared to our baseline simulation (down to -0.3 and -0.4 Wm-2 when using MODIS and POLDER satellite data, respectively). Copyright 2005 by the American Geophysical Union."
"35464731600;6701465132;55947099700;7102517130;7004174939;7202079615;","Aerosol anthropogenic component estimated from satellite data",2005,"10.1029/2005GL023125","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27544501820&doi=10.1029%2f2005GL023125&partnerID=40&md5=ae1c85110c40bb90b1c860e3edbe716d","Satellite instruments do not measure the aerosol chemical composition needed to discriminate anthropogenic from natural aerosol components. However the ability of new satellite instruments to distinguish fine (submicron) from coarse (supermicron) aerosols over the oceans, serves as a signature of the anthropogenic component and can be used to estimate the fraction of anthropogenic aerosols with an uncertainty of ±30%. Application to two years of global MODIS data shows that 21 ± 7% of the aerosol optical thickness over the oceans has an anthropogenic origin. We found that three chemical transport models, used for global estimates of the aerosol forcing of climate, calculate a global average anthropogenic optical thickness over the ocean between 0.030 and 0.036, in line with the present MODIS assessment of 0.033. This increases our confidence in model assessments of the aerosol direct forcing of climate. The MODIS estimated aerosol forcing over cloud free oceans is therefore -1.4 ± 0.4 W/m2. Copyright 2005 by the American Geophysical Union."
"55835127000;7003529616;8894188000;","The relation between rainfall and area-time integrals at the transition from an arid to an equatorial climate",2005,"10.1175/JCLI3451.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27144436380&doi=10.1175%2fJCLI3451.1&partnerID=40&md5=c34b526df182b81ddc80b233ad56fe31","The area-time integral (ATI) method has previously been successfully used to estimate the area-averaged rain-rate distribution and the rainfall volume over an area from radar or from satellite infrared (IR) data. In most cases, the method was implemented over regions or test areas with an assumed homogeneous climatic character, that is, without a strong spatial variation of the rain regime throughout the test area. In the present paper, the behavior of the ATI method is discussed for a test area displaying two strong gradients of the cumulative annual rainfall: one meridional, at the transition between regions having, respectively, a desertic and an equatorial climate and the other zonal, at the transition between land and sea. The studied area is divided into four subtest areas (north, south, land, and sea) over which the ATI computation is applied separately. The linear coefficient relating the radar-observed area-averaged rain rate and the fractional area where the rain is higher than a threshold calculated over the four subtest areas is found to be almost constant, in agreement with the ergodic character of the rain-rate distribution observed in this region. Similarly, the linear coefficient relating the rain volume over the subtest areas to the IR satellite-derived ATI, a parameter analogous to the Geostationary Operational Environmental Satellite (GOES) Precipitation Index (GPI), is found to be very steady, with a mean value of 3.02 mm h-1 and a coefficient of variation of only 8%. These coefficients, as well as the underlying dynamic and microphysical processes, do not seem significantly influenced by the climatic character, even at a short space scale, in the studied area. The ratio of radar rain areas to cloud areas is, notably, almost constant. For a brightness temperature of 235 K, the ratio of the cloud area to rain area is around 1.68. © 2005 American Meteorological Society."
"7006417494;56537463000;","Moist teleconnection mechanisms for the tropical South American and atlantic sector",2005,"10.1175/JCLI3517.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344445278&doi=10.1175%2fJCLI3517.1&partnerID=40&md5=9bd2c12b8364e6fdda3e0a9c8307b499","Teleconnections have traditionally been studied for the case of dry dynamical response to a given diabatic heat source. Important anomalies often occur within convective zones, for instance, in the observed remote response to El Niño. The reduction of rainfall and teleconnection propagation in deep convective regions poses theoretical challenges because feedbacks involving convective heating and cloud radiative effects come into play. Land surface feedbacks, including variations of land surface temperature, and ocean surface layer temperature response must be taken into account. During El Niño, descent and negative precipitation anomalies often extend across equatorial South America and the Atlantic intertropical convergence zone. Analysis of simulated mechanisms in a case study of the 1997/98 El Niño is used to illustrate the general principals of teleconnections occurring in deep convective zones, contrasting land and ocean regions. Comparison to other simulated events shows similar behavior. Tropospheric temperature and wind anomalies are spread eastward by wave dynamics modified by interaction with the moist convection zones. The traditional picture would have gradual descent balanced by radiative damping, but this scenario misses the most important balances in the moist static energy (MSE) budget. A small ""zoo"" of mechanisms is active in producing strong regional descent anomalies and associated drought. Factors common to several mechanisms include the role of convective quasi equilibrium (QE) in linking low-level moisture anomalies to free tropospheric temperature anomalies in a two-way interaction referred to as QE mediation. Convective heating feedbacks change the net static stability to a gross moist stability (GMS) M. The large cloud radiative feedback terms may be manipulated to appear as a modified static stability Meff, under approximations that are quantified for the quasi-equilibrium tropical circulation model used here. The relevant measure of Meff differs between land, where surface energy flux balance applies, and short time scales over ocean. For the time scale of an onsetting El Niño, a mixed layer ocean response is similar to a fixed sea surface temperature (SST) case, with surface fluxes lost into the ocean and Meff substantially reduced over ocean-enhancing descent anomalies. Use of Meff aids analysis of terms that act as the initiators of descent anomalies. Apparently modest terms in the MSE budget can be acted on by the GMS multiplier effect, which yields substantial precipitation anomalies due to the large ratio of the moisture convergence to the MSE divergence. Advection terms enter in several mechanisms, with the leading effects here due to advection by mean winds in both MSE and momentum balances. A Kelvinoid solution is presented as a prototype for how easterly flow enhances moist wave decay mechanisms, permitting relatively small damping terms by surface drag and radiative damping to produce the substantial eastward temperature gradients seen in observations and simulations and contributing to precipitation anomalies. The leading mechanism for drought in eastern equatorial South America is the upped-ante mechanism in which QE mediation of teleconnected tropospheric temperature anomalies tends to produce moisture gradients between the convection zone, where low-level moisture increases toward QE, and the neighboring nonconvective region. Over the Atlantic ITCZ, the upped-ante mechanism is a substantial contributor, but on short time scales several mechanisms referred to jointly as troposphere/SST disequilibrium mechanisms are important. While SST is adjusting during passive SST (coupled ocean mixed layer) experiments, or for fixed SST, heat flux to the ocean is lost to the atmosphere, and these mechanisms can induce descent and precipitation anomalies, although they disappear when SST equilibrates. In simulations here, cloud radiative feedbacks, surface heat fluxes induced by teleconnected wind anomalies, and surface fluxes induced by QE-mediated temperature anomalies are significant disequilibrium contributors. At time scales of several months or longer, remaining Atlantic ITCZ rainfall reductions are maintained by the upped-ante mechanism. © 2005 American Meteorological Society."
"14321134500;7801673320;14626835600;8710425900;","Large-scale water resources management within the framework of GLOWA-Danube. Part A: The groundwater model",2005,"10.1016/j.pce.2005.06.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24044524961&doi=10.1016%2fj.pce.2005.06.003&partnerID=40&md5=a39c6ba2d95d5731ea1c5a018715a11b","The research project GLOWA-Danube, financed by the German Federal Government, is investigating long-term changes in the water cycle of the upper Danube river basin (77,000 km2) in light of global climatic change. Its aim is to build a fully integrated decision-support tool ""DANUBIA"" that combines the competence of 11 different research institutes in domains covering all major aspects governing the water cycle-from the formation of clouds, to groundwater flow patterns, to the behaviour of the water consumer. Both the influence of natural changes in the ecosystem, such as climate change, and changes in human behaviour, such as changes in land use or water consumption, are considered. DANUBIA is comprised of 15 individual disciplinary models that are connected via customized interfaces that facilitate network-based parallel calculations. The strictly object-oriented DANUBIA architecture was developed using the graphical notation tool UML (Unified Modeling Language) and has been implemented in Java code. All models use the same spatial discretisation for the exchange of data (1 × 1 km grid cells) but are using different time steps. The representation of a vast number of relevant physical and social processes that occur at different spatial and temporal scales is a very demanding task. Newly developed up- and downscaling procedures [Rojanschi, V., 2001. Effects of upscaling for a finite-difference flow model. Master's Thesis, Institut für Wasserbau, Universität Stuttgart, Stuttgart, Germany] and a sophisticated time controller developed by the computer sciences group [Hennicker, R., Barth, M., Kraus, A., Ludwig, M., 2002. DANUBIA: A Web-based modelling and decision support system for integrative global change research in the upper Danube basin. In: GSF (Ed.), GLOWA, German Program on Global Change in the Hydrological Cycle Status Report 2002. GSF, Munich, pp. 35-38; Kraus, A., Ludwig, M., 2003. GLOWA-Danube Papers Technical Release No. 002 (Danubia Framework), Software-Release No.: 0.9.2, Documentation Version: 0.10, Release Date: 27 March 2003] are required to solve the emerging problems. After a first successful public demonstration of the DANUBIA package (nine models) in May 2002 [Mauser, W., Stolz, R., Colgan, A., 2002. GLOWA-Danube: integrative techniques, scenarios and strategies regarding global change of the water cycle. In: GSF (Ed.), GLOWA, German Program on Global Change in the Hydrological Cycle (Phase I, 2000-2003) Status Report 2002. GSF, Munich, pp. 31-34], the research consortium is now preparing a first validation run of DANUBIA for the period 1995-1999 with all 15 models. After successful completion of the validation, a scenario run based on IPCC climate scenarios [IPCC, 2001. Climate Change 2001: Synthesis Report. In: Watson, R.T., Core Writing Team (Eds.), A Contribution of Working Groups I, II, and III to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK and New York, NY, USA, 398pp] for a five year period between 2025 and 2040 will follow at the end of 2003. The research group ""Groundwater and Water Resources Management"" at the Institute of Hydraulic Engineering, Universität Stuttgart, is contributing both a three-dimensional groundwater flow model of the catchment and an agent-based model for simulating water supply and distribution. This paper gives a general overview of the GLOWA-Danube project and describes the groundwater modeling segment. Nickel et al. deal with the water supply model in a second contribution to this special issue. A three-dimensional numerical groundwater flow model consisting of four main layers has been developed and is in a continual state of refinement (MODFLOW, [McDonald, M.G., Harbaugh, A.W., 1988. A modular three-dimensional finite-difference ground-water flow model: US Geological Survey Techniques of Water-Resources Investigations, Washington, USA (book 6, Chapter A1)]). One main research focus has been on the investigation of upscaling techniques to meet the requirement of a fixed 1 × 1 km cell size. This cell size is compulsory for all models in DANUBIA in order to facilitate a one to one parameter exchange. In a second stage, a transport model (nitrogen) will be added (MT3D: [Zheng, C., Hathaway, D.-L., 1991. MT3D: a new modular three-dimensional transport model and its application in predicting the persistence and transport of dissolved compounds from a gasoline spill, with implications for remediation. Association of Ground Water Scientists and Engineers Annual Meeting on Innovative Ground Water Technologies for the '90s, National Ground Water Association, Westerville, Ohio, USA. Ground Water 29 (5)]. © 2005 Elsevier Ltd. All rights reserved."
"7004540083;7601318782;23502460300;","A statistical model of cloud vertical structure based on reconciling cloud layer amounts inferred from satellites and radiosonde humidity profiles",2005,"10.1175/JCLI3479.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344432165&doi=10.1175%2fJCLI3479.1&partnerID=40&md5=4a2d86dae9f31b363389bb1307bc4970","To diagnose how cloud processes feed back on weather- and climate-scale variations of the atmosphere requires determining the changes that clouds produce in the atmospheric diabatic heating by radiation and precipitation at the same scales of variation. In particular, not only the magnitude of these changes must be quantified but also their correlation with atmospheric temperature variations; hence, the space-time resolution of the cloud perturbations must be sufficient to account for the majority of these variations. Although extensive new global cloud and radiative flux datasets have recently become available, the vertical profiles of clouds and consequent radiative flux divergence have not been systematically measured covering weather-scale variations from about 100 km, 3 h up to climate-scale variations of 10 000 km, decadal inclusive. By combining the statistics of cloud layer occurrence from the International Satellite Cloud Climatology Project (ISCCP) and an analysis of radiosonde humidity profiles, a statistical model has been developed that associates each cloud type, recognizable from satellite measurements, with a particular cloud vertical structure. Application of this model to the ISCCP cloud layer amounts produces estimates of low-level cloud amounts and average cloud-base pressures that are quantitatively closer to observations based on surface weather observations, capturing the variations with latitude and season and land and ocean (results are less good in the polar regions). The main advantage of this statistical model is that the correlations of cloud vertical structure with meteorology are qualitatively similar to ""classical"" information relating cloud properties to weather. These results can be evaluated and improved with the advent of satellites that can directly probe cloud vertical structures over the globe, providing statistics with changing meteorological conditions. © 2005 American Meteorological Society."
"7202948585;7401491382;6701561683;7003900064;","Surface albedo of the Antarctic sea ice zone",2005,"10.1175/JCLI3489.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344453363&doi=10.1175%2fJCLI3489.1&partnerID=40&md5=5e1d5c53341d71fb5ac3f886facc43f1","In three ship-based field experiments, spectral albedos were measured at ultraviolet, visible, and near-infrared wavelengths for open water, grease ice, nilas, young ""grey"" ice, young grey-white ice, and first-year ice, both with and without snow cover. From the spectral measurements, broadband albedos are computed for clear and cloudy sky, for the total solar spectrum as well as for visible and near-infrared bands used in climate models, and for Advanced Very High Resolution Radiometer (AVHRR) solar channels. The all-wave albedos vary from 0.07 for open water to 0.87 for thick snow-covered ice under cloud. The frequency distribution of ice types and snow coverage in all seasons is available from the project on Antarctic Sea Ice Processes and Climate (ASPeCt). The ASPeCt dataset contains routine hourly visual observations of sea ice from research and supply ships of several nations using a standard protocol, Ten thousand of these observations, separated by a minimum of 6 nautical miles along voyage tracks, are used together with the measured albedos for each ice type to assign an albedo to each visual observation, resulting in ""ice-only"" albedos as a function of latitude for each of five longitudinal sectors around Antarctica, for each of the four seasons. These ice albedos are combined with 13 yr of ice concentration estimates from satellite passive microwave measurements to obtain the geographical and seasonal variation of average surface albedo. Most of the Antarctic sea ice is snow covered, even in summer, so the main determinant of area-averaged albedo is the fraction of open water within the pack. © 2005 American Meteorological Society."
"6507815511;7003467276;","Optimizing parameters in an atmospheric general circulation model",2005,"10.1175/JCLI3430.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344437849&doi=10.1175%2fJCLI3430.1&partnerID=40&md5=5a8895b37fba4c1b3f4ffd834152cc69","An efficient method to optimize the parameter values of the subgrid parameterizations of an atmospheric general circulation model is described. The method is based on the downhill simplex minimization of a cost function computed from the difference between simulated and observed fields. It is used to find optimal values of the radiation and cloud-related parameters. The model error is reduced significantly within a limited number of iterations (about 250) of short integrations (5 yr). The method appears to be robust and finds the global minimum of the cost function. The radiation budget of the model improves considerably without violating the already well simulated general circulation. Different aspects of the general circulation, such as the Hadley and Walker cells improve, although they are not incorporated into the cost function. It is concluded that the method can be used to efficiently determine optimal parameters for general circulation models even when the model behavior has a strong nonlinear dependence on these parameters. © 2005 American Meteorological Society."
"7003908632;8902029800;","Sensitivity of an Arctic regional climate model to the horizontal resolution during winter: Implications for aerosol simulation",2005,"10.1002/joc.1205","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844525402&doi=10.1002%2fjoc.1205&partnerID=40&md5=be58ba74d165daffcaf3bc39519f4bc4","Our ability to properly simulate current climate and its future change depends upon the exactitude of the physical processes that are parameterized on the one hand, and on model configuration on the other hand. In this paper, we focus on the latter and investigate the effect of the horizontal grid resolution on the simulation of a month of January over the Arctic. A limited-area numerical climate model is used to simulate the month of January 1990 over a grid that includes the Arctic and sub-Arctic regions. Two grid resolutions are used: 50 km and 100 km. Results show that finer details appear for regional circulation, temperature, and humidity when increasing horizontal resolution. This is particularly true for continental and sea ice boundaries, which are much better resolved by high-resolution model simulations. The Canadian Archipelago and rivers in northern Russia appear to benefit the most from higher horizontal resolution. High-resolution simulations capture some frozen rivers and narrow straits between islands. Therefore, much colder surface air temperature is simulated over these areas. Precipitation is generally increased in those areas and over topography due to a better representation of surface heterogeneities when increasing resolution. Large-scale atmospheric circulation is substantially changed when horizontal resolution is increased. Feedback processes occur between surface air temperature change over heterogeneous surfaces and atmospheric circulation. High-resolution simulations develop a stronger polar vortex. The mean sea-level pressure increases over the western Arctic and Iceland and decreases over the eastern Arctic. This circulation leads to a substantial cooling of the eastern Arctic and enhanced synoptic activity over the Arctic associated with an intensification of the baroclinic zone. Aerosol mass loading, which is simulated explicitly in this model, is significantly altered by the grid resolution change with the largest differences in aerosol concentration over areas where precipitation and atmospheric circulation are the most affected. The implications of this sensitivity study to the evaluation of indirect radiative effects of anthropogenic aerosols are discussed. Copyright © 2005 Royal Meteorological Society."
"7404586141;","A study of winter human bioclimate in Hong Kong",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745713155&partnerID=40&md5=137d4b50b7322f48f0373ae59334c012","The clo index, a measure of comfort providing an indication of clothing requirements under a given set of atmospheric conditions, was employed to assess the winter human bioclimate in Hong Kong. Hourly clo values for 8 stations were computed using hourly air temperature, wind speed and cloud cover data from 1991 to 2000, and they were reduced and grouped into monthly and seasonal values. A zonal pattern of clo requirements was observed. It was discovered that the hilly terrain blocked the cool northerly air making the southern part of the territory having the lowest clo values. Comfortable and cool weather wears comprised about 50-60 percent of the time at various stations. A statistically significant decreasing trend of clo values was detected at the Hong Kong Observatory; and this was mainly associated with the effect of urbanization. © The International Journal of Meteorology."
"8349977900;6701378450;6602097544;57196499374;","Evaluation of a new cloud droplet activation parameterization with in situ data from CRYSTAL-FACE and CSTRIPE",2005,"10.1029/2004JD005703","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26444492556&doi=10.1029%2f2004JD005703&partnerID=40&md5=52491ca4e9c4e86ad6e99b570d5ec3ce","The accuracy of the 2003 prognostic, physically based aerosol activation parameterization of A. Nenes and J. H. Seinfeld (NS) with modifications introduced by C. Fountoukis and A. Nenes in 2005 (modified NS) is evaluated against extensive microphysical data sets collected on board the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft for cumuliform and stratiform clouds of marine and continental origin. The cumuliform cloud data were collected during NASA's Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE, Key West, Florida, July 2002), while the stratiform cloud data were gathered during Coastal Stratocumulus Imposed Perturbation Experiment (CSTRIPE, Monterey, California, July 2003). In situ data sets of aerosol size distribution, chemical composition, and updraft velocities are used as input for the NS parameterization, and the evaluation is carried out by comparing predicted cloud droplet number concentrations (CDNC) with observations. This is the first known study in which a prognostic cloud droplet activation parameterization has been evaluated against a wide range of observations. On average, predicted droplet concentration in adiabatic regions is within ∼20% of observations at the base of cumuliform clouds and ∼30% of observations at different altitudes throughout the stratiform clouds, all within experimental uncertainty. Furthermore, CDNC is well parameterized using either a single mean updraft velocity w̄ or by weighting droplet nucleation rates with a Gaussian probability density function of w. This study suggests that for nonprecipitating warm clouds of variable microphysics, aerosol composition, and size distribution the modified NS parameterization can accurately predict cloud droplet activation and can be successfully implemented for describing the aerosol activation process in global climate models. Copyright 2005 by the American Geophysical Union."
"55887389300;55887849100;22982762300;26658279600;24546705400;","Globally integrated-measurements of the earth's visible spectral albedo",2005,"10.1086/431420","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23844505875&doi=10.1086%2f431420&partnerID=40&md5=f97d5071d9772acf0c954bce8e7eea3e","We report spectroscopic observations of the earthshine reflected from the Moon. By applying our well-developed photometry methodology to spectroscopy, we are able to precisely determine the Earth's reflectance and its variation as a function of wavelength through a single night as the Earth rotates. These data imply that planned regular monitoring of earthshine spectra will yield valuable new inputs for climate models, which would be complementary to those from the more standard broadband measurements of satellite platforms. For our single night of reported observations, we find that Earth's albedo decreases sharply with wavelength from 500 to 600 nm, while being almost flat from 600 to 900 nm. The mean spectroscopic albedo over the visible is consistent with simultaneous broadband photometric measurements. Unlike previous reports, we find no evidence for either an appreciable ""red"" or ""vegetation"" edge in the Earth's spectral albedo, or for changes in this spectral region (700-740 nm) over the 40° of Earth's rotation covered by our observations. Whether or not the absence of a vegetation signature in disk-integrated observations of the Earth is a common feature awaits the analysis of more earthshine data and simultaneous satellite cloud maps at several seasons. If our result is confirmed, it would limit efforts to use the red edge as a probe for Earth-like extrasolar planets. Water vapor and molecular oxygen signals in the visible earthshine, and carbon dioxide and methane in the near-infrared, are more likely to be powerful probes."
"57193132723;7403174207;7403318365;","Evaluation of regional cloud feedbacks using single-column models",2005,"10.1029/2004JD005011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844433386&doi=10.1029%2f2004JD005011&partnerID=40&md5=2c641f31fe41b1ddd649da7bd4bc93e0","Cloud feedbacks in a warmer climate have not yet been constrained by models or observations. We present an approach that combines a general circulation model (GCM), single-column model (SCM), satellite and surface remote sensing data, and analysis product to infer regional cloud feedbacks and evaluate model simulations of them. The Atmospheric Radiation Measurement (ARM) Program Southern Great Plains (SGP) continuous forcing product, derived from a mesoscale analysis constrained by top-of-atmosphere and surface data, provides long-term advective forcing that links the models to the data. We drive an SCM with the continuous forcing for 10 cold season months in which synoptic forcing dominates the meteorology. Cloud feedbacks in midlatitude winter are primarily responses to changes in dynamical forcing. Thus we select times when observed advective forcing anomalies resemble doubled CO2 advective forcing changes in the parent GCM. For these times we construct cloud type anomaly histograms in the International Satellite Cloud Climatology Project and Active Remotely Sensed Cloud Locations data sets and simulated versions of these histograms in the SCM. Comparison of the SCM subset to GCM doubled CO2 cloud type changes tells us how relevant the selected times are to the GCM's cloud feedbacks, while comparisons of the SCM to the data tell us how well the model performs in these situations. The data suggest that in midlatitude winter, high thick clouds should increase while cirrus and low clouds decrease in upwelling regimes in a climate warming. Downwelling regime cloud feedbacks are dominated by changes in low clouds but are not as well constrained by the data. Copyright 2005 by the American Geophysical Union."
"57214899685;57203053317;57208121852;","A microphysical parameterization for convective clouds in the ECHAM5 climate model: Single-column model results evaluated at the Oklahoma Atmospheric Radiation Measurement Program site",2005,"10.1029/2004JD005128","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844487511&doi=10.1029%2f2004JD005128&partnerID=40&md5=ec99bc8fca1cf5532ca64c3e9107307e","The microphysical parameterization used for stratiform clouds in the ECHAM5 climate model is now extended for simulations of convective clouds. The performance of the newly implemented parameterization in simulating midlatitude continental summertime convective cloud systems is evaluated in this paper at the Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) site in Oklahoma using the single-column mode (SCM) of ECHAM5. Three ARM intensive operating periods (IOPs), including two summer ones and a late spring one, are used for the evaluation. Results show that the SCM simulated cloud cover fraction agrees well with observations. The SCM also captures most of the precipitation events. With the new microphysical parameterization, the model performs at least as well as with the original model setup in simulating almost all the fields examined in this study. Significant improvement is shown in the simulations of outgoing longwave radiation and net incoming solar radiation at the top of the atmosphere revealing the feasibility of the new parameterization. Sensitivity studies show that a 10-fold increase in cloud droplet number concentration significantly increases the simulated liquid water content. More interestingly, this increase in cloud droplet number leads to an increase in the total amount of precipitation in two of the three IOPs. Copyright 2005 by the American Geophysical Union."
"7201646465;7401776640;7201606127;7402064802;","Dynamical controls on sub-global climate model grid-scale cloud variability for Atmospheric Radiation Measurement Program (ARM) case 4",2005,"10.1029/2004JD005022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844446985&doi=10.1029%2f2004JD005022&partnerID=40&md5=5ed84d632ee86194c4821b9b948f16c3","Global climate models (GCMs) produce large errors in cloudiness and cloud radiative forcing when simulating midlatitude, synoptic-scale cloud systems. This is because they do not represent the subgrid-scale processes in these systems that create subgrid variability in cloud optical thickness and cloud top pressure. Improving GCM performance will require a better understanding of these controls on subgrid cloud variability. To begin addressing this issue, this paper uses a mesoscale model, the Regional Atmospheric Modeling System (RAMS), to simulate two case study synoptic storms with much higher resolution than is possible in a GCM. These storms were observed during the Atmospheric Radiation Measurement (ARM) Program's March 2000 Intensive Observing Period (IOP) in the U.S. southern Great Plains (SGP), otherwise knows as ARM case 4. We find that RAMS is able to capture the observed storm morphology, lifecycle, and vertical structure of the atmospheric dynamic and thermodynamic variables. RAMS is also able to capture the observed fine-scale vertical structure and temporal variation of the cloud field. Given this agreement with observations, we then characterize the model-simulated variability in cloudiness and other variables such as vertical velocity. In both storms, there is a high degree of spatial and temporal variability in the vertical motion field across multiple scales. The variability in above-boundary layer cloudiness is closely linked to this dynamical variability. This suggests that a parameterization for subgrid cloud water based on subgrid vertical velocity could be used to improve GCM simulations of midlatitude clouds. Copyright 2005 by the American Geophysical Union."
"55745955800;8859530100;7402064802;6701431208;35509639400;6701464294;57193132723;7005814217;7004364155;57203053317;7006783796;8937991200;57205867148;57208121852;35497573900;7201485519;56093699900;7401936984;7403318365;57214899685;","Comparing clouds and their seasonal variations in 10 atmospheric general circulation models with satellite measurements",2005,"10.1029/2004JD005021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844449617&doi=10.1029%2f2004JD005021&partnerID=40&md5=8793a116ce2772aedbe63274ae09a450","To assess the current status of climate models in simulating clouds, basic cloud climatologies from ten atmospheric general circulation models are compared with satellite measurements from the International Satellite Cloud Climatology Project (ISCCP) and the Clouds and Earth's Radiant Energy System (CERES) program. An ISCCP simulator is employed in all models to facilitate the comparison. Models simulated a four-fold difference in high-top clouds. There are also, however, large uncertainties in satellite high thin clouds to effectively constrain the models. The majority of models only simulated 30-40% of middle-top clouds in the ISCCP and CERES data sets. Half of the models underestimated low clouds, while none overestimated them at a statistically significant level. When stratified in the optical thickness ranges, the majority of the models simulated optically thick clouds more than twice the satellite observations. Most models, however, underestimated optically intermediate and thin clouds. Compensations of these clouds biases are used to explain the simulated longwave and shortwave cloud radiative forcing at the top of the atmosphere. Seasonal sensitivities of clouds are also analyzed to compare with observations. Models are shown to simulate seasonal variations better for high clouds than for low clouds. Latitudinal distribution of the seasonal variations correlate with satellite measurements at >0.9, 0.6-0.9, and -0.2-0.7 levels for high, middle, and low clouds, respectively. The seasonal sensitivities of cloud types are found to strongly depend on the basic cloud climatology in the models. Models that systematically underestimate middle clouds also underestimate seasonal variations, while those that overestimate optically thick clouds also overestimate their seasonal sensitivities. Possible causes of the systematic cloud biases in the models are discussed. Copyright 2005 by the American Geophysical Union."
"7201606127;7401776640;7201646465;7402064802;","Cluster analysis of cloud regimes and characteristics dynamics of midlatitude synoptic systems in observations and a model",2005,"10.1029/2004JD005027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844436233&doi=10.1029%2f2004JD005027&partnerID=40&md5=6ebca671e91b56508dc5b60939df93bf","Global climate models typically do not correctly simulate cloudiness associated with midlatitude synoptic systems because coarse grid spacing prevents them from resolving dynamics occurring at smaller scales and there exist no adequate parameterizations for the effects of these subgrid-scale dynamics. Comparison of modeled and observed cloud properties averaged over similar regimes (e.g., compositing) aids the diagnosis of simulation errors and identification of meteorological forcing responsible for producing particular cloud conditions. This study uses a k-means clustering algorithm to objectively classify satellite cloud scenes into distinct regimes based on grid box mean cloud fraction, cloud reflectivity, and cloud top pressure. The spatial domain is the densely instrumented southern Great Plains site of the Atmospheric Radiation Measurement Program, and the time period is the cool season months (November-March) of 1999-2001. As a complement to the satellite retrievals of cloud properties, lidar and cloud radar data are analyzed to examine the vertical structure of the cloud layers. Meteorological data from the constraint variational analysis is averaged for each cluster to provide insight on the large-scale dynamics and advective tendencies coincident with specific cloud types. Meteorological conditions associated with high and low subgrid spatial variability are also investigated for each cluster. Cloud outputs from a single-column model version of the GFDL AM2 atmospheric model forced with meteorological boundary conditions derived from observations and a numerical weather prediction model were compared to observations for each cluster in order to determine the accuracy with which the model reproduces attributes of specific cloud regimes. Copyright 2005 by the American Geophysical Union."
"23082420800;7003543851;","The sensitivity of the tropical-mean radiation budget",2005,"10.1175/JCLI3456.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26844475767&doi=10.1175%2fJCLI3456.1&partnerID=40&md5=390ce1eb9817516ceac39377ec231597","A key disagreement exists between global climate model (GCM) simulations and satellite observations of the decadal variability in the tropical-mean radiation budget. Measurements from the Earth Radiation Budget Experiment (ERBE) over the period 1984-2001 indicate a trend of increasing longwave emission and decreasing shortwave reflection that no GCM can currently reproduce. Motivated by these results, a series of model sensitivity experiments is performed to investigate hypotheses that have been advanced to explain this discrepancy. Specifically, the extent to which a strengthening of the Hadley circulation or a change in convective precipitation efficiency can alter the tropical-mean radiation budget is assessed. Results from both model sensitivity experiments and an empirical analysis of ERBE observations suggest that the tropical-mean radiation budget is remarkably insensitive to changes in the tropical circulation. The empirical estimate suggests that it would require at least a doubling in strength of the Hadley circulation in order to generate the observed decadal radiative flux changes. In contrast, rather small changes in a model's convective precipitation efficiency can generate changes comparable to those observed, provided that the precipitation efficiency lies near the upper end of its possible range. If, however, the precipitation efficiency of tropical convective systems is more moderate, the model experiments suggest that the climate would be rather insensitive to changes in its value. Further observations are necessary to constrain the potential effects of microphysics on the top-of-atmosphere radiation budget. © 2005 American Meteorological Society."
"8866821900;7403288995;7201504886;","What controls the mean depth of the PBL?",2005,"10.1175/JCLI3417.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26844552404&doi=10.1175%2fJCLI3417.1&partnerID=40&md5=25a2549afbd2a012a1971c5b92b84675","The depth of the planetary boundary layer (PBL) is a climatologically important quantity that has received little attention on regional to global scales. Here a 10-yr climatology of PBL depth from the University of California, Los Angeles (UCLA) atmospheric GCM is analyzed using the PBL mass budget. Based on the dominant physical processes, several PBL regimes are identified. These regimes tend to exhibit large-scale geographic organization. Locally generated buoyancy fluxes and static stability control PBL depth nearly everywhere, though convective mass flux has a large influence at tropical marine locations. Virtually all geographical variability in PBL depth can be linearly related to these quantities. While dry convective boundary layers dominate over land, stratocumulus-topped boundary layers are most common over ocean. This division of regimes leads to a dramatic land-sea contrast in PBL depth. Diurnal effects keep mean PBL depth over land shallow despite large daytime surface fluxes. The contrast arises because the large daily exchange of heat and mass between the PBL and free atmosphere over land is not present over the ocean, where mixing is accomplished by turbulent entrainment. Consistent treatment of remnant air from the deep, daytime PBL is necessary for proper representation of this diurnal behavior over land. Many locations exhibit seasonal shifts in PBL regime related to changes in PBL clouds. These shifts are controlled by seasonal variations in buoyancy flux and static stability. © 2005 American Meteorological Society."
"7004194999;7003927831;7004416203;7003977187;8140555300;7003777747;8263759800;7003800456;55684491100;7003614389;7005829052;","Aviation radiative forcing in 2000: An update on IPCC (1999)",2005,"10.1127/0941-2948/2005/0049","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30644473725&doi=10.1127%2f0941-2948%2f2005%2f0049&partnerID=40&md5=c3669ce0ab295da2da4d3996d5e13ec0","New estimates of the various contributions to the radiative forcing (RF) from aviation are presented, mainly based on results from the TRADEOFF project that update those of the Intergovernmental Panel on Climate Change (IPCC, 1999). The new estimate of the total RF from aviation for 2000 is approximately the same as that of the IPCC's estimate for 1992. This is mainly a consequence of the strongly reduced RF from contrails, which compensates the increase due to increased traffic from 1992 to 2000. The RF from other aviation-induced cirrus clouds might be as large as the present estimate of the total RF (without cirrus). However, our present knowledge on these aircraft-induced cirrus clouds is too poor to provide a reliable estimate of the associated RF. © Gebrüder Borntraeger, Berlin, Stuttgart 2005."
"35353151900;7202330299;","Effects of the vertical profiles of cloud droplets and ice particles on the visible and near-infrared radiative properties of mixed-phase stratocumulus clouds",2005,"10.2151/jmsj.83.471","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344449711&doi=10.2151%2fjmsj.83.471&partnerID=40&md5=a0aa06bbcd0f9f30512f82ee05d9106c","Such cloud radiative properties as reflectance, transmittance, and absorptance of mixed-phase clouds have been simulated for the stratocumulus cloud observed on 30 January 1999 within the Japanese Cloud and Climate Study (JACCS) program, in which simultaneous observations of the cloud microphysical and radiative properties were conducted. The stratocumulus cloud was in mixed-phased condition, and highly heterogeneous vertically and horizontally with different mixing ratios of liquid water droplets and ice particles. A vertically-homogeneous, plane-parallel mixed-phase cloud model could reproduce the observed visible (VIS; wavelength < 0.7 μm) band radiative properties, but it could not reproduce the near-infrared (NIR; > 0.7 μm) band radiative properties. A multi-layered, plane-parallel mixed-phase cloud model could consistently reproduce the observed VIS-band and NIR-band radiative properties within the measurement accuracy. It is found that the vertical profiles of water droplets and ice particles are an important factor to determine the radiative properties of mixed-phase clouds. The simulated results suggested that the NIR-band reflectance and absorptance could vary by more than 0.1 due to different vertical distributions of the cloud microphysical properties even the model clouds had constant liquid-water-path and ice-water-path. The visible and near-infrared solar reflection can be also affected by the vertical profiles of cloud microphysical properties; it is suggested that the conventional passive remote sensing under the assumption of vertical-homogeneity, may bring large errors in estimation of the microphysical properties of mixed-phase clouds. © 2005, Meteorological Society of Japan."
"8696318000;57211634168;","Large-scale changes in the cloud radiative forcing over the Indian region",2005,"10.1016/j.atmosenv.2005.03.051","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23744483522&doi=10.1016%2fj.atmosenv.2005.03.051&partnerID=40&md5=e427092226143f0c67ba05b73caae255","Based on earth radiation budget experiment (ERBE) data, earlier studies have shown that in tropical deep-convective regions there is a near cancellation between shortwave and longwave cloud radiative forcing and El Nino event affects the cloud radiative forcing in the Pacific Ocean. The present study investigates these features over the Indian region (0-30°N, 60-120°E) in the peak monsoon month July, (being a representative month of the southwest monsoon season) using satellite measurements of ERBE and International Satellite Cloud Climatology Project (ISCCP) cloud data during the period 1985-1989. It has been observed from the study that a unique imbalance is seen between shortwave cloud radiative forcing (SWCRF) and longwave cloud radiative forcing (LWCRF). It is found to be prominent when the magnitude of LWCRF is higher than 50 W m-2. Net cloud radiative forcing (NCRF) is highly negative in the Indian region from Arabian sea to Indochina and near zero in the equatorial Indian Ocean. The ratio N, i.e., N=-SWCRF/LWCRF, is showing significantly higher values for all the years, the variation of observed N against SWCRF also shows higher values with SWCRF during average of 1985-1989, 1987 and 1988 because it is more than (N=∼1) that mentioned by Kiehl and Ramanathan (1990, Comparison of cloud forcing derived from the earth radiation budget experiment with that simulated by NCAR community climate model. Journal of Geophysical Research 95, 11679-11698) suggesting more imbalance between SWCRF and LWCRF and the lowering of the cloud top pressure particularly in 1987. Cloud radiative forcing (CRF) components are undergoing year-to-year variability with maximum magnitude in 1988 and minimum in 1987 similar to rainfall variation over the region, indicating an association between monsoon rainfall activity and CRF. Large-scale reduction occurred in the magnitudes of CRF and cloud physical properties in the Arabian Sea and south Bay of Bengal especially in 1987, and NCEP/NCAR-vertical velocity for 700 h Pa is also found considerably weak in 1987 in the Arabian Sea and Bay of Bengal i.e., the reduction in the vertical velocity might have affected the cloud formation and their vertical growth and ultimately changed the CRF. We attribute this reduction to the anomalous subsidence associated with the 1987 El Nino event. © 2005 Elsevier Ltd. All rights reserved."
"7202962414;7004899626;7202899330;","An assessment of the parameterization of subgrid-scale cloud effects on radiative transfer. Part II: Horizontal inhomogeneity",2005,"10.1175/JAS3498.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26244450817&doi=10.1175%2fJAS3498.1&partnerID=40&md5=f01206a6422591935fb8154d9a278261","The role of horizontal inhomogeneity in radiative transfer through cloud fields is investigated within the context of the two-stream approximation. Spatial correlations between cloud optical properties and the radiance field are introduced in the three-dimensional radiative transfer equation and lead to a two-stream model in which the correlations are represented by parameterizations. The behavior of the model is examined using simple single-layer single-column atmospheres. Positive correlations between extinction or scattering and the radiance field are shown to decrease transmission, increase reflection, and increase absorption within inhomogeneous media. The parameterization is used to evaluate the characteristics of inhomogeneous cloud fields observed by radar and lidar over a number of different locations and seasons, revealing that shortwave transfer is generally characterized by negative correlations between extinction and radiance, while longwave transfer is characterized by positive correlations. The results from this characterization are applied to the integration of an atmospheric general circulation model. Model surface temperatures are significantly affected, largely in response to changes in downwelling radiative fluxes at the surface induced by changes in cloud cover and water vapor distributions. © 2005 American Meteorological Society."
"7004590414;7005035462;","Global microwave satellite observations of sea surface temperature for numerical weather prediction and climate research",2005,"10.1175/BAMS-86-8-1097","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23944519657&doi=10.1175%2fBAMS-86-8-1097&partnerID=40&md5=dec126e51e804b96f8be67de418ccc50","Obtaining global sea surface temperature (SST) fields for the ocean boundary condition in numerical weather prediction (NWP) models and for climate research has long been problematic. Historically, such fields have been constructed by a blendig of in situ observations from ships and buoys and satellite infrared observations from the Advanced Vey High Resolution Radiometer (AVHRR) that has been operational on NOAA satellites since November 1981. The resolution of these global SST fields is limited by the sparse coverage of in situ observation in many areas of the World Ocean and cloud contamination of AVHRR observations, which can exceed 75% over the subpolar oceans. As clouds and aerosols are essential transparent to microwave radiation, satellite microwave observation can grealty improve the sampling and resolution of global SST fields. The Advance Microwave Scanning Radiometer on the NASA Earth Observation System (EOS) Aqua satellite (AMST-E) is providing the first hihly accurate and global satellite microwave observations of SST. The potentail for AMSR-E observation to improved the sampling, resolution, and accuracy of SST fields for NWP and climate research is demonstrated from example SST fields and from an investigation of the sensitivity of NWP models to specification of the SST boundary conditio of the SST boundary condition. © 2005 American Metereological Society."
"55717074000;7102604282;","Ice nucleation parameterization for global models",2005,"10.1127/0941-2948/2005/0059","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646032754&doi=10.1127%2f0941-2948%2f2005%2f0059&partnerID=40&md5=1a37a547002fe41c88256dcd318da6df","Global modeling of ice clouds and the effects of aerosol-related ice nuclei (IN) changes on clouds and climate remains a significant challenge. Here, we describe a parameterization that accounts for the effects of homogeneous ice nucleation as well as two different modes of heterogeneous nucleation in the upper troposphere. The parameterization treats homogeneous nucleation by sulfate aerosol, deposition nucleation as described by the Meyers et al. (1992) formulation, and immersion nucleation by soot aerosol. Besides air mass temperature and updraft velocity, number concentration of pure sulfate aerosol acting through homogeneous ice nucleation and number concentration of soot aerosol as heterogeneous ice nuclei are explicitly included in the parameterization so that the indirect effect of aerosols on the cirrus clouds (i.e. the effect of increases in aerosol number concentrations) can be described in a global model. In addition the transition from the heterogeneous to homogeneous-dominated nucleation and the competition between homogeneous and heterogeneous nucleation in the transition regime are considered in the parameterization. The parameterization is compared to the results from air parcel model simulations of uplifting and adiabatically cooling clouds and to other recently developed ice nucleation parameterizations. © Gebrüder Borntraeger, Berlin, Stuttgart 2005."
"35509639400;7006184606;","On the role of moist processes in tropical intraseasonal variability: Cloud-radiation and moisture-convection feedbacks",2005,"10.1175/JAS3506.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26244449283&doi=10.1175%2fJAS3506.1&partnerID=40&md5=c2e16a321f39f93afb2f5210d356112a","Recent observations of the tropical atmosphere reveal large variations of water vapor and clouds at intraseasonal time scales. This study investigates the role of these variations in the large-scale organization of the tropical atmosphere, and in intraseasonal variability in particular. For this purpose, the influence of feedbacks between moisture (water vapor, clouds), radiation, and convection that affect the growth rate and the phase speed of unstable modes of the tropical atmosphere is investigated. Results from a simple linear model suggest that interactions between moisture and tropospheric radiative cooling, referred to as moist-radiative feedbacks, play a significant role in tropical intraseasonal variability. Their primary effect is to reduce the phase speed of large-scale tropical disturbances: by cooling the atmosphere less efficiently during the rising phase of the oscillations (when the atmosphere is moister) than during episodes of large-scale subsidence (when the atmosphere is drier), the atmospheric radiative heating reduces the effective stratification felt by propagating waves and slows down their propagation. In the presence of significant moist-radiative feedbacks, planetary disturbances are characterized by an approximately constant frequency. In addition, moist-radiative feedbacks excite small-scale disturbances advected by the mean flow. The interactions between moisture and convection exert a selective damping effect upon small-scale disturbances, thereby favoring large-scale propagating waves at the expense of small-scale advective disturbances. They also weaken the ability of radiative processes to slow down the propagation of planetary-scale disturbances. This study suggests that a deficient simulation of cloud radiative interactions or of convection-moisture interactions may explain some of the difficulties experienced by general circulation models in simulating tropical intraseasonal oscillations. © 2005 American Meteorological Society."
"6602403713;7404764644;6701382162;7004698443;","Validation of GOES-based insolation estimates using data from the U.S. Climate Reference Network",2005,"10.1175/JHM440.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26444519262&doi=10.1175%2fJHM440.1&partnerID=40&md5=7d6cb91a7a5011d2f215f811e6cc8be0","Reliable procedures that accurately map surface insolation over large domains at high spatial and temporal resolution are a great benefit for making the predictions of potential and actual evapotranspiration that are required by a variety of hydrological and agricultural applications. Here, estimates of hourly and daily integrated insolation at 20-km resolution, based on Geostationary Operational Environmental Satellite (GOES) visible imagery are compared to pyranometer measurements made at 11 sites in the U.S. Climate Reference Network (USCRN) over a continuous 15-month period. Such a comprehensive survey is necessary in order to examine the accuracy of the satellite insolation estimates over a diverse range of seasons and land surface types. The relatively simple physical model of insolation that is tested here yields good results, with seasonally averaged model errors of 62 (19%) and 15 (10%) W m-2 for hourly and daily-averaged insolation, respectively, including both clear- and cloudy-sky conditions. This level of accuracy is comparable, or superior, to results that have been obtained with more complex models of atmospheric radiative transfer. Model performance can be improved in the future by addressing a small elevation-related bias in the physical model, which is likely the result of inaccurate model precipitable water inputs or cloud-height assessments. © 2005 American Meteorological Society."
"57203048291;57191693467;","Land surface model development for the GISS GCM: Effects of improved canopy physiology on simulated climate",2005,"10.1175/JCLI3425.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25444530916&doi=10.1175%2fJCLI3425.1&partnerID=40&md5=69ba7b7db093a6208d57f18e7946d670","A new physiology-based model of canopy stomatal conductance and photosynthesis is described and included in the latest version of the Goddard Institute for Space Studies (GISS) GCM, ModelE1. The submodel includes responses to atmospheric humidity and CO2 concentration, responses missing from previous GISS GCM land surface schemes. Measurements of moisture, energy, and CO2 fluxes over four vegetation types are used to test and calibrate the submodel. Photosynthetic leaf N is calibrated for each vegetation type from the flux measurements. The new submodel results in surface cooling over many regions previously too warm. Some warm biases of over 2°C are cooled by more than 0.5°C, including over central Eurasia, South America, the western United States, and Australia. In addition, some regions that were previously too cool are warmed, such as northern Eurasia and the Tibetan Plateau. A number of precipitation biases are also reduced, particularly over South America (by up to 1 mm, day-1) and the oceanic ITCZs (by over ±1 mm day-1); coastal west Africa becomes significantly wetter. Cloud cover increases over many land areas previously too clear. Higher absolute canopy conductances, and positive feedbacks with atmospheric humidity, are largely responsible for the simulated vegetation influence on the atmosphere. High-latitude climate changes through remote effects of increased tropical latent heating, resulting directly from improved characterization of tropical forest canopy conductance. Realistic representation of the stomatal control on land evaporation is critical for accurate simulation of atmospheric dynamics in the GISS GCM. © 2005 American Meteorological Society."
"6602332696;6602831555;55231746500;7003535176;","An upgraded estimate of the radiative forcing of cryoplane contrails",2005,"10.1127/0941-2948/2005/0057","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24144471608&doi=10.1127%2f0941-2948%2f2005%2f0057&partnerID=40&md5=adfe483f4125d3550ed2222a984f80e8","The radiative forcing of contrails is quantified for a hypothetical fleet of cryoplanes in comparison with a conventional aircraft fleet. The differences in bulk optical properties between conventional and cryoplane contrails are determined by numerical simulations of the microphysical evolution of conventional and cryoplane contrails, under several ambient conditions. Both types of contrails contain about the same ice mass, but the mean effective particle radius is found to be smaller by about a factor of 0.3 in conventional contrails than in cryoplane ones. Hence, in case of cryoplanes the contrail optical depth is lower, which counteracts (with respect to radiative forcing) the effect of increased contrail cover due to the higher specific emission of water vapour. If the information gained from the microphysical simulations is translated to the framework of a global climate model, the global mean radiative forcing of cryoplane contrails is simulated to be between about 30% lower and 30% higher compared to the radiative forcing of conventional contrails, depending on the quantitative assumptions made for the mean particle properties and also depending on the time slice considered. Our results indicate that the effect of decreased optical depth is about the same magnitude as the effect of increased contrail cover. Current state of knowledge does not allow a conclusive assessment whether the net radiative impact of cryoplane contrails will be smaller or larger than that of conventional contrails. Uncertainty with respect to radiative forcing arises mainly from insufficient knowledge regarding the mean effective ice crystal radius for both conventional and, especially, cryoplane contrails. © Gebrüder Borntraeger, Berlin, Stuttgart 2005."
"7004697990;8713556400;7102063963;6601976847;26643530600;57192956394;","Introducing the next-generation advanced baseline imager on GOES-R",2005,"10.1175/BAMS-86-8-1079","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23944500566&doi=10.1175%2fBAMS-86-8-1079&partnerID=40&md5=19fe3abb793a48bffe54f6d7e4f59019","The advanced Baseline Imager (ABI), designated to be one of the instruments on a future Geostationary Operational Environmental Satellite (GOES) series, will introduce a new era for U.S. geostationary environmental remote sensing. ABI is slated to be launched on GOES-R in 2012 and will be used for a wide range of weather, oceanographic, climate, and environmental applications. ABI will have more spectral bands (16), faster imaging (enabling more geographical areas to be scanned), and higher spatial resolution (2 km in the infrared and 1-0.5 km in the visible) than the current GOES Imager. The purposes of the selected spectral bands are summarized in this paper. There will also be improved performance with regard to radiometrics and image navigation/ registration. ABI will improve all current GOES Imager products and introduce a host of new products. New capabilities will include detecting upper-level SO2 plumes, monitoring plant health on a diurnal time scale, inferring cloud-top phase and particle size and other microphysical properties, and quantifying air quality with improved aerosol and smoke detection. ABI will be operating in concert with the GOES-R high spectral resolution sounder, part of the Hyperspectral Environmental Suite (HES); several products will be improved through the combination of high spatial resolution imager data with collocated high spectral resolution measurements. This paper introduces the proposed ABI spectral bands, discusses the rationale for their selection, and presents simulated ABI examples gleaned from current airborne and satellite instrument data. © 2005 American Meteorological Society."
"13406672500;57196817178;","Persistent, widespread, and strongly absorbing haze over the Himalayan foothills and the Indo-Gangetic Plains",2005,"10.1007/s00024-005-2685-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22144483065&doi=10.1007%2fs00024-005-2685-8&partnerID=40&md5=b232667ae0a5149ce07f9b132b4284c9","We examine the impact of the Atmospheric Brown Clouds on the direct radiative forcing of the Himalayan foothills and the Indo-Gangetic Plains (IGP) regions, home for over 500 million S. Asians. The NASA-Terra MODIS satellite data reveal an extensive layer of aerosols covering the entire IGP and Himalayan foothills region with seasonal mean AODs of about 0.4 to 0.5 in the visible wavelengths (0.55 micron), which fall among the largest seasonal mean dry season AODs for the tropics. We show new surface data which reveal the presence of strongly absorbing aerosols that lead to a large reduction in solar radiation fluxes at the surface during the October to May period. The three-year mean (2001 to 2003) October to May seasonal and diurnal average reduction in surface solar radiation for the IGP region is about 32 (±5) W m-2 (about 10% of TOA insolation or 20% of surface insolation). The forcing efficiency (forcing per unit optical depth) is as large as -27% (note that the forcing is negative) of top-of-atmosphere (TOA) solar insolation, and exceeds the forcing efficiency that has been observed for other polluted regions in America, Africa, East Asia, and Europe. General circulation model sensitivity studies suggest that both the local and remote influence of the aerosol induced radiative forcing is to strengthen the lower atmosphere inversion, stabilize the boundary layer, amplify the climatological tendency for a drier troposphere, and decrease evaporation. These aerosol-induced changes could potentially increase the life times of aerosols, make them more persistent, and decrease their single scattering albedos, thus potentially leading to a detrimental positive feedback between aerosol concentrations, aerosol forcing, and aerosol persistence. In addition, both the model studies and observations of pan evaporation suggest that the reduction in surface solar radiation may have led to a reduction in surface evaporation of moisture. These results suggest the vulnerability of this vital region to air pollution related direct and indirect (through climate changes) impacts on agricultural productivity of the region. © Birkhäuser Verlag, Basel, 2005."
"8832995400;16403070500;7202313091;","Numerical experiments on cloud streets in the lee of island arcs during cold-air outbreaks",2005,"10.1029/2005GL023256","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25444512431&doi=10.1029%2f2005GL023256&partnerID=40&md5=a950bc0d1e8fc71b86b12d1b8df9dbe4","Numerous clouds streets often appear in the lee of island arcs during cold-air outbreak. These clouds are quite similar each other in shape and appearance. We found that two different kinds of cloud streets are coexistent in them, one is formed by a mountain and another is formed by the temperature contrast between islands and the sea. Since difference in the characteristics between them is small, it is difficult to simply discriminate by satellite images. However, two kinds of the cloud streets can be observationally classified by the statistics of the satellite images with the help of numerical experiments. Copyright 2005 by the American Geophysical Union."
"26643041500;23995325300;8705440100;7003984086;35461255500;","Direct observational evidence linking atmospheric aerosol formation and cloud droplet activation",2005,"10.1029/2005GL023130","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25444471344&doi=10.1029%2f2005GL023130&partnerID=40&md5=ded0cf3f4cd4528df4dd8b68a01b89b0","In order to predict the current state and future development of the Earth's climate system, detailed knowledge on how atmospheric aerosol particles from various sources interact with clouds is needed. In this article we present, based on continuous aerosol measurements in a remote continental location, direct observational evidence that aerosol particles formed in the atmosphere from gaseous precursors eventually participate into cloud droplet activation. By combining the measurement data with theoretical calculations, we further demonstrate that the albedo of clouds may be significantly influenced by atmospheric aerosol formation, and that this process needs to be taken into account when estimating the indirect climatic effects of aerosols in the global atmosphere. Copyright 2005 by the American Geophysical Union."
"7103246957;7003994238;","Land-surface, boundary layer, and cloud-field coupling over the southwestern Amazon in ERA-40",2005,"10.1029/2004JD005702","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24944582827&doi=10.1029%2f2004JD005702&partnerID=40&md5=7996ae1d27f40af0282e572c65f63e47","Models are powerful tools for understanding the coupling of physical processes. We illustrate this using averages from ERA-40 for the Madeira River, a southwestern basin of the Amazon, which has a large seasonal cycle with a dry season in the austral winter. Daily-mean land-surface fluxes and state variables can be used to map the transitions of the surface ""climate"" of a model and to quantify the links between the soil moisture, the mean cloud-base and cloud field, the shortwave and longwave radiation fields at the surface, the vertical motion field, the atmospheric precipitable water, and the surface precipitation. The links that are visible on a daily timescale can also be seen on the seasonal timescale. Several important surface processes are strongly influenced by soil moisture: relative humidity, which gives the mixed subcloud layer depth, low cloud cover, and the surface net long-wave flux. The link between soil moisture and equivalent potential temperature can therefore be clearly seen once the temperature dependence is filtered. Surface evaporation is controlled as much by the feedback of the cloud field on the surface radiation budget as by soil moisture. Above the surface the cloud field and precipitation are coupled to the large-scale dynamics, specifically the midtropospheric omega field. The shortwave cloud forcing of the atmosphere and the surface is given by the cloud field albedo at the top of the atmosphere to better than 1%. We have developed a new methodology for understanding the coupling and feedbacks between physical processes in models, so that different models can be compared with each other and with data. Copyright 2005 by the American Geophysical Union."
"7501855361;16637291100;","Arctic surface, cloud, and radiation properties based on the AVHRR polar pathfinder dataset. Part II: Recent trends",2005,"10.1175/JCLI3439.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26844516613&doi=10.1175%2fJCLI3439.1&partnerID=40&md5=104f561231cdbab4f64678be377b16a5","Over the past 20 yr, some Arctic surface and cloud properties have changed significantly. Results of an analysis of satellite data show that the Arctic has warmed and become cloudier in spring and summer but has cooled and become less cloudy in winter. The annual rate of surface temperature change is 0.057°C for the Arctic region north of 60°N. The surface broadband albedo has decreased significantly in autumn, especially over the Arctic Ocean, indicating a later freeze-up and snowfall. The surface albedo has decreased at an annual rate of -0.15% (absolute). Cloud fraction has decreased at an annual rate of -0.6% (absolute) in winter and increased at annual rates of 0.32% and 0.16% in spring and summer, respectively. On an annual time scale, there is no trend in cloud fraction. During spring and summer, changes in sea ice albedo that result from surface warming tend to modulate the radiative effect of increasing cloud cover. On an annual time scale, the all-wave cloud forcing at the surface has decreased at an annual rate of -0.335 W m-2, indicating an increased cooling by clouds. There are large correlations between surface temperature anomalies and climate indices such as the Arctic Oscillation (AO) index for some areas, implying linkages between global climate change and Arctic climate change. © 2005 American Meteorological Society."
"7501855361;16637291100;","Arctic surface, cloud, and radiation properties based on the AVHRR polar pathfinder dataset. Part I: Spatial and temporal characteristics",2005,"10.1175/JCLI3438.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26844444159&doi=10.1175%2fJCLI3438.1&partnerID=40&md5=508e8c9dc0712d4f70d0c2259c770d9c","With broad spectral coverage and high spatial and temporal resolutions, satellite sensors can provide the data needed for the analysis of spatial and temporal variations of climate parameters in data-sparse regions such as the Arctic and Antarctic. The newly available Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder (APP) dataset was used to retrieve cloud fraction, cloud optical depth, cloud particle phase and size, cloud-top pressure and temperature, surface skin temperature, surface broadband albedo, radiative fluxes, and cloud forcing over the Arctic Ocean and surrounding landmasses for the 18-yr period from 1982 to 1999. In the Arctic, Greenland is the coldest region with the highest surface albedo, while northeastern Russia has the highest surface temperature in summer. Arctic annual mean cloud coverage is about 70%, with the largest cloudiness occurring in September and the lowest cloudiness occurring in April. On annual average, Arctic cloud visible optical depth is about 5-6. Arctic precipitable water is near 0.2 cm in winter and 1.5 cm in summer. The largest downwelling shortwave radiative flux at the surface occurs in June; the largest upwelling shortwave radiative flux occurs in May. The largest downwelling and upwelling longwave radiative fluxes as well as the net all-wave radiative flux occur in July, with the largest loss of longwave radiation from the surface in April. © 2005 American Meteorological Society."
"55837993200;7202970215;7101619974;55942854700;55437096000;","High clouds over oceans in the ECMWF 15- and 45-Yr reanalyses",2005,"10.1175/JCLI3429.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26844546224&doi=10.1175%2fJCLI3429.1&partnerID=40&md5=4aa6eeffb7a829d47e90d5f486862db5","The reanalysis programs of numerical weather prediction (NWT) centers provide global, comprehensive descriptions of the atmosphere and of the earth's surface over long periods of time. The high realism of their representation of key NWP parameters, like temperature and winds, implies some realism for less emblematic parameters, such as cloud cover, but the degree of this realism needs to be documented. This study aims to evaluate the high clouds over open oceans in the ECMWT 15- and 45-yr reanalyses. The assessment is based on a new 23-yr climatology of monthly frequencies of high-cloud occurrence retrieved from the infrared radiances measured by operational polar satellites. It is complemented by data from the International Satellite Cloud Climatology Project. It is shown that the 45-yr ECMWF reanalysis dramat ically improves on the previous 15-yr reanalysis for the realism of seasonal and interannual variations in high clouds, despite remaining systematic errors. More than 60% of the observed anomalies during the January 1979-February 2002 period over large oceanic basins are captured by the latest reanalysis. However the realism of the analyses in the areas and in the years with sparse observations appears to be poor. Consequently, the interannual variations may not be reliable before January 1979 in most parts of the world. Possible improvements of the handling of assimilated satellite observations before and after this date are suggested. © 2005 American Meteorological Society."
"8906042800;6603610266;","Sensitivity of the simulated monsoons of 1987 and 1988 to convective parameterization schemes in MM5",2005,"10.1175/JCLI3390.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26844507878&doi=10.1175%2fJCLI3390.1&partnerID=40&md5=e79337e24fc641e8b5a757192c13c880","In this study the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model (MM5) version 3.5.2 was used to simulate the Indian summer monsoon during the two contrasting years of 1987 and 1988, a dry year and a wet year, respectively. Three different convection parameterization schemes of Betts-Miller-Janjic, Kain-Fritsch, and Grell were used to study the sensitivity of monsoon to cumulus effects. The model was integrated for a period of 6 months, starting from three different initial conditions of 0000 UTC on 1, 2, and 3 May of each year using the NCEP-NCAR reanalysis data as input. The 6-hourly reanalysis data were used to provide the lateral boundary conditions, and the observed weekly Reynolds sea surface temperature, linearly interpolated to 6 h, was used as the lower boundary forcing. The results show that all three cumulus schemes were able to simulate the interannual and intraseasonal variabilities in the monsoon with reasonable accuracy. However, the spatial distribution of the rainfall and its quantity were different in all the schemes. The Grell scheme underestimated the rainfall in both the years. The Kain-Fritsch scheme simulated the observed rainfall well during July and August, the peak monsoon months, of the year 1988 but overestimated the rainfall in June and September of 1988 and throughout the monsoon season of 1987. The Betts-Miller-Janjic scheme simulated less rainfall in the drought year of 1987 and overestimated the rainfall in June and July of 1988. The circulation patterns simulated by the Betts-Miller-Janjic and Kain-Fritsch schemes are comparable to the observed patterns. © 2005 American Meteorological Society."
"57193132723;6507993848;7403318365;16304488000;","Cumulus microphysics and climate sensitivity",2005,"10.1175/JCLI3413.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844503623&doi=10.1175%2fJCLI3413.1&partnerID=40&md5=c36adb3f504b938b99d45ec43b488472","Precipitation processes in convective storms are potentially a major regulator of cloud feedback. An unresolved issue is how the partitioning of convective condensate between precipitation-size particles that fall out of updrafts and smaller particles that are detrained to form anvil clouds will change as the climate warms. Tropical Rainfall Measuring Mission (TRMM) observations of tropical oceanic convective storms indicate higher precipitation efficiency at warmer sea surface temperature (SST) but also suggest that cumulus anvil sizes, albedos, and ice water paths become insensitive to warming at high temperatures. International Satellite Cloud Climatology Project (ISCCP) data show that instantaneous cirrus and deep convective cloud fractions are positively correlated and increase with SST except at the highest temperatures, but are sensitive to variations in large-scale vertical velocity. A simple conceptual model based on a Marshall-Palmer drop size distribution, empirical terminal velocity-particle size relationships, and assumed cumulus updraft speeds reproduces the observed tendency for detrained condensate to approach a limiting value at high SST. These results suggest that the climatic behavior of observed tropical convective clouds is intermediate between the extremes required to support the thermostat and adaptive iris hypotheses."
"6508380559;","Climate change-driven forest fires marginalize the impact of ice cap wasting on Kilimanjaro",2005,"10.1111/j.1365-2486.2005.00968.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744526685&doi=10.1111%2fj.1365-2486.2005.00968.x&partnerID=40&md5=b737e460032a751a60b7aa7c922aa429","The disappearing glaciers of Kilimanjaro are attracting broad interest. Less conspicuous but ecologically far more significant is the associated increase of frequency and intensity of fires on the slopes of Kilimanjaro, which leads to a downward shift of the upper forest line by several hundred meters as a result of a drier (warmer) climate since the last century. In contrast to common belief, global warming does not necessarily cause upward migration of plants and animals. Here, it is shown that on Kilimanjaro the opposite trend is under way, with consequences more harmful than those due to the loss of the showy ice cap of Africa's highest mountain. © 2005 Blackwell Publishing Ltd."
"8871347500;7003922583;7006082600;","The impact of ice crystal shapes, size distributions, and spatial structures of cirrus clouds on solar radiative fluxes",2005,"10.1175/JAS3459.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344446510&doi=10.1175%2fJAS3459.1&partnerID=40&md5=e6bebf6ec0e411f1bcfcd61723645e8e","The solar radiative properties of cirrus clouds depend on ice particle shape, size, and orientation, as well as on the spatial cloud structure. Radiation schemes in atmospheric circulation models rely on estimates of cloud optical thickness only. In the present work, a Monte Carlo radiative transfer code is applied to various cirrus cloud scenarios to obtain the radiative response of uncertainties in the above-mentioned microphysical and spatial cloud properties (except orientation). First, plane-parallel homogeneous (0D) clouds with different crystal shapes (hexagonal columns, irregular polycrystals) and 114 different size distributions have been considered. The resulting variabilities in the solar radiative fluxes are in the order of a few percent for the reflected and about 1% for the diffusely transmitted fluxes. Largest variabilities in the order of 10% to 30% are found for the solar broadband absorptance. However, these variabilities are smaller than the flux differences caused by the choice of ice particle geometries. The influence of cloud inhomogeneities on the radiative fluxes has been examined with the help of time series of Raman lidar extinction coefficient profiles as input for the radiative transfer calculations. Significant differences between results for inhomogeneous and plane-parallel clouds were found. These differences are in the same order of magnitude as those arising from using extremely different crystal shapes for the radiative transfer calculations. From this sensitivity study, the ranking of cirrus cloud properties according to their importance in solar broadband radiative transfer is optical thickness, ice crystal shape, ice particle size, and spatial structure. © 2005 American Meteorological Society."
"7403282069;7403531523;7004325649;7202926455;7801693068;","Statistical analyses of satellite cloud object data from CERES. Part I: Methodology and preliminary results of the 1998 El Niño/2000 La Niña",2005,"10.1175/JCLI3418.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22944459670&doi=10.1175%2fJCLI3418.1&partnerID=40&md5=db0182c415419457c88db996692a1574","This study presents an objective classification methodology that uses Earth Observing System (EOS) satellite data to classify distinct ""cloud objects"" defined by cloud-system types, sizes, geographic locations, and matched large-scale environments. This analysis method identifies a cloud object as a contiguous region of the earth with a single dominant cloud-system type. It determines the shape and size of the cloud object from the satellite data and the cloud-system selection criteria. The statistical properties of the identified cloud objects are analyzed in terms of probability density functions (PDFs) based upon the Clouds and the Earth's Radiant Energy System (CERES) Single Satellite Footprint (SSF) data. Four distinct types of oceanic cloud objects - tropical dee p convection, boundary layer cumulus, transition stratocumulus, and solid stratus - are initially identified from the CERES data collected from the Tropical Rainfall Measuring Mission (TRMM) satellite for this study. Preliminary results are presented from the analysis of the grand-mean PDFs of these four distinct types of cloud objects associated with the strong 1997/98 El Niño in March 1998 and the very weak 2000 La Niña in March 2000. A majority of the CERES footprint statistical characteristics of observed tropical deep convection are similar between the two periods in spite of the climatological contrast. There are, however, statistically significant differences in some cloud macrophysical properties such as the cloud-top height and cloud-top pressure and moderately significant differences in outgoing longwave radiation (OLR), cloud-top temperature, and ice diameter. The footprint statistical characteristics of the three observed boundary layer cloud-system types are distinctly different from one another in all cloud microphysical, macrophysical, optical properties, and radiative fluxes. The differences between the two periods are not significant for most cloud microphysical and optical properties and the top-of-the-atmosphere albedo, but are statistically significant for some cloud macro-physical properties and OLR. These characteristics of the grand-mean PDFs of cloud microphysical, macrophysical, and optical properties and radiative fluxes can be usefully compared with cloud model simulations. Furthermore, the proportion of different boundary la yer cloud types is changed between the two periods in spite of small differences in their grand-mean statistical properties. An increase of the stratus population and a decrease of the cumulus population are evident in the El Niño period compared to the very weak La Niña period. The number of the largest tropical convective cloud objects is larger during the El Niño period, but the total number of tropical convective cloud objects is approximately the same in the two periods. © 2005 American Meteorological Society."
"8946494600;7102128820;7007114756;","Parameterizing the difference in cloud fraction defined by area and by volume as observed with radar and lidar",2005,"10.1175/JAS3467.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344438306&doi=10.1175%2fJAS3467.1&partnerID=40&md5=b6c1abe752b2580a4a9f6702306e35b1","Most current general circulation models (GCMs) calculate radiative fluxes through partially cloudy grid boxes by weighting clear and cloudy fluxes by the fractional area of cloud cover (Ca), but most GCM cloud schemes calculate cloud fraction as the volume of the grid box that is filled with cloud (Cv). In this paper, 1 yr of cloud radar and lidar observations from Chilbolton in southern England, are used to examine this discrepancy. With a vertical resolution of 300 m it is found that, on average, Ca is 20% greater than Cv, and with a vertical resolution of 1 km, Ca is greater than Cv by a factor of 2. The difference is around a factor 2 larger for liquid water clouds than for ice clouds, and also increases with wind shear. Using Ca rather than Cv, calculated on an operational model grid, increases the mean total cloud cover from 53% to 63%, and so is of similar importance to the cloud overlap assumption. A simple parameterization, Ca = [1 + e(-f)(Cv -1 - 1)]-1, is proposed to correct for this underestimate based on the observation that the observed relationship between the mean Ca and Cv is symmetric about the line Ca = 1 - Cv. The parameter f is a simple function of the horizontal (H) and vertical (V) grid-box dimensions, where for ice clouds f = 0.0880 V0.7696 H-0.2254 and for liquid clouds f = 0.1635 V0.6694 H-0.1882. Implementing this simple parame terization, which excludes the effect of wind shear, on an independent 6-month dataset of cloud radar and lidar observations, accounts for the mean underestimate of Ca for all horizontal and vertical resolutions considered to within 3% of the observed Ca, and reduces the rms error for each individual box from typically 100% to approximately 30%. Small biases remain for both weakly and strongly sheared cases, but this is significantly reduced by incorporating a simple shear dependence in the calculation of the parameter f, which also slightly improves the overall performance of the parameterization for all of the resolutions considered. © 2005 American Meteorological Society."
"7005877775;7402480218;8662493200;","Impact of island-induced clouds on surface measurements: Analysis of the ARM Nauru island effect study data",2005,"10.1175/JAM2241.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24644502355&doi=10.1175%2fJAM2241.1&partnerID=40&md5=8f7a55222b3d8a123399481d8c209024","An Atmospheric Radiation and Cloud Station (ARCS) was established on the island of Nauru by the Atmospheric Radiation Measurement (ARM) Program. Analysis of the Nauru99 field experiment data indicated that measurements at the ARCS were affected by a cloud plume that was induced by diurnal heating of the island. During the Nauru Island Effects Study, instrumentation was installed at a second site to develop criteria for identifying when the cloud plume occurs and to quantify its effect on ARCS measurements. The plume directional heading and frequency of occurrence are affected by the large-scale tropical circulation. During the present study, in which an El Niño was developing, Nauru was in a region of active convection, and easterly trade winds were not dominant; plumes were observed in 25% of satellite images, and only one-half of the observed plumes were downwind of the ARCS site. Surface wind direction, surface air temperature, and downwelling solar radiation at the two sites were used to identify periods when the cloud plume affected surface measurements. Differences in low-cloud frequency and surface radiation between plume-affected and non-plume-affected periods were examined. Existence of the cloud plume increased the average low-cloud frequency of occurrence from 20% to 35%, decreased the average downwelling shortwave radiation by 50-60 W m-2, and increased the average downwelling longwave radiation by 5-10 W m-2. Installing a suite of surface meteorological instruments and a global shortwave radiometer at a second site will allow for the long-term quantification of the cloud plume effect on the radiation field at the ARCS site. © 2005 American Meteorological Society."
"7103373860;","Seasonal variability in clouds and radiation at the Manus ARM site",2005,"10.1175/JCLI3401.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26844531253&doi=10.1175%2fJCLI3401.1&partnerID=40&md5=a3a38e32fdc37f50120e6d13a87e7d0f","The Atmospheric Radiation Measurement (ARM) program operates three climate observation stations in the tropical western Pacific region. One of these sites, located on Manus Island in Papua New Guinea, has been operating since 1996. The Manus ARM site includes an extensive array of instruments chosen to observe cloud properties, water vapor and temperature profiles, and the surface radiation budget. This dataset provides an opportunity to examine variability in tropical cloudiness on a wide range of time scales. The focus of this study is on the annual cycle. Analysis of cloud distribution and radiation data from Manus reveals a clear annual cycle in clouds associated with convective activity. The most convectively active period is found to be the Northern Hemisphere summer, while the least active period is the Northern Hemisphere autumn. Outgoing longwave radiation (OLR) data are also examined in order to relate observations at Manus with the surrounding region. Significant differences are found between the annual cycle at Manus and adjacent large islands within the Maritime Continent. Analysis of the combined ARM-OLR data suggests that during the Northern Hemisphere winter, a significant amount of the high clouds observed over Manus are associated with continental convection over the large Maritime Continent islands. © 2005 American Meteorological Society."
"8890895700;9241209700;55440359400;22234701000;","Surface heat balance and pan evaporation trends in Eastern Asia in the period 1971-2000",2005,"10.1002/hyp.5668","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22944443887&doi=10.1002%2fhyp.5668&partnerID=40&md5=7da079739009a73b30ab9e47c8cc7181","Climatic variations over Eastern Asia, including the Tibetan Plateau, were analysed using meteorological data for 32 points in the period 1971 to 2000. Changes in heat and water balances were examined using potential evaporation Ep, and a wetness index WI, as suggested by Kondo and Xu (1997a,b). Climate zones, including the humid, semi-humid, semi-arid and arid climate types, in Eastern Asia identified by the wetness index matched the vegetation distribution. Average monthly temperatures increased over the 30 years, with the sharpest increase in February. In general, temperature increases were larger in the north than in the south. Air temperature increased by more than 0·05 K yr-1 in northern China. The data showed that diurnal temperature ranges have decreased in recent years. From the Tibetan Plateau, through central China, to southern northeast China, there has been an increase in potential evaporation and pan evaporation, which may be related to both higher temperatures and a lack of surface water. Increasing long-wave radiation flux is apparent in every month and in the interannual trends. This is in contrast to the solar radiation flux. On the other hand, trends for relative humidity and cloud cover were negative, but positive for water vapour pressure. Copyright © 2005 John Wiley &amp; Sons, Ltd."
"6701346974;7202208382;6507017020;","Simulations of the atmospheric general circulation using a cloud-resolving model as a superparameterization of physical processes",2005,"10.1175/JAS3453.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20044395922&doi=10.1175%2fJAS3453.1&partnerID=40&md5=42814ce019d4377c802e58c31e838186","Traditionally, the effects of clouds in GCMs have been represented by semiempirical parameterizations. Recently, a cloud-resolving model (CRM) was embedded into each grid column of a realistic GCM, the NCAR Community Atmosphere Model (CAM), to serve as a superparameterization (SP) of clouds. Results of the standard CAM and the SP-CAM are contrasted, both using T42 resolution (2.8° × 2.8° grid), 26 vertical levels, and up to a 500-day-long simulation. The SP was based on a two-dimensional (2D) CRM with 64 grid columns and 24 levels collocated with the 24 lowest levels of CAM. In terms of the mean state, the SP-CAM produces quite reasonable geographical distributions of precipitation, precipitable water, top-of-the-atmosphere radiative fluxes, cloud radiative forcing, and high-cloud fraction for both December-January-February and June-July-August. The most notable and persistent precipitation bias in the western Pacific, during the Northern Hemisphere summer of all the SP-CAM runs with 2D SP, seems to go away through the use of a small-domain three-dimensional (3D) SP with the same number of grid columns as the 2D SP, but arranged in an 8 × 8 square with identical horizontal resolution of 4 km. Two runs with the 3D SP have been carried out, with and without explicit large-scale momentum transport by convection. Interestingly, the double ITCZ feature seems to go away in the run that includes momentum transport. The SP im proves the diurnal variability of nondrizzle precipitation frequency over the standard model by precipitating most frequently during late afternoon hours over the land, as observed, while the standard model maximizes its precipitation frequency around local solar noon. Over the ocean, both models precipitate most frequently in the early morning hours as observed. The SP model also reproduces the observed global distribution of the percentage of days with nondrizzle precipitation rather well. In contrast, the standard model tends to precipitate more frequently, on average by about 20%-30%. The SP model seems to improve the convective intraseasonal variability over the standard model. Preliminary results suggest that the SP produces more realistic variability of such fields as 200-mb wind and OLR, relative to the control, including the often poorly simulated Madden-Julian oscillation (MJO). © 2005 American Meteorological Society."
"7004561201;7006330182;","Humidity measurements in cold and humid environments",2005,"10.1007/s10546-004-7955-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22144475462&doi=10.1007%2fs10546-004-7955-y&partnerID=40&md5=56ee130ae80a359eada9ca6b703f21a4","Recent studies have shed new light on humidity conditions in the polar atmospheric boundary layer, and cast doubt on the reliability of humidity measurements above the frost point humidity. These issues are addressed herein by considering the processes that affect humidity and its measurement in cold climate conditions and by analyzing observations from two sites, at which the relative humidity is frequently above 100% at sub-freezing temperatures, as shown by repeatedly observed in-cloud icing events. Humidity measurements were made at these two sites by the commonly used Vaisala HMP35 probe and HMP233 capacitance probes respectively and simultaneously by the same manufacturer's HMP243 probe that determines the frost point by a heated capacitance sensor. The results confirm that the relative humidity is frequently well above the frost point, both due to radiative cooling and to the advection of moist air, and that the conventional humidity measurements are unable to detect these events. Furthermore, after such events, the iced sensors show too high a humidity. The false values occur due to ice growth on the probe and cannot be corrected by any algorithm. Our results indicate that these problems, inherent to conventional humidity measurements in cold and humid environments, are avoided by the use of HMP243, which has a heated humidity probe. © Springer 2005."
"7102717744;35395776600;7005848261;7402310115;","New real-time technique to measure the size distribution of water-insoluble aerosols",2005,"10.1021/es048366p","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22044437244&doi=10.1021%2fes048366p&partnerID=40&md5=51fa380710a1e766e31430771d7a3135","To date, there has been much research into the size distribution of ambient atmospheric aerosols, particularly either the total aerosol population or water-soluble ionic species such as sulfate or nitrate. Meanwhile, there have been virtually no size-resolved measurements of water-insoluble aerosols (WIA). This has been due to a lack of practical measurement technology rather than a reflection of the importance of WIA to climate and health. Particle solubility influences the planetary radiation balance both directly and indirectly: solubility influences both the amount of hygroscopic growth (and thus light scattering) that occurs as a function of relative humidity and the ability of particles to serve as cloud condensation nuclei (and thusthe lifetime and albedo of clouds). Also, recentinformation suggests that WIA may be harmful to human health. To address these concerns, a new real-time technique has been developed to measure the size-resolved concentration of WIA. This technique involves the entrainment of particles into a liquid stream and measurement of the WIA size distribution using a liquid optical particle counter. The time resolution of this instrumentation is approximately 4 min (depending on flow rate) and is capable of sizing and counting insoluble particles with diameters of 0.25-2.0 μm at atmospheric concentrations as low as 0.1 cm-3. Laboratory characterization using polystyrene latex spheres shows agreement within ±5% of the liquid stream and air stream particle concentrations when adjusted for flow rate. The instrumentation was field-tested at a rural site on the edge of the metro-Atlanta urban area. During this test, the WIA concentration averaged 5% of the total particle concentration between 0.25 and 2.0 μm but reached as high as 35%. © 2005 American Chemical Society."
"8647674600;8647673900;57176390100;57189218937;8647674200;8647674300;8322187000;7006194858;","African dust clouds are associated with increased paediatric asthma accident and emergency admissions on the Caribbean island of Trinidad",2005,"10.1007/s00484-005-0257-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23644457802&doi=10.1007%2fs00484-005-0257-3&partnerID=40&md5=01de48efbb30d61fd0245dbe8583f357","A retrospective ecological study of paediatric asthma patients who attended the Accident and Emergency (A&E) department of the Paediatric Priority Care Facility at the Eric Williams Medical Sciences Complex in relation to Saharan dust visibility and other climatic variables for the period 23 May 2001 to 13 May 2002 was undertaken to determine if there is an association between paediatric A&E asthma visits and Saharan dust cloud cover. A Poisson regression model was used to determine the statistical relationship between acute paediatric asthma A&E visits and Saharan dust cover with and without other variables such as climatic parameters and month. During the study period, there were 2,655 A&E visits for acute asthma. There was an association between increased paediatric asthma admissions and increased Saharan dust cover. The best fitting model estimated that in one month, such as June, a deterioration of visibility due to increased Saharan dust cover from no dust (visibility =16 km) to very dusty (visibility =7 km) would increase a daily admission rate of 7.8 patients to 9.25 when climate variables such as barometric pressure and humidity were kept constant. © ISB 2005."
"7005006917;9940013500;7003621869;7202305982;6701592812;6603108176;6602599215;7202155374;6603965708;","Coupling diffuse sky radiation and surface albedo",2005,"10.1175/JAS3479.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344441665&doi=10.1175%2fJAS3479.1&partnerID=40&md5=df10c8cd917221cd3cde053f0b1ac5cb","New satellite instruments have been delivering a wealth of information regarding land surface albedo. This basic quantity describes what fraction of solar radiation is reflected from the earth's surface. However, its concept and measurements have some ambiguity resulting from its dependence on the incidence angles of both the direct and diffuse solar radiation. At any time of day, a surface receives direct radiation in the direction of the sun, and diffuse radiation from the various other directions in which it may have been scattered by air molecules, aerosols, and cloud droplets. This contribution proposes a complete description of the distribution of incident radiation with angles, and the implications in terms of surface albedo are given in a mathematical form, which is suitable for climate models that require evaluating surface albedo many times. The different definitions of observed albedos are explained in terms of the coupling between surface and atmospheric scattering properties. The analytical development in this paper relates the various quantities that are retrieved from orbiting platforms to what is needed by an atmospheric model. It provides a physically simple and practical approach to evaluation of land surface albedo values at any condition of sun illumination irrespective of the current range of surface anisotropic conditions and atmospheric aerosol load. The numerical differences between the various definitions of albedo for a set of typical atmospheric and surface scattering conditions are illustrated through numerical computation. © 2005 American Meteorological Society."
"7403497924;7201753505;","A comparison of MODIS, NCEP, and TMI sea surface temperature datasets",2005,"10.1109/LGRS.2005.846838","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744515748&doi=10.1109%2fLGRS.2005.846838&partnerID=40&md5=38825312da5ad3e67f7d1e77fcde1200","The monthly average sea surface temperature (SST) datasets of MODIS (Moderate Resolution Imaging Spectrora-diometer), NCEP (National Center for Environmental Prediction) and TMI (Tropical Rainfall Measuring Mission (TRMM) Microwave Imager) are compared for the period March 2000 to June 2003. Large discrepancies (0.5 K- > 1 K) are found over extensive areas: the tropical Atlantic, tropical western Pacific, Bay of Bengal, Arabian Sea and the storm tracks. Many of these discrepancies are related to the biases inherent in the infrared and microwave retrieval methods. Probable causes for these biases include cirrus contamination, insufficient corrections for water vapor absorption and aerosol attenuation in infrared retrieval as well as uncertainty in surface emissivity in microwave retrieval. The SST difference patterns bear close resemblance to the patterns of distribution of aerosols, cirrus, atmospheric water vapor and surface wind speed at certain regions. Correlations between SST difference and aerosol optical depth, column water vapor and surface wind speed in some areas are high (>0.75). These biases have to be adjusted in order for the SST datasets to be more useful for climate studies. © 2005 IEEE."
"35614590000;6701551631;","Retention of chloride in soil and cycling of organic matter-bound chlorine",2005,"10.1002/hyp.5680","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22944484700&doi=10.1002%2fhyp.5680&partnerID=40&md5=edee00278c1767321a6e2b3ca231b17f","Chloride (Clinorg) is generally considered to be a hydrologically and chemically inert substance. Past research suggests that Clinorg participates in a complex biogeochemical cycle involving the formation of organically bound chlorine (Clorg). The present study examines whether Clorg cycling is sufficiently extensive as to influence the geochemical cycling of Clinorg. Undisturbed soil cores were collected in a coniferous forest soil in SE Sweden. The cores were stored in climate chambers for three months, irrigated with artificial rain, and the leachate was collected and analysed. The water balance of the lysimeters could be well described, and we found that 20-50% of the chlorine leached from the lysimeters was organically bound and that the amounts lost did not decrease with time. This strongly suggests that a substantial amount of Clorg forms in topsoil, and that subsequent leaching to deeper layers causes a considerable withdrawal of Clinorg. The concentration of both organic carbon and Clorg in the leachate was considerably higher than concentrations observed in the runoff in the actual catchment, suggesting that organic matter precipitates or is mineralized on its way through the soil. Copyright © 2005 John Wiley &amp; Sons, Ltd."
"7201706787;10241985000;7102543399;","Arctic tropospheric winds derived from TOVS satellite retrievals",2005,"10.1175/JCLI3407.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26844558932&doi=10.1175%2fJCLI3407.1&partnerID=40&md5=91d90f1631cd330e814d71caa8bf7d3f","Accurate three-dimensional wind fields are essential for diagnosing a variety of important climate processes in the Arctic, such as the advection and deposition of heat and moisture, changes in circulation features, and transport of trace constituents. In light of recent studies revealing significant biases in upper-level winds over the Arctic Ocean from reanalyses, new daily wind fields are generated from 22.5 yr of satellite-retrieved thermal-wind profiles, corrected with a recently developed mass-conservation scheme. Compared to wind measurements from rawinsondes during the Surface Heat Budget of the Arctic (SHEBA) experiment, biases in satellite-retrieved winds are near zero in the meridional direction, versus biases of over 50% for reanalyses. Errors in the zonal component are smaller than those observed in reanalysis winds in the upper troposphere, while in the lower troposphere the effects of Greenland introduce uncertainty in the mass-conservation calculation. Further reduction in error may be achieved by incorporating winds retrieved from feature-tracking techniques using satellite imagers. Overall, satellite-retrieved winds are superior to reanalysis products over the data-sparse Arctic Ocean and provide increased accuracy for analyses requiring wind information. Trends and anomalies for the 22.5-yr record are calculated for both mer idional and zonal winds at eight levels between the surface and 300 hPa. Annual mean trends are similar at varying levels, reflecting the relatively barotropic nature of the Arctic troposphere. Zonal winds are more westerly over Eurasia and the western Arctic Ocean, while westerlies have weakened over northern Canada. Combined with the corresponding pattern in meridional winds, these results suggest that the polar vortex has, on average, shifted toward northern Canada. Seasonal trends show that some changes persist throughout the year while others vary in magnitude and sign. Most striking are spring patterns, which differ markedly from the other seasons. Changes in meridional winds are consistent with observed trends in melt-onset date and sea ice concentration in the marginal seas. Anomalies in zonal wind profiles exhibit decadal-scale cyclicity in the eastern Arctic Ocean, while overall shifts in anomaly signs are evident and vary by region. The winter North Atlantic Oscillation (NAO) index correlates moderately with meridional wind anomalies in the Atlantic sector of the Arctic Ocean: positively (0.48) in the Barents Sea and negatively (-0.59) in the Lincoln Sea. These observed trends and anomalies are expected to translate to changes in advected heat and moisture into the Arctic basin, which are likely linked to trends in sea ice extent, melt onset, cloud properties, and surface temperature. © 2005 American Meteorological Society."
"6507253177;7401837691;","The impact of zonal propagation and seeding on the eddy-mean flow equilibrium of a zonally varying two-layer model",2005,"10.1175/JAS3473.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344438755&doi=10.1175%2fJAS3473.1&partnerID=40&md5=3f280d8d9046344b652350a89d399d66","This paper investigates the role of zonal propagation for the equilibration of zonally varying flow. It is hypothesized that there exist two ideal limits, for very small or very large group speed. In the first limit the eddies equilibrate locally with the forcing, while in the second limit the equilibration can only be understood in a global sense. To understand these two limits and to assess which is more relevant for the extratropical troposphere, a series of idealized experiments that involves changing the magnitude of the uniform zonal wind is performed. The results of the idealized model experiments suggest that the actual troposphere is likely to be in a transition regime between the two limits, but perhaps closer to the global than the local limit. Near the global limit, both the eddy amplitude and local baroclinicity over the baroclinic zone are strongly affected by the amount of upstream seeding. When the propagation speed is reduced relative to the control run, the zonal mean eddy activity decreases because the residence time increases more over the stable part of the channel than along the baroclinic zone. With the decrease in upstream seeding, the local supercriticality along the baroclinic zone increases, although the increase is moderate. The decrease in seeding and increase in baroclinicity partially offset the effects of each other, leading to only small changes in the maximum eddy amplitude downstream of the baroclinic zone. Changes in upstream seeding can also be achieved by enhanced damping. When the eddies are locally damped, the baroclinicity is also enhanced downstream of the damping region due to reduced eddy fluxes. For typical parameters, the recovery of the eddy amplitude occurs over very long distances. Based on these idealized results, it is argued that the coexistence of enhanced baroclinicity and weaker eddy amplitude over the Pacific storm track, as compared to the Atlantic storm track, is consistent with the effects of strong eddy damping over Asia. © 2005 American Meteorological Society."
"7005956183;57202413846;7004540083;7201821692;7601318782;7004384155;23005081100;7102953444;","Cloud effects on the radiation budget based on ISCCP data (1991 to 1995)",2005,"10.1002/joc.1157","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22144453603&doi=10.1002%2fjoc.1157&partnerID=40&md5=ce9a73a93a475c2427a0b1ca3e53c872","Consistent and validated data sets of satellite-borne radiances and of a large variety of products describing the characteristics of terrestrial cloud and radiation fields have been produced within the International Satellite Cloud Climatology Project (ISCCP) covering the years 1983 through to 2003. A subset (annual and seasonal averages of the 5 year period 1991 to 1995) is used in this paper to discuss in greater detail the effect of clouds on the radiation fields at the upper and lower boundary of the atmosphere and in particular on the loss and gain (vertical divergence) of radiant energy by the atmosphere itself. Although this subset covers the effects of the Pinatubo eruption (June 1991) and of the strong El Niño event in 1992-93, which indeed caused 'anomalies in the average aerosol and cloud fields in the tropics and subtropics'. However, our regional averages of the radiation budget at the top of the atmosphere and at ground over a period of 5 years should be within 2-5 W m-2 of longer term averages. We find very interesting spatial patterns in the global distributions of all quantities, which can be explained in part by various cloud field characteristics and by the continental surface characteristics. Most are known from similar studies with radiation budget measurements. Possibly for the first time, we show global fields of the vertical flux divergence of solar and terrestrial radiation within the atmosphere and of the effects of clouds. Both polar regions, various portions of China and the areas of persistent subtropical maritime stratocumulus fields over the Pacific and Atlantic Oceans and of cloud fields associated with the intertropical convergence zone (ITCZ) offer specific features for further analyses. This ISCCP data set seems to underestimate the absorption of solar radiation in the tropical and subtropical atmosphere by about 10 to 20 W m-2. There is a disagreement of about 30 W m-2 in global averages of the gain and loss of solar and terrestrial radiation in the atmosphere between this and two other independent data sets, which needs thorough investigation, since such data are required to validate the radiation budgets within circulation and climate models and for other climate studies. Such an assessment of radiation budget data is now under way within the auspices of the World Climate Research Programme. Copyright © 2005 Royal Meteorological Society."
"55420553800;8620111700;","The generation of monthly gridded datasets for a range of climatic variables over the UK",2005,"10.1002/joc.1161","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22144476240&doi=10.1002%2fjoc.1161&partnerID=40&md5=f1fdc4999db09dc65895043b0d823a88","Monthly or annual 5 km × 5 km gridded datasets covering the UK are generated for the 1961-2000 period, for 36 climatic parameters. As well as the usual elements of temperature, rainfall, sunshine, cloud, wind speed, and pressure, derived temperature variables (such as growing-season length, heating degree days, and heat and cold wave durations) and further precipitation variables (such as rainfall intensity, maximum consecutive dry days, and days of snow, hail and thunder) are analysed. The analysis process uses geographical information system capabilities to combine multiple regression with inverse-distance-weighted interpolation. Geographic and topographic factors, such as easting and northing, terrain height and shape, and urban and coastal effects, are incorporated either through normalization with regard to the 1961-90 average climate, or as independent variables in the regression. Local variations are then incorporated through the spatial interpolation of regression residuals. For each of the climatic parameters, the choice of model is based on verification statistics produced by excluding a random set of stations from the analysis for a selection of months, and comparing the observed values with the estimated values at each point. This gives some insight into the significance, direction, and seasonality of factors affecting different climate elements. It also gives a measure of the accuracy of the method at predicting values between station locations. The datasets are being used for the verification of climate modelling scenarios and are available via the Internet. © Crown Copyright 2005. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd."
"7404587604;7102948268;","Analysis of trends in maximum and minimum temperature, diurnal temperature range, and cloud cover over India",2005,"10.1029/2004GL022201","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844460488&doi=10.1029%2f2004GL022201&partnerID=40&md5=2c99b945c33e59af607e8d646aef8e9b","We assembled data at a 1° latitude by 1° longitude resolution for 285 cells across India and analyzed the seasonal trends in the maximum and minimum temperature, diurnal temperature range (DTR), and cloud cover for the time period 1931-2002. Significant increases in maximum and minimum temperature have occurred over the Deccan plateau, but in general, trends in DTR were not significant except for a decrease in northwest Kashmir in summer. The effect of cloud cover on the DTR was expectedly negative for most of the country for winter and summer seasons with significant increase in summer cloud cover in Kashmir. Copyright 2005 by the American Geophysical Union."
"57185381300;6602003804;6701785367;","Atmospheric controls of the heat balance of Zongo Glacier (16°S, Bolivia)",2005,"10.1029/2004JD005732","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23244458458&doi=10.1029%2f2004JD005732&partnerID=40&md5=e121e3269e8cd2b22568b287f73ccde4","Tropical glaciology includes investigation of climate variability in poorly documented regions of large surface-atmosphere energy exchanges. This study examines the surface energy fluxes of the Bolivian Zongo Glacier (16°S, 68°W, 6000-4900 m asl) in order to identify the atmospheric variables that control melting. Measurements from 1998 to 2000 taken from two meteorological stations in the ablation area are analyzed. During the progressive development of the wet season from September to January, melting energy was high: Solar irradiance was close to its summer solstice peak, clouds were sporadic, and albedo was low. During the core of the wet season from January to April the magnitudes of the net short-wave (+) and net long-wave (-) radiation fluxes were reduced by frequent clouds and snowfalls so that melting energy was moderate. In the dry season from May to August, melting energy was small because of the energy losses essentially in long-wave radiation but also in sublimation. The turbulent sensible heat flux to the ice (+) generally offsets the energy loss in latent heat (-), except in the dry season, when sublimation prevailed because of strong wind and dry air. Solar radiation was the main source of energy, but the seasonal changes of the melting energy were driven by long-wave radiation. In particular, clouds sharply increased the emittance of the thin high-altitude atmosphere. Closely linked to clouds and humidity, the main seasonal variables of low-latitude climates, long-wave radiation is a key variable in the energy balance of tropical glaciers. Copyright 2005 by the American Geophysical Union."
"8953038700;7005973015;","Spatial and spectral variability of the outgoing thermal IR spectra from AIRS: A case study of July 2003",2005,"10.1029/2004JD005530","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23244445182&doi=10.1029%2f2004JD005530&partnerID=40&md5=7a545abdc5f46c8f862f318c9ec8ae8c","Here we present a survey of the spatial variability in different climate zones seen from AIRS data, using the spectral EOF analysis. Over the tropical and subtropical oceans, the first principal component (PC1) is mostly due to the thermal contrast between surface and thick cold cloud tops. The second principal component (PC2) is mainly due to the spatial variation of the lower tropospheric humidity (LTH) and the low clouds. The signature of dust aerosol over the Arabian Sea and the Atlantic off the coast of North Africa in the summertime can be clearly seen in the PC2. Both the PC1 and the PC2 capture the upper tropospheric water vapor variability due to the forced orthogonality of EOFs, The third principal component (PC3) is mainly due to the spatial variation of the lower stratospheric temperature. Over the midlatitude oceans, the PC1 is still due to the thermal contrast of emission temperature. During wintertime, the PC2 is mainly due to stratospheric temperature variations. In the summer, the PC2 over the southern hemisphere is still due to stratospheric temperature variations, but in the northern hemisphere it is mainly due to the variations of the LTH and the low clouds. An exploratory study using synthetic spectra based on a NCAR CAM2 simulation shows that the model could account for the essential features in the data as well as provide an explanation of the three leading PCs. Major disagreements exist in the location of the ITCZ, the dust aerosol, and the lower stratospheric temperature. Copyright 2005 by the American Geophysical Union."
"17433905200;6701378450;","Continued development of a cloud droplet formation parameterization for global climate models",2005,"10.1029/2004JD005591","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24644475770&doi=10.1029%2f2004JD005591&partnerID=40&md5=d109d4e13bb01ff6ad88de80709a064d","This study presents continued development of the Nenes and Seinfeld (2003) cloud droplet activation parameterization. First, we expanded the formulation to (1) allow for a lognormal representation of aerosol size distribution, and (2) include a size-dependant mass transfer coefficient for the growth of water droplets to accommodate the effect of size (and potentially organic films) on the droplet growth rate. The performance of the new scheme is evaluated by comparing the parameterized cloud droplet number concentration with that of a detailed numerical activation cloud parcel model. The resulting modified parameterization robustly and closely tracks the parcel model simulations, even for low values of the accommodation coefficient (average error 4.1 ± 1.3%). The modifications to include the effect of accommodation coefficient do not increase the computational cost but substantially improve the parameterization performance. This work offers a robust, computationally efficient and first-principles approach for directly linking complex chemical effects (e.g., surface tension depression, changes in water vapor accommodation, solute contribution from partial solubility) on aerosol activation within a global climate modeling framework. Copyright 2005 by the American Geophysical Union."
"7401829771;7409189983;55728684000;6603166240;7005035462;","Impacts of in situ and additional satellite data on the accuracy of a sea-surface temperature analysis for climate",2005,"10.1002/joc.1168","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21344437254&doi=10.1002%2fjoc.1168&partnerID=40&md5=24f71abd9fe7f35f03bd49fbf6a6a670","Additional in situ and satellite data improve the accuracy of a blended (in situ and satellite) sea-surface temperature (SST) analysis using optimum interpolation (OI). Two studies were conducted to evaluate the impacts of in situ and additional satellite data. One study evaluated the adequacy of the recent in situ network. Because of the high coverage of satellite data, in situ data used in the analysis tends to be overwhelmed by satellite data. Thus, the most important role of the in situ data in the analysis is to correct large-scale satellite biases. Simulations with different buoy densities showed the need for at least two buoys on a 10° spatial grid. This will ensure that satellite biases do not exceed 0.5°C. Using this criterion, regions were identified where additional buoys are needed. A second study evaluated the impact of satellite SST retrievals from the tropical rainfall measuring mission microwave imager (TMI) on the OI analysis. The present version only uses infrared satellite data from the advanced very high resolution radiometer (AVHRR) instrument. The results of the intercomparisons showed that both AVHRR and TMI data have biases that must be corrected for climate studies. The addition of TMI data clearly improved the OI analysis accuracy without bias correction, but was less significant when bias correction was used. However, there are areas of the ocean with limited in situ data and restricted AVHRR coverage due to cloud cover, and the use of both TMI and AVHRR should improve the accuracy of the analysis in those areas. Copyright © 2005 Royal Meteorological Society."
"8507223000;6602736207;36640176800;57207433434;","Objective analyses of sea-surface temperature and marine meteorological variables for the 20th century using ICOADS and the Kobe Collection",2005,"10.1002/joc.1169","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21344436150&doi=10.1002%2fjoc.1169&partnerID=40&md5=0c88db574e061d9fd7995c1bb23e8299","Data for the 20th century from the International Comprehensive Ocean and Atmosphere Data Set and the Kobe Collection have been used as input data for global objective analyses of sea-surface temperatures (SSTs) and other marine meteorological variables. This study seeks a better understanding of the historical marine meteorological data and an evaluation of the quality of the data in the Kobe Collection. Objective analyses yield gridded data that are less noisy than observed data, which facilitates handling of historical data. The observed data determine the quality of the objective analyses, and quality control specified for historical data is incorporated into the objective analysis to reduce artificial errors. The objective analyses are based on optimum interpolation and reconstruction with empirical orthogonal functions. The final database produced in this study not only contains analysed values, but also analysis errors and data distributions at each time step of the objective analyses. The analysis database contains amp le information on historical observations, as well as signals of marine climate variations during the century. Time series of global mean marine temperatures and cloud cover include trends linked to global warming, and local peaks appear commonly in all the time series around the 1940s. Sea-level pressure and sea-surface wind fields show significant linear trends at high latitudes and over the North Pacific Ocean respectively. These trends seem to be artificial. An SST analysis used widely in climatological studies was verified against HadISST from the Hadley Centre and an SST analysis derived from satellite and in situ observations. El Niño and southern oscillation indices for the century are successfully reproduced, even though observations in the tropics are much rarer before 1950 than after 1950. Copyright © 2005 Royal Meteorological Society."
"55859338300;7402727711;57217720842;8523618200;55624487293;","Numerical analysis of effects of atmospheric ice nuclei concentrations on radiant properties of cold clouds",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-19044376502&partnerID=40&md5=77d398dcaa03d359b2004d1b09b948c1","Numerical simulations of 18 precipitation days from June to September in 1996 with the 3D convective cloud model of CAMS (Chinese Academy of Meteorological Sciences, Version 2000) were conducted. In these simulations, the concentration of IN (ice nuclei) was assumed to increase by 5 times. The results show that when IN concentrations increase, the amounts of precipitation decrease, cloud tops heighten and the areas of cloud tops increase in 80 percent simulated clouds. Moreover, in 95 percent simulated clouds, the sizes of ice crystals in clouds decrease and quantities increase. These results mean that the physical properties of clouds will change when IN concentration increases. The radiant properties of clouds and climate may also change directly and indirectly."
"7103158465;7202162685;7003663305;7005035762;","A new double-moment microphysics parameterization for application in cloud and climate models. Part II: Single-column modeling of arctic clouds",2005,"10.1175/JAS3447.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13244276117&doi=10.1175%2fJAS3447.1&partnerID=40&md5=bb133b7dd08a2af035e57e90bb851efc","The new double-moment microphysics scheme described in Part I of this paper is implemented into a single-column model to simulate clouds and radiation observed during the period 1 April-15 May 1998 of the Surface Heat Budget of the Arctic (SHEBA) and First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment-Arctic Clouds Experiment (FIRE-ACE) field projects. Mean predicted cloud boundaries and total cloud fraction compare reasonably well with observations. Cloud phase partitioning, which is crucial in determining the surface radiative fluxes, is fairly similar to ground-based retrievals. However, the fraction of time that liquid is present in the column is somewhat underpredicted, leading to small biases in the downwelling shortwave and longwave radiative fluxes at the surface. Results using the new scheme are compared to parallel simulations using other microphysics parameterizations of varying complexity. The predicted liquid water path and cloud phase is significantly improved using the new scheme relative to a single-moment parameterization predicting only the mixing ratio of the water species. Results indicate that a realistic treatment of cloud ice number concentration (prognosing rather than diagnosing) is needed to simulate arctic clouds. Sensitivity tests are also performed by varying the aerosol size, solubility, and number concentration to explore potential cloud-aerosol-radiation interactions in arctic stratus. © 2005 American Meteorological Society."
"6507215173;7004125528;7006577245;7102128820;6701754792;23017945100;6506416572;","The retrieval of ice-cloud properties from cloud radar and lidar synergy",2005,"10.1175/JAM2229.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16244413304&doi=10.1175%2fJAM2229.1&partnerID=40&md5=bc2982a12f48cfd4093ba6f807f8e94d","Clouds are an important component of the earth's climate system. A better description of their microphysical properties is needed to improve radiative transfer calculations. In the framework of the Earth, Clouds, Aerosols, and Radiation Explorer (EarthCARE) mission preparation, the radar-lidar (RALI) airborne system, developed at L'Institut Pierre Simon Laplace (France), can be used as an airborne demonstrator. This paper presents an original method that combines cloud radar (94-95 GHz) and lidar data to derive the radiative and microphysical properties of clouds. It combines the apparent backscatter reflectivity from the radar and the apparent backscatter coefficient from the lidar. The principle of this algorithm relies on the use of a relationship between the extinction coefficient and the radar specific attenuation, derived from airborne microphysical data and Mie scattering calculations. To solve radar and lidar equations in the cloud region where signals can be obtained from both instruments, the extinction coefficients at some reference range z0 must be known. Because the algorithms are stable for inversion performed from range z0 toward the emitter, z0 is chosen at the farther cloud boundary as observed by the lidar. Then, making an assumption of a relationship between extinction coefficient and backscattering coefficient, the whole extinction coefficient, the apparent reflectivity, cloud physical parameters, the effective radius, and ice water content profiles are derived. This algorithm is applied to a blind test for downward-looking instruments where the original profiles are derived from in situ measurements. It is also applied to real lidar and radar data, obtained during the 1998 Cloud Lidar and Radar Experiment (CLARE'98) field project when a prototype airborne RALI system was flown pointing at nadir. The results from the synergetic algorithm agree reasonably well with the in situ measurements. © 2005 American Meteorological Society."
"7103158465;7202162685;6701324864;","A new double-moment microphysics parameterization for application in cloud and climate models. Part I: Description",2005,"10.1175/JAS3446.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14744300799&doi=10.1175%2fJAS3446.1&partnerID=40&md5=3459942d755612dda75a95ce09d38316","A new double-moment bulk microphysics scheme predicting the number concentrations and mixing ratios of four hydrometeor species (droplets, cloud ice, rain, snow) is described. New physically based parameterizations are developed for simulating homogeneous and heterogeneous ice nucleation, droplet activation, and the spectral index (width) of the droplet size spectra. Two versions of the scheme are described: one for application in high-resolution cloud models and the other for simulating grid-scale cloudiness in larger-scale models. The versions differ in their treatment of the supersaturation field and droplet nucleation. For the high-resolution approach, droplet nucleation is calculated from Kohler theory applied to a distribution of aerosol that activates at a given supersaturation. The resolved supersaturation field and condensation/deposition rates are predicted using a semianalytic approximation to the three-phase (vapor, ice, liquid) supersaturation equation. For the large-scale version of the scheme, it is assumed that the supersaturation field is not resolved and thus droplet activation is parameterized as a function of the vertical velocity and diabatic cooling rate. The vertical velocity includes a subgrid component that is parameterized in terms of the eddy diffusivity and mixing length. Droplet condensation is calculated using a quasi-steady, saturation adjustment approach. Evaporation/deposition onto the other water species is given by nonsteady vapor diffusion allowing excess vapor density relative to ice saturation. © 2005 American Meteorological Society."
"26643363200;7102643810;7102965584;7005793610;","Dissecting the anomaly: A closer look at the documented urban enhancement in summer season ground flash densities in and around the Houston area",2005,"10.1029/2005GL022725","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22444442862&doi=10.1029%2f2005GL022725&partnerID=40&md5=2ff4a6950d19e5d3cc479bea0abcd28f","The Houston ""lightning anomaly"" was examined using nine years of cloud-to-ground (CG) lightning data (1995-2003). We find that the local Houston CG lightning anomaly, is a persistent feature, but statistically non-unique along the Gulf Coast. The results also suggest that although the Houston area sees an increased frequency of lightning producing storms, storms occurring further inland appear to produce more lightning on an event basis. Although hypotheses invoking anthropogenic influences have been offered to explain the Houston flash density anomaly, it seems equally plausible that mesoscale influences along the coastline may also be important. Copyright 2005 by the American Geophysical Union."
"23017945100;6701754792;7004125528;6506416572;7005729142;6506385754;55454856700;7102425008;","Statistical properties of the normalized ice particle size distribution",2005,"10.1029/2004JD005405","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21444436370&doi=10.1029%2f2004JD005405&partnerID=40&md5=94cebde1860f79fa0cb6e3014e452607","Testud et al. (2001) have recently developed a formalism, known as the ""normalized particle size distribution (PSD)"", which consists in scaling the diameter and concentration axes in such a way that the normalized PSDs are independent of water content and mean volume-weighted diameter. In this paper we investigate the statistical properties of the normalized PSD for the particular case of ice clouds, which are known to play a crucial role in the Earth's radiation balance. To do so, an extensive database of airborne in situ microphysical measurements has been constructed. A remarkable stability in shape of the normalized PSD is obtained. The impact of using a single analytical shape to represent all PSDs in the database is estimated through an error analysis on the instrumental (radar reflectivity and attenuation) and cloud (ice water content, effective radius, terminal fall velocity of ice crystals, visible extinction) properties. This resulted in a roughly unbiased estimate of the instrumental and cloud parameters, with small standard deviations ranging from 5 to 12%. This error is found to be roughly independent of the temperature range. This stability in shape and its single analytical approximation implies that two parameters are now sufficient to describe any normalized PSD in ice clouds: the intercept parameter N*0 and the mean volume-weighted diameter Dm. Statistical relationships (parameterizations) between N*0 and Dm have then been evaluated in order to reduce again the number of unknowns. It has been shown that a parameterization of N*0 and Dm by temperature could not be envisaged to retrieve the cloud parameters. Nevertheless, Dm-T and mean maximum dimension diameter-T parameterizations have been derived and compared to the parameterization of Kristjánsson et al. (2000) currently used to characterize particle size in climate models. The new parameterization generally produces larger particle sizes at any temperature than the Kristjánsson et al. (2000) parameterization. These new parameterizations are believed to better represent particle size at global scale, owing to a better representativity of the in situ microphysical database used to derive it. We then evaluated the potential of a direct N*0-Dm relationship. While the model parameterized by temperature produces strong errors on the cloud parameters, the N*0-Dm model parameterized by radar reflectivity produces accurate cloud parameters (less than 3% bias and 16% standard deviation). This result implies that the cloud parameters can be estimated from the estimate of only one parameter of the normalized PSD (N*0 or Dm) and a radar reflectivity measurement. Copyright 2005 by the American Geophysical Union."
"7404942217;51864222300;57219233745;7102237529;35779630500;","Seasonal variation in the regional structure of warming across China in the past half century",2005,"10.3354/cr028213","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20844453768&doi=10.3354%2fcr028213&partnerID=40&md5=9f57c07ffe0fb01e5223f77e6a2d0912","A dataset of 160 National Meteorological Observatory stations with long-term monthly temperature data for China was analyzed to assess the seasonal variation of the spatial temperature structure across China in the past half century. Different warming trends were found for the different seasons: the extent of warming is stronger and more widespread in winter than in summer. Warming is more pronounced at higher latitude, particularly in winter. The possible mechanisms of seasonal variation in climate warming include effects of greenhouse gases, increased cloud cover due to increases in sulfate aerosols, and local processes such as changes in land use and urban heat island effects. © Inter-Research 2005."
"6602178158;8670472000;","Modeled and observed clouds during Surface Heat Budget of the Arctic Ocean (SHEBA)",2005,"10.1029/2004JD004751","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21544432969&doi=10.1029%2f2004JD004751&partnerID=40&md5=28a1d34ec489cdba3e70dd13b1996f3a","Observed monthly mean cloud cover from the SHEBA site is found to differ by a substantial amount during winter depending on cloud observing instrument. This makes it difficult for climate modelers to evaluate modeled clouds and improve parameterizations. Many instruments and human observers cannot properly detect the thinnest clouds and count them as clear sky instead, resulting in too low cloud cover. To study the impact from the difficulties in the detection of thin clouds, we compute cloud cover in our model with a filter that removes the thinnest clouds. Optical thickness is used as a proxy to identify thin clouds as we are mainly interested in the impact of clouds on radiation. With the results from a regional climate model simulation of the Arctic, we can reproduce the large variability in wintertime cloud cover between instruments when assuming different cloud detection thresholds. During winter a large fraction of all clouds are optically thin, which causes the large sensitivity to filtering by optical thickness. During summer, most clouds are far above the optical thickness threshold and filtering has no effect. A fair comparison between observed and modeled cloud cover should account for thin clouds that may be present in models but absent in the observational data set. Difficulties with the proper identification of clouds and clear sky also has an effect on cloud radiative forcing. The derived clear-sky longwave flux at the surface can vary by some W m-2 depending on the lower limit for the optical thickness of clouds. This impacts on the ""observed"" LW cloud radiative forcing and suggests great care is needed in using satellite-derived cloud radiative forcing for model development. Copyright 2005 by the American Geophysical Union."
"8528590100;7005793610;","High percentage of positive lightning along the USA west coast",2005,"10.1029/2005GL022782","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21044448667&doi=10.1029%2f2005GL022782&partnerID=40&md5=cdff244fe38926c6085b9d195baea4c6","Analyses of the cloud-to-ground (CG) lightning characteristics recorded by the US National Lightning Detection Network (NLDN) along the west coast reveal an average annual percentage of positive CG flashes around 40%, while the average value for the USA is approximately 10%. The primary goal of the study was to document and suggest reasons for this positive CG anomaly. Through seasonal and monthly storm analysis, it was determined that the high annual percent positive along the coast is the result of the low variability in total CG flashes throughout the year coupled with a high number of positive CG flashes during the winter season which can be directly attributed to the climate of the Pacific Coast. The topography of the region was determined to affect the areal distribution of the percent positive anomaly by restricting the inward extent of the coastal climate. The secondary goal of the study was to determine whether the following meteorological variables were related to the dominant CG polarity in a storm: 1) the variation of charge region heights using the -10°C level as a proxy and 2) the tilting of the charge regions by strong windshear. Statistical analysis showed that the height of the -10°C temperature level is related to the dominant CG polarity in a storm, while the windshear did not show a significant relationship. In addition, analyses showed that the thunderstorms that produced few CG flashes (< 6 flashes) contributed most to the total number of positive CG flashes. Copyright 2005 by the American Geophysical Union."
"6602418877;57193882808;7006095466;","Explicit convection over the Western Pacific warm pool in the community atmospheric model",2005,"10.1175/JCLI3345.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20544469956&doi=10.1175%2fJCLI3345.1&partnerID=40&md5=0439b0acfd8d0b702b85071fa789a7d8","This paper reports on the application of the cloud-resolving convection parameterization (CRCP) to the Community Atmospheric Model (CAM), the atmospheric component of the Community Climate System Model (CCSM). The cornerstone of CRCP is the use of a two-dimensional zonally oriented cloud-system resolving model to represent processes on mesoscales at the subgrid scale of a climate model. Herein, CRCP is applied at each climate model column over the tropical western Pacific warm pool, in a domain spanning 10°S-10°N, 150°-170°E. Results from the CRCP simulation are compared with CAM in its standard configuration. The CRCP simulation shows significant improvements of the warm pool climate. The cloud condensate distribution is much improved as well as the bias of the tropopause height. More realistic structure of the intertropical convergence zone (ITCZ) during the boreal winter and better representation of the variability of convection are evident. In particular, the diurnal cycle of precipitation has phase and amplitude in good agreement with observations. Also improved is the large-scale organization of the tropical convection, especially superclusters associated with Madden-Julian oscillation (MJO)-like systems. Location and propagation characteristics, as well as lower-tropospheric cyclonic and upper-tropospheric anticyclonic gyres, are more realistic than in the standard CAM. Finally, the simulations support an analytic theory of dynamical coupling between organized convection and equatorial beta-plane vorticity dynamics associated with MJO-like systems. © 2005 American Meteorological Society."
"7402174994;55768583400;","An improved method of constructing a database of monthly climate observations and associated high-resolution grids",2005,"10.1002/joc.1181","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20444471429&doi=10.1002%2fjoc.1181&partnerID=40&md5=a04902b6c303e22b10ab667556b3a983","A database of monthly climate observations from meteorological stations is constructed. The database includes six climate elements and extends over the global land surface. The database is checked for inhomogeneities in the station records using an automated method that refines previous methods by using incomplete and partially overlapping records and by detecting inhomogeneities with opposite signs in different seasons. The method includes the development of reference series using neighbouring stations. Information from different sources about a single station may be combined, even without an overlapping period, using a reference series. Thus, a longer station record may be obtained and fragmentation of records reduced. The reference series also enables 1961-90 normals to be calculated for a larger proportion of stations. The station anomalies are interpolated onto a 0.5° grid cove ring the global land surface (excluding Antarctica) and combined with a published normal from 1961-90. Thus, climate grids are constructed for nine climate variables (temperature, diurnal temperature range, daily minimum and maximum temperatures, precipitation, wet-day frequency, frost-day frequency, vapour pressure, and cloud cover) for the period 1901-2002. This dataset is known as CRU TS 2.1 and is publicly available (http:// www.cru.uea.ac uk/). Copyright © 2005 Royal Meteorological Society."
"6603341831;6603868770;6507128092;6506306467;","Assessing model predicted vertical cloud structure and cloud overlap with radar and lidar ceilometer observations for the Baltex Bridge Campaign of CLIWA-NET",2005,"10.1016/j.atmosres.2004.12.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-19144365715&doi=10.1016%2fj.atmosres.2004.12.008&partnerID=40&md5=6c013ce7bf9f07f4c766f3a034fa4bd7","The cloud vertical distribution and overlap of four large-scale models operating at different horizontal and vertical resolutions have been assessed using radar and lidar observations from the Baltex Bridge Campaign of CLIWA-NET. The models range from the global European Centre for Medium range Weather Forecast (ECMWF) model, to the Regional Atmospheric Climate Model (RACMO) and the Rossby Centre Atmospheric (RCA) regional climate model, to the non-hydrostatic meso-scale Lokal Model (LM). Different time averaging periods for the radar data were used to estimate the uncertainty of the point-to-space transformations of the observations. Relative to the observations, all models underestimated the height of the lowest cloud base. Clouds occurred more frequently in the models but with smaller cloud fractions below 7 km. The findings confirm previous cloud radar studies which found that models overestimate cloud fractions above 7 km. Radar-observed clouds were often thinner than the model vertical resolutions, which can have serious implications on model cloud overlap and radiation fluxes. The radar-derived cloud overlap matrix, which takes into account the overlap of all vertical layers, was found to be close to maximum-random overlap. Using random overlap for vertically continuous clouds with vertical gradients in cloud fraction larger than 40-50% per kilometre gave the best fit to the data. The gradient approach could be improved by making it resolution- and cloud system-dependent. Previous cloud radar overlap studies have considered the overlap of two cloud layers as a function of maximum and random overlap. Here, it was found that the two-layer overlap could be modelled by a mixture of maximum and minimum overlap. © 2005 Elsevier B.V. All rights reserved."
"7202559581;7401742385;","Inclusion of urban landscape in a climate model",2005,"10.1175/BAMS-86-5-681","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20544464930&doi=10.1175%2fBAMS-86-5-681&partnerID=40&md5=40b19d4ab9143decd51f24f2c232843d","Urban schemes are currently being developed for land surface models. The urban schemes need to include potential feedbacks to the atmosphere and hydrological cycles. Three specific emphases that need to be considered are the large fraction of impervious surfaces that impact surface temperatures and hydrology, that urban plants may be irrigated, and the urban transports that are generated by buildings and vegetation at multiple heights."
"7007021059;6603196127;7102875645;","Radiative damping of annual variation in global mean surface temperature: Comparison between observed and simulated feedback",2005,"10.1007/s00382-005-0002-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23844490151&doi=10.1007%2fs00382-005-0002-y&partnerID=40&md5=d7423dc65fc81ed5af22d46a26c18e2c","The sensitivity of the global climate is essentially determined by the radiative damping of the global mean surface temperature anomaly through the outgoing radiation from the top of the atmosphere (TOA). Using the TOA fluxes of terrestrial and reflected solar radiation obtained from the Earth radiation budget experiment (ERBE), this study estimates the magnitude of the overall feedback, which modifies the radiative damping of the annual variation of the global mean surface temperature, and compare it with model simulations. Although the pattern of the annually varying anomaly is quite different from that of the global warming, the analysis conducted here may be used for assessing the systematic bias of the feedback that operates on the CO2-induced warming of the surface temperature. In the absence of feedback effect, the outgoing terrestrial radiation at the TOA is approximately follows the Stefan-Boltzmann's fourth power of the planetary emission temperature. However, it deviates significantly from the blackbody radiation due to various feedbacks involving water vapor and cloud cover. In addition, the reflected solar radiation is altered by the feedbacks involving sea ice, snow and cloud, thereby affecting the radiative damping of surface temperature. The analysis of ERBE reveals that the radiative damping is weakened by as much as 70% due to the overall effect of feedbacks, and is only 30% of what is expected for the blackbody with the planetary emission temperature. Similar feedback analysis is conducted for three general circulation models of the atmosphere, which was used for the study of cloud feedback in the preceding study. The sign and magnitude of the overall feedback in the three models are similar to those of the observed. However, when it is subdivided into solar and terrestrial components, they are quite different from the observation mainly due to the failure of the models to simulate individually the solar and terrestrial components of the cloud feedback. It is therefore desirable to make the similar comparison not only for the overall feedback but also for its individual components such as albedo- and cloud-feedbacks. Although the pattern of the annually-varying anomaly is quite different from that of global warming, the methodology of the comparative analysis presented here may be used for the identification of the systematic bias of the overall feedback in a model. A proposal is made for the estimation of the best guess value of climate sensitivity using the outputs from many climate models submitted to the Intergovernmental panel on Climate Change. © Springer-Verlag 2005."
"6603873829;6603868770;","Comparison of model predicted liquid water path with ground-based measurements during CLIWA-NET",2005,"10.1016/j.atmosres.2004.12.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-19144365993&doi=10.1016%2fj.atmosres.2004.12.006&partnerID=40&md5=5f43b9d3070a3901a52e90bc8789e6ea","Continuous cloud remote sensing measurements with microwave radiometers and various other instruments were conducted in a ground-based network as part of the EU-project CLIWA-NET with the focus on liquid water path (LWP). The observations, taken from a network of ground-based stations within the BALTEX modeling area, cover in total 6 months and were compared with short-term predictions from atmospheric models. Two models for numerical weather forecasting: the ECMWF model and the meso-scale Lokal-Modell operated by the German Weather Service, and two models for regional climate prediction: the Rossby Centre Atmospheric model and KNMI model RACMO, participated in the model evaluation. In view of the restriction that microwave radiometer measurements are unreliable when the instrument becomes wet, it is essential that events of precipitation be accurately identified in the observations and model values are effectively filtered out. Non-zero or even negative values of observed LWP in cloud free situations are effectively dealt with by a time-dependent correction based on information of supporting instruments for cloud detection. Temporal aggregation or, equivalently, conditional averaging in time, was used to bring the observations to scales matching the grid-box mean model predicted values. Mean observed LWP averaged over the scenes with water clouds present reduces from about 90 g/m2 for temporal scales of 5 min to about 40 g/m2 at scales of 1 h. All models, but in particular the RCA-model, tend to overpredict frequency and duration of precipitation. Different models differ most in their predictions of LWP illustrating the scarcity of LWP observations so far. The ECMWF model and, to a lesser extent, RACMO are found to overestimate mean LWP, while the RCA-model predicts values close to what has been observed. The LM-model tends to greatly underestimate the observed values. © 2005 Elsevier B.V. All rights reserved."
"56370652400;55545335600;8915690000;7404101096;","Chemical characterization of water-soluble organic acids in PM 2.5 in Beijing, China",2005,"10.1016/j.atmosenv.2004.08.038","https://www.scopus.com/inward/record.uri?eid=2-s2.0-19444386090&doi=10.1016%2fj.atmosenv.2004.08.038&partnerID=40&md5=07a131e3a77e9e41db28202f8cc77723","Water-soluble organic acids are important components in atmospheric aerosols and can act as cloud condensation nuclei to potentially affect the climate. In this study, a total of 25 PM 2.5 samples were collected from summer to winter in 2002-2003 at an urban area in Beijing. C 2-C 5 dicarboxylic acids and malic, glyoxylic and pyruvic acids were determined using a capillary electrophoresis. Oxalic acid dominated in these acids with seasonal average concentrations of 107-412 ng m -3. Malonic and succinic acids were comparable in different seasons, with seasonal average concentrations ranging from 20 to 60 ng m -3. Glutaric acid was much less abundant with an average of 10 ng m -3. The sum of these seven detected acids accounted for 3-15% of organic carbon content in PM 2.5. Seasonal differences of these acids were discussed in terms of their corresponding sources. Correlations of these acids with sulfate and MSA were also investigated to interpret their possible secondary formation pathways. © 2005 Elsevier Ltd. All rights reserved."
"6701821355;7006506461;6602548091;7003628742;","Comparison between winter and summer sky-luminance distribution in Central Europe and in the Eastern Mediterranean",2005,"10.1016/j.jastp.2004.12.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17444423626&doi=10.1016%2fj.jastp.2004.12.008&partnerID=40&md5=98897447829583219b3a134e3e76ca7e","This work studies the illuminance levels at a city in Central Europe (Bratislava) and another in the Eastern Mediterranean (Athens) and defines the prevailing sky-luminance distributions for winter and summer. The data used are 5-min values of global and diffuse horizontal irradiance and illuminance along with zenith luminance from the IDMP stations at the two cities for a period of 5 years. The study is based on the new set of the sky types recently adopted by CIE. These sky standards correspond to 15 theoretical diagrams of the ratio of zenith luminance to diffuse horizontal illuminance against solar altitude. The theoretical curves converge above 35° of solar elevation and in many cases they intersect each other. For this reason, each observation is classified into one of the 15 sky standards, only when the value of the ratio of zenith luminance to diffuse horizontal illuminance lies in a zone of ± 2.5 % around the theoretical curve describing the specific category. If any observation is classified into more than one sky standards, the corresponding ratio of global horizontal illuminance to extraterrestrial horizontal illuminance is compared to the average ratio of the sky types implicated, for the same solar altitude, and the observation is classified in the sky type with the nearest value. It is found that the most frequent sky types for Bratislava are the overcast sky with steep luminance gradation and slight brightening towards the sun (winter) and the white-blue sky with a distinct solar corona (summer), while for Athens the cloudless polluted sky prevails in both seasons. It is also found that during a summer day, a noticeable shift appears in the sky-luminance distribution at both sites. © 2005 Published by Elsevier Ltd."
"8262131200;7102701564;55738125200;7004759191;7004702869;","Evaluation of spring snow covered area depletion in the Canadian Arctic from NOAA snow charts",2005,"10.1016/j.rse.2005.01.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16344375124&doi=10.1016%2fj.rse.2005.01.006&partnerID=40&md5=1389334aa4732f2426bfd17a42075cbe","The National Oceanic and Atmospheric Administration (NOAA) weekly snow cover dataset (1966-) is the longest available record of snow cover extent (SCE) over the Northern Hemisphere (NH). This dataset has been used extensively to derive trends in continental SCE and in climate-related studies, but it has received only limited validation, particularly in high latitude areas of the NH. This study evaluated spring snow cover depletion in the NOAA dataset over a study area in the Canadian Arctic mainland north of the tree line. The evaluation used four sources of information: (1) surface snow depth and snow survey observations, (2) snow cover extent produced from the Advanced Very High Resolution Radiometer (AVHRR), (3) snow cover extent derived from Special Sensor Microwave/Imager (SSM/I), and (4) Landsat 5 TM browse images. Six spring seasons from the period 1981-2000 with low (1984, 1988, and 1998) and high (1985, 1995, and 1997) spring snow cover extent were evaluated. The evaluation revealed that the NOAA weekly dataset consistently overestimated snow cover extent during the spring melt period, with delays of up to 4 weeks in melt onset. A number of possible reasons for this delay were investigated. The most likely causes for the delayed melt onset were frequent cloud cover in the spring melt period, and the low frequency of data coverage over higher latitudes. The results suggest that caution should be exercised when using this dataset in any studies related to the timing of snowmelt in the high latitudes of the Northern Hemisphere. © 2005 Elsevier Inc. All rights reserved."
"7202954964;25647939800;8962699100;9535769800;7401945370;","A global cloud-resolving simulation: Preliminary results from an aqua planet experiment",2005,"10.1029/2005GL022459","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22944464732&doi=10.1029%2f2005GL022459&partnerID=40&md5=00e10660fe081c6f611db2a7a676a7ec","Results from global simulations using a nonhydrostatic icosahedral-grid AGCM with cloud-resolving resolutions on an aqua planet are discussed. Results depend on the resolution. Simulations with grid intervals of 7 km and 3.5 km include many realistic features in the tropics: hierarchical cloud structures, a Madden-Julian Oscillation (MJO)-like intraseasonal oscillation, and diurnal precipitation cycles. Global cloud-resolving simulations show promise for future climate research. Such models avoid the liabilities associated with cumulus parameterization. Copyright 2005 by the American Geophysical Union."
"7201844203;7401538490;7403497924;","Influence of transient atmospheric circulation on the surface heating of the western Pacific warm pool",2005,"10.1029/2005GL022359","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22944449681&doi=10.1029%2f2005GL022359&partnerID=40&md5=5e68e3c2d051031ca42b0d81ffe58737","Trade and monsoonal winds converge to regions of the highest sea surface temperature (SST) in the equatorial western Pacific. These regions have the largest cloud cover and smallest wind speed. Both surface solar heating and evaporative cooling are weak. Data on surface heat fluxes show that the reduced evaporative cooling due to weakened winds exceeds the reduced solar heating due to enhanced cloudiness. The result is a maximum surface heating in the strong convective and high SST regions, which follow the seasonal march of the sun. As the Sun moves away from a convective region, the strong trade and monsoonal winds set in, and the evaporative cooling enhances, resulting in a net cooling of the surface. We conclude that the seasonal variation of evaporation associated with the seasonal variation of trade and monsoonal winds is one of the major factors that modulate the SST distribution of the Pacific warm pool. Copyright 2005 by the American Geophysical Union."
"56746732000;7005395607;7403534584;57189939159;6506620526;","Improving continuity of MODIS terrestrial photosynthesis products using an interpolation scheme for cloudy pixels",2005,"10.1080/01431160512331326693","https://www.scopus.com/inward/record.uri?eid=2-s2.0-19944410847&doi=10.1080%2f01431160512331326693&partnerID=40&md5=163d1436ce1d6f5f00cda8ad17c51877","The Moderate Imaging Spectroradiometer (MODIS) sensors onboard the NASA Terra and Aqua satellites provide the means for frequent measurement and monitoring of the status and seasonal variability in global vegetation phenology and productivity. However, while MODIS reflectance data are often interrupted by clouds, terrestrial processes like photosynthesis are continuous, so MODIS photosynthesis data must be able to cope with cloudy pixels. We developed cloud-correction algorithms to improve retrievals of the MODIS photosynthesis product (PSNnet) corresponding to clear sky conditions by proposing four alternative cloud-correction algorithms, which have different levels of complexity and correct errors associated with cloudy-pixel surface reflectance. The cloud-correction algorithms were applied at four weather stations, two fluxtower sites and the Pacific Northwest (PNW) region of the USA to test a range of cloud climatologies. Application of the cloud-correction algorithms increased the magnitude of both daily and annual MODIS PSNnet results. Our results indicate that the proposed cloud correction methods improve the current MODIS PSNnet product considerably at both site and regional scales and weekly to annual time steps for areas subjected to frequent cloud cover. The corrections can be applied as a post-processing interpolation of PSNnet, and do not require reprocessing of the MOD17A2 algorithm. © 2005 Taylor & Francis Group Ltd."
"7005133082;7005634455;7402498482;7005717609;","The climate of the McMurdo, Antarctica, region as represented by one year of forecasts from the Antarctic Mesoscale Prediction System",2005,"10.1175/JCLI3336.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-19144367641&doi=10.1175%2fJCLI3336.1&partnerID=40&md5=28afe6c7c953c2b09ab94ebd812f7dda","In response to the need for improved weather prediction capabilities in support of the U.S. Antarctic Program's Antarctic field operations, the Antarctic Mesoscale Prediction System (AMPS) was implemented in October 2000. AMPS employs a limited-area model, the Polar fifth-generation Pennsylvania State University - National Center for Atmospheric Research (PSU - NCAR) Mesoscale Model (MM5), optimized for use over ice sheets. Twice-daily forecasts from the 3.3-km resolution domain of AMPS are joined together to study the climate of the McMurdo region from June 2002 to May 2003. Annual and seasonal distributions of wind direction and speed, 2-m temperature, mean sea level pressure, precipitation, and cloud fraction are presented. This is the first time a model adapted for polar use and with relatively high resolution is used to study the climate of the rugged McMurdo region, allowing several important climatological features to be investigated with unprecedented detail. Orographic effects exert an important influence on the near-surface winds. Time-mean vortices occur in the lee of Ross Island, perhaps a factor in the high incidence of mesoscale cyclogenesis noted in this area. The near-surface temperature gradient is oriented northwest to southeast with the warmest temperatures in the northwest near McMurdo and the gradient being steepest in winter. The first-ever detailed precipitation maps of the region are presented. Orographic precipitation maxima occur on the southerly slopes of Ross Island and in the mountains to the southwest. The source of the moisture is primarily from the large synoptic systems passing to the northeast and east of Ross Island. A precipitation-shadow effect appears to be an important influence on the low precipitation amounts observed in the McMurdo Dry Valleys. Total cloud fraction primarily depends on the amount of open water in the Ross Sea; the cloudiest region is to the northeast of Ross Island in the vicinity of the Ross Sea polynya. © 2005 American Meteorological Society."
"8643088300;57189998431;7003897194;7004510293;7004864963;","New analytical method for the determination of levoglucosan, polyhydroxy compounds, and 2-methylerythritol and its application to smoke and rainwater samples",2005,"10.1021/es048363c","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16444368588&doi=10.1021%2fes048363c&partnerID=40&md5=6e55ad1d001b8545851af22fcee61e1b","Biomass burning is an important source of smoke aerosol particles, which contain water-soluble inorganic and organic species, and thus have a great potential of affecting cloud formation, precipitation, and climate on global and regional scales. In this study, we have developed a new chromatographic method for the determination of levoglucosan (a specific tracer for biomass burning particles), related polyhydroxy compounds, and 2-methyl-erythritol (recently identified as isoprene oxidation product in fine aerosols in the Amazon) in smoke and in rainwater samples. The new method is based on water extraction and utilizes ion-exclusion high-performance liquid chromatography (IEC-HPLC) separation and spectroscopic detection at 194 nm. The new method allows the analysis of wet samples, such as rainwater samples. In addition, aliquots of the same extracts can be used for further analyses, such as ion chromatography. The overall method uncertainty for sample analysis is 15%. The method was applied to the analysis of high-volume and size-segregated smoke samples and to rainwater samples, all collected during and following the deforestation fires season in Rondônia, Brazil. From the analysis of size-segregated samples, it is evident that levoglucosan is a primary vegetation combustion product, emitted mostly in the 0.175-1 μm size bins. Levoglucosan concentrations decrease below the detection limit at the end of the deforestation fires period, implying that it is not present in significant amounts in background Amazon forest aerosols. The ratio of daytime levoglucosan concentration to particulate matter (PM) concentration was about half the nighttime ratio. This observation is rationalized by the prevalence of flaming combustion during day as opposed to smoldering combustion during night. This work broadens the speciation possibilities offered by simple HPLC and demonstrates the importance of multianalysis of several kinds of samples for a deeper understanding of biomass burning aerosols. © 2005 American Chemical Society."
"9043658700;7006235542;55454856700;7103016965;7007114756;7102128820;","Numerical modelling of mixed-phase frontal clouds observed during the CWVC project",2005,"10.1256/qj.03.210","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27644514136&doi=10.1256%2fqj.03.210&partnerID=40&md5=d6ba2c378a9a7b60612fd857c74e4bd3","The Met Office's cloud-resolving model was used to model mixed-phase frontal clouds observed as part of the Clouds, Water Vapour and Climate programme between 1999 and 2001. The clouds were studied using the Met Office's C130 aircraft and the Chilbolton radar facility. In the model, precipitation forms in updraughts then falls, giving rise to regions of high radar reflectivity similar to those observed. The vertical motions were driven by conditional instability or shear instability. The sensitivity of the model results to the microphysics was examined by varying the number of primary ice nuclei and switching off the Hallett-Mossop process. It is demonstrated that the ice nucleation processes, both primary nucleation and secondary ice particle production, are key to the precipitation production in the cloud. This occurs both through the detail of cloud microphysics and the release of latent heat of fusion in the cloud. This is very sensitive to the details of the microphysics and can markedly change the cloud dynamics. In both cases it seems that the cloud dynamics can be simulated locally without considering the large-scale forcing. © Royal Meteorological Society, 2005."
"6603201254;7403646891;7004188723;","Tropical climate regimes and global climate sensitivity in a simple setting",2005,"10.1175/JAS3404.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18544388942&doi=10.1175%2fJAS3404.1&partnerID=40&md5=7327674209f40b29d012ccacde6b4c41","Multiple tropical climate regimes are found in an atmospheric general circulation model (AGCM) coupled to a global slab ocean when the model is forced by different values of globally uniform insolation. Even in this simple setting, convection organizes into an intertropical convergence zone (ITCZ) solely due to the effect of planetary rotation, as was found in Kirtman and Schneider, for a single value of insolation. Here the response to a range of insolation values is explored, and surprisingly, multiple climate regimes characterized by radically different ITCZ structures are found. In order from the coldest to warmest climates, these are a symmetric double ITCZ, a near-symmetric equatorial ITCZ, a transient asymmetric ITCZ, and a stable, strongly asymmetric ITCZ. The model exhibits hysteresis in the transition from t he near-symmetric to the strongly asymmetric ITCZ regimes when insolation is increased and then decreased. The initial transition away from symmetry can occur in the absence of air-sea coupling; however, the coupling is essential for the establishment and maintenance of the strongly asymmetric ITCZ. Wind-evaporation-SST feedback as well as the longwave radiative effects of clouds and water vapor on SSTs appear to be important in maintaining the asymmetric regime. The existence of multiple regimes in a single AGCM, and the dependence of these regimes on SST feedbacks, may have a bearing on the ITCZ simulation errors of current coupled climate models. The sensitivity of the global mean surface temperature generally decrea ses with increasing insolation, a consequence primarily of increasingly negative shortwave cloud forcing. Climate sensitivity measured across a regime transition can be much larger than the sensitivity within a single regime. © 2005 American Meteorological Society."
"8326850700;6602831555;7004194999;","Why radiative forcing might fail as a predictor of climate change",2005,"10.1007/s00382-004-0497-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17544376748&doi=10.1007%2fs00382-004-0497-7&partnerID=40&md5=f520bed708199c4218ea0b06013c98d1","Radiative forcing has been widely used as a metric of climate change, i.e. as a measure by which various contributors to a net surface temperature change can be quantitatively compared. The extent to which this concept is valid for spatially inhomogeneous perturbations to the climate system is tested. A series of climate model simulations involving ozone changes of different spatial structure reveals that the climate sensitivity parameter γ is highly variable: for an ozone increase in the northern hemisphere lower stratosphere, it is more than twice as large as for a homogeneous CO2 perturbation. A global ozone perturbation in the upper troposphere, however, causes a significantly smaller surface temperature response than CO2. The variability of the climate sensitivity parameter is shown to be mostly due to the varying strength of the stratospheric water vapour feedback. The variability of the sea-ice albedo feedback modifies climate sensitivity of perturbations with the same vertical structure but a different horizontal structure. This feedback is also the origin of the comparatively larger climate sensitivity to perturbations restricted to the northern hemisphere extratropics. As cloud feedback does not operate independently from the other feedbacks, quantifying its effect is rather difficult. However, its effect on the variability of γ for horizontally and vertically inhomogeneous perturbations within one model framework seems to be comparatively small. © Springer-Verlag 2005."
"7601492669;57202301596;56962915800;55703823500;","Large-scale atmospheric forcing by southeast Pacific boundary layer clouds: A regional model study",2005,"10.1175/JCLI3302.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844277289&doi=10.1175%2fJCLI3302.1&partnerID=40&md5=051646259f9aca69d14b113597980dd2","A regional model is used to study the radiative effect of boundary layer clouds over the southeast Pacific on large-scale atmosphere circulation during August-October 1999. With the standard settings, the model simulates reasonably well the large-scale circulation over the eastern Pacific, precipitation in the intertropical convergence zone (ITCZ) north of the equator, and marine boundary layer stratocumulus clouds to the south. In a sensitivity experiment with the radiative effect of liquid clouds south of the equator over the eastern Pacific artificially removed, boundary layer clouds south of the equator almost disappear and precipitation in the ITCZ is reduced by 15%-20%, indicating that the stratocumulus clouds over the southeast Pacific have both local and cross-equatorial effects. Examination of the differences between the control and sensitivity experiments indicates that clouds exert a net diabatic cooling in the inversion layer. In response to this cloud-induced cooling, an in situ anomalous high pressure system develops in the boundary layer and an anomalous shallow meridional circulation develops in the lower troposphere over the equatorial eastern Pacific. At the lower branch of this shallow circulation, anomalous boundary layer southerlies blow from the boundary layer high toward the northern ITCZ where the air ascends. An anomalous returning flow (northerly) just above the cloud layer closes the shallow circulation. This low-level anomalous shallow circulation enhances the subsidence over the southeast Pacific above the cloud layer, helping to maintain boundary layer clouds and temperature inversion there. Meanwhile, the strengthened cross-equatorial flow near the surface enhances moisture convergence and convection in the ITCZ north of the equator. This in turn strengthens the local, deep Hadley circulation and hence the large-scale subsidence and boundary layer clouds over the southeast Pacific. This positive feedback therefore enhances the interhemispheric climate asymmetry over the tropical eastern Pacific. © 2005 American Meteorological Society."
"9133004500;7202711754;","Cirrus parametrization and the role of ice nuclei",2005,"10.1256/qj.04.126","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27644487930&doi=10.1256%2fqj.04.126&partnerID=40&md5=47246104b2c17c14593f17592d675c2d","A parametrization of cirrus clouds formed by homogeneous nucleation is improved so that it can be used more easily in general-circulation models (GCMs) and climate models. The improved parametrization is completely analytical and requires no fitting of parameters to models or measurements; it compares well with full microphysical model results even when monodisperse aerosol particles are used in the parametrization to determine cirrus ice-crystal number densities. However, the presence of ice nuclei in the atmosphere can modify the formation of cirrus clouds. If sufficient ice particles have been generated by heterogeneous nucleation, the saturation ratio of the air parcel will never reach that required for homogeneous nucleation. We calculate the critical number density of ice nuclei, above which homogeneous nucleation will be suppressed. The critical number density depends on the temperature, the updraught velocity, and the supersaturation at which ice nuclei activate. The theory points to key uncertainties in our observations of ice nuclei in the upper troposphere; for ice nuclei that activate at relatively low supersaturations, number density is more important than a precise knowledge of the activation supersaturation. Overall, the theory provides a general framework within which to interpret observations and the results of full microphysical cloud models. The theory can provide analytical test cases as benchmarks for the testing of models in development, and can be implemented itself into larger-scale atmospheric models, such as GCMs. © Royal Meteorological Society, 2005."
"6603703707;6602158966;","Historical climate variation in Belize (Central America) as recorded in scleractinian coral skeletons",2005,"10.2110/palo.2004.p04-09","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17144406912&doi=10.2110%2fpalo.2004.p04-09&partnerID=40&md5=70e9998c4aad67fe6fc2efa663c8b584","Three cores from the scleractinian coral Montastraea faveolata and one core from the scleractinian coral Siderastrea siderea from the Belize barrier and atoll reef complex, Central America, were analyzed with regard to sclerochronology (skeletal extension rates) and stable isotope geochemistry (δ 18O and δ 13C). The core material covers the time span from 1815 to 2000. The four coral time series were compared with available instrumental climate data, such as sea surface temperatures (GISST), cloud cover (GHCN), and precipitation (COADS). Skeletal extension rates measured in the cores average 8.5-14 mm / year in M. faveolata and 8 mm / year in S. siderea. No systematic correlations between extension rates and instrumental climate data were detected. Annual variation in oxygen isotopes is 0.6-08‰, which accounts for monthly averages of sea-surface water temperature fluctuations of 3-4°C. In three cores from the Belize shelf and barrier reef, negative correlations of δ 18O with the GISST 2.3b data were observed. Time series analyses of the oxygen isotope data in these three cores revealed a decadal periodicity (10-15 years), which are attributed here to the influence of the Atlantic sea surface temperature (SST) dipole variation. Three- to six-year periodicities, indicative of the El Niño Southern Oscillation (ENSO), in the same data are only weakly developed. Carbon isotopes of shallow-water corals also exhibit negative correlations with the GISST data. It is speculated that warmer years were characterized by increased cloud cover leading to reduced photosynthesis rates in the corals. Indeed, there is a negative correlation between δ 13C and historic cloud-cover data. Carbon isotopes in the Belize shelf and barrier reef cores further exhibit general trends towards lighter values in time indicating the uptake of fossil fuel CO 2 in the coral skeletons. A proxy data time series from a core from the restricted Turneffe Atoll lagoon differs from those of the Belize shelf and barrier reef cores, and there are fewer systematic correlations with historical climate and proxy data. This is probably a consequence of the strong influence of local environmental factors, which obliterate broader scale environmental parameters. First analyses of oxygen isotopes in fossil (Holocene) coral cores of M. faveolata indicate higher SSTs around 7,000 ybp in Belize as compared to older, younger, and modern samples. Copyright © 2005, SEPM (Society for Sedimentary Geology)."
"7004304399;","Climate policy in an adapting world",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-18844452367&partnerID=40&md5=a7203a486de4e325c62d993805afc906","The scientific community began to come to grips with the issue of global climate change more than three decades ago. While it is safe to say that researchers have made considerable progress in advancing our understanding of the climate system and its sensitivity to human-induced increases in the concentrations of greenhouse gases, it is equally safe to say that this progress has not always lead to a reduction in the uncertainty that clouds our vision of how the future will unfold. No matter what, different communities are going to have to confront change in their environments, and they will do so in different ways. But profound and persistent uncertainty will undermine the ability of the conventional cost-benefit approach to inform their decisions adequately. This conclusion is unsettling for people who are comfortable comparing costs and benefits in their own lives and in their communities, but an alternative approach exists: Apply the same risk-management approach that has inspired people to buy insurance against the intolerable consequences of events such as house fires and serious disease and has inspired their governments to create social safety nets."
"55573647400;7006783796;7004364155;7004325649;7406061582;6506827279;55947099700;7004174939;26643408200;6602843047;","Two MODIS aerosol products over ocean on the Terra and Aqua CERES SSF datasets",2005,"10.1175/JAS3383.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20844454106&doi=10.1175%2fJAS3383.1&partnerID=40&md5=735159021405fa6de34a07f10f76bcad","Understanding the impact of aerosols on the earth's radiation budget and the long-term climate record requires consistent measurements of aerosol properties and radiative fluxes. The Clouds and the Earth's Radiant Energy System (CERES) Science Team combines satellite-based retrievals of aerosols, clouds, and radiative fluxes into Single Scanner Footprint (SSF) datasets from the Terra and Aqua satellites. Over ocean, two aerosol products are derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) using different sampling and aerosol algorithms. The primary, or M, product is taken from the standard multispectral aerosol product developed by the MODIS aerosol group while a simpler, secondary [Advanced Very High Resolution Radiometer (AVHRR) like], or A, product is derived by the CERES Science Team using a different cloud clearing method and a single-channel aerosol algorithm. Two aerosol optical depths (AOD), τA1, and τ A2, are derived from MODIS bands 1 (0.644 μm) and 6 (1.632 μm) resembling the AVHRR/3 channels 1 and 3A, respectively. On Aqua the retrievals are made in band 7 (2.119 μm) because of poor quality data from band 6. The respective Ångström exponents can be derived from the values of τ. The A product serves as a backup for the M product. More importantly, the overlap of these aerosol products is essential for placing the 20+ year heritage AVHRR aerosol record in the context of more advanced aerosol sensors and algorithms such as that used for the M product. This study documents the M and A products, highlighting their CERES SSF specifics. Based on 2 weeks of global Terra data, coincident M and A AODs are found to be strongly correlated in both bands. However, both domains in which the M and A aerosols are available, and the respective τ/a statistics significantly differ because of discrepancies in sampling due to differences in cloud and sun-glint screening. In both aerosol products, correlation is observed between the retrieved aerosol parameters (τ/ a) and ambient cloud amount, with the dependence in the M product being more pronounced than in the A product."
"6701522828;","Forecasting extreme events in the tropical Indian Ocean sector climate",2005,"10.1016/j.dynatmoce.2004.10.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17544375305&doi=10.1016%2fj.dynatmoce.2004.10.012&partnerID=40&md5=26f3e7c2b91dfe73a0492acc24204eed","Prospects for forecasting climate variability over the tropical Indian Ocean sector, specifically extreme positive events of the Indian Dipole Mode (IDM), with lead times of a season or more are investigated using the NASA Seasonal-to-Interannual Prediction Project (NSIPP) coupled-model system. The coupled system presents biases in its climatology over the Indian Ocean sector, which include (i) warmest sea-surface temperatures (SSTs) occurring in the central equatorial basin rather than on the eastside with the eastern (western) tropical SSTs up to 1 °C too cool (warm), (ii) a too northwest lying InterTropical Convergence Zonal over the ocean in boreal fall, (iii) a thermocline shallower (deeper) than observed west of Sumatra-Java (north of Madagascar), (iv) a delay of about a month in the onset (cessation) of the southwest (southeast) monsoon in the west (east) in boreal spring (fall). These biases affect the effectiveness of the SST-clouds-shortwave radiation negative feedback, the sensitivity of SST to wind-stress perturbations, and the character of equatorial coupled ocean-atmosphere modes. Despite these biases, ensemble hindcasts of the SST anomalies averaged over the eastern and western poles of the IDM for the decade 1993-2002, which included extreme positive events in 1994 and 1997/1998, are encouragingly good at 3-months lead. The onset of the 1997/1998-event is delayed by about a month, though the peak and decay are correctly timed. At 6-months lead-time, the forecast at the eastern pole deteriorates with either positive or negative false alarms generated each boreal fall. The forecast at the western pole remains good. © 2004 Elsevier B.V. All rights reserved."
"6603742400;7004101548;","UV index forecasting on a global scale",2005,"10.1127/0941-2948/2005/0029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33144464690&doi=10.1127%2f0941-2948%2f2005%2f0029&partnerID=40&md5=d1b0dbe4cfdbc4c05a5a22ef6c13b3a4","A method is presented to forecast the UV Index (UVI) on a global scale for up to 3 days, taking into account ozone, aerosol, cloudiness, altitude and albedo. Particular consideration is made for the adjustment of the UVI to altitude and for seasonal changes in aerosol optical depth. The UVI describes the level of erythemal weighted solar irradiance and consequently is an indicator of the potential for skin damage by UV radiation. Thus the UVI is an important vehicle to raise public awareness of the risks of UV radiation, and forecasted UVI may help to adapt the human behaviour. The UVI is forecasted by the German Meteorological Service (DWD) using adequate values of the relevant atmospheric and surface properties. The UVI is calculated via lookup tables valid for sea level, clear sky conditions, an aerosol optical depth at 550 nm (AOD) of 0.2, and an albedo of 3 %. The lookup tables have a high resolution in total column ozone and sun zenith angle. The ozone values are forecasted within the global numerical weather prediction model GME of DWD. The module structure of the UV model allows for a subsequent adjustment of UVI to changes in AOD, to the topography, to the albedo of predicted snow, and to forecasted cloudiness, the latter by using empirical cloud modification factors. The factor applied to account for changes in AOD depends on solar zenith angle and on aerosol single scattering albedo, and that for altitude effects additionally on AOD. Since forecasts of AOD are not yet available, regional monthly mean values of AOD have been derived from MODIS and TOMS measurements. The forecasted UVI for all effective atmospheric conditions are compared with measurements at 12 locations in Europe for the summer seasons 1999 and 2003. 80 % of the forecasts for all atmospheric conditions were within the range of ±1 UVI; the predominant error can be attributed to cloudiness. © Gebrüder Borntraeger, Berlin, Stuttgart 2005."
"24322892500;6701859365;7201463831;7201798916;7004174939;16185051500;6602137800;35554446700;","EOS terra aerosol and radiative flux validation: An overview of the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) experiment",2005,"10.1175/JAS3398.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18544390219&doi=10.1175%2fJAS3398.1&partnerID=40&md5=ff114149512dae6496fc04818978bfaf","NASA developed an Earth Observing System (EOS) to study global change and reduce uncertainties associated with aerosols and other key parameters controlling climate. The first EOS satellite, Terra, was launched in December 1999. The Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) field campaign was conducted from 10 July to 2 August 2001 to validate several Terra data products, including aerosol properties and radiative flux profiles derived from three complementary Terra instruments: the Clouds and the Earth's Radiant Energy System (CERES), the Multiangle Imaging Spectroradiometer (MISR), and the Moderate Resolution Imaging Spectroradiometer (MODIS). CERES, MISR, and MODIS are being used to investigate the critical role aerosols play in modulating the radiative heat budget of the earth-atmosphere system. CLAMS' primary objectives are to improve understanding of atmospheric aerosols, to validate and improve the satellite data products, and to test new instruments and measurement concepts. A variety of in situ sampling devices and passive remote sensing instruments were flown on six aircraft to characterize the state of the atmosphere, the composition of atmospheric aerosols, and the associated surface and atmospheric radiation parameters over the U.S. eastern seaboard. Aerosol particulate matter was measured at two ground stations established at Wallops Island, Virginia, and the Chesapeake Lighthouse, the site of an ongoing CERES Ocean Validation Experiment (COVE) where well-calibrated radiative fluxes and Aerosol Robotic Network (AERONET) aerosol properties have been measured since 1999. Nine coordinated aircraft missions and numerous additional sorties were flown under a variety of atmospheric conditions and aerosol loadings. On one ""golden day"" (17 July 2001), under moderately polluted conditions with midvisible optical depths near 0.5, all six aircraft flew coordinated patterns vertically stacked between 100 and 65 000 ft over the COVE site as Terra flew overhead. This overview presents a description of CLAMS objectives, measurements, and sampling strategies. Key results, reported in greater detail in the collection of papers found in this special issue, are also summarized. © 2005 American Meteorological Society."
"7003626306;35414069200;55730024500;35494722400;7404419577;7003995144;57198726737;7201655612;7404506656;56900025900;6602327740;6603712566;","Measurement of low amounts of precipitable water vapor using ground-based millimeterwave radiometry",2005,"10.1175/JTECH1711.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20444478583&doi=10.1175%2fJTECH1711.1&partnerID=40&md5=4f9cfacb67e37109b1d9e1416d8dcf24","Extremely dry conditions characterized by amounts of precipitable water vapor (PWV) as low as 1-2 mm commonly occur in high-latitude regions during the winter months. While such dry atmospheres carry only a few percent of the latent heat energy compared to tropical atmospheres, the effects of low vapor amounts on the polar radiation budget - both directly through modulation of longwave radiation and indirectly through the formation of clouds - are considerable. Accurate measurements of PWV during such dry conditions are needed to improve polar radiation models for use in understanding and predicting change in the climatically sensitive polar regions. To this end, the strong water-vapor absorption line at 183.310 GHz provides a unique means of measuring low amounts of PWV. Weighting function analysis, forward model calculations based upon a 7-yr radiosonde dataset, and retrieval simulations consistently predict that radiometric measurements made using several millimeter-wavelength (MMW) channels near the 183-GHz line, together with established microwave (MW) measurements near the 22.235-GHz water-vapor line and ∼31-GHz atmospheric absorption window can be used to determine within 5% uncertainty the full range of PWV expected in the Arctic. This combined capability stands in spite of accuracy limitations stemming from uncertainties due to the sensitivity of the vertical distribution of temperature and water vapor at MMW channels. In this study the potential of MMW radiometry using the 183-GHz line for measuring low amounts of PWV is demonstrated both theoretically and experimentally. The study uses data obtained during March 1999 as part of an experiment conducted at the Department of Energy's Cloud and Radiation Testbed (CART) site near Barrow, Alaska. Several radiometers from both NOAA and NASA were deployed during the experiment to provide the first combined MMW and MW ground-based dataset during dry Arctic conditions. Single-channel retrievals of PWV were performed using the MW and MMW data. Discrepancies in the retrieved values were found to be consistent with differences observed between measured brightness temperatures (TBs) and forward-modeled TBs based on concurrent radiosonde profiles. These discrepancies are greater than can be explained by radiometer measurement error alone; errors in the absorption models and uncertainty in the radiosonde measurements contribute to the discrepancies observed. The measurements, retrieval technique, and line model discrepancies are discussed, along with difficulties and potential of MMW/MW PWV measurement. © 2005 American Meteorological Society."
"7004174939;35464731600;55947099700;7006421484;7201734141;7201798916;57198938123;7003397919;7404061081;7801610570;7005793702;7004587891;7005399437;","The MODIS aerosol algorithm, products, and validation",2005,"10.1175/JAS3385.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20844440199&doi=10.1175%2fJAS3385.1&partnerID=40&md5=b19afbff320ef3fd15e7cfe7995ba2dd","The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard both NASA's Terra and Aqua satellites is making near-global daily observations of the earth in a wide spectral range (0.41-15 μm). These measurements are used to derive spectral aerosol optical thickness and aerosol size parameters over both land and ocean. The aerosol products available over land include aerosol optical thickness at three visible wavelengths, a measure of the fraction of aerosol optical thickness attributed to the fine mode, and several derived parameters including reflected spectral solar flux at the top of the atmosphere. Over the ocean, the aerosol optical thickness is provided in seven wavelengths from 0.47 to 2.13 μm. In addition, quantitative aerosol size information includes effective radius of the aerosol and quantitative fraction of optical thickness attributed to the fine mode. Spectral irradiance contributed by the aerosol, mass concentration, and number of cloud condensation nuclei round out the list of available aerosol products over the ocean. The spectral optical thickness and effective radius of the aerosol over the ocean are validated by comparison with two years of Aerosol Robotic Network (AERONET) data gleaned from 132 AERONET stations. Eight thousand MODIS aerosol retrievals collocated with AERONET measurements confirm that one standard deviation of MODIS optical thickness retrievals fall within the predicted uncertainty of Δτ = ±0.03 ±0.05τ over ocean and Δτ = ±0.05 ± 0.15τ over land. Two hundred and seventy-one MODIS aerosol retrievals collocated with AERONET inversions at island and coastal sites suggest that one standard deviation of MODIS effective radius retrievals falls within Δreff = ±0.11 μm. The accuracy of the MODIS retrievals suggests that the product can be used to help narrow the uncertainties associated with aerosol radiative forcing of global climate. © 2005 American Meteorological Society."
"7006308157;6602781511;","Simultaneous analysis of climatic trends in multiple variables: An example of application of multivariate statistical methods",2005,"10.1002/joc.1146","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17144419661&doi=10.1002%2fjoc.1146&partnerID=40&md5=d0369a3b399c6b1f178a2267ef70ee1e","This paper introduces into the research on trends in climate elements the multivariate statistical methods, namely principal component analysis (PCA) and cluster analysis, and demonstrates the benefits of their use. We also introduce the idea of normalization of the trends by their confidence interval, which facilitates the comparison of trends among different variables and allows their fair treatment by the multivariate methods. The study is performed for 11 climate elements at 21 stations in the Czech Republic. Temperatures are rising in winter, spring and summer, but decreasing in autumn. Consistent with these changes are trends in sunshine duration, cloudiness and daily temperature range. Correlation analysis and PCA confirm the mutual relationships among the trends in these variables in all seasons. The two methods also uncover other groups of variables whose trends vary similarly at individual stations, which, however, occur in several seasons only, not throughout the year. This implies that the trend analyses based on seasonal values should be preferred to analyses of annual trends. The cluster analysis of stations allows the quantification of the spatial consistency of trends. The groupings of stations are spatially incoherent and seasonally variable, which indicates that local peculiarities of the relatively complex terrain affect the station trends to a considerable extent. Copyright © 2005 Royal Meteorological Society."
"7006712143;9276570300;6603729297;8509491300;8208591500;7004022660;6602506226;7006354036;7005601996;","Cloud condensation nucleus production from nucleation events at a highly polluted region",2005,"10.1029/2004GL022092","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20044371238&doi=10.1029%2f2004GL022092&partnerID=40&md5=9bcaae79b6ef8a2ca1cddb554c282e31","Atmospheric nucleation events have received increasing attention as a potentially important source of aerosol particles affecting climate and human health. Here, we report 2.5 years of continuous nucleation observations from San Pietro Capofiume, Italy (44°39′N, 11°37′W). We show that nucleation events occur frequently in the Po Valley region, even though the region is rather polluted with high pre-existing particle concentrations. The nucleation events are often very intensive, and the newly formed particles can grow to sizes as large as 100-200 nm in diameter within a few hours. Our calculations of the enhancement of particle number concentrations in different size ranges and comparison with steady-state and regional emission estimates indicate that the nucleation events produce a significant fraction of particles larger than 100 nm, and thus constitute an important source of cloud condensation nuclei (CCN). Copyright 2005 by the American Geophysical Union."
"8397494800;25941200000;7202208382;6701346974;7006204393;","Global consequences of interactions between clouds and radiation at scales unresolved by global climate models",2005,"10.1029/2004GL020945","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20044393865&doi=10.1029%2f2004GL020945&partnerID=40&md5=feef0e2248dddd3038b09a16a60d6c31","Horizontal grid-spacings in conventional atmospheric general circulation models (GCMs) are typically between 100 km and 500 km. Hence, many processes are unresolved and must be parameterized in terms of resolved variables. Development of satisfactory parameterizations of meanfield (or domain-average) cloud and radiative processes has been frustratingly slow. Moreover, the sensitivity of conventional GCMs to unresolved interactions between cloud and radiation is unknown. In this study, the native cloud parameterization of a GCM was replaced, in each GCM grid column, by a two-dimensional cloud system-resolving model (CSRM). The CSRMs used a horizontal grid-spacing of 4 km. They were employed to assess the sensitivity of a GCM to the inclusion of interactions between cloud and radiation at unresolved scales as well as sensitivity to accurate domain-average radiative flux profiles. For a simulation spanning one season, unresolved cloud-radiation interactions affect the statistics of average cloud fraction and average cloud-radiative effect, while the accuracy of domain-average radiative flux profiles had less effect. Copyright 2005 by the American Geophysical Union."
"7004299063;","Cooling following large volcanic eruptions corrected for the effect of diffuse radiation on tree rings",2005,"10.1029/2004GL022116","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20044374052&doi=10.1029%2f2004GL022116&partnerID=40&md5=469c4462f9bef402ec5c22ef0e6b0caa","The lack of a larger cooling in proxy records of climate change following large volcanic eruptions such as those of Tambora in 1815 and Krakatau in 1883 has long been a puzzle for climatologists. These records, however, may have been biased by enhanced tree growth for several years following each eruption induced by additional diffuse radiation caused by the stratospheric volcanic aerosol clouds from the eruptions. By comparing proxy reconstructions of climate with and without tree ring data, this effect is demonstrated for the five largest eruptions for the, period 1750-1980. When proxy records of Northern Hemisphere climate change are corrected for this proposed diffuse effect, there is no impact on climate change for time scales longer than 20 years. However, it now appears that there was a hemispheric cooling of about 0.6°C for a decade following the unknown volcanic eruption of 1809 and Tambora in 1815, and a cooling of 0.3°C for several years following the Krakatau eruption of 1883. Copyright 2005 by the American Geophysical Union."
"7006961728;7407797613;","The Arctic climate paradox: The recent decrease of the Arctic Oscillation",2005,"10.1029/2004GL021752","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20044383793&doi=10.1029%2f2004GL021752&partnerID=40&md5=214c646b4561f7b26c33f321fb6977d4","A current paradox is that many physical and biological indicators of Arctic change - summer sea-ice extent, spring surface air temperature and cloud cover, and shifts in vegetation and other ecosystems - show nearly linear trends over the previous two and a half decades, while the Arctic Oscillation, a representative atmospheric circulation index often associated with Arctic change, has had a different, more episodic behavior, with a near-neutral or negative phase for 6 of the last 9 years (1996-2004) following a positive phase (1989-1995). Stratospheric temperature anomalies over the Arctic, which serve as an index of the strength of the polar vortex, also show this episodic character. Model projections of Arctic temperature for 2010-2029 show model-to-model and region-to-region differences suggesting large variability in the future response of atmospheric circulation to external forcing. Thus internal processes in the western Arctic may have a larger role in shaping the present persistence of Arctic change than has been previously recognized. Copyright 2005 by the American Geophysical Union."
"55421346900;6603764342;23026674500;35570811600;26643563100;","Synoptic patterns associated with large summer forest fires in Portugal",2005,"10.1016/j.agrformet.2004.12.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14744268312&doi=10.1016%2fj.agrformet.2004.12.007&partnerID=40&md5=95694a289368aee6adaabc9dacd88f32","Time series of the total annual burnt area in Portugal reveal two main features, a large inter-annual variability and a positive trend since the early 80 s. Here we show that inter-annual variability is partly due to the amount of precipitation in the fire season and in the preceding late spring season and partly to the occurrence of atmospheric circulation patterns that induce extremely hot and dry spells over western Iberia. On the other hand, the observed positive trend of burnt area is mainly related to changes in farming and land use. Meteorological conditions play a fundamental role, both in the ignition and during the fire spread. The description of spatial and temporal variability of wildfire characteristics is performed using the comprehensive fire data set (between 1980 and 2000) from the Portuguese forest service. We show that the vast majority of the burnt area in Portugal (80%) is due to fire events that occurred on in a very small number (10%) of summer days. Large-scale climatic and dynamical meteorological fields were retrieved from the NCAR/NCEP Reanalyses data sets for the 1961-2000 period and composites were then obtained for the 10% of summer days associated with the highest values of burnt area. Anomaly fields of climate variables (e.g. 850 hPa temperature and relative humidity) are interpreted based on physical mechanisms associated with dynamical variables such as the surface wind field or the 500 hPa geopotential height. Overall, one may state that synoptic patterns of most analysed meteorological fields present statistically significant anomalies over western Iberia. In particular, composites of geopotential height for mid (500 hPa) and lower (850 hPa) troposphere show that large forest fires in Portugal occur when the atmospheric circulation forms a prominent ridge over the Iberian peninsula with the flow being dominated by a strong meridional component. Near the surface, wind and sea level pressure anomalies show that these days are associated with south-easterly conditions, with a strong anomalous advection from northern Africa that is further heated when crossing the central Iberian plateau. Large asymmetries between minimum and maximum temperatures composites are analysed taking into account the lack of cloud cover and corresponding precipitation. Finally, we present a linear model based on the monthly precipitation and the occurrence of previously identified wildfire prone atmospheric patterns. The developed model gives a correlation coefficient of 0.8 between the observed and modeled extent of burnt area during the summer. © 2005 Elsevier B.V. All rights reserved."
"8705440100;23995325300;26643041500;35461255500;7003984086;","Measurements of cloud droplet activation of aerosol particles at a clean subarctic background site",2005,"10.1029/2004JD005200","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20044388778&doi=10.1029%2f2004JD005200&partnerID=40&md5=d3606f13b5428b78163db6b9da1a9f5a","Two years of continuous aerosol particle size distribution measurements provided the basis for this cloud droplet activation study. The cloud droplet activation of aerosol particles was studied in Pallas, a clean background site in northern Finland. A slightly different approach compared with traditional methods is presented by measuring simultaneously the cloud interstitial particle size spectrum and a nearby out-of-cloud particle size spectrum. The main advantage of this approach is that one can determine the activated fraction of different-size particles over the whole submicron-size range and that a large number of cloud activation events can be analyzed. The number of cloud droplet activation days peaked in late autumn and was lowest in summer. The annual variation of ""cloud droplet activation"" events followed the annual pattern of low clouds (those below 1000 m). A relation was found between the total particle number concentration outside the cloud and the number of activated particles. A larger particle concentration led to a higher number of activated particles, a lower activation percent, and a larger activation diameter (D50). D50 was on average 80 run and varied from 50 to 128 nm. The average fraction of activated particles during the cloud events was 47% and varied from 9 to 86%. The cleaner and colder air masses from the northern Atlantic or the Arctic Ocean had, on average, 15 nm lower D50 than the more polluted air masses from south and east containing more particles. The annual variation of the number of the activated particles and other variables were also closely related to the annual variation of particle concentration (high in summer and low in winter). On average 87 and 30% of accumulation and Aitken mode particles, respectively, were activated. Aitken mode particles were observed to cover up to 55% of the total number of activated particles (i.e., number of formed droplets), which demonstrates that they have a significant effect on cloud droplet activation and must be taken into account when estimating the aerosol indirect climate effects. Copyright 2005 by the American Geophysical Union."
"11939918300;6602887222;","Sensitivity of the European climate to aerosol forcing as simulated with a regional climate model",2005,"10.1029/2004JD005335","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20044365643&doi=10.1029%2f2004JD005335&partnerID=40&md5=6c73ca586fac9baad43c8d92c0556a58","Despite the recognized importance of atmospheric aerosols for the simulation of present and future climate, the quantification and understanding of their impacts are still poorly constrained. Difficulties arise especially on a regional scale, owing to the short atmospheric lifetime of the aerosol particles combined with the limited observational possibilities. In this study the sensitivity of the European climate to a change in its aerosol forcing is investigated using a regional climate model (RCM) and two aerosol distributions. The original RCM aerosol climatology of Tanre et al. (1984) and a modified version of the Global Aerosol Data Set are considered, while their direct radiative forcing, together with the induced climatic response, is simulated through two five-year integrations of the RCM. The comparison of both sensitivity experiments demonstrates that the uncertainties associated with the aerosol forcing, as expressed here through the use of two different data sets, significantly influence the modeled climate on a regional scale and thus the model biases (in our case the well-known cold bias over the Iberian Peninsula and the summer dry bias over the Danube region). The observed model climatic response can be related to the modification of the radiation budget, also affecting the water cycle. The latter leads to the release of several feedbacks, i.e., cloud and water vapor feedbacks as land-atmosphere interactions, which either intensify or counteract the expected aerosol forcing, depending on the atmospheric conditions, vegetation state, and soil water content. Copyright 2005 by the American Geophysical Union."
"6602560015;6602631793;7006813055;7005395283;8636475800;35607774000;7401935516;","Vertical distribution of Saharan dust over Rome (Italy): Comparison between 3-year model predictions and lidar soundings",2005,"10.1029/2004JD005480","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20044380788&doi=10.1029%2f2004JD005480&partnerID=40&md5=0fc9359415c6c0ec62402d8394c2856a","Mineral dust particles loaded into the atmosphere from the Sahara desert represent one major factor affecting the Earth's radiative budget. Regular model-based forecasts of 3-D dust fields can be used in order to determine the dust radiative effect in climate models, in spite of the large gaps in observations of dust vertical profiles. In this study, dust forecasts by the Tel Aviv University (TAU) dust prediction system were compared to lidar observations to better evaluate the model's capabilities. The TAU dust model' was initially developed at the University of Athens and later modified at Tel Aviv University. Dust forecasts are initialized with the aid of the Total Ozone Mapping Spectrometer aerosol index (TOMS AI) measurements. The lidar soundings employed were collected at the outskirts of Rome, Italy (41.84°N, 12.64°E) during the high-dust activity season from March to June of the years 2001, 2002, and 2003. The lidar vertical profiles collected in the presence of dust were used for obtaining statistically significant reference parameters of dust layers over Rome and for model versus lidar comparison. The Barnaba and Gobbi (2001) approach was used in the current study to derive height-resolved dust volumes from lidar measurements of backscatter. Close inspection of the juxtaposed vertical profiles, obtained from lidar and model data near Rome, indicates that the majority (67%) of the cases under investigation can be classified as good or acceptable forecasts of the dust vertical distribution. A more quantitative comparison shows that the model predictions are mainly accurate in the middle part of dust layers. This is supported by high correlation (0.85) between lidar and model data for forecast dust volumes greater than the threshold of 1 × 10-12 cm3/cm3. In general, however, the model tends to underestimate the lidar-derived dust volume profiles. The effect of clouds in the TOMS detection of AI is supposed to be the main factor responsible for this effect. Moreover, some model assumptions on dust sources and particle size and the accuracy of model-simulated meteorological parameters are also likely to affect the dust forecast quality. Copyright 2005 by the American Geophysical Union."
"6603809220;56611366900;","A smaller global estimate of the second indirect aerosol effect",2005,"10.1029/2004GL021922","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16444371627&doi=10.1029%2f2004GL021922&partnerID=40&md5=3d9a40f0920d74859f7402f501d4f2f9","Global estimates of the indirect aerosol effect much larger than 1 W m-2 in magnitude are difficult to reconcile with observations, yet climate models give estimates between -1 and -4.4 W m-2. We use a climate model with a new treatment of autoconversion to reevaluate the second indirect aerosol effect. We obtain a global-mean value of -0.28 W m-2, compared to -0.71 W m-2 with the autoconversion treatment most often used in climate models. The difference is due to (1) the new scheme's smaller autoconversion rate, and (2) an autoconversion threshold that increases more slowly with cloud droplet concentration. The impact of the smaller autoconversion rate shows the importance of accurately modeling this process. Our estimate of the total indirect aerosol effect on liquid-water clouds changes from -1.63 to -1.09 W m-2. Copyright 2005 by the American Geophysical Union."
"6505942221;7405460591;","The capacitance of solid and hollow hexagonal ice columns",2005,"10.1029/2004GL021771","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20444453690&doi=10.1029%2f2004GL021771&partnerID=40&md5=d87e188c74b63c1e07ebb3d886d16173","The capacitances of solid and hollow hexagonal ice columns are calculated using the classical electrostatic analogy theory. Finite element techniques are used to solve the Laplace equation to obtain water vapor density distribution from which the capacitance can be determined. The results show that solid and hollow columns of the same dimensions have nearly the same capacitance despite the existence of cavities in the latter, which implies the same mass growth rates of the two. The computed capacitances agree well with experimental measurements. Since the volume of a hollow column is smaller than that of a solid column of the same dimensions, the same mass growth rate prompts the hollow column to grow faster in linear dimensions and hence interact stronger with radiation. This will have important implications on the cirrus influence on climate. Copyright 2005 by the American Geophysical Union."
"7102505167;24332424400;","Solar radiation climate change over southern Africa and an assessment of the radiative impact of volcanic eruptions",2005,"10.1002/joc.1134","https://www.scopus.com/inward/record.uri?eid=2-s2.0-15744373037&doi=10.1002%2fjoc.1134&partnerID=40&md5=d5dd8c0fcf81cfdf626f1d002f3b857f","Spatial and temporal variability in global, diffuse, and horizontal direct irradiance and sunshine duration has been evaluated at eight stations in South Africa and two stations in Namibia where the time series range between 21 and 41 years. Global and direct irradiance and sunshine duration decrease from northwest to southeast; diffuse irradiance increases toward the east. Annually averaged global irradiance Ga decreased between 1.3% (2.8 W m-2) and 1.7% (4.4 W m-2) per decade at Bloemfontein, Cape Town, Durban, Pretoria, and Upington. Annually averaged diffuse irradiance Da decreased 5.2% (3.0 W m-2) per decade at Grootfontein and 4.2% (3.1 W m-2) per decade at Port Elizabeth. Annual direct irradiance Ba decreased 2.1% (3.5 W m-2) per decade at Cape Town and 2.8% (5.7 W m-2) per decade at Alexander Bay. A simultaneous decrease in annually averaged daily sunshine duration Sa may have contributed to the decrease in Ba at Alexander Bay and the decrease in Ga at Pretoria. Increases in aerosols may have contributed to the observed decrease in Ga at Cape Town and Durban, and the decrease in Da at Grootfontein may be due to a decrease in aerosols. On average, variability in Sa explains 89.0%, 50.4%, and 89.5% of the variance in Ga, Da, and Ba respectively. The radiative response to changes in sunshine duration is greater for direct irradiance than for global and diffuse. In the 2 years following the 1963 Mount Agung eruption in Indonesia, changes in global irradiance over southern Africa were small and inconsistent. At eight stations, diffuse irradiance increased 21.9% (13.3 W m-2) on average and direct irradiance decreased 8.7% (15.5 W m-2 ). After the 1982 El Chichón eruption in Mexico, global irradiance increased at two stations and decreased at seven stations. Eight stations witnessed an increase in diffuse irradiance averaging 7.2% (4.0 W m-2 ) and a decrease in direct irradiance of 5.0% (9.0 W m-2 ). The contribution of changes in cloud cover to the observed changes in irradiances appears to be small. Following the 1991 Mount Pinatubo eruption in the Philippines, diffuse irradiance increased an average of 18.8% (10.0 W m-2) at three stations and direct irradiance decreased by 7.2% (13.0 W m-2). Copyright © 2005 Royal Meteorological Society."
"7004462010;7006613432;","Role of primary admixtures in the formation and fluctuation of the Earth's climate",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-21144458191&partnerID=40&md5=aa5abda117c545a3ffd5f366c7d9996e","It should be emphasized that water in all three of its sates - gaseous (water vapor), liquid (hydrosphere and clouds), and solid (ice and snow) - serves as the main regulator in the formation of the Earth's climate and its fluctuations. The role of carbon dioxide and other greenhouse admixtures is several orders of magnitude lower as compared with that of water vapor and clouds. Copyright © 2005 by Pleiades Publishing, Inc."
"7006518289;","Climate change commitment in the twenty-first and twenty-second centuries",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-17644404067&partnerID=40&md5=3bc664fe857454c89070feff9d8926cf","The newly developed Community Climate System Model Version 3 (CCSM3) with increased horizontal resolution was used to address climate-change commitment. It was found that even if concentrations of all greenhouse gases (GHGs) were stabilized at year 2000 levels, 0.4°C more warming could still occur by the end of 21st century. At the end of 21st century, the warming in the tropical Pacific will resemble an El Nino-like response, likely due to cloud feedbacks in the model."
"7402311929;13608069100;7402291655;7202935976;","Local climate sensitivity to the three gorges dam",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-17644381620&partnerID=40&md5=3dd32353d7a9ac0fa12b3aa68985f3b1","The change in surface characteristics in the Three Gorges area from steep, vegetated terrain to a large, flat, saturated surface that evaporates at the potential evaporation rate was examined. Focusing on changes in local circulation patterns, an attempt was made to quantify the relative change in tempature, precipitation, and energy fluxes using a regional atmospheric model coupled to a land-surface model. Initial analyses of simulations suggest that increased surface evaporation leads to a colder surface with decreased sensible heat flux which further cools the atmospheric column, producing stronger downdrafts of air mass and dissipation of clouds. In turn, clouds reduction caused an increase in solar radiation, countering the decrease in surface temperature."
"56245933700;6701873414;","Observations of transient linear oraganization and nonlinear scale interactions in lake-effect clouds. Part I: Transient linear organization",2005,"10.1175/MWR-2879.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17044400131&doi=10.1175%2fMWR-2879.1&partnerID=40&md5=246a3cc22e87d1376b1d1d645b76bbc7","The cold-air outbreak of 13-14 January 1998 during the Lake-Induced Convection Experiment was characterized by large positive buoyancy flux and moderate wind shear. Although theory predicts only cellular organization in these conditions, transient linear organization was observed. Time series of vertical velocity obtained with the Pennsylvania State University 94-GHz vertically pointing cloud radar, which is sensitive to cloud droplets and ice crystals, were used to document the changes in organization that occurred during this wintertime lake-effect event. The cloud radar was deployed on the downwind shore of southern Lake Michigan and measured high-temporal-resolution vertical velocity data at several in-cloud heights. The duration of the event was 18 h, encompassing three cycles of linear organization switching to cellular organization. In Part I of this two-part series the authors document the transient nature of the linearly organized convection and evaluate the role of atmospheric conditions in the mode switching between linear and cellular organization. Within the limits of the available measurements, no correlation was found with mean or low-level shear, surface fluxes, or stability parameters. The mode switching in this case does not appear to be controlled by the atmospheric indicators typically associated with linearly organized convection, suggesting that other factors must have played an important role. © 2005 American Meteorological Society."
"7101658117;57218598936;7004461962;55837993200;7102446182;6603175750;6603445264;7202970215;55993750800;7003912723;23492749600;7101619974;6701603958;7003406400;","Assimilation and modeling of the atmospheric hydrological cycle in the ECMWF forecasting system",2005,"10.1175/BAMS-86-3-387","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20244378820&doi=10.1175%2fBAMS-86-3-387&partnerID=40&md5=18ec4dbc042ae886430c20fa2a03f60a","Several new types of satellite instrument will provide improved measurements of Earth's hydrological cycle and the humidity of the atmosphere. In an effort to make the best possible use of these data, the modeling and assimilation of humidity, clouds, and precipitation are currently the subjects of a comprehensive research program at the European Centre for Medium-Range Weather Forecasts (ECMWF). Impacts on weather prediction and climate reanalysis can be expected. The preparations for cloud and rain assimilation within ECMWF's four-dimensional variational data assimilation system include the development of linearized moist physics, the development of fast radiative transfer codes for cloudy and precipitating conditions, and a reformulation of the humidity analysis scheme. Results of model validat ions against in situ moisture data are presented, indicating generally good agreement - often to within the absolute calibration accuracy of the measurements. Evidence is also presented of shortcomings in ECMWF's humidity analysis, from the operational data assimilation and forecasting system in 2002, and from the recently completed ERA-40 reanalysis project. Examples are shown of biases in the data and in the model that lead to biased humidity analyses. Although these biases are relatively small, they contribute to an overprediction of tropical precipitation and to an overly intense Hadley circulation at the start of the forecast, with rapid adjustments taking place during the first 6-12 h. It is shown that with an improved humidity analysis this long-standing ""spindown"" problem can be reduced. © 2005 American Meteorological Society."
"7403401100;6701378450;","A continuous-flow streamwise thermal-gradient CCN chamber for atmospheric measurements",2005,"10.1080/027868290913988","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18544376508&doi=10.1080%2f027868290913988&partnerID=40&md5=ff0fdcd96eabbd5d224a3583f348b183","We have addressed the need for improved measurements of cloud condensation nuclei (CCN) by developing a continuous-flow instrument that provides in situ measurements of CCN. The design presented in this article can operate between 0.1 and 3% supersaturation, at sampling rates sufficient for airborne operation. The design constitutes a cylindrical continuous-flow thermal-gradient diffusion chamber employing a novel technique of generating a supersaturation: by establishing a constant streamwise temperature gradient so that the difference in water vapor and thermal diffusivity yield a quasi-uniform centerline supersaturation. Our design maximizes the growth rate of activated droplets, thereby enhancing the performance of the instrument. The temperature gradient and the flow through the column control the supersaturation and may be modified to retrieve CCN spectra. The principle of the CCN instrument was validated in controlled laboratory experiments at different operating conditions using a monodisperse aerosols with known composition and size. These experiments yield sharp activation curves, even for those kinetically limited particles that have not exceeded their critical diameter. The performance of the CCN instrument was also assessed using polydisperse laboratory-generated aerosol of known composition and size distributions similar to ambient particulate matter. In all tests, the measured CCN concentrations compared well with predicted values and highlight the instrument's ability to measure CCN at various size distributions. The full potential of the new design has yet to be explored; however, model simulations suggest that direct measurements in the climatically important range of supersaturations of less than 0.1% (certainly down to 0.07%) are possible. The new instrument clearly offers a unique level of design simplicity, robustness, and flexilibity (temperature control, large range of supersaturations without flow reversal, and multiple configurations for same super-saturation) necessary for atmospheric studies."
"7402311929;7403373333;55740664200;7102576657;7006618862;6602287391;7202541817;8333585400;57213790366;8701382600;13608069100;8333585800;7003426743;6506195160;7201487195;55313019700;8333586400;6506451470;","The doe water cycle pilot study",2005,"10.1175/BAMS-86-3-359","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20244373167&doi=10.1175%2fBAMS-86-3-359&partnerID=40&md5=3fcd8a420e321156036798da5416841b","A Department of Energy (DOE) multilaboratory Water Cycle Pilot Study (WCPS) investigated components of the local water budget at the Walnut River watershed in Kansas to study the relative importance of various processes and to determine the feasibility of observational water budget closure. An extensive database of local meteorological time series and land surface characteristics was compiled. Numerical simulations of water budget components were generated and, to the extent possible, validated for three nested domains within the Southern Great Plains - the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Cloud Atmospheric Radiation Testbed (CART), the Walnut River watershed (WRW), and the Whitewater watershed (WW), in Kansas. A 2-month intensiv e observation period (IOP) was conducted to gather extensive observations relevant to specific details of the water budget, including finescale precipitation, streamflow, and soil moisture measurements that were not made routinely by other programs. Event and seasonal water isotope (d18O, dD) sampling in rainwater, streams, soils, lakes, and wells provided a means of tracing sources and sinks within and external to the WW, WRW, and the ARM CART domains. The WCPS measured changes in the leaf area index for several vegetation types, deep groundwater variations at two wells, and meteorological variables at a number of sites in the WRW. Additional activities of the WCPS include code development toward a regional climate model that includes water isotope processes, soil moisture transect measurements, and water-level measurements in groundwater wells. © 2005 American Meteorological Society."
"7101703632;7005803643;","On the temperature correlation of δ18O in modern precipitation",2005,"10.1016/j.epsl.2004.12.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844312068&doi=10.1016%2fj.epsl.2004.12.004&partnerID=40&md5=0372e5cc54df3681b623371697abffcb","Reevaluation of modern precipitation, temperature, and isotope data permits reconciliation of previous disparate values for the correlation between δ18O of modern precipitation and surface temperature. Past analysis has used the mean surface temperature over the time interval of sample collection (e.g., mean weekly, monthly, or annual temperature) to calculate temperature coefficients, and different approaches at mid-latitudes yield different temperature coefficients (Δδ18O/ΔT): spatial correlations among geographically distinct sites yield ∼0.55‰/K; seasonal variations at single sites yield 0.2-0.4‰/K; and 12 month running averages yield 0.5-1‰/K. However, there are systematic differences in temperature during precipitation events vs. time-averaged surface temperature means. Correction for this bias using hourly weather and monthly isotope data from U.S. sites yields a single value of ∼0.55‰/K for all three approaches. Revised temperature coefficients based on surface observations are also commensurate with coefficients obtained using cloud base temperatures and with theoretical distillation models (0.5-0.7‰/K). These coefficients provide a consistent basis for validation of general circulation models that incorporate stable isotopes of precipitation, and for comparison to independent estimators of the isotopic response to climate change. © 2004 Elsevier B.V. All rights reserved."
"7407663749;8204540500;6602995068;","Time series analysis of regional climate model performance",2005,"10.1029/2004JD005046","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17944377798&doi=10.1029%2f2004JD005046&partnerID=40&md5=02280d31e0c8b3fff245c7540002f88e","Four regional climate models (RegCM2, MM5/BATS, MM5/SHEELS, and MM5/OSU) were intercompared on a fairly small domain covering a relatively homogenous area in Kansas, United States, including the First International Satellite Land Surface Climatology Project (SLSCP) Field Experiment (FIFE) site. The models were integrated for a 2-year period covering 1987 and 1988. The model results are evaluated against data collected during this time period at the Konza Prairie Long-Term Ecological Research (LTER) site as well as over the summer observation periods of FIFE. The models all captured the proper qualitative behavior of the interannual variability, though the magnitudes varied considerably between models. They also found it particularly difficult to reproduce observed changes in the variance of surface variables. No model performed consistently better, with each model displaying particular strengths and weaknesses of its own. RegCM2 could be improved by including an ice phase in the cloud microphysics parameterization. MM5/BATS and MM5/SHEELS need revision of the formulation of stability dependence of the surface drag coefficients, including the coupling to the wind field, as well as using a total soil depth more representative of the area. MM5/OSU simulates too much. resistance to evapotranspiration and fails to close the energy budget. All of the models overestimate runoff and evapotranspiration during winter, creating a dry anomaly which persists throughout the following summer. Development and verification of parameterizations involved in coupling the land surface and atmospheric components of these models together is at least as important as the development and verification of each component individually. Copyright 2005 by the American Geophysical Union."
"56249704400;7404334532;","Distant origins of Arctic black carbon: A Goddard Institute for Space Studies ModelE experiment",2005,"10.1029/2004JD005296","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17944371348&doi=10.1029%2f2004JD005296&partnerID=40&md5=83226527921a4fb03c8516d81224ec18","Black carbon (BC) particles, derived from incomplete combustion of fossil fuels and biomass, may have a severe impact on the sensitive Arctic climate, possibly altering the temperature profile, cloud temperature and amount, the seasonal cycle, and the tropopause level and accelerating polar ice melting. We use the Goddard Institute for Space Studies general circulation model to investigate the origins of Arctic BC by isolating various source regions and types. The model suggests that the predominant sources of Arctic soot today are from south Asia (industrial and biofuel emissions) and from biomass burning. These are the primary global s.ources of BC (approximately 20% and 55%, respectively, of the global emissions), and BC aerosols in these regions are readily lofted to high altitudes where they may be transported poleward. According to the model the Arctic BC optical thickness is mostly from south Asia (30%) and from biomass (28%) (with Slightly more than half of biomass coming from north of 40°N); North America, Russia, and Europe each contribute 10-15%. Russia, Europe, and south Asia each contribute about 20-25% of BC to the low-altitude springtime ""Arctic haze."" In the Arctic upper troposphere/lower stratosphere during the springtime, south Asia (30-50%) and low-latitude biomass (20-30%) are dominant, with a significant aircraft contribution (10-20%). Industrial S emissions are estimated to be weighted relatively more toward Russia and less toward south Asia (compared with BC). As a result, Russia contributes the most to Arctic sulfate optical thickness (24%); however, the south Asian contribution is also substantial (17%). Uncertainties derive from source estimates, model vertical mixing, and aerosol removal processes. Nevertheless, our results suggest that distant sources contribute more to Arctic pollution than is generally assumed. Copyright 2005 by the American Geophysical Union."
"57188534998;7006329853;15828363300;7005113064;13806362800;","Passing through a giant molecular cloud: ""Snowball"" glaciations produced by interstellar dust",2005,"10.1029/2004GL021890","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17744384269&doi=10.1029%2f2004GL021890&partnerID=40&md5=12662562ae8f7b136ba67377855f59a8","In its motion through the Milky Way galaxy, the solar system encounters an average -density (≥330 H atoms cm-3) giant molecular cloud (GMC) approximately every 108 years, a dense (∼2 × 103 H atoms cm-3) GMC every ∼109 years and will inevitably encounter them in the future [Talbot and Newman, 1977]. However, there have been no studies linking such events with severe (snowball) glaciations in Earth history. Here we show that dramatic climate change can be caused by interstellar dust accumulating in Earth's atmosphere during the solar system's immersion into a dense (∼2 × 103 H atoms cm-3) GMC. The stratospheric dust layer from such interstellar particles could provide enough radiative forcing to trigger the runaway ice-albedo feedback that results in global snowball glaciations. We also demonstrate that more frequent collisions with less dense GMCs could cause moderate ice ages. Copyright 2005 by the American Geophysical Union."
"7102995797;7004076402;","Computer-based identification and tracking of Antarctic icebergs in SAR images",2005,"10.1016/j.rse.2004.10.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-12344276985&doi=10.1016%2fj.rse.2004.10.002&partnerID=40&md5=6272494f4cff0aad980546045d06053d","Icebergs play an important role in climate through the transfer of fresh water and heat between ice sheets and the oceans. Synthetic aperture radar (SAR) images offer a robust way of observing icebergs in the often dark and cloud-covered polar areas. A computer-based technique is proposed to identify icebergs at higher resolution than in the past, allowing the shape of small to medium icebergs to be retained and used for tracking between images acquired at different times. The identification consists of (i) automatic segmentation, followed by (ii) classification of these objects as icebergs or nonicebergs. The classification stage requires user intervention as the icebergs are not always a separable class from other objects, most notably sea ice. The icebergs are then matched between images using their size and shape similarities, and their position tracked. The system performance was assessed by applying the technique to three wintertime ERS-1 PRI images, around Kapp Norvegia (10°W), on the Eastern Weddell Sea coast. The results show both the identification and the tracking to be effective. © 2004 Elsevier Inc. All rights reserved."
"7005110878;7005265210;7004651463;","Sources of variability of evapotranspiration in California",2005,"10.1175/JHM-398.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14944368621&doi=10.1175%2fJHM-398.1&partnerID=40&md5=5d5f2620cf8b6aa66ad6f200a8d92fdd","The variability (1990-2002) of potential evapotranspiration estimates (ETo) and related meteorological variables from a set of stations from the California Irrigation Management System (CIMIS) is studied. Data from the National Climatic Data Center (NCDC) and from the Department of Energy from 1950 to 2001 were used to validate the results. The objective is to determine the characteristics of climatological ETo and to identify factors controlling its variability (including associated atmospheric circulations). Daily ETo anomalies are strongly correlated with net radiation (Rn) anomalies, relative humidity (RH), and cloud cover, and less with average daily temperature (Tavg). The highest intraseasonal variability of ETo daily anomalies occurs during the spring, mainly caused by anomalies below the high ETo seasonal values during cloudy days. A characteristic circulation pattern is associated with anomalies of ETo and its driving meteorological inputs, Rn, RH, and Tavg, at daily to seasonal time scales. This circulation pattern is dominated by 700-hPa geopotential height (Z700) anomalies over a region off the west coast of North America, approximately between 32° and 44° latitude, referred to as the California Pressure Anomaly (CPA). High cloudiness and lower than normal ETo are associated with the lowheight (pressure) phase of the CPA pattern. Higher than normal ETo anomalies are associated with clear skies maintained through anomalously high Z700 anomalies offshore of the North American coast. Spring CPA, cloudiness, maximum temperature (Tmax), pan evaporation (Epan), and ETo conditions have not trended significantly or consistently during the second half of the twentieth century in California. Because it is not known how cloud cover and humidity will respond to climate change, the response of ETo in California to increased greenhouse-gas concentrations is essentially unknown; however, to retain the levels of ETo in the current climate, a decline of Rn by about 6% would be required to compensate for a warming of +3°C. © 2005 American Meteorological Society."
"8247122100;7004479957;7007160862;7203085045;7004484563;","EPIC 95°W observations of the eastern Pacific atmospheric boundary layer from the cold tongue to the ITCZ",2005,"10.1175/JAS-3381.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14744295371&doi=10.1175%2fJAS-3381.1&partnerID=40&md5=69404d53ef07428df2d03280289d55cf","The atmospheric boundary layer (ABL) along 95°W in the eastern equatorial Pacific during boreal autumn is described using data from the East Pacific Investigation of Climate (EPIC) 2001, with an emphasis on the evolution of the thermodynamic ABL properties from the cold tongue to the cold-advection region north of the sea surface temperature (SST) front. Surface sensible and latent heat fluxes and wind stresses between 1°S and 12°N are calculated from data from eight NCAR C-130 research aircraft flights and from Tropical Atmosphere Ocean (TAO) buoys. Reduced surface wind speed and a 10 m s-1 jet at a height of 500 m are found over the equatorial cold tongue, demonstrating the dependence of the surface wind speed on surface stability. The ABL exhibits a maximum in cloud cover on the north (downwind) side of the warm SST front, at 1°-3°N. Turbulent mixing driven by both surface buoyancy flux and radiative cooling at the cloud tops plays a significant role in maintaining the depth and structure of the ABL. The ABL heat budget between the equator and 3°N is balanced by comparable contributions from advective cooling, radiative cooling, surface warming, and entrainment warming. Entrainment drying is a weak contributor to the moisture budget, relative to dry advection and surface evaporation. Both the heat and moisture budgets are consistent with a rapid entramment rate, 12 ± 2 mm s-1, deduced from the observed rise of the inversion with latitude between 0° and 4°N. © 2005 American Meteorological Society."
"57218348877;7202672095;7004086472;8563095000;35564888800;","Spatial and temporal variations of precipitation in and around Bangladesh",2005,"10.2151/jmsj.83.21","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17744375570&doi=10.2151%2fjmsj.83.21&partnerID=40&md5=5bd04d32ce39e4a632df72c6e2a78cb8","Radar data from the Bangladesh Meteorological Department (BMD) are employed as a preliminary analysis. This is a first research work to investigate the spatial and temporal distribution of rainfall over the country for 135 consecutive days, from 16 April to 30 August 2000. Radar data are sampled in 10 km grid boxes to obtain daily rainfall over the country. Rain gauge data at 33 locations are utilized to check the radar results. The distributions of rainfall obtained by both the radar and the rain gauges are similar in pattern, but the time of the maximum rainfall determined by the radar is a few hours earlier than that determined by the rain gauges. The distribution of rainfall over the whole radar domain suggests that 21 to 09 local standard time (LST) is the most likely time for rainfall to occur in Bangladesh, while 06 LST is the most likely time for maximum rainfall to occur over the entire country. It is mentioned that no data are available between 03-06 LST. The occurrence of 21 to 09 LST rainfall is possibly linked to the local effects such as complex terrain and sea and land breeze circulations. The morning maximum rainfall at 06 LST in Bangladesh is different from that of the Indian subcontinent or of the mountain area where, generally, maximum rainfall occurs in the afternoon. The northern border of Bangladesh, close to the Shillong hill of India, is the region with the highest rainfall, while the second highest volume of rainfall occurs on the eastern border. In order to observe the characteristics of large-scale cloud activity, analyses of the Japanese GMS-5 hourly infrared data, within a larger domain of 80-100°E and 1030°N were conducted. The cloud activities in and around Bangladesh were obtained in 1° by 1° grid boxes. The northwestern part of Bangladesh was largely affected by pre-monsoon clouds, while the whole country was affected by the peak monsoon activities. © 2005, Meteorological Society of Japan."
"35337273500;7202042059;7401683250;14048744800;","Climatological distribution of lightning density observed by satellites in China and its circumjacent regions",2005,"10.1360/03yd0204","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746375985&doi=10.1360%2f03yd0204&partnerID=40&md5=2f87adcc33733c9acf8239b978c8f47c","The 0.5° × 0.5° grid resolution distribution of lightning density in China and its circumjacent regions have been analyzed by using the satellite-borne OTD (Apr 1995-Mar 2000) and LIS (Dec 1997-Mar 2003) databases. It is shown that: (i) Firstly, the variability of the lightning density (LD) is particularly pronounced over the different subareas, 9 times greater over the south than the north side of Himalayas Mountains, 2.5 times greater over the eastern than the western area of China. While the maximum and minimum LD are respectively 31.4fl/km2/a (in Guangzhou region) and less than 0.2fl/km2/a (in the desert of western China). Secondly, the LD of China's continent regularly varies with latitude and distance off coast, which is consistent with annual mean precipitation in varying trend. In conclusion, the Qinghai-Tibet Plateau, the China's three-step staircase topography and the latitude are three important factors affecting macro-scale characteristics of the LD distribution, (ii) The regional differences in LD distribution are closely related to the mesoscale orographie forcing. In the eastern humid regions of China, the high LD belts often appear along the mesoscale mountains (with south-north or northeast-southwest direction, 500-1500 m ASL) and hills, while the low LD belts often appear on the plain and basin (valley) between the mountains. But in the western cold and arid regions of China, the relatively high LD belts mostly appear on the Qinghai Lake area of the southern side of Qilian Mountain, Yili River valley, the basin between Tanggula Mountains and Nyainqêntanglha. On the coastal land, the high LD centers appear in regions where mountain and hill and large cities are located. This seems to be related to the interaction between the sea-land breeze and mountain-valley wind or city heat island effect, (iii) The China Sea is one of the relatively high LD zones on global oceans. It is very interesting that a high LD belt is located along the Kuroshio area. It is a new fact that the high temperature and high salinity characteristics of Kuroshio have obvious effect on the local deep convective activity. In addition, the intracloud/cloud-to-ground lightning ratio is close to 3.0 in Anhui Province. Copyright by Science in China Press 2005."
"55624487819;36092832100;6507173926;7402398883;","Precipitation, temperature and runoff analysis from 1950 to 2002 in the Yangtze basin, China [Analyse des précipitations, températures et débits de 1950 à 2002 dans le bassin du Yangtze, en Chine]",2005,"10.1623/hysj.50.1.65.56338","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13244275307&doi=10.1623%2fhysj.50.1.65.56338&partnerID=40&md5=76222a286a98b16fd043e5a5ed172dff","Monthly precipitation and temperature trends of 51 stations in the Yangtze basin from 1950-2002 were analysed and interpolated. The Mann-Kendall trend test was applied to examine the monthly precipitation and temperature data. Significant positive and negative trends at the 90, 95 and 99% significance levels were detected. The monthly mean temperature, precipitation, summer precipitation and monthly mean runoff at Yichang, Hankou and Datong stations were analysed. The results indicate that spatial distribution of precipitation and temperature trends is different. The middle and lower Yangtze basin is dominated by upward precipitation trend but by somewhat downward temperature trend; while downward precipitation trend and upward temperature trend occur in the upper Yangtze basin. This is because increasing precipitation leads to increasing cloud coverage and, hence, results in decreasing ground surface temperature. Average monthly precipitation and temperature analysis for the upper, middle and lower Yangtze basin, respectively, further corroborate this viewpoint. Analysis of precipitation trend for these three regions and of runoff trends for the Yichang, Hankou and Datong stations indicated that runoff trends respond well to the precipitation trends. Historical flood trend analysis also shows that floods in the middle and lower Yangtze basin are in upward trend. The above findings indicate that the middle and lower Yangtze basin is likely to face more serious flood disasters. The research results help in further understanding the influence of climatic changes on floods in the Yangtze basin, providing scientific background for the flood control activities in large catchments in Asia. Copyright © 2005 IAHS Press."
"7202079615;10240710000;8979277400;35330367300;7404243086;","Simulation of climate response to aerosol direct and indirect effects with aerosol transport-radiation model",2005,"10.1029/2004JD005029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16444367564&doi=10.1029%2f2004JD005029&partnerID=40&md5=448d2f38be65ab70aaff2774e93a85a7","With a global aerosol transport-radiation model coupled to a general circulation model, changes in the meteorological parameters of clouds, precipitation, and temperature caused by the direct and indirect effects of aerosols are simulated, and its radiative forcing are calculated. A microphysical parameterization diagnosing the cloud droplet number concentration based on the Köhler theory is introduced into the model, which depends not only on the aerosol particle number concentration but also on the updraft velocity, size distributions, and chemical properties of each aerosol species and saturation condition of the water vapor. The simulated cloud droplet effective radius, cloud radiative forcing, and precipitation rate, which relate to the aerosol indirect effect, are in reasonable agreement with satellite observations. The model results indicate that a decrease in the cloud droplet effective radius by anthropogenic aerosols occurs globally, while changes in the cloud water and precipitation are strongly affected by a variation of the dynamical hydrological cycle with a temperature change by the aerosol direct and first indirect effects rather than the second indirect effect itself. However, the cloud water can increase and the precipitation can simultaneously decrease in regions where a large amount of anthropogenic aerosols and cloud water exist, which is a strong signal of the second indirect effect. The global mean radiative forcings of the direct and indirect effects at the tropopause by anthropogenic aerosols are calculated to be -0.1 and -0.9 W m -2, respectively. It is suggested that aerosol particles approximately reduce 40% of the increase in the surface air temperature by anthropogenic greenhouse gases on the global mean. Copyright 2005 by the American Geophysical Union."
"7006131953;57203977166;","A k-distribution technique for radiative transfer simulation in inhomogeneous atmosphere: 2. FKDM, fast k-distribution model for the shortwave",2005,"10.1029/2004JD005163","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17044433820&doi=10.1029%2f2004JD005163&partnerID=40&md5=f5633d20fba3db8c8394c5e2d641a19f","A new technique for developing k-distributions applied to longwave radiation parameterization has been presented in a preceding paper. Now we discuss an extension of this technique to the shortwave spectral range. A fast k-distribution model (FKDM) for gaseous absorption calculations suitable for use in weather and climate prediction is described. FKDM has been created using 15 k-distribution terms only, less than in other comparable codes. The molecular species represented in the model are H2O, CO2, O3, and O 2. In k-distribution terms, characterized by strong absorption, representative absorption cross section is treated as a function of absorber amount along the direct solar radiation path, thus allowing improved fitting of solar fluxes and heating rates in upper troposphere and stratosphere. This technique has been applied to derive effective single-scattering properties of clouds in each term for a more accurate treatment of cloud optical properties by taking into account correlation between water vapor and liquid water or ice absorption. It is shown that disregarding the above correlation in radiation models can essentially distort simulated fluxes and heating rates. FKDM has been developed and validated using a fast line-by-line model (FLBLM). Both FKDM and FLBLM used a Monte-Carlo code. Validations have covered the tropical, midlatitude summer, midlatitude winter, subarctic summer, subarctic winter, and U.S. standard atmospheres, four atmospheres from the Spectral Radiance Experiment campaign, and a case of an observed tropical atmosphere. It is found that the FKDM heating rate accuracy for clear-sky conditions is as follows: ∼0.1 and ∼0.2 K d -1 in the troposphere for standard and real atmospheres, respectively, and ∼0.5 K d-1 in all the cases at altitudes below 70 km. Downward flux errors are below 1%, upward flux errors are below 2% (usually ∼1.5 W m-2), and total atmospheric absorption errors are below 3% (usually 1.5-3 W m -2) in every case. The Intercomparison of Radiation Codes in Climate Models (ICRCCM) cloud models have also been used for the validations. It has been demonstrated that the usage of the technique to derive effective cloud optical properties halves maximal errors in calculated radiation fluxes absorbed by cloud. Copyright 2005 by the American Geophysical Union."
"6506913052;6602863002;8329497200;","UV radiation in the Netherlands: Assessing long-term variability and trends in relation to ozone and clouds",2005,"10.1029/2004JD004824","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17044406613&doi=10.1029%2f2004JD004824&partnerID=40&md5=d77640ad48a2f5dd1b8239508e335262","The variability and long-term changes in the ultraviolet (UV) climate in the Netherlands have been studied in relation to ozone and clouds, by analyzing modeled and measured values for daily, monthly, and yearly integrated erythernally weighted UV doses. At Bilthoven, Netherlands (longitude 5.19°E, latitude 52.12°N), UV irradiance measurements for the 1994-2003 period yielded a mean annual dose of 447 ± 29 kJ/m2 and a mean daily dose of 2.5 ± 0.5 kJ/m 2 for June and July. On average, the maximum UV index exceeded 6.5 (i.e., 0.1625 W/m2 erythemally weighted) on 10 days per year (21 days in 2003). The mean value of measured-to-modeled ratios of erythernal UV irradiances was 1.00 with a standard deviation of 0.06 for days when the measured global solar radiation agrees within 5% with the cloudless sky value. Three previously introduced approaches to model cloud effects on UV doses were shown to have limitations when applied for low Sun and/or optically thick clouds, while a new approach provided the most consistent results with an average ratio of the measured-to-modeled daily doses of 1.02 and a standard deviation of 0.09, for all seasons and weather conditions for the period 1994-2002. Further analysis also revealed a wavelength dependency of the correlation between global solar radiation and UV radiation. Clouds, on average, reduced the daily dose of erythernal UV to 68% of the clear-sky value, whereas for global solar radiation this was 57%. The modeled annual erythernal UV dose was 622 kJ/m2 (402 kJ/ m 2 ) averaged over the years 1979-1982, while the years 2000-2003 yield 662 kJ/m2 (448 kJ/m2) for cloudless (cloudy) conditions. In the past 25 years the highest annual doses were received in 1995 (485 kJ/m2) and 2003 (488 kJ/m 2): in 1995 as a result of extremely low ozone values and moderate cloud reduction and in 2003 as a result of extremely low cloud reduction combined with moderately low ozone values. As an indication of the changes over time, a linear regression is performed showing that the annual UV dose received at the ground for all weather conditions increased with 5.5 ± 2% per decade for erythemal UV over the 1979-2003 period. Copyright 2005 by the American Geophysical Union."
"15835359300;36124109400;","Erythemal UV at Davos (Switzerland), 1926-2003, estimated using total ozone, sunshine duration, and snow depth",2005,"10.1029/2004JD005231","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17044362648&doi=10.1029%2f2004JD005231&partnerID=40&md5=a9054297aeb050b71867b61954650152","A method previously developed for reconstructing daily erythemal UV doses at Sodankylä, northern Finland, was adjusted to the local conditions at Davos, Switzerland, and used for estimating the erythemal UV doses there over the period 1926-2003. The method uses total ozone, sunshine duration, and snow depth as input, and is based on the empirical relationship between relative sunshine duration and relative UV doses. In order to examine how the method behaves in different environments, the relationships found for Davos and Sodankylä were compared. This revealed that the surface albedo and the cloud climate have a comparable influence on the relationship found. Although the method is fairly simple, it accounts for the most important factors affecting the amount of UV radiation reaching the Earth's surface. A comparison between estimated UV doses and the corresponding observations with a broadband biometer at Davos demonstrated the good performance of the method. The correlation coefficient for daily values varies between 0.95 and 0.98 depending on time of year, and the corresponding root mean square error is typically of the order of 20%. The monthly mean values show considerably less scatter around the regression line with a root mean square error of 4%. The time series of estimated UV shows that the UV level at Davos has varied considerably throughout the period of this study, with high values in the middle of the 1940s, in the early 1960s, and in the 1990s. Variations in the estimated UV doses prior to 1980, e.g., a steady decrease from the early 1960s to the late 1970s, were found to be caused primarily by changes in sunshine duration. Since 1980, on the other hand, there has been a distinct increase in the UV level caused mainly by the diminution of total ozone. This increase is most clearly seen during winter and spring, while the decrease from the early 1960s to the late 1970s is most pronounced during summer. Copyright 2005 by the American Geophysical Union."
"11139484600;16161569000;23485501700;7103333752;7202281109;7004462227;","Hydrophilic properties of aged soot",2005,"10.1029/2004GL021496","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16344363848&doi=10.1029%2f2004GL021496&partnerID=40&md5=8ef2125df217193c2bb22257aee979c8","The global presence of soot has significant effects on regional and global climate, as well as human health. Influence of soot on radiation budget, rain formation and heterogeneous chemistry, and its residence time in the atmosphere are largely dependent on its ability to interact with water. While freshly emitted soot is extremely hydrophobic, oxidation during aging causes soot to become more hydrophilic. Laboratory studies demonstrate that aged soot attracts and retains water, and can be efficiently removed from the troposphere by entrapment in existing liquid cloud droplets or by activation as cloud condensation nuclei. Copyright 2005 by the American Geophysical Union."
"7005137442;","Climate dynamics of a hard snowball Earth",2005,"10.1029/2004JD005162","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17044371501&doi=10.1029%2f2004JD005162&partnerID=40&md5=a12f1c89319d457db2bcef18c5d63a5a","The problem of deglaciating a globally ice-covered (""hard snowball"") Earth is examined using a series of general circulation model simulations. The aim is to determine the amount of CO2 that must be accumulated in the atmosphere in order to trigger deglaciation. Prior treatments of this problem have been limited to energy balance models, which are incapable of treating certain crucial physical processes that turn out to strongly affect the conditions under which deglaciation can occur. CO2 concentrations up to .2 bars are considered in the general circulation model simulations, and even at such high CO2 content the model radiation code is found to perform well in comparison with codes explicitly designed for high CO2. In contrast to prevailing expectations, the hard snowball Earth is found to be nearly 30 K short of deglaciation, even at .2 bars. The very cold climates arise from a combination of the extreme seasonal and diurnal cycle, lapse rate effects, snow cover, and weak cloud effects. Several aspects of the atmospheric dynamics are examined in detail. The simulations indicate that the standard scenario, wherein snowball termination occurs after a few tenths of a bar of CO 2 has built up following cessation of weathering, is problematic. However, the climate was found to be sensitive to details of a number of parameterized physical processes, notably clouds and heat transfer through the stable boundary layer. It is not out of the question that other parameterization suites might permit deglaciation. The results should not be construed as meaning that the hard snowball state could not have occurred, but only that deglaciation requires the operation of as-yet undiscovered processes that would enhance the climate sensitivity. A brief survey of some of the possibilities is provided. Copyright 2005 by the American Geophysical Union."
"12039415500;7501757094;","Cloud parameterizations in SUNYA regional climate model for the East Asia summer monsoon simulations",2005,"10.3319/TAO.2005.16.5.959(RCS)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31444446804&doi=10.3319%2fTAO.2005.16.5.959%28RCS%29&partnerID=40&md5=083c85ca7c15025b33e2da6d13dd3a10","East Asia summer monsoon (EASM) simulations are conducted to evaluate three schemes which determine cloud properties used in the radiation calculation of the State University of New York at Albany (SUNYA) regional climate model (RCM). Scheme-I uses diagnostic cloud cover and cloud water while Scheme-II uses prognostic cloud water along with overcast sky; both schemes are commonly employed in RCMs. In Scheme-III, cloud cover is determined by diagnostic formula, but the cloud water is calculated by the weighted means of its diagnosed and prognosed values. Therefore, Scheme-III considers the subgrid-scale clouds as Scheme-I and maintains consistent cloud properties in radiation calculation and microphysical processes as Scheme-II. Cloud radiative forcing (CRF) which provides a quantification of the cloud-radiation-climate interaction is adopted to compare the three schemes in simulating the 1991 EASM, characterized by large amounts of cloud and persistent rainfall over Yangtze-Huai River valley. With these three cloud schemes, the SUNYA RCM is capable of simulating the intra-seasonal variations of observed cloud cover and longwave CRF. The transition of shortwave CRF is not properly simulated due to the constantly presented low-level clouds. Mostly the magnitude of CRF is over-estimated by 13-22 W m-2 for shortwave CRF and by 12-16 W m-2 for longwave CRF. It is also found that the surface temperature biases are highly correlated (with correlation coefficient greater than 0.8) to the shortwave CRF biases. Therefore, Scheme-III resulting in less low-level cloud water and the least shortwave CRF biases simulates surface temperatures in better agreement with observations. Analyses of surface energy balance components indicate that the CRF changes dominate the surface temperature responses and the consequent surface latent heat and sensible heat flux feedbacks significantly offset them. Finally, comparisons of the diurnal variations of simulated cloud water among the three schemes show that Scheme-III provides consistency between cloud microphysics and radiation."
"55893487700;6603315547;7003535176;","A note on how to avoid contrail cirrus",2005,"10.1016/j.trd.2005.04.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22544444223&doi=10.1016%2fj.trd.2005.04.012&partnerID=40&md5=41fc299e5264ac4f8acd62df849b0f39","Aircraft induced cirrus clouds have a major effect on climate. Here we use operational radiosonde data with high vertical resolution to estimate the effect of a small change in flight altitudes on the contrail and cirrus formation. It is shown that a substantial fraction of contrails and contrail induced cirrus can be avoided by relatively small changes in flight level, due to the shallowness of ice-super-saturation layers. © 2005 Elsevier Ltd. All rights reserved."
"57203348817;8287337100;36740296400;","Orographic precipitation and Oregon's climate transition",2005,"10.1175/JAS-3376.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13244299317&doi=10.1175%2fJAS-3376.1&partnerID=40&md5=d8ec011b2f08b9a0b1024a0deb187683","Oregon's sharp east-west climate transition was investigated using a linear model of orographic precipitation and four datasets: (a) interpolated annual rain gauge data, (b) satellite-derived precipitation proxies (vegetation and brightness temperature), (c) streamflow data for a small catchment, and (d) stable isotope analysis of water samples from streams. The success of the linear model against these datasets suggests that the main elements of the model (i.e., airflow dynamics, cloud time delays, condensed water advection, and leeside evaporation) are behaving reasonably, although the high Oregon terrain may push the linear theory beyond its range of applicability. A key parameter in the linear model is the cloud delay time (τ), encapsulating the action of orographic cloud processes. Each dataset was examined to see if it can constrain the τ values. The statewide precipitation patterns from rain gauge and satellite constrain the τ values only within a broad range from about 500 to 5000 s. A focus on the sharp gradient on the lee slopes of the Cascades suggests that τ values in the range of 1800-2400 s are preferred. The study of the small Alsea watershed constrains τ little, as it receives a mixture of upslope and spillover precipitation. Stable isotope ratios in stream water indicate an atmospheric drying ratio of about 43%, requiring an average cloud physics delay time greater than τ = 600 s. © 2005 American Meteorological Society."
"7404747615;","The semidirect aerosol effect: Comparison of a single-column model with large eddy simulation for marine stratocumulus",2005,"10.1175/JCLI-3233.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844292770&doi=10.1175%2fJCLI-3233.1&partnerID=40&md5=368ae7c0ced496ca4bcf1b424e47c163","Large eddy simulations (LES) show that the presence of black carbon aerosols in marine boundary layers leads to a marked reduction of stratocumulus liquid water path (LWP) by heating the cloud layer and suppressing convection in the boundary layer. The reduction of LWP leads to a positive radiative forcing known as the semidirect effect. In this study LES results are compared with results from the National Center for Atmospheric Research (NCAR) Single-Column Community Climate Model (SCCM). The SCCM represents clouds and boundary layer processes through simple parameterization schemes that are typical of general circulation models (GCMs) used for climate experiments. In a case study in which black carbon aerosols were introduced in a stratocumulus-capped boundary layer the SCCM gave a semidirect aerosol radiative forcing that was a factor of 5 smaller than the value obtained from the LES. The cloud response to absorbing aerosols was underestimated because of the way that cloud cover and cloud radiative properties were parameterized in the SCCM. Furthermore, the SCCM gave a poor representation of processes, such as entrainment and boundary layer decoupling, that are crucial to determining stratocumulus LWP. This study shows that GCMs may not include all the physical processes necessary to adequately capture the semidirect aerosol effect. Previous GCM estimates of the semidirect effect that have incorporated simple cloud parameterizations should, therefore, be treated with some caution. © 2005 American Meteorological Society."
"7006111925;6603723278;23978480100;6701926018;7102545802;56402486000;","Characterizing the urban heat island in current and future climates in New Jersey",2005,"10.1016/j.hazards.2004.12.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744490585&doi=10.1016%2fj.hazards.2004.12.001&partnerID=40&md5=5abf44114ef56d5d77b75fc9a255d230","Climate change caused by increased anthropogenic emissions of carbon dioxide (CO2) and other greenhouse gases is a long-term climate hazard with the potential to alter the intensity, temporal pattern, and spatial extent of the urban heat island (UHI) in metropolitan regions. Particular meteorological conditions—including high temperature, low cloud cover, and low average wind speed—tend to intensify the heat island effect. Analyses of existing archived climate data for the vicinities of Newark and Camden, New Jersey indicate urban to suburban/rural temperature differences over the previous half-century. Surface temperatures derived from a Landsat thermal image for each site were also analyzed for spatial patterns of heat islands. Potential interactions between the UHI effect and projected changes in temperature, wind speed, and cloud cover are then examined under a range of climate change scenarios, encompassing different greenhouse gas emissions trajectories. The scenarios include those utilized in the Metropolitan East Coast Regional Assessment of Climate Variability and Change and the A2 and B2 scenarios of the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES). The UHI effect was detected in Newark and Camden in both satellite surface-temperature and meteorological station airtemperature records. The average difference in urban—nonurban minimum temperatures was 3.0 °C for the Newark area and 1.5 °C for Camden. Extrapolation of current trends and the selected global climate models (GCMs) project that temperatures in the case study areas will continue to warm in the current century, as they have over the past half-century. An initial analysis of global climate scenarios shows that wind speed may decline, and that cloud cover may increase in the coming decades. These generally small countervailing tendencies suggest that urban—nonurban temperature differences may be maintained under climate change. Overall warmer conditions throughout the year may extend the spatial and temporal dimensions of the urban-suburban heat complex. The incidence of heat-related morbidity and mortality are likely to increase with interactions between the increased frequency and duration of heat waves and the UHI effect. Camden and Newark will likely be subjected to higher temperatures, and areas experiencing UHI-like conditions and temperature extremes will expand. Thus, urban heat island-related hazard potential is likely to increase in a warmer climate. © 2005 Taylor &amp; Francis Group, LLC."
"9132948500;7201504886;7006452341;","On the diurnal cycle and susceptibility to aerosol concentration in a stratocumulus-topped mixed layer",2005,"10.1256/qj.04.103","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27644441425&doi=10.1256%2fqj.04.103&partnerID=40&md5=df83e349dc29d99da1ead0716b29af82","Mixed-layer theory is used to study the diurnal cycle of the stratocumulus-topped boundary layer and its susceptibility to perturbations in atmospheric aerosol concentration. Our results show that the diurnal evolution of cloud thickness is sensitive to the entrainment efficiency. For high entrainment efficiencies, the cloud base tends to descend at a faster rate than the cloud top; this difference in descent rates leads to cloud thickening during the daytime, which is inconsistent with observations. For low entrainment efficiencies, variations in cloud-top height dominate in the cloud-thickness evolution, while cloud-base height remains almost constant; this behaviour is in better agreement with available data. We explain these effects through a consideration of the equilibrium state of cloud boundaries and their adjustment time-scales. Liquid-water path and cloud albedo are both sensitive to the entrainment efficiency; still, the susceptibility of cloud albedo to droplet number density dominates the entrainment effects. This result has significant implications for climate-sensitivity studies: it suggests that estimates of aerosol indirect effects from stratocumulus clouds will not be particularly sensitive to the way entrainment is represented in large-scale models. © Royal Meteorological Society, 2005."
"7003398947;6603081424;57206332144;7402215419;55499821700;57205867148;56771301000;57202531041;23476370700;7005626683;25941200000;7006204393;7006738324;7004315232;8608733900;56270311300;57207603330;6602356307;6602209040;6603330844;6603551919;7202899330;56198145500;6603904180;6603453147;8225489800;7007057711;","The 13RC: Bringing together the most advanced radiative transfer tools for cloudy atmospheres",2005,"10.1175/BAMS-86-9-1275","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844503446&doi=10.1175%2fBAMS-86-9-1275&partnerID=40&md5=2f241d6817222cdcc0fc6a9cf8154315","The interaction of clouds with solar and terrestrial radiation is one of the most important topics of climate research. In recent years it has been recognized that only a full three-dimensional (3D) treatment of this interaction can provide answers to many climate and remote sensing problems, leading to the worldwide development of numerous 3D radiative transfer (RT) codes. The international Intercomparison of 3D Radiation Codes (I3RC), described in this paper, sprung from the natural need to compare the performance of these 3D RT codes used in a variety of current scientific work in the atmospheric sciences. I3RC supports intercomparison and development of both exact and approximate 3D methods in its effort to 1) understand and document the errors/limits of 3D algorithms and their sources; 2) provide ""baseline"" cases for future code development for 3D radiation; 3) promote sharing and production of 3D radiative tools; 4) derive guidelines for 3D radiative tool selection; and 5) improve atmospheric science education in 3D RT. Results from the two completed phases of I3RC have been presented in two workshops and are expected to guide improvements in both remote sensing and radiative energy budget calculations in cloudy atmospheres. © 2005 American Meteorological Society."
"6603031730;6603742681;11339001000;55728284300;36842724800;7103259757;8212745300;11338901700;57199124158;7410340979;56528895600;56132929700;","Generating historical AVHRR 1 km baseline satellite data records over Canada suitable for climate change studies",2005,"10.5589/m05-024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30644475278&doi=10.5589%2fm05-024&partnerID=40&md5=3e9cc4d08183d2535677a31ce859b0d1","Satellite data are an important component of the global climate observing system (GCOS). To serve the purpose of climate change monitoring, these data should satisfy certain criteria in terms of the length of observations and the continuity and consistency between different missions and instruments. Despite the great potential and obvious advantages of satellite observations, such as frequent repeat cycles and global coverage, their use in climate studies is hindered by substantial difficulties arising from large data volumes, complicated processing, and significant computer resources required for archiving and analysis. Successful examples of satellite earth observation (EO) data in climate studies include, among others, analyses of the earth’s radiation budget (Earth Radiation Budget Experiment (ERBE), Scanner for Radiation Budget (ScaRaB), and Cloud and the Earth’s Radiant Energy System (CERES)), cloudiness (International Satellite Cloud Climatology Project (ISCCP)), vegetation research (Global Inventory Modeling and Mapping Studies (GIMMS)), and the National Oceanic and Atmospheric Administration – National Aeronautics and Space Administration (NOAA–NASA) Pathfinder Program. Despite several attempts, the great potential of the advanced very high resolution radiometer (AVHRR) 1 km satellite data for climate research remains substantially underutilized. To address this issue, the generation of a comprehensive satellite data archive of AVHRR data and products at 1 km spatial resolution over Canada for 1981–2004 (24 years) has been initiated, and a new system for processing at level 1B has been developed. This processing system was employed to generate baseline 1 day and 10 day year-round clear-sky composites for a 5700 km × 4800 km area of North America. This region is centred over Canada but also includes the northern United States, Alaska, Greenland, and surrounding ocean regions. The baseline products include top-of-atmosphere (TOA) visible and near-infrared reflectance, TOA band 4 and band 5 brightness temperature, a cloud – clear – shadow – snow and ice mask, and viewing geometry. Details of the data processing system are presented in the paper. An evaluation of the system characteristics and comparison with previous results demonstrate important improvements in the quality and efficiency of the data processing. The system can process data in a highly automated manner, both for snow-covered and snow-free scenes, and for daytime and nighttime orbits, with high georeferencing accuracy and good radiometric consistency for all sensors from AVHRR NOAA-6 to AVHRR NOAA-17. Other processing improvements include the implementation of advanced algorithms for clear sky – cloud – shadow – snow and ice scene identification, as well as atmospheric correction and compositing. At the time of writing, the assembled dataset is the most comprehensive AVHRR archive at 1 km spatial resolution over Canada that includes all available observations from AVHRR between 1981 and 2004. The archive and the processing system are valuable assets for studying different aspects of land, oceans, and atmosphere related to climate variability and climate change. © 2005 Government of Canada."
"55703823500;57202301596;7601492669;","Subseasonal variability of the southeast Pacific stratus cloud deck",2005,"10.1175/JCLI3250.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844292771&doi=10.1175%2fJCLI3250.1&partnerID=40&md5=80aac8fc0500c976acaabb72a6ebb63d","Subseasonal variability of the stratus/stratocumulus cloud deck over the subtropical southeast Pacific is studied using satellite and buoy observations as well as the NCEP-NCAR reanalysis. It is found that subseasonal variability in the stratus cloud deck is closely related to variations in surface wind velocity, water vapor, sea level pressure, and 500-hPa geopotential height. An increase in cloud liquid water (CLW) over the subtropical southeast Pacific is found to be associated with the development of an anomalous anticyclonic circulation to the south off the west coast of Chile. The enhanced southerly to southeasterly winds advect cold and dry air into the stratus region against the mean sea surface temperature (SST) gradient. This cold and dry advection, together with increased wind speed, intensifies surface latent and sensible heat fluxes and destabilizes the boundary layer. Anomalous offshore easterlies north of the anomalous anticyclone cause a low-level divergence. The associated subsidence warming, together with the cold advection in the surface layer, strengthens the temperature inversion, conducive to the development of stratus clouds. Buoy observations confirm this subseasonal cloud variability and its relationship with surface meteorological variables. A lead/lag composite analysis indicat es that circulation variables such as sea level pressure and surface wind lead cloud liquid water by 1-2 days while SST lags CLW by 1-2 days, suggesting that low-cloud variability is caused by atmospheric circulation changes rather than by the underlying ocean. The dynamic adjustment that leads to cloud fluctuations and possible orographic effects of the Andes are also discussed. © 2005 American Meteorological Society."
"7201504886;7004084412;6701850538;24722339600;56350405800;7101795549;7004479957;23019327900;","Pockets of open cells and drizzle in marine stratocumulus",2005,"10.1175/BAMS-86-1-51","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13244265239&doi=10.1175%2fBAMS-86-1-51&partnerID=40&md5=d16e5a768588a3ee3635fd25066d0ad0","Data from recent field studies in the northeast and southeast Pacific are used to investigate pockets of open cells (POCs) that are embedded in otherwise uniform stratocumulus. The cellular structure within a POC resembles broader regions of open cellular convection typically found further offshore. In both regions, cells are composed of precipitating cells walls and cell interiors with depleted cloud water and even clearing. POCs are long lived and embedded in broader regions of stratocumulus where average droplet sizes are relatively large. In contrast, stratiform, or unbroken, cloud formations tend to be accompanied by lees, or no, drizzle, suggesting that precipitation is necessary for the sustenance of the open cellular structure. Because, by definition, open cells are associated with a reduction in cloud cover these observations provide direct evidence of a connection between cloudiness and precipitation - A linchpin of hypotheses that posit a connection between changes in the atmospheric aerosol and climate. © 2005 American Meteorological Society."
"6507948271;7005112315;","Temperature dependence of tropical cirrus properties and radiative effects",2005,"10.1029/2004JD005426","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750433229&doi=10.1029%2f2004JD005426&partnerID=40&md5=4165d788efbe8b23ba09922564d80e96","The temperature dependencies of cirrus properties are studied using a dual polarization lidar and Mesosphere Stratosphere Troposphere (MST) radar at the tropical tation Gadanki (13.5°N, 79.2°E). Cirrus clouds are generally observed in the altitude region 10 to 18 km, with midcloud temperature in the range -85° to -40°C. The cloud temperature decreases with increase in cloud altitude as expected. The mean cloud thickness is generally in the range 0.7 to 1.7 km. For temperatures in the range -75° to -50°C the cloud thickness is ∼1.7 km and shows a tendency to decrease at lower temperatures. The linear depolarization ratio (LDR) within the cloud shows a small increase with decrease in temperature. The cloud extinction and optical depth increases with increase in temperature. The temperature dependence of cirrus extinction/optical depth has been parameterized using different analytical forms such as exponential, linear, and polynomial, which shows that a second-order polynomial function is well suited for describing the temperature dependence of extinction coefficient/optical depth of tropical cirrus. The climate sensitivity factor derived based on the empirical relations shows an increase with decrease in cloud optical depth. The present study, however, indicates that the cirrus becomes radiatively significant when its optical depth exceeds a threshold value of 0.03. Copyright 2005 by the American Geophysical Union."
"6507611604;7201549312;7406354082;7006568483;7003965195;7003292889;","Diurnal cycle in the North America Monsoon",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-14244260069&partnerID=40&md5=52f609d3516c813fe4423524a5c73654","A comprehensive diagnostic study of the temporal and spatial structure of North American Monsoon System (NAMS) clouds and precipitation over the summer of 2003 was performed. The NOAA Climate Prediction Center morphing techniques and the three-dimensional precipitation data observed by the TRMM Precipitation Radar were employed. The data were used to compute 3-hourly fields of cloud amounts and mean precipitation on a 0.25° lat/lon grid over a spatial domain of 22°-32°N; 120°-90°W for a 6-month period from May to October 2003. Time-longitude sections of mean cloudiness and precipitation were composited relative to the crest of the Sierra Madre Occidental. Results indicate that variations of cloudiness and precipitation associated with the NAMS are dominated by the diurnal cycle."
"57203424410;7402179527;","Long-term trends in solar radiation and the associated climatic factors over China for 1961-2000",2005,"10.5194/angeo-23-2425-2005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27844573801&doi=10.5194%2fangeo-23-2425-2005&partnerID=40&md5=7ee1c43af16cc69105bf83ebaf9fb92c","Long-term trends in downwelling solar irradiance and associated climatic factors over China are studied in the paper. Decreasing trends in global and direct radiation are observed over much of China. The largest decrease occurs in South and East China (east of about 100° E and south of about 40°N). The spatial pattern of observed trends in diffuse irradiance is complex and inhomogeneous. An intriguing aspect of trends in global and direct irradiance is the rather abrupt decrease in annual and seasonal mean values from 1978 onward. The decreasing trends in solar radiation in China did not persist into the 1990s. The spatial and temporal patterns of trends in sunshine duration are consistent with that of global and direct irradiance. A decreasing trend in rainy days is observed over much of China, which is in agreement with the secular trend in cloud amount. The fact that trends in cloud amount and solar radiation are quite similar suggests that the cloud amount is not the primary cause for the decrease in solar radiation. Visibility in the eastern part of China has deteriorated heavily as a result of the rapid increase in aerosol loading. The statistical analysis showed that atmospheric transmission under clear conditions decreased rapidly. These facts suggest that the rapid increase in aerosol loading should be one of the principle causes for the decrease in solar radiation. The observed diurnal temperature range decreases remarkably in China, which is closely related to the increase in aerosols. The effects of anthropogenic air pollutants on climate should be further studied and included in the simulation of climate and projection of climate scenario. © European Geosciences Union 2005."
"15841350300;8670213100;6507681572;6603395511;7004639116;6602137840;6701796418;","Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984-2000",2005,"10.5194/acp-5-1721-2005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23744512933&doi=10.5194%2facp-5-1721-2005&partnerID=40&md5=c4bb68654112eb735a947fa211c38914","A decadal-scale trend in the tropical radiative energy budget has been observed recently by satellites, which however is not reproduced by climate models. In the present study, we have computed the outgoing shortwave radiation (OSR) at the top of atmosphere (TOA) at 2.5° longitude-latitude resolution and on a mean monthly basis for the 17-year period 1984-2000, by using a deterministic solar radiative transfer model and cloud climatological data from the International Satellite Cloud Climatology Project (ISCCP) D2 database. Anomaly time series for the mean monthly pixel-level OSR fluxes, as well as for the key physical parameters, were constructed. A significant decreasing trend in OSR anomalies, starting mainly from the late 1980s, was found in tropical and subtropical regions (30° S-30° N), indicating a decadal increase in solar planetary heating equal to 1.9±0.3 Wm-2/ decade, reproducing well the features recorded by satellite observations, in contrast to climate model results. This increase in solar planetary heating, however, is accompanied by a similar increase in planetary cooling, due to increased outgoing longwave radiation, so that there is no change in net radiation. The model computed OSR trend is in good agreement with the corresponding linear decadal decrease of 2.5±0.4 Wm-2/decade in tropical mean OSR anomalies derived from ERBE S-10N nonscanner data (edition 2). An attempt was made to identify the physical processes responsible for the decreasing trend in tropical mean OSR. A detailed correlation analysis using pixel-level anomalies of model computed OSR flux and ISCCP cloud cover over the entire tropical and subtropical region (30° S-30° N), gave a correlation coefficient of 0.79, indicating that decreasing cloud cover is the main reason for the tropical OSR trend. According to the ISCCP-D2 data derived from the combined visible/infrared (VIS/IR) analysis, the tropical cloud cover has decreased by 6.6±0.2% per decade, in relative terms. A detailed analysis of the interannual and long-term variability of the various parameters determining the OSR at TOA, has shown that the most important contribution to the observed OSR trend comes from a decrease in low-level cloud cover over the period 1984-2000, followed by decreases in middle and high-level cloud cover. Note, however, that there still remain some uncertainties associated with the existence and magnitude of trends in ISCCP-D2 cloud amounts. Opposite but small trends are introduced by increases in cloud scattering optical depth of low and middle clouds. © 2005 Author(s). This work is licensed under a Creative Commons License."
"55770344900;6603956493;6701775424;7006215690;","Floristics and structure of the mossy cloud forest of Mt Gower summit, Lord Howe Island",2005,"10.1071/PC050246","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28844479795&doi=10.1071%2fPC050246&partnerID=40&md5=4fcdb518d207d33fed7834de2a38b152","The summit of Mt Gower, Lord Howe Island (31°33′S, 159°05′E), is a small area of 27 ha supporting mossy cloud forest. This study describes patterns in the floristic composition and structure of the vegetation of the summit, in relation to a range of environmental variables. A total of 42 vascular plant species was recorded, 86% of which are endemic to Lord Howe Island, and 17% of which are found only on the summit and upper slopes of Mt Gower and adjacent Mt Lidgbird. A complete species list for Mt Gower is presented, including species from the present survey and all previously recorded species. The composition of the vegetation differed in gullies and on ridges, reflecting differences in substrate rockiness and soil moisture, and was also influenced by the number of bird burrows and aspect. The summit of Mt Gower is of high conservation significance, due to the restricted distribution of the habitat type it represents, its relatively undisturbed state and high levels of endemism. Potential threats to the summit vegetation include the impacts of climate change, seed predation by introduced rats, and the introduction of weed species and exotic pathogens such as Phytophthora cinnamomi."
"6603831835;6603055155;6701346187;7202772338;6701796332;7005421048;6603151089;7101658117;6603158380;6505791876;6701462551;14015514600;6603265184;","The atmospheric dynamics mission for global wind field measurement",2005,"10.1175/BAMS-86-1-73","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20044390366&doi=10.1175%2fBAMS-86-1-73&partnerID=40&md5=4f97daf7403a6e9a73cef01ee5171a78","The prime aim of the Atmospheric Dynamics Mission is to demonstrate measurements of vertical wind profiles from space. Extensive studies conducted by the European Space Agency over the past 15 years have culminated in the selection of a high-performance Dopper wind lidar based on direct-detection interferometric techniques. Such a system, with a pulsed laser perating at 355-nm wavelength, would utilize both Rayleigh scattering from molecules and Mie scattering from thin cloud and aerosol particles; measurement of the residual Dopler shift from successive levels in the atmosphere provides the vertical wind profiles. The lidar would be accommodated on a satellite flying in a sun-synchronous orbit, at an altitute of ∼400 km, providing near-global coverage; target date for launch is in 2007. Processing of the backscatter signals will provide about 3000 globally distributed wind profiles per day, above thick clouds or down to the surface in clear air, at typically 200-km separation along the satellite track. Such improved knowledge of the global wind field is crucial to many aspects of climate research and weather prediction. Knowledge over large parts of the Tropics and major oceans is presently quite incomplete-leading to major difficulties in studying key processes in the climate system and in improving numerical simulations and predictions; progress in climate modeling is indeed intimately linked to progress in numerical weather prediction. The background studies, potential impact on climate and weather prediction, choice of measurement specifications, and the lidar technology are discussed. © 2005 American Meteorological Society."
"57197784699;35498501900;57198460524;","On the importance of cumulus penetration on the microphysical and optical properties of stratocumulus clouds",2005,"10.5194/acp-5-755-2005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16444380042&doi=10.5194%2facp-5-755-2005&partnerID=40&md5=d578cec39bc4edd9328bb1b7e3bbf707","Owing to their extensive spatial coverage, stratocumulus clouds play a crucial role in the radiation budget of the earth. Climate models need an accurate characterisation of stratocumulus in order to provide an accurate forecast. However, remote sensing as well as in-situ observations reveal that on several occasions, cumulus clouds present below the stratocumulus, often have a significant impact on the main stratocumulus microphysical properties. This was observed during the ACE-2 (Aerosol Characterisation Experiment-2) campaign designed to study the impact of polluted continental air on stratocumulus formation. In this paper we used a detailed micro-physical chemical parcel model to quantify the extent of this cumulus-stratocumuls coupling. In addition, we made extensive use of microphysical observations from the C-130 aircraft that was operated during ACE-2. For the ACE-2 case studies considered in this paper, our analysis revealed that the chemical, micro-physical and optical characteristics of the main stratocumulus cloud deck had significant contributions from cumulus clouds that often penetrated the stratocumulus deck. The amount of fine mode ionic species, the average droplet number concentrations, the effective radii and the optical depths during the flight A562 (when cumulus clouds interacted with the main stratocumulus) were estimated and model runs that included this effect yielded microphysical and optical properties which compared more favourably with the observations than the runs which did not. This study highlights the importance of including these cumulus effects in stratocumulus related modelling studies. © 2005 Author(s). This work is licensed under a Creative Commons License."
"55218830300;7102604282;","Uncertainty analysis for estimates of the first indirect aerosol effect",2005,"10.5194/acp-5-2935-2005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30344466066&doi=10.5194%2facp-5-2935-2005&partnerID=40&md5=7ebf28e17a141e1303991c90d1ffb1fd","The IPCC has stressed the importance of producing unbiased estimates of the uncertainty in indirect aerosol forcing, in order to give policy makers as well as research managers an understanding of the most important aspects of climate change that require refinement. In this study, we use 3-D meteorological fields together with a radiative transfer model to examine the spatially-resolved uncertainty in estimates of the first indirect aerosol forcing. The global mean forcing calculated in the reference case is - 1.30 Wm-2. Uncertainties in the indirect forcing associated with aerosol and aerosol precursor emissions, aerosol mass concentrations from different chemical transport models, aerosol size distributions, the cloud droplet parameterization, the representation of the in-cloud updraft velocity, the relationship between effective radius and volume mean radius, cloud liquid water content, cloud fraction, and the change in the cloud drop single scattering albedo due to the presence of black carbon are calculated. The aerosol burden calculated by chemical transport models and the cloud fraction are found to be the most important sources of uncertainty. Variations in these parameters cause an underestimation or overestimation of the indirect forcing compared to the base case by more than 0.6 Wm-2. Uncertainties associated with aerosol and aerosol precursor emissions, uncertainties in the representation of the aerosol size distribution (including the representation of the pre-industrial size distribution), and uncertainties in the representation of cloud droplet spectral dispersion effect cause uncertainties in the global mean forcing of 0.2∼0.6 Wm-2. There are significant regional differences in the uncertainty associated with the first indirect forcing with the largest uncertainties in industrial regions (North America, Europe, East Asia) followed by those in the major biomass burning regions. © 2005 Author(s). This work is licensed under a Creative Commons License."
"12805239400;","On the distribution and variability of water vapour in the middle atmosphere of Venus",2005,"10.1016/j.asr.2005.09.021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27844561483&doi=10.1016%2fj.asr.2005.09.021&partnerID=40&md5=c7982db9a806ae30281c492b1636135a","Water is a key constituent of every planetary environment, and on Venus its abundance, distribution and temporal behaviour are crucial for understanding greenhouse warming, cloud formation and dissipation, volcanism, and atmospheric evolution. Many telescopic and spacecraft-based observations of atmospheric water vapour on Venus have been made, but are inconclusive about its role as a component of the current climate system on the planet. The data suggest that H 2 O may be well mixed in the lower atmosphere, but highly variable in and near the cloud layers, and probably also at the thermospheric levels where dissociation and loss occur. The details of the middle atmosphere variability, how significant it is, and the processes responsible, remain controversial. In particular, the Pioneer Venus Infrared Radiometer found a large 'wet patch', a localized region where the water vapour mixing ratio is generally enhanced by one to two orders of magnitude over the global mean, occurring at low latitudes in the mid-afternoon, that has not been confirmed by other observations. If it is real, the presently unknown mechanism that produces it may be an important part of the water cycle in the Venusian atmosphere. Here we reconsider this problem, and some of the possible processes that may be involved, prior to the expected acquisition of relevant new data by Venus Express and the Venus Climate Orbiter. © 2005 COSPAR. Published by Elsevier Ltd. All rights reserved."
"7404586141;","Human Thermal Climates in China",2005,"10.2747/0272-3646.26.3.163","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144440745&doi=10.2747%2f0272-3646.26.3.163&partnerID=40&md5=d363000c649af67403a040858f07b5f9","The clo index, which indicates the amount of clothing required to maintain comfort, is used to evaluate the human thermal climates in China. Daily clo values for 200 stations were computed using daily air temperature, wind speed, and cloud-cover data from 1960 to 1998, and they were reduced and grouped into seasonal values. In winter, the roughly zonal pattern of thermal stress reflects the influence of latitude. In summer, the spatial pattern becomes more meridional. In eastern China, seasonal monsoon and maritime effects are crucial factors determining spatial variations of physioclimates. In western China, altitude and local topography play an important role in shaping the bioclimatic patterns. For the regional patterns of severe thermal stress, during the winter months, the northeast and northwest experience the highest percent of stressful time. In summer, the most oppressive heat stress is located in areas east of the Sichuan Basin and south of Huaihe River. © 2005 Taylor & Francis Group, LLC."
"16029719200;7004299063;6701413579;35561911800;6604021707;","Climatic response to high-latitude volcanic eruptions",2005,"10.1029/2004JD005487","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646804826&doi=10.1029%2f2004JD005487&partnerID=40&md5=67fbf504ab84610d2a32f13b38f2b17b","Strong volcanic eruptions can inject large amounts ot SO<inf>2</inf> into the lower stratosphere, which over time, are converted into sulfate aerosols and have the potential to impact climate. Aerosols from tropical volcanic eruptions like the 1991 Mount Pinatubo eruption spread over the entire globe, whereas high-latitude eruptions typically have aerosols which remain in the hemisphere in which they where injected. This causes their largest radiative forcing to be extratropical, and the climate response should be different from that of tropical eruptions. We conducted a 20-member ensemble simulation of the climate response to the Katmai eruption (58°.N) of 6 June 1912 using the NASA Goddard Institute for Space Studies ModelE climate model. We also produced an additional 20-member ensemble for a 3 times Katmai (3x Katmai) eruption to see the impact the strength of the eruption has on the radiative as well as the dynamical responses. The results of these simulations do not show a positive Arctic Oscillation response like past simulations of tropical volcanic eruptions, but we did find significant cooling over southern Asia during the boreal winter. The first winter following Katmai and the second winter following 3x Katmai showed strong similarities in lower stratospheric geopotential height anomalies and sea level pressure anomalies, which occurred when the two cases had similar optical depth perturbations. These simulations show that the radiative impact of a high-latitude volcanic eruption was much larger than the dynamical impact at high latitudes. In the boreal summer, however, strong cooling over the Northern Hemisphere landmasses caused a decrease in the Asian monsoon circulation with significant decreases of up to 10% in cloud cover and warming over northern India. Thus the main dynamical impact of highlatitude eruptions is in the summer over Asia. Copyright 2005 by the American Geophysical Union."
"9844618400;","A coupled model study on the intensification of the Asian summer monsoon in IPCC SRES scenarios",2005,"10.1007/BF02918680","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28844494137&doi=10.1007%2fBF02918680&partnerID=40&md5=c955f556e434066f0842911cac636cc1","The Asian summer monsoon is an important part of the climate system. Investigating the response of the Asian summer monsoon to changing concentrations of greenhouse gases and aerosols will be meaningful to understand and predict climate variability and climate change not only in Asia but also globally. In order to diagnose the impacts of future anthropogenic emissions on monsoon climates, a coupled general circulation model of the atmosphere and the ocean has been used at the Max-Planck-Institute for Meteorology. In addition to carbon dioxide, the major well mixed greenhouse gases such as methane, nitrous oxide, several chlorofluorocarbons, and CFC substitute gases are prescribed as a function of time. The sulfur cycle is simulated interactively, and both the direct aerosol effect and the indirect cloud albedo effect are considered. Furthermore, changes in tropospheric ozone have been pre-calculated with a chemical transport model and prescribed as a function of time and space in the climate simulations. Concentrations of greenhouse gases and anthropogenic emissions of sulfur dioxide are prescribed according to observations (1860-1990) and projected into the future (1990-2100) according to the Scenarios A2 and B2 in Special Report on Emissions Scenarios (SRES, Nakiéenović et al., 2000) developed by the Intergovernmental Panel on Climate Change (IPCC). It is found that the Indian summer monsoon is enhanced in the scenarios in terms of both mean precipitation and interannual variability. An increase in precipitation is simulated for northern China but a decrease for the southern part. Furthermore, the simulated future increase in monsoon variability seems to be linked to enhanced ENSO variability towards the end of the scenario integrations."
"7003908632;27267529400;55247122500;","Effects of arctic sulphuric acid aerosols on wintertime low-level atmospheric ice crystals, humidity and temperature at Alert, Nunavut",2005,"10.1016/j.atmosres.2004.08.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10644284575&doi=10.1016%2fj.atmosres.2004.08.002&partnerID=40&md5=da7398f1e67740f44ea0c28032d129f8","The effect of pollution-derived sulphuric acid aerosols on wintertime arctic lower atmospheric ice crystals is investigated. These anthropogenic aerosols differ from natural background aerosols by their number concentration, strong solubility and reduced homogeneous freezing temperature when internally mixed with other compounds. Furthermore, observations suggest that the ice-forming nuclei concentration is reduced by one to four orders of magnitude when the sulphuric acid aerosol concentration is high. Simulations performed using a column model and analysis of observed data for the period of 1991-1994 at Alert (82° 30'N, 62°20'W) are used to assess the changes of the boundary layer cloud characteristics by sulphuric acid aerosols and the potential effect on arctic climate. Results show that aerosol acidification leads to depletion of the ice crystal number concentration and an increase of its mean size. As a result, low-level precipitating ice crystals occur more frequently than ice fog and thick nonprecipitating clouds during high concentration of pollution-derived aerosols. This result is in agreement with observations that indicate an increase by more than 50% of the frequency of precipitating ice crystals when the weight proportion of sulphuric acid is greater than its mean value of 20% of the total aerosol mass. Consequently, the ice crystal size increases and number decreases, and the sedimentation flux of ice crystals and the dehydration rate of the lower troposphere are accelerated in the presence of high sulphuric acid aerosol concentration. As a result, the infrared radiation flux reaching the surface and the greenhouse effect are decreased. This process is referred to as the dehydration-greenhouse feedback. One-dimensional simulation for Alert during the period of 1991 to 1994 shows that a negative cloud radiative forcing of -9 W m-2 may occur locally as a result of the enhanced dehydration rate produced by the aerosol acidity. © 2004 Elsevier B.V. All rights reserved."
"7103293232;9249742700;","A preliminary study of students' asking quantitative scientific questions for inquiry-based climate model experiments",2005,"10.5408/1089-9995-53.4.432","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744537685&doi=10.5408%2f1089-9995-53.4.432&partnerID=40&md5=5d15d676abed9574eaf286b27574c5d0","The cognitive apprenticeship method is used to promote conceptual learning in climate science by encouraging student inquiry, which literature shows to be conducive to learning a multi-faceted topic. A course was taught with this approach, whereby students conducted their own research using an up-to-date user-friendly climate model. Five topics addressed in this class are investigated here: Earth Radiation Budget and Clouds, Greenhouse Effect, Ozone, Aerosols and Surface Processes. Assigned reading served as the basis for individual questions, while lectures and discussions helped to define group research questions and associated projects whose results were presented in class. Our analysis of students' questions shows improvement in students' ability to formulate questions in terms of the variable's applicability to the model. Mid-range and low-scoring students showed abrupt and gradual improvement, respectively, while higher-scoring students tended to immediately and consistently perform well. Due to the limited data set for this pilot study, these patterns of improvement are used only as an indication that conceptual learning has taken place. Nevertheless, the results of this study will aid in the experimental design of the next class offering."
"8921632800;7006208962;14321759900;14322233900;","Nowcasting of convective cells over Italian Peninsula",2005,"10.5194/adgeo-2-173-2005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748036423&doi=10.5194%2fadgeo-2-173-2005&partnerID=40&md5=ec3c767335be037a476187e66b1ee6be","The aim of the study is the individuation of convective cells over the Italian peninsula with the conjunction use of geostationary satellite data (METEOSAT, MSG satellite) in the IR and WV channels and lightning data. We will use GCD (Global Convective Diagnostic) algorithm developed at Aviation Weather Centre (AWC) of NOAA (National Oceanic and Atmospheric Administration). This algorithm is based on the idea that a deep convective cloud will not have any significant moisture above it. This technique works quite well at identifying active deep convection and can be applied to all the world's geostationary satellites. However it does not always agree with lightning sensors. Low topped convection with lightning will be missed. We will extend the capabilities of GCD using lightning data. The new product will be validate over different cases in the central Italy using the C-band polarimetric radar of ISAC-CNR (Institute of Atmospheric Sciences and Climate-of the Italian National Research Council) Rome."
"7007148434;56251307100;56054157600;7006643234;7004864963;7102830450;11140433400;6602675083;11140220700;57201177267;8786620100;57147018500;35461763400;","Airborne measurements of trace gas and aerosol particle emissions from biomass burning in Amazonia",2005,"10.5194/acp-5-2989-2005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30344481106&doi=10.5194%2facp-5-2989-2005&partnerID=40&md5=d955e64395f7400024ac0a9de5b4dd7a","As part of the LBA-SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke, Aerosols, Clouds, Rainfall, and Climate) 2002 campaign, we studied the emission of carbon monoxide (CO), carbon dioxide (CO2), and aerosol particles from Amazonian deforestation fires using an instrumented aircraft. Emission ratios for aerosol number (CN) relative to CO (ERCN/CO) fell in the range 14-32cm-3 ppb-1 in most of the investigated smoke plumes. Particle number emission ratios have to our knowledge not been previously measured in tropical deforestation fires, but our results are in agreement with values usually found from tropical savanna fires. The number of particles emitted per amount biomass burned was found to be dependent on the fire conditions (combustion efficiency). Variability in ERCN/CObetween fires was similar to the variability caused by variations in combustion behavior within each individual fire. This was confirmed by observations of CO-to-CO2 emission ratios (ERCO/CO2), which stretched across the same wide range of values for individual fires as for all the fires observed during the sampling campaign, reflecting the fact that flaming and smoldering phases are present simultaneously in deforestation fires. Emission factors (EF) for CO and aerosol particles were computed and a correction was applied for the residual smoldering combustion (RSC) fraction of emissions that are not sampled by the aircraft, which increased the EF by a factor of 1.5-2.1. Vertical transport of smoke from the boundary layer (BL) to the cloud detrainment layer (CDL) and the free troposphere (FT) was found to be a very common phenomenon. We observed a 20% loss in particle number as a result of this vertical transport and subsequent cloud processing, attributable to in-cloud coagulation. This small loss fraction suggests that this mode of transport is very efficient in terms of particle numbers and occurs mostly via non-precipitating clouds. The detrained aerosol particles released in the CDL and FT were larger than in the unprocessed smoke, mostly due to coagulation and secondary growth, and therefore more efficient at scattering radiation and nucleating cloud droplets. This process may have significant atmospheric implications on a regional and larger scale. © 2005 Author(s). This work is licensed under a Creative Commons License."
"6701689811;35577097300;","Radiative effects of natural aerosols: A review",2005,"10.1016/j.atmosenv.2004.12.029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16344382454&doi=10.1016%2fj.atmosenv.2004.12.029&partnerID=40&md5=ef781c3e5a1c690ebde61cf79ef297c9","In recent years, there has been a substantial increase in interest in the influence of anthropogenic aerosols on climate through both direct and indirect effects. Several extensive investigations and coordinated field campaigns have been carried out to assess the impact of anthropogenic aerosols on climate. However, there are far fewer studies on natural aerosols than on anthropogenic aerosols, despite their importance. Natural aerosols are particularly important because they provide a kind of base level to aerosol impact, and there is no effective control on them, unlike their anthropogenic counterparts. Besides, on a global scale the abundance of natural aerosols is several times greater than that of the major anthropogenic aerosols (sulphate, soot and organics). The major natural aerosol components are sea salt, soil dust, natural sulphates, volcanic aerosols, and those generated by natural forest fires. As with anthropogenic aerosols, the abundance of natural aerosols such as soil dust is also increasing, due to processes such as deforestation, which exposes more land areas which may then interact directly with the atmosphere, and due to other human activities. Since a major fraction of the natural aerosol (sea salt and natural sulphate) is of the non-absorbing type (and hygroscopic), it partly offsets the warming due to greenhouse gases as well as that due to absorbing aerosols (e.g., soot). The mineral dust transported over land and ocean causes surface cooling (due to scattering and absorption) simultaneously with lower atmospheric heating (due to absorption); this could in turn intensify a low-level inversion and increase atmospheric stability and reduce convection. To accurately predict the impact of dust aerosols on climate, the spatial and temporal distribution of dust is essential. The regional characteristics of dust source function are poorly understood due to the lack of an adequate database. The reduction of solar radiation at the surface would lead to a reduction in the sensible heat flux and all these will lead to perturbations in the regional and global climate. Enhanced concentration of sea salt aerosols at high wind speed would lead to more condensation nuclei, increase in the cloud droplet concentration and hence cloud albedo. Even though direct radiative impacts due to sea salt and natural sulphate are small compared to those due to anthropogenic counterparts, their indirect effects (and the uncertainties) are much larger. There is a considerable uncertainty in sea salt aerosol radiative forcing due to an inadequate database over oceans. The presence of natural aerosols may influence the radiative impact of anthropogenic aerosols, and it is difficult to separate the natural and anthropogenic aerosol contributions to radiative forcing when they are in a mixed state. Hence it is necessary to document the radiative effects of natural aerosols, especially in the tropics where the natural sources are strong. This is the subject matter of this review. © 2005 Elsevier Ltd. All rights reserved."
"7004627399;7004089395;","Shortwave radiative forcing efficiency of urban aerosols - A case study using ground based measurements",2005,"10.1016/j.chemosphere.2004.09.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-9644275761&doi=10.1016%2fj.chemosphere.2004.09.013&partnerID=40&md5=cad204c86585a756e16106c48c315fb6","Importance of this paper: Measurements of spectral solar flux reaching the surface in cloud free conditions are required to determine the aerosol radiative impact and validate models used for calculating radiative forcing. Aerosols reduce the surface reaching solar flux by scattering the incoming solar radiation out to space. Various model studies on climate change suggest that surface cooling induced by aerosol scattering is the largest source of uncertainty in predicting the future climate. In the present study measurements of aerosol optical depth (AOD) and its direct radiative forcing efficiency has been presented over a typical tropical urban environment namely Hyderabad during December, 2003. Measurements of AOD have been carried out using MICROTOPS-II sunphotometer, black carbon aerosol mass concentration using Aethalometer, total aerosol mass concentration using channel Quartz Crystal Microbalance (QCM) Impactor Particle analyser and direct normal solar irradiance using Multifilter Rotating Shadow Band Radiometer (MFRSR). Diurnal variation of AOD showed high values during afternoon hours. The fraction of BC estimated to be ∼9% in the total aerosol mass concentration over the study area. Results of the study suggest -62.5 Wm -2 reduction in the ground reaching shortwave flux for every 0.1 increase in aerosol optical depth. The results have been discussed in the paper. © 2004 Elsevier Ltd. All rights reserved."
"8687996600;57201772099;57209089997;","Role of the hydrological cycle in regulating the planetary climate system of a simple nonlinear dynamical model",2005,"10.5194/npg-12-741-2005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24144456256&doi=10.5194%2fnpg-12-741-2005&partnerID=40&md5=fe51995930091afb3441801b7439ccaf","We present the construction of a dynamic area fraction model (DAFM), representing a new class of models for an earth-like planet. The model presented here has no spatial dimensions, but contains coupled parameterizations for all the major components of the hydrological cycle involving liquid, solid and vapor phases. We investigate the nature of feedback processes with this model in regulating Earth's climate as a highly nonlinear coupled system. The model includes solar radiation, evapotranspiration from dynamically competing trees and grasses, an ocean, an ice cap, precipitation, dynamic clouds, and a static carbon greenhouse effect. This model therefore shares some of the characteristics of an Earth System Model of Intermediate complexity. We perform two experiments with this model to determine the potential effects of positive and negative feedbacks due to a dynamic hydrological cycle, and due to the relative distribution of trees and grasses, in regulating global mean temperature. In the first experiment, we vary the intensity of insolation on the model's surface both with and without an active (fully coupled) water cycle. In the second, we test the strength of feedbacks with biota in a fully coupled model by varying the optimal growing temperature for our two plant species (trees and grasses). We find that the negative feedbacks associated with the water cycle are far more powerful than those associated with the biota, but that the biota still play a significant role in shaping the model climate. third experiment, we vary the heat and moisture transport coefficient in an attempt to represent changing atmospheric circulations. © 2005 Author(s). This work is licensed under a Creative Commons License."
"27170375100;55418553100;56006103500;","A sensitivity study of regional climate simulation to convective parameterization schemes for 1998 East Asia summer monsoon",2005,"10.3319/TAO.2005.16.5.989(RCS)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31444443038&doi=10.3319%2fTAO.2005.16.5.989%28RCS%29&partnerID=40&md5=2a8e83497cb7f6a54422a92a825db965","A sensitivity study of regional climate simulations over East Asia to three convective parameterization schemes (CPSs), the Grell, Kain-Fritsch, and Anthes-Kuo schemes, was conducted using a regional climate model, SNURCM with a 60 km horizontal resolution. Nesting experiments with a 20 km horizontal resolution were also performed in order to investigate the sensitivity of CPSs to horizontal resolution. In all runs with 60 km horizontal resolution, seasonal mean precipitation, low- and upper-level wind, and temporal and spatial variation of monsoon fronts over East Asia were simulated with a certain difference between CPSs. With higher horizontal resolution, all the schemes were likely to increase slightly the total precipitation amount and the precipitation intensity due to the increase of convective rain, but differences in the spatial distribution of precipitation between CPSs were relatively small. There were prominent differences in vertical profiles of wind, temperature, water vapor, and atmospheric hydrometeors amongst CPSs, although the vertical, structures of those in GR and KF runs were similar to each other. Sensitivities of the vertical structure of most atmospheric variables to horizontal resolution were relatively smaller than they were to CPSs except for cloud water. Surface energy fluxes, in particular incoming solar radiation and latent heat between CPSs were different to each other because of differences in the vertical structure of atmospheric hydrometeors. Diurnal variation of precipitation was also sensitive to not only CPSs but also horizontal resolution. In this study, the AK scheme reproduced the East Asian Summer precipitation properly because of intrinsic triggering assumptions and the spectral nudging technique. The GR scheme was on the whole suitable to simulate the general features of East Asian summer monsoon in 1998 such as heavy precipitation, atmospheric vertical structure, and temporal evolution of the East Asian Summer monsoon. The KF scheme had the worst statistics in precipitation simulation due to large convective precipitation portion. Consequently, the AK and GR schemes simulated more reasonably the 1998 summer flood over East Asia which was affected by anomalous large-scale condition."
"23392287100;7005316058;6603162518;","An attempt to define the Road Climate Room",2005,"10.1017/S1350482705001945","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31144462532&doi=10.1017%2fS1350482705001945&partnerID=40&md5=3fa26918d9d55d999e58ddcc9cd13423","Since the start of field station manufacturing approximately 25 years ago, the configuration of Road Weather Information System (RWIS) stations and the type of sensors used has changed very little. Little is known about the variation of climatic variables from the 2 m level, where instruments are normally placed, down to the road surface. The 'Road Climate Room' can be defined as the volume of air, road and surroundings influencing the conditions on the road. This study attempts to describe the Road Climate Room both theoretically and experimentally. Mobile measurements as well as a permanent station were used. At the permanent station detailed temperature measurements above and beside the road were made. These were related to other climatic variables such as wind, cloudiness, humidity and ground heat flux. The results show that the most important processes occur below the 10 cm level. The air column above this level is well represented by the 2 m level temperature sensor. For most situations the cooling of the air closest to the ground is much more intense in the vegetation than over the road. The temperature difference can be as large as 8 °C and can be represented statistically with high determination by wind and cloudiness. The heat storage in the road is a key factor for keeping the temperature of the road high throughout a full diurnal cycle. The cold air in the vegetation can be considered as a potential source for cold air drainage onto the road surface in terrain where that is a problem. No advection affecting the road surface was observed at the permanent station. This suggests that the Road Climate Room can be defined as being well within the internal boundary layer of the road. The mobile measurements, however, show that advection from the surroundings is likely to have taken place, which makes the definition of the Road Climate Room more difficult. Further studies are needed to fully understand the complicated processes."
"55718747400;7402270607;","Numerical simulation of the impact of vegetation index on the interannual variation of summer precipitation in the Yellow River Basin",2005,"10.1007/bf02918686","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28844499192&doi=10.1007%2fbf02918686&partnerID=40&md5=eca8077b06030f4ddb6db4cd724d0638","Two sets of numerical experiments using the coupled National Center for Environmental Prediction General Circulation Model (NCEP/GCM T42L18) and the Simplified Simple Biosphere land surface scheme (SSiB) were carried out to investigate the climate impacts of fractional vegetation cover (FVC) and leaf area index (LAI) on East Asia summer precipitation, especially in the Yellow River Basin (YRB). One set employed prescribed FVC and LAI which have no interannual variations based on the climatology of vegetation distribution; the other with FVC and LAI derived from satellite observations of the International Satellite Land Surface Climate Project (ISLSCP) for 1987 and 1988. The simulations of the two experiments were compared to study the influence of FVC, LAI on summer precipitation interannual variation in the YRB. Compared with observations and the NCEP reanalysis data, the experiment that included both the effects of satellite-derived vegetation indexes and sea surface temperature (SST) produced better seasonal and interannual precipitation variations than the experiment with SST but no interannual variations in FVC and LAI, indicating that better representations of the vegetation index and its interannual variation may be important for climate prediction. The difference between 1987 and 1988 indicated that with the increase of FVC and LAI, especially around the YRB, surface albedo decreased, net surface radiation increased, and consequently local evaporation and precipitation intensified. Furthermore, surface sensible heat flux, surface temperature and its diurnal variation decreased around the YRB in response to more vegetation. The decrease of surface-emitting longwave radiation due to the cooler surface outweighed the decrease of surface solar radiation income with more cloud coverage, thus maintaining the positive anomaly of net surface radiation. Further study indicated that moisture flux variations associated with changes in the general circulation also contributed to the precipitation interannual variation."
"7003663731;57207802764;","Frequency and magnitude of active-layer detachment failures in discontinuous and continuous permafrost, northern Canada",2005,"10.1002/ppp.522","https://www.scopus.com/inward/record.uri?eid=2-s2.0-15844410111&doi=10.1002%2fppp.522&partnerID=40&md5=634a7ec8f730a35cd34f6c4862f0f503","Active-layer detachment failures triggered weeks to months after forest fire in the central Mackenzie Valley (65°N, discontinuous permafrost zone) are compared to others generated almost immediately by summer meteorological conditions on the Fosheim Peninsula, Ellesmere Island (80°N, continuous permafrost zone). Preferred long-axis orientations in both zones vary in relation to valley geometry and ground ice distribution: differential insolation plays no direct role in detachment failure distribution. Rates of geomorphic work over periods of one to two centuries are of the same order of magnitude. Threshold meteorological conditions for initiating failures on the Fosheim Peninsula can be incorporated into a surface heating index, but pre-conditioning of the active layer remains important because rapid thaw does not always initiate activity. Slope pre-conditioning does not occur at the fire-affected sites because the failure zone is within formerly perennially frozen ground. Long-term rates of unit vertical transport at the most active site on the Fosheim Peninsula are similar to those due to debris flow and slushflow in a nearby mountain range. The frequency of potential triggering events at the Ellesmere Island sites is expected to increase if summer climate warms, providing low percentage cloud cover is maintained during periods of high air temperatures. Copyright © 2005 John Wiley & Sons, Ltd."
"7003821079;","Attenuation-based estimates of rainfall rates aloft with vertically pointing Ka-band radars",2005,"10.1175/JTECH-1677.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14344250841&doi=10.1175%2fJTECH-1677.1&partnerID=40&md5=d60ec6059363f740316c63f9428649de","An approach is suggested to retrieve low-resolution rainfall rate profiles and layer-averaged rainfall rates, Ra, from radar reflectivity measurements made by vertically pointing Ka-band radars. This approach is based on the effects of attenuation of radar signals in rain and takes advantage of the nearly linear relation between specific attenuation and rainfall rate at Ka-band frequencies. The variability of this relation due to temperature, details of raindrop size distributions, and the nature of rain (convective versus stratiform) is rather small (∼ 10%) and contributes little to errors in rainfall rate retrievals. The main contribution to the retrieval errors comes from the uncertainty of the difference in the nonattenuated radar reflectivities in the beginning and the end of the range resolution interval. For 2- and 1-dB uncertainties in this difference, the retrieval errors due to this main contribution are less than 34% and 17%, correspondingly, for rains with Ra ≈ 10 mm h-1 at a 1-km resolution interval. The heavier rain rates are retrieved with a better accuracy since this retrieval error contribution is proportional to 1/Ra. The retrieval accuracy can also be improved but at the expense of more coarse vertical resolutions of retrievals since the main retrieval error contribution is also proportional to the reciprocal of the resolution interval. The Mie scattering effects at Ka band results in less variability in nonattenuated reflectivities (cf. lower radar frequencies), which aids the suggested approach. Given that radar receivers are not saturated, the rainfall rates can be retrieved using cloud radars that were originally designed for measuring only nonprecipitating and weakly precipitating clouds. An important advantage of the attenuation-based retrievals of rainfall is that absolute radar calibration is not required. The inclusion of rainfall information will improve the characterization of the atmospheric column obtained with such radars used for climate research. The applications of the suggested approach are illustrated using the vertically pointing Ka-band radar measurements made during a field experiment in southern Florida. The retrieval results are in good agreement with surface estimates of rainfall rates. © 2005 American Meteorological Society."
"8942525300;8942524900;7004469744;7004402705;35810775100;","A global off-line model of size-resolved aerosol microphysics: II. Identification of key uncertainties",2005,"10.5194/acp-5-3233-2005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30844458408&doi=10.5194%2facp-5-3233-2005&partnerID=40&md5=65c1c8775cdf69263fef20a9d30626a4","We use the new GLOMAP model of global aerosol microphysics to investigate the sensitivity of modelled sulfate and sea salt aerosol properties to uncertainties in the driving microphysical processes and compare these uncertainties with those associated with aerosol and precursor gas emissions. Overall, we conclude that uncertainties in microphysical processes have a larger effect on global sulfate and sea salt derived condensation nuclei (CN) and cloud condensation nuclei (CCN) concentrations than uncertainties in present-day sulfur emissions. Our simulations suggest that uncertainties in predicted sulfate and sea salt CCN abundances due to poorly constrained microphysical processes are likely to be of a similar magnitude to long-term changes in sulfate and sea salt CCN due to changes in anthropogenic emissions. A microphysical treatment of the global sulfate aerosol allows the uncertainty in climate-relevant aerosol properties to be attributed to specific processes in a way that has not been possible with simpler aerosol schemes. In particular we conclude that: (1) changes in the binary H2SO4-H2O nucleation rate and condensation rate of gaseous H2SO4 cause a shift in the vertical location of the upper tropospheric CN layer by as much as 3 km, while the shape of the CN profile is essentially pre-served (2) uncertainties in the binary H2SO4-H2O nucleation rate have a relatively insignificant effect on marine boundary layer (MBL) aerosol properties; (3) emitting a fraction of anthropogenic SO2 as particulates (to represent production of sulfate particles in power plant plumes below the scale of the model grid (which is of the order of 300 km)) has the potential to change the global mean MBL sulfate-derived CN concentrations by up to 72%, and changes of up to a factor 20 can occur in polluted continental regions; (4) predicted global mean MBL sulfate and sea salt CCN concentrations change by 10 to 60% when several microphysical processes are changed within reasonable uncertainty ranges; (5) sulfate and sea salt derived CCN concentrations are particularly sensitive to primary particle emissions, with global mean MBL sulfate and sea salt CCN changing by up to 27% and local concentrations over continental regions changing by more than 100% when the percentage of anthropogenic SO2 emitted as particulates is changed from 0 to 5%; (6) large changes in sea spray flux have insignificant effects on global sulfate aerosol except when the mass accommodation coefficient of sulfuric acid on the salt particles is set unrealistically low. © 2005 Author(s). This work is licensed under a Creative Commons License."
"6508337270;6602635781;56472932500;","Modeling of in situ ultrafine atmospheric particle formation in the eastern United States",2005,"10.1029/2004JD004683","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30344474578&doi=10.1029%2f2004JD004683&partnerID=40&md5=aeb71cc966eeabcb9490faf8249407f4","The creation of new atmospheric particles from in situ nucleation influences climate through cloud-aerosol interactions and may negatively impact human health. Although recent observations show that nucleation is widespread in the eastern United States, the corresponding pathways remain uncertain. Combining extensive field measurements in Pittsburgh, Pennsylvania, with an aerosol dynamics and chemistry model assuming ternary NH<inf>3</inf>-H <inf>2</inf>SO<inf>4</inf>-H<inf>2</inf>O nuclei formation, we show excellent model-measurement agreement and predictive capability. The ternary NH <inf>3</inf>-H<inf>2</inf>SO<inf>4</inf>-H<inf>2</inf>O nucleation model is successful in predicting the presence or lack of nucleation on 19 out of 19 days with complete data sets in July 2001 and on 25 out of 29 days in January 2002. Reductions of ammonia emissions are predicted to decrease the frequency of nucleation events during both summer and winter, with a more dramatic effect during the summer. The response to changes in emissions of sulfur dioxide during the summer is counterintuitive. Reductions of sulfur dioxide and the resulting sulfate by up to 40% actually increase the frequency of the summer nucleation events. Modeling predicts the opposite effect in winter, with reductions of sulfur dioxide leading to fewer nucleation events. Copyright 2005 by the American Geophysical Union."
"7006366653;6507046956;9233453100;","Potential climatic effects of cirrus contrails for the subarctic setting of Fairbanks, Alaska",2005,"10.1007/s00704-004-0113-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21844463081&doi=10.1007%2fs00704-004-0113-0&partnerID=40&md5=3d9186595c097876e7dc25bd2b8f8485","Continuous all-sky camera images supported by direct visual observations of jet contrails have been carried out in Fairbanks since March 2000. These data together with FAA information of all commercial flights and the twice-daily radiosonde data, give the meteorological conditions at flight level under which contrails are formed. If we correct for daylight and clear sky conditions, which make contrail observations possible, winter has the maximum and summer the minimum in the occurrence of contrails. This is a result to be expected, as the layer in which contrails can form has in winter nearly twice the thickness when compared to summer. In November 2002, a radiation station was added to the observations. For a contrail in the path between the sun and the observation point, we found a strong decrease in the direct beam radiation; this loss was in part compensated by increased diffuse radiation. The combined effect leads to a reduction in global radiation. However, the back radiation of the atmosphere in the infrared region of the spectrum increased somewhat. Altogether, this affects the net radiation negatively in the summer, but positively in the winter. Comparing the observed temperature conditions of clear days with those of high-level cloud cover, we found for 8 months of the year a higher temperature for days with clouds. For the other four months, May through August, clear days were warmer. On the average of the year, days with high-level cloudiness were warmer than clear days as well as days with low-level overcast. High-level cloudiness has increased in Alaska over the last decades. This increase in cloudiness was more pronounced under the much-traveled flight corridor from Anchorage to Europe than for more remote areas of Alaska. Further, we found a temperature increase for the same time period, which was most pronounced in winter, followed by spring, a result consistent of the expectations of increased high-level cloudiness. © Springer-Verlag/Wien 2005."
"8435608400;8420514500;7401806579;","A case study on a strong tropical disturbance and record heavy rainfall in Hat Yai, Thailand during the winter monsoon",2005,"10.1007/BF02918757","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20344406778&doi=10.1007%2fBF02918757&partnerID=40&md5=20983e6bc5d0f94fdd9d6fc074587b4f","The evolutionary process and structural characteristics of the atmospheric circulation and synoptic situation which caused the record heavy rainfall with a precipitation amount of 550 mm in Hat Yai, Thailand from 20 to 23 November 2000 is studied. In the study, the modern three dimensional observational data were collected as completely as possible, and detailed analyses were made. It is revealed that the cold surges of the Asian winter monsoon that originate from Siberia can arrive at the lower latitudes, including South Thailand, Malaysia, Indonesia, cause strong heavy rainfall there, and interact with weather systems in the near-equatorial regions of the Southern Hemisphere. This is strongly supported by Chinese scientist's original finding in 1930s. The strong convective cloud clusters in the above areas are generated by the direct influence of the cold surges, and are related with the South China Sea disturbances in the lower troposphere. The maximum of the convergence of total moisture flux near South Thailand in the situation under study implies that the water vapour supply is abundant and very favorable to the occurrence of the heavy rainfall. The release of latent heat enhances the Hadley Circulation also. The feedback of the strong severe weather on climate indeed exists, and there are pronounced interactions between the multi-scale systems and between both hemispheres."
"8871497700;26643041500;55950593000;6507189548;6603729297;7004022660;7006712143;35461255500;","Effects of SO2 oxidation on ambient aerosol growth in water and ethanol vapours",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-16444385972&partnerID=40&md5=9cd7cd6af8ff37f22772746b19c0eced","Hygroscopicity (i.e. water vapour affinity) of atmospheric aerosol particles is one of the key factors in defining their impacts on climate. Condensation of sulphuric acid onto less hygroscopic particles is expected to increase their hgrocopicity and hence their cloud condensation nuclei formation potential. In this study, differences in the hygroscopic and ethanol uptake properties of ultrafine aerosol particles in the Arctic air masses with a different exposure to anthropogenic sulfur pollution were examined. The main discovery was that Aitken mode particles having been exposed to polluted air were more hygroscopic and less soluble to ethanol than after transport in clean air. This aging process was attributed to sulphur dioxide oxidation and subsequent condensation during the transport of these particle to our measurement site. The hygroscopicity of nucleation mode aerosol particles, on the other hand, was approximately the same in all the cases, being indicative of a relatively similar chemical composition despite the differences in air mass transport routes. These particles had also been produced closer to the observation site typically 3-8 h prior to sampling. Apparently, these particles did not have an opportunity to accumulate sulphuric acid on their way to the site, but instead their chemical composition (hygroscopicity and ethanol solubility) resembled that of particles produced in the local or semi-regional ambient conditions. © 2005 Author(s). This work is licensed under a Creative Commons License."
"11240127200;11339401400;6603931046;7003405691;7102692123;7003897194;57189998431;11240254900;11239835600;7004864963;56212802600;35461763400;","The NH4+-NO3--Cr-SO 42--H2O aerosol system and its gas phase precursors at a pasture site in the Amazon Basin: How relevant are mineral cations and soluble organic acids?",2005,"10.1029/2004JD005478","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28844489267&doi=10.1029%2f2004JD005478&partnerID=40&md5=b81e5dca6bd94f024586278776f6532c","Real-time measurements of ammonia, nitric acid, hydrochloric acid, sulfur dioxide and the water-soluble inorganic aerosol species, ammonium, nitrate, chloride, and sulfate were performed at a pasture site in the Amazon Basin (Rondônia, Brazil). The measurements were made during the late dry season (biomass burning), the transition period, and the onset of the wet season (clean conditions) using a wet-annular denuder (WAD) in combination with a Steam-Jet Aerosol Collector (SJAC). Measurements were conducted from 12 September to 14 November 2002 within the framework of LBA-SMOCC (Large-Scale Biosphere Atmosphere Experiment in Amazonia - Smoke Aerosols, Clouds, Rainfall, and Climate: Aerosols From Biomass Burning Perturb Global and Regional Climate). Real-time data were combined with measurements of sodium, potassium, calcium, magnesium, and low-molecular weight (LMW) polar organic acids determined on 12-, 24-, and 48-hours integrated filter samples. The contribution of inorganic species to the fine particulate mass (Dp ≤ 2.5 μm) was frequently below 20% by mass, indicating the preponderance of organic matter. The measured concentration products of NH3 × HNO3 and NH3 × HCl persistently remained below the theoretical equilibrium dissociation constants of the NH3/HNO3/NH 4NO3 and NH3/HCl/NH4Cl systems during daytime (RH &lt; 90%). The application of four thermodynamic equilibrium models (EQMs) indicates that the fine mode aerosol anions NO3 -, Cl-, and SO42- were balanced predominantly by mineral cations (particularly pyrogenic K+) during daytime. At nighttime (RH &gt; 90%) fine-mode NH4NO3 and NH3Cl are predicted to be formed in the aqueous aerosol phase. Probably, Cl- was driven out of the aerosol phase largely by reaction of pyrogenic KCl with HNO3 and H2SO4. As shown by an updated version of the equilibrium simplified aerosol model (EQSAM2), which incorporates mineral aerosol species and lumped LMW polar organic acids, daytime aerosol NH4+ was mainly balanced by organic compounds. Copyright 2005 by the American Geophysical Union."
"7006934305;57206526404;57211105491;7006589757;6602641633;35574839400;","Detection of mesoscale seasonal and interannual variation in the vegetation of the Amazon basin",2005,"10.1175/EI129.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955975080&doi=10.1175%2fEI129.1&partnerID=40&md5=57b24c4a6b7940d846080ea72e6ed39f","In the Amazon basin, seasonal and interannual spectral changes measured by satellites result from anthropogenic disturbance and from the interaction between climate variation and the surface cover. Measurements of spectral change, and the characterization of that change, provide information concerning the physical processes evident at this mesoscale. A 17-yr sequence of daily Advanced Very High Resolution Radiometer (AVHRR) global area coverage (GAC) images were analyzed to produce a monthly record of surface spectral change encompassing El Niño-Southern Oscillation (ENSO) cycles. Monthly cloud-free composite images from daily AVHRR data were produced by linear filters that minimized the finescale spatial variance and allowed for a wide range analysis within a consistent mathematical framework. Here the use of a minimized local variance (MLV) filter that produced spatially smooth images in which major land-cover boundaries and spatial gradients are clearly represented is discussed. Changes in the configuration of these boundaries and the composition of the landscape elements they defined are described in terms of quantitative changes in landscape pattern. The time series produced with the MLV filter revealed a marked seasonal difference in the pattern of the landscape and structural differences over the length of the time series. Strikingly, the response of the region to drier El Nñio years appears to be delayed in the MLV series, the maximum response being in the year following El Niño with little or no change seen during El Niño. © 2010 Population Review Publications."
"6603168914;55982350900;","Challenges of water demand management in jordan",2005,"10.1080/02508060508691861","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20844453278&doi=10.1080%2f02508060508691861&partnerID=40&md5=b6a11c71226676b03a80fc0d307cc5bc","Water scarcity is considered one of the most important challenges facing Jordan because of the need to satisfy the municipal, industrial, and agricultural needs. The climate in Jordan reveals that more than 80 percent of its area receives less than 200 mm of rainfall. The water resources are divided into two main parts: conventional (surface and groundwater) and non-conventional (treated wastewater, cloud seeding and desalination of sea water, and brackish water). The major problems facing conventional water resources development are quality deterioratio and resource depletion. The non-conventional resources could increase water supply enough to overcome the shortage and to satisfy the different water needs of the country. Desalination of seawater and brackish groundwater could reduce the need for additional water supply to cover the country's water needs. The uses of water are divided among municipal, industrial, irrigation, and livestock uses. The irrigation sector consumes most of the water resources in the country, and there is a gradual decrease in the water resources for all uses. Sharing water resources is considered very important to water supplies in the present and future. The annual safe yield of groundwater is 275 million cubic meter (MCM) per year while pumping is more than 450 MCM. This increases the stress on groundwater and gives the priority to water harvesting projects in different areas to accumulate the runoff water either in pools or in desert dams for irrigation, livestock, or artificial groundwater recharge. There are more than 25 dams located in the different parts of the country with total storage of about 204 MCM. To avoid the water shortages in Jordan, it is recommended to increase water harvesting projects and reuse wastewater for irrigation purposes. © 2005, Taylor & Francis Group, LLC."
"57189998431;7003488532;8643088300;7003897194;7004510293;7004864963;","Low molecular weight organic acids in aerosol particles from Rondônia, Brazil, during the biomass-burning, transition and wet periods",2005,"10.5194/acp-5-781-2005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16444370595&doi=10.5194%2facp-5-781-2005&partnerID=40&md5=83a64c8b65d688a85151aad25d787fe7","Particles from biomass burning and regional haze were sampled in Rondônia, Brazil, during dry, transition and wet periods from September to November 2002, as part of the LBA-SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke, Aerosols, Clouds, Rainfall, and Climate) field campaign. Water soluble organic and inorganic compounds in bulk (High Volume and Stacked Filter Unit sampler) and size-resolved (Micro Orifice Uniform Deposit Impactor - MOUDI) smoke samples were determined by ion chromatography. It was found that low molecular weight polar organic acids account for a significant fraction of the water soluble organic carbon (WSOC) in biomass burning aerosols (C2-C6 dicarboxylic acids reached up to 3.7% and one-ring aromatic acids reached up to 2% of fine fraction WSOC during burning period). Short dicarboxylic (C2-C6) acids are dominated by oxalic acid followed by malonic and succinic acids. The largest ionic species is ammonium sulfate (60-70% of ionic mass). It was found that most of the ionic mass is concentrated in submicrometer-sized particles. Based on the size distribution and correlations with K+, a known biomass burning tracer, it is suggested that many of the organic acids are directly emitted by vegetation fires. Concentrations of dicarboxylic acids in the front and back filters of high volume sampler were determined. Based on these measurements, it was concluded that in the neutral or slightly basic smoke particles typical of this region, dicarboxylic acids are mostly confined to the particulate phase. Finally, it is shown that the distribution of water soluble species shifts to larger aerosols sizes as the aerosol population ages and mixes with other aerosol types in the atmosphere. © 2005 Author(s). This work is licensed under a Creative Commons License."
"16638820000;35468686100;57208765879;7004208584;56486548700;","Spatially complete global spectral surface albedos: Value-added datasets derived from terra MODIS land products",2005,"10.1109/TGRS.2004.838359","https://www.scopus.com/inward/record.uri?eid=2-s2.0-12844258939&doi=10.1109%2fTGRS.2004.838359&partnerID=40&md5=1be143b44c6176435c1237dfff6f35da","Recent production of land surface anisotropy, diffuse bihemispherical (white-sky) albedo, and direct-beam directional hemispherical (black-sky) albedo from observations acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard the National Aeronautics and Space Administration's Terra and Aqua satellite platforms have provided researchers with unprecedented spatial, spectral, and temporal information on the land surface's radiative characteristics. Cloud cover, which curtails retrievals, and the presence of ephemeral and seasonal snow limit the snow-free data to approximately half the global land surfaces on an annual equal-angle basis. This precludes the MOD43B3 albedo products from being used in some remote sensing and ground-based applications, climate models, and global change research projects. An ecosystem-dependent temporal interpolation technique is described that has been developed to fill missing or seasonally snow-covered data in the official MOD43B3 albedo product. The method imposes pixel-level and local regional ecosystem-dependent phenological behavior onto retrieved pixel temporal data in such a way as to maintain pixel-level spatial and spectral detail and integrity. The phenological curves are derived from statistics based on the MODIS MOD12Q1 IGBP land cover classification product geolocated with the MOD43B3 data. The resulting snow-free value-added products provide the scientific community with spatially and temporally complete global whiteand black-sky surface albedo maps and statistics. These products are stored on 1-min and coarser resolution equal-angle grids and are computed for the first seven MODIS wavelengths, ranging from 0.47-2.1 ̈m and for three broadband wavelengths 0.3-0.7, 0.3-5.0, and 0.7-5.0 μm."
"16430637800;6507958221;8420514500;7401806579;57201958916;57207177305;","A diagnostic study of heavy rainfall in Karachi due to merging of a mesoscale low and a diffused tropical depression during South Asian summer monsoon",2005,"10.1007/BF02918751","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20344380911&doi=10.1007%2fBF02918751&partnerID=40&md5=beda5cd5827d167431181f0354f02752","This paper presents the results of a diagnostic study of a typical case of very heavy rainfall during the South Asian summer monsoon when a mesoscale low in a desert climate merged with a diffused tropical depression. The former low was located over Pakistan's desert region and the latter depression originated over the Bay of Bengal. Surface and NCEP reanalysis data supported by satellite and radar images were incorporated in the diagnosis. The relationship between the heavy precipitation process and large-scale circulations such as monsoon trough, subtropical high, westerly jet, low level jet and water vapor transport were investigated to further understand the mechanism of this peculiar interaction. It was found that: (1) the mesoscale low developed as a result of cold air advection aloft from northern latitudes and strong convection over the region of humidity convergence on 24 July 2003 over the Indian Rajistan area. (2) On the same day, a low that formed over the Bay of Bengal was transformed into a monsoon depression and moved westward to the mesoscale low which existed over southwest India and the adjoining southeastern parts of Pakistan. (3) Initially, the mesoscale low received moisture supply from both the Bay of Bengal as well as the Arabian Sea, whereas the Bay of Bengal maintained the cont)nuous supply of moisture to the monsoon depression. (4) After the depression crossed central India, the Bay's moisture supply was cut off and the Arabian Sea became the only source of moisture to both the closely located systems. On 27 July, both of the systems merged together and the merger resulted in a heavy downpour in the Karachi metropolitan and in its surroundings. (5) With the intensification as well as the southeastward extension of the subtropical high and the shift of the monsoon trough axis from southwest-west to northeast-east, the monsoon depression moved southwestward. In this situation, there existed a very favourable condition for a merger of the two systems in the presence of cross-latitude influence. (6) A number of convective cloud clusters were developed and organized in the mesoscale low. Probably, interactions existed among the multi-scale systems."
"7006191743;57190531316;7003498065;7003495982;7006111925;56402486000;7006550762;7006224475;7202963086;35600785900;","Sensitivity of present and future surface temperatures to precipitation characteristics",2004,"10.3354/cr028053","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844253632&doi=10.3354%2fcr028053&partnerID=40&md5=9ff301bdd50746b0fd6d61e19d218d23","A model simulation study shows that different diurnal cycles of precipitation are consistent with radically different present and future climate characteristics. In projected future climate scenarios, divergence in the time of day and type of precipitation had very divergent impacts on the radiation balance and consequently on surface temperatures. The relationship between the diurnal cycle of precipitation versus the present and future climate was examined using the GISS-MM5 (Goddard Institute for Space Studies Mesoscale Model 5) regional climate modeling system with 2 alternative moist convection schemes. June-August (JJA) mean surface temperatures of the 1990s, 2050s, and 2080s were simulated over the eastern US on a double nested 108/36 km domain, with the 36 km domain centered over the eastern US. In the 1990s, one model version simulated maxima in (convective) precipitation during the early morning, while the second model simulated the hour of precipitation maxima with considerable spatial variability (in better agreement with observations). In the futuristic climate scenarios, differences in the time of day of precipitation had very important impacts on the radiation balance at the surface. One version gave more precipitation at night and fewer clouds during the day, promoting higher surface temperatures. The alternative version created more precipitation during the day, consistent with diminished absorption of solar radiation at the surface and consequently lower surface temperatures. The results demonstrate the importance of improving cumulus parameterizations in regional mesoscale and global climate models and suggest that such improvements would lead to greater confidence in model projections of climate change. © Inter-Research 2004."
"8868755900;7005052420;57203558683;","Climatic shift in patterns of shallow clouds over the Amazon",2004,"10.1029/2004GL021188","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14544280635&doi=10.1029%2f2004GL021188&partnerID=40&md5=4e775902d10c2f8268cdddc3717e13ed","The Amazon rain forest has experienced dramatic changes in the past 50 years due to active deforestation. As of 2001, 15% of the 4,000,000 km 2 Brazilian Amazon has been deforested [Instituto Nacional de Pesquisas Espaciais (INPE), 2003]; each year, agricultural exploitation claims an estimated 13,000 km2 of tropical forest [Achard et al., 2002]. In this paper we investigate the climatic effects caused by the observed change of the physical characteristics of the land surface (i.e., increased surface albedo, decreased root-zone depth, decreased surface roughness and decreased leaf-area index). More precisely, we examine the spatial correspondence of shallow cumulus clouds with deforestation. Through the creation of an 8-year record of thrice daily shallow cumulus cloud cover at 1 km resolution from multi-spectral satellite imagery, we quantitatively show the existence of a significant climatic shift in shallow cloudiness patterns associated with deforestation. This shift manifests itself as an enhancement of shallow cumuli over deforested patches, and has potentially important climatic, hydrologic and ecological implications. Copyright 2004 by the American Geophysical Union."
"16246205000;7401436524;","Underestimated tropical stratiform precipitation in the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3)",2004,"10.1029/2004GL021292","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14544292477&doi=10.1029%2f2004GL021292&partnerID=40&md5=0b7277343e58520db30df145795f92a2","The ratio between stratiform and convective precipitation simulated by the NCAR CCM3 is examined. Stratiform rain only accounts for about 1.5% of the total rain amount in CCM3 between 20°N and 20°S, far lower than 40% estimated from Tropical Rainfall Measuring Mission (TRMM) data. Preliminary study suggests that the serious underestimation of stratiform precipitation in CCM3 could be responsible for failed simulations of intraseasonal oscillation (ISO) and seasonal migration of the intertropical convergence zone (ITCZ) precipitation across the equator. Sensitivity experiment with artificially enhanced stratiform precipitation indicates that increase of stratiform rain fraction can improve the simulations of ISO and seasonal migration of the ITCZ precipitation. This study suggests that reasonable partition of stratiform and convective precipitation is crucial for a climate model to project realistic climate features. Copyright 2004 by the American Geophysical Union."
"36897470600;7004544454;","Orographic influences on the annual cycle of Namibian stratocumulus clouds",2004,"10.1029/2004GL020814","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14544287318&doi=10.1029%2f2004GL020814&partnerID=40&md5=a003b7f887717d70150bb55fe802c63f","The impact of African orography on the persistence and seasonal cycle of Namibian stratocumulus is examined in the context of an atmospheric general circulation model. A control simulation with realistic orography and simulated stratocumulus is compared to a sensitivity experiment, in which African orography is removed. In the absence of orography, stratocumulus incidence off the Namibian and Angolan coast is significantly reduced during austral winter and spring. It is argued that through the combined effects of obstruction and deflection of atmospheric flow, orography acts to enhance static stability of the lower troposphere over the Atlantic off the Namibian coast, which provides an environment conducive to the development of stratocumulus in that region. Copyright 2004 by the American Geophysical Union."
"55456111900;6603631763;6603025800;","Comparison of NOAA's operational AVHRR-derived cloud amount to other satellite-derived cloud climatologies",2004,"10.1175/JCLI-3242.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-12344275808&doi=10.1175%2fJCLI-3242.1&partnerID=40&md5=1b0cefc2436e38a9c430df7744396170","A comparison is made between a new operational NOAA Advanced Very High Resolution Radiometer (AVHRR) global cloud amount product to those from established satellite-derived cloud climatologies. The new operational NOAA AVHRR cloud amount is derived using the cloud detection scheme in the extended Clouds from AVHRR (CLAVR-x) system. The cloud mask within CLAVR-x is a replacement for the Clouds from AVHRR phase 1 (CLAVR-1) cloud mask. Previous analysis of the CLAVR-1 cloud climatologies reveals that its utility for climate studies is reduced by poor high-latitude performance and the inability to include data from the morning orbiting satellites. This study demonstrates, through comparison with established satellite-derived cloud climatologies, the ability of CLAVR-x to overcome the two main shortcomings of the CLAVR-1-derived cloud climatologies. While systematic differences remain in the cloud amounts from CLAVR-x and other climatologies, no evidence is seen that these differences represent a failure of the CLAVR-x cloud detection scheme. Comparisons for July 1995 and January 1996 indicate that for most latitude zones, CLAVR-x produces less cloud than the International Satellite Cloud Climatology Project (ISCCP) and the University of Wisconsin High Resolution Infrared Radiation Sounder (UW HIRS). Comparisons to the Moderate Resolution Imaging Spectroradiometer (MODIS) for 1-8 April 2003 also reveal that CLAVR-x tends to produce less cloud. Comparison of the seasonal cycle (July-January) of cloud difference with ISCCP however, indicates close agreement. It is argued that these differences may be due to the methodology used to construct a cloud amount from the individual pixel-level cloud detection results. Overall, the global cloud amounts from CLAVR-x appear to be an improvement over those from CLAVR-1 and compare well to those from established satellite cloud climatologies. The CLAVR-x cloud detection results have been operational since late 2003 and are available in real time from NOAA. © 2004 American Meteorological Society."
"7202330299;7103313899;7202444684;16555441300;","Solar radiation budget from the MRI radiometers for clear and cloudy air columns within ARESE II",2004,"10.1175/JAS-3288.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-12144267864&doi=10.1175%2fJAS-3288.1&partnerID=40&md5=0ed74e9787d16adf13f551f21b54900d","As an international collaborative research activity within the Japanese Cloud-Climate Study (JACCS) program, the authors participated in the second Atmospheric Radiation Measurement (ARM) Enhanced Shortwave Experiment (ARESE II) using the Meteorological Research Institute (MRI) radiometers. This paper describes results of ARESE II, as well as specifications and calibration of the MRI radiometers. The solar radiation budget for 2 days of typical clear sky (27 February and 20 March 2000) and overcast sky (3 and 21 March 2000) has been analyzed using spatially collocated, total-band solar irradiances measured by the MRI pyranometers (Kipp & Zonen CM21). These were installed on a Twin Otter aircraft, and deployed at the ARM Southern Great Planes Central Facility site. On average, the clear-sky and overcast-sky air columns between the surface and the Twin Otter flight level of 7 km absorbed about 13% ± 2% ± and 20% ± 3%, respectively, of the total-band solar radiation incident on the column top. The measured solar radiation budgets agree well with those computed for models of clear and cloudy atmospheres. The present results indicate no evidence of anomalous solar absorption for either the clear- or cloudy-sky cases. It is suggested that about half of the observed absorption enhancement of 7% for the overcast-sky cases could be caused by the presence of larger water vapor, compared with the clear-sky cases, and that the other half could be caused by increased absorption within and above the rather low cloud layers. © 2004 American Meteorological Society."
"57218978870;9939102400;7003922138;7102665209;6701379896;7102620639;7103271625;7004343004;6603396333;7103242280;6506103893;7401477391;7005808242;6701618837;7103206141;7402064802;7003554208;7006735547;16637634600;7005350396;8733578200;7005884486;7006003831;7103033590;6603173671;56744278700;35514163500;8733579000;6508004743;7003543851;7103366892;55419119900;57199296506;6602864692;8733579800;","The new GFDL global atmosphere and land model AM2-LM2: Evaluation with prescribed SST simulations",2004,"10.1175/JCLI-3223.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-19944434306&doi=10.1175%2fJCLI-3223.1&partnerID=40&md5=bec7e20dbfff91e14f99f8c8e19974fd","The configuration and performance of a new global atmosphere and land model for climate research developed at the Geophysical Fluid Dynamics Laboratory (GFDL) are presented. The atmosphere model, known as AM2, includes a new gridpoint dynamical core, a prognostic cloud scheme, and a multispecies aerosol climatology, as well as components from previous models used at GFDL. The land model, known as LM2, includes soil sensible and latent heat storage, groundwater storage, and stomatal resistance. The performance of the coupled model AM2-LM2 is evaluated with a series of prescribed sea surface temperature (SST) simulations. Particular focus is given to the model's climatology and the characteristics of interannual variability related to El Niño-Southern Oscillation (ENSO). One AM2-LM2 integration was perfor med according to the prescriptions of the second Atmospheric Model Intercomparison Project (AMIP II) and data were submitted to the Program for Climate Model Diagnosis and Intercomparison (PCMDI). Particular strengths of AM2-LM2, as judged by comparison to other models participating in AMIP II, include its circulation and distributions of precipitation. Prominent problems of AM2-LM2 include a cold bias to surface and tropospheric temperatures, weak tropical cyclone activity, and weak tropical intraseasonal activity associated with the Madden-Julian oscillation. An ensemble of 10 AM2-LM 2 integrations with observed SSTs for the second half of the twentieth century permits a statistically reliable assessment of the model's response to ENSO. In general, AM2-LM2 produces a realistic simulation of the anomalies in tropical precipitation and extratropical circulation that are associated with ENSO. © 2004 American Meteorological Society."
"55717244800;7003833060;6602407091;","A new heuristic lagrangian marine boundary layer cloud model",2004,"10.1175/JAS-3344.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-12144271629&doi=10.1175%2fJAS-3344.1&partnerID=40&md5=d5fc103cb735c71d43fd3f72a3b34659","A new heuristic model of stratocumulus cloudiness in the inversion-capped marine boundary layer is developed and tested. The essential ingredient is a new method for predicting the statistical distribution of temperature and specific humidity at the inversion base under partially decoupled conditions along steady-state marine boundary layer (MBL) trajectories. MBL decoupling is parameterized as an increasing function of the height difference between the inversion base and lifting condensation level (LCL) of the mixed-layer air. Required inputs are sea surface temperature (SST), free air (above inversion) temperature and humidity, subsidence velocity, and mean boundary layer wind speed. Upstream boundary conditions must also be specified but have little influence at sufficient downstream distances (>2000 km). The model is applied to the cold advection regime of the northeastern subtropical Pacific and to both warm and cold advection regimes of the eastern equatorial Pacific Ocean. The model is conceptually simple and avoids explicit calculation of several important physical processes. Nevertheless, it is at least qualitatively successful in predicting both the climatological mean properties and climate anomaly variations of MBL stratocumulus in both regions. These results suggest that, regardless of other properties, successful MBL stratocumulus models will need to accurately predict inversion base height and the LCL and they will have to account for downstream memory effects. © 2004 American Meteorological Society."
"6701522828;","Climate variability over the tropical Indian ocean sector in the NSIPP seasonal forecast system",2004,"10.1175/JCLI-3239.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-12344277914&doi=10.1175%2fJCLI-3239.1&partnerID=40&md5=6e8e45828cf1780d1f7c120db3a35de0","Prospects for forecasting Indian dipole mode (IDM) events with lead times of a season or more are examined using the NASA Seasonal-to-Interannual Prediction Project (NSIPP) coupled-model forecast system. The mean climatology of the system over the sector is reasonable, as determined from an almost-century-long run without data assimilation. However, the system presents biases, for example, too cool sea surface temperatures (SSTs), too shallow thermocline, and too strong southeasterlies along the Sumatra-Java coast in the east, and too warm SSTs, too deep thermocline, and too weak extension of the southeast trades into the Findlater jet in the west. These suggest coupling between the ocean and atmosphere is stronger, and the SST-clouds-shortwave radiation negative feedback less effective, than observed in the east with the opposite holding true in the west. Also, the negative zonal gradient in SST in the eastern equatorial basin, in contrast with the positive observed, suggests that equatorial Kelvin and Rossby coupled modes may have a different character from observed. Biases identified in the seasonal cycle, which may affect the strength and timing of IDM events, include a delayed onset of the boreal summer monsoon in the west, and a prolonged boreal summer monsoon in the east. Eight major positive IDM events occur during the almost-century-long run over a range of El Niño-Southern Oscillation phases with a tendency to occur post-El Niño/pre-La Niña. Consistent with the identified air-sea interaction biases, the cold (warm) anomaly at the east (west) pole tends to be stronger (weaker) than observed. Also, the cold anomaly extends much farther westward and is more equatorially trapped than observed; its slow westward propagation and the structure of the associated fields is reminiscent of an unstable, coupled Rossby mode with SST governed by lateral advection due to the westward displacement of the convective anomaly from the heat source. Otherwise, the life cycle of the eight-event composite is similar in seasonal phase locking and mechanisms of evolution and decay to the canonical event. For the decade from 1993 to the present, there were major positive IDM events in 1994 and 1997/98. Monthly mean SST anomalies over the western pole are well hindcast by the ocean component of the NSIPP system forced by observed surface fluxes with SST damped to observed values, and in which subsurface temperature data available in real time are assimilated; these data are very sparse over the Indian Ocean. Over the eastern pole, the SST anomalies are well hindcast except for the 1997/98 event, when it is too cool. The ensemble mean hindcast of the zonal surface wind anomaly of the central basin by the atmosphere component of the NSIPP system forced by observed SST is too weak during both events. These hindcasts provide initial conditions for the coupled system forecasts. Forecast ensembles for the decade 1993 onward, generated by the coupled system, give monthly mean SST anomalies averaged over the east and west poles of the IDM in agreement with observations at lead times of three months. The cool anomaly at the eastern pole is slightly too large in 1997/98, and the onset of the warm anomaly in 1997 is delayed by a month or so; its peak and decay are correctly timed. At lead times of six months, there is a significant deterioration in the forecast at the eastern pole with either false positive or negative alarms generated annually in boreal fall; that at the western pole remains good. These results are very encouraging and suggest that major IDM events have the potential to be forecast a season or more in advance. © 2004 American Meteorological Society."
"56316474800;7004940109;35857960400;6701427386;","Modelling the effect of an assumed cosmic ray-modulated global cloud cover on the terrestrial surface temperature",2004,"10.1016/j.jastp.2003.12.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10144260058&doi=10.1016%2fj.jastp.2003.12.003&partnerID=40&md5=84d1a07a2aa4c4b6664c595b11533da6","We have used the thermodynamic model of the climate to estimate the effect of variations in the oceanic cloud cover on the surface temperature of the Earth in the North Hemisphere (NH) during the period 1984-1990. We assume that the variations in the cloud cover are proportional to the variation of the cosmic ray flux measured during the same period. The results indicate that the effect in the temperature is slightly noticeable when we consider the surface hemispheric temperature on July 1987, finding an average temperature anomaly between -0.06°C and -0.14°C, along a latitudinal band between 20° and 40°. The surface temperature averaged globally in the NH presents a decrease of ∼0.01°C in average, which is almost the same for continents and oceans. However, these values are not significant when compared to the overall variability of the time series with and without forcing. © 2003 Published by Elsevier Ltd."
"55887849100;7201551011;7202076777;","The possible connection between ionization in the atmosphere by cosmic rays and low level clouds",2004,"10.1016/j.jastp.2004.07.041","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10144221373&doi=10.1016%2fj.jastp.2004.07.041&partnerID=40&md5=2f15bbfa43ce8ebe03e115c0ecd2535a","Recent analysis of monthly mean cloud data from the International Satellite Cloud Climatology Project uncovered a strong correlation between low cloud and the cosmic ray flux for extensive regions of the Earth. Additional data have been recently released covering the period up to September 2001 with which we have made a new study of the geographical variation of the correlation between low cloud and predicted ionization level from cosmic rays at an altitude of 2 km. When analysed globally, we find that the correlations do not correspond to the latitude variation of cosmic ray flux and they are not field significant. Nonetheless they appear to be marginally field significant over broad latitude and longitude bands with a peak positive correlation at 50 degrees North and South and a tendency to negative correlation at lower latitudes. The correlation is strongest over the North and South Atlantic. Several of these features are consistent with the predictions of the electroscavenging process. We use a simple model to calculate the climatic impact should the correlation be confirmed. We show that, under the most favorable conditions, a reduction in low cloud cover since the late 19th century, combined with the direct forcing by solar irradiance can explain a significant part of the global warming over the past century, but not all. However, this computation assumes that there is no feedback or changes in cloud at other levels. © 2004 Elsevier Ltd. All rights reserved."
"7202048112;7202152636;55802246600;35187572900;","Evaluation of regional climate simulations of the 1998 and 1999 East Asian summer monsoon using the GAME/HUBEX observational data",2004,"10.2151/jmsj.82.1695","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844253667&doi=10.2151%2fjmsj.82.1695&partnerID=40&md5=615b1a4a5d61c6c41211263b78ca7fa8","A regional climate model based on the Penn State/NCAR Mesoscale Model (MM5) was used to simulate the 1998 and 1999 East Asian summer monsoon conditions. Simulations were performed for 1 April-31 August of each year, with initial and lateral boundary conditions provided by the ECMWF analysis. Observations from the 1998 and 1999 GAME/HUBEX experiments were used to evaluate the regional climate simulations. Based on observations, large differences can be found between the 1998 and 1999 meteorological conditions and surface energy budgets at the Shouxian station during the IOPs, with much higher rain intensity but only slightly higher rain frequency in 1998 than 1999. For 1998, although the regional climate model was able to reproduce the general spatial distribution of monthly mean rainfall quite well during the summer monsoon season, large discrepancies can be found in comparing the observed and simulated surface climate and energy fluxes in the HUBEX region. By using Four Dimensional Data Assimilation (FDDA) technique, which constrains the simulated large-scale circulation with observations from 21 soundings in the HUBEX α-scale region, both the root mean square error and mean bias in rainfall were greatly reduced. The improvements in simulating rainfall were related to both reduction in errors of precipitation amount and timing. In the control simulation, a mean bias of -63 W/M2 (-36%) was found in the simulated surface net radiation at Shouxian, which suggest large errors in simulating clouds in the region. With FDDA, the bias was significantly reduced to -23 W/ m2 (-13%), with corresponding reduction of bias in the latent heat flux. This suggests that at least part of the model bias in simulating net radiation is related to errors in simulating the large-scale circulation, which can affect cloud amount and vertical distribution. Comparing the 1998 and 1999 simulations, both without FDDA, smaller biases were found in the surface fluxes during 1999. Percentage biases in the net radiation and latent heat flux were -18% and -33% in 1999 and -36% and -50% in 1998 respectively. Based on observations, large differences in the net surface radiation, and small differences in cloud fraction between the two years suggest that cloud optical depth and/or vertical distribution were very different, with more cloudy conditions observed during 1999. Although the 1999 simulations were sensitive to the cumulus convective parameterizations (Grell scheme versus Kain-Fritsch scheme) as shown by the sensitivity experiments, the large differences in simulation skill between the 1998 and 1999 cases, regardless of the convection schemes used, suggest possible dependence of model errors on cloud properties that deserve further investigations. © 2004, Meteorological Society of Japan."
"7005902717;55165863400;","Factors that inhibit snowball Earth simulation",2004,"10.1029/2004PA001056","https://www.scopus.com/inward/record.uri?eid=2-s2.0-15944376596&doi=10.1029%2f2004PA001056&partnerID=40&md5=b4f5c33aea9f8bc6f90de15a71badd80","A coupled ocean-atmosphere general circulation model with a thermodynamic sea-ice model, the Fast Ocean Atmosphere Model version 1.5, is used to investigate the factors that inhibit the simulation of global sea ice. In the control experiment with reduced solar luminosity (93% of modern), low atmospheric pCO2 (140 ppm), and an idealized tropical continent, the sea-ice margin equilibrates at ∼27° latitude. A series of experiments was completed to systematically test the influence of deep-ocean circulation, wind-driven ocean circulation, convective mixing, sea-ice treatment, and radiative-cloud forcing, on the sea-ice extent. Model results indicate that both wind-driven circulation and cloud-radiative forcing are critical factors that inhibit sea-ice advance into the low latitudes. The wind-driven ocean circulation transports heat to the sea-ice margin, stabilizing the sea-ice margin. Clouds yield a positive radiative forcing over ice, warming the air overlying sea ice and decreasing sensible heat loss at the sea-ice margin. In the absence of either factor, sea ice expands to the equator within 15 model years, yielding a snowball Earth. We also find that intensification of the Hadley circulation as sea ice enters the Hadley domain promotes the climate instability that leads to global sea-ice cover. Results from this study help explain the wide disparity in conditions necessary to simulate global ice cover in previous climate models of the Neoproterozoic. Copyright 2004 by the American Geophysical Union."
"57204987677;7005631653;","Mortality in England during the 1783-4 Laki Craters eruption",2004,"10.1007/s00445-004-0357-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10444261982&doi=10.1007%2fs00445-004-0357-7&partnerID=40&md5=79b6968056ff76b39d2ce50780433e3d","1783/4 has been recognised as a mortality ""crisis year"" in the population history of England. This demographic incident coincides with the Laki Craters eruption, Iceland, which began in June 1783 and fumigated many parts of Europe with volcanic gases and particles. Many reports and proxy climate records implicate the volcanic cloud in meteorological anomalies, including notably hot 1783 summer conditions in England and a severe subsequent winter. We present here a detailed analysis of the geographical and temporal trends in English mortality data, and interpret them in the light of the climatological records and observations of the pollutant cloud. We show that there were two distinct crisis periods: in August-September 1783, and January-February 1784, which together accounted for ∼20,000 extra deaths. In both cases, the East of England was the worst affected region. Possible causes for the two crisis periods are considered and we conclude that the timing and magnitude of the winter mortality peak can be explained by the severe cold of January 1784. The late summer mortality followed 1-2 months after the very hot July of 1783 and may also have been related to the weather, with the time lag reflecting the relatively slow spread of enteric disease or the contraction of malaria. However, it is hard to explain the entire late summer anomaly by these high temperature causes. We therefore consider that fine acid aerosol and/or gases in the volcanic haze may also have contributed to the unusual August-September mortality. Given that complex radiative and dynamical effects of the volcanic cloud are implicated in the climatic anomalies in 1783-4, it is likely that the Laki Craters eruption did play a role in the English mortality crises of the same period. © Springer-Verlag 2004."
"6602237128;57204299664;35594051500;7404959038;","Coastal pollution hazards in southern California observed by SAR imagery: Stormwater plumes, wastewater plumes, and natural hydrocarbon seeps",2004,"10.1016/j.marpolbul.2004.07.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8844269068&doi=10.1016%2fj.marpolbul.2004.07.016&partnerID=40&md5=5290e8a825109f9b77ec889e0e1f9161","Stormwater runoff plumes, municipal wastewater plumes, and natural hydrocarbon seeps are important pollution hazards for the heavily populated Southern California Bight (SCB). Due to their small size, dynamic and episodic nature, these hazards are difficult to sample adequately using traditional in situ oceanographic methods. Complex coastal circulation and persistent cloud cover can further complicate detection and monitoring of these hazards. We use imagery from space-borne synthetic aperture radar (SAR), complemented by field measurements, to examine these hazards in the SCB. The hazards are detectable in SAR imagery because they deposit surfactants on the sea surface, smoothing capillary and small gravity waves to produce areas of reduced backscatter compared with the surrounding ocean. We suggest that high-resolution SAR, which obtains useful data regardless of darkness or cloud cover, could be an important observational tool for assessment and monitoring of coastal marine pollution hazards in the SCB and other urbanized coastal regions. © 2004 Elsevier Ltd. All rights reserved."
"7102848501;7005851232;","Atmospheric chemistry in the coastal ocean: A synopsis of processing, scavenging and inputs",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-23044442123&partnerID=40&md5=549f3fcbf36a51197c34a441061da36f","The coastal atmosphere provides a complicated chemical environment that can have global implications for climate. For example, the continents transport an array of gases and aerosols, both natural dusts and pollutant species, which can interact with sea-salt and affect coastal clouds and their processing for deposition. Once over the coastal ocean, different mixtures of acids, bases, minerals, sea-salt and water under different solar irradiation can induce a host of heterochemical chemical reactions. Deposition of the products of these reactions can make a significant contribution of nutrient inputs to coastal waters and impact coastal ecosystems. However, the steep gradients and complex physical and chemical processes occurring in this transitional area between terrestrial and marine atmospheric domains complicate the quantification of these inputs. This synopsis considers a group of key processes such as interaction of climatic aerosols that operate to regulate atmospheric scavenging and deposition to the coastal environment."
"55463815300;13406672500;","Aerosol loading over the Indian Ocean and its possible impact on regional climate",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-17444372676&partnerID=40&md5=c8bb9d972bbe4ad0e95039545123e8f0","This paper provides a review of aerosol forcing results from the Indian Ocean Experiment (INDOEX) and also summarizes the follow-on modeling studies that examine the impact of the haze on regional climate. Every dry season from November to May, anthropogenic haze spreads over most of the northern Indian Ocean, and South and Southeast Asia. The INDOEX documented this Indo-Asian haze at various scales during 1995-2001. The haze particles consisted of several inorganic and carbonaceous species, including absorbing black carbon clusters, fly ash and mineral dust. Becauseof black carbon contributing as much as about 14% to the fine particle mass, the single-scattering albedo estimated by several independent methods was consistently around 0.9 both inland and over the open ocean. Anthropogenic sources contributed as much as 75% (±10%) to the aerosol loading and the optical depth. The regional aerosol forcing resulting from the direct and indirect effects was derived by integrating the multi-platform observations of satellites, aircraft, ships, surface stations and balloons with 1- and 4-D models. The haze layer reduces the net solar flux at the surface by as much as 20 to 40 Wm-2on a monthly mean basis and heats the lowest 3 km atmosphere by as much as 0.4 to 0.8 K/day, which enhances the solar heating of this layer by 50 to 100%. The INDOEX also documented year-to-year fluctuations of the haze forcing. For instance, the southernmost extent of the haze varied from about 10°S to about 5°N. In assessing the haze impacts on the cold dry-season regional climate, we conducted two CCM3 experiments with two extreme locations of the forcing: 1) extended haze forcing (EHF) and 2) shrunk haze forcing (SHF). Over India where the forcing is centered, the simulated climate changes are very similar between EHF and SHF. The most important effect of the haze is a surface cooling, and a strengthening of the inversion in the lower troposphere. The surface cooling has been confirmed by observations. The stabilization of the boundary layer results in a reduction of evaporation and sensible heat flux from the land. Rainfall patterns get substantially disrupted in local and remote regions, with the disruption being very sensitive to the southern extent of the imposed haze forcing. Both forcings lead to global circulation/precipitation perturbations; and the EHF produces about an order of magnitude larger responses. One key remote response to the haze is the suppression of convection in the western equatorial Pacific, which has implications for ENSO variability. Since the western Pacific convection suppression would weaken the trade winds over the Pacific and induce warm anomalies in the eastern basin, we speculate that the Great Indo-Asian haze might have an important role in the amplitude and frequency of El Nio events during the recent decades. The haze-ENSO connection is further demonstrated by the Cane-Zebiak Pacific Ocean/atmosphere model. The focus of the studies thus far has been on the dry season (November to May) aerosols. The role of anthropogenic aerosols during the wet season from June to September is to be explored."
"7004858790;7006518289;6701508272;","A decadal solar effect in the tropics in July-August",2004,"10.1016/j.jastp.2004.06.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10144250345&doi=10.1016%2fj.jastp.2004.06.003&partnerID=40&md5=a938a44c69e0b6e6391d11bfd44f5529","The availability of global gridded precipitation and outgoing long-wave radiation (OLR) data after 1978 makes possible an investigation of the influence of the decadal solar oscillation in the tropics during three solar maxima and two solar minima. The NCEP/NCAR reanalyses starting in the 1950s allows the inclusion of an additional two solar maxima and minima to look for consistency of response across a longer time period. In the northern summer (July-August), the major climatological tropical precipitation maxima are intensified in solar maxima compared to solar minima during the period 1979-2002. The regions of this enhanced climatological precipitation extend from the Indian monsoon to the West Pacific oceanic warm pool and farther eastwards in the Intertropical Convergence Zone of the North Pacific and North American Monsoon, to the tropical Atlantic and greater rainfall over the Sahel and central Africa. The differences between solar maxima and minima in the zonal mean temperature through the depth of the troposphere, OLR, tropospheric vertical motion, and tropopause temperature are consistent with the differences in the rainfall. The upward vertical motion is stronger in regions of enhanced tropical precipitation, tropospheric temperatures are higher, tropopause temperatures are lower, and the OLR is reduced due to higher, colder cloud tops over the areas of deeper convective rainfall in the solar maxima than in the minima. These differences between the extremes of the solar cycle suggest that an increase in solar forcing intensifies the Hadley and Walker circulations, with greater solar forcing resulting in strengthened regional climatological tropical precipitation regimes. These effects are as strong or even more pronounced when warm and cold extremes in the Southern Oscillation are removed from the analyses. Additionally, lower stratospheric temperatures and geopotential heights are higher with greater solar forcing suggesting ozone interactions with solar forcing in the upper stratosphere. © 2004 Elsevier Ltd. All rights reserved."
"6602548091;7003628742;","Sunshine duration and daily courses of illuminance in Bratislava",2004,"10.1002/joc.1109","https://www.scopus.com/inward/record.uri?eid=2-s2.0-9744244280&doi=10.1002%2fjoc.1109&partnerID=40&md5=49ac86f6ecf89d5c959863bdf3c60a50","The occurrences of typical sky conditions during overcast days are close to the CIE Overcast Sky Standard in the Bratislava area; their variation is specified by the diffuse coefficient kdd = Dv /Ev where Dv is the horizontal diffuse illuminance and Ev is the extraterrestrial illuminance. Luminance distributions on cloudless days are close to the CIE Clear Sky Standard. Complex daylight conditions can be expected during cloudy days when moving clouds cause frequent sun disk shading with abrupt changes in illuminance levels. Since sunshine duration is one of the basic climatic parameters that describes sunny situations, the present study attempts to investigate its relation to daily illuminance levels. However, the average daily value of sunshine duration does not exactly correspond to the same illuminance course, as it depends on the temporal distribution of sunny periods within the day. Anyhow, the estimation of daytime illuminance levels is mainly influenced by the presence or absence of sunshine with frequent sky luminance patterns. Copyright © 2004 Royal Meteorological Society."
"55905970100;7801344746;","Greenhouse forcing outweighs decreasing solar radiation driving rapid temperature rise over land",2004,"10.1029/2004GL020937","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14044253377&doi=10.1029%2f2004GL020937&partnerID=40&md5=96f9e89c50ee8636766eb7adf28451e9","Since 1988, surface temperature over land in Europe increased three times faster than the northern hemisphere average. Here we contrast surface climatic and radiative parameters measured in central Europe over different time periods, including the extreme summer 2003, to pinpoint the role of individual radiative forcings in temperature increases. Interestingly, surface solar radiation rather decreases since 1981. Also, on an annual basis no net radiative cooling or warming is observed under changing cloud amounts. However, high correlation (rT = 0.86) to increasing temperature is found with total heating radiation at the surface, and very high correlation (rT = 0.98) with cloud-free longwave downward radiation. Preponderance of longwave downward radiative forcing suggests rapidly increasing greenhouse warming, which outweighs the decreasing solar radiation measured at the surface and drives rapid temperature increases over land. Copyright 2004 by the American Geophysical Union."
"7403625607;6701859365;24322892500;6602188216;","A parameterization of ocean surface albedo",2004,"10.1029/2004GL021180","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14044279741&doi=10.1029%2f2004GL021180&partnerID=40&md5=7e130eef7021ae2164ac0938c0fcecfd","Measurements at a sea platform show that the ocean surface albedo is highly variable and is sensitive to four physical parameters: solar zenith angle, wind speed, transmission by atmospheric cloud/aerosol, and ocean chlorophyll concentration. Using a validated coupled ocean-atmosphere radiative transfer model, an ocean albedo look up table is created in terms of these four important parameters. A code to read the table is also provided; it gives spectral albedos for a range of oceanic and atmospheric conditions specified by the user. The result is a fast and accurate parameterization of ocean surface albedo for radiative transfer and climate modeling. Copyright 2004 by the American Geophysical Union."
"6603431534;22975069200;7005035762;35276210200;7202625046;","Observations of marine stratocumulus in SE Pacific during the PACS 2003 cruise",2004,"10.1029/2004GL020751","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14044271982&doi=10.1029%2f2004GL020751&partnerID=40&md5=82ff3cef519d6d9a49839748e4cbb247","In November 2003, the NOAA Environmental Technology Laboratory (ETL) conducted measurements of Marine Boundary Layer (MBL) stratocumulus clouds, thermodynamic structure, surface fluxes and meteorology in the southeastern Pacific stratocumulus region. The observations were part of a field program to replace the WHOI Ocean Reference Station buoy at 20 S Latitude 85 W Longitude. During the cruise the MBL structure was characterized by a strong capping inversion, periods with well mixed conditions and marine stratus, clear sky periods and periods with moderate vertical gradients of potential temperature and mixing ratio that overlap with periods of small cloud fractional coverage, decoupled layers and low cloud base shallow cumuli clouds. The lifting condensation level (LCL) showed strong variability consistent with the variability of the MBL. Clouds with thickness more that 250 in had drizzle below the cloud base especially during nighttime. Large periods of clear skies were observed at the buoy location, especially just after the solar flux maximum. The aerosol size distribution measurements generally exhibited a bimodal structure. However, abrupt changes in the aerosol size distribution were also recorded, corresponding either with the presence of drizzle (and a depletion of the accumulation mode) or the presence of clear skies (and an increase in the Aitken mode). The stratocumulus observed during the 5-day station at the buoy location revealed a far more complex picture from the one captured during the East Pacific Investigation of Climate (EPIC) cruise to this same location in 2001. Copyright 2004 by the American Geophysical Union."
"8309699900;6701378450;6505919411;","Chemical and dynamical effects on cloud droplet number: Implications for estimates of the aerosol indirect effect",2004,"10.1029/2004JD004596","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14344262447&doi=10.1029%2f2004JD004596&partnerID=40&md5=d348a8a766d9d2f7c67ff511fe8f2323","Most aerosol-cloud-climate assessment studies use empirical aerosol number/droplet number relationships, which are subject to large variability. Historically, this variability has been attributed to unresolved variations in updraft velocity. We revisit this postulation and assess the effects of both updraft velocity and chemical composition on this variability. In doing so we utilize an inverse modeling approach. Using a detailed numerical cloud parcel model and published aerosol characteristics, with published correlations of cloud droplet versus sulfate and cloud droplet versus aerosol number as constraints, we determine a most probable size distribution and updraft velocity for polluted and clean conditions of cloud formation. A sensitivity analysis is then performed to study the variation in cloud droplet number with changes in aerosol chemistry and updraft velocities. This addresses the need to estimate the importance of chemical effects on spatial scales relevant for global climate models. Our analysis suggests that the effect of organic surfactants can introduce as much variability in cloud droplet number as the effect of expected variations in updraft velocity. In addition, the presence of organics seems to further enhance the sensitivity of droplet concentration to vertical velocity variability. The variability from organic surfactants is seen to be insensitive to variations in aerosol number concentration, implying that such effects can affect cloud droplet number consistently over large spatial scales. Our findings suggest that organics can be as important to the aerosol indirect effect as the effect of unresolved cloud dynamics, and they illustrate the potential and complex role of chemical effects on aerosol-cloud interactions. Copyright 2004 by the American Geophysical Union."
"7004159166;7801632012;","A model study of the influence of aerosol size and chemical properties on precipitation formation in warm clouds",2004,"10.1029/2004JD004779","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14344256392&doi=10.1029%2f2004JD004779&partnerID=40&md5=dfefc86c6d99cc252a135052b6504412","We present simulations of size-resolved cloud drop activation, condensational growth, and collision/coalescence performed with a cloud microphysics parcel model. The study investigates the efficiency of precipitation formation in a warm cumulus cloud with emphasis on the timescale of precipitation formation and on the amount of precipitation produced and examines the response of these parameters to modifications of aerosol size and chemical properties at different updraft velocities. Both parameters affect the lifetime of a cloud, but it depends on environmental conditions whether their responses have similar or opposite influences. In relatively clean clouds (with a cloud drop number concentration below ∼200 cm-3) the growth rate of precipitation drops and the precipitation water content decrease with increasing aerosol abundance, whereas in more polluted clouds (∼400 cm-3 and more) precipitation formation is delayed, but the amount of precipitation increases. Precipitation formation depends in a complex way on the updraft speed, especially in polluted clouds that are characterized by a relatively dispersed drop size distribution. In clouds with updraft speeds between 20 and 50 cm/s, an increase of the aerosol abundance causes a slight suppression of the growth of precipitation drops, but this effect is more pronounced in clouds with smaller or larger updraft speeds. The results suggest that global aerosol-climate models may simulate the second indirect effect more consistently when the dispersion of the drop size distribution is accounted for. Copyright 2004 by the American Geophysical Union."
"6603941796;","Optimized stomatal conductance of vegetated land surfaces and its effects on simulated productivity and climate",2004,"10.1029/2004GL020769","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13244279427&doi=10.1029%2f2004GL020769&partnerID=40&md5=43d7eee0d53d963ce33d58c78e755757","The stomatal conductance of terrestrial vegetation affects the exchange fluxes of water and carbon at the land surface. Here, a dynamic vegetation model coupled to a climate model of intermediate complexity is used to demonstrate that an optimum stomatal conductance exists at which the rate of photosynthesis, and therefore vegetation productivity, is at a maximum. This maximum originates from two competing drivers that affect the rate of photosynthesis: (i) increased supply of atmospheric carbon dioxide with increased stomatal conductance and (ii) increased cloud cover, which reduces the supply of sunlight. The simulated climate with optimized stomatal conductance is close to the model's control simulation, but vegetation productivity is substantially enhanced. The existence of this optimum has potentially important implications for the adaptation of terrestrial productivity to different climates. If vegetation maintains this optimum not only in the present-day, but also adapts to it during past (and future) climates, not considering this optimum and how it changes leads to a general underestimation of terrestrial productivity under different climates. Copyright 2004 by the American Geophysical Union."
"57212781009;","On the structure of water vapour feedbacks in climate models",2004,"10.1029/2004GL020708","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13244289819&doi=10.1029%2f2004GL020708&partnerID=40&md5=c6f8c29dbb3fdf4c1b5613e34a73f4bc","This paper quantifies the structure of water vapour feedback in a model by evaluating its meridional and vertical distribution and decomposing it into conceptually simplified components. First is a division into changes from fixed and varying relative humidity (RH). The first term is further divided into responses associated with the global mean surface temperature change, changes in horizontal gradients, and changes to the lapse rate. The uniform global temperature change component explains the majority of water vapour feedback. The horizontal gradient and varying RH terms are small. The component of water vapour feedback associated with lapse rate changes makes a significant contribution to the global water vapour feedback. However, there is a roughly equal and opposite temperature feedback from the lapse rate changes themselves. These results suggest both a very simple conceptual model for the bulk of the global water vapour feedback, as well as a relative insensitivity of combined temperature and water vapour feedbacks to the details of lapse rate changes. The effect of clouds on all feedback contributions is also quantified. Copyright 2004 by the American Geophysical Union."
"7003333942;7102636922;","On the influence of land cover on early Holocene climate in northern latitudes",2004,"10.1029/2003JD004213","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13244286685&doi=10.1029%2f2003JD004213&partnerID=40&md5=7ddcab8a9ff90926558437888be6c7fe","This study presents a factorial experimental strategy for assessing the effects of the changing land surface on early Holocene (∼11 ka) climate in Beringia. The strategy uses a coupled land-atmosphere single column model in a series of perturbation experiments that vary the vegetation type, lake cover, and soil specification simultaneously. Two sites and eight years of model forcing are chosen to determine the importance of differing terrestrial histories, local climate, and interannual variability. Eastern Beringia is represented by Fairbanks, Alaska, and western Beringia is represented by Elikchan Lake, Siberia. Evaluations of model response are performed using metrics important for vegetation growth, such as growing degree days and moisture availability. For both sites, large-scale interannual variability has a greater impact on the local climate than changes in the land surface specification for temperature-based responses, but not for moisture availability. Of the three land surface parameters tested, vegetation type is most influential. Vegetation transitions from tundra to boreal forest leads to increased precipitation, winter snow depth, and low cloud, leading to a delayed snowmelt in forested regions. This is in contrast to expectations based on albedo arguments alone. In western Beringia, a positive feedback is suggested in warming due to the presence of boreal forest, consistent with some observations that Siberian deciduous forest persisted longer than Alaskan deciduous forest in the context of large-scale cooling of the climate. The reverse was found to be true in eastern Beringia, where deciduous forests exhibited a cooling effect due to increases in albedo. The response to soil variations was relatively small, but the inclusion of inland lakes tends in general to cool the surface, although in some years a warning is evident due to the surface energy balance shifting in favor of downwelling longwave heating over evaporative cooling. Copyright 2004 by the American Geophysical Union."
"55113736500;","Climate response of fossil fuel and biofuel soot, accounting for soot's feedback to snow and sea ice albedo and emissivity",2004,"10.1029/2004JD004945","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13244270269&doi=10.1029%2f2004JD004945&partnerID=40&md5=69a87616d02129072a6bf93a1be8c693","The first three-dimensional global model in which time-dependent spectral albedos and emissivities over snow and sea ice are predicted with a radiative transfer solution, rather than prescribed, is applied to study the climate response of fossil fuel plus biofuel black carbon plus organic matter (ff+bf BC+OM) when BC absorption in snow and sea ice is accounted for. The model treats the cycling of size-resolved BC+OM between emission and removal by dry deposition and precipitation from first principles. Particles produce and enter size-resolved clouds and precipitation by nucleation scavenging and aerosol-hydrometeor coagulation. Removal brings BC to the surface, where internally and externally mixed BC in snow and sea ice affects albedo and emissivity through radiative transfer. Climate response simulations were run with a ff+bf BC+OC emission inventory lower than that used in a previous study. The 10-year, globally averaged ff+bf BC+OM near-surface temperature respouse due to all feedbacks was about +0.27 K (+0.32 in the last 3 years), close to those from the previous study (5-year average of +0. 3 K and fifth-year warming of +0.35 K) and its modeled range (+0.15 to +0.5 K) because warming due to soot absorption in snow and sea ice here (10-year average of +0.06 K with a modeled range of +0.03 to +0.11 K) offset reduced warming due to lower emission. BC was calculated to reduce snow and sea ice albedo by ∼0.4% in the global average and 1% in the Northern Hemisphere. The globally averaged modeled BC concentration in snow and sea ice was ∼5 ng/g; that in rainfall was ∼22 ng/g. About 98% of BC removal from the atmosphere was due to precipitation; the rest was due to dry deposition. The results here support previous findings that controlling ff+bf BC+OM and CO 2 emission may slow global warming. Copyright 2004 by the American Geophysical Union."
"56055143800;55703589700;35744799500;7401900689;57211572218;","Taking China's temperature: Daily range, warming trends, and regional variations, 1955-2000",2004,"10.1175/3230.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-11044236028&doi=10.1175%2f3230.1&partnerID=40&md5=9d37fc116cee6e0c7ffb7843492addf4","In analyzing daily climate data from 305 weather stations in China for the period from 1955 to 2000, the authors found that surface air temperatures are increasing with an accelerating trend after 1990. They also found that the daily maximum (Tmax) and minimum (T min) air temperature increased at a rate of 1.27° and 3.23°C (100 yr)-1 between 1955 and 2000. Both temperature trends were faster than those reported for the Northern Hemisphere, where Tmax and Tmin increased by 0.87° and 1.84°C (100 yr)-1 between 1950 and 1993. The daily temperature range (DTR) decreased rapidly by -2.5°C (100 yr)-1 from 1960 to 1990; during that time, minimum temperature increased while maximum temperature decreased slightly. Since 1990, the decline in DTR has halted because Tmax and T min increased at a similar pace during the 1990s. Increased minimum and maximum temperatures were most pronounced in northeast China and were lowest in the southwest. Cloud cover and precipitation correlated poorly with the decreasing temperature range. It is argued that a decline in solar irradiance better explains the decreasing range of daily temperatures through its influence on maximum temperature. With declining solar irradiance even on clear days, and with decreases in cloud cover, it is posited that atmospheric aerosols may be contributing to the changing solar irradiance and trends of daily temperatures observed in China. © 2004 American Meteorological Society."
"7005742190;12141333900;7102759403;","Cloud detection in the tropics - A suitable tool for climate-ecological studies in the high mountains of Ecuador",2004,"10.1080/01431160410001709967","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8744278258&doi=10.1080%2f01431160410001709967&partnerID=40&md5=ef7697fd2939bbc1e242891cfd33dd19","The detection of clouds and the analysis of cloud frequency play an important role for operational weather prediction as well as for climate-ecological studies. A threshold technique for cloud detection in the tropical mountainous area of Ecuador is presented which is based on National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA-AVHRR) data. Cloud classification is performed for both day and night overpasses by applying several threshold tests which also include ancillary terrain information. From a set of 155 images, maps of relative cloud frequency are calculated for Ecuador and adjacent areas as well as the central study area of an ecological project in southern Ecuador (Loja). Results show a clear relation between topography, main airflow and cloudiness due to barrage and lee-effects. The spatial extension of high mountain ecosystems such as the Ecuadorian Páramo has been proven to be significantly influenced by the spatial pattern of cloud frequency. © 2004 Taylor & Francis Ltd."
"6602806333;6507612473;6701594686;6507039600;23970271800;","Recent improvements to LWP retrievals from AVHRR",2004,"10.1016/j.atmosres.2004.03.031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8644257512&doi=10.1016%2fj.atmosres.2004.03.031&partnerID=40&md5=96f9860dce49aa9073b77a5f358b76bb","In the framework of the Cloud Liquid Water Network (CLIWA-NET) project, an attempt is made to reconstruct the spatial distribution of liquid water path (LWP) by combining data from a network of ground-based microwave radiometers with imagery of the Advanced Very High Resolution Radiometer (AVHRR). In order to provide atmospheric modelers sufficient high-quality reference data for model evaluation and improvement, measurements from three intensive measurement campaigns are analyzed. This paper describes the AVHRR quantitative cloud analysis environment that was developed and tested at the Royal Netherlands Meteorological Institute (KNMI) during the project. The environment is named KLAROS (KNMI Local Implementation of APOLLO in an Operational System). KLAROS includes retrieval of a suite of physical cloud parameters. In order to evaluate the liquid water path retrieval, ground-based radiometer measurements are used. A new technique, called the Russian doll method, is introduced to assess the relation between ground and satellite measurements. This relation depends on the variability in time and space of the observed cloud fields and shows up clearly in the Russian doll diagrams. First, results from the comparisons give confidence that KLAROS gives plausible liquid water path values. We find that AVHHR data from the NOAA-16 platform is much better suited for quantitative cloud analysis than its predecessors. In particular, the availability of a 1.6-μm channel and the good calibration contribute to the improved accuracies. The retrieval method for liquid water path will be implemented in the framework of the Satellite Application Facility of Climate Monitoring (CM-SAF). © 2004 Published by Elsevier B.V."
"7103246957;","Understanding hydrometeorology using global models",2004,"10.1175/BAMS-85-11-1673","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10244228505&doi=10.1175%2fBAMS-85-11-1673&partnerID=40&md5=2819523edc94f888b20ad7aed5e0fa10","The land surface coupling, a crucial element of the climate system, is explored in the recent 40-yr European Centre for Medium-Range Forecasts (ECMWF) reanalysis (ERA-40) model. In seasonal forecasts for the Northern Hemisphere summer, initialized with idealized soil moisture fields, the ERA-40 model has a large evaporation-precipitation feedback over the continents, and the memory of initial soil moisture is longest at high northern latitudes. Thirty years of hourly data from the ERA-40 reanalysis are averaged over the Madeira, Red-Arkansas and Athabasca River basins. Although the model fully resolves the diurnal cycle and has an interactive prognostic cloud field, the transitions in the boundary layer climate over land can be mapped with remarkable precision by the daily mean state and daily flux averages. The coupling to cloud processes plays an essential role in the surface and boundary layer equilibrium. Soil moisture, cloud base, cloud cover, radiation fields, and evaporative fraction are coupled quite tightly on daily time scales. The long wave flux control by cloud-base height and cloud cover is particularly strong across all basins. Evaporation can be regarded as being determined somewhat indirectly by the dependence of net radiation on cloud cover and cloud base, and sensible heat flux on subcloud-layer processes. Cloud and boundary layer processes and the land surface components of a model must be evaluated as a tightly coupled system, not as independent components. This analysis provides a new framework for comparing global models with each other, and for evaluating them against observations. © 2004 American Meteorological Society."
"16401545000;6602621536;55999772700;7102708039;7003532404;","Radiative energy partition and cloud radiative forcing at a Po valley site",2004,"10.1016/j.atmosres.2004.03.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8644246623&doi=10.1016%2fj.atmosres.2004.03.022&partnerID=40&md5=8736b1940aec95727d0379b3a3847dc8","Values of downward and upward flux densities of solar and terrestrial radiation were continuously recorded between 1 December 2001 and 30 November 2002 using a four-components radiometer at S. Pietro Capofiume (SPC) in northern Italy (44°39′N, 11°37′E, alt. 11 m a.m.s.l.), which is characterized by a weakly-reflective surface. The aim of the study was to investigate the effects of clouds on surface radiation balance (SRB); the cloud fraction (N) has been retrieved through the inverted form of the parameterization proposed by Kasten and Czeplak [Solar Energy 24 (1980) 177] and cloud types estimated following the methodology of Duchon and O'Malley [J. Appl. Meteorol. 38 (1999) 132]. The cloud radiative forcing (CRF) was evaluated through the Bintanja and Van den Broeke [Int. J. Climatol. 16 (1996) 1281] formula and then associated with cloud type. Experimental results showed that during the measuring period the net shortwave (Sw) balance always decreased with increasing N, whereas the net longwave (Lw) balance increased in all seasons. The net radiation available at the surface decreased with increasing N in all seasons except in winter, where no significant dependency was detected. The analysis of the cloud radiative forcing indicates that all seasons were characterized by a net cooling of the surface except winter, where clouds seem to have no effects on the surface warming or cooling. Taking into account the dependence on solar radiation cycle, an intercomparison between the retrieved cloud types seems to indicate that the effect of stratus was a slight cooling whereas that of cumulus clouds was a stronger cooling of the surface. On the contrary, cirrus clouds seem to have slight warming effect on the surface. The annual trends of mean monthly values of shortwave and longwave radiation balances confirmed that the measurement site is characterized by a temperate climate. Moreover, in spite of the cooling effect of clouds, a monthly radiative energy surplus is available all year long for surface-atmosphere energy exchanges. The analysis is also instrumental for the detection of SRB variations. © 2004 Elsevier B.V. All rights reserved."
"7407116104;7004325649;7403931916;6602844274;57201874118;7404150761;","Application of deep convective cloud albedo observation to satellite-based study of the terrestrial atmosphere: Monitoring the stability of spaceborne measurements and assessing absorption anomaly",2004,"10.1109/TGRS.2004.834765","https://www.scopus.com/inward/record.uri?eid=2-s2.0-9944262479&doi=10.1109%2fTGRS.2004.834765&partnerID=40&md5=89322a51fb504abaaad028b852c1cdf2","An objective method is developed to monitor the stability of spaceborne instruments, aimed at distinguishing climate trend from instrument drift in satellite-based climate observation records. This method is based on four-years of Clouds and the Earth's Radiant Energy System (CERES) broadband observations of deep convective cloud systems with cloud-top temperature lower than 205 K and with large optical depths. The implementation of this method to the CERES instrument stability analysis reveals that the monthly albedo distributions are practically the same for deep convective clouds with CERES measurements acquired from both the Tropical Rainfall Measuring Mission and Terra satellite platforms, indicating that CERES instruments are well calibrated and stable during both missions. Furthermore, with a nonlinear regression neural network narrowband-broadband conversion, this instrument-stability monitoring method can also be applied to narrowband instruments such as the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Visible Infrared Scanner (MRS). The results show that the drifts associated with both VIRS and MODIS instruments are less than 1% during a four-year period. Since the CERES albedo measurements are highly accurate, the absorptance of these opaque clouds can be reliably estimated. The absorptions of these clouds from observations are around 25%, whereas the absorptions from theory can be as low as 18%, depending on ice cloud microphysics."
"7004339809;7003696273;24460392200;15840593700;","The effect of cirrus clouds on microwave limb radiances",2004,"10.1016/j.atmosres.2004.03.023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8644268014&doi=10.1016%2fj.atmosres.2004.03.023&partnerID=40&md5=acc718b55ccc3398506f3ef1808a3525","This study presents and analyses the first simulations of microwave limb radiances with clouds. They are computed using the 1D unpolarized version of the Atmospheric Radiative Transfer System (ARTS). The study is meant to set a theoretical foundation for using microwave limb measurements for cloud monitoring. Information about clouds is required for the validation of climate models. Limb spectra are generated for the frequency bands of the Millimeter wave Acquisitions for Stratosphere/Troposphere Exchange Research (MASTER) instrument. For these simulations, the radiative transfer equation is solved using the Discrete Ordinate ITerative (DOIT) method, which is briefly described. Single scattering properties for the cloud particles are calculated using the T-matrix method. The impact of various cloud parameters is investigated. Simulated brightness temperatures most strongly depend on particle size, ice mass content and cloud altitude. The impact of particle shape is much smaller, but still significant. Increasing the ice mass content has a similar effect as increasing the particle size; this complicates the prediction of the impact of clouds on microwave radiances without exact knowledge of these cloud parameters. © 2004 Elsevier B.V. All rights reserved."
"7402056142;7102223138;35512883100;23162993500;","A finite element-spherical harmonics model for radiative transfer in inhomogeneous clouds. Part II. Some applications",2004,"10.1016/j.atmosres.2004.03.021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8644273954&doi=10.1016%2fj.atmosres.2004.03.021&partnerID=40&md5=4204981796333023dbc78edba51870c6","EVENT has been used to examine the effects of 3D cloud structure, distribution, and inhomogeneity on the scattering of visible solar radiation and the resulting 3D radiation field. Large eddy simulation and aircraft measurements are used to create realistic cloud fields which are continuous or broken with smooth or uneven tops. The values, patterns and variance in the resulting downwelling and upwelling radiation from incident visible solar radiation at different angles are then examined and compared to measurements. The results from EVENT confirm that 3D cloud structure is important in determining the visible radiation field, and that these results are strongly influenced by the solar zenith angle. The results match those from other models using visible solar radiation, and are supported by aircraft measurements of visible radiation, providing confidence in the new model. © 2004 Elsevier B.V. All rights reserved."
"6602364115;6603566335;6701519241;7006904374;","An evaluation of mass flux closures for diurnal cycles of shallow cumulus",2004,"10.1175/MWR2776.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10244266366&doi=10.1175%2fMWR2776.1&partnerID=40&md5=10e71fb093c506b7a98a513ccef7dce0","Three closure methods for the mass flux at cloud base in shallow cumulus convection are critically examined for the difficult case of a diurnal cycle over land. The closure methods are first evaluated against large-eddy simulations (LESs) by diagnosing all parameters appearing in the closure equations during simulations of two different observed diurnal cycles of shallow cumulus. This reveals the characteristic behavior of each closure mechanism purely as a result of its core structure. With these results in hand the impact of each closure on the development of the cloudy boundary layer is then studied by its implementation in an offline single-column model of a regional atmospheric climate model. The LES results show that the boundary layer quasi-equilibrium closure typically overestimates the cloud-base mass flux after cloud onset, due to the neglect of significant moisture and temperature tendencies in the subcloud layer. The convective available potential energy (CAPE) adjustment closure is compromised by its limitation to compensating subsidence as the only CAPE breakdown mechanism and the use of a constant adjustment time scale. The closure method using the subcloud convective vertical velocity scale gives the best results, as it catches the time development of the cloud-base mass flux as diagnosed in LES. © 2004 American Meteorological Society."
"7402302276;7004316629;7004465394;","Impact of cold flow improvers on soybean biodiesel blend",2004,"10.1016/j.biombioe.2004.04.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4344621716&doi=10.1016%2fj.biombioe.2004.04.006&partnerID=40&md5=c12ece7a1cef8e964d7c43730eeec314","The use of biodiesel as a diesel fuel extender and lubricity improver is rapidly increasing. An import aspect of using these extenders is their transport in cold climates and subsequent mixing with cold diesel fuel. In this paper, the cold flow properties of biodiesel (B100) and 80% (B80) to 90% biodiesel in kerosene were evaluated with pour point depressants, toward the objective of identifying approaches to transport and mix biodiesel with diesel in cold climates. Four cold flow improver additives were tested at 0.1-2% in B80, B90, and B100 blends. Two additives significantly decreased the pour points of soybean biodiesel blends, but all the four additives had little effect on cloud points. A mixture of 0.2% additive, 79.8% biodiesel, and 20% kerosene reduced the pour point of B100 by 27°C. © 2004 Elsevier Ltd. All rights reserved."
"6603081424;7201844203;6701346974;25941200000;7003398947;","Performance of Goddard earth observing system GCM column radiation models under heterogeneous cloud conditions",2004,"10.1016/j.atmosres.2004.03.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8644277057&doi=10.1016%2fj.atmosres.2004.03.025&partnerID=40&md5=1a7e74ff1d9b48b207f9f31b4d9a741d","We test the performance of the shortwave (SW) and longwave (LW) Column Radiation Models (CORAMs) of Chou and collaborators with heterogeneous cloud fields from a single-day global dataset produced by NCAR's Community Atmospheric Model (CAM) with a 2-D Cloud Resolving Model (CRM) installed in each column. The original SW version of the CORAM performs quite well compared to reference Independent Column Approximation (ICA) calculations for boundary fluxes (global error ∼4 W m-2 for reflected flux), largely due to the success of a combined overlap and cloud scaling parameterization scheme. The absolute magnitude of errors relative to ICA are even smaller (global error ∼2 W m-2 for outgoing flux) for the LW CORAM which applies similar overlap. The vertical distribution of heating and cooling within the atmosphere is also simulated quite well with daily averaged zonal errors always less than 0.3 K/day for SW and 0.6 K/day for LW heating (cooling) rates. The SW CORAM's performance improves by introducing a scheme that accounts for cloud inhomogeneity based on the Gamma Weighted Two Stream Approximation (GWTSA). These results suggest that previous studies demonstrating the inaccuracy of plane-parallel models may have unfairly focused on worst case scenarios, and that current radiative transfer algorithms in General Circulation Models (GCMs) may be more capable than previously thought in estimating realistic spatial and temporal averages of radiative fluxes, as long as they are provided with correct mean cloud profiles. However, even if the errors of our particular CORAMs are small, they seem to be systematic, and their impact can be fully assessed only with GCM climate simulations. © 2004 Elsevier B.V. All rights reserved."
"6603250042;","Optical thickness of stratiform clouds over the Baltic inferred from on-board irradiance measurements",2004,"10.1016/j.atmosres.2004.03.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8644282722&doi=10.1016%2fj.atmosres.2004.03.012&partnerID=40&md5=6186eb866381436dc439f7ce52d0c988","The paper discusses the optical thickness of non-precipitating layer clouds retrieved from irradiance measurements collected during cruises of R/V Oceania to the Baltic Sea from 1994 to 2002. Pyranometer measurements were accompanied by standard meteorological observations. Cloud optical thickness was obtained by a comparison of downward irradiance in the visible part of the spectrum averaged over 1-min intervals with MODTRAN4 (MOD4v2r1) computations. For an individual cloud retrieval, the total statistical error varies from 28% to over 100%. This is mainly attributed to irradiance measurement error, uncertainties in aerosol optical thickness, the lack of information on cloud droplet radius and the assumption of cloud horizontal uniformity. The systematic error (bias) due to the plane-parallel assumption is negative (the cloud optical thickness is overestimated) and is estimated at several percent. Statistical analysis of the optical thickness of layer clouds over the Baltic was performed with two purposes in mind: to look for (1) seasonal variations in cloud optical thickness and (2) for differences in cloud optical thickness for various cloud 'classes'. The cloud 'classes' were distinguished with respect to the following: total cloud cover N and low-level cloud cover NL, and cloud type predominating in the sky (SHIP meteorological reports, WMO cloud classification and coding). Cloud optical thickness distributions for low-level layer clouds can be approximated by a lognormal distribution, the parameters of which depend on the cloud class. The mean base-10 logarithm of τ varies from about 1 (τ =10) for semi-transparent clouds and cloud classes with N =7 to 1.5 for the class defined by N = NL=8 (overcast sky) and CL=7 (low-level clouds before or after precipitation). The values obtained are consistent with findings by other researchers. For the joint class containing all cases with N =8, the lowest mean logarithm of τ was found for February (about 1, which corresponds to τ =10) and the highest for the spring months, from March to May (1.3-1.4, which correspond to τ =20-25). However, the low number of data available does not allow for an accurate description of the annual cycle. © 2004 Elsevier B.V. All rights reserved."
"36799718200;35555822400;7404325680;","Relic volcanic ash and dust still an aviation hazard",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-10944248450&partnerID=40&md5=c66a234c3a1d5348ee567f1c990f6679","Volcanic eruptions at the Katmai National Park and Preserve in 1912 buried more than 40 mi2 of lush green land beneath volcanic ash and debris. On 20-21 September 2003, a very large amount of this relic ash was resuspended into the atmosphere. It was proposed that the strong northwest winds blowing over local mountains resulted in a downward acceleration on the lee side of the mountains, and that hydraulic flow entrained the ash at the mountain base. The resulting ash /dust cloud created a serious hazard to aviation."
"56627468800;7102223138;35512883100;","A finite element-spherical harmonics model for radiative transfer in inhomogeneous clouds Part I. The EVENT model",2004,"10.1016/j.atmosres.2004.03.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8644268020&doi=10.1016%2fj.atmosres.2004.03.020&partnerID=40&md5=6a104716e881086d0ab355129bd8a1ed","We present a new numerical radiative transfer model for application to solar radiation transport in three-dimensional (3D) cloudy atmospheres. The code uses the finite element-spherical harmonics (FE- PN) approximation to solve the second-order even-parity form of the transport equation. It is validated by comparison with solutions from two well-established, deterministic radiative transfer models, the one-dimensional (1D) DISORT code and the spherical harmonics discrete ordinates method (SHDOM). The cases solved show generally good agreement, but also reveal some differences. EVEn-parity Neutral particle Transport (EVENT) is very efficient at performing 1D calculations quickly and, even for quite high angular resolutions, is faster. EVENT also has a competitive speed for the simpler, less-heterogeneous multidimensional cases but it is slower than SHDOM for more variable cases. However, there is significant potential to improve the performance of EVENT; it has not yet been optimised for speed and, as such, is not a finished product. Even as it is, EVENT could be used to produce fast, lower-resolution estimates for applications where this would be sufficient, or at lower-spatial resolutions with partial homogenisation. Another difference between the models is that the SHDOM algorithm is designed for small-scale inhomogeneous cloud fields in which the grid spacing is comparable to the mean free path. Problems arise from the use of larger grid cell optical depths, with an increase in the number of iterations required and a lack of flux conservation. Neither of the models is specifically constrained to conserve flux, but the conservation of flux gives an indication of the accuracy of the solution. Increasing the spatial and angular resolution can improve the accuracy but this is not always possible for very large 3D scenes. The grid-point method of property definition in SHDOM means that it performs best for cases with a continuous variation in extinction as this avoids discontinuities in the source function. The finite clouds used in our tests have sharp boundaries that are easily defined in EVENT but the difficulties caused by these in SHDOM are evident in excesses of up to 10 fluxes. The EVENT mesh resolution is determined by the local optical depth; it has no problem in dense areas but has more trouble in coping with voids or optically thin regions. These conditions are easily handled in SHDOM through streaming of photons along discrete ordinates but EVENT must implement methods such as a ray-tracing algorithm. Cases with extreme values of the extinction coefficient are probably best avoided with EVENT, but slightly larger-scale cases with greater optical depths, not suitable for SHDOM, may be solved more easily. These factors should be considered when selecting the most appropriate method for a particular application. © 2004 Elsevier B.V. All rights reserved."
"56196145800;6701313597;7102862273;7004692414;7102490158;55633197600;7003383481;6603457933;7003726515;","Interpretation of Arctic aerosol properties using cluster analysis applied to observations in the Svalbard area",2004,"10.1111/j.1600-0889.2004.00128.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-9444252812&doi=10.1111%2fj.1600-0889.2004.00128.x&partnerID=40&md5=713f383dad32ab5d9f948128f3d224da","Atmospheric aerosols play an important role in global climate change, directly through radiative forcing and indirectly through their effect on cloud properties. Numerous measurements have been performed in the last three decades in order to characterize polar aerosols. Information about aerosol characteristics is needed to calculate induced changes in the Earth's heat balance. However, this forcing is highly variable in space and time. Accurate quantification of forcing by aerosols will require combined efforts, assimilating information from different sources such as satellite, aircraft and surface-based observations. Adding to the complexity of the problem is that the measurements themselves are often not directly comparable as they vary in spatial/temporal resolution and in the basic properties of the aerosol that they measure. Therefore it is desirable to close the gap between the differences in temporal and spatial resolution and coverage among the observational approaches. In order to keep the entire information content and to treat aerosol variability in a consistent and manageable way an approach has to be achieved which enables one to combine these data. This study presents one possibility for linking together a complex Arctic aerosol data set in terms of parameters, timescale and place of measurement as well as meteorological parameters. A cluster analysis was applied as a pattern recognition technique. The data set is classified in clusters and expressed in terms of mean staristical values, which represent the entire database and its variation. For this study, different time-series of microphysical, optical and chemical aerosol parameters as well as meteorological parameters were analysed. The database was obtained during an extensive aerosol measurement campaign, the ASTAR 2000 (Arctic Study of Tropospheric Aerosol and Radiation) field campaign, with coordinated simultaneous ground-based and airborne measurements in the vicinity of Spitsbergen (Svalbard). Furthermore, long-term measurements at two ground-based sites situated at different altitudes were incorporated into the analysis. The approach presented in this study allows the necessary linking of routine long-term measurements with short-term extensive observations. It also involves integration of intermittent vertical aerosol profile measurements. This is useful for many applications, especially in climate research where the required data coverage is large. Copyright © Blackwell Munksguard 2004."
"6701612537;6602117886;","On the correlation between the recent star formation rate in the Solar Neighbourhood and the glaciation period record on Earth",2004,"10.1016/j.newast.2004.05.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7444234852&doi=10.1016%2fj.newast.2004.05.001&partnerID=40&md5=8afba0611d16857a1ee51a22938c7ac2","Shaviv [New Astron. 8 (2003) 39; J. Geophys. Res. 108 (2003) 3] has shown evidence for a correlation between variations in the Galactic cosmic ray flux reaching Earth and the glaciation period record on Earth during the last 2 Gyr. If the flux of cosmic rays is mainly the result of Type II supernovae, an additional correlation between the star formation history of the Solar Neighbourhood and the timing of past ice ages is expected. Higher star formation rate implies increased cosmic ray flux and this may translate into colder climate through a rise in the average low altitude cloud cover. Here we reanalyze the correlation between this star formation history and the glaciation period record on Earth using a volume limited open cluster sample. Numerical modeling and recent observational data indicate that the correlation is rather strong but only if open clusters within 1.5 kpc from the Sun are considered. Under this constraint, our statistical analysis not only suggests a strong correlation in the timing of the events (enhanced star formation and glaciation episodes), but also in the severity and length of the episodes. In particular, the snowball Earth scenario appears to be connected with the strongest episode of enhanced star formation recorded in the Solar Neighbourhood during the last 2 Gyr. © 2004 Elsevier B.V. All rights reserved."
"6602318640;","May 2003 disaster in Sri Lanka and cyclone 01-B in the bay of Bengal",2004,"10.1023/B:NHAZ.0000048462.21938.d6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-9144233662&doi=10.1023%2fB%3aNHAZ.0000048462.21938.d6&partnerID=40&md5=9150a2cc76f50c2d93a3bd5dc2369265","Heavy rainfall deluged South-Western Sri Lanka between the 11th and 19th of May 2003 and led to its worst disaster in 50 years. Floods and landslides claimed 260 lives. The World Meteorological Organization cited it as evidence for the increase of anomalous climatic extremes in recent years. Here, a meteorological analysis is presented of this disaster as part of a sustained effort to undertake meteorological applications for disaster management. There were intense low-level westerlies over Sri Lanka related to cyclone 01-B that made its way across the Bay of Bengal at least 700 km away. The southeastwardly traverse of the cyclone was stalled for a few days by anomalous north-westerly geostrophic winds ver South Asia. Here, it is argued that orographic rainfall induced by this stalled cyclone and seasonal inter-tropical convergence zone cloud bands over Sri Lanka led to the deluge. The trajectory of the cyclone was remote from Sri Lanka and this led to no cyclone hazard warnings being issued. No cyclones have made landfall in Sri Lanka in May in the last 100 years. This study shows that one must exercise vigilance not only in the path of the cyclone but also remotely due to the modulation of the cyclone by other atmospheric phenomenon and topographic features. This flood may have been predicted with contemporary local area weather prediction models and this example points to the need for the development of local area weather prediction models as part of disaster warning systems. This study also demonstrates the use of meteorological diagnostics for post-event analysis of hydrometeorology of disaster events. © 2004 Kluwer Academic Publishers."
"56014511300;7006783796;35547214900;","Deep convective cloud-top heights and their thermodynamic control during CRYSTAL-FACE",2004,"10.1029/2004JD004811","https://www.scopus.com/inward/record.uri?eid=2-s2.0-11844291292&doi=10.1029%2f2004JD004811&partnerID=40&md5=ff58663a33f5a2e072f21424fd81af5e","Infrared (11 μm) radiances from GOES-8 and local radiosonde profiles, collected during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) in July 2002, are used to assess the vertical distribution of Florida-area deep convective cloud-top height and test predictions as to its variation based on parcel theory. The highest infrared tops (Z11) reached approximately to the cold point at 15.4 km, though these are uncertain by about 1 km due to unknown cloud-environment temperature differences. Since lidar shows that visible ""tops"" are generally 1 km or more above Z11, visible cloud tops frequently penetrated the lapse-rate tropopause (∼ 15 km). Further, since tropospheric ice concentrations were typically present up to ∼ 1 km above the visible tops, lofting of moisture through the mean cold point was probably common. Morning clouds, and those near Key West, rarely penetrated the tropopause. As in previous studies, nonentraining parcel theory fails to explain either of these results, though it does show promise in explaining day-to-day variations over the peninsula. Moisture variations above the boundary layer account for much of the day-to-day Z 11 variability, especially over the oceans. In all locations a 20% increase in mean mixing ratio between 750 and 500 hPa was associated with about 1 km deeper maximum cloud penetration, other things being equal. This sensitivity is too large to explain by simple dilution of parcel buoyancy through mixing, implying microphysical or dynamical feedbacks on cloud development. The evident influence of midtropospheric humidity on the depth of the tropical troposphere suggests an interesting climate feedback possibility for stabilizing midtropospheric relative humidity. Copyright 2004 by the American Geophysical Union."
"57203053317;","Can anthropogenic aerosols decrease the snowfall rate?",2004,"10.1175/1520-0469(2004)061<2457:CAADTS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8744230599&doi=10.1175%2f1520-0469%282004%29061%3c2457%3aCAADTS%3e2.0.CO%3b2&partnerID=40&md5=7d4edad9e27bcccab6f63c89e65152f4","Observations by Borys, Lowenthal, Cohn, and Brown in midlatitude orographic clouds show that for a given supercooled liquid water content, both the riming and the snowfall rates are smaller if the supercooled cloud has more cloud droplets as, for example, caused by anthropogenic aerosols. The climatic implication of this effect was studied in global climate model simulations by replacing the constant riming efficiency with a size-dependent one appropriate for planar crystals and aggregates, respectively. In the model simulations that use a size-dependent riming collection efficiency, the pollution-induced decrease in cloud droplet size causes a decrease in the riming rate in stratiform clouds despite larger liquid water contents in polluted clouds. Contrary to the above-mentioned observations, in all model simulations the snowfall rate increases because of feedbacks in the climate system. Anthropogenic aerosol particles increase the aerosol and cloud optical thickness, which reduces the solar radiation at the top of the atmosphere and the surface. This in turn causes a cooling in Northern Hemisphere midlatitudes that favors precipitation formation via the ice phase. © 2004 American Meteorological Society."
"7003543851;7003922138;6701618837;","On the use of cloud forcing to estimate cloud feedback",2004,"10.1175/1520-0442(2004)017<3661:OTUOCF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-6044251401&doi=10.1175%2f1520-0442%282004%29017%3c3661%3aOTUOCF%3e2.0.CO%3b2&partnerID=40&md5=357a27656c1d07c486ee737b840e4067","Uncertainty in cloud feedback is the leading cause of discrepancy in model predictions of climate change. The use of observed or model-simulated radiative fluxes to diagnose the effect of clouds on climate sensitivity requires an accurate understanding of the distinction between a change in cloud radiative forcing and a cloud feedback. This study compares simulations from different versions of the GFDL Atmospheric Model 2 (AM2) that have widely varying strengths of cloud feedback to illustrate the differences between the two and highlight the potential for changes in cloud radiative forcing to be misinterpreted. © 2004 American Meteorological Society."
"56000281400;7007108728;","Aircraft observations of cloud droplet number concentration: Implications for climate studies",2004,"10.1256/qj.03.120","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8344260675&doi=10.1256%2fqj.03.120&partnerID=40&md5=24820c286d0c39b44a058ed128f37ebc","Droplet number concentration (Nd) is a major parameter affecting cloud physical processes and cloud optical characteristics. In most climate models, Nd is usually assumed to be constant or a function of the droplet and aerosol number concentration (N a). Three types of cloud systems over Canada, namely Arctic clouds, maritime boundary-layer clouds, and winter storms, were studied to obtain values of Nd as a function of temperature (T). The probability density function of Nd was also calculated to show the variability of this parameter. The results show that Nd reaches a maximum at about 10°C (200 cm -3) and then decreases gradually to a minimum (∼1-3 cm-3) at about -35°C. A comparison of relationships between Nd and Na indicates that estimates of N d from Na can have an uncertainty of about 30-50 cm-3, resulting in up to a 42% uncertainty in cloud short-wave radiative forcing. This study concludes that the typical fixed values of Nd, which are ∼100 cm-3 and ∼200 cm-3 for maritime and continental clouds, respectively, and the present relationships of Nd to N a, could result in a large uncertainty in the heat and moisture budgets of the earth's atmosphere. It is suggested that the use of relationships between Nd and T can improve climate simulations. © Crown, 2004."
"7005477332;7005626683;57189585133;6701803760;7005928149;7006307463;56520921400;23476370700;7005399437;7004166136;7201463831;7003621869;7101938512;55740664200;7006634316;7102604282;7006705919;55207447000;57196499374;7202899330;57203174863;7101718859;7004325649;56933322900;","PARAGON: An integrated approach for characterizing aerosol climate impacts and environmental interactions",2004,"10.1175/BAMS-85-10-1491","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8444229359&doi=10.1175%2fBAMS-85-10-1491&partnerID=40&md5=f1ba1a60e130dbd22278179f96215d8d","The Progressive Aerosol Retrieval and Assimilation Global Observing Network (PARAGON) is a vehicle designed to facilitate the transformation of information into knowledge, and ideas into action. This integrated approach merges multiple observation techniques, modeling capabilities, geospatial statistics research, and high-performance information technologies into a systematic framework. In addition to aerosol-climate interactions, the concept can also be applied to other problems, such as, the impact of aerosols on air quality, or the study of cloud-climate forcing and feedbacks."
"6603868770;55982290400;6602806333;57214398762;6507612473;6508104909;7004139339;6603196991;6603873829;6602565779;7003728829;56249134600;36807959100;15053643400;7004167838;55339298600;57202119596;7004357137;7005174340;6603341831;","The baltex bridge campaign: An integrated approach for a better understanding of clouds",2004,"10.1175/BAMS-85-10-1565","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042770713&doi=10.1175%2fBAMS-85-10-1565&partnerID=40&md5=faac7f81c7f9635202d86c0d8a9f21af","To improve modeling and forecasting of clouds in climate and numerical weather prediction (NWP) models, the BALTEX Bridge Campaign (BBC) was conducted in the Netherlands in August/September 2001 as a contribution to the main field experiment of the Baltic Sea Experiment (BALTEX) from April 1999 to March 2001 (BRIDGE). Advanced remote sensing instruments were operated at the central facility in Cabauw, Netherlands, to derive the vertical cloud structure. To evaluate the performance of dynamic atmospheric models for the cloudy atmosphere four operational climate and NWP models were compared to the observations. Initial results show that increased vertical resolution can improve the representation of clouds in these models."
"6603463229;","Changes in spring-summer cirrus cloud amount over Estonia, 1958-2003",2004,"10.1002/joc.1055","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7244229445&doi=10.1002%2fjoc.1055&partnerID=40&md5=5fc7fd622d68db788c18c15f65656853","The data of hourly cloud detection during daytime at the Tartu-Tõravere meteorological station for the period 1958-2003 have been treated to find the monthly mean amounts of cirrus clouds (in tenths) for March-September and to study their variance. The highest mean value (4.1 tenths) was found in April and the lowest (three tenths) in July. The results of previous cloud-type notation frequency-based studies using no quantitative measure for cirrus cloud amount exhibit a maximum in June. The smoothed March-September cirrus cloud amount for 1958-2003 manifests alternation of relatively high and relatively low amounts with a period of approximately 20 years. The relative contribution of clear skies (cirrus amounts less than one tenth) has decreased, the lowest being during 1991-96. The cirrus cloud amount was weakly correlated with local characteristics of atmospheric moisture, such as precipitation, total cloud amount and low cloud amount. Low average cirrus amounts, however, were often recorded when the spring was dry. High cirrus amounts were observed when spring and most months were wet. © 2004 Royal Meteorological Society."
"57196499374;7201463831;57189585133;7006307463;23476370700;7005477332;7006634316;55207447000;7004325649;","Scientific objectives, measurement needs, and challenges motivating the PARAGON aerosol initiative",2004,"10.1175/BAMS-85-10-1503","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8444249679&doi=10.1175%2fBAMS-85-10-1503&partnerID=40&md5=d5747df40ad0ca7a0a6dd8f898ef756e","The discrepancy between the uncertainty in forward and inverse models remains a key issue in predicting future climate response to increased greenhouse gases (GHGs), making it critically important to improve and validate three-dimensional global models and to develop more realistic, physically based process representations. Systematic comparison with measurements is the only known way to make models a reliable basis for decisions regarding climate adaptation and mitigation. One approach that makes this possible is PARAGON. A key benefit of using this scheme is the establishment of a worldwide system for studying the impacts of changing aerosol concentrations on air quality."
"55613229930;6602074621;55705627100;57206686711;7403540294;7406871753;","The role of climate variability in the inter-annual variation of terrestrial net primary production (NPP)",2004,"10.1016/j.scitotenv.2004.03.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4444243900&doi=10.1016%2fj.scitotenv.2004.03.009&partnerID=40&md5=d050866475afb6b6248cb08d9e135c8e","Eleven years data set of global net primary production (NPP) and long-term climatic and land use data were used to explore the patterns of inter-annual variability of terrestrial NPP in relation to potential causal factors. Global anomalies in temperature, precipitation and cloud cover were found to significantly contribute in different ways and magnitudes to the variability of NPP of global ecosystems particularly forests and grasslands. El Niño/La Niña events represented an important factor affecting forests, woodlands and grasslands while deforestation was found to largely contribute to the NPP variability of tropical forests. Regionally, NPP variability is related to variation of precipitation in the tropics but is related to both variation and annual mean of temperature and cloud cover in the mid-northern latitudes. We hypothesized that the increase in variability of potential causal factor(s) will provoke more declines of NPP in the tropics but will yield more pulses or at least maintain a mean NPP in the mid-northern latitudes. © 2004 Elsevier B.V. All rights reserved."
[No author id available],"Aerosol effects in snowfall - And beyond",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-8444228241&partnerID=40&md5=34de3805120bf898ba6ac8158f9cedf9","General circulation model simulations of preindustrial and present-day climate were performed. The decrease in the riming rate was simulated by implementing an efficiency of the riming process that depends on the size of the cloud droplets. Results indicate that microscale processes within clouds can change the amount of precipitation locally. However, the climatic or long-term implications could oppose the microphysical effect when feedbacks of cloud microphysics on the heat and moisture budget are considered."
"6603566335;7006698304;6701519241;6602364115;36097134700;6603873829;57200585664;6603630562;6602811538;8670472000;56865378100;24537575000;7102630621;7005056279;7402078417;6507198458;6507815511;","Cloud representation in general-circulation models over the northern Pacific Ocean: A EUROCS intercomparison study",2004,"10.1256/qj.03.146","https://www.scopus.com/inward/record.uri?eid=2-s2.0-12344288400&doi=10.1256%2fqj.03.146&partnerID=40&md5=aa9ea29e2237482f9e882b1383ddd870","The EUROCS (EUROpean Cloud Systems study) project aims to improve the treatment of cloud systems in regional and global climate and weather prediction models. This paper reports an intercomparison study of cloud representation over the Pacific Ocean for nine climate and weather prediction models. The study consists of an analysis of a June/July/ August 1998 period along an idealized trajectory over the Pacific Ocean that encompasses both the ascending and descending branch of the Hadley circulation. The three cloud types that are studied by EUROCS, stratocumulus, shallow cumulus and deep-convective cloud systems, do all occur in a persistent and geographically separated way, along this trajectory. The main focus of this study is on processes related to the hydrological cycle within the Hadley circulation. These include the large-scale dynamics (i.e. the strength of the up- and downwelling branches of the Hadley cell), the cloud processes (i.e. cloud cover, cloud amounts and precipitation), and the impact of these processes on the radiation budget both at the top of the atmosphere and at the ocean's surface. In order to make a quantitative assessment, special care has been taken to select reliable observational datasets. The main conclusions are that (1) almost all models strongly underpredicted both cloud cover and cloud amount in the stratocumulus regions while (2) the situation is opposite in the trade-wind region and the tropics where cloud cover and cloud amount are overpredicted by most models. These deficiencies result in an overprediction of the downwelling surface short-wave radiation of typically 60 W m-2 in the stratocumulus regimes and a similar underprediction of 60 W m-2 in the trade-wind regions and in the intertropical convergence zone (ITCZ). Similar biases for the short-wave radiation were found at the top of the atmosphere, while discrepancies in the outgoing long-wave radiation are most pronounced in the ITCZ. © Royal Meteorological Society, 2004."
"6506837510;7007108728;6603734019;55087038900;","Liquid fraction in stratiform mixed-phase clouds from in situ observations",2004,"10.1256/qj.03.153","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10944245294&doi=10.1256%2fqj.03.153&partnerID=40&md5=b5cd10a16e71bb56022a48fceb5a4731","Liquid fractions in mixed-phase clouds have been analysed using aircraft 'measurements taken in mid- and high latitude stratiform clouds. The liquid fraction generally increases with temperature but has a minimum at about -15 °C, where the maximum ice crystal growth based on vapour deposition would be expected. The mean liquid fraction also depends on total water content. This suggests that segregation of cloud phase based on a simple linear relationship of phase fraction (ice or liquid) with temperature, as is used in some climate models, may be unrealistic. Parametrizations of mean liquid fraction in terms of temperature and total water content, and in terms of temperature alone, have been developed based on data averaged at 10 s resolution (1 km). These parametrizations agree reasonably well with the observations. © Royal Meteorological Society, 2004."
"7006760857;6603853280;7003554893;6602080773;6507679962;7004160585;7006091410;","Sensitivity of moist convection to environmental humidity",2004,"10.1256/qj.03.130","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844292723&doi=10.1256%2fqj.03.130&partnerID=40&md5=db94a4b9beae36db624d9e8ceca26e54","As part of the EUROCS (EUROpean Cloud Systems study) project, cloud-resolving model (CRM) simulations and parallel single-column model (SCM) tests of the sensitivity of moist atmospheric convection to mid-tropospheric humidity are presented. This sensitivity is broadly supported by observations and some previous model studies, but is still poorly quantified. Mixing between clouds and environment is a key mechanism, central to many of the fundamental differences between convection schemes. Here, we define an idealized quasi-steady 'testbed' , in which the large-scale environment is assumed to adjust the local mean profiles on a timescale of one hour. We then test sensitivity to the target profiles at heights above 2 km. Two independent CRMs agree reasonably well in th eir response to the different background profiles and both show strong deep precipitating convection in the more moist cases, but only shallow convection in the driest case. The CRM results also appear to be numerically robust. All the SCMs, most of which are one-dimensional versions of global climate models (GCMs), show sensitivity to humidity but differ in various ways from the CRMs. Some of the SCMs are improved in the light of these comparisons, with GCM improvements documented elsewhere. © Crown copyright, 2004."
"7006518289;55393048900;6604045869;","Changes in frost days in simulations of twentyfirst century climate",2004,"10.1007/s00382-004-0442-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7744246757&doi=10.1007%2fs00382-004-0442-9&partnerID=40&md5=d00232346fc5844550f034696b4b0966","Global coupled climate model simulations of twentieth and twentyfirst century climate are analyzed for changes in frost days (defined as nighttime minima less than freezing). The model simulations agree with the observed pattern for late twentieth century of a greater decrease of frost days in the west and southwest USA compared to the rest of the country, and almost no change in frost days in fall compared to relatively larger decreases in spring. Associated with general increases of nighttime minimum temperatures, in the future climate with increased greenhouse gases (GHGs) the number of frost days is fewer almost everywhere, but there are greatest decreases over the western parts of the continents. The numbers of frost days are most consistently related to sea level pressure, with more frost days occurring when high pressure dominates on the monthly time scale in association with clearer skies and lower nighttime minimum temperatures. Spatial patterns of relative changes of frost days are indicative of regional scale atmospheric circulation changes that affect nighttime minimum temperatures. Increases of soil moisture and clouds also contribute, but play secondary roles. The linkages among soil moisture, clouds, sea level pressure, and diurnal temperature range are quantified by a statistical multiple regression model. Coefficients for present and future climate are similar among the predictors, indicating physical processes that affect frost days in present and future climates do not appreciably change. Only the intercept changes in association with the significant warming of the mean climate state. This study highlights the fact that, though there is a general decrease in the number of frost days with global warming, the processes that affect the pattern of those changes, and thus the regional changes of frost days, are influenced by several interrelated physical processes, with changes in regional atmospheric circulation generally being most important. © Springer-Verlag 2004."
"57206128696;6603646841;7003473171;","Climate change implications on flood response of a mountainous watershed",2004,"10.1023/B:WAFO.0000044809.79328.9d","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5644259931&doi=10.1023%2fB%3aWAFO.0000044809.79328.9d&partnerID=40&md5=2e9113bb68047204bc38499148d3fbf1","The modification of the flood response due to future climate change is presented for the Illecillewaet watershed of British Columbia, Canada. The Canadian Centre for Climate Modeling Analysis General Circulation Model (CGCMa1) was used for the assessment of changes of precipitation and temperature due to climate change. The runoff was simulated using the UBC watershed model and considering, also, changes on the spatial distribution of precipitation with elevation, cloud cover, glaciers, vegetation distribution, vegetation biomass production, and plant physiology. The results show that the future climate would be wetter and warmer than the present climate affecting the type, the magnitude and the temporal distribution of floods as well as the frequency of flood peaks. The above changes in the flood response of the study watershed could be explained by the change of the form of precipitation from snowfall to rainfall, the consequent decrease of the snowpack, and the initiation of the snowmelt earlier in the season, under the altered climate. © 2004 Kluwer Academic Publishers."
"6701850538;24722339600;35584010200;7004479957;","Reflectivity and rain rate in and below drizzling stratocumulus",2004,"10.1256/qj.03.187","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10944262236&doi=10.1256%2fqj.03.187&partnerID=40&md5=6e861a6438de5d479bf7ad116dc8cba2","Ship-based radar measurements obtained during the East Pacific Investigation of Climate 2001 stratocumulus (Sc) cruise are used to derive characteristics of the rainfall from drizzling Sc. Reflectivity to rain rate (Z-R) relationships are determined from shipboard raindrop-size distribution measurements obtained from observations using filter-paper, and compared to Z-R relationships derived from aircraft probe data from below north-east Atlantic drizzling Sc and stratus. A model for the evaporation and sedimentation of drizzle is combined with reflectivity profiles from a millimetre-wavelength cloud radar to derive information on the mean raindrop radius and drizzle drop concentrations at cloud base, and to show how Z-R relationships change with height below the cloud base. The Z-R relationships are used in conjunction with shipborne C-band radar reflectivity data to estimate areal average precipitation with uncertainties at cloud base and at the surface. In the Sc drizzle Z-R relationship, Z = aRb (where a and b are constants), the estimated exponent b = 1.1 to 1.4 is lower than commonly observed in deep convective rain (b = 1.5). Analyses indicate that variations in Sc rain rates and reflectivities are influenced both by fluctuations in drizzle drop concentration and in mean radius, but that number concentration contributes more to the modulation of rain rate in Sc. Rain rates derived using the scanning C-band radar are found to be spatially variable, with much of the accumulation originating from a small fraction of the drizzling area. The observations also suggest that rain rate in marine Sc is strongly dependent on cloud liquid-water path, and inversely correlated with cloud droplet concentration. © Royal Meteorological Society, 2004."
"7005626683;7005928149;7005477332;57189585133;7201463831;7003621869;7102604282;7006705919;7004325649;56933322900;","Integrating and interpreting aerosol observations and models within the PARAGON framework",2004,"10.1175/BAMS-85-10-1523","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8444220514&doi=10.1175%2fBAMS-85-10-1523&partnerID=40&md5=8d9bdec8869a992aa3510480f50e967b","Constructing a measurement-based description of global tropospheric aerosols that effectively confronts and constrain global three-dimensional models is a challenge. The Progressive Aerosol Retrieval and Assimilation Global Observing Network (PARAGON) strategy is designed for this purpose. This progressive approach will make it possible to tackle problems of increasing difficulty, such as the incorporation of cloud observations, process models, and parameterization needed for understanding indirect effects, and the measurement of boundary-layer chemistry needed for understanding aerosol and gas interactions and their effects on air quality."
"7003371535;6603606681;56350405800;57200585664;6603292201;6602209873;6603630562;6602811538;7005732592;56865378100;6701519241;6701370189;6506423324;7005056279;7004061048;7402078417;6507198458;6507679962;7403362745;6603140753;","Observations and numerical simulations of the diurnal cycle of the EUROCS stratocumulus case",2004,"10.1256/qj.03.139","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844250565&doi=10.1256%2fqj.03.139&partnerID=40&md5=3ee4829d6e7846385bb329d744775f03","As part of the European Project on Cloud Systems in Climate Models, the diurnal cycle of stratocumulus has been simulated with Large-Eddy Simulation (LES) models and Single Column Models (SCMs). The models were initialized and compared with observations collected in marine stratocumulus in July 1987 during the First International Satellite Cloud Climatology Project Regional Experiment. The results of the six LES models are found to be in a fair agreement with the observations. They all capture the distinct diurnal variation in the cloud liquid-water path, the turbulence profiles and clearly show a decoupled boundary layer during daytime and a vertically well-mixed boundary layer during the night. Entrainment of relatively dry and warm air from just above the inversion into the boundary layer is the major process modifying the thermodynamic structure of the boundary layer during the night. The differences that arise in the liquid-water path evolution can therefore be attributed mainly to differences in the entrainment rate. The mean entrainment rates computed from the LES model results are 0.58 ± 0.08 cm s-1 and 0.36 ± 0.03 cm s-1 for the night-time and daytime periods, respectively. If the horizontal domain size in a LES model is enlarged, mesoscale fluctuations develop. This leads to a broader liquid-water path distribution and a reduction of the cloud albedo. To assess the quality of the representation of stratocumulus in general-circulation models, results from ten SCMs are compared with observations and LES results. The SCM latent and sensible heat fluxes at the surface agree fairly well with the LES results. Many of the SCMs predict a liquid-water path which is much too low, a cloud cover smaller than unity, and cloud tops that are lower than the observations and the LES results. This results in a much larger amount of downwelling short-wave radiation absorbed at the sea surface. Improvement of entrainment parametrizations is needed for a better representation of stratocumulus in SCMs. Observations and LES results of entrainment rate s for different stratocumulus cases are compared. The observed entrainment rates in Atlantic stratocumulus clouds during the Atlantic Stratocumulus Transition Experiment (ASTEX) are larger than for the ones over the Pacific Ocean off the coast of California. Results from LES models corroborate these findings. The differences in the entrainment rate can likely be attributed to the smaller inversion jumps of the liquid-water potential temperature for the ASTEX stratocumulus cases. © Royal Meteorological Society, 2004."
"6603630562;7402078417;6603140753;","Numerical simulation of the diurnal cycle of marine stratocumulus during FIRE - An LES and SCM modelling study",2004,"10.1256/qj.03.128","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844275218&doi=10.1256%2fqj.03.128&partnerID=40&md5=2ccebf61fd46b213e37839f041f9fc02","As part of the European Project on Cloud Systems in Climate Models (EUROCS), the stratocumulus-topped boundary layer has been simulated using the Max Planck Institute Large-Eddy Simulation (LES) model and the European Centre Hamburg Version Single Column Model (ECHAM-SCM). We have addressed the full diurnal cycle of stratocumulus off the coast of California based on observations of the First International Satellite Cloud Climatology Project Regional Experiment (FIRE). The results of the LES model demonstrate that the model is capable of reproducing the observed diurnal cycle of the boundary-layer structure reasonably well. In particular, the LES model reproduces the distinct diurnal variation in liquid-water path and of turbulence profiles due to the forcing imposed by the short-wave heating of the cloud layer. In addition, we have examined the sensitivity of our LES results with respect to the assumed values of various external environmental conditions. We found that the largest contribution to the variance of the LES-derived data products is due to the uncertainties in the cloud-top jumps of liquid-water potential temperature and total-water mixing ratio and to the net radiative forcing. To evaluate the quality of the representatio n of stratocumulus in a general circulation model, results from the standard ECHAM-SCM are contrasted with diagnostics from LES simulations. Results of the standard ECHAM-SCM reveal the following deficiencies: values of the liquid-water path are too low, and unreal-istically large levels of turbulent kinetic energy within the cloud layer are due to a numerical instability arising from a decoupling of radiative and diffusive processes. Based on these findings, the SCM has been revised. The modifications include the vertical advection scheme, the numerical treatment of diffusion and radiation, and the combination of the 1.5-order turbulent closure model with an explicit entrainment closure at the boundary-layer top in combination with a front tracking/capturing method. It is demonstrated that, with these modifications, the revised SCM produces a fair simulation of the diurnal cycle of the stratocumulus-topped boundary layer which is significantly improved compared to the one performed with the standard SCM. © Royal Meteorological Society, 2004."
"57185381300;24492458800;7003785403;7403003918;7102197206;7202505831;","A sensitivity study of daytime net radiation during snowmelt to forest canopy and atmospheric conditions",2004,"10.1175/1525-7541(2004)005<0774:ASSODN>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-9444277113&doi=10.1175%2f1525-7541%282004%29005%3c0774%3aASSODN%3e2.0.CO%3b2&partnerID=40&md5=5409246490aec9594b443dcda789b72e","This study investigates the dependence of net radiation at snow surfaces under forest canopies on the overlying canopy density. The daily sum of positive values of net radiation is used as an index of the snowmelt rate. Canopy cover is represented in terms of shortwave transmissivity and sky-view factor. The cases studied are a spruce forest in the Wolf Creek basin, Yukon Territory, Canada, and a pine forest near Fraser, Colorado. Of particular interest are the atmospheric conditions that favor an offset between shortwave energy attenuation and longwave irradiance enhancement by the canopy, such that net radiation does not decrease with increasing forest density. Such an offset is favored in dry climates and at high altitudes, where atmospheric emissivities are low, and in early spring when snow albedos are high and solar elevations are low. For low snow albedos, a steady decrease in snowmelt energy with increasing canopy cover is found, up to a forest density close to the actual densities of mature spruce forests. Snowmelt rates for high albedos are either insensitive or increase with increasing canopy cover. At both sites, foliage area indices close to 2 are associated with a minimum in net radiation, independent of snow albedo or cloud cover. However, these results are more uncertain for open forests because solar heating of trees may invalidate the longwave assumptions, increasing the longwave irradiance. © 2004 American Meteorological Society."
"7003893896;","The influence of Asian summer monsoon variability on the water balance of a Tibetan lake",2004,"10.1023/B:JOPL.0000042918.18798.cb","https://www.scopus.com/inward/record.uri?eid=2-s2.0-6944245344&doi=10.1023%2fB%3aJOPL.0000042918.18798.cb&partnerID=40&md5=416150864aa0d32d7159c92622dd3c9a","Past water-balance changes in Tibetan lakes are generally attributed to changes in the strength of the summer monsoon. However, the water balance of a lake reflects many different water fluxes, which are controlled by many climatic and hydrologic processes. In this research, weather data and evaporation models are used to determine the climatic cause of a recent water-balance change in Ahung Co, a lake in central Tibet. Between 1995 and 2001, lake level rose at least 20 cm and the lake began to overflow. Results indicate that an increase in summer monsoon precipitation over the lake and drainage basin is responsible for the rise in lake level. Stronger monsoon conditions between 1995 and 2001 also led to decreased lake evaporation and basin evapotranspiration due to increased clouds and humidity. This contributed to the rise in lake level, but to a much smaller extent than the increase in monsoon precipitation. Lake evaporation during the spring and fall was also reduced between 1995 and 2001 due to longer lasting ice cover. Variations in ice cover play a small role in the overall water balance of Ahung Co, however, because the lake area is small compared to the drainage basin area. If these results hold true for the past, water-balance fluctuations inferred from the geochemistry of sediments from Ahung Co provide a record of variations in monsoon precipitation during the Holocene."
"7005135473;57203378050;","Cloud-free shortwave aerosol radiative effect over oceans: Strategies for identifying anthropogenic forcing, from Terra satellite measurements",2004,"10.1029/2004GL020510","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10644295575&doi=10.1029%2f2004GL020510&partnerID=40&md5=f61122f2983f10d25101d76dcaece210","Using the Single Scanner Footprint (SSF) data that combines the multi-spectral Moderate Resolution Imaging Spectroradiometer (MODIS) cloud and aerosol products with the Clouds and the Earth's Radiant Energy System (CERES) top of atmosphere broadband radiative fluxes, we first provide observational estimates of the instantaneous cloud-free shortwave aerosol radiative forcing (SWARF) over the global oceans. Different from our previous research, we corrected for both the sample biases and the diurnal cycle of SWARF and the cloud-free diurnally averaged SWARF is -5.3 ± 1.7 Wm-2, a value that is consistent with previous studies. Furthermore, we partition the CERES shortwave flux as a function of MODIS aerosol optical thickness and the fraction of fine mode aerosol to the total aerosol optical depth (η . Since η is related to particle size and is a good surrogate for aerosol type, we present strategies for estimating the radiative forcing of anthropogenic aerosols from MODIS and CERES measurements that is important for quantifying the climate forcing of aerosols. Copyright 2004 by the American Geophysical Union."
"55727417500;36952888700;7003975505;","Ocean circulation and climate in an idealised Pangean OAGCM",2004,"10.1029/2004GL020643","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10644278789&doi=10.1029%2f2004GL020643&partnerID=40&md5=601b0eae7c1a64e0ae894f690b0020f1","An idealised Pangean configuration is integrated in a coupled ocean atmosphere general circulation model to investigate the form of the ocean circulation and its impacts on the large scale climate system. A vigorous, hemispherically symmetric overturning is found, driven by deep water formation at high latitudes. Whilst the peak mass transport is around 100 Sv, a low vertical temperature gradient in the ocean means that the maximum heat transport is only 1.2 PW. The geographical change in the coupled model is found to produce a global average warming of 2°C, despite an increase in global surface albedo. This occurs through changes in the atmospheric water vapour and cloud distributions. There is also reduction in the equator-pole temperature gradient, largely attributable to the same causes, avoiding the paradox of low meridional temperature gradients without increased polar heat transport. Copyright 2004 by the American Geophysical Union."
"6507343578;7102577095;","Stochastic theory of radiative transfer through generalized cloud fields",2004,"10.1029/2004JD004524","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10244247779&doi=10.1029%2f2004JD004524&partnerID=40&md5=dcad89af10610d0b3d8119be0c93e084","We present a coherent treatment, based on linear kinetic theory, of stochastic radiative transfer in an atmosphere containing clouds. A brief summary of statistical cloud radiation models is included. We explore the sensitivities inherent in the stochastic approach by using a well-known plane-parallel model developed by Fouquart and Bonnel together with our own stochastic model which generalizes earlier work of F. Malvagi, R. N. Byrne, G. C. Pomraning, and R. C. J. Somerville. In overcast conditions, in comparison to the plane parallel model, the stochastic model underestimates transmittance at small optical depths (<7) and overestimates transmittance at large optical depths. The stochastic model is strongly sensitive to cloud optical properties, including cloud water content and cloud droplet effective radius. The extension of the stochastic approach to an atmospheric general circulation model parameterization appears to be most appropriate for cloud fraction ranging from 25 to 70%. We conclude that stochastic theory holds substantial promise as a modeling approach for calculating shortwave radiative transfer through partially cloudy fields. Unlike cloud-resolving models and Monte Carlo cloud models, stochastic cloud models do not depend on specific realizations of the cloud field. Instead, they calculate the transfer of radiation through a cloudy atmosphere whose properties are known statistically in the form of probability density functions characterizing cloud geometry and cloud optical properties. The advantage of the stochastic approach is its theoretical generality and its potential for representing a complex cloud field realistically at modest computational cost. Copyright 2004 by the Geophysical Union."
"7202516876;7003591311;","A modeling study of the effect of nitric acid on cloud properties",2004,"10.1029/2004JD004750","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10244236527&doi=10.1029%2f2004JD004750&partnerID=40&md5=b31cc9815a6015faa69610145b778a2b","The effect of nitric acid (HNO<inf>3</inf>) on cloud microphysical and radiative properties is studied using an adiabatic cloud parcel model for a range of aerosol size distributions, different water vapor mass accommodation coefficients, and HNO<inf>3</inf> concentrations. Results show that HNO<inf>3</inf> not only increases cloud drop number concentration N<inf>d</inf>, but also leads to significantly broader droplet size spectra at both the small- and large-size ends. The broader spectra are generally the result of competition for H<inf>2</inf>O and HNO<inf>3</inf> among the polydisperse droplets. The increase in the number of activated cloud droplets in the presence of HNO<inf>3</inf>, and the deactivation of some of the small cloud droplets due to the outgasing of HNO<inf>3</inf>, lead to spectral broadening at the small-size end. At the large-size end the broadening is caused by an increase in the driving force for growth. For small drops the driving force tends to be decreased by the presence of HNO<inf>3</inf>. Although N<inf>d</inf> increases with increasing HNO<inf>3</inf> concentration, the increases in cloud optical depth and albedo due to HNO<inf>3</inf> cannot necessarily be predicted by the commonly used relationships for cloud optical properties. The dependence of the cloud optical depth on N<inf>d</inf> to the one-third power is shown to be an overestimate because droplet spectra are significantly broadened by HNO<inf>3</inf>. We show that broadening effects due to HNO<inf>3</inf> and other chemical or microphysical factors need to be considered when estimating cloud optical properties and their effect on climate."
"7201443624;7003976079;6507890592;7004034323;","Simulation of the Earth's radiation budget by the European centre for medium-range weather forecasts 40-year reanalysis (ERA40)",2004,"10.1029/2004JD004816","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10244264723&doi=10.1029%2f2004JD004816&partnerID=40&md5=8f4d1df5eb6ef7293dd17a22a56ea53a","The radiation budget simulated by the European Centre for Medium-Range Weather Forecasts (ECMWF) 40-year reanalysis (ERA40) is evaluated for the period 1979-2001 using independent satellite data and additional model data. This provides information on the quality of the radiation products and indirect evaluation of other aspects of the climate produced by ERA40. The climatology of clear-sky outgoing longwave radiation (OLR) is well captured by ERA40. Underestimations of about 10 W m-2 in clear-sky OLR over tropical convective regions by ERA40 compared to satellite data are substantially reduced when the satellite sampling is taken into account. The climatology of column-integrated water vapor is well simulated by ERA40 compared to satellite data over the ocean, indicating that the simulation of downward clear-sky longwave fluxes at the surface is likely to be good. Clear-sky absorbed solar radiation (ASR) and clear-sky OLR are overestimated by ERA40 over north Africa and high-latitude land regions. The observed interannual changes in low-latitude means are not well reproduced. Using ERA40 to analyze trends and climate feedbacks globally is therefore not recommended. The all-sky radiation budget is poorly simulated by ERA40. OLR is overestimated by around 10 W m-2 over much of the globe. ASR is underestimated by around 30 W m -2 over tropical ocean regions. Away from marine stratocumulus regions, where cloud fraction is underestimated by ERA40, the poor radiation simulation by ERA40 appears to be related to inaccurate radiative properties of cloud rather than inaccurate cloud distributions. Copyright 2004 by the American Geophysical Union."
"7005327054;","A model for simulation of the climate and hydrology of the Great Lakes basin",2004,"10.1029/2004JD004602","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10344263949&doi=10.1029%2f2004JD004602&partnerID=40&md5=90f8cb336459ceb9ef17a5b4b49b51d0","The Coupled Hydrosphere-Atmosphere Research Model (CHARM) was developed by coupling the Regional Atmospheric Modeling System (RAMS) to models of the land hydrology of the Great Lakes basin and of the evaporation and thermodynamics of the Great Lakes. It is intended for running coupled atmosphere-surface climate scenarios for the Great Lakes basin, to gain a perspective that has been missed by running hydrologic models in off-line mode, driven by the output of global general circulation models. This paper presents validation of this model using historical atmospheric data to drive the regional embedded CHARM model. The current version of CHARM simulates the near-surface air temperature in the region quite well, with some positive bias during the winter and negative bias during the summer. Biases in the temperature averaged over 1 month and over the portion of the domain that is not directly forced by observations are less than or approximately 2 K. The annual precipitation has a positive bias of 6.6% and does well at placing the lake-effect precipitation areas, but may have too strong a west-east gradient. Simulation of annually averaged runoff meets well with expectations, but additional empirical fitting may be required to replicate the seasonal cycle. Aspects of the model that remain troublesome are the tendency for unrealistically low pressure at mean sea level and for persistent heavy low stratus clouds."
"7101959253;7005626683;","Evaluation of radiometric measurements from the NASA Multiangle Imaging Spectroradiometer (MISR): Two- and three-dimensional radiative transfer modeling of an inhomogeneous stratocumulus cloud deck",2004,"10.1029/2004JD004710","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10244222767&doi=10.1029%2f2004JD004710&partnerID=40&md5=7574df4c729f4a2dd8f57655f7e68a21","In December 1999, NASA launched the Terra satellite. This platform carries five instruments that measure important properties of the Earth climate system. One of these instruments is the Multiangle Imaging Spectroradiometer, or MISR. This instrument measures light reflected from the Earth at a spatial resolution of 275-1100 m, at four wavelengths (446, 558, 672, and 866 nm), and at nine different viewing angles that vary from +70 to -70 degrees along the direction of flight [Diner et al., 2002]. These multiangle data have the potential to provide information on aerosols, surface, and, cloud characteristics that compliments traditional single-view-direction satellite measurements. Before this potential can be realized, the accuracy of the satellite radiance measurements must be carefully assessed, and the implications of the radiometric accuracy on remote-sensing algorithms must be evaluated. In this article, we compare MISR multiangle measurements against two-dimensional (2-D) and 3-D radiative transfer calculations from an inhomogeneous cloud scene. Inputs to the radiative transfer code are based entirely on independently gathered data (ground-based radar, lidar, microwave radiometer, in situ aircraft data, etc.). The 2-D radiative transfer calculations compare favorably near nadir and, in most of the forward scattering directions, but differ by as much as 10% in the backscattering directions. Using 3-D radiative transfer modeling, we show that this difference is due to the 3-D structure of the cloud deck, including variations in the cloud top height on scales less than 275 m, which are not resolved in the 2-D simulations. Comparison of the 2-D calculations to the MISR measurements, after accounting for the 3-D structure, show residual differences that are less than 4% at all angles at the MISR blue and green wavelengths. The comparison also reveals that the MISR measurements at the red and near-infrared wavelengths are too bright relative to measurements in the blue and green bands. On the basis of the results of this study, along with results from five other comparisons, the MISR calibration is being adjusted to reduce the red and near-infrared radiances."
"7004377832;6701599465;6603925178;6603233146;","New evidence for an ENSO impact on low-latitude glaciers: Antizana 15, Andes of Ecuador, 0°28'S",2004,"10.1029/2003JD004484","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10244251636&doi=10.1029%2f2003JD004484&partnerID=40&md5=c6d3951182a2c96fb1fac074a7c00886","Continuous monthly mass balance measurements from the ablation zone of Antizana 15 glacier in the Andes of Ecuador between January 1995 and December 2002 indicate a strong dependence on El Niño-Southern Oscillation (ENSO). Over the 8-year period investigated, mass balance was negative all year round during El Niño periods but remained close to equilibrium (positive anomalies) during La Niña events. On seasonal timescales, mean ablation rates remain at a quite constant level all year round, but interannual variability shows much larger changes from year to year during the key periods February May and September. This variability is caused by large differences that occur in the seasonal cycle during the two opposite phases of ENSO. Since ENSO is phase locked to the seasonal cycle with largest sea surface temperature anomalies around boreal winter, November-February, and the atmospheric response to ENSO is delayed by 3 months over the Ecuadorian Andes, year-to-year variations in mass balance are largest between February and May. Energy balance studies at the glacier surface indicate that high air temperature, which favors rain over snowfall, weak and sporadic snowfall, insufficient to maintain a high glacier albedo, low wind speeds, which limit the transfer of energy from melting to sublimation, and reduced cloud cover, which increases the incoming short-wave radiation, are the dominant factors related to El Niño, which tend to increase ablation. La Niña events on the other hand are characterized by colder temperatures, higher snowfall amounts, and to a lesser 1degree, more constant winds, factors which increase albedo and sublimation and therefore preclude melting at the glacier surface. The effects of ENSO variability are also important over the accumulation area, which represents up to 80% of the glacier surface during La Niña events (1999-2000) and 45-60% in El Niño years. Since the accumulation rates increase during these cold periods, the specific net balance and the dynamics of the entire glacier are strongly affected. Longer mass balance records than this 8-year period are needed for conclusive answers about the dependence of the Ecuadorian glaciers on ENSO variability, but initial results suggest that the response observed on Antizana glaciers is very similar to what has been observed previously during ENSO periods on Andean glaciers in the outer tropics. The seasonal dependence on ENSO and the physical mechanisms linking ENSO with mass balance variations on Antizana, however, are different from the response observed on Andean glaciers in the outer tropics. Copyright 2004 by the American Geophysical Union."
"36149741000;56284545500;8979277400;36842329100;7003967390;55619302076;7102857642;","Far-reaching effects of the Hawaiian Islands in the CCSR/NIES/FRCGC high-resolution climate model",2004,"10.1029/2004GL020907","https://www.scopus.com/inward/record.uri?eid=2-s2.0-9744257981&doi=10.1029%2f2004GL020907&partnerID=40&md5=7d8378e8be166a773184dea3132d74f8","For the first time, using a high-resolution atmosphere-ocean coupled general circulation model (CGCM), we succeed in reproducing the far-reaching effects of the Hawaiian Islands, recently showed by satellite observations. The model reproduces the distributions of sea surface temperature (SST), surface winds and cloud liquid water (CLW) in the wake of the Hawaiian Islands. It is revealed that these distributions are caused by the Hawaiian Lee Counter Current (HLCC) and that this current is driven by the wind-curls induced by the orographic effect of the islands, as suggested from an observational study. It is also shown that wind changes around the Hawaiian Islands can further affect the speed of the North Equatorial Current (NEC) and SST over the current, and intra-annual variability in CLW to the west of the islands is governed, not only by SST bur also by wind speed. Copyright 2004 by the American Geophysical Union."
"7202216319;57203055233;7006635125;57196170962;","Impact of a convectively forced gravity wave drag parameterization in NCAR CCM3",2004,"10.1175/1520-0442(2004)017<3530:IOACFG>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7044246100&doi=10.1175%2f1520-0442%282004%29017%3c3530%3aIOACFG%3e2.0.CO%3b2&partnerID=40&md5=73c06825472beb8bdaf10c71d09ac434","A parameterization of gravity wave drag forced by subgrid-scale cumulus convection (GWDC) proposed by Chun and Baik is implemented into the National Center for Atmospheric Research Community Climate Model (NCAR CCM3) and its effect on perpetual January and July climate is investigated. The cloud-top gravity wave stress is concentrated in the intertropical convergence zone where persistent deep cumulus clouds exist. The resultant zonal wind acceleration due to the breaking of convectively forced gravity waves is predominantly found in the tropical lower stratosphere with westerly acceleration above cloud top and easterly acceleration just below it. Since the parameterized gravity waves are stationary relative to convective clouds, wave breaking occurs mainly in the tropical lower stratosphere where the zonal wind is weak enough for wave saturation. It is shown that the GWDC parameterization significantly alleviates the systematic model biases of zonal-mean zonal wind and temperature. In particular, excessive easterlies in the tropical stratosphere and excessive cold temperatures in the tropical lower stratosphere are reduced by more than 50% by including the GWDC parameterization. The horizontal wind divergence field in the tropical upper troposphere and lower stratosphere is also significantly improved with the GWDC parameterization. The impact of the GWDC parameterization extends to mid- to high latitudes through planetary wave activity in the winter hemisphere. The increased amplitude of zonal wavenumber 3 in the January Northern Hemisphere and the increased amplitude of zonal wavenumber 2 in the July Southern Hemisphere lead to significant improvements in model performance. The impact of the GWDC parameterization on Eliassen-Palm (EP) flux divergence forcing by stationary waves is generally opposite to that by transient waves in the extratropics, especially in the Northern Hemisphere wintertime. Hence, the zonal-mean zonal wind change by the GWDC parameterization occurs mainly in the Tropics by direct gravity wave drag forcing. © 2004 American Meteorological Society."
"57208346904;57142763300;7005691764;7003961970;14038431700;","Regional climate model simulation of U.S. precipitation during 1982-2002. Part I: Annual cycle",2004,"10.1175/1520-0442(2004)017<3510:RCMSOU>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7044264890&doi=10.1175%2f1520-0442%282004%29017%3c3510%3aRCMSOU%3e2.0.CO%3b2&partnerID=40&md5=c221875e7d2eeb945357b64d9e85c415","The fifth-generation PSU-NCAR Mesoscale Model (MM5)-based regional climate model (CMM5) capability in simulating the U.S. precipitation annual cycle is evaluated with a 1982-2002 continuous baseline integration driven by the NCEP-DOE second Atmospheric Model Intercomparison Project (AMIP II) reanalysis. The causes for major model biases (differences from observations) are studied through supplementary seasonal sensitivity experiments with various driving lateral boundary conditions (LBCs) and physics representations. It is demonstrated that the CMM5 has a pronounced rainfall downscaling skill, producing more realistic regional details and overall smaller biases than the driving global reanalysis. The precipitation simulation is most skillful in the Northwest, where orographic forcing dominates throughout the year; in the Midwest, where mesoscale convective complexes prevail in summer; and in the central Great Plains, where nocturnal low-level jet and rainfall peaks occur in summer. The actual model skill, however, is masked by existing large LBC uncertainties over datapoor areas, especially over oceans. For example, winter dry biases in the Gulf States likely result from LBC errors in the south and east buffer zones. On the other hand, several important regional biases are identified with model physics deficiencies. In particular, summer dry biases in the North American monsoon region and along the east coast of the United States can be largely rectified by replacing the Grell with the Kain-Fritsch cumulus scheme. The latter scheme, however, yields excessive rainfall in the Atlantic Ocean but large deficits over the Midwest. The fall dry biases over the lower Mississippi River basin, common to all existing global and regional models, remain unexplained and the search for their responsible physical mechanisms will be challenging. In addition, the representation of cloud-radiation interaction is essential in determining the precipitation distribution and regional water recycling, for which the new scheme implemented in the CMM5 yields significant improvement. © 2004 American Meteorological Society."
"6701656335;","Precipitation, cloud cover and Forbush decreases in galactic cosmic rays",2004,"10.1016/j.jastp.2004.05.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3543099181&doi=10.1016%2fj.jastp.2004.05.010&partnerID=40&md5=8227f22e164dc903a67105ea5ac2f431","The results of a study to explore variations in cloud cover, over regions that are minimally affected by rainfall and heavy rainfall, and that are coincident with variations in the galactic cosmic ray flux, are presented. Using an extensive record of global satellite derived cloud and rainfall products from the International Satellite Cloud Climatology Project D1 data series and Xie and Arkin (J. Climate 9 (1996) 840), epoch superposition analysis of a sample of events of short term decreases in the galactic cosmic ray flux, is conducted. Analysis of data that is largely free from the influence of rainfall and heavy rainfall, averaged over 10-degree geomagnetic latitude (φ) bands reveals that cloud cover is reduced at high latitudes, and at middle and lower (including equatorial) latitudes over regions of relatively higher cloud cover, over both land and ocean surfaces, while increasing over ocean surfaces at middle and lower latitudes in regions of thinner cloud. © 2004 Elsevier Ltd. All rights reserved."
"7005035762;","Springtime arctic mixed-phase cloud",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-5644270245&partnerID=40&md5=1677240a8900739460d975244a109a10","The microphysical characteristics, radiative impact, and lifecycle of a long-lived, liquid and ice surface-based mixed-layer cloud with an average temperature of -20°C were examined. It was observed that the cloud's radiative (flux) impact is close to that of an all-liquid cloud, but the ice can indirectly regulate the cloud's total optical depth. Overall, the results imply that the impact of arctic clouds upon the surface energy budget can only be understood if both the underlying cloud microphysical processes and their dependence upon large-scale dynamics are known."
"55717244800;7003833060;","Marine low-cloud anomalies associated with ENSO",2004,"10.1175/1520-0442(2004)017<3448:MLAAWE>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4444258240&doi=10.1175%2f1520-0442%282004%29017%3c3448%3aMLAAWE%3e2.0.CO%3b2&partnerID=40&md5=71bc3eb787a2a4357f9cfb20487981d2","As a contribution to understanding the possible impact of altered climate regimes on marine clouds, and hence on cloud radiative forcing, ship-observed marine low clouds and precipitation frequency for individual seasons are regressed at zero lag on an index of El Niño-Southern Oscillation (ENSO) for the period December 1955-January 1996 for ocean areas between 40°S and 70°N. Seasonal anomalies of atmospheric circulation parameters, static stability, and SST are also examined in order to illuminate physical mechanisms responsible for observed ENSO cloud variations. The following extratropical regions exhibit significant ENSO cloud anomalies and are discussed in detail: winter-spring North Pacific, summer North Pacific, winter western North Atlantic, autumn northeastern Atlantic, and western Mediterranean Sea. In all of these regions except the summer North Pacific, cloud anomalies are related to jet stream and storm track anomalies associated with atmospheric teleconnection patterns. The summer North Pacific anomalies are also connected with jet stream and storm track anomalies, but these are associated with a persistent SST anomaly rather than an atmospheric teleconnection. ENSO anomalies in the western and eastern equatorial Pacific are analyzed in greater detail than in previous work, as well as those in the Arabian Sea during winter and summer monsoons. With the exception of the Arabian Sea region in winter, cloud anomalies are consistently related to 1) changes in storm tracks and/or 2) changes in low-level static stability and temperature advection. © 2004 American Meteorological Society."
"8859530100;55745955800;","Evaluation of clouds and their radiative effects simulated by the NCAR community atmospheric model against satellite observations",2004,"10.1175/1520-0442(2004)017<3302:EOCATR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5444257881&doi=10.1175%2f1520-0442%282004%29017%3c3302%3aEOCATR%3e2.0.CO%3b2&partnerID=40&md5=7c08577051197b3f97998c83e13a8baa","Cloud climatology and the cloud radiative forcing at the top of the atmosphere (TOA) simulated by the NCAR Community Atmospheric Model (CAM2) are compared with satellite observations of cloud amount from the International Satellite Cloud Climatology Project (ISCCP) and cloud forcing data from the Earth Radiation Budget Experiment (ERBE). The comparison is facilitated by using an ISCCP simulator in the model as a runtime diagnostic package. The results show that in both winter and summer seasons, the model substantially underestimated total cloud amount in the storm tracks and in the subtropical dry regions of the two hemispheres, and it overestimated total cloud amount in the tropical convection centers. The model, however, simulates reasonable cloud radiative forcing at the TOA at different latitudes. The differences of cloud vertical structures and their optical properties are analyzed between the model and the data for three regions selected to represent the storm tracks: the convective Tropics and the subtropical subsidence regions. Major cloud biases are identified as follows: the model overestimated high thin cirrus, high-top optically thick clouds, and low-top optically thick clouds, while it significantly underestimated middle- and low-top clouds with intermediate and small optical thickness. These multiple cloud biases compensate for each other to produce reasonable cloud forcing in the following way: for the longwave cloud forcing, excessive high clouds compensate for significantly deficient middle and low clouds; for the shortwave cloud forcing, excessive optically thick clouds offset significantly deficient optically intermediate and thin clouds. Possible causes of model biases are discussed. © 2004 American Meteorological Society."
"7103274591;6603589501;7006478660;7102031571;7004479957;7102643810;7006874359;7005772154;22958319200;7005035762;","EPIC2001 and the coupled ocean-atmosphere system of the tropical east Pacific",2004,"10.1175/BAMS-85-9-1341","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5644275477&doi=10.1175%2fBAMS-85-9-1341&partnerID=40&md5=dd1d96626d525e47fcbed5aee59ea7bb","East Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System 2001 (EPIC2001) is a field experiment initiated to provide the observational basis needed to improve the representation of certain key physical processes in models. In addition to physical processes, EPIC2001 research is directed toward a better understanding and simulation of the effects of short-term variability in the east Pacific on climate. This variability is important in the region because conditions in the intertropical convergence zone are highly variable on daily to intraseasonal time scales. The effects of such variability rectify strongly onto climate time scales in this region."
"7202803069;6701656335;","Short-term variability in satellite-derived cloud cover and galactic cosmic rays: An update",2004,"10.1016/j.jastp.2004.05.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3543071052&doi=10.1016%2fj.jastp.2004.05.002&partnerID=40&md5=577fa170f2344021a8cc97034e3a93f7","Previous work by Todd and Kniveton (TK2001) (J. Geophys. Res. 106(D23) (2001) 32031) has indicated a statistically significant association (at the daily timescale) between short-term reductions in galactic cosmic rays, specifically Forbush decrease (FD) events, and reduced cloud cover, mainly over Antarctica (as recorded in International Satellite Cloud Climatology Project (ISCCP) D1 data). This study presents an extension of the previous work using an extended dataset of FD events and ISCCP cloud data over the period 1983-2000, to establish how stable the observed cloud anomalies are. Composite analysis of ISCCP data based on a sample of 32 FD events (excluding those coincident with solar proton events) indicates cloud anomalies with a very similar space/time structure to that previously reported, although of smaller magnitude. Substantial reductions in high level cloud (up to 12% for zonal mean, compared to 18% reported by TK2001) are observed over the high geomagnetic latitudes, especially of the southern hemisphere immediately following FD event onset. Largest anomalies are centred on the Antarctic plateau region during austral winter. However, the largest cloud anomalies occur where the accuracy of the ISCCP cloud retrievals is likely to be lowest, such that the results must be treated with extreme caution. Moreover, significant positive composite mean surface and tropospheric temperature anomalies centred over the same region are also observed for the FD sample from the National Center for Environmental Prediction (NCEP) reanalysis data. Such increased temperatures are inconsistent with the radiative effect of a reduction in high-level cloud during local winter. Overall, the results do not provide strong evidence of a direct galactic cosmic ray/cloud association at short timescales. The results highlight (a) the potential problems of data quality in the high latitude regions (b) the problems inherent in inferring cause and effect relationships from observational data alone (c) the need for further research to test competing hypotheses. © 2004 Elsevier Ltd. All rights reserved."
"9233435600;6602729251;7202162685;","Vertical heat transfer over the arctic ocean",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-5644303231&partnerID=40&md5=5138fc008d2ab532ad9cf2a988642a31","Vertical heat transfer through the lower atmosphere during clear-sky conditions is observed from analysis of data focused on the climatic implications of arctic clouds and their interaction with the surface. The analyis demonstrates that the most plausible mechanism for balancing the heat loss to the surface is vertical advection of heat within the inversion layer, resulting from weak subsidence acting on the strong temperature inversion. The turbulence responsible for the entrainment of this heat into the boundary layer and its downward transport to the surface is maintained by wind shear and wave processes.The downward flow of heat represents important components of the heat budgets of the lower atmosphere and ice-pack surface, with potential implications for the ice-pack mass balance as well."
"23091439900;6506097974;57189252351;","El Niño and La Niña in highly reflective cloud",2004,"10.1175/1520-0442(2004)017<3470:ENALNI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5444241867&doi=10.1175%2f1520-0442%282004%29017%3c3470%3aENALNI%3e2.0.CO%3b2&partnerID=40&md5=ff5441206e4ad47dd66fcaf8e9b36b5e","Over the last two decades, several scientists have used Garcia's record of highly reflective cloud (HRC) to study the El Niño-Southern Oscillation (ENSO). Recently Waliser and Zhou removed a satellite bias. This note describes a test for the presence of the ENSO signal in the corrected record. The test treats anomaly values of corrected HRC in a grid that covers the equatorial western Pacific Ocean. For each box in the grid, the HRC anomaly was averaged over El Niño events in the record. From the averages, a map of the El Niño HRC anomaly was made. Similarly, a map of the La Niña HRC anomaly was made. Each map shows a strong, east-southeastwest-northwest trending dipole. The El Niño dipole dips toward the west-northwest, implying excess cloud in the east-southeast; the La Niña dipole dips toward the east-southeast, implying excess cloud in the west-northwest. In respect to these dipoles, the pair of HRC anomaly maps closely resembles published ENSO rain anomaly maps. The mapping was repeated for the part of the HRC record that overlaps a record of outgoing longwave radiation (OLR). Composite maps of OLR contain dipoles opposite in sign to the HRC dipoles. Together with the OLR comparison, the test reveals a robust ENSO in the Garcia and Waliser-Zhou records of HRC. The presence of ENSO supports the use of corrected HRC for studies of more subtle interannual signals. © 2004 American Meteorological Society."
"6603293528;7102521545;10042470700;7403233451;6701346974;7202208382;","Effects of model resolution and subgrid-scale physics on the simulation of precipitation in the continental United States",2004,"10.1007/s00382-004-0440-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5044220145&doi=10.1007%2fs00382-004-0440-y&partnerID=40&md5=658444c90ee3c629cb4e1240cbb34d9b","We analyze simulations of the global climate performed at a range of spatial resolutions to assess the effects of horizontal spatial resolution on the ability to simulate precipitation in the continental United States. The model investigated is the CCM3 general circulation model. We also preliminarily assess the effect of replacing cloud and convective parameterizations in a coarse-resolution (T42) model with an embedded cloud-system resolving model (CSRM). We examine both spatial patterns of seasonal-mean precipitation and daily time scale temporal variability of precipitation in the continental United States. For DJF and SON, high-resolution simulations produce spatial patterns of seasonal-mean precipitation that agree more closely with observed precipitation patterns than do results from the same model (CCM3) at coarse resolution. However, in JJA and MAM, there is little improvement in spatial patterns of seasonal-mean precipitation with increasing resolution, particularly in the southeast USA. This is because of the dominance of convective (i.e., parameterized) precipitation in these two seasons. We further find that higher-resolution simulations have more realistic daily precipitation statistics. In particular, the well-known tendency at coarse resolution to have too many days with weak precipitation and not enough intense precipitation is partially eliminated in higher-resolution simulations. However, even at the highest resolution examined here (T239), the simulated intensity of the mean and of high-percentile daily precipitation amounts is too low. This is especially true in the southeast USA, where the most extreme events occur. A new GCM, in which a cloud-resolving model (CSRM) is embedded in each grid cell and replaces convective and stratiform cloud parameterizations, solves this problem, and actually produces too much precipitation in the form of extreme events. However, in contrast to high-resolution versions of CCM3, this model produces little improvement in spatial patterns of seasonal-mean precipitation compared to models at the same resolution using traditional parameterizations. © Springer-Verlag 2004."
"7401742385;7006720318;7007129227;","A dynamic GIS-multicriteria technique for siting the NASA-Clark Atlanta urban rain gauge network",2004,"10.1175/1520-0426(2004)021<1346:ADGTFS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5044237705&doi=10.1175%2f1520-0426%282004%29021%3c1346%3aADGTFS%3e2.0.CO%3b2&partnerID=40&md5=8eedc790f5ae82e94ea7e5984538c330","Because Atlanta, Georgia, is a model of rapid transition from forest/agriculture land use to urbanization, NASA and other agencies have initiated programs to identify and understand how urban heat islands (UHIs) impact the environment in terms of land use, air quality, health, climate, and other factors. Atlanta's UHI may also impact the regional water cycle by inadvertent forcing of precipitating cloud systems. Yet, a focused assessment of the role of urban-induced rainfall in Atlanta has not been a primary focus of past efforts. Several observational and climatological studies have theorized that UHIs can have a significant influence on mesoscale circulations and resulting convection. Using spaceborne rain radar and a limited network of irregularly spaced, ground-based rain gauges, evidence that the Atlanta and Houston, Dallas, and San Antonio, Texas, urban areas may modify cloud and precipitation development was recently found. To validate these recent satellite-based findings, it was determined that a higher density of rainfall gauges would be required for future work. The NASA-sponsored Study of Precipitation Anomalies from Widespread Urban Landuse (SPRAWL) seeks to further address the impact of urban Atlanta on precipitation variability by implementing a dense rain gauge network to validate spaceborne rainfall estimates. To optimize gauge location to a given set of criteria, a geographical information system (GIS) aided by a spatial decision support system (DSS) has been developed. A multicriteria decision analysis (MCDA) technique was developed to locate optimal sites in accordance to the guidelines defined by the World Meteorological Organization (WMO). A multicriteria analysis model for the optimization of prospective sites was applied to identify prime locations for the tipping-bucket rain gauges. The MCDA design required development of a spatial model by applying a series of linear programming methods, with the aid of spatial analytical techniques, in order to identify land sites that meet a particular set of criteria. © 2004 American Meteorological Society."
"7004111620;22985172300;","Temperature alterations on the Antarctic ice sheet initiated by the disturbed solar wind",2004,"10.1016/j.jastp.2004.05.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3543128269&doi=10.1016%2fj.jastp.2004.05.005&partnerID=40&md5=733b9edfbbdd5bf000c38e15182868bd","The temperature observations made by the automatic weather stations (AWS) at Dome C II and South Pole (ftp://amrc.ssec.wisc.edu/pub/aws/10min/rdr/) and by automatic meteorological station MILOS at Vostok provided the basis of the analysis. The hourly values of the temperature deviations (ΔT) have been derived from these measurements for winter season (May-September) of 2000-2001. These values were compared with the hourly solar wind characteristics, such as interplanetary electric field and the solar wind dynamic pressure, the time of the maximum deviation in a proper solar wind parameter being determined as a key moment. Results of our analysis confirm the conclusion of Troshichev et al. (J. Atmos. Solar-Terr. Phys. 65 (2003) 947), that large increases the interplanetary dawn-dusk electric field influence the warming effect on the ground level in the Central Antarctica. However, extent of the solar wind influence on the atmospheric temperature turned out to be highly different at various sites of the ice sheet: while the temperature response at Dome C II is like to Vostok station, the only slight tendency is displayed at South Pole. The conclusion is made that difference in the temperature effects at Vostok and Dome C II, on the one hand, and South Pole, on the other hand, is determined by different disposition of stations within the katabatic system of circulation. As the pattern of near-surface katabatic winds (Nature 328 (1987) 51) shows, the both stations, Vostok and Dome C II, are situated in zone of Central Antarctic ridge, where the drainage winds take origin. On the contrary, South Pole is out of the Antarctic ridge, in area of the developed drainage winds. It is suggested that the interplanetary electric field influences the katabatic system of atmospheric circulation, typical of the winter Antarctic, by means the global electric circuit affecting clouds and hence the radiation dynamics of the troposphere. © 2004 Elsevier Ltd. All rights reserved."
"7203055935;7202640224;","Seasonal evolution and variability associated with the West African monsoon system",2004,"10.1175/1520-0442(2004)017<3364:SEAVAW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5444231779&doi=10.1175%2f1520-0442%282004%29017%3c3364%3aSEAVAW%3e2.0.CO%3b2&partnerID=40&md5=26e5bf324aa8d9cae7e57136261ea42c","In this study, the seasonal variations in surface rainfall and associated large-scale processes in the tropical eastern Atlantic and West African region are investigated. The 6-yr (1998-2003) high-quality Tropical Rainfall Measuring Mission (TRMM) rainfall, sea surface temperature (SST), water vapor, and cloud liquid water observations are applied along with the NCEP-NCAR reanalysis wind components and a 4-yr (2000-2003) Quick Scatterometer (Quik SCAT) satellite-observed surface wind product. Major mean rainfall over West Africa tends to be concentrated in two regions and is observed in two different seasons, manifesting an abrupt shift of the mean rainfall zone during June-July: (i) near the Gulf of Guinea (about 5°N), intense convection and rainfall are seen during April-June and roughly follow the seasonality of SST in the tropical eastern Atlantic, and (ii) along the latitudes of about 10°N over the interior of the West African continent, a second intense rain belt begins to develop in July and remains there during the later summer season. This belt coexists with a northward-moving African easterly jet (AEJ) and its accompanying horizontal and vertical shear zones, the appearance and intensification of an upper-tropospheric tropical easterly jet (TEJ), and a strong low-level westerly flow. Westward-propagating wave signals [i.e., African easterly waves (AEWs)] dominate the synoptic-scale variability during July-September, in contrast to the evident eastward-propagating wave signals during May-June. The abrupt shift of the mean rainfall zone thus turns out to be a combination of two different physical processes: (i) evident seasonal cycles in the tropical eastern Atlantic Ocean, which modulate convection and rainfall near the Gulf of Guinea by means of SST thermal forcing and SST-related meridional gradient; and (ii) the interaction among the AEJ, TEJ, low-level westerly flow, moist convection, and AEWs during July-September, which modulates rainfall variability in the interior of West Africa, primarily within the ITCZ rain band. Evident seasonality in synoptic-scale wave signals is shown to be a good indication of this seasonal evolution. © 2004 American Meteorological Society."
"6602574969;6701812159;36948127000;7004617145;56246028600;","Large-scale diversity patterns of vascular epiphytes in Neotropical montane rain forests",2004,"10.1111/j.1365-2699.2004.01093.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4444305744&doi=10.1111%2fj.1365-2699.2004.01093.x&partnerID=40&md5=1e0ef757836c7a3b612c69ae387b170f","Aim: Epiphytes contribute up to 30% to the number of vascular plant species in certain global biodiversity hotspots, e.g. the Ecuadorian Andes. However, their large scale diversity patterns are still discussed on the base of results from a few, local epiphyte inventories. Consequently, explanatory models on epiphyte diversity concentrate on the impact of local climate on small scale epiphyte species richness. Our aim was to analyse large scale elevational patterns of epiphyte diversity integrating data from different geographic scales. Location: Tropical America, with special emphasis on the Ecuadorian Andes. Methods: Our study is based on two data sources. First, we analysed the elevational patterns of epiphyte diversity based on the Catalogue of the Vascular Plants of Ecuador and the Libro Rojo de las Plantas Endèmicas del Ecuador. Secondly, the floristic turnover between the epiphyte inventories of seven montane and four lowland study sites in the Neotropics was analysed. Results: The floristic turnover between Neotropical montane epiphyte floras is higher than the one between lowland epiphyte floras. Montane study sites located only a few kilometres apart from each other show considerable differences in their epiphyte species inventories. Irrespectively of their similar dispersal mode, the floristic turnover is much higher for orchids than for Pteridophyta. The Orchidaceae are the species richest group in all of the examined 11 Neotropical epiphyte floras. At the larger scale of the Ecuadorian Flora, c. 50% of the species in the elevational zone with maximum epiphyte diversity (between 1000 and 1500 m) are orchids. Elevational patterns of epiphyte diversity strongly reflect patterns of Orchidaceae. Main conclusions: Our results support the observation of a 'mid-elevation bulge' of epiphyte diversity by Gentry and Dodson. It has been frequently shown that the high humidity in mid-elevations is suitable to maintan a high epiphyte species richness. Our findings show that in addition, large scale epiphyte diversity in montane rain forest is increased by the high floristic turnover at local and regional scale. Based on the importance of Orchidaceae for epiphyte diversity, we discuss that speciation processes corresponding to the highly diverse environment are a driving force for endemism, floristic heterogeneity and consequently for large scale epiphyte species richness in montane forests."
"7501720647;6701670597;","Wind shear effects on cloud-radiation feedback in the western Pacific warm pool",2004,"10.1029/2004GL020199","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7044222524&doi=10.1029%2f2004GL020199&partnerID=40&md5=242a4fa3746f0c2b4039652be96e4a27","Upper tropospheric stratiform clouds associated with deep convection are impprtant to global radiation budgets and to cloud-radiation feedbacks on climate variability and change. Several recent observational studies indicate that vertical wind shear is an important factor affecting stratiform cloud fraction and cloud overlap. This study further examines wind shear effects on cloud properties (including cloud fraction and cloud optical depth) and associated top of atmosphere (TOA) and surface radiative fluxes, using observations from the Tropical Ocean Global Atmosphere program's Coupled Ocean Atmosphere Response Experiment (TOGA COARE) experiment and long-term satellite measurements. Wind shear affects cloud-radiative fluxes, through both the cloud fraction and optical thickness, in a strong and systematic way. In typical convecting conditions, shear-induced additional cloudiness can reduce outgoing longwave radiation (OLR) by 10s of Wm-2, implying longwave radiative changes on the order of 10% of the total latent heating. Such cloud also reflects shortwave radiation, reducing surface downward flux (energy input to the ocean) by 10s of Wm-2. Current climate models lack these effects. Copyright 2004 by the American Geophysical Union."
"6701832491;6701915334;8683032900;","Regional climate effects of Arctic Haze",2004,"10.1029/2004GL020318","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7044263253&doi=10.1029%2f2004GL020318&partnerID=40&md5=49e83e7d0191e78b14369118eb1343d7","The direct climate effect of aerosols has been studied within a regional atmospheric model of the Arctic. The mean springtime effect on the near surface temperature has been estimated and showed to be within ±1 K. However, the aerosol effect varies strongly regionally depending on the surface albedo, atmospheric humidity, and cloud condition of the region. The interannual variability of the aerosol effect is very pronounced (for the near surface temperature in the order of 2 K) and is connected with the strong varying year-specific atmospheric conditions. Due to the high horizontal resolution of the model, it was possible to assess the influence both on the large-scale as well as on the meso-scale atmospheric circulation. Through the aerosol-radiation-circulation feedback, the scattering and absorption of radiation by aerosol cause pressure pattern changes which have the potential to modify Arctic teleconnection patterns like the Barents Sea Oscillation. Copyright 2004 by the American Geophysical Union."
"57203053317;26643250500;7102988363;","Sensitivity studies of cirrus clouds formed by heterogeneous freezing in the ECHAM GCM",2004,"10.1029/2003JD004443","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7044272796&doi=10.1029%2f2003JD004443&partnerID=40&md5=2a0491ac5893ef76a97cd8a28c0f0355","Cirrus clouds can form by homogeneous and heterogeneous ice nucleation mechanisms at temperatures below 235 K. Here we evaluate the effectiveness of heterogeneous freezing versus homogeneous freezing using a newly developed parameterization of heterogeneous freezing that is restricted to immersion freezing as the most likely pathway for heterogeneous ice formation in cirrus conditions [Kärcher and Lohmann, 2003]. In addition to a reference simulation considering homogeneous nucleation with temperature-dependent freezing thresholds, we discuss two idealized model experiments. We conduct a scenario that hypothetically assumes that the aerosol particles available for homogeneous freezing could act as freezing nuclei commencing freezing at 130% with respect to ice and contrast that by a scenario that only considers black carbon and mineral dust as immersion nuclei with the same freezing relative humidity of 130%. These idealized simulations serve to delimit possible climate responses. If the number of freezing nuclei is limited by the number of black carbon and dust aerosols, then heterogeneous freezing results in fewer ice crystals than formed by homogeneous freezing. These fewer ice crystals grow more readily to precipitation size and with that increase the global mean precipitation, decrease the ice water path, and trap less outgoing longwave radiation at the top of the atmosphere. Copyright 2004 by the American Geophysical Union."
"6603416853;7005313336;6508389989;6601974795;55893487700;","A 14-year European Cloud Climatology from NOAA/AVHRR data in comparison to surface observations",2004,"10.1029/2004GL020098","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7044222604&doi=10.1029%2f2004GL020098&partnerID=40&md5=9246a27831d8c79363c6b2cf57a79ff5","A 14-year (1990-2003) high resolution European Cloud Climatology has been generated by use of NOAA/AVHRR data. For selected areas we present spatially averaged monthly means of total cloud cover derived from noon overpasses and compare them with surface SYNOP observations. The climatologies do not reveal a significant trend of cloud cover over the 14-year period. However, both data sets show a clear latitudinal variability and a seasonal dependence which is more pronounced in the satellite than in the SYNOP observations. Mean differences between satellite and SYNOP data range from about -2% to -10% in all seasons except summer when the mean difference is as large as -15.3%. As a special feature we notice the broad minimum of cloud cover during the extreme dry and hot summer in 2003 in Central Europe. Copyright 2004 by the American Geophysical Union."
"7410041005;35419152500;6701648855;7004210193;","A new way to measure cirrus cloud ice water content by using ice Raman scatter with Raman lidar",2004,"10.1029/2004GL020004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7044269693&doi=10.1029%2f2004GL020004&partnerID=40&md5=856d5787de05c0f18579af000948b5c1","To improve our understanding of cirrus cloud radiative impact on the current and future climate, improved knowledge of cirrus cloud microphysical properties is needed. However, long-term studies of the problem indicate that accurate cirrus cloud measurements are challenging. This is true for both, remote sensing as well as in situ sampling. This study presents a new method to remotely sense cirrus microphysical properties utilizing the Raman scattered intensities from ice crystals using a Raman lidar. Since the intensity of Raman scattering is fundamentally proportional to the number of molecules involved, this method provides a more direct way of measuring the ice water content compared with other schemes. Case studies presented here show that this method has the potential to provide simultaneous measurements of many of the essential information of cirrus microphysical properties. Copyright 2004 by the American Geophysical Union."
"7005065590;7403076014;7005852356;","A multivariate empirical-orthogonal-function-based measure of climate model performance",2004,"10.1029/2004JD004584","https://www.scopus.com/inward/record.uri?eid=2-s2.0-6444239256&doi=10.1029%2f2004JD004584&partnerID=40&md5=160ee8d14eb09f87a5876d06217505ff","A measure of the average distance between climate model predictions of multiple fields and observations has been developed that is based on the use of empirical orthogonal functions (EOFs). The application of EOFs provides a means to use information about spatial correlations in natural variability to provide a more balanced view of the significance of changes in model predictions across multiple fields, seasons, and regions. A comparison is made between the EOF-based measure and measures that are normalized by grid point variance and spatial variance for changes in the National Center for Atmospheric Research Community Climate Model, Version 3.10 (CCM3.10), parameter controlling initial cloud downdraft mass flux (ALFA), an important parameter within the Zhang and McFarlane [1995] convection scheme. All measures present consistent views that increasing ALFA from its default value creates significant improvements in precipitation, shortwave radiation reaching the surface, and surface latent heat fluxes at the expense of degrading predictions of total cloud cover, near-surface air temperature, net shortwave radiation at the top of the atmosphere, and relative humidity. However, the relative importance of each of these changes, and therefore the average view of the change in model performance, is significantly impacted by the details of how each measure of model performance handles regions with little or no internal variability. In general, the EOF-based measure emphasizes regions where modeled-observational differences are large, excluding those regions where internal variability is small. Copyright 2004 by the American Geophysical Union."
"6701636816;7005275092;55673012400;7003414293;7003927831;7401850582;7404611595;26028515700;26643054400;57136469800;57218357458;","Chemical transport model ozone simulations for spring 2001 over the western Pacific: Regional ozone production and its global impacts",2004,"10.1029/2003JD004041","https://www.scopus.com/inward/record.uri?eid=2-s2.0-6444222026&doi=10.1029%2f2003JD004041&partnerID=40&md5=3af213174611076da79accfe83def400","The spatial and temporal variation in ozone production over major source regions in East Asia during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) measurement campaign in spring 2001 is assessed using a global chemical transport model. There is a strong latitudinal gradient in ozone production in springtime, driven by regional photochemistry, which rapidly diminishes as the season progresses. The great variability in meteorological conditions characteristic of East Asia in springtime leads to large daily variability in regional ozone formation, but we find that it has relatively little impact on the total global production. We note that transport processes effectively modulate and thus stabilize total ozone production through their influence over its location. However, the impact on the global ozone burden, important for assessing the effects of precursor emissions on tropospheric oxidizing capacity and climate, is sensitive to local meteorology through the effects of location on chemical lifetime. Stagnant, anticyclonic conditions conducive to substantial boundary layer ozone production typically allow little lifting of precursors into the free troposphere where greater ozone production could occur, and the consequent shorter chemical lifetime for ozone leads to relatively small impacts on global ozone. Conversely, cyclonic conditions with heavy cloud cover suppressing regional ozone production are often associated with substantial cloud convection, enhancing subsequent production in the free troposphere where chemical lifetimes are longer, and the impacts on global ozone are correspondingly greater. We find that ozone formation in the boundary layer and free troposphere outside the region of precursor emissions dominates total gross production from these sources in springtime, and that it makes a big contribution to the long range transport of ozone, which is greatest in this season. Copyright 2004 by the American Geophysical Union."
"55977336000;16637291100;7201607592;7101677832;7102063963;","Nighttime polar cloud detection with MODIS",2004,"10.1016/j.rse.2004.06.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4143144279&doi=10.1016%2fj.rse.2004.06.004&partnerID=40&md5=bba7a5d8cacb2cbbec9d16195fe432d4","Cloud detection is the first step in studying the role of polar clouds in the global climate system with satellite data. In this paper, the cloud detection algorithm for the Moderate Resolution Imaging Spectrometer (MODIS) is evaluated with model simulations and satellite data collocated with radar/lidar observations at three Arctic and Antarctic stations. Results show that the current MODIS cloud mask algorithm performs well in polar regions during the day but does not detect more than 40% of the cloud cover over the validation sights at night. Two new cloud tests utilizing the 7.2 μm water vapor and 14.2 μm carbon dioxide bands, one new clear-sky test using the 7.2 μm band, and changes to the thresholds of several other tests are described. With the new cloud detection procedure, the misidentification of cloud as clear decreases from 44.2% to 16.3% at the two Arctic stations, and from 19.8% to 2.7% at the Antarctic station. © 2004 Elsevier Inc. All rights reserved."
"7003843648;7401658754;7005387356;","Pacific interdecadal climate variability: Linkages between the tropics and the North Pacific during boreal winter since 1900",2004,"10.1175/1520-0442(2004)017<3109:PICVLB>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4444259428&doi=10.1175%2f1520-0442%282004%29017%3c3109%3aPICVLB%3e2.0.CO%3b2&partnerID=40&md5=cb961b4493dc8d80f44731b5a694382e","This study examines the tropical linkages to interdecadal climate fluctuations over the North Pacific during boreal winter through a comprehensive and physically based analysis of a wide variety of observational datasets spanning the twentieth century. Simple difference maps between epochs of high sea level pressure over the North Pacific (1900-24 and 1947-76) and epochs of low pressure (1925-46 and 1977-97) are presented for numerous climate variables throughout the tropical Indo-Pacific region, including rainfall, cloudiness, sea surface temperature (SST), and sea level pressure. The results support the notion that the Tropics play a key role in North Pacific interdecadal climate variability. In particular, SST anomalies in the tropical Indian Ocean and southeast Pacific Ocean, rainfall and cloudiness anomalies in the vicinity of the South Pacific convergence zone, stratus clouds in the eastern tropical Pacific, and sea level pressure differences between the tropical southeast Pacific and Indian Oceans all exhibit prominent interdecadal fluctuations that are coherent with those in sea level pressure over the North Pacific. The spatial patterns of the interdecadal tropical climate anomalies are compared with those associated with ENSO, a predominantly interannual phenomenon; in general, the two are similar with some differences in relative spatial emphasis. Finally, a published 194-yr coral record in the western tropical Indian Ocean is shown to compare favorably with the twentieth-century instrumental records, indicating the potential for extending knowledge of tropical interdecadal climate variability to earlier time periods. © 2004 American Meteorological Society."
"6603561402;7005453346;","The variability of modeled tropical precipitation",2004,"10.1175/1520-0469(2004)061<1993:TVOMTP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4444237186&doi=10.1175%2f1520-0469%282004%29061%3c1993%3aTVOMTP%3e2.0.CO%3b2&partnerID=40&md5=b352f69064211e3748b856aaa9e79fd3","This paper investigates the temporal properties of tropical precipitation in the Canadian Centre for Climate Modelling and Analysis (CCCma) third-generation atmospheric general circulation model (AGCM3). AGCM3 employs the penetrative mass-flux (PMF) scheme of Zhang and McFarlane (ZM) for the parameterization of deep cumulus convection. It is found that the temporal variability of the ZM scheme is sensitive to a number of its internal parameters as well to the use of a prognostic, rather than diagnostic, closure condition for the cloud-base mass flux. Sensitivity experiments suggest that the ZM scheme can produce realistic amounts of variability when compared to direct radar observations of deep cumulus convection in the Tropics. A central finding of this study is that the resolved large-scale stratiform precipitation (LSP) in the model can participate in the modeling of deep latent heating and so compete with the ZM scheme in the Tropics. In modeling deep latent heating the LSP is found to mimic the behavior of a moist-convective adjustment scheme. In AGCM3 it is found that typical parameter settings of the ZM scheme place it in a regime in which the temporal variability of tropical precipitation is dominated by this behavior of the LSP, while the temporal mean is dominated by the ZM scheme. In such circumstances it is the LSP, and not the ZM scheme, that provides the primary source of resolved tropical Kelvin and mixed Rossby-gravity waves in the GCM. Such competition between LSP and the parameterization of deep convection appears to be active in other modeling studies. Consequently, it has the potential to complicate efforts to understand the nature of resolved tropical waves in GCMs and their role in the forcing of the quasi-biennial and semiannual oscillations."
[No author id available],"Cirrus cloud flights test assumptions",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-69649108843&partnerID=40&md5=34534a90a01c10f5b536baeeb675036c","Scientists from the University of Utah conducted test flights to study the inside of cirrus clouds. A WB57 jet was flown into the clouds and the conditions observed were compared with information from NASA satellites Terra and Aqua to determine how much sunlight the clouds reflect, as well as how much insulation they provide. The team found that ice crystals inside the clouds are in general many times smaller than most climate models assume."
"7003976079;7201443624;","Evaluating climate model simulations of tropical cloud",2004,"10.1111/j.1600-0870.2004.00061.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3843146374&doi=10.1111%2fj.1600-0870.2004.00061.x&partnerID=40&md5=3a4ce3a18678c36b2de7f37a87301fb7","The representation of tropical cloud and its radiative effects in the Hadley Centre climate model are evaluated using a combination of Earth observation data and meteorological reanalyses. It is shown that useful information regarding the model's physical parametrizations can be obtained by considering cloud radiative effects and cloud types in terms of 'dynamical regimes', defined in terms of sea surface temperature and large-scale vertical motion. In addition to comparisons with observed top-of-atmosphere radiation budget parameters and total cloud amount, information is obtained through direct comparisons of International Satellite Cloud Climatology Project (ISCCP) cloud types, defined according to cloud top pressure and optical depth, with corresponding model diagnostics. An analysis of the atmosphere-only model, HadAM3, demonstrates how errors in the albedo and outgoing long-wave radiation can be related to the simulation of particular cloud types in the different dynamical regimes. Inconsistencies between the simulations of the various cloud types and the top-of-atmosphere radiation budget are also highlighted. A version of the model including several new cloud-related paramettizations is then examined. A more consistent comparison with the observed radiation budget and cloud amounts is obtained, although deficiencies in the simulation still remain. A parametrization for the radiative effects of convective anvils and the impact of a new boundary layer mixing scheme are examined in more detail. Finally, it is shown how the climate model's ability to simulate the observed interannual variability of cloud in the equatorial Pacific follows directly from the analysis according to dynamical regimes. © Blackwell Munksgaard, 2004."
[No author id available],"Earthshine, sunshine trends may shed light on climate",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-4444249913&partnerID=40&md5=6a91ce72da2cacef69ce7bc9b15198a4","In 1998, researchers from the New Jersey Institute of Technology (NJIT) and the California Institute of Technology (Caltech) started regular earthshine monitoring with the use of ordinary telescopes. The team compared their earthshine measurements from 1999 to mid-2001 with overlapping satellite observations from the International Satellite Cloud Climatology Project from 1983 to 2001. Evidence was obtained that the Earth's average albedo varies considerably from year to year and from decade to decade. A related study conducted by researchers from the Australian National University provided evidence of less sunlight reaching the Earth's surface. Both studies suggest that the Earth reflects more light toward space than it did a decade or more ago."
"7102514911;8542639900;7003770652;8603356700;56501802200;7004510293;","Formation of secondary organic aerosols from isoprene and its gas-phase oxidation products through reaction with hydrogen peroxide",2004,"10.1016/j.atmosenv.2004.06.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042608186&doi=10.1016%2fj.atmosenv.2004.06.001&partnerID=40&md5=1cbe4985c524e8c7d68312e166533a2a","Aerosols produced over forests impair visibility and may affect climate by scattering and absorbing solar radiation and by serving as cloud condensation nuclei. Here, we introduce, to our knowledge, a new route to secondary organic aerosol formation from isoprene and its gas-phase oxidation products, methacrolein and methacrylic acid, namely, multiphase acid-catalysed oxidation with hydrogen peroxide, a perfect analogue to atmospheric sulphate formation. We demonstrate that the formation of major secondary organic aerosol components that are present in natural forest aerosols collected at K-puszta, Hungary, during the summer of 2003, namely, 2-methyltetrols and 2,3-dihydroxymethacrylic acid, can be explained by this mechanism. © 2004 Elsevier Ltd. All rights reserved."
"8247122100;7004479957;","Quasi-Lagrangian large eddy simulations of cross-equatorial flow in the East Pacific atmospheric boundary layer",2004,"10.1175/1520-0469(2004)061<1837:QLESOC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4344568742&doi=10.1175%2f1520-0469%282004%29061%3c1837%3aQLESOC%3e2.0.CO%3b2&partnerID=40&md5=9c4085193e19af9c5aff8ceb95af2b8d","Using a large eddy simulation (LES), the atmospheric boundary layer (ABL) is numerically modeled along 95°W from 8°S to 4°N during boreal autumn, and compared to observations from the East Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System (EPIC) 2001. Since the local ABL winds are predominantly southerly in this season, a ""quasi-Lagrangian"" forcing is used in which the ABL air column is forced as if it were advecting northward with the mean September-October 2001 meridional wind across the equatorial cold tongue and the rapidly warming SSTs to the north. Pressure gradients and large-scale zonal advective tendencies are prescribed as a function of latitude. Where possible, observations from the EPIC 2001 experiment are used for forcing and for comparison with model results. The ABL's modeled vertical structure accords with the conceptual model of Wallace et al. and agrees well with observations. Surface stability accounts for the minimum in surface wind over the equatorial cold tongue and the maximum over the warm water to the north. Stability of the lower ABL over the cold tongue allows a jet to accelerate at about 500-m height, relatively uncoupled to the frictional surface layer. Vertical mixing over the warm water to the north distributes this momentum to the surface. Additional simulations were performed to explore the modeled ABL's sensitivity to pressure gradients, zonal advection, free-tropospheric humidity, and initial conditions. The model ABL was robust: changing the forcings resulted in little change in the modeled structure. The strongest sensitivity was of stratocumulus clouds over the cold tongue to cloud-top radiative cooling. Once formed at the southern edge of the cold tongue, modeled stratocumulus clouds demonstrate a remarkable ability to maintain themselves over the cold tongue in the absence of surface fluxes by radiative cooling at their tops. The persistence of thin stratocumulus clouds in this Lagrangian model suggests that horizontal advection of condensate might be an important process in determining cloudiness over the cold tongue. © 2004 American Meteorological Society."
"6603036372;7005921461;7005239449;","Impact of the North Atlantic oscillation on winter convection: Convective precipitation and cloud-to-ground lightning",2004,"10.1002/joc.1067","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3843052589&doi=10.1002%2fjoc.1067&partnerID=40&md5=c8dfd9ebf08768bdde6261d78be5fddc","The relationship between the North Atlantic oscillation (NAO) and winter (November to March) convection is analysed using two convective parameters: convective precipitation (CP) and cloud-to-ground (CG) lightning. Using winter CP values from 1950 to 2000 over the North Atlantic and western European area (30-70°N, 60°W-10°E), positive correlations were found between the NAO index values and CP at latitudes higher than ∼50°N, whereas negative correlations were found for latitudes lower than 50°N. The spatial pattern of correlation coefficients at latitudes higher (lower) than ∼50°N suggests that the advection of temperature (moisture) is the main factor contributing to the relationship between the NAO and CP. The NAO accounts for 47% (25%) of the first principal component of CP interannual variance at latitudes higher (lower) than 50°N. The monthly winter CG lightning-flash density for 9 years (1992-2000) over the Iberian Peninsula was analysed in relation to the NAO on a small spatial scale (0.4° longitude × 0.4° latitude). The results were consistent with those found for the CP over the same zone. The correlation coefficient between the monthly NAO index value and the monthly CG flash number is r = -0.6, suggesting a relationship between them. Spatial variations in this relationship were also studied. The results indicated that the impact of the NAO on CG lightning is stronger on the western Iberian Peninsula and decreases eastwards. © 2004 Royal Meteorological Society."
"7401829771;6603166240;7005035462;","Impact of TRMM SSTs on a climate-scale SST analysis",2004,"10.1175/1520-0442(2004)017<2938:IOTSOA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242730672&doi=10.1175%2f1520-0442%282004%29017%3c2938%3aIOTSOA%3e2.0.CO%3b2&partnerID=40&md5=6bcf48ea8380ab6b50c08c1c363a40f3","Prior efforts have produced a sea surface temperature (SST) optimum interpolation (OI) analysis that is widely used, especially for climate purposes. The analysis uses in situ (ship and buoy) and infrared (IR) satellite data from the Advanced Very High Resolution Radiometer (AVHRR). Beginning in December 1997, ""microwave"" SSTs became available from the Tropical Rainfall Measuring Mission (TRMM) satellite Microwave Imager (TMI). Microwave SSTs have a significant coverage advantage over ""IR"" SSTs because microwave SSTs can be retrieved in cloud-covered regions while IR SSTs cannot. However, microwave SSTs are at a much lower spatial resolution than the IR SSTs. In this study, the impact of SSTs derived from TMI was tested from the perspective of the OI analysis. Six different versions of the OI were produced weekly from 10 December 1997 to 1 January 2003 using different combinations of AVHRR and TMI data and including versions with and without a bias correction of the satellite data. To make the results more objective, 20% of the buoys were randomly selected and the SSTs from these buoys were withheld from the OI for independent verification. The results of the intercomparisons show that both AVHRR and TMI data have biases that must be corrected for climate studies. These biases change with time as physical properties of the atmosphere change and as satellite instruments and the orbits of the satellites, themselves, change. It is critical to monitor differences between satellite and other products to quickly diagnose any of these changes. For the OI analyses with bias correction, it is difficult using the withheld buoys to clearly demonstrate that there is a significant advantage in adding TMI data. The advantage of TMI data is clearly shown in the OI analyses without bias correction. Because IR and microwave satellite algorithms are affected by different sources of error, biases may tend to cancel when both TMI and AVHRR data are used in the OI. Bias corrections cannot be made in regions where there are no in situ data. In these regions, the results of the analyses without bias corrections apply. Because there are areas of the ocean with limited in situ data and restricted AVHRR coverage due to cloud cover, the use of both TMI and AVHRR should improve the accuracy of the analysis in these regions. In addition, the use of more than one satellite product is helpful in diagnosing problems in these products. © 2004 American Meteorological Society."
"6603764342;6602377428;6603472580;7103033688;","Climate impact of the European winter blocking episodes from the NCEP/NCAR reanalyses",2004,"10.1007/s00382-004-0410-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4544334414&doi=10.1007%2fs00382-004-0410-4&partnerID=40&md5=aae850fee819497ce1395f08b3765873","A comprehensive multivariable characterisation of the climatic impacts of winter blocking and strong zonal-flow (non-blocking) episodes over the Euro-Atlantic sector is presented here, using a 40-year (1958-97) consistent dataset from NCEP/NCAR. Anomaly fields of surface or low troposphere climate variables are then interpreted based on large-scale physical mechanisms, namely, the anomalous mean flow (characterised by the 500 hPa geopotential height and the surface wind) and the anomalous eddy activity (characterised by the surface vorticity and cyclonic activity). It is shown that the lower troposphere (850 hPa) temperature patterns are mainly controlled by the advection of heat by the anomalous mean flow. However, at the surface level, the anomaly patterns obtained for maximum and minimum temperatures present important asymmetries, associated with a different control mechanism, namely the modulation of shortwave and longwave radiation by cloud cover variations. It is shown that blocking and non-blocking episodes are typically associated with important meridional shifts in the location of maximum activity of transient eddies. The influence of persistent anomaly events in precipitable water is strongly related to the corresponding anomaly fields of lower troposphere temperature. The precipitation rate, however, appears to be essentially controlled by the surface vorticity field and preferred locations of associated cyclones. © Springer-Verlag 2004."
"6603896143;6508070993;7102084129;","Radar analysis of cloud systems and their rainfall yield in Israel",2004,"10.1560/G68K-30MN-D5V0-KUHU","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242656637&doi=10.1560%2fG68K-30MN-D5V0-KUHU&partnerID=40&md5=bbe16ae9d417bf6b12db498bfaef16af","This study documents the climatological occurrence of rainfall from different types of rain cloud systems over Israel and the adjacent seas. The rain cloud types are: (a) cold front; (b) cloud systems that develop in the cold sectors of cyclones; and (c) cloudiness of the cyclone center (vortex). The cloud systems within the cold sector include: (a) convection lines; (b) open Benard cells and unorganized cells; (c) the coastal front; and (d) cloud streets. While the warm front rain yield is negligible, the Red Sea trough adds about 5% to the total precipitation in the Mediterranean climate region of the country. The main rainfall yield contribution in the north of the country comes from cold fronts and vortices, while the southern part is dominated by less dynamically and more air-mass-convection-controlled rain cloud systems, such as Benard cells and coastal fronts. Analysis of the cloud pattern on a monthly basis reveals that the cold front is more active during November-December, with the climax of the coastal front in December, and the main vortex activity starts in January. We checked rainy/dry year variations and found that during rainy years, the vortex rain contribution is larger than that of the cold front. The coastal front also contributes more rain during wet years and tends to follow a more southerly route. In dry years, the proportion of vortex/cold front is reversed, and the coastal front rain yield is meager and has a more northerly route. © 2004 Science From Israel/LPPLtd."
"7401936984;55745955800;7401974644;6701464294;7102268722;8859530100;","Impact of a revised convective triggering mechanism on community atmosphere model, version 2, simulations: Results from short-range weather forecasts",2004,"10.1029/2004JD004692","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5444272242&doi=10.1029%2f2004JD004692&partnerID=40&md5=addef7b3bf156c51deec9c526c6f9984","This study implements a revised convective triggering condition in the National Center for Atmospheric Research (NCAR) Community Atmosphere Model, Version 2 (CAM2), model to reduce its excessive warm season daytime precipitation over land. The new triggering mechanism introduces a simple dynamic constraint on the initiation of convection that emulates the collective effects of lower level moistening and upward motion of the large-scale circulation. It requires a positive contribution from the large-scale advection of temperature and moisture to the existing positive convective available potential energy (CAPE) for model convection to start. In contrast, the original convection triggering function in CAM2 assumes that convection is triggered whenever there is positive CAPE, which results in too frequent warm season convection over land arising from strong diurnal variation of solar radiation. We examine the impact of the new trigger on CAM2 simulations by running the climate model in numerical weather prediction (NWP) mode so that more available observations and high-frequency NWP analysis data can be used to evaluate model performance. We show that the modified triggering mechanism has led to considerable improvements in the simulation of precipitation, temperature, moisture, clouds, radiations, surface temperature, and surface sensible and latent heat fluxes when compared to the data collected from the Atmospheric Radiation Measurement (ARM) Program at its Southern Great Plains (SGP) site. Similar improvements are also seen over other parts of the globe. In particular, the surface precipitation simulation has been significantly improved over both the continental United States and around the globe; the overestimation of high clouds in the equatorial tropics has been substantially reduced; and the temperature, moisture, and zonal wind are more realistically simulated. Results from this study also show that some systematic errors in the CAM2 climate simulations can be detected in the early stage of model integration. Examples are the extremely overestimated high clouds in the tropics in the vicinity of Intertropical Convergence Zone and the spurious precipitation maximum to the east of the Rockies. This has important implications in studies of these model errors since running the climate model in NWT mode allows us to perform a more in-depth analysis during a short time period where more observations are available and different model errors from various processes have not compensated for the systematic errors. Copyright 2004 by the American Geophysical Union."
"6602550399;55951225700;6701508272;","Diurnal temperature range as an index of global climate change during the twentieth century",2004,"10.1029/2004GL019998","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4544240917&doi=10.1029%2f2004GL019998&partnerID=40&md5=0eb91e0aa43bc0509a48edf3b0d3a962","The usefulness of global-average diurnal temperature range (DTR) as an index of climate change and variability is evaluated using observations and climate model simulations representing unforced climate variability and anthropogenic climate change. On decadal timescales, modelled and observed intrinsic variability of DTR compare well and are independent of variations in global mean temperature. Observed reductions in DTR over the last century are large and unlikely to be due to natural variability alone. Comparison of observed and anthropogenic-forced model changes in DTR over the last 50 years show much less reduction in DTR in the model simulations due to greater warming of maximum temperatures in the models than observed. This difference is likely attributed to increases in cloud cover that are observed over the same period and are absent in model simulations. Copyright 2004 by the American Geophysical Union."
"55957189000;57205638870;","Significant dust simulation differences in nudged and climatological operation mode of the AGCM ECHAM",2004,"10.1029/2003JD004381","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4844226688&doi=10.1029%2f2003JD004381&partnerID=40&md5=7109d57d66a11887b7f5f1d2ad081119","The geographical distribution and the seasonal variability of soil dust aerosol have been investigated with the climate model ECHAM4. Two experiments have been performed: a climatological with prescribed climatological sea surface temperatures (CLIM) and a nudged where the model is forced by ECMWF Reanalysis data of the particular years 1986-1991 (NUDGE). The mean geographical distribution and the seasonal variability of mineral dust alter between the different modes of operation of the climate model. Largest deviations occur in Northern Hemisphere winter and are related to the overestimation and the mislocation of the Azores high in ECHAM4. The Saharan dust plume is shifted farther north in CLIM compared to NUDGE and Meteosat satellite observations with significant implication for the cross-Atlantic transport. In the dust source regions the wind speed distribution is slightly shifted and creates a twofold difference in total dust emissions. Our results indicate that the mode of operation of the climate model seems to be as important as the interannual variability of the dust cloud by climate variations alone. Copyright 2004 by the American Geophysical Union."
"7401436524;56962915800;7402989545;","Climate effects of the deep continental stratus clouds generated by the Tibetan Plateau",2004,"10.1175/1520-0442(2004)017<2702:CEOTDC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3843097335&doi=10.1175%2f1520-0442%282004%29017%3c2702%3aCEOTDC%3e2.0.CO%3b2&partnerID=40&md5=44f53ee75a117fecb446903eb7935ae1","Evidence is presented to show that the maximum annual mean cloud optical depth between 60°S and 60°N is located on the lee side of the Tibetan Plateau. This largest cloud optical depth is produced by persistent deep stratus clouds (primarily the nimbostratus and altostratus) during winter and spring. These deep stratus clouds are generated and maintained by the frictional and blocking effects of the Tibetan Plateau. The plateau slows down the overflow, inducing downstream midlevel divergence; meanwhile it forces the low-level flows to converge downstream, generating sustained large-scale lifting and stable stratification that maintain the thick stratus clouds. These stratus clouds produce extremely strong cloud radiative forcing at the top of the atmosphere, which fundamentally influences the local energy balance and climate change. Analysis of the long-term meteorological station observations reveals that the monthly mean anomalous cloudiness and surface temperature vary in tandem. In addition, the surface warming leads to destabilization and desaturation in the boundary layer. This evidence suggests a positive feedback between the continental stratus clouds and surface temperature through changing lower-tropospheric relative humidity and stratification. It is shown that the positive feedback mechanism is more robust during the period of the surface cooling than during the surface warming. It is suggested that the positive climate feedback of the continental stratus cloud may be instrumental in understanding the long-term climatic trend and variations over East Asia. © 2004 American Meteorological Society."
"55749288300;7006133602;7006063017;","Future climate change of the subtropical North Atlantic: Implications for the cloud forests of Tenerife",2004,"10.1023/B:CLIM.0000037488.33377.bf","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4344670342&doi=10.1023%2fB%3aCLIM.0000037488.33377.bf&partnerID=40&md5=7197cf2dee12b04e009b1d51287dc45a","This paper is concerned with climate change in the region of the Canary Islands and the potential implications for the laurel forests of Tenerife. Frequent orographic cloud formation during the dry season is of vital importance to the altitudinal distribution of the laurel forests, because it maintains a semi-humid environment in the otherwise semi-arid climate of the Canary Islands. The distinctive environmental conditions in conjunction with the location of the Canary Islands on the Northern poleward edge of the Hadley Circulation make these ecosystems potentially highly sensitive to regional changes in climatic conditions. To explore this sensitivity, we first quantify observed trends in humidity and temperature across an altitudinal transect at the base of the Anaga peninsular, and second, analyse the results of three GCM experiments (CGCM1, ECHAM4 and CSIRO) to develop alternative climate change scenarios, and third, use these data to assess likely shifts in the elevational distribution of the laurel forest climate envelope. We report a significant increase in relative humidity and decreases in the diurnal temperature range on Tenerife at altitudes below the trade wind inversion within the last 30 years during the dry season, which suggests an increased occurrence of low-level clouds. There is also partial evidence for a drying trend across the trade wind inversion, which may be linked to an increased subsidence. Overall, the models suggest a downward shift of the area climatically suitable for laurel forests, which may be driven by changes in temperature and moisture supply in the region as well as by larger-scale changes in the atmospheric circulation. Our findings contrast with previously published findings for a tropical montane cloud region, which predict an upward shift of the cloud base. This suggests, following the assumptions inherent in the models applied, that the ecological consequences of climate change for cloud forests may be linked to their relative location in the Hadley Circulation."
"25941200000;6701511324;","Neglect by GCMs of subgrid-scale horizontal variations in cloud-droplet effective radius: A diagnostic radiative analysis",2004,"10.1256/qj.03.116","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242816010&doi=10.1256%2fqj.03.116&partnerID=40&md5=950670776f1345422dd9cd2b80ead4b9","Output from a global climate model (GCM) that employed a low-resolution two-dimensional cloud-system-resolving model (CSRM) in each column is used to assess the radiative impact of neglecting subgrid-scale horizontal variations in cloud-droplet effective radius re. For this diagnostic study, only liquid-phase variations in re are addressed; the ice-cloud particle distributions are assumed to be constant. For reference calculations, values of re in the CSRM cells are computed assuming that the droplet-number concentration Ncld and the effective variance of droplet-size distribution are constant in a GCM cell. The independent-column approximation is used to produce flux profiles for each GCM column. Three alternative methods of setting horizontally-invariant re are examined, each of which resemble how re is set in one-dimensional radiative-transfer models. Relative to the reference calculations, the other methods lead to positive spurious radiative forcings at the surface and at the top of the atmosphere. These stem from overestimation of optical-depth variability and, thus, reduced short-wave albedo of clouds. Globally averaged, these forcings range from 1 W m-2 to 3 W m-2, with zonal-mean biases reaching almost 15 W m-2. The most severe biases arise from use of constant values of re over the land and the ocean. In addition, radiative effects due to unacknowledged uncertainty in Ncld (or re) are assessed. It is shown that ad hoc, but not outlandish, estimates of unbiased uncertainty in Ncld impart biases on estimates of the earth's solar-radiation budget (tantamount to a spurious radiative forcing). These arise through the chain of nonlinear relations that link Ncld to solar radiative transfer. © Crown copyright, 2004."
"7003931528;7003979342;57203053317;6602729528;","Interactions between climatic factors",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-4143123285&partnerID=40&md5=d45748430ea7a6f16f0d1daceb702cbc","Experiments with the ECHAM4 atmospheric general circulation model coupled to a slab ocean and thermodynamic sea-ice model were performed. It was found that the climate response to the combined greenhouse gas and aerosol forcing is not just a sum of the response to the individual forcings. The global hydrological sensitivity was observed to be almost three times higher for aerosol forcing than for greenhouse gas forcing. Combining both forcings led to the decrease of evaporation and precipitation despite global warming."
"7101825560;","The cumulus parameterization problem: Past, present, and future",2004,"10.1175/1520-0442(2004)017<2493:RATCPP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3843138534&doi=10.1175%2f1520-0442%282004%29017%3c2493%3aRATCPP%3e2.0.CO%3b2&partnerID=40&md5=d58ee80a9a41ee6439e158b4aa94b4ea","A review of the cumulus parameterization problem is presented with an emphasis on its conceptual aspects covering the history of the underlying ideas, major problems existing at present, and possible directions and approaches for future climate models. Since its introduction in the early 1960s, there have been decades of controversies in posing the cumulus parameterization problem. In this paper, it is suggested that confusion between budget and advection considerations is primarily responsible for the controversies. It is also pointed out that the performance of parameterization schemes can be better understood if one is not bound by their authors' justifications. The current trend in posing cumulus parameterization is away from deterministic diagnostic closures, including instantaneous adjustments, toward prognostic or nondeterministic closures, including relaxed and/or triggered adjustments. A number of questions need to be answered, however, for the merit of this trend to be fully utilized. Major practical and conceptual problems in the conventional approach of cumulus parameterization, which include artificial separations of processes and scales, are then discussed. It is rather obvious that for future climate models the scope of the problem must be drastically expanded from ""cumulus parameterization"" to ""unified cloud parameterization,"" or even to ""unified model physics."" This is an extremely challenging task, both intellectually and computationally, and the use of multiple approaches is crucial even for a moderate success. ""Cloud-resolving convective parameterization"" or ""superparameterization"" is a promising new approach that can develop into a multiscale modeling framework (MMF). It is emphasized that the use of such a framework can unify our currently diversified modeling efforts and make verification of climate models against observations much more constructive than it is now. Copyright © 2004 American Meteorological Society."
"6701511324;25941200000;","Evaluation and optimization of sampling errors for the Monte Carlo Independent Column Approximation",2004,"10.1256/qj.03215","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4844228930&doi=10.1256%2fqj.03215&partnerID=40&md5=ae8748df79ffe90579cbbcb73389c138","The Monte Carlo Independent Column Approximation (McICA) method for computing domain-average broadband radiative fluxes is unbiased with respect to the full ICA, but its flux estimates contain conditional random noise. McICA's sampling errors are evaluated here using a global climate model (GCM) dataset and a correlated-k distribution (CKD) radiation scheme. Two approaches to reduce McICA's sampling variance are discussed. The first is to simply restrict all of McICA's samples to cloudy regions. This avoids wasting precious few samples on essentially homogeneous clear skies. Clear-sky fluxes need to be computed separately for this approach, but this is usually done in GCMs for diagnostic purposes anyway. Second, accuracy can be improved by repeated sampling, and averaging those CKD terms with large cloud radiative effects. Although this naturally increases computational costs over the standard CKD model, random errors for fluxes and heating rates are reduced by typically 50% to 60%, for the present radiation code, when the total number of samples is increased by 50%. When both variance reduction techniques are applied simultaneously, globally averaged flux and heating rate random errors are reduced by a factor of ∼3. © Royal Meteorological Society, 2004."
"7004091067;7006029393;7202625046;","Satellite and CALJET aircraft observations of atmospheric rivers over the Eastern North Pacific Ocean during the winter of 1997/98",2004,"10.1175/1520-0493(2004)132<1721:SACAOO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943102656&doi=10.1175%2f1520-0493%282004%29132%3c1721%3aSACAOO%3e2.0.CO%3b2&partnerID=40&md5=1724d9a4cd0c2dbcc299998bd0c15c21","This study uses a unique combination of airborne and satellite observations to characterize narrow regions of strong horizontal water vapor flux associated with polar cold fronts that occurred over the eastern North Pacific Ocean during the winter of 1997/98. Observations of these ""atmospheric rivers"" are compared with past numerical modeling studies to confirm that such narrow features account for most of the instantaneous meridional water vapor transport at midlatitudes. Wind and water vapor profiles observed by dropsondes deployed on 25-26 January 1998 during the California Land-falling Jets Experiment (CALJET) were used to document the structure of a modest frontal system. The horizontal water vapor flux was focused at low altitudes in a narrow region ahead of the cold front where the combination of strong winds and large water vapor content were found as part of a low-level jet. A close correlation was found between these fluxes and the integrated water vapor (IWV) content. In case, 75% of the observed flux through a 1000-km cross-front baseline was within a 565-km-wide zone roughly 4 km deep. This zone contained 1.5 × 108 kg s-1 of meridional water vapor flux, the equivalent of ∼20% of the global average at 35°N. By compositing polar-orbiting satellite Special Sensor Microwave Imager (SSM/I) data from 46 dates containing long, narrow zones of large IWV, it was determined that the single detailed case was representative of the composite in terms of both the IWV amplitude (3.09 cm vs 2.81 cm) and the width of the area where IWV ≥ 2 cm (424 km vs 388 km). The SSM/I composites also showed that the width scales (defined by the 75% cumulative fraction along a 1500-km cross-plume baseline) for cloud liquid water and rain rate were 176 and 141 km, respectively, which are narrower than the 417 km for IWV. Examination of coincident Geostationary Operational Environmental Satellite (GOES) and SSM/I satellite data revealed that GOES cloud-top temperatures were coldest and cloud-top pressures were lowest in the core of the IWV plumes, and that the core cloud tops became substantially colder and deeper for larger IWV. A strong latitudinal dependence of the satellite-derived cross-river characteristics was also found. Atmospheric rivers form a critical link between weather and climate scales. They strongly influence both short-term weather and flood prediction, as well as seasonal climate anomalies and the global water cycle, through their cumulative effects. However, the rivers remain poorly observed by the existing global atmospheric observing system in terms of their horizontal water vapor fluxes."
"7102591209;6603735878;","The dependence of retrieved cirrus ice-crystal effective dimension on assumed ice-crystal geometry and size-distribution function at solar wavelengths",2004,"10.1256/qj.03.154","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4844229746&doi=10.1256%2fqj.03.154&partnerID=40&md5=4391665d3a04cdb71dc08b86ea0288f4","The dependence of retrieved ice-crystal effective dimension on assumed ice-crystal shape and size-distribution function is investigated at solar wavelengths (0.87, 1.6 and 3.7 μm). The dual viewing Along Track Scanning Radiometer is used to retrieve ice-crystal effective dimension using a method of Optimal Estimation over semi-transparent cirrus located in the tropics and mid-latitudes. The ice-crystal effective dimension is defined in terms of the effective diameter and it is retrieved assuming roughened hexagonal ice aggregates, pristine hexagonal ice columns, and four-branched bullet rosettes. It is shown that if a phase function that well represents the scattering properties of cirrus is applied to each crystal type then the retrieved ice-crystal effective diameter is only weakly dependent on ice-crystal shape and size-distribution function. Absolute differences between retrieved ice-crystal effective diameter assuming hexagonal ice columns and ice aggregates combined with a representative phase function are generally well within ±5 μm. The findings of this paper have the important implication that, in climate models, simulation of cirrus cloudy radiances at solar wavelengths might be made to be independent of assumed ice-crystal shape and size-distribution function. © Crown copyright, 2004."
"55717837500;57213597809;7403258822;8685265100;6506920369;6701497419;","A simple method for reconstructing a high-quality NDVI time-series data set based on the Savitzky-Golay filter",2004,"10.1016/j.rse.2004.03.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2942739366&doi=10.1016%2fj.rse.2004.03.014&partnerID=40&md5=6e551c3af9773f8ecdd7b985cb58762a","Although the Normalized Difference Vegetation Index (NDVI) time-series data, derived from NOAA/AVHRR, SPOT/VEGETATION, TERRA or AQUA/MODIS, has been successfully used in research regarding global environmental change, residual noise in the NDVI time-series data, even after applying strict pre-processing, impedes further analysis and risks generating erroneous results. Based on the assumptions that NDVI time-series follow annual cycles of growth and decline of vegetation, and that clouds or poor atmospheric conditions usually depress NDVI values, we have developed in the present study a simple but robust method based on the Savitzky-Golay filter to smooth out noise in NDVI time-series, specifically that caused primarily by cloud contamination and atmospheric variability. Our method was developed to make data approach the upper NDVI envelope and to reflect the changes in NDVI patterns via an iteration process. From the results obtained by applying the newly developed method to a 10-day MVC SPOT VGT-S product, we provide optimized parameters for the new method and compare this technique with the BISE algorithm and Fourier-based fitting method. Our results indicate that the new method is more effective in obtaining high-quality NDVI time-series. © 2004 Elsevier Inc. All rights reserved."
"7402969850;7103180783;7005070958;7102268722;","The 1997/98 El Niño: A test for climate models",2004,"10.1029/2004GL019956","https://www.scopus.com/inward/record.uri?eid=2-s2.0-6044250251&doi=10.1029%2f2004GL019956&partnerID=40&md5=9d8de4d38ca45032079e464bac0df480","Version 3 of the Hadley Centre Atmospheric Model (HadAM3) has been used to demonstrate one means of comparing a general circulation model with observations for a specific climate perturbation, namely the strong 1997/98 El Niño. This event was characterized by the collapse of the tropical Pacific's Walker circulation, caused by the lack of a zonal sea surface temperature gradient during the El Niño. Relative to normal years, cloud altitudes were lower in the western portion of the Pacific and higher in the eastern portion. HadAM3 likewise produced the observed collapse of the Walker circulation, and it did a reasonable job of reproducing the west/east cloud structure changes. This illustrates that the 1997/98 El Niño serves as a useful means of testing cloud-climate interactions in climate models. Copyright 2004 by the American Geophysical Union."
"7403180902;7005070958;","A procedure for evaluating feedback mechanisms in coupled atmosphere/ocean climate models",2004,"10.1029/2004GL019876","https://www.scopus.com/inward/record.uri?eid=2-s2.0-6044253668&doi=10.1029%2f2004GL019876&partnerID=40&md5=4006454bbde9063cbaa55811c66662f8","To understand inter-model differences in long-term simulations of climate change, as exist between coupled atmosphere/ocean general circulation models, it is necessary to first understand climate feedback mechanisms that operate within each of the various models. With this goal in mind, we have employed an 1870 to 1989 simulation, with prescribed increases in greenhouse gases, that was performed using the National Center for Atmospheric Research Community Climate System Model Version 1, as a vehicle for determining two feedback processes operating within that model. These are cloud feedback and snow/ice albedo feedback. A prerequisite to evaluating feedback mechanisms is to first evaluate the direct radiative forcing, caused by the increasing greenhouse gases, which produces global warming by the model, and a procedure for doing this is presented. Cloud feedback is then evaluated by referencing the model's change in global-mean cloud-radiative forcing to the direct greenhouse-gas induced radiative forcing, and a comparable procedure is employed to determine snow/ice albedo feedback. This model produces a moderately strong negative cloud feedback and a modest positive snow/ice albedo feedback. But the main purpose of this study is to provide a reasonably simple procedure for determining both cloud feedback and snow/ice albedo feedback within coupled atmosphere/ocean GCMs. Copyright 2004 by the American Geophysical Union."
"6701762451;7004715270;7401651197;6603385031;7202586843;7007061674;7406639632;7005968859;7404062492;","Observations of organic species and atmospheric ice formation",2004,"10.1029/2004GL019822","https://www.scopus.com/inward/record.uri?eid=2-s2.0-6044271588&doi=10.1029%2f2004GL019822&partnerID=40&md5=0ba0ea779f23b0340720082912b91906","Aerosol particles found in the lower confines of the atmosphere are typically internal mixtures of sulfate, inorganic salts, refractory components, and organic species. The effect these complex combinations have on cloud formation processes remains largely unknown. We have conducted two complementary studies on one important process, the homogeneous formation of ice by small particles. In the first study the freezing of atmospheric aerosol was induced using controlled temperature and humidity conditions. In the second study the chemical composition of the residue from ice crystals in high altitude clouds was analyzed. Here we show that organic components do not partition equally to the ice and aqueous phases. Instead, organic-rich particles preferentially remain unfrozen. These results suggest that emissions of organic species have the potential to influence aerosol-cold cloud interactions and climate. Copyright 2004 by the American Geophysical Union."
"56264677300;7007039218;7102496779;35461255500;","How important is nucleation in regional/global modelling?",2004,"10.1029/2004GL019525","https://www.scopus.com/inward/record.uri?eid=2-s2.0-6044250257&doi=10.1029%2f2004GL019525&partnerID=40&md5=9e79a60df9d41ce2c022f7e402718424","Modelling nucleation and subsequent growth is a difficult task especially in global and regional models. Therefore it is important to know under which conditions the freshly nucleated particles are able to survive the coagulation barrier and grow to the Aitken mode sizes and further to cloud condensation nuclei thus affecting climate. By using a sectional aerosol dynamics model AEROFOR at various conditions, the regions of parameter space in which nucleation plays an important role are identified and the contour plots are presented. Sulphuric acid is assumed to participate in both nucleation and condensation processes, additionally there is present some other condensable vapour. Our simulations show that nucleation is almost always an important process in the atmosphere excluding the cases when condensable vapour concentration is not high enough so that the nucleated particles have time to coagulate away before reaching the Aitken mode sizes. Thus it is well established to include nucleation in regional/global models. Copyright 2004 by the American Geophysical Union."
"7006847648;26643250500;","The impact of aerosols and gravity waves on cirrus clouds at midlatitudes",2004,"10.1029/2004JD004579","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4444379181&doi=10.1029%2f2004JD004579&partnerID=40&md5=22688c5bd00e8a222d63d6bc8d924a3a","We use a Lagrangian microphysical aerosol-cloud model to simulate cirrus clouds along trajectories at northern hemisphere midlatitudes. The model is constrained by recent in situ observations in terms of aerosol size distributions, freezing relative humidities, cooling rates, and cirrus particle sedimentation rates. Key features include competition between insoluble and volatile aerosol particles and temperature perturbations induced by high-frequency gravity waves. Recent analyses of field measurements have revealed the crucial roles both factors play in cirrus formation. We show that most cirrus form in synoptic cold pools, but with microphysical properties determined by mesoscale variability in vertical velocities. Heterogeneous ice nuclei (IN) present in concentrations probably typical for northern midlatitude background conditions (&lt;0.01-0.03 cm-3) significantly modify cirrus properties but do not control cirrus formation. The key effect of IN on cirrus clouds is a reduction of the number of ice crystals. This indirect aerosol effect results in reduced cloud albedo due to increased effective radii and decreased ice water contents, as well as in nonlinear changes of cirrus occurrence, optical extinction, and fraction of clouds that are subvisible. The nonlinear dependence of the three latter quantities appears when IN concentrations rise above a threshold concentration of some 0.01 cm-3, the exact value depending on the cloud formation temperature, cooling rate, and IN freezing relative humidity. In such conditions, IN become the controlling factor in cirrus formation, diminishing the role of homogeneous freezing. Ice nuclei with freezing thresholds near ice saturation are capable of introducing strong changes of cloud properties, even at low concentrations. Optically thin and subvisible cirrus are particularly susceptible to IN. The presence of a small number of IN (0.001 cm-3) can significantly increase their occurrence frequencies. If such clouds predominantly form on IN, they might be affected by anthropogenic activities. Changes in upper tropospheric cooling rates and ice-forming aerosols in a future climate may induce changes in cirrus occurrence that are comparable in magnitude to observed decadal trends in global cirrus cover. Copyright 2004 by the American Geophysical Union."
"7006303509;7005626683;7402934750;","Evidence of high ice supersaturation in cirrus clouds using ARM Raman lidar measurements",2004,"10.1029/2004GL019705","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4143154018&doi=10.1029%2f2004GL019705&partnerID=40&md5=04d1073891db09fd05ee52dd423070b6","Water vapor amounts in the upper troposphere are crucial to understanding the radiative feedback of cirrus clouds on the Earth's climate. We use a unique, year-long dataset of water vapor mixing ratio inferred from ground-based Raman lidar measurements to study the role of ice supersaturation in ice nucleation processes. We find that ice supersaturation occurs 31% of the time in over 300,000 data points. We also examine the distribution of ice supersaturation with height and find that in the uppermost portion of a cloud layer, the air is ice supersaturated 43% of the time. These measurements show that large ice supersaturation is common in cirrus clouds, which supports the theory of ice forming homogeneously. Given the continuous nature of these Raman lidar measurements, our results have important implications for studying ice nucleation processes using cloud microphysical models. Copyright 2004 by the American Geophysical Union."
"7003931528;7003979342;57203053317;6602729528;","Nonlinear aspects of the climate response to Greenhouse gas and aerosol forcing",2004,"10.1175/1520-0442(2004)017<2384:NAOTCR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2942599266&doi=10.1175%2f1520-0442%282004%29017%3c2384%3aNAOTCR%3e2.0.CO%3b2&partnerID=40&md5=8905fd73f9ff8d3a1f85e432e9e894d6","In a series of equilibrium experiments the climate response to present-day radiative forcings of anthropogenic greenhouse gases and aerosol particles is calculated. The study was performed with a model system consisting of the ECHAM4 atmospheric general circulation model coupled to a slab ocean and thermodynamic sea ice model. The model includes transport of the relevant chemical constituents, a sulfur chemistry model that calculates sulfate production in the gas and aqueous phase, and an aerosol model that accounts for source and sink processes. The aerosol cycle, the hydrological cycle, and the atmospheric dynamics are fully interactive. The climate response to aerosol forcing is not just a mirror image of the response to greenhouse forcing. This applies to the temperature changes, which are regionally more uniform for greenhouse forcing than for aerosol forcing as is already well known, and, in particular, to the hydrological cycle: the global hydrological sensitivity (Δprecip/Δtemp) to a I-K surface temperature change is almost 3 times higher for aerosol forcing than for greenhouse forcing. When both forcings are combined, a global warming is simulated while evaporation and precipitation decrease by about 2% K-1, resulting in a negative hydrological sensitivity. A strong dependency of the response to the type of forcing has also been found for the cloud water content and, consequently, for the change in cloud radiative forcing, which is substantially larger in the combined forcing experiment than in either of the individual forcing experiments. Consequently, the global warming for combined forcing is significantly smaller (0.57 K) than that obtained by adding the individual changes (0.85 K). Due to feedbacks between temperature changes and the hydrological cycle the simulated aerosol load, applying the same source strength, is considerably lower in a warmer climate (- 17% K-1 warming). A consequence of this aerosol-temperature feedback could be that a future increase in greenhouse gases may reduce the aerosol burden even if the source strength would not change. © 2004 American Meteorological Society."
"57204253860;7006432091;8861633300;","The tropical dynamical response to latent heating estimates derived from the TRMM precipitation radar",2004,"10.1175/1520-0469(2004)061<1341:TTDRTL>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242688106&doi=10.1175%2f1520-0469%282004%29061%3c1341%3aTTDRTL%3e2.0.CO%3b2&partnerID=40&md5=bc1ce2c7c5b0f0bef8cec7ee3e157656","A 3-yr (1998-2000) climatology of near-surface rainfall and stratiform rain fraction observed by the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) was used to calculate the four-dimensional distribution of tropical latent heating on seasonal-to-annual time scales. The TRMM-derived latent heating was then used to force an idealized primitive equation model using an initial value approach in order to obtain the quasi-steady-state, nonlinear, zonally asymmetric atmospheric response to precipitating tropical cloud systems. In agreement with previous studies, an increase in stratiform rain fraction elevates circulation centers and strengthens the upper-level response. Furthermore, horizontal variations in the vertical heating profile implied by the PR stratiform rain fraction pattern lead to circulation anomalies of varying height and vertical extent that are not present when the model is forced with a vertically uniform heating field. During El Niño, the trans-Pacific gradient in stratiform rain fraction that is normally present becomes more pronounced and the model response becomes even more sensitive to the horizontal variability of the latent heating vertical structure. When the heating field is modified to take into account the effects of nonprecipitating cumulus and cloud radiative forcing within the regions of tropical precipitating cloud systems, the overall pattern of the model response to the TRMM-derived latent heating is reinforced, as is the model's sensitivity to the variability in the latent heating vertical structure. © 2004 American Meteorological Society."
"7102718675;","Interannual, monthly, and regional variability in the Wet season diurnal cycle of precipitation in sub-Saharan Africa",2004,"10.1175/1520-0442(2004)017<2441:IMARVI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242687176&doi=10.1175%2f1520-0442%282004%29017%3c2441%3aIMARVI%3e2.0.CO%3b2&partnerID=40&md5=b31f38fcd5c667d3eb627462382f6acd","Convective systems in sub-Saharan Africa were defined from measurements by the Tropical Rainfall Measuring Mission satellite Microwave Imager at 85 GHz for four wet seasons, May-September 1998-2001. By applying a convective-stratiform discrimination algorithm to each convective system, the pixels within were designated as convective or stratiform cloud, life cycle ages assigned, and rainfall rates calculated. The years 1998 and 1999 were wetter than the long-term (1898-2000) mean, while 2000 and 2001 were drier. The wetter years had about 10% more convective systems than the drier years, but the size and intensity distributions for the wetter and drier years were virtually identical. The wet season diurnal cycle of precipitation in the study area varied regionally, intraseasonally, and interannually. Analysis of precipitation versus time revealed different diurnal cycles for each of the three 10° zones south of the Sahara Desert. The diurnal cycle was bimodal north of 10°N and unimodal south of 10°N. The bimodal diurnal cycle was more pronounced north of 15°N. Diurnal cycles in each zone exhibited regional and seasonal variability of about 10% per four-hour time block. In wetter years the regional mean diurnal cycle was unimodal, but in drier years it was bimodal. The variability of the diurnal cycle appeared to be primarily influenced by variability in the frequency and life cycle of organized convective systems and thus the physical and dynamical factors responsible for their development. © 2004 American Meteorological Society."
"7101962277;6508389989;16052639100;","Comparison of a satellite based Alpine cloud climatology with observations of synoptic stations",2004,"10.1127/0941-2948/2004/0013-0233","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646054139&doi=10.1127%2f0941-2948%2f2004%2f0013-0233&partnerID=40&md5=0712a98918464c2ee7a570d67314a75b","A five-year cloud climatology (1992 to 1996) of the Alpine region in a 15-km resolution has been evaluated by means of the APOLLO cloud detection algorithm applied to daytime AVHRR data of several NOAA satellites. The study area comprises three different climatic regions, the moderate climate north of the Alps, the Alpine climate and the Mediterranean climate in the Po-valley. Synoptic observations of the total cloud cover at 40 stations have been compared to the satellite based monthly mean data. Hourly ground observations allowed to estimate the variance in the monthly mean diurnal cycle of total cloud cover due to the fact that the satellite overpass time shifts from noon to afternoon for the NOAA-11 platform and for different NOAA satellites as well. This time shift of satellite observation effects the cloud climatology only slightly, because the changes of the cloud cover between 11 and 16 UTC are in most cases considerably smaller than the year-to-year variability. Furthermore, these cloud cover variations due to the time of the day are in monthly means below the validation accuracy. The comparison of monthly means reveals an overestimation of the satellite cloud cover of about 10% mainly due to additional detection of thin cirrus. A good agreement is found in the Alpine and rural moderate climates (corr. coeff. r > 0.75), whereas the cloud detection in the satellite data is too high in the Mediterranean zone due to urban and aerosol haze effects. In both data sets a rather small amplitude of the annual cycle of cloud cover results in the mountains compared to the lowlands. The high spatial variability of cloud cover in mountainous terrain is obvious with the satellite data and is substantiated by the sparse synoptic stations within the Alps. © Gebrüder Borntraeger, Berlin, Stuttgart 2004."
"57193569920;","Variation of snow/ice-extent and cloud coverage of the Alps as seen from NOAA operational satellites imager",2004,"10.1127/0941-2948/2004/0013-0245","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646023712&doi=10.1127%2f0941-2948%2f2004%2f0013-0245&partnerID=40&md5=0f0248c9c57ea7af16896aaf1e503232","The extent of snow and glacier ice in the Alps is characterized by annual, seasonal and - at least for snow - inner-seasonal variations. The knowledge of these variations is of increasing importance for the water management of the Alpine and abutting countries. By classifying imager data of the polar orbiting satellites and the additional use of a Geographical Information System (GIS) a monitoring of snow/ice extent is possible. This is exemplary performed in this study using AVHRR/3 data of the time range December 2002 to May 2003. The classification of the satellite data is done by multispectral threshold techniques taking account for underlying landuse and topography data and recent atmospheric profiles as forecasted by the global model GME of the German Weather Service (DWD). The automatic cloud masking based on NOAA 15 and 16 scenes fulfilling the condition of a sun zenith angle less than 90 turned out to be in good agreement to cloud coverage estimated by central Alpine SYNOP-stations. Applying the GIS functionality enables the evaluation of the snow/ice conditions with regard to the given topography. Time series of the relative coverage for predefined regions-of-interests reveal an accumulation phase in early winter, fluctuations of the order of several percent during the winter and the beginning of the snow melt in March and its continuation, interrupted by a late winter intermezzo happening in the first days of April 2003. © Gebrüder Borntraeger, Berlin, Stuttgart 2004."
"7004219663;","Impact of atmospheric CO2 and galactic cosmic radiation on Phanerozoic climate change and the marine δ18O record",2004,"10.1029/2003GC000683","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38549181818&doi=10.1029%2f2003GC000683&partnerID=40&md5=3b7227a0e9efd0be202ee8c9cf62f242","A new model is developed and applied to simulate the Phanerozoic evolution of seawater composition (dissolved Ca, Sr, dissolved inorganic carbon, alkalinity, pH, δ818O), marine carbonates (Sr/Ca, 87Sr/86Sr, δ13C, δ18O), atmospheric CO2 and surface temperature. The marine carbonate records (Sr/Ca, 87Sr/86Sr, δ13C) are used to reconstruct changes in volcanic/tectonic activity and organic carbon burial over the Phanerozoic. Seawater pH is calculated assuming saturation with respect to calcite and considering the changing concentration of dissolved Ca documented by brine inclusion data. The depth of calcite saturation is allowed to vary through time and the effects of changing temperature and pressure on the stability constants of the carbonate system are considered. Surface temperatures are calculated using the GEOCARB III approach considering also the changing flux of galactic cosmic radiation (GCR). It is assumed that GCR cools the surface of the Earth via enhanced cloud formation at low altitudes. The δ18O of marine carbonates is calculated considering the changing isotopic composition of seawater, the prevailing surface temperatures and seawater pH. Repeated model runs showed that the trends observed in the marine δ18O record can only be reproduced by the model if GCR is allowed to have a strong effect on surface temperature. The climate evolution predicted by the model is consistent with the geological record. Warm periods (Cambrian, Devonian, Triassic, Cretaceous) are characterized by low GCR levels. Cold periods during the late Carboniferous to early Permian and the late Cenozoic are marked by high GCR fluxes and low pCO2 values. The major glaciations occurring during these periods are the result of carbon cycling processes causing a draw-down of atmospheric CO2 and a coevally prevailing dense cloud cover at low-altitudes induced by strong GCR fluxes. The two moderately cool periods during the Ordovician - Silurian and Jurassic - early Cretaceous are characterized by both high pCO2 and GCR levels so that greenhouse warming compensated for the cooling effect of low-altitude clouds. The very high Jurassic δ18O values observed in the geological record are caused by low pH values in surface waters rather than cold surface conditions. Copyright 2004 by the American Geophysical Union."
"36523706800;8571302000;6603808469;15071768600;7004515562;6506196218;6507822486;6602699701;56630712200;6505913116;7005456532;7003463582;","Rethinking satellite-based solar irradiance modelling: The SOLIS clear-sky module",2004,"10.1016/j.rse.2004.02.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2542603815&doi=10.1016%2fj.rse.2004.02.009&partnerID=40&md5=4517f86fd9e5241c60c2bbfc88a23360","Accurate solar irradiance data are not only of particular importance for the assessment of the radiative forcing of the climate system, but also absolutely necessary for efficient planning and operation of solar energy systems. Within the European project Heliosat-3, a new type of solar irradiance scheme is developed. This new type will be based on radiative transfer models (RTM) using atmospheric parameter information retrieved from the Meteosat Second Generation (MSG) satellite (clouds, ozone, water vapour) and the ERS-2/ENVISAT satellites (aerosols, ozone). This paper focuses on the description of the clear-sky module of the new scheme, especially on the integrated use of a radiative transfer model. The linkage of the clear-sky module with the cloud module is also briefly described in order to point out the benefits of the integrated RTM use for the all-sky situations. The integrated use of an RTM within the new Solar Irradiance Scheme SOLIS is applied by introducing a new fitting function called the modified Lambert-Beer (MLB) relation. Consequently, the modified Lambert-Beer relation and its role for an integrated RTM use are discussed. Comparisons of the calculated clear-sky irradiances with ground-based measurements and the current clear-sky module demonstrate the advantages and benefits of SOLIS. Since SOLIS can provide spectrally resolved irradiance data, it can be used for different applications. Beside improved information for the planning of solar energy systems, the calculation of photosynthetic active radiation, UV index, and illuminance is possible. © 2004 Elsevier Inc. All rights reserved."
"7006303509;7006698304;","Evaluation of tropical cirrus cloud properties derived from ECMWF model output and ground based measurements over Nauru Island",2004,"10.1029/2004GL019539","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4143134225&doi=10.1029%2f2004GL019539&partnerID=40&md5=fbb81a1c1dfed05618a1bca37b4e189d","Cirrus clouds play an important role both radiatively and dynamically in the tropics. Understanding the mechanisms responsible for the formation and persistence of tropical cirrus is an important step in accurately predicting cirrus in forecast and climate models. In this study, we compare ground-based measurements of cloud properties with those predicted by the ECMWF model at a location in the tropical western Pacific. Our comparisons of cloud height and optical depth over an 8 month time period indicate that the model and measurements agree well. The ECMWF model predicts cirrus anvils associated with deep convection during convectively active periods, and also isolated cirrus events that are influenced by large-scale vertical ascent. We also show through examination of an upper tropospheric cirrus case that the model produces tropospheric waves that appear to influence the morphology and maintenance of the cirrus layer. Copyright 2004 by the American Geophysical Union."
"24827532700;6603745487;","Changes of the diurnal cycle structures of selected meteorological parameters of Potsdam Station for the summer season",2004,"10.3354/cr026131","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4344649761&doi=10.3354%2fcr026131&partnerID=40&md5=50a10704ad5fc3513fc2f9edad625eb2","Using cluster analysis, patterns of diurnal cycles were calculated based on hourly values of temperature, cloud cover, sunshine frequency, vapour pressure and relative humidity at Potsdam Station for the period June to August 1893-2000. It was shown that the large-scale climate variations of the last century are reflected in the temporal behaviour in some of these patterns. These temporal changes occur in a highly differentiated manner over the day. Additionally, relationships between the investigated parameters and precipitation and also the appearance of extremes were considered. © Inter-Research 2004."
"7003627515;6505508443;7004326742;","Surface radiation balance in Antarctica as measured with automatic weather stations",2004,"10.1029/2003JD004394","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3342985693&doi=10.1029%2f2003JD004394&partnerID=40&md5=ddcee0f15e05745b836571caa00b2be8","We present 4 years of near-surface radiation balance observations of four Antarctic automatic weather stations (AWS). The AWS are situated along a traverse line in Dronning Maud Land, connecting the coastal ice shelf and the inland plateau via the katabatic wind zone, covering the three major climate regimes of East Antarctica. Important differences in the radiation balance of the three regions are found. Clouds not only limit atmospheric transmissivity for shortwave radiation but also strongly enhance the albedo for the shortwave radiation that reaches the surface. As a result, the snow surface of the coastal ice shelves absorbs up to 65% less shortwave radiation in high summer than at the high plateau, where cloudy episodes and precipitation events are less frequent. In winter, over the slopes katabatic winds maintain a continuous turbulent transport of sensible heat toward the surface, which enhances outgoing longwave radiation. As a result, the katabatic wind zone shows the largest longwave and all-wave radiation loss in winter and over the year. Clear-sky effective emissivity for incoming longwave radiation shows great spatial variability resulting from differences in vertical temperature and moisture profiles among, the various climate, zones. Copyright 2004 by the American Geophysical Union."
"6701626212;7003641049;57202245193;35617202100;7404250633;6701802669;7202694513;","Precipitation over the interior East Antarctic Ice Sheet related to midlatitude blocking-high activity",2004,"10.1175/1520-0442(2004)017<1914:POTIEA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442675034&doi=10.1175%2f1520-0442%282004%29017%3c1914%3aPOTIEA%3e2.0.CO%3b2&partnerID=40&md5=90cfdc6eb4ebeccb5e84dd5bb0bc3dfa","Intermittent atmospheric blocking-high activity in the South Tasman Sea is shown to play a key role in delivering substantial snowfall as far south as at least 75°S on the central East Antarctic Ice Sheet plateau. Typically, cyclones fail to penetrate this far (> 1000 km) inland, and accumulation was thought to be dominated by clear-sky precipitation. In East Antarctica, the meridional cloud bands delivering the moisture originate from as far north as 35°-40°S, and appear to preferentially pass over the East Antarctic coast in a corridor from ∼ 120° to 160°E. Comparison of surface observations, model, and satellite data suggests that a few such episodes contribute a significant proportion of the (low) mean annual accumulation of the central East Antarctic Ice Sheet (e.g., an estimated 44% at Dome C over 18 days in December 2001-January 2002). Blocking-high-related incursions also cause abrupt increases in the surface wind speed (snow redistribution) and air temperature; this has implications for the interpretation of ice core data. Blocking-high-related precipitation episodes can generally be detected over the ice sheet interior, via abrupt changes (of ∼0.02-0.04) in polarization in 37- and 85-GHz SSM/I data, due to the relative stability of the surface and its ""background"" microwave signature and the relative lack of cloud cover overall. This is not the case in high-accumulation near-coastal regions such as Law Dome, where additional information is required. Ambiguities remain due to blowing snow and hoarfrost formation. Further research is necessary to examine the frequency of occurrence and variability of midlatitude blocking-high systems, their effect on precipitation in the Antarctic Ice Sheet interior, and the potential effect of global change. © 2004 American Meteorological Society."
"7401984344;7004442182;","Variations in low cloud cover over the United States during the second half of the twentieth century",2004,"10.1175/1520-0442(2004)017<1883:VILCCO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442575694&doi=10.1175%2f1520-0442%282004%29017%3c1883%3aVILCCO%3e2.0.CO%3b2&partnerID=40&md5=253b50ac4812748fd8c6662c5c2cb799","Several changes in U.S. observational practice [in particular, the introduction of the Automated Surface Observing System (ASOS) in the early 1990s] have led to a challenging heterogeneity of time series of most ground-based cloud observations. In this article, an attempt is made to preserve/restore the time series of average low cloud cover (LCC) over the country up to the year 2001 using cloud sky condition and cloud-base height information collected in the national archive data and to describe its spatial and temporal variability. The switch from human observations to ASOS can be bridged through the use of frequency of overcast/broken cloudiness. During the past 52 yr. the nationwide LCC appears to exhibit a significant increase but all of this increase occurred prior to the early 1980s and thereafter tends to decrease. This finding is consistent with similar changes in the frequency of days with precipitation. When the cloud-type information was still available (i.e., during the pre-ASOS period), it was found that the overall LCC increase was due to the increase in stratiform and cumulonimbus cloud occurrences while cumulus cloud frequency decreased. © 2004 American Meteorological Society."
"6603051342;","Nocturnal cloud systems and the diurnal variation of clouds and rainfall in southwestern Amazonia",2004,"10.1175/1520-0493(2004)132<1201:NCSATD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442712425&doi=10.1175%2f1520-0493%282004%29132%3c1201%3aNCSATD%3e2.0.CO%3b2&partnerID=40&md5=e4a573d7e615da2975e2405f6589fa5a","This paper examines the origins of a secondary nocturnal maximum in cloudiness and precipitation in southwestern Amazonia, a diurnal feature observed previously by many investigators. Analysis is based on satellite, radar, sounding, and profiler observations of precipitating systems and cloudiness from the Tropical Rainfall Measuring Mission Large-Scale Biosphere-Atmosphere (TRMM-LBA) and the coincident Wet-Season Atmospheric Mesoscale Campaign (WETAMC) field programs during the early 1999 wet season. The general finding is that following the collapse of the nearly ubiquitous and locally generated afternoon (""noon balloon"") convection, organized deep convection contributes to a postmidnight maximum in raining area and high cloudiness, and to a lesser extent rainfall. Nocturnal convective systems have the effect of weakening and delaying the onset of the following afternoon's convection. Many of these nocturnal convective events are traced to large-scale squall lines, which propagate westward thousands of kilometers from their point of origin along the northeast coast of Brazil. In addition, a previously undescribed nocturnal stratiform drizzle phenomenon, generated above the melting layer independently from deep convection, contributes significantly to nocturnal cloud cover. Results from this study underscore the complex influence of propagating large-scale organized convection in locally modulating the diurnal variation in clouds and rain. The greatest significance of the nocturnal drizzle may be the potential effect on the diurnal radiation budget by the extensive midlevel nocturnal clouds rather than their marginal contribution to nocturnal rainfall. © 2004 American Meteorological Society."
"7102092302;7003902659;","Real-time sky-view factor calculation and approximation",2004,"10.1175/1520-0426(2004)021<0730:RSFCAA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442638710&doi=10.1175%2f1520-0426%282004%29021%3c0730%3aRSFCAA%3e2.0.CO%3b2&partnerID=40&md5=9758412d197eeb1f0e1a888d62052cc9","Previously, the acquisition of sky-view factor data for climate studies has been time consuming and dependent on postprocessing. However, advances in technology now mean that techniques using fish-eye imagery can be algorithmically processed in real time to provide an instant calculation of the sky-view factor. Although data collection is often limited due to the need to survey under homogenous overcast skies, vast datasets can now be rapidly assembled for the training of proxy ""all weather"" techniques. An artificial neural network is used to estimate the sky-view factor using raw global positioning system (GPS) data and is shown to explain over 69% of the variation of the sky-view factor in urban areas. © 2004 American Meteorological Society."
"57197167176;6506672122;7004777301;7004877677;","Atmospheric laser communication new challenges for applied meteorology",2004,"10.1175/BAMS-85-5-725","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042604639&doi=10.1175%2fBAMS-85-5-725&partnerID=40&md5=93844e92eddd57a2c5a26bfb3a31c32e","Atmospheric laser communication, often referred to as free-space optics (FSO) or free-space laser (FSL) communication, is similar to fiber optic cable in terms of carrier wavelength and bandwidth capability, but data are transmitted directly through the atmosphere via laser beams over paths from a few meters to 4 km or longer. FSL uses lasers in the near-infrared spectrum, typically at wavelengths of 850 or 1550 nm. Given these wavelengths, atmospheric attenuation must be considered, and an adequate margin of optical power (dB) must exist to support high system availability (the percentage of time that an FSL link is in operation, typically 99.9%). A visual range of 100 m can attenuate a laser beam at a rate of nearly 130 dB km-1. For short links (&lt; 1200 m), fog and low clouds are the primary concerns. For longer links, scintillation, heavy rain, and snow frequently become issues. To address these issues, long-term climate data are analyzed to determine the frequency of occurrence of low visibilities and low-cloud ceilings. To estimate availability at a site of interest, adjustments to airport climate data are made to accommodate differences in altitude, geography, and the effects of the urban heat island. In sum, communication via FSL is a feasible alternative to fiber optic cable when atmospheric conditions are considered and properly analyzed."
"55495155800;6603685334;6603585313;57207122984;","Validation of parameterized algorithms used to derive TRMM-CERES surface radiative fluxes",2004,"10.1175/1520-0426(2004)021<0742:VOPAUT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442685188&doi=10.1175%2f1520-0426%282004%29021%3c0742%3aVOPAUT%3e2.0.CO%3b2&partnerID=40&md5=afa5d8190bc2e96cdeaab855cc8456b8","Parameterized shortwave and longwave algorithms developed at the Langley Research Center have been used to derive surface radiative fluxes in the processing of the Clouds and the Earth's Radiant Energy System (CERES) data obtained from flight aboard the Tropical Rainfall Measuring Mission (TRMM) satellite. Retrieved fluxes were validated on an instantaneous-footprint basis using coincident surface measurements obtained from the Atmospheric Radiation Measurement (ARM) program's Southern Great Plains (SGP) central facility, the ARM/SGP network of extended facilities, and a number of surface sites of the Baseline Surface Radiation Network (BSRN) and the Climate Monitoring and Diagnostics Laboratory (CMDL). Validation was carried out separately for clear-sky and all-sky conditions. For the shortwave, systematic errors varied from -12 to 10 W m-2 for clear skies and from -5 to 35 W m-2 for all-sky conditions. Random errors varied from 20 to 40 W m-2 for clear skies but were much larger (45-85 W m-2) for all-sky conditions. For the longwave, systematic errors were comparatively small for both clear-sky and all-sky conditions (0 to -10 W m-2) and random errors were within about 20 W m-2. In general, comparisons with surface data from the ARM/SGP site (especially the central facility) showed the best agreement. Large systematic errors in shortwave comparisons for some sites were related to flaws in the surface measurements. Larger errors in longwave fluxes for some footprints were found to be related to the errors in cloud mask retrievals, mostly during the nighttime. Smaller longwave errors related to potential errors in the operational analysis products used in satellite retrievals were also found. Still, longwave fluxes obtained with the present algorithm nearly meet the accuracy requirements for climate research."
"7401538490;7201844203;7403497924;7403225300;7501397529;","Tropical warm pool surface heat budgets and temperature: Contrasts between 1997/98 El Niño and 1998/99 La Niña",2004,"10.1175/1520-0442(2004)017<1845:TWPSHB>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442582958&doi=10.1175%2f1520-0442%282004%29017%3c1845%3aTWPSHB%3e2.0.CO%3b2&partnerID=40&md5=49bb5e4fb711a303613ae571387b4d05","Seasonal to interannual variations of the net surface heating (FNET) and its relationship to sea surface temperature tendency (dT,/dt) in the tropical eastern Indian and western Pacific Oceans are studied for the period October 1997-September 2000. The surface heat fluxes are derived from the Special Sensor Microwave Imager and Japanese Geostationary Meteorological Satellite radiance measurements. It is found that the magnitude of solar heating is larger than that of evaporative cooling, but the spatial variation of the latter is significantly larger than the former. As a result, the spatial patterns of the seasonal and interannual variability of FNET are dominated by the variability of evaporative cooling. Seasonal variations of FNET and dT,/dt are significantly correlated, except for the equatorial western Pacific. The high correlation is augmented by the high negative correlation between solar heating and evaporative cooling. The change of FN'ET between the 1997/98 El Niño and 1998/99 La Niña is significantly larger in the tropical eastern Indian Ocean than that in the tropical western Pacific. For the former region, reduced evaporative cooling arising from weakened winds during El Niño is generally associated with enhanced solar heating due to reduced cloudiness, leading to enhanced interannual variability of FNET. For the latter region, reduced evaporative cooling due to weakened winds is generally associated with reduced solar heating arising from increased cloudiness, and vice versa. Consequently, the interannual variability of FNET is reduced. The correlation between interannual variations of FNET and dT,/dt is weak in the tropical western Pacific and eastern Indian Oceans, indicating the importance of ocean dynamics in affecting the interannual SST variation. © 2004 American Meteorological Society."
"6701389719;6506653667;","Monitoring rainfall trends to predict adverse impacts - A case study from Sri Lanka (1964-1993)",2004,"10.1016/j.gloenvcha.2003.11.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1942537116&doi=10.1016%2fj.gloenvcha.2003.11.009&partnerID=40&md5=be6a7acced497451e6cdf753c7a9b24b","This paper describes an analysis of long-term rainfall trends in central mountainous region of Sri Lanka. A 30-year 60 rain gauge data set is analyzed to identify the trends in annual and seasonal rainfall. Inter-annual as well as intra-annual rainfall trends are investigated to understand the adverse impacts on water resources, floods and land degradation. It is found that there is a decrease in the annual rainfall in the region, while different seasons show mixed results. The March-April 1st inter-monsoon period shows the highest decrease in rainfall where almost all the rain gauges have recorded decreasing rainfall. In addition to the decreasing rainfall trend, the numbers of rainy days have reduced giving rise to an increasing rain intensity trend. In order to understand better the changes to rain intensity-frequency relation, a universal multifractal analysis was carried out where multifractal models calibrated to first and last decades of the rain series are used to estimate the intensity-frequency relations in the rainfall series. The results show that there is a decrease of inter-monsoon rainfall, while the intensities and return period of extreme events appear to become shorter. These changes could be associated with regional climate changes, and are consistent with projections related to Asia Brown Cloud phenomena. © 2003 Elsevier Ltd. All rights reserved."
"7401844779;7101886364;7003478309;8847776700;36076994600;6602137800;7102654014;7006807656;7005399437;","Sunlight transmission through desert dust and marine aerosols: Diffuse light corrections to Sun photometry and pyrheliometry",2004,"10.1029/2003JD004292","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042837559&doi=10.1029%2f2003JD004292&partnerID=40&md5=681fa0bf421ad7bd556b994e910827fe","Desert dust and marine aerosols are receiving increased scientific attention because of their prevalence on intercontinental scales and their potentially large effects on Earth radiation, climate, other aerosols, clouds, and precipitation. The relatively large size of dust and marine aerosol particles produces scattering phase functions that are strongly forward peaked. Hence Sun photometry and pyrheliometry of these aerosols are more subject to diffuse light errors than is the case for smaller aerosols. We quantify these diffuse light effects for common Sun photometer and pyrheliometer fields of view (FOV), using data on dust and marine aerosols from (1) Aerosol Robotic Network (AERONET) measurements of sky radiance and solar beam transmission and (2) in situ measurements of aerosol layer size distribution and chemical composition. Accounting for particle nonsphericity is important when deriving dust size distribution from both AERONET and in situ aerodynamic measurements. We obtain correction factors that can be applied to Sun photometer or pyrheliometer results for aerosol optical depth (AOD) or direct beam transmission. The corrections are negligible (less than ∼1% of AOD) for Sun photometers with narrow FOV (half-angle η < ∼1°), but they can be as large as 10% of AOD at 354 nm wavelength for Sun photometers with η = 1.85°. For pyrheliometers (which can have η up to ∼2.8°), corrections can be as large as 16% at 354 nm. AOD correction factors are well correlated with AOD wavelength dependence (hence Ångström exponent). We provide best fit equations for determining correction factors from Ångström exponents of uncorrected AOD spectra, and we demonstrate their application to vertical profiles of multiwavelength AOD. Copyright 2004 by the American Geophysical Union."
"25031430500;35547807400;7402469637;55087038900;6603955469;6506421883;7103004004;6508349287;","Radiation balance of the tropical tropopause layer",2004,"10.1029/2003jd004190","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18544400384&doi=10.1029%2f2003jd004190&partnerID=40&md5=0e9dc575a1424409d5737391aab97d5a","The radiation balance of the tropical tropopause layer (TTL) is examined using several different radiation codes with standard profiles compiled from observations in the tropics assuming clear sky conditions. These codes include detailed radiative transfer models and simplified codes for global climate models. The importance of the various radiatively active gases are examined. Water vapor is the most important contributor to the TTL radiation balance, but carbon dioxide and ozone also play a role. Differences in radiative heating between radiation models are mostly due to treatments of shortwave radiation. Differences between models below the TTL are due to different treatments of water vapor continuum absorption. The level of zero clear sky radiative heating, a level important for understanding the transport of air into the stratosphere, is generally found near 15 km, 125 hPa and 200°K (360 K potential temperature), consistent with previous work. Changes in time and space can modify this level by ±500 m, and individual profiles vary from these averages by ±400 m (1σ). Increases in water vapor in the TTL would tend to increase the altitude of the level at which the net heating is zero, while increases in carbon dioxide or ozone would tend to decrease this level. Clouds in the TTL tend to increase the level due to enhancements in longwave cooling above clouds. The implications for transport are discussed. Copyright 2004 by the American Geophysical Union."
"35513483300;6603788056;7004615859;7003352180;7202277933;7103350217;6603689569;16206263100;57203774512;","The hydrogen isotopic composition of water vapor entering the stratosphere inferred from high-precision measurements of δD-CH4 and δD-H2",2004,"10.1029/2003jd004003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2942527134&doi=10.1029%2f2003jd004003&partnerID=40&md5=e11ce1cf781948c23dfe8e8f590e5b96","The hydrogen isotopic composition of water vapor entering the stratosphere provides an important constraint on the mechanisms for dehydration of air ascending through the tropical tropopause layer. We have inferred the annual mean hydrogen isotopic composition of water vapor entering the stratosphere (or δD-H2O0) for the mid to late 1990s based on high-precision measurements of the hydrogen isotopic compositions of stratospheric H2 and CH4 from whole air samples collected on the NASA ER-2 aircraft between 1996 and 2000 and remote observations of δD-HO2 from the FIRS-2 far infrared spectrometer. We calculate an annual mean value for δD-H2O0 of -653 (+24/-25)‰ relative to Vienna standard mean ocean water (VSMOW). Previous inferences from balloon-borne and spacecraft remote-sensing observations are ∼20‰ lighter than the value from this analysis. We attribute the difference to an underestimation of deuterium in the molecular H2 reservoir in earlier work. This precise and more accurate value for the annual mean δD-H2O0 will be useful as a 1990's benchmark for detecting future changes in the details of the dehydration of air due to the impact of climate change on convection intensity, cloud microphysics, or tropical tropopause layer temperatures. In addition, we report a value for the total deuterium content in the three main stratospheric hydrogen reservoirs HDO, HD, and CH3D of 1.60 (+0.02/-0.03) ppbv. Copyright 2004 by the American Geophysical Union."
"6701404949;7202035883;","The diurnal cycle in circulation and cloudiness over the subtropical southeast Pacific: A modeling study",2004,"10.1175/1520-0442(2004)017<1699:TDCICA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2342461019&doi=10.1175%2f1520-0442%282004%29017%3c1699%3aTDCICA%3e2.0.CO%3b2&partnerID=40&md5=086c016eb2b1f016a9a5b88fb19a6800","The extensive and persistent deck of stratocumulus (Sc) over the subtropical southeast Pacific (SSEP) plays an important role in the regional and global climate. As in other subtropical regions, the Sc form at the top of a marine boundary layer (MBL), capped by the subsidence inversion. A distinctive feature of this subtropical deck is its pronounced dawn-to-afternoon decrease in cloud amount and liquid water path, partially associated with a regular and marked descent of the inversion base and the warming of the lower troposphere. Furthermore, coastal observations in this area reveal a diurnal cycle in air temperature encompassing up to 5 km MSL. In this work, 15-day regional numerical simulations using the fifth-generation PSU-NCAR Mesoscale Model (MM5) in November (austral spring), May (late fall), and January (summer) 2001 were used to document the mean diurnal cycle in circulation and low-level cloudiness over the SSEP. The simulated amplitude, depth, and phase of the diurnal cycle in air temperature, wind, and cloudiness at the northern coast of Chile and over open ocean compare quite favorably with their observational counterparts. Large-scale subsidence prevails over the SSEP on a daily average. Between 1 and 5 km, however, the vertical velocity exhibits a marked diurnal cycle, largely produced by a band of upward motion propagating from the southern coast of Peru into the SSEP during late afternoon and night. Such an ""upsidence wave"" was found in the three simulations. The upsidence wave produces a significant cooling, leading to a consistent diurnal cycle in air temperature in low- and midlevels over the SSEP. The impact of the vertical velocity cycle on the MBL was further studied using a 1D version of the MM5 with higher resolution. The deepening of the MBL during the upsidence period induces a more turbulent MBL and more entrainment. The warming and drying of the MBL result in a greater dissipation of the cloud layer in the afternoon, increasing the amplitude of the diurnal cycle in Sc cloud amount with respect to the cycle forced by absorption of solar radiation only. © 2004 American Meteorological Society."
"7006783796;8280879000;6506234624;9844101100;","Contrails, cirrus trends, and climate",2004,"10.1175/1520-0442(2004)017<1671:CCTAC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2342589400&doi=10.1175%2f1520-0442%282004%29017%3c1671%3aCCTAC%3e2.0.CO%3b2&partnerID=40&md5=b6812583533d55e5e0528956581e0539","Rising global air traffic and its associated contrails have the potential for affecting climate via radiative forcing. Current estimates of contrail climate effects are based on coverage by linear contrails that do not account for spreading and, therefore, represent the minimum impact. The maximum radiative impact is estimated by assuming that long-term trends in cirrus coverage are due entirely to air traffic in areas where humidity is relatively constant. Surface observations from 1971 to 1995 show that cirrus increased significantly over the northern oceans and the United States while decreasing over other land areas except over western Europe where cirrus coverage was relatively constant. The surface observations are consistent with satellite-derived trends over most areas. Land cirrus trends are positively correlated with upper-tropospheric (300 hPa) humidity (UTH), derived from the National Centers for Environmental Prediction (NCEP) analyses, except over the United States and western Europe where air traffic is heaviest. Over oceans, the cirrus trends are negatively correlated with the NCEP relative humidity suggesting some large uncertainties in the maritime UTH. The NCEP UTH decreased dramatically over Europe while remaining relatively steady over the United States, thereby permitting an assessment of the cirrus-contrail relationship over the United States. Seasonal cirrus changes over the United States are generally consistent with the annual cycle of contrail coverage and frequency lending additional evidence to the role of contrails in the observed trend. It is concluded that the U.S. cirrus trends are most likely due to air traffic. The cirrus increase is a factor of 1.8 greater than that expected from current estimates of linear contrail coverage suggesting that a spreading factor of the same magnitude can be used to estimate the maximum effect of the contrails. From the U.S. results and using mean contrail optical depths of 0.15 and 0.25, the maximum contrail-cirrus global radiative forcing is estimated to be 0.006-0.025 W m-2 depending on the radiative forcing model. Using results from a general circulation model simulation of contrails, the cirrus trends over the United States are estimated to cause a tropospheric warming of 0.2°-0.3°C decade-1, a range that includes the observed tropospheric temperature trend of 0.27°C decade-1 between 1975 and 1994. The magnitude of the estimated surface temperature change and the seasonal variations of the estimated temperature trends are also in good agreement with the corresponding observations. © 2004 American Meteorological Society."
"10243650000;6603196127;7003967390;","Effects of sea ice dynamics on the Antarctic sea ice distribution in a coupled ocean atmosphere model",2004,"10.1029/2003JC002022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042751708&doi=10.1029%2f2003JC002022&partnerID=40&md5=6b08f4c44d6d4f04e425bcf6bd6b88ea","Impact of sea ice dynamics on the Southern Ocean sea ice distribution is investigated using a coupled ocean-sea ice-atmosphere general circulation model (OAGCM) and a separate offline sea ice model driven by monthly mean climatological boundary conditions. Sea ice dynamics considerably affects sea ice distribution of the OAGCM as well as of the offline model. When sea ice dynamics (advection) is turned on, summer ice extent and winter ice thickness decrease in both models. Results of the OAGCM indicate that variation of clouds plays an important role when sea surface energy budget responds to the sea ice dynamics in summer. Surface wind field in summer responds to the sea ice dynamics so that northerly wind anomaly is directed to where sea ice retreats and air temperature is kept higher, leading to a positive feedback. In addition, meridional ocean circulation and upward ocean heat flux to the sea surface appear to be sensitive to the sea ice dynamics, which contributes to the response of winter sea ice thickness. Results obtained in the present study underline the importance of atmosphere-sea ice-ocean interaction when discussing the impact of sea ice dynamics on sea ice distribution. Copyright 2004 by the American Geophysical Union."
"57215729754;57203424410;7407805439;","Evaluation of dust activity and climate effects in North China",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642569545&partnerID=40&md5=15933baeb580ce3e7463534711c79a70","TOMS/ AI data with nearly 20 years are utilized in the paper to evaluate dust activities in North China. Combined with simultaneous NCEP reanalysis climate data, climate effects on dust activities are assessed. The results showed that the whole North China suffers impact by dust aerosols, with three centers standing out in TOMS/ AI spring average map that are western three basins, which are characterized by lower annual precipitation and elevation. Gobi deserts in Mongolia Plateau do not attain higher TOMS/ Al value due to cloud contamination and relative higher elevation. Spring is the season with the highest TOMS dust aerosol index; within the western three basins, high dust aerosol index appears in both spring and summer, especially in Tarim Basin. Wind speed in spring and precipitation in previous rainy season play important roles in controlling dust activities, higher wind speed and less precipitation than the normal are in favor of dust activities in spring. Temperature in spring and previous winter also affect dust activity to a certain extent, but with contrary spatial distribution. Temperature in winter exert effect principally in west part, contrarily, temperature effect in spring is mainly shown in east part. Both of them have negative correlation with dust activity."
"55633197600;7004038653;6504779649;6507638023;6504724207;7005794379;6602462985;6508056640;7203047788;6506175820;6507282341;","Mineral particles in cloud droplets produced in an artificial cloud experimental system (ACES)",2004,"10.1080/02786820490422871","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442662686&doi=10.1080%2f02786820490422871&partnerID=40&md5=cb3a7557b23b4de6a9fe31e9a9325a2e","An instrument that collects cloud droplets one by one was designed to measure the fraction of cloud droplets containing mineral particles. Sampling was performed in the artificial cloud experimental system (ACES) established in the vertical shaft of an abandoned mine. The collected droplets were observed with a scanning electron microscope (SEM), and their constituents were analyzed by an energy dispersive X-ray analyzer (EDX). The ratio of droplets including mineral particles was above 50%, reflecting the high concentration of mineral particles at the bottom of the shaft. When small droplets were sprayed by an industrial fog generator at the bottom of the shaft, the fraction of cloud droplets with mineral particles decreased but remained above 20%. This result suggests that mineral particles in the free atmosphere may also act as cloud condensation nuclei and be incorporated into cloud droplets at the early stage of cloud formation. Significant influences on the climate model, biogeochemistry, and atmospheric chemistry should be considered."
"6701682533;","Impact of global warming and locally changing climate on tropical cloud forest bats",2004,"10.1644/BWG-016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16544369445&doi=10.1644%2fBWG-016&partnerID=40&md5=0cf44514341f5f9053219c3bfd804f0f","Significant changes in local climate and correlated changes in non mammalian vertebrate populations have been documented in the Monteverde cloud forest in the Tileran Mountains of northern Costa Rica, leading to the prediction that corroborative changes should occur in bat populations. Habitat changes resulting from development for ecotourism, including a 19% increase in forest, might also be expected to impact bat populations. Analysis of data collected between 1973 and 1999 in Monteverde supports the hypothesis, although changes are less dramatic than those shown for birds, reptiles, and amphibians in earlier studies. Capture rates did not change significantly during the 27 year sample period, but relative species abundance increased, and at least 24 new species (of mostly lowland distribution) were recorded in the study area during the 1980s, 1990s, and through early 2002. These changes are likely a consequence of climatic change following global warming, forest clearing, and an increase in amount of secondary forest. This latter factor is a result of changes in land use due to development for tourism."
"57214957727;57214957433;","CCN activation of slightly soluble organics: The importance of small amounts of inorganic salt and particle phase",2004,"10.1111/j.1600-0889.2004.00090.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1942520333&doi=10.1111%2fj.1600-0889.2004.00090.x&partnerID=40&md5=cbfa68e8993a9feeda4dc7d6778ee5cd","Using a static thermal-gradient diffusion cloud condensation nucleus chamber we study the effect of small amounts of inorganic salts on the cloud droplet activation of two slightly soluble organic aerosol components (adipic and succinic acid) and experimentally confirm the two maxima predicted by Köhler theory modified to take limited solubility into account. Equally importantly we suggest (and confirm experimentally) that solid and liquid (supersaturated) particles of slightly soluble organic compounds follow two different Köhler curves and that knowledge about the particle phase and thereby the humidity history is important for interpretation of experimental data and modelling of the aerosol indirect climate effect. © Blackwell Munksgaard, 2004."
"35353151900;7202330299;36984879800;6506175295;7202444684;","Radiative properties of mid-latitude frontal ice-clouds observed by the shortwave and longwave radiometer-sondes",2004,"10.2151/jmsj.2004.639","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242784010&doi=10.2151%2fjmsj.2004.639&partnerID=40&md5=04569f9aa4f05c85a544b63e869bf435","In the Japanese Cloud and Climate Study (JACCS) cirrus experiment, simultaneous measurements of cloud radiative and microphysical properties were conducted by using the combined-sonde (radiometer-sonde + hydrometeor-video-sonde (HYVIS)) observation system at the Meteorological Research Institute (MRI), located at (36.05°N, 140.13°E) in Tsukuba, Japan, during early summer seasons from 1995 to 1999. We have analyzed the radiative properties of frontal ice-clouds observed by the shortwave and longwave radiometer-sondes (Asano et al. 2004). To interpret the observed radiative flux profiles, we have also performed radiative transfer calculations for horizontally homogeneous atmospheric models, where the single-scattering properties of ice-clouds were computed by anomalous diffraction theory for ice-crystals observed by HYVIS. On an average of the observed frontal ice-clouds, the shortwave reflectance, transmittance and absorptance were estimated to be 0.41 ± 0.03, 0.51 ± 0.06, and 0.08 ± 0.09, respectively, for the averaged ice-cloud layer with a mean visible optical thickness of 4.6 and a mean geometrical thickness of 5.4 km (mean volume extinction coefficient of 0.85 km-1). The ice-clouds were significantly heated by absorption of solar radiation in daytime. On the other hand, the mean effective emittance was estimated to be about 0.86 ± 0.37, showing that the frontal ice-clouds never acted as blackbody for longwave radiation. The lower parts of ice-cloud layers were heated by absorption of long-wave radiation from the surface and the atmosphere below the ice-clouds, while the upper parts were cooled by emission of longwave radiation to space. The shortwave and longwave heating profiles could make the daytime ice-cloud layers thermodynamically unstable. © 2004, Meteorological Society of Japan."
"26643251000;7003613864;8724549600;7102578937;","The determination of the atmospheric optical thickness over Western Europe using SeaWiFS imagery",2004,"10.1109/TGRS.2003.819880","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442522682&doi=10.1109%2fTGRS.2003.819880&partnerID=40&md5=968a8eb32d851592912a276c3cef6dcf","The first results obtained from the aerosol-cloud retrieval algorithm (developed at the University of Bremen) are presented. The algorithm enables the observation of the regional characteristics of aerosol and cloud optical thickness both over land and ocean surfaces. The aerosol and cloud optical thickness over Western Europe is derived from the high-resolution SeaWiFS data for October 11, 2001 (11:30 UTC). The most probable value of the aerosol optical thickness was found to be equal approximately 0.25. The frequency distributions of the aerosol and cloud optical thickness are skewed and have long tails for larger optical thickness. It was found that retrieved values of the aerosol optical thickness at wavelengths 0.412 and 0.440 μm are close to those measured by five ground-based instruments placed at different locations. The problems related to the retrieval of the atmospheric optical thickness from space are discussed."
"7006518289;7005965757;6701508272;7202699757;","Factors affecting climate sensitivity in global coupled models",2004,"10.1175/1520-0442(2004)017<1584:FACSIG>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2042527678&doi=10.1175%2f1520-0442%282004%29017%3c1584%3aFACSIG%3e2.0.CO%3b2&partnerID=40&md5=3b74b796de1153966deecdaaeb2053bc","Four global coupled climate models with different combinations of atmosphere, ocean, land surface, and sea ice components are compared in idealized forcing (1% CO2 increase) experiments. The four models are the Climate System Model (CSM), the Parallel Climate Model (PCM), the PCM/CSM Transition Model (PCTM), and the Community Climate System Model (CCSM). The hypothesis is posed that models with similar atmospheric model components should show a similar globally averaged dynamically coupled response to increasing CO2 in spite of different ocean, sea ice, and land formulations. Conversely, models with different atmospheric components should be most different in terms of the coupled globally averaged response. The two models with the same atmosphere and sea ice but different ocean components (PCM and PCTM) have the most similar response to increasing CO2, followed closely by CSM with comparable atmosphere and different ocean and sea ice from either PCM or PCTM. The fourth model, CCSM, has a different response from the other three and, in particular, is different from PCTM in spite of having the same ocean and sea ice but different atmospheric model component. These results support the hypothesis that, to a greater degree than the other components, the atmospheric model ""manages"" the relevant global feedbacks including sea ice albedo, water vapor, and clouds. The atmospheric model also affects the meridional overturning circulation in the ocean, as well as the ocean heat uptake characteristics. This is due to changes in surface fluxes of heat and freshwater that affect surface density in the ocean. For global sensitivity measures, the ocean, sea ice, and land surface play secondary roles, even though differences in these components can be important for regional climate changes. © 2004 American Meteorological Society."
"14013504500;7004479957;","A new parameterization for shallow cumulus convection and its application to marine subtropical cloud-topped boundary layers. Part II: Regional simulations of marine boundary layer clouds",2004,"10.1175/1520-0493(2004)132<0883:ANPFSC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642308011&doi=10.1175%2f1520-0493%282004%29132%3c0883%3aANPFSC%3e2.0.CO%3b2&partnerID=40&md5=1a4bc1e2fc9e4b1850663efad8dcac63","The impact of physical parameterizations on simulations of cloud-topped marine boundary layers is investigated using the fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5). Three-month MM5 simulations of the northeast and southeast Pacific during June-August 1987 are boundary forced with time-varying ECMWF analyses. Runs with four planetary boundary layer (PBL) parameterizations already implemented in MM5 are compared with runs using new parameterizations of boundary layer turbulence and shallow cumulus convection (ShCu) described in a companion paper. Numerous modifications to the MM5 that allow it to be used as a regional climate model are described. The simulated 3-month mean shortwave cloud radiative forcing (SWCF) and vertical structure of cloud-topped boundary layers in the northeast Pacific are sensitive to the PBL/shallow convection schemes. All four current MM5 PBL schemes [the Blackadar, Medium-Range Forecast (MRF), Burk-Thompson, and Gayno-Seaman schemes] produce overly shallow boundary layers with excessive SWCF throughout this region, especially in the transition from stratocumulus to trade cumulus where their SWCF errors range from 130 (Gayno-Seaman) to 200 W m-2 (MRF). These errors likely reflect inadequate vertical mixing by parameterized turbulence and shallow convection. The only shallow convection scheme available for MM5, the Grell scheme, was almost totally inactive in this region, so no shallow convection scheme was used for the above simulations. The Grenier-Bretherton (GBO1) scheme, which entrains more aggressively above stratocumulus-capped convective layers, has much better regional SWCF and vertical structure. Without shallow cumulus convection, the scheme still produces excessive cloud in the transition regions: the main impact of the ShCu parameterization is to remove this bias. With all schemes, the near-surface air has a cool, dry bias, and surface turbulent fluxes are somewhat larger than observed. Sensitivity studies show that the SWCF is sensitive to a halving of the cloud droplet concentration, ti plausible uncertainties in parameterized penetrative mixing at cumulus cloud tops and in stratocumulus entrainment, and (in the coastal zone) to horizontal resolution. Southeast Pacific simulations show that the GB01 + ShCu schemce can also accurately represent another subtropical boundary layer cloud regime. © 2004 American Meteorological Society."
"7405614202;7403931916;7402516470;7201826462;7407116104;7005741798;7101677832;","Inference of ice cloud properties from high spectral resolution infrared observations",2004,"10.1109/TGRS.2003.822752","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442542681&doi=10.1109%2fTGRS.2003.822752&partnerID=40&md5=6a429e1142b6a31f1e7a6dcd83f83d8b","The theoretical basis is explored for inferring the microphysical properties of ice clouds from high spectral resolution infrared (IR) observations. Extensive radiative transfer simulations are carried out to address relevant issues. The single-scattering properties of individual ice crystals are computed from state-of-the-art light scattering computational methods and are subsequently averaged for 30 in situ particle size distributions and for four additional analytical Gamma size distributions. The nonsphericity of ice crystals is shown to have a significant impact on the radiative signatures in the IR spectrum. Furthermore, the errors associated with the use of the Henyey-Greenstein phase function can be larger than 1 K in terms of brightness temperature for large particle effective sizes (∼ 80 μm) at wavenumbers where the scattering of the IR radiation by ice crystals is not negligible. The simulations undertaken in this paper show that the slope of the IR brightness temperature spectrum between 790-960 cm-1 is sensitive to the effective particle size. Furthermore, a strong sensitivity of the IR brightness temperature to cloud optical thickness is noted within the 1050-1250-cm-1 region. Based on these spectral features, a technique is presented for the simultaneous retrieval of the visible optical thickness and effective particle size from high spectral resolution IR data for ice clouds. An error analysis shows that the uncertainties of the retrieved optical thickness and effective particle size have a small range of variation. The error for retrieving particle size in conjunction with an uncertainty of 5 K in cloud temperature, or a surface temperature uncertainty of 2.5 K, is less than 15%. The corresponding errors in the uncertainty of optical thickness are within 5% to 20%, depending on the value of cloud optical thickness. The applicability of the present retrieval technique is demonstrated using airborne high-resolution IR measurements obtained during two field campaigns."
"7004034323;7006019301;7402254888;","Simulation of the diurnal cycle in a climate model and its evaluation using data from Meteosat 7",2004,"10.1256/qj.03.165","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2942511200&doi=10.1256%2fqj.03.165&partnerID=40&md5=191f9ba92a557a57c1deb6b23c910166","The representation of the diurnal cycle in the Hadley Centre climate model is evaluated using simulations of the infrared radiances observed by Meteosat 7. In both the window and water vapour channels, the standard version of the model with 19 levels produces a good simulation of the geographical distributions of the mean radiances and of the amplitude of the diurnal cycle. Increasing the vertical resolution to 30 levels leads to further improvements in the mean fields. The timing of the maximum and minimum radiances reveals significant model errors, however, which are sensitive to the frequency with which the radiation scheme is called. In most regions, these errors are consistent with well documented errors in the timing of convective precipitation, which peaks before noon in the model, in contrast to the observed peak in the late afternoon or evening. When the radiation scheme is called every model time step (half an hour), as opposed to every three hours in the standard version, the timing of the minimum radiance is improved for convective regions over central Africa, due to the creation of upper-level layer-cloud by detrainment from the convection scheme, which persists well after the convection itself has dissipated. However, this produces a decoupling between the timing of the diurnal cycles of precipitation and window channel radiance. The possibility is raised that a similar decoupling may occur in reality and the implications of this for the retrieval of the diurnal cycle of precipitation from infrared radiances are discussed. © Royal Meteorological Society, 2004."
"6506286471;55637266800;6701742258;6507994712;","Influence of sea ice treatment in a regional climate model on boundary layer values in the fram strait region",2004,"10.1175/1520-0493(2004)132<0985:IOSITI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-9944239252&doi=10.1175%2f1520-0493%282004%29132%3c0985%3aIOSITI%3e2.0.CO%3b2&partnerID=40&md5=ad41abd39cec9a86091544047ab70807","The influence of two simple descriptions for the sea ice distribution on boundary layer values is investigated by comparing model results from the regional climate model REMO with measured data in the Fram Strait in April 1999. One method for determining the sea ice distribution in REMO is to diagnose the sea ice cover from the prescribed surface temperature and allow each grid cell to be either completely free of ice or completely covered by ice (REMO-original). The other one is to employ a partial sea ice concentration in each REMO grid cell with the input data derived from satellite data (REMO-partial). Surface fluxes are average values of the ice and water partial fluxes. There is a clearly better agreement between measured and simulated surface and boundary layer temperatures and humidities when using REMO-partial compared to REMO-original. The closed ice cover in REMO-original leads to downward sensible heat fluxes over ice, whereas the ice cover with leads and polynyas in REMO-partial leads to smaller downward or even upward sensible heat fluxes. The introduction of the partial sea ice concentration smoothes unrealistically sharp gradients between ice-covered and ice-free regions, which can influence cloud cover and precipitation. An additional result of the study is that the simulation of the albedo could be improved in allowing a larger range of sea ice albedos and introducing a water albedo dependent on sun zenith angle. © 2004 American Meteorological Society."
"56277556200;12809714700;","Intraseasonal variability of the low-level jet stream of the Asian summer monsoon",2004,"10.1175/1520-0442(2004)017<1449:IVOTLJ>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2042427906&doi=10.1175%2f1520-0442%282004%29017%3c1449%3aIVOTLJ%3e2.0.CO%3b2&partnerID=40&md5=30e47f598aaa3cbf9fdb03416b2ced2c","The strong cross-equatorial low level jet stream (LLJ) with its core around 850 hPa of the Asian summer monsoon (June-September) is found to have large intraseasonal variability. During the monsoon onset over Kerala, India, and during break monsoon periods, when the convective heating of the atmosphere is over the low latitudes of the Indian Ocean, the axis of the LLJ is oriented southeastward over the eastern Arabian Sea and it flows east between Sri Lanka and the equator and there is no LLJ through peninsular India. This affects the transport of moisture produced over the Indian Ocean to peninsular India and the Bay of Bengal. In contrast, during active monsoon periods when there is an east-west band of strong convective heating in the latitudes 10°-20°N from about longitude 70° to about 120°E, the LLJ axis passes from the central Arabian Sea eastward through peninsular India and it provides moisture for the increased convection in the Bay of Bengal and for the monsoon depressions forming there. The LLJ does not show splitting into two branches over the Arabian Sea. Splitting of the jet was first suggested by Findlater and has since found wide acceptance as seen from the literature. Findlater's findings were based on analysis of monthly mean winds. Such an analysis is likely to show the LLJ of active and break monsoons as occurring simultaneously, suggesting a split. Strengths of the convective heat source (OLR) over the Bay of Bengal and the strength of the LLJ (zonal component of wind) at 850 hPa over peninsular India and also the Bay of Bengal between latitudes 10° and 20°N have the highest linear correlation coefficient a lag of 2-3 days, with OLR leading. The LLJ crossing the equator close to the coast of East Africa will pass through India only if there is active monsoon convection in the latitude belt 10°-20°N over south Asia. The position in latitude of the LLJ axis between longitudes 70° and 100°E is decided by the south-north movement of the east-west convective cloud band of the monsoon in its 30-50-day oscillation. When there is little convection over south Asia in the latitude belt 10°-20°N, the LLJ crossing the equator curves clockwise over the Arabian Sea under conservation of potential vorticity and by-passing India passes east close to the equator. It is speculated that the cyclonic vorticity associated with this low-latitude LLJ causes convergence in the boundary layer and consequent upward motion in the atmosphere resulting in the formation of a convective cloud band there that later moves into the Bay of Bengal as part of the monsoon's 30-50-day oscillation. Since LLJ is very important in monsoon dynamics, monsoon modelers should take adequate care to see that LLJ and the associated deep convection and their intraseasonal variability are properly simulated in their models. © 2004 American Meteorological Society."
"6602692238;6602600408;","Evaluation of cloud thermodynamic phase parametrizations in the LMDZ GCM by using POLDER satellite data",2004,"10.1029/2003gl019095","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18544412387&doi=10.1029%2f2003gl019095&partnerID=40&md5=d05d1496dd187d018c7c97f855d06537","Realistic simulations of clouds are of uppermost importance for climate modelling using general circulation models. Satellite data are well suited to evaluate model parametrizations. In this study we use the Laboratoire de Méteorologie Dynamique general circulation model (LMDZ). We evaluate the current LMDZ cloud phase parametrization, in which the repartition of condensed cloud water between liquid and ice is a function of the local temperature. Three parameters are used to derive a relation between liquid cloud water content and temperature, two of which are not physically based. We use the POLDER-1 satellite data to infer more realistic parameters by establishing statistical relationships between cloud top thermodynamical phase and cloud top temperature, consistently in both satellite data and model results. We then perform a multitude of short model integrations and derive a best estimate for the lowest local temperature where liquid water can exist in a cloud (Tice, = -32°C in our parametrization). The other parameter which describes the shape of the transition between ice and liquid water is also estimated. A longer simulation has then been performed with the new parameters, resulting in an improvement in the representation of the shortwave cloud radiative forcing. Copyright 2004 by the American Geophysical Union."
"7403577184;7006614696;35453054300;7202772927;","Impact of aerosols and atmospheric thermodynamics on cloud properties within the climate system",2004,"10.1029/2003gl019287","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18544403362&doi=10.1029%2f2003gl019287&partnerID=40&md5=b0c7fd25563f45e6d1af147a9f7d56df","A combination of cloud-top and columnar droplet sizes derived from the multi Tropical Rainfall Measurement Mission (TRMM) sensors reveals the sensitivity of the aerosols effect on cloud-precipitation processes due to environmental vertical thermodynamic structure. First, the magnitude of aerosol indirect effect could be larger with the analysis of columnar droplet sizes than that derived from the cloud-top droplet sizes since column-droplet size can account for the broader droplet spectra in the cloud layers. Second, a combination of cloud-top and columnar droplet sizes reveals that the warm rain process is prevented regardless of the aerosols concentration under high static stability such as when a strong temperature inversion exists, while a high aerosol concentration suppresses the warm rain formulation under low static stability. Copyright 2004 by the American Geophysical Union."
"6602729528;7003931528;57203053317;7003979342;","Can aerosols spin down the water cycle in a warmer and moister world?",2004,"10.1029/2003gl019060","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18544400972&doi=10.1029%2f2003gl019060&partnerID=40&md5=0b1331c06b731f392b012d91a43cb1a8","Surface observations show puzzling evidence of reduced solar warming and concurrent increasing temperature during the last four decades. Based on climate simulations with the general circulation model of the Max Planck Institute in Hamburg we suggest that the interactions of greenhouse gas forcing plus direct, semidirect and indirect aerosol effects on clouds explain this paradox. We argue that reductions in surface solar radiation due to clouds and aerosols are only partly offset by enhanced down-welling longwave radiation from the warmer and moister atmosphere. We conclude that the radiative imbalance at the surface leads to weaker latent and sensible heat fluxes and hence to reductions in evaporation and precipitation despite global warming. Copyright 2004 by the American Geophysical Union."
"7801344746;55905970100;","Automatic cloud amount detection by surface longwave downward radiation measurements",2004,"10.1029/2003jd004182","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642515636&doi=10.1029%2f2003jd004182&partnerID=40&md5=fbf1e73af6faa158a5a3d3710e6ca8cb","Naked-eye observation of sky cloud cover has widely resisted automation. Automatic cloud cover detection systems suitable also for nighttime operation often demand large equipment investments and expensive data processing. An automatic partial cloud amount detection algorithm (APCADA) is presented, based only on accurate measurements of longwave downward radiation, temperature, and relative humidity at screen level height. APCADA provides cloud cover estimates every 10 min during daytime and nighttime and is applicable to radiation stations without knowledge of synoptic cloud observations. Naked-eye observations from seven radiation sites spanning from arctic to tropical climates have been compared to APCADA estimates. Results show that about 86% of all cases agree within ±1-octa cloud amount difference for sites with moderate climate, 82% for sites with arctic climate, and 78% for the site with tropical climate. For a maximum ±2-octa cloud amount difference, average site percentages range from 90% up to 95%. Copyright 2004 by the American Geophysical Union."
"7102128820;55393008200;7006146719;7007114756;","Estimate of the global distribution of stratiform supercooled liquid water clouds using the LITE lidar",2004,"10.1029/2003gl018977","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442442907&doi=10.1029%2f2003gl018977&partnerID=40&md5=85a335f8190a61760354db3f4ec080c0","Supercooled liquid water clouds can occur in the form of thin layers that have a much larger radiative impact than ice clouds of the same water content because of their smaller particle size, yet they are poorly represented in climate models. Such clouds may be easily distinguished from ice by their high lidar backscatter coefficient and sharp backscatter gradient at cloud top. In this paper, data from the Lidar In-space Technology Experiment (LITE), which flew on the space shuttle in 1994, are used to estimate the fraction of clouds that contain supercooled liquid water over the latitude range ±60°. Around 20% of clouds between -10°C and -15°C were found to contain liquid water, falling with temperature to essentially zero below -35°C. Even from this limited dataset some clear latitudinal clear trends were evident, with a distinctly more frequent occurrence of supercooled water in clouds associated with mid-latitude weather systems in the southern hemisphere, as well as in tropical clouds warmer than around -15°C. The results between 40 and 60°N agree well with the distribution previously found at Chilbolton in Southern England (51°N), implying that the forthcoming long-term lidar observations from space will be able to infer the global distribution of mixed-phase clouds with much greater accuracy and vertical resolution than has been possible until now. Copyright 2004 by the American Geophysical Union."
"6603779272;57203052274;7005233878;7006550762;","Climate response to the increase in tropospheric ozone since preindustrial times: A comparison between ozone and equivalent CO2 forcings",2004,"10.1029/2003jd003653","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642511545&doi=10.1029%2f2003jd003653&partnerID=40&md5=295a132f63cefdfe783b0d3efe29d16f","We examine the characteristics of the climate response to anthropogenic changes in tropospheric ozone. Using a general circulation model, we have carried out a pair of equilibrium climate simulations with realistic present-day and preindustrial ozone distributions. We find that the instantaneous radiative forcing of 0.49 W m-2 due to the increase in tropospheric ozone since preindustrial times results in an increase in global mean surface temperature of 0.28°C. The increase is nearly 0.4°C in the Northern Hemisphere and about 0.2°C in the Southern Hemisphere. The largest increases (&gt;0.8°C) are downwind of Europe and Asia and over the North American interior in summer. In the lower stratosphere, global mean temperatures decrease by about 0.2°C due to the diminished upward flux of radiation at 9.6 μm. The largest stratospheric cooling, up to 1.0°C, occurs over high northern latitudes in winter, with possibly important implications for the formation of polar stratospheric clouds. To identify the characteristics of climate forcing unique to tropospheric ozone, we have conducted two additional climate equilibrium simulations: one in which preindustrial tropospheric ozone concentrations were increased everywhere by 18 ppb, producing the same global radiative forcing as present-day ozone but without the heterogeneity; and one in which CO2 was decreased by 25 ppm relative to present day, with ozone at present-day values, to again produce the same global radiative forcing but with the spectral signature Of CO2 rather than ozone. In the first simulation (uniform increase of ozone), the global mean surface temperature increases by 0.25°C, with an interhemispheric difference of only 0.03°C, as compared with nearly 0.2°C for the heterogeneous ozone increase. In the second simulation (equivalent CO2), the global mean surface temperature increases by 0.36°C, 30% higher than the increase from tropospheric ozone. The stronger surface warming from CO2 is in part because CO2 forcing (obscured by water vapor) is shifted relatively poleward where the positive ice-albedo feedback amplifies the climate response and in part because the magnitude of the CO2 forcing in the midtroposphere is double that of ozone. However, we find that CO2 is far less effective than tropospheric ozone in driving lower stratospheric cooling at high northern latitudes in winter. Copyright 2004 by the American Geophysical Union."
"7004993886;7005634455;7006705919;7003311618;","Antarctic clouds and radiation within the NCAR climate models",2004,"10.1175/1520-0442(2004)017<1198:ACARWT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842638680&doi=10.1175%2f1520-0442%282004%29017%3c1198%3aACARWT%3e2.0.CO%3b2&partnerID=40&md5=ac6bd961fecfa901784405c05f59e682","To evaluate and improve the treatment of clouds and radiation by the climate models of the National Center for Atmospheric Research (NCAR), simulations by the NCAR Community Climate Model version 3 (CCM3), as well as the recently released Community Atmosphere Model version 2 (CAM2), are examined. The Rasch and Kristjánsson prognostic cloud condensate scheme, which is now the standard scheme for CAM2, is included in a version of CCM3 and evaluated. Furthermore, the Rapid Radiative Transfer Model (RRTM), which alleviates the deficit in downward clear-sky longwave radiation, is also included in a version of CCM3. The new radiation scheme in CAM2 also alleviates the clear-sky longwave bias, although RRTM is not included. The impact of the changes is especially large over the interior of Antarctica. The changes induced by the introduction of the prognostic cloud scheme are found to have a much larger impact on the CCM3 simulations than do those from the introduction of RRTM. The introduction of the prognostic cloud scheme increases cloud emissivity in the upper troposphere, reduces cloud emissivity in the lower troposphere, and results in a better vertical distribution of cloud radiative properties over interior Antarctica. The climate simulations have a very large cold bias in the stratosphere, especially during summer. There are significant deficiencies in the simulation of Antarctic cloud radiative effects. The optical thickness of Antarctic clouds appears to be excessive. This contributes to a warm bias in surface temperature during winter and a deficit in downward shortwave radiation during summer. Some biases for Antarctica are larger for CCM3 with the prognostic cloud condensate scheme than with the standard diagnostic clouds. When the mixing ratio threshold for autoconversion from suspended ice cloud to falling precipitation is reduced toward a more realistic value, the Antarctic clouds are thinned and some of the biases are reduced. To improve the surface energy balance, not only must the radiative effects of clouds be improved, it is also necessary to improve the representation of sensible heat flux. Insufficient vertical resolution of the frequently very shallow, very stable surface boundary layer apparently contributes to an excessive heat flux from the atmosphere to the surface during winter. The representations of Antarctic clouds and radiation by the new NCAR CAM2 are not clearly improved compared to those of the earlier CCM3. For example, the surface albedo over Antarctica is descreased in CAM2 and Community Climate System Model version 2 (CCSM2) simulations in comparison to CCM3 simulations, contributing to a summer warm bias in tropospheric temperature for the former. © 2004 American Meteorological Society."
"6602787883;","PBL stratiform cloud inhomogeneities thermally induced by the orography: A parameterization for climate models",2004,"10.1175/1520-0469(2004)061<0644:PSCITI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842732684&doi=10.1175%2f1520-0469%282004%29061%3c0644%3aPSCITI%3e2.0.CO%3b2&partnerID=40&md5=2f77bc0ccb01b9fda176acc498c268ab","This paper proposes a parameterization for use in climate models of the orographic variance and associated thermal circulation's impact on the macroscopic behavior of planetary boundary layer (PBL) stratiform clouds. Orographically induced inhomogeneities in the PBL cloud field can significantly alter the area-averaged cloud radiative properties and consequently the PBL evolution. Current climate models do not include this effect. The design of the parameterization is based on a systematic set of experiments in which a cloud system resolving model (CSRM) explicitly simulates the diurnally varying interactions between PBL clouds and the orography for a variety of configurations. Analyses of the results suggest that the orographic effect on PBL clouds is parameterizable to a large extent due to a quasi equilibrium between cloud-radiative, turbulent, and mesoscale processes. Parameterizability holds in the range of parameters for which stratiform clouds play a dominant role in the PBL dynamics (cloud fraction ∼0.5 or larger). A statistical parameterization of the liquid water path (LWP) spatial distribution in the PBL is formulated as a function of its mean state. The component of the LWP distribution not captured by the parameterization is mostly associated with a hysteresis effect in the PBL height and decreases with increasing orographic variance. The LWP distribution is characterized by an exponentially decaying function that describes the patchy clouds and a bell-shaped function that describes the solid cloud decks. Orographic variance impacts cloud fraction and the relative area cover of the patchy and solid clouds, mainly by reducing the incidence of the latter, while the characteristic horizontal scale of the orography has little influence on PBL cloudiness. © 2004 American Meteorological Society."
"7004186785;","An 8000-year record of vegetation, climate, and human disturbance from the Sierra de Apaneca, El Salvador",2004,"10.1016/j.yqres.2004.01.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842712399&doi=10.1016%2fj.yqres.2004.01.002&partnerID=40&md5=ed20e77a98f6eb6d70f96e07c10b494c","An ∼8000-cal-yr stratigraphic record of vegetation change from the Sierra de Apaneca, El Salvador, documents a mid-Holocene warm phase, followed by late Holocene cooling. Pollen evidence reveals that during the mid-Holocene (∼8000-5500 cal yr B.P.) lowland tropical plant taxa were growing at elevations ∼200-250 m higher than at present, suggesting conditions about 1.0°C warmer than those prevailing today. Cloud forest genera (Liquidambar, Juglans, Alnus, Ulmus) were also more abundant in the mid-Holocene, indicating greater cloud cover during the dry season. A gradual cooling and drying trend began by ∼5500 cal yr B.P., culminating in the modern forest composition by ∼3500 cal yr B.P. A rise in pollen from weedy plant taxa associated with agriculture occurred ∼5000 cal yr B.P., and pollen from Zea first appeared in the record at ∼4440 cal yr B.P. Human impacts on local vegetation remained high throughout the late Holocene, but decreased abruptly following the Tierra Blanca Joven (TBJ) eruption of Volcán Ilopango at ∼1520 cal yr B.P. The past 1500 years are marked by higher lake levels and periodic depositions of exogenous inorganic sediments, perhaps indicating increased climatic variability. © 2004 University of Washington. All rights reserved."
"7005050002;7007026915;6506004306;","Regional variations in U.S. diurnal temperature range for the 11-14 September 2001 aircraft groundings: Evidence on jet contrail influence on climate",2004,"10.1175/1520-0442(2004)017<1123:RVIUDT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842639387&doi=10.1175%2f1520-0442%282004%29017%3c1123%3aRVIUDT%3e2.0.CO%3b2&partnerID=40&md5=c2bbf7271daf16067a3a1092977c3478","The grounding of all commercial aircraft within U.S. airspace for the 3-day period following the 11 September 2001 terrorist attacks provides a unique opportunity to study the potential role of jet aircraft contrails in climate. Contrails are most similar to natural cirrus clouds due to their high altitude and strong ability to efficiently reduce outgoing infrared radiation. However, they typically have a higher albedo than cirrus; thus, they are better at reducing the surface receipt of incoming solar radiation. These contrail characteristics potentially suppress the diurnal temperature range (DTR) when contrail coverage is both widespread and relatively long lasting over a specific region. During the 11-14 September 2001 grounding period natural clouds and contrails were noticeably absent on high-resolution satellite imagery across the regions that typically receive abundant contrail coverage. A previous analysis of temperature data for the grounding period reported an anomalous increase in the U.S.-averaged, 3-day DTR value. Here, the spatial variation of the DTR anomalies as well as the separate contributions from the maximum and minimum temperature departures are analyzed. These analyses are undertaken to better evaluate the role of jet contrail absence and synoptic weather patterns during the grounding period on the DTR anomalies. It is shown that the largest DTR increases occurred in regions where contrail coverage is typically most prevalent during the fall season (from satellite-based contrail observations for the 1977-79 and 2000-01 periods). These DTR increases occurred even in those areas reporting positive departures of tropospheric humidity, which may reduce DTR, during the grounding period. Also, there was an asymmetric departure from the normal maximum and minimum temperatures suggesting that daytime temperatures responded more to contrail absence than did nighttime temperatures, which responded more to synoptic conditions. The application of a statistical model that ""retro-predicts"" contrail-favored areas (CFAs) on the basis of upper-tropospheric meteorological conditions existing during the grounding period, supports the role of contrail absence in the surface temperature anomalies; especially for the western United States. Along with previous studies comparing surface climate data at stations beneath major flight paths with those farther away, the regionalization of the DTR anomalies during the September 2001 ""control"" period implies that contrails have been helping to decrease DTR in areas where they are most abundant, at least during the early fall season. © 2004 American Meteorological Society."
"7005231450;7005578774;","The diurnal cycle and its depiction in the community climate system model",2004,"10.1175/1520-0442(2004)017<0930:TDCAID>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842740306&doi=10.1175%2f1520-0442%282004%29017%3c0930%3aTDCAID%3e2.0.CO%3b2&partnerID=40&md5=899fe2b3fabda62b0e329c8d5a27a8ee","To evaluate the performance of version 2 of the Community Climate System Model (CCSM2) in simulating the diurnal cycle and to diagnose the deficiencies in underlying model physics, 10 years of 3-hourly data from a CCSM2 control run are analyzed for global and large-scale features of diurnal variations in surface air temperature, surface pressure, upper-air winds, cloud amount, and precipitation. The model-simulated diurnal variations are compared with available observations, most of which were derived from 3-hourly synoptic reports and some new results are reported for surface air temperatures. The CCSM2 reproduces most of the large-scale tidal variations in surface pressure and upper-air winds, although it overestimates the diurnal pressure tide by 20%-50% over low-latitude land and underestimates it over most oceans, the Rockies, and other midlatitude land areas. The CCSM2 captures the diurnal amplitude (1°-6°C) and phase [peak at 1400-1600 local solar time (LST)] of surface air temperature over land, but over ocean the amplitude is too small (≤0.2°C). The CCSM2 overestimates the mean total cloud amount by 10%-20% of the sky from ∼ 15°S to 15°N during both December- January-February (DJF) and June-July-August (JJA) and over northern mid- and high-latitude land areas in DJF, whereas it underestimates the cloud amount by 10%-30% in the subtropics and parts of the midlatitudes. Over the marine stratocumulus regions west to the continents, the diagnostic cloud scheme in the CCSM2 underestimates the mean stratocumulus amount by 10%-30% and does not simulate the observed large diurnal variations (∼ 3%-10%) in the marine stratocumulus clouds even when driven by observational data. In the CCSM2, warm-season daytime moist convection over land starts prematurely around 0800 LST, about 4 hours too early compared with observations, and plateaus from 1100 to 1800 LST, in contrast to a sharp peak around 1600-1700 LST in observations. The premature initiation of convection prevents convective available potential energy (CAPE) from accumulating in the morning and early afternoon and intense convection from occurring in the mid to late afternoon. As a result of the extended duration of daytime convection over land, the CCSM2 rains too frequently at reduced intensity despite the fairly realistic patterns of rainy days with precipitation &gt; 1 mm day-1. Furthermore, the convective versus nonconvective precipitation ratio is too high in the model as deep convection removes atmospheric moisture prematurely. The simulated diurnal cycle of precipitation is too weak over the oceans, especially for convective precipitation. These results suggest that substantial improvements are desirable in the CCSM2 in simulating cloud amount, initiation of warm-season deep convection over land, and in the diurnal cycle in sea surface temperatures. © 2004 American Meteorological Society."
"55474583500;6603194785;55613234984;57197445315;7202963999;7006642410;","Effects of climate and dam operations on reservoir thermal structure",2004,"10.1061/(ASCE)0733-9496(2004)130:2(112)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842787617&doi=10.1061%2f%28ASCE%290733-9496%282004%29130%3a2%28112%29&partnerID=40&md5=fa90edaa6e0e52524a66d9c35acdd88c","Recently, the United States Bureau of Reclamation agreed to increase spring releases from Upper Colorado River Basin reservoirs to create a more natural flow regime in the lower Gunnison River and Upper Colorado River. Fishery managers have expressed concern that new operations could change reservoir conditions and jeopardize popular and economically important reservoir sport fisheries. This study attempts to predict how one aspect of reservoir conditions, thermal structure, might respond to new dam operations at Blue Mesa Reservoir aimed at addressing downstream ecological concerns. A one-dimensional thermal model (CE-THERM) is applied to simulating thermal effects of ""traditional"" and proposed ""new"" dam operation scenarios. To evaluate the relative importance of climate and dam operations a sensitivity analysis of hydrologic (i.e., inflows and starting reservoir elevation) and meteorologic (i.e., air temperature, cloud cover, and dew point temperature) inputs was conducted along with an ""extreme"" dam operation scenario. Results indicate that reservoir managers at Blue Mesa Reservoir have considerable latitude for new operations without negative thermal consequences. The natural variability of climate and hydrology appear to exert stronger control over reservoir thermal structure than reservoir operations at Blue Mesa. © ASCE / MARCH/APRIL 2004."
"7004737151;","Seasonal climate summary southern hemisphere (autumn 2003): Demise of the 2002/03 El Niño event",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242806702&partnerID=40&md5=c0aba4dba4012d2c245ccfac0beed326","Southern hemisphere circulation patterns and associated anomalies for the austral autumn 2003 are reviewed, with emphasis given to the Pacific Basin climate indicators and Australian rainfall and temperature patterns. Autumn 2003 saw the complete demise of the El Niño event which began about one year earlier. Sustained cooling of surface waters occurred in the central to eastern tropical Pacific, and negative anomalies were widespread in the tropical Pacific sub-surface. Averaged over the season, the Walker circulation was enhanced and the amount of cloud around the equatorial dateline was generally close to average for the time of year. Australian rainfall patterns returned to something closer to average, although seasonal falls in many instances were insufficient to provide a clear break to the severe drought conditions. Maximum temperatures were above average over large parts of the country, but there was close to an even split between positive and negative anomalies for seasonal minima."
"14820677200;7003610507;35581962600;","Sea fog research in the United Kingdom and United States. A historical essay including outlook",2004,"10.1175/BAMS-85-3-395","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2142710194&doi=10.1175%2fBAMS-85-3-395&partnerID=40&md5=b6532a0ca6d2c1d3b0de12f79ebd047c","In the post-W.W.II era, the intricacies of sea fog were examined with the aid of numerical models, that is, numerical experiments. Results from these experiments pointed to the subtleties that resided in the mechanics of sea fog formation, namely, the delicate interplay between processes such as radiation and turbulent heat transfer at the sea-air boundary. This paper discusses these issues as well as speculation on the future of sea fog research in light of the historical contributions."
"56283402900;7006993412;36829694300;7402548443;7004402705;57192975368;","Arctic ozone loss and climate change",2004,"10.1029/2003GL018844","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2542447149&doi=10.1029%2f2003GL018844&partnerID=40&md5=0dac909982aca34906282990efbb53d0","We report the first empirical quantification of the relation between winter-spring loss of Arctic ozone and changes in stratospheric climate. Our observations show that -e1 15 DU additional loss of column ozone can be expected per Kelvin cooling of the Arctic lower stratosphere, an impact nearly three times larger than current model simulations suggest. We show that stratospheric climate conditions became significantly more favorable for large Arctic ozone losses over the past four decades; i.e., the maximum potential for formation of polar stratospheric clouds increased steadily by a factor of three. Severe Arctic ozone loss during the past decade occurred as a result of the combined effect of this long-term climate change and the anthropogenic increase in stratospheric halogens. Copyright 2004 by the American Geophysical Union."
"35461255500;26643041500;6603850285;7006712143;7006708207;","Organic aerosol formation via sulphate cluster activation",2004,"10.1029/2003jd003961","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642573415&doi=10.1029%2f2003jd003961&partnerID=40&md5=e6aa85ee1f441d43e9ff4a19024d1064","The formation of aerosols, and subsequent cloud condensation nuclei, remains one of the least understood atmospheric processes upon which global climate change critically depends. Under atmospheric conditions, the process of homogeneous nucleation (formation of stable clusters ∼ 1 nm in size), and their subsequent growth into new particles (>3 nm), determines the aerosol and cloud nuclei population, yet, hitherto, no theory has elucidated the new particle formation phenomenon in detail. In this study, we present a new theory which provides a mechanistic explanation for new particle formation via activation of stable inorganic clusters by organic vapors. The new nano-particle activation theory is analogous to Köhler theory which describes cloud formation in a supersaturated water vapor field but differs in that it describes the activation of inorganic stable nano-clusters into aerosol particles in a supersaturated organic vapor which initiates spontaneous and rapid growth of clusters. Inclusion of the new theory into aerosol formation models predicts that increases in organic vapor densities lead to even greater increases in particle production, which, in turn, will influence the global radiative cooling effect of atmospheric aerosols. Copyright 2004 by the American Geophysical Union."
"6701762451;7404062492;57192107995;7202586843;","Single particle measurements of the chemical composition of cirrus ice residue during CRYSTAL-FACE",2004,"10.1029/2003jd004032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442662188&doi=10.1029%2f2003jd004032&partnerID=40&md5=a16ff533fd82e325951973f45b0addc0","The first real-time, in situ, investigation of the chemical composition of the residue of cirrus ice crystals was performed during July 2002. This study was undertaken on a NASA WB-57F high-altitude research aircraft as part of CRYSTAL-FACE, a field campaign which sought to further our understanding of the relation of clouds, water vapor, and climate by characterizing, among other parameters, anvil cirrus formed about the Florida peninsula. A counter flow virtual impactor (CVI) was used to separate cirrus ice from the unactivated interstitial aerosol particles and evaporate condensed-phase water. Residual material, on a crystal-by-crystal basis, was subsequently analyzed using the NOAA Aeronomy Laboratory's Particle Analysis by Laser Mass Spectrometry (PALMS) instrument. Sampling was performed from 5 to 15 km altitude and from 12° to 28° north latitude within cirrus originating over land and ocean. Chemical composition measurements provided several important results. Sea salt was often incorporated into cirrus, consistent with homogeneous ice formation by aerosol particles from the marine boundary layer. Size measurements showed that large particles preferentially froze over smaller ones. Meteoritic material was found within ice crystals, indicative of a relation between stratospheric aerosol particles and tropospheric clouds. Mineral dust was the dominant residue observed in clouds formed during a dust transport event from the Sahara, consistent with a heterogeneous freezing mechanism. These results show that chemical composition and size are important determinants of which aerosol particles form cirrus ice crystals. Copyright 2004 by the American Geophysical Union."
"13310165300;6701601159;7402456930;7402480218;55464967500;","Long-term variations in the occurrence and effective solar transmission of clouds as determined from surface-based total irradiance observations",2004,"10.1029/2003jd003568","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642536810&doi=10.1029%2f2003jd003568&partnerID=40&md5=69b644de3198018eded22676989270e1","Time series of cloud solar transmission and cloud occurrence frequency are developed for the past 27 years at four globally remote and climatically diverse surface locations. A new methodology is developed that objectively segregates times of cloud-free conditions from those times when clouds are detected in high-time-resolution total solar irradiance observations that are obtained from pyranometers. The methodology for cloud detection depends on the magnitude and short-term variability of observed departures from clear-sky conditions. Expected clear-sky irradiances are based on interpolated clear-sky observations. Results of the new cloud detection methodology are compared to four independent cloud detection methods. An effective cloud transmission is determined as the ratio of observed irradiance in the presence of clouds to that expected in the absence of clouds. Selective forward scattering by clouds toward the observation site results in computed effective transmissions frequently being > 1.0. It is shown that conditional temporal averaging of effective cloud transmission over periods of three days or more virtually eliminates the unrealistic cloud transmissions exceeding 1.0. Such temporal averaging of the surface measurements is advantageous for comparing against other areawide cloud transmission estimates, such as those determined from satellite or by numerical climate models. The cloud occurrence frequency and the effective solar transmission for long-term observational records are summarized into monthly and annual averages, and their long-term variability is investigated. Temporal variations in frequency distributions of transmission are used to determine which clouds are responsible for changes in mean cloudiness. A statistically significant upward trend in cloud occurrence frequency, from 76 to 82% between 1976 and 2001, is detected at Barrow, Alaska, where clouds having solar transmission near 0.2 exhibit the largest increase. At the South Pole, decadal timescale oscillations in both cloud characteristics are detected, but no particular cloud category is identified as the source of that oscillation. Copyright 2004 by the American Geophysical Union."
"7501627905;","A modeling study on the climate impacts of black carbon aerosols",2004,"10.1029/2003jd004084","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642575022&doi=10.1029%2f2003jd004084&partnerID=40&md5=137f3e1bd75a54dc961a2f217abf1d83","A three-dimensional interactive aerosol-climate model has been developed and used to study the climatic impact of black carbon (BC) aerosols. When compared with the model's natural variability, significant global-scale changes caused by BC aerosols occurred in surface latent and sensible heat flux, surface net long-wave radiative flux, planetary boundary layer height, convective precipitation (all negative), and low-cloud coverage (positive), all closely related to the hydrological cycle. The most significant regional change caused by BC revealed in this study is in precipitation that occurs in the tropics (shift of precipitation center in the ITCZ) and in the middle and high latitudes of the Northern Hemisphere (change in snow depth). Influenced by BC caused changes in cloud cover and surface albedo, the interactive model provides smaller positive all-sky forcing at the top of atmosphere (TOA) and larger negative forcing at the surface than the offline diagnostics (the direct forcings). The actual solar radiative forcings by BC derived from the interactive model also exhibit significant interannual variations that are up to 4 times as large as their means. Based on the revealed changes in cloud radiative forcing by BC, a non-Twomey-Albrecht indirect forcing by BC that alters radiative budgets by changing cloud cover via thermodynamics rather than microphysics is also defined. It has been demonstrated that with an absolute amount more than 2 times higher than that of the TOA forcing, the surface forcing by BC is a very important factor in analyzing the climatic impact of BC. The result of this study suggests that with a constant annual emission of 14 TgC, BC aerosols do not cause a significant change in global-mean surface temperature. The calculated surface temperature change is determined by a subtle balance among changes in surface energy budget as well as in the hydrological cycle, all caused by BC forcing and often compensate each other. The result of this study shows that the influences of BC aerosols on climate and environment are more significant in regional scale than in global scale. Important feedbacks between BC radiative effects and climate dynamics revealed in this study suggest the importance of using interactive aerosol-climate models to address the issues related to the climate impacts of aerosols. Copyright 2004 by the American Geophysical Union."
"55905970100;7801344746;7006240152;57202413846;7102953444;","Radiative forcing - Measured at Earth's surface - Corroborate the increasing greenhouse effect",2004,"10.1029/2003GL018765","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18144447678&doi=10.1029%2f2003GL018765&partnerID=40&md5=0e3e25f3082e7d9ce12604738cd43821","The Intergovernmental Panel of Climate Change (IPCC) confirmed concentrations of atmospheric greenhouse gases and radiative forcing to increase as a result of human activities. Nevertheless, changes in radiative forcing related to increasing greenhouse gas concentrations could not be experimentally detected at Earth's surface so far. Here we show that atmospheric longwave downward radiation significantly increased (+5.2(2.2) Wm-2) partly due to increased cloud amount (+1.0(2.8) Wm-2) over eight years of measurements at eight radiation stations distributed over the central Alps. Model calculations show the cloud-free longwave flux increase (+4.2(1.9) Wm-2) to be in due proportion with temperature (+0.82(0.41) °C) and absolute humidity (+0.21(0.10) g m-3) increases, but three times larger than expected from anthropogenic greenhouse gases. However, after subtracting for two thirds of temperature and humidity rises, the increase of cloud-free longwave downward radiation (+1.8(0.8) Wm-2) remains statistically significant and demonstrates radiative forcing due to an enhanced greenhouse effect. Copyright 2004 by the American Geophysical Union."
"7404812403;57196396429;7006861646;55505923400;","Upper tropospheric drying and the ""transition to break"" in the Indian summer monsoon during 1999",2004,"10.1029/2003GL018269","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18144439806&doi=10.1029%2f2003GL018269&partnerID=40&md5=dc66f19aa181b717c51a54a50860d54d","METEOSAT pixel measurements reveal a striking new observation that rapid southward propagating deep clouds, on diurnal scale, are embedded in the northward migrating cloud structures from near equator upto 20N during active phases of 1999 summer monsoon. For the first time, we show that, ""while the deep convection is on"" during the active phase, an abrupt atmospheric drying occurs three days before the commencement of break in layers between 600 and 200 hPa over Continental Tropical Convergence Zone (CTCZ) with drastic reduction in Upper Tropospheric relative Humidity to ∼30%. East-West circulation cells induce subsidence over CTCZ and hence upper tropospheric drying. Continued drying and simultaneous weakening of low level convergence by ∼50% causes the transition to break. Subsidence associated with intense convection near foot hills of Himalayas weakens low level convergence. A rapid shift occurs in divergence field during transition with convergence replacing intense divergence at upper levels over CTCZ. Copyright 2004 by the American Geophysical Union."
"6701413579;7103060756;7004299063;56744278700;35514163500;","Arctic oscillation response to the 1991 Pinatubo eruption in the SKYHI general circulation model with a realistic quasi-biennial oscillation",2004,"10.1029/2003jd003699","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642538447&doi=10.1029%2f2003jd003699&partnerID=40&md5=be0d555d5eed44f63bb9572ebc5b675f","Stratospheric aerosol clouds from large tropical volcanic eruptions can be expected to alter the atmospheric radiative balance for a period of up to several years. Observations following several previous major eruptions suggest that one effect of the radiative perturbations is to cause anomalies in the Northern Hemisphere extratropical winter tropospheric circulation that can be broadly characterized as positive excursions of the Arctic Oscillation (AO). We report on a modeling investigation of the radiative and dynamical mechanisms that may account for the observed AO anomalies following eruptions. We focus on the best observed and strongest 20th century eruption, that of Mt. Pinatubo on 15 June 1991. The impact of the Pinatubo eruption on the climate has been the focus of a number of earlier modeling studies, but all of these previous studies used models with no quasi-biennial oscillation (QBO) in the tropical stratosphere. The QBO is a very prominent feature of interannual variability of tropical stratospheric circulation and could have a profound effect on the global atmospheric response to volcanic radiative forcing. Thus a complete study of the atmospheric variability following volcanic eruptions should include a realistic representation of the tropical QBO. Here we address, for the first time, this important issue. We employed a version of the SKYHI troposphere-stratosphere-mesosphere model that effectively assimilates observed zonal mean winds in the tropical stratosphere to simulate a very realistic QBO. We performed an ensemble of 24 simulations for the period 1 June 1991 to 31 May 1993. These simulations included a realistic prescription of the stratospheric aerosol layer based on satellite observations. These integrations are compared to control integrations with no volcanic aerosol. The model produced a reasonably realistic representation of the positive AO response in boreal winter that is usually observed after major eruptions. Detailed analysis shows that the aerosol perturbations to the tropospheric winter circulation are affected significantly by the phase of the QBO, with a westerly QBO phase in the lower stratosphere resulting in an enhancement of the aerosol effect on the AO. Improved quantification of the QBO effect on climate sensitivity helps to better understand mechanisms of the stratospheric contribution to natural and externally forced climate variability. Copyright 2004 by the American Geophysical Union."
"6603358668;6508009865;6506484654;6603823606;7005677213;7102237329;","Spatial and temporal variability of meteorological variables at Haut Glacier d'Arolla (Switzerland) during the ablation season 2001: Measurements and simulations",2004,"10.1029/2003jd003973","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642578307&doi=10.1029%2f2003jd003973&partnerID=40&md5=0cba67ecc422b5eeb5ccbb9fa369958e","During the ablation period 2001 a glaciometeorological experiment was carried out on Haut Glacier d'Arolla, Switzerland. Five meteorological stations were installed on the glacier, and one permanent automatic weather station in the glacier foreland. The altitudes of the stations ranged between 2500 and 3000 m a.s.l., and they were in operation from end of May to beginning of September 2001. The spatial arrangement of the stations and temporal duration of the measurements generated a unique data set enabling the analysis of the spatial and temporal variability of the meteorological variables across an alpine glacier. All measurements were taken at a nominal height of 2 m, and hourly averages were derived for the analysis. The wind regime was dominated by the glacier wind (mean value 2.8 ms-1) but due to erosion by the synoptic gradient wind, occasionally the wind would blow up the valley. A slight decrease in mean 2 m air temperatures with altitude was found, however the 2 m air temperature gradient varied greatly and frequently changed its sign. Mean relative humidity was 71% and exhibited limited spatial variation. Mean incoming shortwave radiation and albedo both generally increased with elevation. The different components of shortwave radiation are quantified with a parameterization scheme. Resulting spatial variations are mainly due to horizon obstruction and reflections from surrounding slopes, i.e., topography. The effect of clouds accounts for a loss of 30% of the extraterrestrial flux. Albedos derived from a Landsat TM image of 30 July show remarkably constant values, in the range 0.49 to 0.50, across snow covered parts of the glacier, while albedo is highly spatially variable below the zone of continuous snow cover. These results are verified with ground measurements and compared with parameterized albedo. Mean longwave radiative fluxes decreased with elevation due to lower air temperatures and the effect of upper hemisphere slopes. It is shown through parameterization that this effect would even be more pronounced without the effect of clouds. Results are discussed with respect to a similar study which has been carried out on Pasterze Glacier (Austria). The presented algorithms for interpolating, parameterizing and simulating variables and parameters in alpine regions are integrated in the software package AMUNDSEN which is freely available to be adapted and further developed by the community. Copyright 2004 by the American Geophysical Union."
"7501757094;57198472289;36950518200;7501956187;7402359452;36889357300;","Characteristics of cloud radiation forcing over East China",2004,"10.1175/1520-0442(2004)017<0845:COCRFO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842585782&doi=10.1175%2f1520-0442%282004%29017%3c0845%3aCOCRFO%3e2.0.CO%3b2&partnerID=40&md5=34750d354faf9fdba68f6d506f6b9488","Observations indicate that the East Asian summer monsoon (EASM) exhibits distinctive characteristics of large cloud amounts with associated heavy and persistent rainfall, although short breaks for clear sky usually occur. Consequently, the effects of cloud-radiation interactions can play an important role in the general circulation of the atmosphere and, thus, the evolution of the EASM. In this note, as a first step toward studying the topic, the 5-yr (January 1985-December 1989) Earth Radiation Budget Experiment (ERBE) dataset is used to show the spatial and temporal patterns of both shortwave (SW) and longwave (LW) cloud radiative forcing (CRF) at the top of the atmosphere over east China, and to compare the observed features with Atmospheric Model Intercomparison Project-II (AMIP-II) simulations with the University at Albany. State University of New York (SUNYA) Community Climate Model 3 (CCM3) and the ECHAM4 general circulation models. The observations indicate that the net CRF provides a cooling effect to the atmosphere-surface climate system, dominated by the SW CRF cooling (albedo effect) with partial compensation from the LW CRF warming (greenhouse effect). The SW CRF shows a strong seasonal cycle, and its peak magnitude is particularly large, ∼110 W m-2, for south China and the Yangtze-Huai River valley (YHRV) during May and June, while the LW CRF is about 50 W m-2 for the same months with a weak dependence on the latitudes and seasons. These characteristics are in sharp contrast to the Northern Hemispheric zonal means of the same latitude bands and seasons, thus implying a unique role for cloud-radiation interaction in east China. Both model simulations show similar observed characteristics, although biases exist. For example, in May, the ECHAM4 underestimates the SW CRF while the SUNYA CCM3 simulates a significantly larger value, both attributed to the respective biases in the simulated total cloud cover. Model-to-observation comparisons of the association between total cloud cover and SW CRF, and between high cloud cover and LW CRF, are also presented and their differences are discussed. Finally, the SUNYA CCM3 biases in the CRF and its relevance to the model cloud biases are discussed in the context of model cold and dry biases in climate simulations. © 2004 American Meteorological Society."
"7005397699;7102142308;7102964430;6603613527;6701489606;8772820800;8772820900;7003804398;7007006198;12645664000;7004371983;7402025405;8387475700;8772821600;6506796470;21733785800;7202111979;26433470700;7102707599;7404441387;6506253868;15832899700;55710583000;7005165467;","Remote sensing of vegetation and land-cover change in Arctic Tundra Ecosystems",2004,"10.1016/j.rse.2003.10.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10744226306&doi=10.1016%2fj.rse.2003.10.018&partnerID=40&md5=e21aacfb01e15b6fa47e0aed1bc76392","The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations. The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored. © 2003 Elsevier Inc. All rights reserved."
"57202891769;","The impact of cloud feedbacks on Arctic climate under Greenhouse forcing",2004,"10.1175/1520-0442(2004)017<0603:TIOCFO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642339807&doi=10.1175%2f1520-0442%282004%29017%3c0603%3aTIOCFO%3e2.0.CO%3b2&partnerID=40&md5=1faa3f8fb56b4724e181525890b64042","The simulation of Arctic cloud cover and the sensitivity of Arctic climate to cloud changes are investigated using an atmosphere-mixed-layer ocean GCM (GENESIS2). The model is run with and without changes in three-dimensional cloud fraction under 2 × CO2, radiative forcing. This model was chosen in part because of its relatively successful representation of modern Arctic cloud cover, a trait attributable to the parameterized treatment of mixed-phase microphysics. Simulated modern Arctic cloud fraction is insensitive to model biases in surface boundary conditions (SSTs and sea ice distribution), but the modeled Arctic climate is sensitive to high-frequency cloud variability. When forced with increased CO2, the model generally simulates more (less) vertically integrated cloudiness in high (low) latitudes. In the simulation without cloud feedbacks, cloud fraction is fixed at its modern control value at all grid points and all levels while CO2, is doubled. Compared with this fixed-cloud experiment, the simulated cloud changes enhance greenhouse warming at all latitudes, accounting for one-third of the global warming signal. This positive feedback is most pronounced in the Arctic, where approximately 40% of the warming is due to cloud changes. The strong cloud feedback in the Arctic is caused not only by local processes but also by cloud changes in lower latitudes, where positive top-of-the-atmosphere cloud radiative forcing anomalies are larger. The extra radiative energy gained in lower latitudes is transported dynamically to the Arctic via moist static energy flux convergence. The results presented here demonstrate the importance of remote impacts from low and midlatitudes for Arctic climate change. © 2004 American Meteorological Society."
"24066600500;55410029500;6508074492;7004115849;","Evidence for a link between the flux of galactic cosmic rays and Earth's climate during the past 200,000 years",2004,"10.1016/j.jastp.2003.12.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1542290640&doi=10.1016%2fj.jastp.2003.12.004&partnerID=40&md5=51a5a487c77fad463ae3e1db98d66a7d","The possibility that galactic cosmic rays (GCR) influence the Earth's cloud cover and therefore have an important impact on the Earth's radiative climate forcing has become a leading candidate to explain the observed sun-climate connection. A correlation between GCR and low cloud cover has been ascertained in models and observations over the past few years. The deposition of cosmogenic radionuclides in ice cores and deep sea sediments can be used as a proxy for the past GCR-flux and provides an important tool to study the supposed GCR-climate connection on glacial-interglacial timescales. In this study, a record of geomagnetic paleointensity based on 10Be from deep sea sediments is used as proxy for GCR-flux over the past 200,000 years. It is compared with climate records from marine, terrestrial and ice core archives. Our results are consistent with the GCR-climate theory and suggest the existence of a GCR-climate connection over the past 200,000 years. © 2004 Elsevier Ltd. All rights reserved."
"55703823500;7601492669;57202301596;","Effects of the Andes on Eastern Pacific climate: A regional atmospheric model study",2004,"10.1175/1520-0442(2004)017<0589:EOTAOE>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642383787&doi=10.1175%2f1520-0442%282004%29017%3c0589%3aEOTAOE%3e2.0.CO%3b2&partnerID=40&md5=5c127dddbf86a6d113dd40634b4d3b1c","A regional atmospheric model is used to study the effects of the narrow and steep Andes on the eastern Pacific climate. In the Southern Hemisphere cold season (i.e., August-October 1999), the model reproduces key climatic features, including the intertropical convergence zone (ITCZ) north of the equator and an extensive low-level cloud deck capped by a temperature inversion to the south. Blocking the warm easterly winds from South America, the Andes help maintain the divergence and temperature inversion and, hence, the stratocumulus cloud deck over the southeast Pacific off South America. In an experiment where the Andean mountains are removed, the warm advection from the South American continent lowers the inversion height and reduces the low-level divergence offshore, leading to a significant reduction in cloud amount and an increase in solar radiation that reaches the sea surface. In March and early April 1999, the model simulates a double ITCZ in response to the seasonal warming on and south of the equator, in agreement with satellite observations. Under the same sea surface temperature forcing, the removal of the Andes prolongs the existence of the southern ITCZ for 3 weeks. Without the mountains, the intrusion of the easterlies from South America enhances the convergence in the lower atmosphere, and the transient disturbances travel freely westward from the continent. Both effects of the Andes removal favor deep convection south of the equator. The same sensitivity experiments are repeated with orography used in T42 global models. and the results confirm that an underrepresentation of the Andes reduces the stratus clouds in the cold season and prolongs the southern ITCZ in the warm season, with both acting to weaken the latitudinal asymmetry of eastern Pacific climate. The implications of these results for coupled modeling of climatic asymmetry are discussed. © 2004 American Meteorological Society."
"6504033814;7006246996;7102577095;","Infrared radiative properties of the Antarctic plateau from AVHRR data. Part I: Effect of the snow surface",2004,"10.1175/1520-0450(2004)043<0350:IRPOTA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842865107&doi=10.1175%2f1520-0450%282004%29043%3c0350%3aIRPOTA%3e2.0.CO%3b2&partnerID=40&md5=c20f3f9ba6576594ce003ce03de439fa","The effective scene temperature, or ""brightness temperature,"" measured in channel 3 (3.5-3.9 μm) of the Advanced Very High Resolution Radiometer (AVHRR) is shown to be sensitive, in principle, to the effective particle size of snow grains on the Antarctic plateau, over the range of snow grain sizes reported in field studies. In conjunction with a discrete ordinate method radiative transfer model that couples the polar atmosphere with a scattering and absorbing snowpack, the thermal infrared channels of the AVHRR instrument can, therefore, be used to estimate effective grain size at the snow surface over Antarctica. This is subject to uncertainties related to the modeled top-of-atmosphere bidirectional reflectance distribution function resulting from the possible presence of sastrugi and to lack of complete knowledge of snow crystal shapes and habits as they influence the scattering phase function. However, when applied to NOAA-11 and NOAA-12 AVHRR data from 1992, the snow grain effective radii of order 50 μm are retrieved, consistent with field observations, with no apparent discontinuity between two spacecraft having different viewing geometries. Retrieved snow grain effective radii are 10-20-μm larger when the snow grains are modeled as hexagonal solid columns rather than as spheres with a Henyey-Greenstein phase function. Despite the above-mentioned uncertainties, the retrievals are consistent enough that one should be able to monitor climatically significant changes in surface snow grain size due to major precipitation events. It is also shown that a realistic representation of the surface snow grain size is critical when retrieving the optical depth and effective particle radius of clouds for the optically thin clouds most frequently encountered over the Antarctic plateau. © 2004 American Meteorological Society."
"7102057095;55001699000;7004600486;7202389214;6701830105;6603793985;57198249844;","Lidar observations of polar mesospheric clouds at Rothera, Antarctica (67.5°S, 68.0°W)",2004,"10.1029/2003GL018638","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18144433605&doi=10.1029%2f2003GL018638&partnerID=40&md5=b721e71d97427c4bb3270b3e8d158ad6","Polar mesospheric clouds (PMC) were observed by an Fe Boltzmann temperature lidar at Rothera (67.5°S, 68.0°W), Antarctica in the austral summer of 2002-2003. The Rothera PMC are much weaker, less frequent, and not as high as the PMC observed at the South Pole. The mean PMC altitude is 83.74 ± 0.25 km, which is approximately 1.3 km lower than the South Pole clouds. A comparison of numerous cloud observations indicates that southern hemisphere PMC are about 1 km higher than northern clouds at similar latitudes. Lidar measurements also show that the mesopause region temperatures at Rothera in late January are warmer than at the South Pole, while the Fe layer at Rothera has higher density and a lower peak altitude compared to the summertime Fe layer at the South Pole. These Fe density and temperature observations are qualitatively consistent with the PMC observations. Copyright 2004 by the American Geophysical Union."
"7004308563;6603606008;","Causes and consequences of extreme Permo-Triassic warming to globally equable climate and relation to the Permo-Triassic extinction and recovery",2004,"10.1016/S0031-0182(03)00667-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1242322144&doi=10.1016%2fS0031-0182%2803%2900667-9&partnerID=40&md5=78f3ec7a2523539ee41f53b8f5026c0f","Permian waning of the low-latitude Alleghenian/Variscan/Hercynian orogenesis led to a long collisional orogeny gap that cut down the availability of chemically weatherable fresh silicate rock resulting in a high-CO 2 atmosphere and global warming. The correspondingly reduced delivery of nutrients to the biosphere caused further increases in CO 2 and warming. Melting of polar ice curtailed sinking of O 2- and nutrient-rich cold brines while pole-to-equator thermal gradients weakened. Wind shear and associated wind-driven upwelling lessened, further diminishing productivity and carbon burial. As the Earth warmed, dry climates expanded to mid-latitudes, causing latitudinal expansion of the Ferrel circulation cell at the expense of the polar cell. Increased coastal evaporation generated O2- and nutrient-deficient warm saline bottom water (WSBW) and delivered it to a weakly circulating deep ocean. Warm, deep currents delivered ever more heat to high latitudes until polar sinking of cold water was replaced by upwelling WSBW. With the loss of polar sinking, the ocean was rapidly filled with WSBW that became increasingly anoxic and finally euxinic by the end of the Permian. Rapid incursion of WSBW could have produced ∼20 m of thermal expansion of the oceans, generating the well-documented marine transgression that flooded embayments in dry, hot Pangaean mid-latitudes. The flooding further increased WSBW production and anoxia, and brought that anoxic water onto the shelves. Release of CO2 from the Siberian traps and methane from clathrates below the warming ocean bottom sharply enhanced the already strong greenhouse. Increasingly frequent and powerful cyclonic storms mined upwelling high-latitude heat and released it to the atmosphere. That heat, trapped by overlying clouds of its own making, suggests complete breakdown of the dry polar cell. Resulting rapid and intense polar warming caused or contributed to extinction of the remaining latest Permian coal forests that could not migrate any farther poleward because of light limitations. Loss of water stored by the forests led to aquifer drainage, adding another ∼5 m to the transgression. Non-peat-forming vegetation survived at the newly moist poles. Climate feedback from the coal-forest extinction further intensified warmth, contributing to delayed biotic recovery that generally did not begin until mid-Triassic, but appears to have resumed first at high latitudes late in the Early Triassic. Current quantitative models fail to generate high-latitude warmth and so do not produce the chain of events we outline in this paper. Future quantitative modeling addressing factors such as polar cloudiness, increased poleward heat transport by deep water and its upwelling by cyclonic storms, and sustainable mid-latitude sinking of warm brines to promote anoxia, warming, and thermal expansion of deep water may more closely simulate conditions indicated by geological and paleontological data. © 2003 Elsevier B.V. All rights reserved."
"7102268722;7005070958;","Testing the impact of clouds on the radiation budgets of 19 atmospheric general circulation models",2004,"10.1029/2003jd004018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642558935&doi=10.1029%2f2003jd004018&partnerID=40&md5=0cc9530d635e35473e8eb74984d11cf7","We compare cloud-radiative forcing (CRF) at the top-of-the atmosphere from 19 atmospheric general circulation models, employing simulations with prescribed seasurface temperatures, to observations from the Earth Radiation Budget Experiment (ERBE). With respect to 60°N to 60°S means, a surprising result is that many of the 19 models produce unusually large biases in Net CRF that are all of the same sign (negative), meaning that many of the models significantly overestimate cloud radiative cooling. The primary focus of this study, however, is to demonstrate a diagnostic procedure, using ERBE data, to test if a model might produce, for a given region, reasonable CRF as a consequence of compensating errors caused either by unrealistic cloud vertical structure, cloud optical depth or cloud fraction. For this purpose we have chosen two regions, one in the western tropical Pacific characterized by high clouds spanning the range from thin cirrus to deep convective clouds, and the other in the southeastern Pacific characterized by trade cumulus. For a subset of eight models, it is found that most typically produce more realistic regionally-averaged CRF (and its longwave and shortwave components) for the southeastern region as opposed to the western region. However, when the diagnostic procedure for investigating cloud vertical structure and cloud optical depth is imposed, this somewhat better agreement in the southeastern region is found to be the result of compensating errors in either cloud vertical structure, cloud optical depth or cloud fraction. The comparison with ERBE data also shows large errors in clear-sky fluxes for many of the models. Copyright 2004 by the American Geophysical Union."
"23485990000;7101978698;","Middle-atmospheric response to a future increase in humidity arising from increased methane abundance",2004,"10.1029/2003jd003590","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642514146&doi=10.1029%2f2003jd003590&partnerID=40&md5=800de456e976c1f90b1cf10438527df4","The response of the middle atmosphere to an increase in humidity arising from a possible future increase in CH4 is examined in a general circulation model with interactive H2O and O3. A chemical parameterization allows the middle-atmospheric H2O change to evolve naturally from an imposed change in tropospheric CH4. First, a simulation of the year 2060 using postulated loadings of the radiatively active gases is compared with a control simulation of the present-day atmosphere. Then, the particular contribution of the CH4 (and hence H2O) change to the observed difference is isolated by repeating the 2060 simulation without the projected CH4 change. Under the Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (SRES) B2 scenario, the middle atmosphere in 2060 cools by up to ∼5 K relative to 1995, with the CH4-derived increase in H2O accounting for ∼10% of the change. The cooling is accompanied by a strengthened general circulation, intensified dynamic heating rates, and a reduction in the mean age of middle-atmospheric air. The component of the circulation change attributable solely to the H2O change differs somewhat from the net response: The H2O change causes a greater increase in the descent rate in the north than in the south, ages the stratospheric air, and has a distinct effect on age/N2O correlations. Around 20% of the increased prevalence of polar stratospheric clouds (PSCs) in 2060 is due to the microphysical effect of the extra H2O, with the remainder attributable to the reduced vortex temperatures. Although the PSC increase facilitates release of reactive chlorine, this positive impact on chemical O3 destruction is outweighed by the negative impact of the reduced total chlorine in 2060. Nonetheless, the H2O increase does make the 2060 Arctic O3 loss ∼15% greater than it would otherwise be. Copyright 2004 by the American Geophysical Union."
"57209089997;35453054300;7102320462;7403247998;","Likelihood of rapidly increasing surface temperatures unaccompanied by strong warming in the free troposphere",2004,"10.3354/cr025185","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1542347549&doi=10.3354%2fcr025185&partnerID=40&md5=da16e0d188abccbe2e64800f6e0b7efd","Recent model simulations of the effects of increasing greenhouse gases combined with other anthropogenic effects predicted larger rates of warming in the mid and upper troposphere than near the Earth's surface. In multiple model comparisons we find that accelerated upper-level warming is simulated in all models for the greenhouse-gas/direct-aerosol forcing representative of 1979-2000. However, in a test of model predictive skill, a comparison with observations shows no warming of the free troposphere over this period. We assessed the likelihood that such a disparity between model projection and observations could be generated by forcing uncertainties or chance model fluctuations, by comparing all possible 22 yr temperature trends in a series of climate simulations. We find that it is extremely unlikely for near-surface air temperatures (surface temperatures) to increase at the magnitude observed since 1979 without a larger warming in the mid-troposphere. Warming of the surface relative to the mid-troposphere was also more likely in control simulations than under anthropogenic forcing. Because errors in the vertical temperature structure would be expected to create errors in water-vapor feedback, cloud cover and moisture content, these results suggest the need for great caution when applying the simulations to future climate predictions and to impact assessments. © Inter-Research 2004."
"6602787883;7004544454;57203054708;","Impact of orographically induced spatial variability in PBL stratiform clouds on climate simulations",2004,"10.1175/1520-0442(2004)017<0276:IOOISV>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342288754&doi=10.1175%2f1520-0442%282004%29017%3c0276%3aIOOISV%3e2.0.CO%3b2&partnerID=40&md5=14fd3c1c83f88063dd5bda5fa41b6be1","This paper examines the impact of orographically induced mesoscale heterogeneities on the macroscopic behavior of planetary boundary layer (PBL) stratiform clouds, and implements and tests a physically based parameterization of this effect in the University of California, Los Angeles (UCLA), atmospheric general circulation model (AGCM). The orographic variance and associated thermal circulations induce inhomogeneities in the cloud field that can significantly alter the PBL evolution; an effect that has been largely ignored in existing climate models. The impact of this effect on AGCM simulations is examined and the mechanisms at work are studied by analyzing a series of Cloud System Resolving Model (CSRM) simulations. Both the CSRM and AGCM results show that, in the absence of the orographic effect, the continental PBL tends to be in one of two regimes: the solid regime characterized by a cold and overcast PBL and the broken regime characterized by a low time-mean cloud incidence and a large-amplitude diurnal cycle. Without the orographic effect, the PBL may lock in the convectively stable solid regime, with deep convection displaced to the surrounding oceans and subsidence induced over land further contributing to the persistence of the cloud deck. The inclusion of the orographic effect weakens the feedback between the cloud's albedo and the ground temperature responsible for the existence of the two regimes and, therefore, conspires against the persistence of the solid regime rendering the behavior of the PBL-ground system less bimodal. The parameterization featured in this paper also increases the amplitude of the diurnal cycle in the AGCM and reduces the excessive seasonality in PBL cloud incidence, resulting in an improved simulation of convective precipitation over regions where the solid regime was spuriously dominating. © 2004 American Meteorological Society."
"7201637089;7202948585;7401491382;","Transmission of solar radiation by clouds over snow and ice surfaces: A parameterization in terms of optical depth, solar zenith angle, and surface albedo",2004,"10.1175/1520-0442(2004)017<0266:TOSRBC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342310451&doi=10.1175%2f1520-0442%282004%29017%3c0266%3aTOSRBC%3e2.0.CO%3b2&partnerID=40&md5=5ea7cb80cd95b795f9b71900452e918c","A multilevel spectral radiative transfer model is used to develop simple but accurate parameterizations for cloud transmittance as a function of cloud optical depth, solar zenith angle, and surface albedo, for use over snow, ice, and water surfaces. The same functional form is used for broadband and spectral transmittances, but with different coefficients for each spectral interval. When the parameterization is applied to measurements of ""raw"" cloud transmittance (the ratio of downward irradiance under cloud to downward irradiance measured under clear sky at the same zenith angle), an ""effective"" optical depth τ is inferred for the cloud field, which may be inhomogeneous and even patchy. This effective optical depth is only a convenient intermediate quantity, not an end in itself. It can then be used to compute what the transmittance of this same cloud field would be under different conditions of solar illumination and surface abedo, to obtain diurnal and seasonal cycles of cloud radiative forcing. The parameterization faithfully mimics the radiative transfer model, with rms errors of 1%-2%. Lack of knowledge of cloud droplet sizes causes little error in the inference of cloud radiative properties. The parameterization is applied to pyranometer measurements from a ship in the Antarctic sea ice zone; the largest source of error in inference of inherent cloud properties is uncertainty in surface albedo. © 2004 American Meteorological Society."
"7005955015;24080547200;6602142887;","Solar activity, cosmic rays, clouds and climate - An update",2004,"10.1016/j.asr.2003.02.040","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042590646&doi=10.1016%2fj.asr.2003.02.040&partnerID=40&md5=abcd4b4ba405f9c5052de1f43a841465","Eighteen years of monthly averaged low cloud cover data from the International Satellite Cloud Climatology Project are correlated with both total solar irradiance and galactic cosmic ray flux from neutron monitors. When globally averaged low cloud cover is considered, consistently higher correlations (but with opposite sign) are found between low cloud variations and solar irradiance variations than between variations in cosmic ray flux and low cloud cover. The correlations are not significant at the 0.1 level, but it should be noted that non-solar effects such as El Niño and volcanic eruptions have not been removed. When spatial regression patterns between low cloud cover and total solar irradiance are studied, the Pacific Ocean exhibits patterns reminiscent of the Pacific Decadal Oscillation. A possible interpretation is that the solar signal interacts with variability modes in the ocean to give this kind of pattern. Correlating low cloud cover with its own global average shows that most of the variability is coming from the subtropical oceans, where the bulk of the Earth's low clouds are found. In conclusion, the updated analysis is not inconsistent with a modulation of marine low cloud cover due to variations in solar irradiance causing changes in lower tropospheric static stability, but many details are still missing. A cosmic ray modulation seems less likely, but can not be ruled out on the basis of the present analysis. © 2004 COSPAR. Published by Elsevier Ltd. All rights reserved."
"7404183672;6602080205;","Climate response to tropospheric absorbing aerosols in an intermediate general-circulation model",2004,"10.1256/qj.03.64","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0442280914&doi=10.1256%2fqj.03.64&partnerID=40&md5=cda2d7266de304e5983eed326ad5e827","This study uses idealized aerosol distributions with the Reading Intermediate General-Circulation Model (IGCM) to assess and explain the climate response in that model to absorbing tropospheric aerosol. We find that the sign of the direct aerosol radiative forcing is not a good indication of the sign of the resulting global and annual mean surface temperature change. The climate sensitivity parameter for aerosols which absorb some solar radiation is much larger than that for CO2 or solar experiments with the same model. Reasons for the enhanced surface temperature response in the presence of aerosol are examined. Significant changes in cloud amount occur, some of which appear most influenced by the change in surface temperature and may be generic to any mechanism that warms the surface. A reduction in low cloud amount occurs when the aerosol single-scattering albedo is less than 0.95; the so-called 'semi-direct' effect of aerosols is clearly evident in this model. We suggest that this aerosol-cloud feedback is present in all GCMs which include absorbing tropospheric aerosol but remains largely undiagnosed. Comparisons with a previous study and further sensitivity tests suggest that the magnitude of this effect and the mechanisms behind it are strongly dependent on the cloud scheme employed."
"8670472000;6602178158;6602547442;6603341831;","The Rossby Centre regional atmospheric climate model part II: Application to the Arctic climate",2004,"10.1579/0044-7447-33.4.211","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042695256&doi=10.1579%2f0044-7447-33.4.211&partnerID=40&md5=793720c500e89506e7ce11a2050947bd","The Rossby Centre regional climate model (RCA2) has been integrated over the Arctic Ocean as part of the international ARCMIP project. Results have been compared to observations derived from the SHEBA data set. The standard RCA2 model overpredicts cloud cover and down-welling longwave radiation, during the Arctic winter. This error was improved by introducing a new cloud parameterization, which significantly improves the annual cycle of cloud cover. Compensating biases between clear sky downwelling longwave radiation and longwave radiation emitted from cloud base were identified. Modifications have been introduced to the model radiation scheme that more accurately treat solar radiation interaction with ice crystals. This leads to a more realistic representation of cloud-solar radiation interaction. The clear sky portion of the model radiation code transmits too much solar radiation through the atmosphere, producing a positive bias at the top of the frequent boundary layer clouds. A realistic treatment of the temporally evolving albedo, of both sea-ice and snow, appears crucial for an accurate simulation of the net surface energy budget. Likewise, inclusion of a prognostic snow-surface temperature seems necessary, to accurately simulate near-surface thermodynamic processes in the Arctic."
"8670472000;6603341831;6602547442;7006665163;","The Rossby Centre regional atmospheric climate model part I: Model climatology and performance for the present climate over Europe",2004,"10.1579/0044-7447-33.4.199","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042602670&doi=10.1579%2f0044-7447-33.4.199&partnerID=40&md5=d7af66bf3cbae91b290f3bbf195e6307","The Rossby Centre Atmospheric Regional Climate Model (RCA2) is described and simulation results, for the present climate over Europe, are evaluated against available observations. Systematic biases in the models mean climate and climate variability are documented and key parameterization weaknesses identified. The quality of near-surface parameters is investigated in some detail, particularly temperature, precipitation, the surface energy budget and cloud cover. The model simulates the recent, observed climate and variability with a high degree of realism. Compensating errors in the components of the surface radiation budget are highlighted and the fundamental causes of these biases are traced to the relevant aspects of the cloud, precipitation and radiation parameterizations. The model has a tendency to precipitate too frequently at small rates, this has a direct impact on the simulation of cloud-radiation interaction and surface temperatures. Great care must be taken in the use of observations to evaluate high resolution RCMs, when they are forced by analyzed boundary conditions. This is particularly true with respect to precipitation and cloudiness, where observational uncertainty is often larger than the RCM bias."
"35509639400;7004714030;56283400100;24322005900;7004764167;","On dynamic and thermodynamic components of cloud changes",2004,"10.1007/s00382-003-0369-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2142829554&doi=10.1007%2fs00382-003-0369-6&partnerID=40&md5=182fc9541143b753cda33fce1a45a768","Clouds are sensitive to changes in both the large-scale circulation and the thermodynamic structure of the atmosphere. In the tropics, temperature changes that occur on seasonal to decadal time scales are often associated with circulation changes. Therefore, it is difficult to determine the part of cloud variations that results from a change in the dynamics from the part that may result from the temperature change itself. This study proposes a simple framework to unravel the dynamic and non-dynamic (referred to as thermodynamic) components of the cloud response to climate variations. It is used to analyze the contrasted response, to a prescribed ocean warming, of the tropically-averaged cloud radiative forcing (CRF) simulated by the ECMWF, LMD and UKMO climate models. In each model, the dynamic component largely dominates the CRF response at the regional scale, but this is the thermodynamic component that explains most of the average CRF response to the imposed perturbation. It is shown that this component strongly depends on the behaviour of the low-level clouds that occur in regions of moderate subsidence (e.g. in the trade wind regions). These clouds exhibit a moderate sensitivity to temperature changes, but this is mostly their huge statistical weight that explains their large influence on the tropical radiation budget. Several propositions are made for assessing the sensitivity of clouds to changes in temperature and in large-scale motions using satellite observations and meteorological analyses on the one hand, and mesoscale models on the other hand. © Springer-Verlag 2004."
"55992263300;8732171100;7005539346;27267529400;55468534200;","A parametrization of solar energy disposition in the climate system",2004,"10.3137/ao.420203","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4344606263&doi=10.3137%2fao.420203&partnerID=40&md5=a89341d1490663d9192d21a4f40a90d4","During the past decade a class of climate models of reduced complexity, called Earth system Models of Intermediate Complexity (EMICs), has been developed. Some of these models employ an energy and moisture balance model (EMBM) as the atmospheric component. However, the solar energy disposition (SED) in the subcomponents of these climate models using an EMBM has never been parametrized in a systematic manner. In this paper, the SED, which is a measure of the amount of solar radiation absorbed in the atmosphere, absorbed at the surface and reflected to space, is first expressed as functions of the surface albedo and the integrated atmospheric reflectivity, transmissivity, absorptivity and cloud amount for a one-layer atmosphere which includes a cloud region and aerosols. Then an atmospheric radiative-convective model is used to parametrize the integrated atmospheric reflectivity and transmissivity in terms of cloud optical depth, aerosol optical depth, precipitable water, and solar zenith angle. Next, the presentday climatology of the SED is calculated using the climatological data (for cloud amount and optical depth, aerosol optical depth, precipitable water and surface albedo) from the International Satellite Cloud Climatology Project (ISCCP), ECMWF 15-year Reanalysis (ERA-15) and the Pathfinder Atmosphere (PATMOS). Since cloud amount data are used from three independent sources, three SEDs are in fact calculated and tested against the SED derived from satellite data. The calculated SEDs are in good agreement with the SED derived from satellite data; thus the parametrized SED presented here is recommended for use in climate models which employ an EMBM or a one-layer atmosphere model. © 2004 Taylor & Francis Group, LLC."
"6603025800;16637291100;6602926744;","A study of the Antarctic surface energy budget using a polar regional atmospheric model forced with satellite-derived cloud properties",2004,"10.1175/1520-0493(2004)132<0654:ASOTAS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1542645252&doi=10.1175%2f1520-0493%282004%29132%3c0654%3aASOTAS%3e2.0.CO%3b2&partnerID=40&md5=ae590b4832b4736a085fd6ae018e9a82","Cloud properties from the newly extended Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder (APP-x) dataset were incorporated into the atmospheric component of the Arctic Regional Climate System Model (ARCSyM) in order to improve the simulation of the Antarctic surface energy balance. A method for using the APP-x cloud properties in 48-h model simulations is presented. In the experiments, the model cloud fields were altered via the water vapor mixing ratio using cloud properties from the APP-x dataset. Significant improvements in monthly mean downwelling longwave radiation at the surface were observed relative to surface measurements. In the austral summer, the use of the APP-x dataset resulted in improvements as large as 30 W m-2 at the South Pole when computed to model results without APP-x clouds. However, only a very small improvement was seen in the turbulent heat fluxes and the surface temperature. It was also found that the satellite data can be used to shorten the model ""spinup"" time and may be useful in model initialization for short duration forecasts. © 2004 American Meteorological Society."
"7004593505;6603783890;35609878300;55206018900;55424975000;7005206400;7203054240;6506191803;7403635969;7102866124;6507871748;57201177267;","Amazonian climate: Results and future research",2004,"10.1007/s00704-004-0052-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642568263&doi=10.1007%2fs00704-004-0052-9&partnerID=40&md5=061196efc2bbdd8426425cdfd9e4e285","Some of the results from the climate component of the Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), which are presented in this Special Issue are summarised. Recent advances in Amazonian climate modelling are also discussed. There is a range of papers which fall into three groups: surface fluxes and boundary layer growth: convection, clouds and rainfall; and climate modelling. The new insight given by this work is discussed and an argument is made for future research to employ a wider approach to Amazonian climate modelling. © Springer-Verlag 2004."
"7003960899;","A comparison of AMIP II model cloud layer properties with ISCCP D2 estimates",2004,"10.1007/s00382-003-0374-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2142705296&doi=10.1007%2fs00382-003-0374-9&partnerID=40&md5=319bb0cd2d5898d58ca2b7599fda6b0e","The cloud amounts and liquid and ice water paths as a function of height in five Atmospheric Model Intercomparison Project (AMIP) II models have been compared to International Satellite Cloud Climatology Project (ISCCP) d2 observations. The model layer data have been transformed to the ISCCP low, mid and height cloud amount and vertically integrated water values. In addition a simple radiative transfer model has been used to transform both model output and ISCCP cloud amount and water contents into top of atmosphere albedos for the low, mid and high cloud fractions. Overall, most models represent moderately well the spatial, seasonal and interannual variability of total cloud albedo, which is largely a function of the total cloud amount. The models also tend to predict moderately well the spatial, seasonal, and interannual variability of cloud fraction, but fail to display the observed spatial, and especially, seasonal and interannual variability in cloud water path. In particular nearly all models have mid and low cloud water path variabilities, which are much larger than those observed in the ISCCP observations. This increased cloud water path variability seems to compensate partially for smaller underestimates of cloud fraction variability in most models. Furthermore, variations in cloud amount and cloud water path are much more often negatively correlated in models than in the observations. A simple estimate of the influence of cloud overlap suggests that monthly mean model cloud layers are less stacked in the vertical in models than in an observational estimate based upon a combination of satellite and ground-based observations. © Springer-Verlag 2004."
"7410041005;7005171879;35419152500;6701648855;","Studying altocumulus with ice virga using ground-based active and passive remote sensors",2004,"10.1175/1520-0450(2004)043<0449:SAWIVU>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842635759&doi=10.1175%2f1520-0450%282004%29043%3c0449%3aSAWIVU%3e2.0.CO%3b2&partnerID=40&md5=652ec7426006f945ba8822c53ac7ff13","Mixed-phase clouds are still poorly understood, though studies have indicated that their parameterization in general circulation models is critical for climate studies. Most of the knowledge of mixed-phase clouds has been gained from in situ measurements, but reliable remote sensing algorithms to study mixed-phase clouds extensively are lacking. A combined active and passive remote sensing approach for studying supercooled altocumulus with ice virga, using multiple remote sensor observations, is presented. Precipitating altocumulus clouds are a common type of mixed-phase clouds, and their easily identifiable structure provides a simple scenario to study mixed-phase clouds. First, ice virga is treated as an independent ice cloud, and an existing lidar-radar algorithm to retrieve ice water content and general effective size profiles is applied. Then, a new iterative approach is used to retrieve supercooled water cloud properties by minimizing the difference between atmospheric emitted radiance interferometer (AERI)-observed radiances and radiances, calculated using the discrete-ordinate radiative transfer model at 12 selected wavelengths. Case studies demonstrate the capabilities of this approach in retrieving radiatively important microphysical properties to characterize this type of mixed-phase cloud. The good agreement between visible optical depths derived from lidar measurement and those estimated from retrieved liquid water path and effective radius provides a closure test for the accuracy of mainly AERI-based supercooled water cloud retrieval. © 2004 American Meteorological Society."
"7601492669;57202301596;55703823500;56962915800;","Regional model simulations of marine boundary layer clouds over the southeast Pacific off South America. Part I: Control experiment",2004,"10.1175/1520-0493(2004)132<0274:RMSOMB>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642381321&doi=10.1175%2f1520-0493%282004%29132%3c0274%3aRMSOMB%3e2.0.CO%3b2&partnerID=40&md5=f5e9ab9362385c3983a72da757177316","A regional climate model is used to simulate boundary layer stratocumulus (Sc) clouds over the southeast Pacific off South America during August-October 1999 and to study their dynamical, radiative, and microphysical properties and their interaction with large-scale dynamic fields. Part I evaluates the model performance against satellite observations and examines physical processes important for maintaining the temperature inversion and Sc clouds in the simulation. The model captures major features of the marine boundary layer in the region, including a well-mixed marine boundary layer, a capping temperature inversion, Sc clouds, and the diurnal cycle. The Sc clouds develop in the lower half of and below the temperature inversion layer that increases its height westward off the Pacific coast of South America. The strength of the capping inversion is determined not only by large-scale subsidence and local sea surface temperature (SST), but also by cloud-radiation feedback. A heat budget analysis indicates that upward longwave radiation strongly cools the upper part of the cloud layer and strengthens the temperature inversion. This cloud-top cooling further induces a local enhancement of subsidence in and below the inversion layer, resulting in a dynamical warming that strengthens the temperature stratification above the clouds. While of secondary importance on the mean, solar radiation drives a pronounced diurnal cycle in the model boundary layer. Consistent with observations, boundary layer clouds thicken after sunset and cloud liquid water content reaches a maximum at 0600 local time just before the sunrise. © 2004 American Meteorological Society."
"6603631763;7201607592;6603025800;","Relative merits of the 1.6 and 3.75 μm channels of the AVHRR/3 for cloud detection",2004,"10.5589/m03-058","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2542482756&doi=10.5589%2fm03-058&partnerID=40&md5=44bf1dd46e888c6a1748e6b97088a6c5","A study was performed to investigate the potential impacts of the cloud-masking capability of the advanced very high resolution radiometer (AVHRR) on board the National Oceanic and Atmospheric Administration (NOAA) polar orbiting satellites because of the addition of the 1.6 µm channel (ch3a) and the removal of the 3.75 µm channel (ch3b) during daylight operation. Both channels are measured by the AVHRR, but only one is available in the data stream. Because the AVHRR presents the longest time series of global imager data, this change could impact a critical source of climate data. Specifically, changes in its cloud-masking capability may introduce a discontinuity in its derived clear-sky data records. To study the relative cloud-detection capabilities of the AVHRR with ch3a or ch3b, data from the moderate resolution imaging spectroradiometer (MODIS) on the National Aeronautics and Space Administration (NASA) TERRA mission was used because it offers ch3a, ch3b, and the other AVHRR channels simultaneously. The MODIS data analysis indicated that ch3b offered more capability in separating cloud from snow. Cloud-masking results with ch3a and ch3b were comparable with respect to the separation of cloud from aerosol and the detection of cloud over a desert scene. Although these results are preliminary and based on a limited analysis, they do indicate that the switch from ch3b to ch3a may have significant impacts on the cloud-detection capability of the AVHRR. © 2004, Taylor & Francis Group, LLC. All rights reserved."
"35461255500;6603611312;7007039218;57207261095;8758100000;6602906612;7004858482;7004296083;6603860503;7003750797;7007162501;7102357095;7005755464;7102513363;","A new feedback mechanism linking forests, aerosols, and climate",2004,"10.5194/acp-4-557-2004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242695341&doi=10.5194%2facp-4-557-2004&partnerID=40&md5=bea39c98a7ad75cab24f886b718bb488","The possible connections between the carbon balance of ecosystems and aerosol-cloud-climate interactions play a significant role in climate change studies. Carbon dioxide is a greenhouse gas, whereas the net effect of atmospheric aerosols is to cool the climate. Here, we investigated the connection between forest-atmosphere carbon exchange and aerosol dynamics in the continental boundary layer by means of multiannual data sets of particle formation and growth rates, of CO2 fluxes, and of monoterpene concentrations in a Scots pine forest in southern Finland. We suggest a new, interesting link and a potentially important feedback among forest ecosystem functioning, aerosols, and climate: Considering that globally increasing temperatures and CO2 fertilization are likely to lead to increased photosynthesis and forest growth, an increase in forest biomass would increase emissions of non-methane biogenic volatile organic compounds and thereby enhance organic aerosol production. This feedback mechanism couples the climate effect Of CO2 with that of aerosols in a novel way. © European Geosciences Union 2004."
"55462907200;7402807578;7403948631;","Prediction of the vertical profile of ozone based on ground-level ozone observations and cloud cover",2004,"10.1080/10473289.2004.10470914","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842853144&doi=10.1080%2f10473289.2004.10470914&partnerID=40&md5=33099fe593aacb3f1a537471dbd50fc8","A number of statistical techniques have been used to develop models to predict high-elevation ozone (O3) concentrations for each discrete hour of day as a function of elevation based on ground-level O3 observations. The analyses evaluated the effect of exclusion/inclusion of cloud cover as a variable. It was found that a simple model, using the current maximum ground-level O3 concentration and no effect of cloud cover provided a reasonable prediction of the vertical profile of O3, based on data analyzed from O3 sites located in North Carolina and Tennessee. The simple model provided an approach that estimates the concentration of O3 as a function of elevation (up to 1800 m) based on the statistical results with a ±13.5 ppb prediction error, an R2 of 0.56, and an index of agreement, d1, of 0.66. The inclusion of cloud cover resulted in a slight improvement in the model over the simple regression model. The developed models, which consist of two matrices of 24 equations (one for each hour of day for clear to partly cloudy conditions and one for cloudy conditions), can be used to estimate the vertical O3 profile based on the inputs of the current day’s 1-hr maximum ground-level O3 concentration and the level of cloud cover. © 2004 Air &amp; Waste Management Association."
"7003875148;6701728368;7102495313;","Model simulations of the arctic atmospheric boundary layer from the SHEBA year",2004,"10.1579/0044-7447-33.4.221","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042695845&doi=10.1579%2f0044-7447-33.4.221&partnerID=40&md5=29c0c20aa6a610b3a758fe6e4ff63524","We present Arctic atmospheric boundary-layer modeling with a regional model COAMPS™, for the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment. Model results are compared to soundings, near-surface measurements and forecasts from the ECMWF model. The near-surface temperature is often too high in winter, except in shorter periods when the boundary layer was cloud-capped and well-mixed due to cloud-top cooling. Temperatures are slightly too high also during the summer melt season. Effects are too high boundary-layer moisture and formation of too dense stratocumulus, generating a too deep well-mixed boundary layer with a cold bias at the simulated boundary-layer top. Errors in temperature and therefore moisture are responsible for large errors in heat flux, in particular in solar radiation, by forming these clouds. We conclude that the main problems lie in the surface energy balance and the treatment of the heat conduction through the ice and snow and in how low-level clouds are treated."
"55887849100;55887389300;22982762300;7403309955;55915388400;26658279600;55581974700;7006597288;22958999700;24546705400;","The Earthshine Project: Update on photometric and spectroscopic measurements",2004,"10.1016/j.asr.2003.01.027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042694268&doi=10.1016%2fj.asr.2003.01.027&partnerID=40&md5=fc7d17bcc1c8b4637041a523c58ee79d","The Earthshine Project is a collaborative effort between Big Bear Solar Observatory (New Jersey Institute of Technology) and the California Institute of Technology. Our primary goal is the precise determination of a global and absolutely calibrated albedo of the Earth and the characterization of its synoptic, seasonal and inter-annual variability. Photometric observations of the Earth's reflectance have been regularly carried out during the past 4 years. The up-to-date synoptic, seasonal and long-term variation in the Earth's albedo are reported in this paper, together with a comparison to model albedos using modern cloud satellite data and Earth Radiation Budget Experiment scene models. The Earth's albedo has a major role in determining the Earth's climate. The possibility of a response of this parameter to solar activity is also discussed. Simultaneously, spectrometric observations of the earthshine have been carried out at Palomar Observatory. The main goals and first results of those observations are also presented. © 2004 COSPAR. Published by Elsevier Ltd. All rights reserved."
"6603240618;57203079636;","Reconstruction of erythemal UV irradiance and dose at Hohenpeissenberg (1968-2001) considering trends of total ozone, cloudiness and turbidity",2004,"10.1007/s00704-004-0034-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2342573552&doi=10.1007%2fs00704-004-0034-y&partnerID=40&md5=b105cdbfa9ed6d1faa7f03ffec40afe3","Erythemal ultraviolet (UV) doses reaching the earth's surface depend in a complex manner on the amount of total ozone, cloud cover, cloud type and the structure of the cloud field. A statistical model was developed allowing the reconstruction of UV from measured total ozone and a cloud modification factor (CMF) for the GAW site Hohenpeissenberg, Germany (48°N, 11°E). CMF is derived from solar global radiation G, normalized against a Rayleigh scattering atmosphere. By this way the complex influence of the cloud field is accounted for by introduction of a measured parameter, exposed also to this complex field. The statistical relations are derived from the period 1990-1998 where UV measurements and relevant meteorological parameters are available. With these relations daily UV doses could be reconstructed back to 1968. Tests show that the model works remarkably well even for time scales of a minute except for situations with high albedo. The comparison of measured and calculated UV irradiances shows that the model explains 97% of the variance for solar elevations above 18° on average over the period 1968-2001. The reconstruction back to 1968 indicates that maximum UV irradiances (clear days) have increased due to long-term ozone decline. Clouds show seasonally depending long-term changes, especially an increase of citrus. Consequently the UV doses have increased less or even decreased in some months in comparison to the changes expected from the ozone decline alone. In May to August total cloud frequency and cloud cover have decreased. Therefore, the average UV doses have increased much more than can be explained by the ozone decline alone. It is also shown that the optical thickness of cirrus clouds has increased since 1953. The higher frequency of cirrus is caused in part by more frequent contrails. Besides that an observed long-term rise and cooling of the tropopause favors an easier cirrus formation. However, whether climate change and an intensification of the water cycle is responsible for the cirrus trends has not been investigated in detail. © Springer-Verlag 2004."
"7101846453;6504064936;","Origin of winter precipitation in the central coastal lowlands of Saudi Arabia",2004,"10.1016/S0140-1963(03)00091-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342332741&doi=10.1016%2fS0140-1963%2803%2900091-0&partnerID=40&md5=dade7015ebe3018177cab89787dd0c9e","The area under investigation is situated at the Gulf coast in Saudi Arabia north of Jubail Industrial City. The region is characterized by a Mediterranean climate regime displaying a hot and dry summer season and a cooler winter period with rainfall. The analysis of regional climate data was based on the measurements of three weather stations during three winter periods. For further analysis GMS 5(col) IR and MET5/7 IR satellite images were used in order to locate tracks of cyclones and cloud formations. During the observation period four different types of precipitation occurred: (1) cyclones from the Mediterranean Sea; (2) convection cells; (3) the formation of new cyclonic depressions in front of the Zagros Mountains above Iraq and eastern Iran; (4) currents from equatorial areas in Sudan and Ethiopia. The study demonstrates that apart from the well-known Mediterranean depressions there are at least three more characteristic weather situations, which may provide rain for the Eastern Province of Saudi Arabia. © 2003 Elsevier Ltd. All rights reserved."
"26027537400;7401968259;23479679000;","Overcast sky conditions and luminance distribution in Hong Kong",2004,"10.1016/j.buildenv.2003.06.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242306115&doi=10.1016%2fj.buildenv.2003.06.001&partnerID=40&md5=6db331ddb350a85c96943c22c9325586","In studying solar energy and daylight availability, particularly the sky luminance distributions, the required data are always analysed under various sky types which are categorised by some climatic parameters. Overcast days are important because they are used in more general sky models and appear quite frequent in some places. This paper studies some common climatic parameters including cloud cover, sunshine hour, solar irradiance, daylight illuminance and sky luminance and their applications in the classification of sky conditions. Frequency of occurrence of each parameter under overcast skies in Hong Kong has been established. It has been found that no single parameter can effectively describe the fully overcast skies and hybrid indices should be adopted. The general luminance distribution formula for the overcast sky with various luminance distribution parameter values has been used to test the selected sky luminance databases. The analysis indicates that the CIE standard overcast sky shows a good agreement with the overcast sky luminance distributions obtained in Hong Kong. © 2003 Elsevier Ltd. All rights reserved."
"7202928981;7101833247;","The accuracy of downward short- and long-wave radiation at the earth's surface calculated using simple models",2004,"10.1017/S1350482703001154","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2942579003&doi=10.1017%2fS1350482703001154&partnerID=40&md5=290210bf67421a73bf170daeeb90c8db","Estimates of the downward global solar and long-wave radiations are commonly made using simple models. We have tested the estimates produced by a number of these simple models against the values predicted by the radiative transfer model used in a climate model in order to determine their suitability for global applications. For clear sky, two simple models were comparable, but under cloudy conditions a combination of a clear-sky model based on the Angstrom-Prescott equation (which deals with the downwelling solar radiation) with a cloud transmissivity utilising total cloud fraction proved best. The lowest root mean square errors were 27 W m-2 for clear-sky global solar radiation and 90 W m-2 for cloudy conditions. For downward long-wave radiation in clear-sky conditions, the model of Garratt (1992) performed best with a root mean square error of 24 W m-2. However, in cloudy conditions the model of Idso &amp; Jackson (1969) performed best with a root mean square error of 22 W m-2, and, as it performs nearly as well as that of Garratt (1992) in clear-sky conditions, it is probably the best choice."
"6506191803;7410009029;7103050898;","Simulation of deforestation in eastern Amazonia using a high-resolution model",2004,"10.1007/s00704-004-0048-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042740593&doi=10.1007%2fs00704-004-0048-5&partnerID=40&md5=8011e3ae7595f85295be4bcadf5f24d4","This work evaluates the impact of deforestation on the climate of the eastern portion of the Amazon basin. This region is primarily an area of native tropical rainforest, but also contains several other natural ecosystems such as mangroves and savanna. It is the most densely populated area in Amazonia, and has been significantly affected by deforestation. In this study, numerical simulations were performed with a high spatial resolution, regional model that allows for consideration of mesoscale aspects such as topography, coastlines and large rivers. To evaluate the present situation and to predict potential future effects of deforestation on the climatic conditions of this region, two, one-year model simulations were made. In the first, ""control simulation"", an attempt was made to match the existing surface vegetation. The biophysical parameters used were derived from recent studies of similar Amazon-region ecosystems. In the second run, ""deforested simulation"", the forested-area biophysical parameters were replaced by those corresponding to the pasture areas of the region. The higher-resolution regional modelling revealed important climatic features of the deforestation process, displaying some associated mesoscale effects that are not typically represented in similar Global Circulation Model simulations. Near coastal zones and along large rivers, deforestation resulted in reduced cloud cover and precipitation. However, increased cloud cover and precipitation was predicted over upland areas, especially on slopes facing river valleys. The modelled surface sensible and latent heat fluxes also presented both positive and negative anomalies. The magnitudes of these anomalies were greater during the dry season. Windspeed near the surface was the meteorological variable that presented the most significant change due to deforestation. The reduction in roughness coefficient resulting from the shift from forest to pasture produced increased windspeeds near the Atlantic coast. The greater windspeeds diminished local humidity convergence and consequently reduced rainfall totals in nearby regions. The results obtained from these higher-resolution simulations show that, in general, orography, coastline profile and the distribution of large rivers play important roles in determining anomaly patterns of precipitation, wind, and energy exchange associated with deforestation in eastern Amazonia. © Springer-Verlag 2004."
"56231599000;7102737443;","Preliminary study of cosmic rays, geomagnetic field changes and possible climate changes",2004,"10.1016/j.asr.2004.02.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042639087&doi=10.1016%2fj.asr.2004.02.008&partnerID=40&md5=de4d50d85985d911405cb72573498317","The possibility of a connection between cosmic radiation and climate has intrigued scientists for the past several decades. The studies of Friis-Christensen and Svensmark reported a variation of 3-4% in the global cloud cover between 1980 and 1995 that appeared to be directly correlated with the change in galactic cosmic radiation flux over the solar cycle. However, not only the solar cycle modulation of cosmic radiation must be considered, but also the changes in the cosmic radiation impinging at the top of the atmosphere as a result of the long-term evolution of the geomagnetic field. We present preliminary results of an on-going study of geomagnetic cutoff rigidities over a 400-year interval. These results show: (1) the change in cutoff rigidity is sufficiently large over this 400-year period that the change in cosmic radiation flux impacting the earth is approximately equal to the relative change in flux over a solar cycle, and (2) the changes in cutoff rigidity are non-uniform over the globe with both significant increases and decreases at mid-latitude locations. © 2004 COSPAR. Published by Elsevier Ltd. All rights reserved."
"42962694100;7403697477;7402803216;7201567061;7409749484;56463154100;","Simulation of the radiative effect of black carbon aerosols and the regional climate responses over China",2004,"10.1007/BF02915731","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4143130897&doi=10.1007%2fBF02915731&partnerID=40&md5=3fad62b01e8378ae990165c829ecc60b","As part of the development work of the Chinese new regional climate model (RIEMS), the radiative process of black carbon (BC) aerosols has been introduced into the original radiative procedures of RIEMS, and the transport model of BC aerosols has also been established and combined with the RIEMS model. Using the new model system, the distribution of black carbon aerosols and their radiative effect over the China region are investigated. The influences of BC aerosole on the atmospheric radiative transfer and on the air temperature, land surface temperature, and total rainfall are analyzed. It is found that BC aerosols induce a positive radiative forcing at the top of the atmosphere (TOA), which is dominated by shortwave radiative forcing. The maximum radiative forcing occurs in North China in July and in South China in April. At the same time, negative radiative forcing is observed on the surface. Based on the radiative forcing comparison between clear sky and cloudy sky, it is found that cloud can enforce the TOA positive radiative forcing and decrease the negative surface radiative forcing. The responses of the climate system in July to the radiative forcing due to BC aerosols are the decrease in the air temperature in the middle and lower reaches of the Changjiang River and Huaihe area and most areas of South China, and the weak increase or decrease in air temperature over North China. The total rainfall in the middle and lower reaches of the Changjiang River area is increased, but it decreased in North China in July."
"55494077000;35618283200;7402590526;55335220500;","A coupled regional climate model for the Lake Victoria Basin of East Africa",2004,"10.1002/joc.983","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1142293891&doi=10.1002%2fjoc.983&partnerID=40&md5=eebcdf2b48e21e8269a7e96c3b072ee6","A nested coupled model has been developed to investigate the two-way interactions between the regional climate of eastern Africa and Lake Victoria. The atmospheric component of the model is the North Carolina State University (NCSU) version of the National Center for Atmospheric Research (NCAR) regional climate model (NCSU-RegCM2). The lake component of the model is based on the Princeton ocean model (POM). Three simulations, each 4 months long, have been performed for the short rains of eastern Africa of September through to December. The control experiment is based on the standard NCSU-RegCM2 model coupled to a one-dimensional model of Lake Victoria. The second experiment was based on the stand-alone three-dimensional primitive equation POM-Lake Victoria model forced by output from the atmospheric component of the control run. The third experiment is based on the integration of the coupled system of the NCSU-RegCM2 model where the one-dimensional lake model in the control run has been replaced by the three-dimensional POM hydrodynamical model for Lake Victoria. The results confirm that adopting the traditional modelling approach, in which the lake hydrodynamics are neglected and the formulation is based entirely on thermodynamics alone, is not entirely satisfactory for the Lake Victoria basin. Such a strategy precludes the transport of heat realistically within the lake, from the heat surplus regions to the cooler regions, and thereby results in a degraded simulation of the climate downstream over the rest of the lake and the surrounding land regions. The numerical simulations show that the southwestern region of the lake is an important source of warm water because it is relatively shallower and the water column is heated up much more quickly during the day than the rest of the lake. The result is that the surface temperature anomaly field from the all-lake area average consists of a gradient pattern with warmer water over the shallow region of the lake over the southeastern sector and a colder pool of water over the northeastern region, where the lake is relatively deeper. This pattern is also reproduced by the one-dimensional lake model. Some of the excess heat over the southeastern region is transported to the colder and deeper region over the northeastern put of the lake by prevailing surface wind flow. Through the lake atmosphere coupling, the resulting asymmetric lake-surface temperature distribution modifies the overlying wind circulation, which in turn reduces the cloud cover and rainfall. This secondary feature in the surface temperature structure cannot be generated by the traditional nested climate models, such as the standard version of the NCAR-RegCM2 model, since the simple static lake model formulation is not capable of supporting horizontal mixing of water. Comparisons show that this feature is weaker in the RegCM2-POM coupled model than the corresponding pattern that we obtained in our previous study based on the 'stand-alone' POM lake model. In contrast, from the simple classical text-book theoretical model of the lake-land breeze phenomena, the simulated surface wind circulation and rainfall distribution are highly asymmetric across the lake. © 2004 Royal Meteorological Society."
"7005634455;7005133082;55474342800;","Modeling the ENSO modulation of Antarctic climate in the late 1990s with the Polar MM5",2004,"10.1175/1520-0442(2004)017<0109:MTEMOA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1442291177&doi=10.1175%2f1520-0442%282004%29017%3c0109%3aMTEMOA%3e2.0.CO%3b2&partnerID=40&md5=906e5ad3ef1710d3cc795c6e38cde497","The Polar fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5) is employed to examine the El Nin̄o-Southern Oscillation (ENSO) modulation of Antarctic climate for July 1996-June 1999, which is shown to be stronger than for the mean modulation from 1979 to 1999 and appears to be largely due to an eastward shift and enhancement of convection in the tropical Pacific Ocean. This study provides a more comprehensive assessment than can be achieved with observational datasets by using a regional atmospheric model adapted for high-latitude applications (Polar MM5). The most pronounced ENSO response is observed over the Ross Ice Shelf-Marie Byrd Land and over the Weddell Sea-Ronne/Filchner Ice Shelf. In addition to having the largest climate variability associated with ENSO, these two regions exhibit anomalies of opposite sign throughout the study period, which supports and extends similar findings by other investigators. The dipole structure is observed in surface temperature, meridional winds, cloud fraction, and precipitation. The ENSO-related variability is primarily controlled by the large-scale circulation anomalies surrounding the continent, which are consistent throughout the troposphere. When comparing the El Niña/La Niña phases of this late 1990s ENSO cycle, the circulation anomalies are nearly mirror images over the entire Antarctic, indicating their significant modulation by ENSO. Large temperature anomalies, especially in autumn, are prominent over the major ice shelves. This is most likely due to their relatively low elevation with respect to the continental interior making them more sensitive to shifts in synoptic forcing offshore of Antarctica, especially during months with considerable open water. The Polar MM5 simulations are in broad agreement with observational data, and the simulated precipitation closely follows the European Centre for Medium-Range Weather Forecasts Tropical Ocean-Global Atmosphere precipitation trends over the study period. The collective findings of this work suggest the Polar MM5 is capturing ENSO-related atmospheric variability with good skill and may be a useful tool for future climate studies."
"24822802700;35271129900;7406099977;","The characteristics of climate change over the Tibetan Plateau in the last 40 years and the detection of climatic jumps",2004,"10.1007/BF02915705","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16544371015&doi=10.1007%2fBF02915705&partnerID=40&md5=4d684d29df1e4ad5e6aea446fa96c722","Through analyzing the yearly average data obtained from 123 regular meteorological observatories located in the Tibetan Plateau (T-P), this article studies the characteristics of climate change in T-P in the last 40 years. From the distribution of the linear trend, it can be concluded that the southeastern part of T-P becomes warmer and wetter, with an obvious increase of rainfall. The same characteristics are found in the southwestern part of T-P, but the shift is smaller. In the middle of T-P, temperature and humidity obviously increase with the center of the increase in Bangoin-Amdo. The south of the Tarim Basin also exhibits the same tendency. The reason for this area being humid is that it gets less sunshine and milder wind. The northeastern put of T-P turns warmer and drier. Qaidam Basin and its western and southern areas are the center of this shift, in which the living environment is deteriorating. Analyzing the characteristics of the regional average time series, it can be found that in the mid-1970s, a significant sudden change occurred to annual rainfall, yearly average snow-accumulation days and surface pressure in the eastern part of T-P. In the mid-1980s, another evident climatic jump happened to yearly average temperature, total cloud amount, surface pressure, relative humidity, and sunshine duration in the same area. That is, in the mid 1980s, the plateau experienced a climatic jump that is featured by the increase of temperature, snow-accumulation days, relative humidity, surface pressure, and by the decrease of sunshine duration and total cloud amount. The sudden climatic change of temperature in T-P is later than that of the global-mean temperature. From this paper it call be seen that in the middle of the 1980s, a climatic jump from warm-dry to warm-wet occurred in T-P."
"35461255500;6701574983;8871497700;57207261095;6701904979;26643041500;7004047498;7005956394;","Formation and growth rates of ultrafine atmospheric particles: A review of observations",2004,"10.1016/j.jaerosci.2003.10.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642492862&doi=10.1016%2fj.jaerosci.2003.10.003&partnerID=40&md5=82e68bd8e4652476ab323300228bf80f","Over the past decade, the formation and growth of nanometer-size atmospheric aerosol particles have been observed at a number of sites around the world. Measurements of particle formation have been performed on different platforms (ground, ships, aircraft) and over different time periods (campaign or continuous-type measurements). The development during the 1990s of new instruments to measure nanoparticle size distributions and several gases that participate in nucleation have enabled these new discoveries. Measurements during nucleation episodes of evolving size distributions down to 3 nm can be used to calculate the apparent source rate of 3-nm particles and the particle growth rate. We have collected existing data from the literature and data banks (campaigns and continuous measurements), representing more than 100 individual investigations. We conclude that the formation rate of 3-nm particles is often in the range 0.01-10 cm-3 s-1 in the boundary layer. However, in urban areas formation rates are often higher than this (up to 100 cm-3 s-1), and rates as high as 104-10 5 cm-3 s-1 have been observed in coastal areas and industrial plumes. Typical particle growth rates are in the range 1-20 nm h-1 in mid-latitudes depending on the temperature and the availability of condensable vapours. Over polar areas the growth rate can be as low as 0.1 nm h-1. Because nucleation can lead to a significant increase in the number concentration of cloud condensation nuclei, global climate models will require reliable models for nucleation. © 2003 Elsevier Ltd. All rights reserved."
"7402474749;7003310808;","The development of a warm-weather relative stress index for environmental applications",2004,"10.1175/1520-0450(2004)043<0503:TDOAWR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842787092&doi=10.1175%2f1520-0450%282004%29043%3c0503%3aTDOAWR%3e2.0.CO%3b2&partnerID=40&md5=d392e71fcac2be76326f947a0835df88","The heat stress index (HSI) is a new, comprehensive summer index that evaluates daily relative stress for locations throughout the United States based on deviations from the norm. The index is based on apparent temperature and other derived meteorological variables, including cloud cover, cooling degree-days, and consecutive days of extreme heat. Statistical distributions of meteorological variables are derived for 10-day periods of the annual cycle so that percentile values for each parameter can be determined. The daily percentile values for each variable are then summed, and a statistical distribution is fit to the summed frequencies. The daily HSI value is the percentile associated with the location of the daily summed value under the summation curve. The index is analyzed and spatially verified by comparing intra- and interregional results. Although stations from various climate regions have different criteria defining an excessive heat stress event, neighboring stations typically produce similar HSI results because they are usually affected by the same air mass. To test the effectiveness of the HSI, a relationship between the index results and mortality values is made. Overall, the highest mortality days are associated with the highest HSI values, but high-HSI days are not always associated with high numbers of deaths. A mortality study such as this one is just one of many potential environmental applications of the HSI. Other applications include implementing the index to correlate extreme weather conditions with resource consumption, such as electric-utility load, to determine conditions for which load levels are excessive. The ability to forecast the HSI using a variety of weather forecasting tools has also generated interest within various industries that have a need to issue weather stress advisories, watches, and warnings. © 2004 American Meteorological Society."
"7004937718;7402548443;8447628500;7005170580;7102511048;56283402900;57192975368;","Extrapolating future Arctic ozone losses",2004,"10.5194/acp-4-1849-2004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7244231222&doi=10.5194%2facp-4-1849-2004&partnerID=40&md5=ae005e8cde6db721ca05c2b0a0e32a38","Future increases in the concentration of greenhouse gases and water vapour may cool the stratosphere further and increase the amount of polar stratospheric clouds (PSCs). Future Arctic PSC areas have been extrapolated from the highly significant trends 1958-2001. Using a tight correlation between PSC area and the total vortex ozone depletion and taking the decreasing amounts of ozone depleting substances into account we make empirical estimates of future ozone. The result is that Arctic ozone losses increase until 2010-2015 and decrease only slightly afterwards. However, for such a long extrapolation into the future caution is necessary. Tentatively taking the modelled decrease in the ozone trend in the future into account results in almost constant ozone depletions until 2020 and slight decreases afterwards. This approach is a complementary method of prediction to that based on the complex coupled chemistry -climate models (CCMs). © European Geosciences Union 2004."
"7004154240;7404416268;","Atmospheric response to soil-frost and snow in Alaska in March",2004,"10.1007/s00704-003-0032-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18344405795&doi=10.1007%2fs00704-003-0032-5&partnerID=40&md5=227376f0b77a835eab25ae3264b972dd","A hydro-thermodynamic soil-vegetation model including soil freezing/thawing (soil-frost) and snow-metamorphism has been integrated into the PennState/NCAR Mesoscale Meteorological Model MM5 in a two-way coupled mode. A hierarchy of simulations with and without the soil-frost module, each combined with and without the snow module, shows the influence of snow-cover and soil-frost on weather in Alaska. Herein the landscape is featured as it is typically by mesoscale models. Theoretical considerations suggest that organic soil types should be considered in mesoscale modeling because of their different thermal and hydrological behavior as compared to mineral soils. The Ludwig-Soret and Dufour effects are small, but increase appreciably during freezing/thawing and snow-melt. The snow and soil-frost processes have a demonstrable impact on the surface thermal and hydrological regimes and on the near-surface atmospheric conditions even on the short (synoptic) timescales. The presence of snow-cover results in a highly stable stratification. In cloud-free areas, the enhanced loss of radiant energy and cooling of the air over snow-cover lead to a positive feedback to relatively colder, drier conditions. In cloudy areas, a positive feedback to warmer, moister conditions develops over snow-cover. As the changes in atmospheric humidity and temperature caused by snow-cover propagate into the pressure field, sea level pressure is lower by more than 1 hPa in the simulations with snow-cover. Although the effect of soil-frost alone is an order of magnitude smaller, the soil-frost snow system leads to an increase of the pressure difference to 1.2hPa. The changes in the pressure field alter wind speed and direction slightly. Soil-frost results in soil temperature differences of 2-5 K in the upper soil layers, while snow results in differences of 3-10 K. Soil-frost has a notably greater impact in cloud-free than cloudy areas. When a snow-cover is present, frozen soil enhances the insulating effect of a snow-cover in cloudy areas, but reduces it in cloud-free areas. In cloudy areas, soil-frost without snow-cover leads to cooler, drier atmospheric conditions relative to no frost. In cloudy areas, soil-frost under a snow-cover reduces the water supply to the atmosphere as compared to snow-covered conditions without soil-frost. The combined effects of soil-frost and snow increase precipitation locally by as much as 12.2 mm/48 h. If mesoscale modeling does not consider the soil-frost snow system, predicted water vapor fluxes will be too high in cloud-free areas, and too low in cloudy areas. © Springer-Verlag 2004."
"6701329624;6701553756;6602071545;","Fern species richness along a central Himalayan elevational gradient, Nepal",2004,"10.1046/j.0305-0270.2003.01013.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1542319942&doi=10.1046%2fj.0305-0270.2003.01013.x&partnerID=40&md5=dda71a4fe9d9e40777a7ef3d481b78b9","Aim: The study explores fern species richness patterns along a central Himalayan elevational gradient (100-4800 m a.s.l.) and evaluates factors influencing the spatial increase and decrease of fern richness. Location: The Himalayas stretch from west to east by 20°, i.e. 75-95° east, and Nepal is located from 80 to 88° east in this range. Methods: We used published data of the distribution of ferns and fern allies to interpolate species elevational ranges. Defining species presence between upper and lower elevation limit is the basis for richness estimates. The richness pattern was regressed against the total number of rainy days, and gradients that are linearly related to elevation, such as length of the growing season, potential evapotranspiration (PET, energy), and a moisture index (MI = PET/mean annual rainfall). The regressions were performed by generalized linear models. Results: A unimodal relationship between species richness and elevation was observed, with maximum species richness at 2000 m. Fern richness has a unimodal response along the energy gradients, and a linear response with moisture gradients. Main conclusions: The study confirms the importance of moisture on fern distributions as the peak coincides spatially with climatic factors that enhance moisture levels; the maximum number of rainy days and the cloud zone. Energy-related variables probably control species richness directly at higher elevations but at the lower end the effect is more probably related to moisture."
"6603395511;6602137840;6507681572;7004639116;8670213100;6701796418;","Ten-year global distribution of downwelling longwave radiation",2004,"10.5194/acp-4-127-2004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4043114797&doi=10.5194%2facp-4-127-2004&partnerID=40&md5=8c64bd09e393814cbd539bf5552dbc16","Downwelling longwave fluxes, DLFs, have been derived for each month over a ten year period (1984-1993), on a global scale with a spatial resolution of 2.5 × 2.5 degrees and a monthly temporal resolution. The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite and reanalysis data for the key atmospheric input parameters, i.e. cloud properties, and specific humidity and temperature profiles. The cloud climatologies were taken from the latest released and improved International Satellite Climatology Project D2 series. Specific humidity and temperature vertical profiles were taken from three different reanalysis datasets; NCEP/NCAR, GEOS, and ECMWF (acronyms explained in main text). DLFs were computed for each reanalysis dataset, with differences reaching values as high as 30 Wm-2 in specific regions, particularly over high altitude areas and deserts. However, globally, the agreement is good, with the rms of the difference between the DLFs derived from the different reanalysis datasets ranging from 5 to 7 Wm-2 . The results are presented as geographical distributions and as time series of hemispheric and global averages. The DLF time series based on the different reanalysis datasets show similar seasonal and inter-annual variations, and similar anomalies related to the 86/87 El Niño and 89/90 La Niña events. The global ten-year average of the DLF was found to be between 342.2 Wm-2 and 344.3 Wm-2, depending on the dataset. We also conducted a detailed sensitivity analysis of the calculated DLFs to the key input data. Plots are given that can be used to obtain a quick assessment of the sensitivity of the DLF to each of the three key climatic quantities, for specific climatic conditions corresponding to different regions of the globe. Our model downwelling fluxes are validated against available data from ground-based stations distributed over the globe, as given by the Baseline Surface Radiation Network. There is a negative bias of the model fluexes when compared against BSRN fluxes, ranging from -7 to -9 Wm-2, mostly caused by low cloud amount differences between the station and satellite measurements, particularly in cold climates. Finally, we compare our model results with those of other deterministic models and general circulation models. © European Geosciences Union 2004."
"35424175300;57217432361;","Changes of pan evaporation in the recent 40 years in the yellow river basin",2004,"10.1080/02508060408691814","https://www.scopus.com/inward/record.uri?eid=2-s2.0-11144221279&doi=10.1080%2f02508060408691814&partnerID=40&md5=fa7910faeaf5a9dce11fd5ea6bbf264c","Based on monitoring data of 123 meteorological stations from 1960 to 2000 near or in the Yellow River Basin, the spatial and temporal distributions and their trends for pan evaporation (PE) are investigated in this study. The results indicate that, despite the annual mean air temperature over the Yellow River Basin has, on average, increased by 0.6° over the past 40 years, the rate of PE has steadily decreased, especially in summer and spring. Compared with the period of 1960s to 1970s, the rate of annual pan evaporation during 1980s to 1990s has decreased by 126mm or 7.0 percent. Spatial distribution of the rate of change show that this kind of trend is general but not universal, PE has significantly decreased over the upper and lower reaches of the Yellow River, but increased to a small degree over the middle reaches. Further analyses show that the decrease of PE is mainly related to reductions in sunshine durations and solar irradiance, owing to more clouds and aerosols. © 2004, Taylor & Francis Group, LLC."
"6506730133;7004416203;","Impact of dynamically induced ozone mini-hole events on PSC formation and chemical ozone destruction",2004,"10.1016/j.asr.2003.08.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2042484718&doi=10.1016%2fj.asr.2003.08.001&partnerID=40&md5=bdf48c5c601ff84c12b59ffd6037169d","The impact of ozone mini-holes over the extra-tropics of the northern hemisphere on the heterogeneous ozone chemistry is investigated, based on simulations with the coupled climate-chemistry model ECHAM4.L39(DLR)/CHEM. Ozone mini-holes are synoptic-scale regions of strongly reduced total ozone, directly associated with upper troposphere high pressure systems. The simulated mini-hole events are validated with a mini-hole climatology based on daily ozone measurements with the total ozone mapping spectrometer (TOMS) instrument on the satellite Nimbus-7 between 1979 and 1993. Furthermore, the impact of mini-holes on the stratospheric heterogeneous ozone chemistry is investigated indirectly. For this purpose, polar stratospheric cloud formation inside mini-holes is suppressed during the model simulation. Heterogeneous processes inside mini-holes amount to one third of the heterogeneous ozone destruction in general over northern mid- and high-latitudes during winter (January-April). This ozone perturbation subsides and recovers during summer with an e-folding time of two months. © 2003 COSPAR. Published by Elsevier Ltd. All rights reserved."
"6701669739;7005523706;","A differential attenuation based algorithm for estimating precipitation from dual-wavelength spaceborne radar",2004,"10.5589/m04-036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-11144244805&doi=10.5589%2fm04-036&partnerID=40&md5=9f0b5199fe18b56d07ea231f977cc71e","An algorithm for estimating precipitation from dual-wavelength spaceborne radar measurements is formulated and investigated. The algorithm is based on a single-wavelength attenuation-correction procedure applied within discrete ranges [r1, r2] along a radar ray, satisfying the condition r2 – r1 ≤ 750 m. The attenuation-correction procedure is based on two parameters, namely the integrated attenuation from the top of the atmosphere to r1 and the intercept parameter (N*0) of the normalized gamma drop size distribution model. The N*0 value is assumed constant within the discrete range. A cost function is defined to evaluate the discrepancy between the two-wavelength precipitation estimates obtained from the corrected reflectivity profile within the discrete range. Consequently, the path-integrated attenuation to r1 and N*0 is determined through optimization, minimizing the cost function. The algorithm is investigated using synthetic data, i.e., derived from cloud model simulations, and airborne observations from the fourth convection and moisture experiment (CAMEX-4). © 2004, Taylor &amp; Francis Group, LLC. All rights reserved."
"7402839597;7004427005;35264812100;7004461406;7003271895;6602222092;7102083334;","GPS radio occultation with CHAMP: An innovative remote sensing method of the atmosphere",2004,"10.1016/S0273-1177(03)00591-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2042455858&doi=10.1016%2fS0273-1177%2803%2900591-X&partnerID=40&md5=a4f7e5ff534e5013fec5568f9fe93ec2","The availability of GPS (Global Positioning System) radio signals has introduced a new promising remote sensing technique for the Earth's atmosphere. GPS-based radio occultation exploits GPS signals received onboard a Low Earth Orbiting (LEO) satellite for atmospheric limb sounding. Temperature and water vapour profiles with high accuracy and vertical resolution can be derived from these measurements. The GPS radio occultation technique requires no calibration, is not affected by clouds, aerosols or precipitation, and the occultations are almost uniformly distributed over the globe. The radio occultation experiment aboard the German CHAMP (CHAllenging Minisatellite Payload) satellite provided its first measurements in February 2001. Since then up to 250 daily occultation measurements were performed. About 70% of these were successfully processed to yield atmospheric temperature and water vapour profiles. The CHAMP radio occultation experiment demonstrated the immense potential of this technique for the global monitoring of stratospheric temperature, the tropopause region and the global humidity distribution in the troposphere. All of these are important variables of the climate system. In this paper the GPS radio occultation experiment onboard CHAMP will be described. At GeoForschungsZentrum (GFZ) Potsdam an operational system was established to process CHAMP radio occultation data, orbit data, and GPS ground station observations in an automatic and operational way to derive profiles of atmospheric parameters. The CHAMP temperature bias compared to ECMWF analyses is less than 1.5 K between the tropopause layer and the 30 hPa level, and less than 0.5 K between 12 and 20 km at mid and high latitudes. Further comparisons between CHAMP atmospheric profiles and radiosonde data as well as applications of CHAMP radio occultation data for atmospheric research and climate monitoring are given. © 2003 COSPAR. Published by Elsevier Ltd. All rights reserved."
"7202840224;35510702700;7401688834;55544069300;6508112864;7005899862;56401230900;6602548572;55808070900;7003379342;","Water cycling in a Bornean tropical rain forest under current and projected precipitation scenarios",2004,"10.1029/2003WR002226","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2542550506&doi=10.1029%2f2003WR002226&partnerID=40&md5=807ebae8b6953ad5795dccb9cb9c6001","Southeastern Asian tropical rain forests are among the most important biomes in terms of annual productivity and water cycling. How their hydrologic budgets are altered by projected shifts in precipitation is examined using a combination of field measurements, global climate model (GCM) simulation output, and a simplified hydrologic model. The simplified hydrologic model is developed with its primary forcing term being rainfall statistics. A main novelty in this analysis is that the effects of increased (or decreased) precipitation on increased (or decreased) cloud cover and hence evapotranspiration is explicitly considered. The model is validated against field measurements conducted in a tropical rain forest in Sarawak, Malaysia. It is demonstrated that the model reproduces the probability density function of soil moisture content (s), transpiration (Tr), interception (Ic), and leakage loss (Q). On the basis of this model and projected shifts in precipitation statistics by GCM the probability distribution of Ic, Q and, to a lesser extent, s varied appreciably at seasonal timescales. The probability distribution of Tr was least impacted by projected shifts in precipitation."
"7102866124;7005247310;","The convective system area expansion over Amazonia and its relationships with convective system life duration and high-level wind divergence",2004,"10.1175/1520-0493(2004)132<0714:TCSAEO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842786458&doi=10.1175%2f1520-0493%282004%29132%3c0714%3aTCSAEO%3e2.0.CO%3b2&partnerID=40&md5=6a13fe197a7e0b6ae51547604bfbac1e","The relationships between the initial area expansion rate of tropical convective systems and their total life duration are analyzed during the period of the Wet Season Amazon Mesoscale Campaign/Large-Scale Biosphere-Atmosphere (WETAMC/LBA) experiment over tropical South America, using an objective tracking of convective systems during their life cycle from infrared Geostationary Operational Environmental Satellite (GOES) images. The results show that it is possible to estimate the probable lifetime of a convective system, within certain error bars, considering only its initial area expansion. This result shows that the initial area expansion could be used as a predictor of the life cycle of convective systems. The area expansion is also a good indicator of convective activity such as the diurnal cycle of convection. Over the southwest Amazon, the maximum area expansion occurs close to the time of maximum precipitation and about 4 h before the maximum cold cloud fraction at the same threshold (235 K). Also, the hypothesis that the area expansion, and hence the convective activity, impacts the high-level wind divergence has been investigated using satellite wind observations. It is found that the wind divergence fields derived are able to describe the large-scale patterns but are not able to capture the small-scale features. The diurnal cycle of the high-level wind divergence generally shows a flat response over tropical South America, although a coherent but not significant signal is observed over the WETAMC/LBA area. It is shown that the area of the cloud shield of convective systems varies not only in association with the upper-level wind divergence but also with the condensation-evaporation process. The increase of area in this initial stage is mainly due to the condensation process. During the ensuing mature stage, the upper-air wind divergence also contributes to the expansion. © 2004 American Meteorological Society."
"11240127200;6603931046;56212802600;6601943623;6603081063;35461763400;","Real-time measurements of ammonia, acidic trace gases and water-soluble inorganic aerosol species at a rural site in the Amazon Basin",2004,"10.5194/acp-4-967-2004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4544355423&doi=10.5194%2facp-4-967-2004&partnerID=40&md5=878ba22f0179862b250308304069a655","We measured the mixing ratios of ammonia (NHA3) nitric acid (HNO3) nitrous acid (HONO), hydrochloric acid (HCI), sulfur dioxide (SO2) and the corresponding water-soluble inorganic aerosol species, ammonium (NH4+), nitrate (NO3- ), nitrite (NO2-), chloride (Cl-) and sulfate (SO42-), and their diel and seasonal variations at a pasture site in the Amazon Basin (Rondônia, Brazil). This study was conducted within the framework of LBA-SMOCC (Large Scale Biosphere Atmosphere Experiment in Amazonia Smoke Aerosols, Clouds, Rainfall and Climate: Aerosols from Biomass Burning Perturb Global and Regional Climate). Sampling was performed from 12 September to 14 November 2002, extending from the dry season (extensive biomass burning activity), through the transition period to the wet season (background conditions). Measurements were made continuously using a wet-annular denuder (WAD) in combination with a Steam-Jet Aerosol Collector (SJAC) followed by suitable on-line analysis. A detailed description and verification of the inlet system for simultaneous sampling of soluble gases and aerosol compounds is presented. Overall measurement uncertainties of the ambient mixing ratios usually remained below 15%. The limit of detection (LOD) was determined for each single data point measured during the field experiment. Median LOD values (3σ-definition) were ≤0.015 ppb for acidic trace gases and aerosol anions and ≤0.118ppb for NH3 and aerosol NH+4. Mixing ratios of acidic trace gases remained below 1 ppb throughout the measurement period, while NH3 levels were an order of magnitude higher. Accordingly, mixing ratios of NH4+ exceeded those of other inorganic aerosol contributors by a factor of 4 to 10. During the wet season, mixing ratios decreased by nearly a factor of 3 for all compounds compared to those observed when intensive biomass burning took place. Additionally, N-containing gas and aerosol species featured pronounced diel variations. This is attributed to strong relative humidity and temperature variations between day and night as well as to changing photochemistry and stability conditions of the planetary boundary layer. HONO exhibited a characteristic diel cycle with high mixing ratios at nighttime and was not completely depleted by photolysis during daylight hours. © European Geosciences Union 2004."
"7004542776;7006738324;7102127179;","Enhancement of ERBS data by using data from sounders onboard NPP/NPOESS and METOP satellites",2004,"10.1016/S0273-1177(03)00751-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2042484717&doi=10.1016%2fS0273-1177%2803%2900751-8&partnerID=40&md5=4e636d885da0afb1a8e73e064bc282a1","The operational climate monitoring and diagnostic community will continue to favor in using outgoing longwave radiation (OLR) estimates that have long and continuous time series such as those estimated from the High Resolution Infrared Sounder (HIRS). OLR from HIRS data could be generated since these data exist since 1979 and will continue during NPOESS era with Cross-Track Infrared Sounder (CrIS) and HIRS/4 on NPOESS and METOP satellites, respectively. OLR estimated from Earth Radiation Budget Suite (ERBS)/Clouds and the Earth's Radiant Energy System (CERES) can be used to calibrate the HIRS technique that will be used to generate continuous time series of OLR. This will ensure to have a consistent climate data involving different data sources. OLR generated from CrIS on the afternoon orbit could provide a backup in the event of ERBS's failure. There will be three evenly spaced sounders (two CrIS and one HIRS/4) that could be used to retrieve OLR allowing therefore a better definition of the diurnal variability of OLR. This paper will present results from GOES sounder data to estimate OLR using an approach similar to that used for HIRS. The instantaneous OLR estimates are compared with collocated OLR products from the CERES instruments onboard TRMM and Terra spacecraft to establish the instantaneous accuracy of the multi-spectral estimation techniques for homogeneous scenes. The hourly GOES sounder OLR estimates are used to study the diurnal cycle of OLR. The time-averaged data are used to estimate the accuracy of the ERBE/CERES and HIRS diurnal cycle models as applied to daily- and monthly-averaged products at different spatial resolutions. The study suggests that the technique can be implemented for NPOESS using the CrIS and HIRS/4 for both augmenting the temporal sampling of OLR estimates and reducing the risk of OLR EDR generation. © 2003 COSPAR. Published by Elsevier Ltd. All rights reserved."
"7004994024;","A comparison of growing season agrometeorological stress and single-date Landsat NDVI for wheat yield estimation in west central Saskatchewan",2004,"10.5589/m03-054","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642618511&doi=10.5589%2fm03-054&partnerID=40&md5=d26acb235105a3104c0838901e0d9d73","Modeled moisture stress from three weather stations and normalized difference vegetation index (NDVI) values from historical Landsat images for an area of west central Saskatchewan were utilized to assess the yield potential of several wheat fields, some of which were suspected to have suffered residual herbicide damage. The study was initiated to assess whether the crop yields in recent years had been adversely affected by residual herbicide damage. There was a wide variation in wheat yields between fields within a growing season and between growing seasons. NDVI values from individual fields could not provide a reliable estimate of wheat yield. However, a linear regression of mean annual producer-reported wheat yields on mean growing season moisture stress from three weather stations that surrounded the study area was significant with a coefficient of determination (r2) of 0.85. Although mean annual producer-reported wheat yields showed a direct relationship with mean NDVI, the regression was not significant. Mean NDVI was also poorly correlated with mean growing season moisture stress. This may be partly related to the inability to source cloud-free Landsat images from late July when the wheat would normally be near peak growth. A within-year comparison of individual yields and NDVI values for fields that had been treated and those that had not been treated with herbicide showed that there was no statistical difference between them. © 2004, Taylor &amp; Francis Group, LLC. All rights reserved."
"7003265236;7005649482;7003886670;6701415209;7006686940;7004430325;7003967055;6603261697;7102653983;","Spatial and temporal variations in fluxes of energy, water vapour and carbon dioxide during OASIS 1994 and 1995",2004,"10.1023/A:1026028217081","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742288510&doi=10.1023%2fA%3a1026028217081&partnerID=40&md5=cb77b2d520184b89dfdc5bafc47638c2","This paper introduces the micrometeorological field campaigns known as OASIS (Observations At Several Interacting Scales) and then summarizes several companion studies that have used the OASIS dataset. Instrumented towers, aircraft and atmospheric sondes were used for measurements over three paired sites (crops and pastures), approximately equi-spaced along an 88-km transect in south-eastern New South Wales, Australia, during the austral springs of 1994 and 1995. Measurements included standard meteorological data and the fluxes of solar and net radiation, sensible heat, water vapour and the greenhouse gases CO2, N2O, CH4. Descriptions of the site, and the spatial and temporal variations of climate fields and fluxes, are presented. There were strong contrasts in fluxes and surface conductances, evaporation ratios and water use efficiencies between the 1994 drought year and the normal rainfall year of 1995. Despite greater incoming solar radiation in 1994 associated with less cloud cover, net radiation was lower than in 1995 because of greater outgoing thermal radiation caused by higher surface temperatures. In 1994 daily sensible heat fluxes were about 50% higher and evaporation rates about half those for 1995. Rainfall in the three-month growing season prior to the field campaigns was the key determinant of leaf area index, surface conductances and the fluxes of sensible and latent heat and CO2. Antecedent rainfall distribution also controlled variation in fluxes and surface properties along the transect within each year. There was a net loss of CO2 to the atmosphere at the drier central sites in 1994, and a net uptake at the wetter north-eastern sites. Both sites recorded uptake of CO 2 in 1995, but values were lower at the central site than at the north-east site due to the strong rainfall gradient along the transect in the three months prior to each field campaign. Differences in fluxes between crops and pastures at each site were smaller than between sites."
"7102944401;7006107059;7003968166;7402640769;7201640490;6602734013;","A 15-year climatology of warm conveyor belts",2004,"10.1175/1520-0442(2004)017<0218:AYCOWC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1442266686&doi=10.1175%2f1520-0442%282004%29017%3c0218%3aAYCOWC%3e2.0.CO%3b2&partnerID=40&md5=838e637f34f53006264964a4e9502199","This study presents the first climatology of so-called warm conveyor belts (WCBs), strongly ascending moist airstreams in extratropical cyclones that, on the time scale of 2 days, rise from the boundary layer to the upper troposphere. The climatology was constructed by using 15 yr (1979-93) of reanalysis data and calculating 355 million trajectories starting daily from a 1° × 1° global grid at 500 m above ground level (AGL). WCBs were defined as those trajectories that, during a period of 2 days, traveled northeastward and ascended by at least 60% of the zonally and climatologically averaged tropopause height. The mean specific humidity at WCB starting points in different regions varies from 7 to 12 g kg-1. This moisture is almost entirely precipitated out, leading to an increase of potential temperature of 15-22 K along a WCB trajectory. Over the course of 3 days, a WCB trajectory produces, on average, about four (six) times as much precipitation as a global (extratropical) average trajectory starting from 500 m AGL. WCB starting points are most frequently located between approximately 25° and 45°N and between about 20° and 45°S. In the Northern Hemisphere (NH), there are two distinct frequency maxima east of North America and east of Asia, whereas there is much less zonal variability in the Southern Hemisphere (SH). In the NH, WCBs are almost an order of magnitude more frequent in January than in July, whereas in the SH the seasonal variation is much weaker. In order to study the relationship between WCBs and cyclones, an independent cyclone climatology was used. Most of the WCBs were found in the vicinity of a cyclone center, whereas the reverse comparison revealed that cyclones are normally accompanied by a strong WCB only in the NH winter. In the SH, this is not the case throughout the year. Particularly around Antarctica, where cyclones are globally most frequent, practically no strong WCBs are found. These cyclones are less influenced by diabatic processes and, thus, they are associated with fewer high clouds and less precipitation than cyclones in other regions. In winter, there is a highly significant correlation between the North Atlantic Oscillation (NAO) and the WCB distribution in the North Atlantic: In months with a high NAO index. WCBs are about 12% more frequent and their outflow occurs about 10° latitude farther north and 20° longitude farther east than in months with a low NAO index. The differences in the WCB inflow regions are relatively small between the two NAO phases. During high phases of the Southern Oscillation, WCBs occur more (less) frequent around Australia (in the South Atlantic)."
"36851768400;55547129338;7201706787;7401548835;6603934441;","Observed and modeled relationships among Arctic climate variables",2003,"10.1029/2003jd003824","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642389341&doi=10.1029%2f2003jd003824&partnerID=40&md5=ab8847e01fde2dda1490bd0092d809d1","The complex interactions among climate variables in the Arctic have important implications for potential climate change, both globally and locally. Because the Arctic is a data-sparse region and because global climate models (GCMs) often represent Arctic climate variables poorly, significant uncertainties remain in our understanding of these processes. In addition to the traditional approach of validating individual variables with observed fields, we demonstrate that a comparison of covariances among interrelated parameters from observations and GCM output provides a tool to evaluate the realism of modeled relationships between variables. We analyze and compare a combination of conventional observations, satellite retrievals, and GCM simulations to examine some of these relationships. The three climate variables considered in this study are surface temperature, cloud cover, and downward longwave flux. Results show that the highest correlations between daily changes in pairs of variables for all three data sets occur between surface temperature and downward longwave flux, particularly in winter. There is less variability in GCM output, in part, because there is greater spatial averaging. Although the satellite products can be used to examine some of these relationships, additional work may be needed to ensure consistency between changes in radiative components of the energy budget and other retrieved quantities. The GCM's relationships between variables agree well with in situ observations, which provides some confidence that the GCM's representation of present-day climate is reasonable in high northern latitudes. Copyright 2003 by the American Geophysical Union."
"7801654745;7202621525;6603757377;","Solar-radiation-maintained glacier recession on Kilimanjaro drawn from combined ice-radiation geometry modeling",2003,"10.1029/2003jd003546","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342269740&doi=10.1029%2f2003jd003546&partnerID=40&md5=c318594dc3ef83c8639fdaface5c94da","In the context of investigating modern glacier recession on Kilimanjaro, which began around 1880, this study addresses the glacier regime of the vertical ice walls that typically form the margins of Kilimanjaro's summit glaciers. These walls have suffered a continuous lateral retreat during the twentieth century. To evaluate the role of solar radiation in maintaining glacier recession on Kilimanjaro, a radiation model is applied to an idealized representation of the 1880-ice cap. The combined process-based model calculates the spatial extent and geometry of the ice cap for various points in time after 1880. Support for input data and fundamental assumptions are provided by an automatic weather station that has operated on the summit's Northern Icefield since February 2000. Even in a simple climatic scenario only forced with an annual cycle of clouds, the basic evolution in spatial distribution of ice bodies on the summit is modeled well. The Northern and Southern Icefields form in characteristic east-west orientation, which verifies the basic idea behind the model. Forcing the model with further climate-related phenomena improves the results. It then additionally reproduces the Eastern Icefield, the third big ice entity on the summit. This study qualitatively demonstrates that solar radiation is the main climatic parameter maintaining modern glacier recession on Kilimanjaro summit, but also suggests that retreat on the inner ice cap margin might have been supported by a secondary energy source. The need for additional field measurements is emphasized in order to better understand the complex processes of glacier-climate interaction on Kilimanjaro. © 2003 by the American Geophysical Union."
"6602097544;57196499374;36076994600;7102294773;7404592426;7006159471;7003468747;6602996168;7202429440;","A model for the radiative forcing during ACE-Asia derived from CIRPAS Twin Otter and R/V Ronald H. Brown data and comparison with observations",2003,"10.1029/2002jd003260","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342269207&doi=10.1029%2f2002jd003260&partnerID=40&md5=21d102ff6fbd23e9e16d11e026be64da","Vertical profiles of aerosol size, composition, and hygroscopic behavior from Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter and National Oceanic and Atmospheric Administration R/V Ronald H. Brown observations are used to construct a generic optical model of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) aerosol. The model accounts for sulfate, black carbon, organic carbon, sea salt, and mineral dust. The effects of relative humidity and mixing assumptions (internal versus external, coating of dust by pollutants) are explicitly accounted for. The aerosol model is integrated with a Monte Carlo radiative transfer model to compute direct radiative forcing in the solar spectrum. The predicted regional average surface aerosol forcing efficiency (change in clear-sky radiative flux per unit aerosol optical depth at 500 nm) during the ACE-Asia intensive period is -65 Wm-2 for pure dust and -60 Wm-2 for pure pollution aerosol (clear skies). A three-dimensional atmospheric chemical transport model (Chemical Weather Forecast System (CFORS)) is used with the radiative transfer model to derive regional radiative forcing during ACE-Asia in clear and cloudy skies. Net regional solar direct radiative forcing during the 5-15 April 2001 dust storm period is -3 Wm-2 at the top of the atmosphere and -17 W m-2 at the surface for the region from 20°N to 50°N and 100°E to 150°E when the effects of clouds on the direct forcing are included. The model fluxes and forcing efficiencies are found to be in good agreement with surface radiometric observations made aboard the R.H. Brown. Mean cloud conditions are found to moderate the top of atmosphere (TOA) radiative forcing by a factor of ∼3 compared to clear-sky calculations, but atmospheric absorption by aerosol is not strongly affected by clouds in this study. The regional aerosol effect at the TOA (""climate forcing"") of -3 Wm-2 is comparable in magnitude, but of opposite sign, to present-day anthropogenic greenhouse gas forcing. The forcing observed during ACE-Asia is similar in character to that seen during other major field experiments downwind of industrial and biomass black carbon sources (e.g., the Indian Ocean Experiment (INDOEX)), insofar as the primary effect of aerosol is to redistribute solar heating from the surface to the atmosphere. © 2003 by the American Geophysical Union."
"7401559815;7405584618;","Warm rain processes over tropical oceans and climate implications",2003,"10.1029/2003GL018567","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642617896&doi=10.1029%2f2003GL018567&partnerID=40&md5=56dcf377ea4b43a93d977fe30f14f744","From analysis of TRMM data, we find that warm rain accounts for 31% of the total rain amount and 72% of the total rain area in the tropics, and plays an important role in regulating the moisture content of the tropical atmosphere. There is a substantial increase in precipitation efficiency of light warm rain as the sea surface temperature increases, but precipitation efficiency of heavy rain associated with deep convection is independent of sea surface temperature. This implies that in a warmer climate, there may be more warm rain, at the expense of less cloud water available for middle and high level clouds. Copyright 2003 by the American Geophysical Union."
"7102505167;","The geography and climatology of aerosols",2003,"10.1191/0309133303pp393ra","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347253674&doi=10.1191%2f0309133303pp393ra&partnerID=40&md5=a8c28aeb5450e687df182f00d8b659c7","Aerosols affect climate by scattering and absorbing radiation and by modifying the physical and radiative properties of clouds. Despite their importance in the climate system, the temporal and spatial variability of aerosols is not well understood. This paper briefly describes the nature of aerosols, their influence on the climate system and methods for quantifying atmospheric turbidity, which is the total column amount of aerosol. The main focus of the paper is a review of turbidity research that serves to document how and why aerosols vary over time and space. This analysis reveals that temporal and spatial variability in aerosol emissions is superimposed by temporal and/or spatial variability in meteorological and climatic factors. These factors include variability in wind speed, humidity, stability, insolation, frontal and cyclonic activity, the position of the Intertropical Convergence Zone and the polar front, rates of precipitation and convection, and the source regions of air masses. This interaction between aerosol emission characteristics and atmospheric processes is manifested in distinct trends in total column aerosol - described herein by geographic region - at a variety of spatial and temporal scales."
"7007018164;6504384849;","Profile of the climate change in the Kingdom of Bahrain",2003,"10.1002/env.620","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344287028&doi=10.1002%2fenv.620&partnerID=40&md5=127b2f6f78c9e9cd42d534e7c1368e8d","Long-term meteorological data from the Kingdom of Bahrain (1902 to 2001), along with other data from the Sultanate of Oman and the Kingdom of Saudi Arabia, were used to study the profile and the characteristics of the climate changes in the Kingdom of Bahrain. This article illustrates the possible effects of several factors, such as greenhouse gases (GHG), sunspot number, cosmic ray flux, planet conjunctions, the Earth's magnetic field, as well as volcanic eruption, on the profile of the climate change. In general, we found that the temperature variations, to a certain extent, are associated with the cyclic variations in sunspot number (the 11-year cycle), which in turn affect the pattern of the cosmic ray flux due to the distortion of the interplanetary magnetic field. The latter is believed to influence cloud formation. In addition, the discrepancy in the climate change pattern in Bahrain was also attributed to the combined effect of the high local level of CO2 emissions as well as that of other cooling gases in the region. Copyright © 2003 John Wiley &amp; Sons, Ltd."
"8721631200;57129153300;55434996700;55732536600;","Applications of Spatial Interpolation for Climate Variables Based on Geostatistics: A Case Study in Gansu Province, China",2003,"10.1080/10824000309480590","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450189970&doi=10.1080%2f10824000309480590&partnerID=40&md5=684ee5c61adaab3104b0f05b52892823","Based on reviewing the origin, development and basic principles of Geostatistics. this article mainly introduces two interpolation methods: Ordinary Kriging and Cokriging. As an optimal one among so many methods to spatial interpolation for climate variables is not available, the article discusses Geostatistics-based interpolation methods by using 30-year average precipitation and evaporation data in Gansu province from 1961 to 1990. According to different semivariogram theory models, we adopt Ordinary Kriging and Bivariate Cokriging interpolation methods, and compare research results. We draw the following conclusions: (1) Both 30-year average precipitation and evaporation present obvious gradient change on space, in a great range. But the former's is larger than the latter's. 30-year average precipitation decreases gradually from southeast to northwest, however, evaporation increases gradually from southeast to northwest. (2) According to semivariogram cloud plots and experiment variance minimum principle, we select suitable theoretical semivariogram models based on Geostatistics interpolation, which can simulate the spatially continuous distribution patterns of the special regionalized variables in a better way. Compared with Ordinary Kriging, Cokriging considers the influence of altitude on precipitation and evaporation and thereby has higher interpolation accuracy. (3) Though Geostatistics methods can better reflect the general space patterns of climate variables, their interpolations precision is not high as we expect and can be improved further. © 2003 Taylor & Francis Group, LLC."
"22933478600;","Variability of saturation deficit in Wrocław in the 20th century and some of its conditions",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-35349015292&partnerID=40&md5=1ca444852f3cc878eb69afb3b759eff2","The work is an attempt at the reconstruction and analysis of changes in the annual, half-yearly (winter and summer) and monthly mean values of the saturation deficit (d) in Wrocław in the 20th century. The problem of homogeneity of the data used for that purpose, in connexion with several changes in the localization of meteorological stations in Wrocław and the different times of observation, has been discussed. The analysis suggests the occurrence of several d rhythms of different periodicity and genesis. The issue has been presented in terms of the solar activity (Wolf's number) and of long-term circulation changes (influences of the NAO index) in Poland."
"7004160106;6602995001;7401559815;35425197200;","Simulating the midwestern U.S. drought of 1988 with a GCM",2003,"10.1175/1520-0442(2003)016<3946:STMUDO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346656460&doi=10.1175%2f1520-0442%282003%29016%3c3946%3aSTMUDO%3e2.0.CO%3b2&partnerID=40&md5=73505ffe7f319140efafdb10febcbd3a","Past studies have suggested that the drought of the summer of 1988 over the midwestern United States may have been caused by sea surface temperature (SST) anomalies, an evolving stationary circulation, a soil moisture feedback on circulation and rainfall, or even by remote forcings. The relative importance of various contributing factors is investigated in this paper through the use of Goddard Earth Observing System (GEOS) GCM simulations. Seven different experiments, each containing an ensemble of four simulations, were conducted with the GCM. For each experiment, the GCM was integrated through the summers of 1987 and 1988 starting from an analyzed atmosphere in early January of each year. In the baseline case, only the SST anomalies and climatological vegetation parameters were prescribed, while everything else (such as soil moisture, snow cover, and clouds) was interactive. The precipitation differences (1988 minus 1987) show that the GCM was successful in simulating reduced precipitation in 1988, but the accompanying low-level circulation anomalies in the Midwest were not well simulated. To isolate the influence of the model's climate drift, analyzed winds and analyzed soil moisture were prescribed globally as continuous updates (in isolation or jointly). The results show that remotely advected wind biases (emanating from potential errors in the model's dynamics and physics) are the primary cause of circulation biases over North America. Inclusion of soil moisture helps to improve the simulation as well as to reaffirm the strong feedback between soil moisture and precipitation. In a case with both updated winds and soil moisture, the model produces more realistic evapotranspiration and precipitation differences. An additional case also used soil moisture and winds updates, but only outside North America. Its simulation is very similar to that of the case with globally updated winds and soil moisture, which suggests that North American simulation errors originate largely outside the region. Two additional cases examining the influence of vegetation were built on this case using correct and opposite-year vegetation. The model did not produce a discernible improvement in response to vegetation for the drought year. One may conclude that the soil moisture governs the outcome of the land-atmosphere feedback interaction far more than the vegetation parameters. A primary inference of this study is that even though SSTs have some influence on the drought, model biases strongly influence the prediction errors. It must be emphasized that the results from this study are dependent upon the GEOS model's identified errors and biases, and that the conclusions do not necessarily apply to results from other models."
"55887849100;22982762300;55915388400;7403309955;26658279600;55887389300;55581974700;7006597288;22958999700;24546705400;","Earthshine and the Earth's albedo: 2. Observations and simulations over 3 years",2003,"10.1029/2003jd003611","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1442337213&doi=10.1029%2f2003jd003611&partnerID=40&md5=4988ad795468e7be034c7fb579d66564","Since late 1998, we have been making sustained measurements of the Earth's reflectance by observing the earthshine from Big Bear Solar Observatory. Further, we have simulated the Earth's reflectance for both the parts of the Earth in the earthshine and for the whole Earth. The simulations employ scene models of the Earth from the Earth Radiation Budget Experiment, simulated snow/ice cover, and near-real-time satellite cloud cover data. Broadly, the simulations and observations agree; however, there are important and significant differences, with the simulations showing more muted variations. During the rising phase of the Moon we measure the sunlit world to the west of California, and during the declining lunar phase we measure the sunlit world to the east. Somewhat surprisingly, the one third of the Earth to the west and that to the east have very similar reflectances, in spite of the fact that the topographies look quite different. The part to the west shows less stability, presumably because of the greater variability in the Asian cloud cover. We find that our precision, with steady observations since December 1998, is sufficient to detect a seasonal cycle. We have also determined the annual mean albedos both from our observations and from simulations. To determine a global albedo, we integrate over all lunar phases. Various methods are developed to perform this integration, and all give similar results. Despite sizable variation in the reflectance from night to night and from season to season (which arises from changing cloud cover), we use the earthshine to determine annual albedos to better than 1%. As such, these measurements are significant for measuring climate variation and are complementary to satellite determinations. Copyright 2003 by the American Geophysical Union."
"6602169738;57217771446;55470017900;7005981420;","Observations of blowing snow at the South Pole",2003,"10.1029/2002jd003327","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1442337221&doi=10.1029%2f2002jd003327&partnerID=40&md5=65e7f6a02af08672853a2d459618e767","Observations of blowing snow from visual observers' records as well as ground-based infrared and lidar measurements at South Pole Station are analyzed to obtain the first climatology of blowing snow over the Antarctic Plateau. Occurrence frequencies of blowing snow, wind direction and speed during blowing snow events, typical snow layer heights, as well as optical depths are determined. Blowing snow is recorded in roughly one third of the visual observations and occurs under a narrow range of wind directions. Blowing snow layers are usually less than 400 m in thickness but can exceed 1000 m. During blowing snow conditions, these near-surface layers are apparent in lidar backscatter profiles. These layers emit radiances similar to those from optically thin clouds frequently seen over the Antarctic Plateau. Because the near-surface blowing snow layers are frequently present, they are a factor in space-borne laser altimetry and other satellite remote sensing. Copyright 2003 by the American Geophysical Union."
"7005202019;7006081524;26643408200;7202163945;7003917155;35495958000;7005917593;7004299063;7101634666;7004227663;7102636633;55329219900;7402314813;7202548036;","Surface radiation budgets in support of the GEWEX Continental-Scale International Project (GCIP) and the GEWEX Americas Prediction Project (GAPP), including the North American Land Data Assimilation System (NLDAS) project",2003,"10.1029/2002jd003301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1442338676&doi=10.1029%2f2002jd003301&partnerID=40&md5=2479d28b1e0ad8ca3bd5154d14e9b67b","In support of the World Climate Research Program GEWEX Continental-Scale International Project (GCIP) and the GEWEX Americas Prediction Project (GAPP), real-time estimates of shortwave radiative fluxes, both at the surface and at the top of the atmosphere, are being produced operationally by the National Oceanic and Atmospheric Administration (NOAA)/National Environmental Satellite Data and Information Service using observations from GOES images. The inference scheme has been developed at the Department of Meteorology, University of Maryland, and the atmospheric and surface model input parameters are produced and provided by the NOAA/National Centers for Environmental Prediction. The radiative fluxes are being evaluated on hourly, daily, and monthly timescales using observations at about 50 stations. The satellite estimates have been found to be within acceptable limits during snow-free periods, but the difficulty in detecting clouds over snow affects the accuracy during the winter season. In what follows, this activity is discussed, and evaluation results of the derived fluxes against ground observations for time periods of 1-2 years are presented. Copyright 2003 by the American Geophysical Union."
"7403309955;22982762300;55887849100;55915388400;26658279600;55887389300;55581974700;7006597288;22958999700;24546705400;","Earthshine and the Earth's albedo: 1. Earthshine observations and measurements of the lunar phase function for accurate measurements of the Earth's Bond albedo",2003,"10.1029/2003jd003610","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1442288175&doi=10.1029%2f2003jd003610&partnerID=40&md5=c83bca8cf64c0238eee649fc8c75ac18","We have been making sustained observations of the earthshine from Big Bear Solar Observatory in California since late 1998. We also have intermittent observations from 1994-1995. We have reinvigorated and modernized a nearly forgotten way of measuring the Earth's albedo, and hence its energy balance, previously studied by A. Danjon and his followers for about 25 years early in the last century using their observations of the earthshine from France. This is the first in a series of papers covering observations and simulations of the Earth's reflectance from photometric and spectral observations of the Moon. Here, we develop a modern method of measuring, instantaneously, the large-scale reflectance of the Earth. From California we see the Moon reflecting sunlight from the third of the Earth to the west of us in our evening (before midnight, which is during the Moon's rising phase) and from the third of the Earth to our east in our morning (after midnight, which is during the Moon's declining phase). We have precisely measured the scattering from the Moon as a function of lunar phase, which enables us to measure, in a typical night's observations, the Earth's reflectance to an accuracy of 2.0% (equivalent to measuring the Earth's emission temperature to ∼0.8 K). We have also identified the lunar phase function as the major source of discrepancy between Danjon's estimates of the albedo and more recent measurements. The albedo is due to the interplay of cloud cover and different landscapes. Copyright 2003 by the American Geophysical Union."
"7004227663;7101634666;7202163945;7003917155;35495958000;7005917593;7004299063;36864686200;7102636633;55329219900;7402314813;7202548036;7005202019;7006081524;56828634300;","Real-time and retrospective forcing in the North American Land Data Assimilation System (NLDAS) project",2003,"10.1029/2002jd003118","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342288488&doi=10.1029%2f2002jd003118&partnerID=40&md5=dbafea151f38478fff067b958ac92ce6","The accuracy of forcing data greatly impacts the ability of land surface models (LSMs) to produce realistic simulations of land surface processes. With this in mind, the multi-institutional North American Land Data Assimilation System (NLDAS) project has produced retrospective (1996-2002) and real-time (1999-present) data sets to support its LSM modeling activities. Featuring 0.125° spatial resolution, hourly temporal resolution, nine primary forcing fields, and six secondary validation/model development fields, each data set is based on a backbone of Eta Data Assimilation System/Eta data and is supplemented with observation-based precipitation and radiation data. Hourly observation-based precipitation data are derived from a combination of daily National Center for Environmental Prediction Climate Prediction Center (CPC) gauge-based precipitation analyses and hourly National Weather Service Doppler radar-based (WSR-88D) precipitation analyses, wherein the hourly radar-based analyses are used to temporally disaggregate the daily CPC analyses. NLDAS observation-based shortwave values are derived from Geostationary Operational Environmental Satellite radiation data processed at the University of Maryland and at the National Environmental Satellite Data and Information Service. Extensive quality control and validation efforts have been conducted on the NLDAS forcing data sets, and favorable comparisons have taken place with Oklahoma Mesonet, Atmospheric Radiation Measurement Program/cloud and radiation test bed, and Surface Radiation observation data. The real-time forcing data set is constantly evolving to make use of the latest advances in forcing-related data sets, and all of the real-time and retrospective data are available online at http://ldas.gsfc.nasa.gov for visualization and downloading in both full and subset forms. Copyright 2003 by the American Geophysical Union."
"7005706662;","Spatial and temporal scales of precipitating tropical cloud systems in satellite imagery and the NCAR CCM3",2003,"10.1175/1520-0442(2003)016<3545:SATSOP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141804864&doi=10.1175%2f1520-0442%282003%29016%3c3545%3aSATSOP%3e2.0.CO%3b2&partnerID=40&md5=83104fbeb9fe24e71c82fe81c7794a60","Testing general circulation model parameterizations against observations is traditionally done by comparing simulated and observed, time-averaged quantities, such as monthly mean cloud cover, evaluated on a stationary grid. This approach ignores the dynamical aspects of clouds, such as their life cycle characteristics, spatial coverage, temporal duration, and internal variability. In this study, a complementary Lagrangian approach to the validation of modeled tropical cloudiness is explored. An automated cloud detection and tracking algorithm is used to observe and track overcast decks of cloud in a consecutive set of hourly Meteosat-5 images and the National Center for Atmospheric Research Community Climate Model version 3 (NCAR CCM3). The algorithm is applied to the deep convective cloud systems of the tropical Indian Ocean region during a 49-day period of the 1999 winter monsoon season. Observations of precipitation are taken from the Tropical Rainfall Measuring Mission (TRMM) satellite in addition to a Meteosat-5 infrared rainfall technique that is calibrated using the TRMM data. Clouds, defined as overcast decks, are observed spanning spatial scales from 25 km2 to greater than 107 km2, as well as temporal scales from 1 h to greater than 100 h. Semipermanent decks of anvil and cirrus cloud, with numerous regions of deep convection embedded within, dominate total cloud cover. Bridging between convective centers within the deck by cirrus clouds, particularly during the suppressed portion of the diurnal cycle of convection, may help to maintain the integrity of semipermanent overcast decks over long timescales. At scales greater than 10° km2 the size distribution of simulated clouds is biased such that the dominant scale of clouds is several million square kilometers larger than the dominant scale of observed clouds. Virtually all of the simulated precipitation occurs at rain rates lower than 2 mm h-1, while as much as 25% of observed precipitation occurs at rain rates higher than 2 mm h-1, Precipitation associated with deep convection in observed semipermanent cloud systems is organized into more localized mesoscale structures of adjacent convective cells attached to stratiform precipitation regions. A separate analysis of TRMM data by Wilcox and Ramanathan determined that such structures can exceed the size of grid cells in coarse-grid global models and have area-averaged rain rates up to and exceeding 2 mm h-1. These mesoscale convective systems are responsible for the extreme, episodic precipitation events that are not parameterized in the model. The simulated cloud systems gently precipitate throughout their duration and everywhere within their boundaries. The model lacks a process that acts to organize the convective cells within fewer grid cells, in addition to a representation of the observed stratiform precipitation structures. A modification to CCM3 is tested that is intended to account for the evaporation of upper-level precipitation in midlevel mesoscale downdrafts. The modification results in only a slight change in domain-averaged precipitation. However, it causes a significant shift in the distribution of precipitation toward higher rain rates that is more consistent with the distribution of TRMM observed rain rates. The modification demonstrates the sensitivity of the model to one important component of mesoscale organized convection."
"7004171611;7103010852;","Observations of the infrared outgoing spectrum of the Earth from space: The effects of temporal and spatial sampling",2003,"10.1175/1520-0442(2003)016<3820:OOTIOS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346056663&doi=10.1175%2f1520-0442%282003%29016%3c3820%3aOOTIOS%3e2.0.CO%3b2&partnerID=40&md5=9381cc6250f9c12779b2891fb30b5893","A recent comparison between data taken by two different satellite instruments, the Interferometric Monitor of Greenhouse Gases (IMG) that flew in 1997 and the Infrared Interferometer Spectrometer (IRIS) that flew in 1970, showed evidence of a change in the clear-sky greenhouse radiative forcing due to the increase in greenhouse gas concentrations between those years. A possibly even more intriguing question is whether the data can be used to extract unambiguous information about the radiative feedback processes that accompany such a change of forcing, especially cloud feedback. This paper is an investigation of this question, with particular reference to the uncertainties introduced into the differences between IMG and IRIS spectra due to their different patterns of temporal and spatial sampling. This has been approached by modeling the sampling problem, using high-resolution proxy scenes of top-of-the-atmosphere 11-μm brightness temperature, TB11, taken from International Satellite Cloud Climatology Project (ISCCP) data, sampled according to the characteristics of IRIS and IMG, respectively. The results suggest that while the sampling pattern of the IRIS instrument is sufficiently well distributed and dense to generate monthly regional mean brightness temperatures that are within 1.5 K of the true all-sky values, the IMG sampling is too sparse and yields results that differ from the true case by up to 6.0 K. Under cloud-free conditions the agreement with the true field for both instruments improves to within a few tenths of a kelvin. Comparisons with the observed IMG-IRIS difference spectra show that these uncertainties due to sampling presently limit the conclusions that can be drawn about climatically significant feedback processes. However, further analysis using the sampling characteristics of the Advanced Infrared Sounder (AIRS) instrument suggests that as climate change progresses, spectral measurements may be able to pick out significant changes due to processes such as cloud feedback."
"7003531755;6505526457;23082420800;9247651000;","Why is there an evaporation minimum at the equator?",2003,"10.1175/1520-0442(2003)016<3793:WITAEM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346056664&doi=10.1175%2f1520-0442%282003%29016%3c3793%3aWITAEM%3e2.0.CO%3b2&partnerID=40&md5=0aab318666fcfedc605c583520e78a1b","At all longitudes oceanic evaporation rates are lower on the equator than at latitudes to the north and south. Over the oceanic cold tongues this is related to the presence of cold water and divergence of heat by the ocean circulation. Herein is investigated why there is also a minimum over the Indo-Pacific warm pool. Model results confirm the recent suggestion of Sobel that deep convective clouds over the warm pool reduce the amount of solar radiation coming into the ocean that the evaporation has to balance. The results also confirm that this is only a partial explanation. Less evaporation over the warm pool than in the trade wind regions is also caused by an interaction between the ocean heat transport and the distribution of surface wind speeds. Low wind speeds over the warm pool reduce the latent heat flux and increase the SST, and stronger wind speeds in the off-equatorial regions of the Tropics increase the latent heat flux and cool the SST. Consequently, the wind speed distribution increases the meridional temperature gradient and increases the poleward ocean heat transport. Low latent heat fluxes over the warm pool can be sustained because the incoming solar radiation is partially offset by ocean heat flux divergence. Large values under the trade winds are sustained by ocean heat flux convergence. Climate models are used to show that, in equilibrium, wind speeds can only influence the latent heat flux distribution through their coupling to the ocean heat transport. In the presence of ocean heat transport, advection of moisture in the atmospheric boundary layer from the subtropics to the equator also increases the evaporation under the trade winds, but this has a much smaller effect than the wind speed or the cloud-radiation interactions."
"7801449033;56031450100;","Modeling decadal variability of the Baltic Sea: 2. Role of freshwater inflow and large-scale atmospheric circulation for salinity",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-1542286743&partnerID=40&md5=23f74a1929252a16cf774a277a928905","Hindcast simulations for the period 1902-1998 have been performed using a three-dimensional coupled ice-ocean model for the Baltic Sea. Daily sea level observations in Kattegat, monthly basin-wide discharge data, and reconstructed atmospheric surface data have been used to force the Baltic Sea model. The reconstruction utilizes a statistical model to calculate daily sea level pressure and monthly surface air temperature, dew point temperature, precipitation, and cloud cover fields. Sensitivity experiments have been performed to explore the impact of the freshwater and saltwater inflow variability on the salinity of the Baltic Sea. The decadal variability of the average salinity is explained partly by decadal volume variations of the accumulated freshwater inflow from river runoff and net precipitation and partly by decadal variations of the large-scale sea level pressure over Scandinavia. During the last century two exceptionally long stagnation periods are found, the 1920s to 1930s and the 1980s to 1990s. During these periods, precipitation, runoff, and westerly winds were stronger, and salt transports into the Baltic were smaller than normal. As the response timescale on freshwater forcing of the Baltic Sea is about 35 years, seasonal and year-to-year changes of the freshwater inflow are too short to affect the average salinity significantly. We found that the impact of river regulation, which changes the discharge seasonality, is negligible. Copyright 2003 by the American Geophysical Union."
"7006421134;57062286700;7403544649;25622266100;7003465848;6603247427;56228733900;57199296506;7103060756;8240597100;6603887794;","Tropical comulus convection and upward-propagating waves in Middle-Atmospheric GCMs",2003,"10.1175/1520-0469(2003)060<2765:TCCAUW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347185031&doi=10.1175%2f1520-0469%282003%29060%3c2765%3aTCCAUW%3e2.0.CO%3b2&partnerID=40&md5=32504ef8b13dc8a27ac726974aa72161","It is recognized that the resolved tropical wave spectrum can vary considerably among general circulation models (GCMs) and that these differences can have an important impact on the simulated climate. A comprehensive comparison of low-latitude waves is presented for the December-January-February period using high-frequency data from nine GCMs participating in the GCM Reality Intercomparison Project for Stratospheric Processes and Their Role in Climate (GRIPS: SPARC). Quantitative measures of the wavenumber-frequency structure of resolved waves and their impacts on the zonal mean circulation are given. Space-time spectral analysis reveals that the wave spectrum throughout the middle atmosphere is linked to the variability of convective precipitation, which is determined by the parameterized convection. The variability of the precipitation spectrum differs by more than an order of magnitude among the models, with additional changes in the spectral distribution (especially the frequency). These differences can be explained primarily by the choice of different cumulus parameterizations: quasi-equilibrium mass-flux schemes tend to produce small variability, while the moist-convective adjustment scheme is the most active. Comparison with observational estimates of precipitation variability suggests that the model values are scattered around the observational estimates. Among the models, only those that produce the largest precipitation variability can reproduce the equatorial quasi-biennial oscillation (QBO). This implies that in the real atmosphere, the forcing from the waves, which are resolvable with the typical resolutions of present-day GCMs, is insufficient to drive the QBO. Parameterized cumulus convection also impacts the nonmigrating tides in the equatorial region. In most of the models, momentum transport by diurnal nonmigrating tides in the mesosphere is comparable to or larger than that by planetary-scale Kelvin waves, being more significant than has been thought. It is shown that the westerly accelerations in the equatorial semi-annual oscillation in the models examined are driven mainly by gravity waves with periods shorter than 3 days, with some contribution from parameterized gravity waves, and that the contribution from the wavenumber-1 Kelvin waves is negligible. These results provide a state-of-the-art assessment of the links between convective parameterizations and middle-atmospheric waves in present-day middle-atmosphere climate models."
"6603809220;56611366900;","Sensitivity of the first indirect aerosol effect to an increase of cloud droplet spectral dispersion with droplet number concentration",2003,"10.1175/1520-0442(2003)016<3476:SOTFIA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346723147&doi=10.1175%2f1520-0442%282003%29016%3c3476%3aSOTFIA%3e2.0.CO%3b2&partnerID=40&md5=5b5275eed1c7ddf053a2031f9d5fcb99","Observations show that an increase in anthropogenic aerosols leads to concurrent increases in the cloud droplet concentration and the relative dispersion of the cloud droplet spectrum, other factors being equal. It has been suggested that the increase in effective radius resulting from increased relative dispersion may substantially negate the indirect aerosol effect, but this is usually not parameterized in global climate models (GCMs). Empirical parameterizations, designed to represent the average of this effect, as well as its lower and upper bounds, are tested in the CSIRO GCM. Compared to a control simulation, in which the relative dispersion of the cloud droplet spectrum is prescribed separately over land and ocean, inclusion of this effect reduces the magnitude of the first indirect aerosol effect by between 12% and 35%."
"7202208382;6701346974;57203054708;57193882808;","Breaking the cloud parameterization deadlock",2003,"10.1175/BAMS-84-11-1547","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141956622&doi=10.1175%2fBAMS-84-11-1547&partnerID=40&md5=ec1ad50bd272246978a5bada4f0217cf","A key factor limiting the reliability of simulations of anthropogenic climate change is the inability to accurately represent the various effects of clouds on climate. Despite the best efforts of the community, the problem has resisted solution for several decades. The reasons for this are briefly reviewed and it is argued that it will be many more decades before the problem can be solved through the approaches to cloud parameterization that have been used up to now. An alternative approach, called superparameterization, is then outlined, in which high-resolution cloud system-resolving models (CSRMs) are used in place of the conventional cloud parameterizations. Tests performed with the Community Atmosphere Model show that superparameterizations can give more realistic simulations of the current climate, including greatly improved simulations of the Madden-Julian oscillation and other tropical wave disturbances. Superparameterizations increase the cost of climate simulation by a factor of several hundred dollars, but can make efficient use of massively parallel computers. In addition, superparameterizations make it possible for a climate model to converge to a global CSRM as the horizontal grid spacing of the climate model decreases to a few kilometers. No existing global atmospheric model has this convergence property. Superparameterizations have the potential to greatly increase the reliability of climate change simulations."
"7006698304;6603422104;","Objective identification of cloud regimes in the Tropical Western Pacific",2003,"10.1029/2003GL018367","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642280532&doi=10.1029%2f2003GL018367&partnerID=40&md5=8b279de0a2202add879ac1d8dd2a67fb","Identifying cloud regimes and their role in the climate system can serve a multitude of purposes, ranging from a better understanding of clouds to guiding field experiments to improving the representation of clouds in models. This study describes early results in identifying cloud regimes from ISCCP data using cluster analysis. A simple algorithm for cloud regime identification is introduced and applied to data in the Tropical Western Pacific region. Four major cloud regimes, namely a shallow cumulus regime, a transparent isolated cirrus regime, thick cirrus with convection and a deep and probably organized convective regime are identified and their frequency of occurrence is quantified. The use of the regime information for various applications is discussed and the use of regime classifications for representativeness studies is presented using the ARM TWP sites as an example. Copyright 2003 by the American Geophysical Union."
"57193882808;","Impact of cloud microphysics on convective-radiative quasi equilibrium revealed by cloud-resolving convection parameterization",2003,"10.1175/1520-0442(2003)016<3463:IOCMOC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347353582&doi=10.1175%2f1520-0442%282003%29016%3c3463%3aIOCMOC%3e2.0.CO%3b2&partnerID=40&md5=b4aee7b22029311cb00c0b1e28b6f4f9","This paper investigates how cloud microphysics impact global convective-radiative quasi equilibrium on a constant-SST aquaplanet. A novel approach, the cloud-resolving convection parameterization (CRCP), also known as ""superparameterization,"" resolves both global dynamics and cloud-scale dynamics, as well as small-scale coupling among convective, radiative, and surface processes, within a single computational framework. As a result, the effects of cloud microphysics on the tropical large-scale dynamics and climate can be investigated with greater confidence than traditional approaches allow. Idealized simulations highlight extreme effects of the microphysical parameterizations to expose the impacts. The results suggest that cloud microphysics impact quasi-equilibrium temperature and moisture profiles substantially, but the relative humidity is only weakly affected. Small cloud and precipitation particles result in a climate that is warmer and moister. This is explained by the impact of cloud microphysics on the coupling between convection and surface exchange during the approach to quasi equilibrium. With interactive radiation, this effect is supplemented by gradual evolution of mean cloud fraction profiles and the mean radiative cooling. The mean quasi-equilibrium radiative cooling is weaker in the simulation featuring small cloud and precipitation particles. Cloud-radiation interactions, explicitly treated in CRCP, play a significant role in setting up the quasi-equilibrium cloudiness. The simulations further support the conjecture that the main impact of cloud microphysics in the Tropics is on the net energy budget at the ocean surface. The net energy flux into the ocean in quasi equilibrium is considerably smaller in simulations having small cloud and precipitation particles."
"15032788000;7202185413;7007061674;7004198777;7003529785;","Small, highly reflective ice crystals in low-latitude cirrus",2003,"10.1029/2003GL018153","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642405537&doi=10.1029%2f2003GL018153&partnerID=40&md5=87a20d2399f053a5a831009c89bdb303","At low latitudes, cirrus are ubiquitous and can be in excess of 100°C colder than the surface, limiting the amount of sunlight absorbed by the earth's atmosphere and surface, and reducing its loss of heat. Here we present aircraft measurements within cirrus over southern Florida indicating that ice crystals have smaller sizes and are more reflective than is assumed in most current climate models. If the measurements are generally representative of low-latitude cirrus, they point to a first-order correction to representations of how these clouds affect the earth's climate. Copyright 2003 by the American Geophysical Union."
"7004279859;57203235663;7801317846;6506579205;","Current and perturbed climate as simulated by the second-generation Canadian Regional Climate Model (CRCM-II) over northwestern North America",2003,"10.1007/s00382-003-0342-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141951080&doi=10.1007%2fs00382-003-0342-4&partnerID=40&md5=1dd0e1b822ca1bd1281ab9c7533c2e78","An updated version of the Canadian Regional Climate Model (CRCM-II) has been used to perform time-slice simulations over northwestern North America, nested in the coupled Canadian General Circulation Model (CGCM2). Both driving and driven models are integrated in a scenario of transient greenhouse gases (GHG) and aerosols. The time slices span three decades that were chosen to correspond roughly to single, double and triple current GHG concentration levels. Several enhancements have been implemented in CRCM-II since the CRCM-I climate-change simulations reported upon earlier. The larger computational domain, extending further to the west, north and south, allows for a better spin-up of weather systems as they enter the regional domain. The increased length of the simulations, from 5 to 10 years, strengthens the statistical robustness of the results. The improvements to the physical parameterisation, notably the moist convection scheme and the diagnostic cloud formulation, cure the excessive cloud cover problem present in CRCM-I, reduce the warm surface bias and prevent the occurrence of grid-point precipitation storms that occurred with CRCM-I in summer. The dynamical ocean and sea-ice components of CGCM2 that is used to provide atmospheric lateral and surface boundary conditions to CRCM-II, as well as the use of transient rather than equilibrium conditions of GHG and the inclusion of direct aerosols forcing, in both CGCM2 and CRCM-II, increase the realism of the CRCM-II climate-change simulation."
"7005729142;","Properties of tropical and midlatitude ice cloud particle ensembles. Part II: Applications for mesoscale and climate models",2003,"10.1175/1520-0469(2003)060<2592:POTAMI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344858006&doi=10.1175%2f1520-0469%282003%29060%3c2592%3aPOTAMI%3e2.0.CO%3b2&partnerID=40&md5=8ba9b0abfbdc919f97789bdbddb39fa0","This is the second part of a study that characterizes several bulk properties of ice particle populations sampled in synoptically generated midlatitude and convectively generated tropical ice clouds, for the purpose of developing empirical and analytical relationships that describe microphysical properties for use in mesoscale and climate models. The purpose of this paper is to examine the interrelationships between the mass, area, and fall velocity properties of the particle size distributions, and the dependence of these properties on temperature. Gamma distributions of the form N = N0Dμe-λD are fitted to the measured particle size distributions (PSDs) over sizes (D) from as small as 10 μm to as large as 1.5 cm. Exponential distributions (μ = 0) are also fitted to the PSD. The intercept parameter N0 and the slope λ are directly related, and decrease monotonically with increasing temperature. The μ values for the gamma fits tend from positive values at large λ to negative values at small λ. The maximum measured diameter Dmax increases with decreasing λ. The N0 values from the midlatitude clouds are about an order of magnitude lower than those for the tropical PSDs at the same temperatures. Bulk properties are derived from the fitted PSDs. The ice water contents (IWC) are about an order of magnitude higher for the tropical than for the midlatitude clouds. The median mass diameter (Dm) and the effective diameter (Dc) each increase with temperature, and are found to be related to each other. Several aspects related to the modeling of ice particle sedimentation in general circulation models (GCMs), and the relationship of these velocities to other bulk properties, are investigated. On average, the median mass-weighted terminal velocity (Vm) increase weakly with temperature. Correlations between Vm and IWC are also weak. It is found that for a given particle ensemble, most of the ice mass is contained within a relatively narrow range of fall velocities, although the values of Vm can be appreciable. Calculations reveal that the fallout of particles that dominate the extinction cannot be ignored, except at temperatures below -50°C. Also, the effective diameter is found to be strongly related to the ensemble mean Vm, perhaps allowing the two variables to be linked in GCMs."
"7003821079;7003663305;7005729142;7005035762;","Ice cloud optical thickness and extinction estimates from radar measurements",2003,"10.1175/1520-0450(2003)042<1584:ICOTAE>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346152818&doi=10.1175%2f1520-0450%282003%29042%3c1584%3aICOTAE%3e2.0.CO%3b2&partnerID=40&md5=f03ce100f6f27d1d83baed4117468181","A remote sensing method is proposed to derive vertical profiles of the visible extinction coefficients in ice clouds from measurements of the radar reflectivity and Doppler velocity taken by a vertically pointing 35-GHz cloud radar. The extinction coefficient and its vertical integral, optical thickness τ, are among the fundamental cloud optical parameters that, to a large extent, determine the radiative impact of clouds. The results obtained with this method could be used as input for different climate and radiation models and for comparisons with parameterizations that relate cloud microphysical parameters and optical properties. An important advantage of the proposed method is its potential applicability to multicloud situations and mixed-phase conditions. In the latter case, it might be able to provide the information on the ice component of mixed-phase clouds if the radar moments are dominated by this component. The uncertainties of radar-based retrievals of cloud visible optical thickness are estimated by comparing retrieval results with optical thicknesses obtained independently from radiometric measurements during the yearlong Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment. The radiometric measurements provide a robust way to estimate τ but are applicable only to optically thin ice clouds without intervening liquid layers. The comparisons of cloud optical thicknesses retrieved from radar and from radiometer measurements indicate an uncertainty of about 77% and a bias of about - 14% in the radar estimates of τ relative to radiometric retrievals. One possible explanation of the negative bias is an inherently low sensitivity of radar measurements to smaller cloud particles that still contribute noticeably to the cloud extinction. This estimate of the uncertainty is in line with simple theoretical considerations, and the associated retrieval accuracy should be considered good for a nonoptical instrument, such as radar. This paper also presents relations between radar-derived characteristic cloud particle sizes and effective sizes used in models. An average relation among τ, cloud ice water path, and the layer mean value of cloud particle characteristic size is also given. This relation is found to be in good agreement with in situ measurements. Despite a high uncertainty of radar estimates of extinction, this method is useful for many clouds where optical measurements are not available because of cloud multilayering or opaqueness."
"7005729142;","Properties of tropical and midlatitude ice cloud particle ensembles. Part I: Median mass diameters and terminal velocities",2003,"10.1175/1520-0469(2003)060<2573:POTAMI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344426165&doi=10.1175%2f1520-0469%282003%29060%3c2573%3aPOTAMI%3e2.0.CO%3b2&partnerID=40&md5=58c44ab1ff37379f58db5531bcc6c042","This is Part I of a study that characterizes several bulk properties of ice particle populations sampled in midlatitude and tropical cirrus and deep stratiform ice clouds, for the purpose of developing an understanding of how particles evolve in ice clouds and to derive empirical and analytical relationships that describe microphysical properties for use in cloud and climate models. The effort focuses on describing the microphysical properties of ice cloud layers in the vertical. The size distribution data and particle imagery were obtained during Lagrangian spiral descents and balloon-borne ascents through cloud layers that formed in association with synoptic-scale lifting (midlatitude) and deep convection (Tropics). Temperatures ranged between - 20° and -63°C for the midlatitude clouds and between 0° and -50°C for the tropical clouds. Optical depths spanned the range 0.4-7 for the midlatitude clouds and 20-30 for the tropical clouds. This part of the study characterizes median mass diameter (Dm and median fall velocities (Vm) for the more than 2000 ensembles or particle size distributions (PSDs) examined. The Dm and Vm increase downward from cloud top to base, with the smallest Dm and Vm values found in the coldest (midlatitude) clouds and the largest values found in the warmest (tropical) clouds. The range of sizes that dominate the ice water content, and the associated range of particle fall speeds, are characterized in terms of Dm and Vm. The Vm are represented in terms of Dm and the slopes (λ) of gamma distributions fitted to the particle size distributions. The Vm values increase with Dm and decrease with λ in a predictable manner. The magnitudes of the changes in Vm that result from differing ambient pressures between 250 and 1000 hPa are quantified. The observations are generalized so that the results can be extended to different pressure levels and other particle size distributions. The coefficients γ and β in the power-law relationship V1 = γDβ fitted to the individual spectra are found to be inversely related to Dm. Many carlier studies have derived these coefficients from measurements at the surface. The wide variability noted in these coefficients may partially be attributed to variations in the Dm values of the populations considered. The relationship of the γ and β coefficients found for particle ensembles at the surface to those at the pressure levels of ice clouds are derived."
"7004014731;56228733900;7103342287;35550043200;6701834461;","Fluctuations of cloud, humidity, and thermal structure near the tropical tropopause",2003,"10.1175/1520-0442(2003)016<3428:FOCHAT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346723152&doi=10.1175%2f1520-0442%282003%29016%3c3428%3aFOCHAT%3e2.0.CO%3b2&partnerID=40&md5=679bdc0cad0524565e17216b59574b9e","Thermal and humidity structures near the tropical tropopause are studied using microwave satellite retrievals of water vapor, along with contemporaneous dynamical structure in ECMWF analyses and cold clouds in high-resolution global cloud imagery. Examined during November 1991-February 1992, these fields all vary coherently with the outflow from convective centers-in the upper troposphere as well as in the lowermost stratosphere. The outbreak of deep convection is accompanied by diabatic heating below a level between 250 and 150 mb but by diabatic cooling at higher levels. The reversal from heating to cooling is broadly consistent with cumulus detrainment. Through irreversible mixing, that process serves as a heat source for the environment below the level of neutral buoyancy (LNB) but as a heat sink at higher levels. Calculations, inclusive of entrainment, place the LNB very near the observed reversal from heating to cooling. The outbreak of convection is also accompanied by humidification below 125 mb but by dehydration at higher levels. The reversal from humidification to dehydration coincides with levels where environmental conditions approach saturation. Those conditions suggest the efficient removal of total water from cumulus updrafts, leaving dessicated air to ventilate to higher levels. Cumulus detrainment then acts to humidify the environment beneath the zone of nearly saturated environmental conditions, while dehydrating it at higher levels. Dry air emerges from the region of the coldest cloud. It then extends into the winter hemisphere, along streamlines that characterize the Hadley circulation. Coinciding with diabatic cooling are stratospheric convergence and downwelling. These features of stratospheric motion amplify simultaneously with divergence at tropospheric levels, which represents the major outflow from deep convection. The deepest convection, found over the equatorial Pacific, coincides with the highest moist static energy. The latter yields an LNB that is some 3 km higher over the equatorial Pacific than elsewhere, in agreement with the observed reversal from heating to cooling. Observed brightness temperatures place the level at which cumulus anvils are most extensive very near the cold point over the equatorial Pacific. This, in turn, lies near the tropical tropopause throughout the Tropics. Collectively, these features suggest that the coldest cloud, found over the equatorial Pacific, plays a key role in maintaining temperature and humidity near the tropical tropopause."
"7006783796;8280879000;8723505700;7101907794;","Contrail frequency over the United States from surface observations",2003,"10.1175/1520-0442(2003)016<3447:CFOTUS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347353583&doi=10.1175%2f1520-0442%282003%29016%3c3447%3aCFOTUS%3e2.0.CO%3b2&partnerID=40&md5=2c6393ecd8f94b5c690c065a1d5db6a9","Contrails have the potential for affecting climate because they impact the radiation budget and the vertical distribution of moisture. Estimating the effect requires additional knowledge about the temporal and spatial variations of contrails. The mean hourly, monthly, and annual frequencies of daytime contrail occurrence are estimated using 2 yr of observations from surface observers at military installations scattered over the continental United States. During both years, persistent contrails are most prevalent in the winter and early spring and are seen least often during the summer. They co-occur with cirrus clouds 85% of the time. The annual mean persistent contrail frequencies in unobscured skies dropped from 0.152 during 1993-94 to 0.124 in 1998-99 despite a rise in air traffic. Mean hourly contrail frequencies reflect the pattern of commercial air traffic, with a rapid increase from sunrise to midmorning followed by a very gradual decrease during the remaining daylight hours. Although highly correlated with air traffic fuel use, contrail occurrence is governed by meteorological conditions. It is negatively and positively correlated with the monthly mean 300-hPa temperature and 300-hPa relative humidity, respectively, from the National Centers for Environmental Prediction (NCEP) reanalyses. A simple empirical model employing the fuel use and the monthly mean 300-hPa temperatures and relative humidities yields a reasonable representation of the seasonal variation in contrail frequency. The interannual drop in contrail frequency coincides with a decrease in mean 300-hPa relative humidities from 45.8% during the first period to 38.2% in 1998-99, one of the driest periods in the NCEP record."
"7003279098;55739684700;7006171750;7003443591;","The sensitivity of dimethyl sulfide production to simulated climate change in the Eastern Antarctic Southern Ocean",2003,"10.1034/j.1600-0889.2003.00077.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242349261&doi=10.1034%2fj.1600-0889.2003.00077.x&partnerID=40&md5=3ce15aeaa8dc2cdc6d94245d81f3bbb2","Dimethyl sulfide (DMS) is a radiatively active trace gas produced by enzymatic cleavage of its precursor compound, dimethyl sulfoniopropionate (DMSP), which is released by marine phytoplankton in the upper ocean. Once ventilated to the atmosphere, DMS is oxidised to form non-sea-salt sulfate and methane sulfonate (MSA) aerosols, which are a major source of cloud condensation nuclei (CCN) in remote marine air and may thus play a role in climate regulation. Here we simulate the change in DMS flux in the Eastern Antarctic ocean from 1960-2086, corresponding to equivalent CO2 tripling relative to pre-industrial levels. Calibration to contemporary climate conditions was carried out using a genetic algorithm to fit the model to surface chlorophyll from the 4-yr SeaWiFs satellite archive and surface DMS from an existing global database. Following the methodology used previously in the Subantarctic Southern Ocean, we then simulated DMS emissions under enhanced greenhouse conditions by forcing the DMS model with output from a coupled atmospheric-ocean general circulation model (GCM). The GCM was run in transient mode under the IPCC/IS92a radiative forcing scenario. By 2086, the change simulated in annual integrated DMS flux is around 20% in ice-free waters, with a greater increase of 45% in the seasonal ice zone (SIZ). Interestingly, the large increase in flux in the SIZ is not due to higher in situ production but mainly because of a loss of ice cover during summer-autumn and an increase in sea-to-air ventilation of DMS. These proportional changes in areal mean flux (25%) are much higher than previously estimated for the Subantarctic Southern Ocean (5%), and point to the possibility of a significant DMS-climate feedback at high Southern latitudes. Due to the nexus between ice cover and food-web structure, the potential for ecological community shifts under enhanced greenhouse conditions is high, and the implications for DMS production are discussed."
"57202245193;","Warming trends in the Arctic from clear sky satellite observations",2003,"10.1175/1520-0442(2003)016<3498:WTITAF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347353591&doi=10.1175%2f1520-0442%282003%29016%3c3498%3aWTITAF%3e2.0.CO%3b2&partnerID=40&md5=bb4529e9f2448b9df9c885d5e71521a7","Satellite thermal infrared data on surface temperatures provide pan-Arctic coverage from 1981 to 2001 during cloud-free conditions and reveal large warming anomalies in the 1990s compared to the 1980s and regional variability in the trend. The rms error of the derived surface temperatures when compared with in situ data ranges from 1.5 to 3 K over the 20-yr period. Average temperature trends are generally positive at 0.33 ± 0.16°C decade-1 over sea ice, 0.50 ± 0.22°C decade-1 over Eurasia, and 1.06 ± 0.22°C decade-1 over North America. The trend is slightly negative and insignificant at -0.09 ± 0.25°C decade-1 in Greenland with the negatives mainly at high elevations. The trends are also predominantly positive in spring, summer, and autumn causing the lengthening of the melt season by 10-17 days per decade while they are generally negative in winter. The longer-term in situ surface temperature data shows that the 20-yr trend is 8 times larger than the 100-yr trend suggesting a rapid acceleration in the warming that may be associated with the recent change in phase of the Arctic Oscillation that has been linked to increasing greenhouse gases in the atmosphere."
"7406543625;7501630594;37102465800;","Potential vorticity diagnostics of a Mei-Yu front case",2003,"10.1175/1520-0493(2003)131<2680:PVDOAM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346752403&doi=10.1175%2f1520-0493%282003%29131%3c2680%3aPVDOAM%3e2.0.CO%3b2&partnerID=40&md5=cb738681b72fd04a6d87314703961b0a","The present study selects the mei-yu frontal case of 12-13 June 1990 over southeastern China, and performs potential vorticity (PV) diagnostic analysis to discuss the mechanism responsible for the intensification and maintenance of frontal vorticity. The mei-yu front had typical characteristics at the western section, and was shallow with weak baroclinity but strong horizontal shear vorticity. For this particular case, results of piecewise PV inversion indicate that latent heat release associated with both deep convections and stratiform clouds was responsible for the frontal vorticity, and the apparent frontogenesis near 0000 UTC 13 June was driven almost entirely by an outbreak of deep convections along the front, through the conditional instability of the second kind (CISK) mechanism proposed by Cho and Chen. The positive feedback between the mei-yu frontogenesis and cumulus latent heating, in which the front provided low-level convergence and helped organize the convection while latent heating by cumuli generated low-level PV and further enhanced the frontogenesis process, led to rapid growth in shear vorticity along the front. A low-level jet (LLJ) subsequently developed to the immediate south of the front through Coriolis acceleration of isallobaric winds. It is also found that the heating efficiency during this process depended upon the initial low-level PV value when deep convections started, and thus convections south of the front were ineffective in producing a similar response in either PV or wind field. Finally, an upper-level jet streak appeared to provide additional lifting at the outbreak of deep convection in the present case, but its role is secondary compared to the presence of the front itself in providing PV values sufficiently large in the background."
"7005650812;7408612236;","Explaining sources of discrepancy in SSM/I water vapor algorithms",2003,"10.1175/1520-0442(2003)016<3229:ESODII>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344984319&doi=10.1175%2f1520-0442%282003%29016%3c3229%3aESODII%3e2.0.CO%3b2&partnerID=40&md5=fd3d12ff9a36682303ae6e16caa27189","This study examines a mix of seven statistical and physical Special Sensor Microwave Imager (SSM/I) passive microwave algorithms that were designed for retrieval of over-ocean precipitable water (PW). The aim is to understand and explain why the algorithms exhibit a range of discrepancies with respect to measured PWs and with respect to each other, particularly systematic regional discrepancies that would produce substantive uncertainties in water vapor transports and radiative cooling in the context of climate dynamics. Data analysis is used to explore the nature of the algorithm differences, while radiative transfer analysis is used to explore the influence of several environmental variables (referred to as tangential environmental factors) that affect the PW retrievals. These are sea surface temperature (SST), surface wind speed (Us), cloud liquid water path (LWP), and vertical profile structure of water vapor [q(z)]. The main datasets include the Wentz matched radiosonde-SSM/I point database consisting of 42 months of globally distributed oceanic radiosonde profiles paired with coincident SSM/I brightness temperatures, and globally compiled instantaneous orbit-swath maps of SSM/I brightness temperatures for January and July 1990. Results demonstrate that the seemingly good agreement found in past studies and herein, within the conventional framework of scatter diagram analysis that ignores regional classification, gives way to poor agreement in the framework of monthly and zonally averaged differences. It is shown how much of the disagreement inherent to statistical algorithms is due to disjoint training datasets used in deriving algorithm regression coefficients. The investigation also explores how tangential environmental factors composed of variations in SST. Us, cloud LWP, and q(z) structure impart dissimilar errors to retrieved PWs, according to the design of the retrieval algorithms. A discussion on implications of the discrepancies vis-à-vis the Global Energy and Water Cycle Experiment program is given, with suggestions on mitigating discrepancies in algorithm designs."
"24492486300;6603148881;6601956073;","Convective scheme and resolution impacts on seasonal precipitation forecasts",2003,"10.1029/2003GL018297","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1242345156&doi=10.1029%2f2003GL018297&partnerID=40&md5=8b212c21ac1c7759c27aca3198350c31","An investigation is carried out to assess the role of different convective schemes and resolutions in seasonal quantitative forecasts of precipitation. The model performances are evaluated by changing convective schemes and the resolution impacts are examined by increasing the model horizontal resolution from T63 to T170 and finally T255. The predicted rainfall amounts are compared against the TRMM satellite estimate. Every forecast captures prominent rainfall features reasonably well. However, there are pros and cons in each of the forecasts. Predicted seasonal rainfall patterns and intensities from changing convective schemes exhibit larger variability and higher impact on predictability than those from increasing resolution. The impact of higher resolution with any currently implemented cumulus parameterization turns out to be smaller in seasonal precipitation forecasts than in short- to medium-range forecasts. © 2003 by the American Geophysical Union."
"7006698304;","An improved strategy for the evaluation of cloud parameterizations in GCMS",2003,"10.1175/BAMS-84-10-1387","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242696062&doi=10.1175%2fBAMS-84-10-1387&partnerID=40&md5=5e2146401054bebc0000476e78632b5a","The parameterization schemes - Used to represent clouds in general circulation models have significantly evolved in their complexity over the last 10 yr. This increases the demand for a thorough evaluation of their performance. Several techniques ranging from the evaluation of the model climate to single column modeling have been proposed for that purpose. This paper aims to provide a strategy for an improved, more coherent use of these techniques. An over -view of the different techniques is given using examples from the evaluation of the global model of the European Centre for Medium Range Weather Forecasts. Advantages and disadvantages of the individual methods are highlighted. The paper closes by proposing a strategy to join the different techniques into a coherent procedure of cloud parameterization evaluation."
"7201443624;7003976079;7004034323;","Evaluation of moisture in the Hadley Centre climate model using simulations of HIRS water-vapour channel radiances",2003,"10.1256/qj.02.217","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042308778&doi=10.1256%2fqj.02.217&partnerID=40&md5=8a77bcbec17354a26c1f2adc43c4a7a5","It is important to establish that climate models can accurately simulate the observed present-day fluctuations of water vapour. In particular, water-vapour and cloud-radiative feedbacks are intrinsically linked to processes governing relative-humidity distribution and variability. To explore these issues, clear-sky radiances, sensitive to upper-tropospheric relative humidity, are simulated within the Hadley Centre atmospheric climate model, version HadAM3, allowing direct comparison with High Resolution Infrared Sounder (HIRS) observations. The model is forced by observed sea surface temperatures and sea-ice fields over the period 1979-98. Evaluation of the simulated distribution and variability of water vapour is undertaken utilizing the HIRS 6.7 μm brightness temperature (T6.7) and satellite measurements of column-integrated water vapour and clear-sky outgoing longwave radiation (OLR). Modifications are made to the clear-sky OLR and T6.7 HadAM3 diagnostics to reduce sampling inconsistencies with the observed products. Simulated T6.7 over subtropical dry zones are higher than T6.7 from observations, particularly in the southern hemisphere, and is symptomatic of an overactive circulation. The observed spatial signature of the T6.7 interannual variability is dominated by El Niño and is captured well by HadAM3. Interannual variability of the tropical ocean mean T6.7 is consistent between HadAM3 and the HIRS observations, suggesting that the small simulated decadal changes in relative humidity are realistic."
"7005071210;6602466905;7005682116;55768583400;","Were southern Swedish summer temperatures before 1860 as warm as measured?",2003,"10.1002/joc.945","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242318735&doi=10.1002%2fjoc.945&partnerID=40&md5=dad496da5b56ea389726496c0caf6a5d","Temperature series from Stockholm and Uppsala in southern Sweden indicate that summers from the mid-18th century until around 1860 were, on average, warmer than the 1961-90 mean. The station histories suggest that the early observations could have been positively biased, for example because of insufficient radiation protection. We investigate if independent support for warm summers in the early period can be obtained from other climate variables. Using stepwise multiple regression analysis we investigate nine potential predictor variables: six air circulation indices, precipitation, air pressure and cloud amount. Three of these variables - cloud amount (the most important one), meridional geostrophic wind, and air pressure - together explain 65% of the June-August temperature variance in the calibration period 1873-2000. Application of the regression relationship back to 1780 shows that the model is equally successful in predicting year-to-year temperature variability before 1873 as it is in the calibration period, whereas the low-frequency component is poorly reconstructed in the early period. This reduced skill is primarily due to poorer data quality of the predictor variables in the early period, in particular the cloud amount series. The observed decadal mean temperatures during 1780-1860 are found to be above the upper limit of a 95% confidence interval that accounts for uncertainties both in the regression relationship and in the cloud amount series. We conclude that the observed temperatures before around 1860 are, therefore, most likely positively biased. The size of this bias cannot be accurately determined from the evidence used here, but seems to be about 0.7-0.8°C for both stations. A comparison with long instrumental temperature series from central Europe suggests a slightly smaller bias (0.5-0.6°C). For more accurate assessment of the Stockholm and Uppsala temperatures, we recommend that extensive homogeneity testing of other long northern European temperature series are undertaken. © 2003 Royal Meteorological Society."
"8921339000;6603831835;","Simulation of wind profiles from a space-borne Doppler wind lidar",2003,"10.1256/003590003769682183","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0142184794&doi=10.1256%2f003590003769682183&partnerID=40&md5=e4ca0c2f71a0d98dc2c8a22229de6258","The importance of wind observations for meteorological analysis has been recognized for many years. The current global observing system lacks a uniform distribution of tropospheric wind measurements, especially in the tropics and southern hemisphere, and over the northern-hemisphere oceans. A Doppler wind lidar (DWL) mounted on a space-borne platform has the potential to provide a global three-dimensional coverage of wind data. The European Space Agency has decided to fly in 2007 a DWL on a polar-orbiting satellite platform as part of the Atmospheric Dynamics Mission, now called Aeolus. The proposed DWL is a non-scanning single-perspective instrument, operating in the ultraviolet part of the electromagnetic spectrum, providing profiles of line-of-sight (LOS) wind components from detected light backscattered from the illuminated atmospheric volume. The concept has been simulated and was used in observation-system simulation experiments to assess its potential impact on numerical weather prediction and climate processes. This paper describes the simulation of Aeolus LOS wind-component profiles and their expected quality in cloud-free and cloudy conditions."
"56241347800;8839231800;","Characteristic differences of rainfall and cloud-to-ground lightning activity over South Korea during the summer monsoon season",2003,"10.1175/1520-0493(2003)131<2312:CDORAC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242415380&doi=10.1175%2f1520-0493%282003%29131%3c2312%3aCDORAC%3e2.0.CO%3b2&partnerID=40&md5=37e9cc58f7b2ddc822564b449982f781","In this paper the characteristic variations of cloud-to-ground (CG) lightning and total precipitation during the Korean summer monsoon (June-August) season have been extensively analyzed for different climate regimes. The data used in this study consist of the monthly CG lightning flash count as detected by the lightning detection network installed at the Korean Meteorological Administration (KMA) and the monthly precipitation data from 23 meteorological observatories spread over the Korean peninsula for a period of 10 yr from 1988 to 1997. Temporal and spatial scales of 1 month and 102 km2, respectively, were considered to determine the seasonal values of rain yield or rain volume per CG flash (defined as the ratio of total precipitation to CG flash count over a common area). Seasonal values of rain yield have been compared with that of monthly values separately. The results of variation of the rain yield during the different months constituting the monsoon season are also presented. Results show that the variation of rain yield for the monsoon season closely resembles that of July indicating that July, rather than the other two monsoon months, dominates the overall monsoon pattern. The maximum values of rain yield are observed in the east coast of the Korean peninsula, particularly in the region east of Tae-back Mountain, with a mean value of 3 × 105 m3 fl 1 while the minimum value is seen in the west of Tae-back Mountain, with an average value of 8 × 104 m3 fl 1. The method for separating convective rain designed on broad heterogeneity similar to the Petersen and Rutledge method shows on average 82% of the total rainfall is convective in nature at the west coast stations, 53% is convective at the middle of the peninsula, and 46% is convective at the east coast stations. Maximum convective rain occurred at Kanghwa in the northwest, while the minimum was seen at Ulsan in the southeast. The correlation coefficient between the total precipitation and CG lightning during the summer monsoon season is 0.54, which is not very high since in most cases total precipitation persists longer than CG lightning. This may be due to the occasional development of mesoscale convective systems (MCSs), which produce light stratiform precipitation during their dissipation stage or might have been contaminated by the upslope precipitation or by nonlightning producing frontal precipitation. This low correlation coefficient could also be due to the episodic presence of warm rain convection or a ""low-echo centroid"" precipitation system."
"55182712000;6603850393;","Atmospheric circulation anomalies during episodes of enhanced and reduced convective cloudiness over Uruguay",2003,"10.1175/1520-0442(2003)016<3171:ACADEO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344552897&doi=10.1175%2f1520-0442%282003%29016%3c3171%3aACADEO%3e2.0.CO%3b2&partnerID=40&md5=d1d4b0cb8f5e35a84d6081aebda9ca04","Regional and large-scale circulation anomalies associated with periods of enhanced and reduced convective cloudiness over Uruguay are studied for austral spring and summer, when rainfall associated with deep convection is more frequent in this region. The analysis was performed at a submonthly timescale, considering that the essential nature of the mechanisms producing rainfall is not well captured by anomalies calculated on a monthly or seasonal basis in regions where precipitation is highly episodic. Periods of enhanced and reduced convective cloudiness over Uruguay are characterized by a marked dipolar structure in the outgoing longwave radiation anomaly field along eastern South America from 10° to 40°S, with the centers of the dipole located over the South Atlantic convergence zone (SACZ) and over a broad region including Uruguay, southern Brazil, and northeastern Argentina. This dipole, which corresponds to one of the key factors of climate dynamics in South America during spring and summer, seems to be part of a much larger wavelike quasi-barotropic structure that includes alternating centers of negative and positive geopotential height and temperature anomalies in the southern portion of the continent, and farther upstream in the southern Pacific. At the regional scale, periods of enhanced convection and rainfall over Uruguay are associated with the following features: a warm-core anticyclonic circulation anomaly in the middle and upper troposphere, centered on 34°S, 45°W, approximately: an intensified Chaco low in northwestern Argentina that favors a reinforced northwesterly flow of warm and moist air from the Amazon basin; and an anomalously strong subtropical jet along eastern South America. Periods with reduced convective cloudiness over Uruguay are characterized by circulation anomalies that are broadly opposite to those described before, although some significant asymmetries in their intensity are documented. No major differences were detected in the circulation anomaly patterns between spring and summer, although some changes in the wavelike structure associated to the dipole were found. Considering the extent of circulation anomalies described here for the austral summer semester, it seems plausible that they also characterize rainfall anomalies over a broader region in southeastern South America."
"6602996168;7003468747;6701333444;7202429440;35463545000;","Clear-sky infrared aerosol radiative forcing at the surface and the top of the atmosphere",2003,"10.1256/003590003769682110","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0142215997&doi=10.1256%2f003590003769682110&partnerID=40&md5=fecf9b2023381af65e367b04611f4adb","We study the aerosol radiative forcing at infrared (IR) wavelengths using data from the Aerosol Characterization Experiment, ACE-Asia, cruise of the National Oceanic and Atmospheric Administration research vessel Ronald H. Brown. The analyses apply to the daytime periods of clear-sky conditions for the area within the immediate vicinity of the ship. An optical model is derived from chemical measurements, lidar profiles, and visible-extinction measurements, which are used to estimate the IR aerosol optical thickness and the single-scattering albedo. The IR model results are compared to detailed Fourier transform interferometer-based IR aerosol forcing estimates, pyrgeometer-based IR downward fluxes, and to observations of the direct aerosol solar forcing. This combined approach attests to the self-consistency of the optical model, and allows us to derive quantities such as the IR forcing at the top of the atmosphere (TOA) and the IR optical thickness. The mean IR aerosol optical thickness at 10 μm is 0.08 and the single-scattering albedo is 0.55. The modelled IR aerosol surface forcing reaches 10 W m-2 during the cruise, which is a significant contribution compared to the total direct aerosol forcing. The surface IR aerosol radiative forcing is between 10 and 25% of the short-wave aerosol forcing. The IR aerosol forcing at the TOA can be up to 19% of the solar aerosol forcing. We show good agreement between TOA aerosol IR forcing derived from the model and from the CERES (Clouds and the Earth's Radiant Energy System) satellite data. Over the Sea of Japan, the average IR aerosol radiative forcing is 4.6 W m-2 at the surface, and 1.5 W m-2 at the TOA. The IR forcing efficiency at the TOA is a strong function of aerosol temperature (which is coupled to vertical structure) and changes between 10 and 18 W m-2 (per IR optical depth unit), while the surface IR forcing efficiency varies between 37 and 55 W m-2 (per IR optical depth unit)."
"6602098362;7102389805;","A hydrological definition of Indian Monsoon onset and withdrawal",2003,"10.1175/1520-0442(2003)016<3200a:AHDOIM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344121648&doi=10.1175%2f1520-0442%282003%29016%3c3200a%3aAHDOIM%3e2.0.CO%3b2&partnerID=40&md5=cf990da1ce1e460023bd6f53fe9551e0","A diagnostic criterion that retrospectively assesses the onset and withdrawal dates of the Indian monsoon is derived from variability in the large-scale hydrologic cycle. The method is proposed as an improved means with which to understand interannual variability in the monsoon transitions as compared to criteria that rely heavily on rainfall variability over limited spatial domains (e.g., individual Indian districts). The hydrologic cycle is chosen as a key physical basis for monitoring the monsoon due to the essential roles played by zonal and meridional gradients in water vapor, clouds, and rainfall in driving the large-scale monsoon circulation. Moreover, as rainfall is greater than evaporation in wet monsoonal areas, lateral transports of water vapor are required for the existence of monsoonal rains. To diagnose onset and withdrawal, vertically integrated moisture transport (VIMT) is therefore used instead of rainfall, which over the large scale is often poorly measured and modeled. In contrast to rainfall, VIMT is generally well modeled and observed, and its variability, particularly over the Arabian Sea, is substantial during both monsoon onset and withdrawal. An index, named the hydrologic onset and withdrawal index (HOWI), is thus formed from those regions, where VIMT variability is pronounced at the beginning and end of the monsoon season. The HOWI offers several advantages as the index is based on fields that are better modeled and measured than rainfall, and the index is indicative of the transition in the large-scale monsoon circulation rather than being highly sensitive to synoptic variability and the spatial complexity of the monsoon transitions. The HOWI is shown to be both robust to bogus monsoon onsets and reflective of the timing, rather than the spatial character, of the transitions. Analysis of interannual variability in monsoon onset and withdrawal dates based on the HOWI reveals robust associations that are weak and insignificant when assessed using other onset criteria. For example, the associations between total June-July-August-September (JJAS) rainfall and both monsoon onset and withdrawal are weak (correlations are weaker than -0.11) when onset dates from the Indian Meteorological Department (IMD) or other objective methods are considered. However, the HOWI criterion shows strong correlations between total JJAS rainfall and both onset (0.30) and withdrawal (-0.49). Thus, the length of the monsoon season is shown to be strongly related to its overall strength. In addition, while the correlation between IMD onset date and Niño-3 SST is insignificant, the correlation based on HOWI is 0.41. The associations between HOWI and both ENSO and the overall monsoon season exceed significance at the 99% confidence level. Moreover, the associations are shown to be robust to the scale of the region selected in compiling the HOWI. It is speculated that the influence of synoptic variability and the spatially variable nature of the monsoon transitions mask, in part, the existence of the climate associations that are revealed by the HOWI."
"6602887222;6701847229;57218357462;7003499456;7003748648;","Predictability and uncertainty in a regional climate model",2003,"10.1029/2002jd002810","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342268203&doi=10.1029%2f2002jd002810&partnerID=40&md5=357e7026c0832a150d699fd0c4e25900","The evaluation of the quality and usefulness of climate modeling systems is dependent upon an assessment of both the limited predictability of the climate system and the uncertainties stemming from model formulation. In this study a methodology is presented that is suited to assess the performance of a regional climate model (RCM), based on its ability to represent the natural interannual variability on monthly and seasonal timescales. The methodology involves carrying out multiyear ensemble simulations (to assess the predictability bounds within which the model can be evaluated against observations) and multiyear sensitivity experiments using different model formulations (to assess the model uncertainty). As an example application, experiments driven by assimilated lateral boundary conditions and sea surface temperatures from the ECMWF Reanalysis Project (ERA-15, 1979-1993) were conducted. While the ensemble experiment demonstrates that the predictability of the regional climate varies strongly between different seasons and regions, being weakest during the summer and over continental regions, important sensitivities of the modeling system to parameterization choices are uncovered. In particular, compensating mechanisms related to the long-term representation of the water cycle are revealed, in which summer dry and hot conditions at the surface, resulting from insufficient evaporation, can persist despite insufficient net solar radiation (a result of unrealistic cloud-radiative feedbacks). © 2003 by the American Geophysical Union."
"7201994547;56031450100;","Sensitivity of the Baltic Sea salinity to the freshwater supply",2003,"10.3354/cr024231","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242369774&doi=10.3354%2fcr024231&partnerID=40&md5=7d92137bc8954760a11d9289d55d41c8","The sensitivity of the Baltic Sea salinity to the freshwater supply is investigated using a 3-dimensional (3D) coupled sea-ice-ocean model. Today's climate is characterized by an average salinity of about 7.4 ‰ and a freshwater supply, including river runoff and net precipitation, of about 16 000 m3 s-1. As recent results of some regional climate models have suggested a significant increase in precipitation in the Baltic catchment area due to anthropogenic climate change, in this study the response of salinity in the Baltic Sea to changing freshwater inflow is investigated. Of special interest is the possibility of the Baltic Sea becoming a freshwater sea with 0‰ salinity in the future. Therefore, model simulations with modified river runoff and precipitation for 1902-1998 were performed. The model is forced with daily sea-level observations in the Kattegat, monthly basin-wide discharge data, and reconstructed atmospheric surface data. The reconstruction utilizes a statistical model to calculate daily sea-level pressure, and monthly surface-air temperature, dew-point temperature, precipitation, and cloud-cover fields. It is assumed that the Kattegat deepwater salinity of about 33‰ will not change regardless of the changed freshwater supply. In most of the experiments the final stratification is almost in a steady state after 100 yr. We found that even for a freshwater supply increased by 100% compared to 1902-1998 the Baltic Sea cannot be classified as a freshwater sea. A pronounced halocline still separates the upper and lower layers in the Baltic Proper, limiting the impact of direct wind mixing to the surface layer. A calculated phase diagram suggests that the relationship between freshwater supply and average salinity of the final steady state is non-linear. The results of the 3D model are in agreement with an analytical steady-state model assumed to work for freshwater changes smaller than 30%. The latter model was applied in scenarios for the average salinity of the Baltic Sea."
"6603568514;7004242319;23065650200;7102577095;","The sensitivity of radiative fluxes to parameterized cloud microphysics",2003,"10.1175/1520-0442(2003)016<2979:TSORFT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242349787&doi=10.1175%2f1520-0442%282003%29016%3c2979%3aTSORFT%3e2.0.CO%3b2&partnerID=40&md5=71dbb5cc9fbe85f98756c24a188bcbaa","The sensitivity of modeled radiative fluxes to the specification of cloud microphysical parameterizations of effective radius and fallout are investigated using a single-column model and measurements from the Atmospheric Radiation Measurement (ARM) Program. The single-column model was run with data for the 3-month period of June-August 2000 at the ARM Southern Great Plains site forced with operational numerical weather prediction data. Several different packages of cloud microphysical parameterizations were used in the single-column model. The temporal evolution of modeled cloud amount as well as surface radiative fluxes from a control run compare well with ARM measurements. Mean ice particle fall speeds varied significantly with respect to the assumed ice particle habit. As particle fall speeds increased, the overall cloud fraction, cloud height, and grid-averaged ice water path decreased. The outgoing longwave radiation (OLR) differs by up to 4 W m-2 over the range of fall speeds examined, while shortwave fluxes varied little as most of the changes in cloud properties occurred at times of minimal solar radiation. Model results indicate that surface and top-of-atmosphere radiative fluxes are sensitive to the scheme used to specify the ice particle effective radius. On the seasonal timescale this sensitivity is on the order of 4 W m-2 and on the daily timescale can be as large as 32 W m-2. A conclusive statement as to which microphysical scheme is performing best is not achievable until cloud microphysical measurements include an accurate representation of small ice particles. The modeled variance of the ice particle effective radius at any given height in the model is considerably smaller than that suggested by measurements. Model results indicate that this underestimation of the ice particle effective radius variance can alter the seasonal mean top-of-atmosphere radiative fluxes by up to 5 W m-2 and the mean longwave cooling rate by up to 0.2° K day-1 near the location of maximum cloud amount. These seemingly modest flux sensitivities may have important implications for numerical climate simulations. These numerical experiments and observational comparisons have provided valuable physical insight into ice cloud-radiation physics and also into the mechanisms through which contemporary cloud microphysical parameterizations interact with climate model radiation schemes. In particular, the results demonstrate the importance of the smaller ice particles and emphasize the critical role played by not only the average particle size and shape but also the width of the ice particle effective radius distribution about its mean. In fact, the results show that this variability in particle size can sometimes play a greater role in cloud-radiation interactions than the more obvious variations in cloud amount due to changes in ice particle fall speed."
"7003802133;","On the climatic impact of ocean circulation",2003,"10.1175/1520-0442(2003)016<2875:OTCIOO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141940655&doi=10.1175%2f1520-0442%282003%29016%3c2875%3aOTCIOO%3e2.0.CO%3b2&partnerID=40&md5=4b291a4330a5a11ec196a933e3b62ca8","Integrations of coupled climate models with mixed-layer and fixed-current ocean components are used to explore the climatic response to varying magnitudes of ocean circulation. Four mixed-layer ocean experiments without ocean heat transports are performed using two different atmosphere-land components-the new GFDL AM2 and the GFDL Manabe Climate Model (MCM)-and two different sea ice components, one dynamic and one thermodynamic. Both experiments employing the dynamic sea ice component develop unstable growth of sea ice while the experiments with a thermodynamic sea ice component develop very large but stable ice covers. The global cooling ranges from modest to extreme in the four experiments. Using the fixed-current climate model, a trio of 100-yr integrations are made with control currents from a GFDL R30 ocean simulation, same currents reduced by 50%, and same currents increased by 50%. This suite is performed with two coupled models again employing the two atmosphere-land components, AM2 and MCM, for a total of six experiments. Both models show a large sensitivity of the sea ice extent to the magnitude of currents with increased currents reducing the extent and warming the high latitudes. Low cloud cover also responds to circulation changes in both models but in the opposite sense. In the AM2-based model, low cloudiness decreases as ocean circulation increases, reinforcing the sea ice changes in reducing the planetary reflectivity, and warming the climate. This cloudiness change is associated with a reduction in lower-atmospheric stability over the ocean. Because the AM2-based model is able to simulate the observed seasonal low cloud-stability relationship and the changes in these quantities with altered ocean circulation are consistent with this relationship, the AM2 interpretation of the cloud changes is favored."
"57202754759;6602558284;","Polar amplification of climate change in coupled models",2003,"10.1007/s00382-003-0332-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0142137724&doi=10.1007%2fs00382-003-0332-6&partnerID=40&md5=cb9f18b1baeb63722c53de4d7e9bbef4","The Northern Hemisphere polar amplification of climate change is documented in models taking part in the Coupled Model Intercomparison Project and in the new version of the Community Climate System Model. In particular, the magnitude, spatial distribution, and seasonality of the surface warming in the Arctic is examined and compared among the models. The range of simulated polar warming in the Arctic is from 1.5 to 4.5 times the global mean warming. While ice-albedo feedback is likely to account for much of the polar amplification, the strength of the feedback depends on numerous physical processes and parametrizations which differ considerably among the models. Nonetheless, the mean sea-ice state in the control (or present) climate is found to influence both the magnitude and spatial distribution of the high-latitude warming in the models. In particular, the latitude of the maximum warming is correlated inversely and significantly with sea-ice extent in the control climate. Additionally, models with relatively thin Arctic ice cover in the control climate tend to have higher polar amplification. An intercomparison of model results also shows that increases in poleward ocean heat transport at high latitudes and increases in polar cloud cover are significantly correlated to amplified Arctic warming. This suggests that these changes in the climate state may modify polar amplification. No significant correlation is found between polar amplification and the control climate continental ice and snow cover."
"6602332696;6602831555;8913262100;7004194999;","Future development of contrail cover, optical depth, and radiative forcing: Impacts of increasing air traffic and climate change",2003,"10.1175/1520-0442(2003)016<2890:FDOCCO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0142010042&doi=10.1175%2f1520-0442%282003%29016%3c2890%3aFDOCCO%3e2.0.CO%3b2&partnerID=40&md5=9e1f9845c06891bf77e7239cb05cf813","The future development of contrails is investigated considering changes in air traffic and aircraft technology as well as climate change by means of a contrail parameterization developed for the ECHAM general circulation model. Time slice simulations show an increase in global annual mean contrail cover from 0.06% in 1992, to 0.14% in 2015, and to 0.22% in 2050. In the northern extratropics, the enhancement of contrail cover is mainly determined by the growth of aviation. In the Tropics, contrail cover is, additionally, highly affected by climate change. In order to quantify the effect of systematic errors in the model climate on contrail cover, offline diagnostic studies are also performed. These studies suggest an underestimation of global contrail cover in the ECHAM simulations by a factor of about 0.8-0.9. The effect of the bias in the model climate is strongest in tropical latitudes. The temporal development of the simulated contrail radiative forcing is most closely related to total contrail cover, although the mean optical depth is found to increase in a warmer climate. Our best estimate is an increase of global annual mean radiative forcing from 3.5 mW m-2 in 1992, to 9.4 mW m-2 in 2015, and to 14.8 mW m-2 in 2050. Uncertainties in contrail radiative forcing mainly arise from uncertainties in microphysical and optical properties such as particle shape, particle size, and optical depth."
"7406372329;56962915800;7407038982;8873843700;","A theory for the Indian Ocean dipole-zonal mode",2003,"10.1175/1520-0469(2003)060<2119:ATFTIO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141796252&doi=10.1175%2f1520-0469%282003%29060%3c2119%3aATFTIO%3e2.0.CO%3b2&partnerID=40&md5=722306ec87f36475df3b887bfc996b41","Four fundamental differences of air-sea interactions between the tropical Pacific and Indian Oceans are identified based on observational analyses and physical reasoning. The first difference is represented by the strong contrast of a zonal cloud-SST phase relationship between the warm and cool oceans. The in-phase cloud-SST relationship in the warm oceans leads to a strong negative feedback, while a significant phase difference in the cold tongue leads to a much weaker thermodynamic damping. The second difference arises from the reversal of the basic-state zonal wind and the tilting of the ocean thermocline, which leads to distinctive effects of ocean waves. The third difference lies in the existence of the Asian monsoon and its interaction with the adjacent oceans. The fourth difference is that the southeast Indian Ocean is a region where a positive atmosphere-ocean thermodynamic feedback exists in boreal summer. A conceptual coupled atmosphere-ocean model was constructed aimed to understand the origin of the Indian Ocean dipole-zonal mode (IODM). In the model, various positive and negative air-sea feedback processes were considered. Among them were the cloud-radiation-SST feedback, the evaporation-SST-wind feedback, the thermocline-SST feedback, and the monsoon-ocean feedback. Numerical results indicate that the IODM is a dynamically coupled atmosphere-ocean mode whose instability depends on the annual cycle of the basic state. It tends to develop rapidly in boreal summer but decay in boreal winter. As a result, the IODM has a distinctive evolution characteristic compared to the El Nin̄o. Sensitivity experiments suggest that the IODM is a weakly damped oscillator in the absence of external forcing, owing to a strong negative cloud-SST feedback and a deep mean thermocline in the equatorial Indian Ocean. A thermodynamic air-sea (TAS) feedback arises from the interaction between an anomalous atmospheric anticyclone and a cold SST anomaly (SSTA) off Sumatra. Because of its dependence on the basic-state wind, the nature of this TAS feedback is season dependent. A positive feedback occurs only in northern summer when the southeasterly flow is pronounced. It becomes a negative feedback in northern winter when the northwesterly wind is pronounced. The phase locking of the IODM can be, to a large extent, explained by this seasonal-dependent TAS feedback. The biennial tendency of the IODM is attributed to the monsoon-ocean feedback and the remote El Niño forcing that has a quasi-biennial component. In the presence of realistic Niño-3 SSTA forcing, the model is capable of simulating IODM events during the last 50 yr that are associated with the El Nin̄o, indicating that ENSO is one of triggering mechanisms. The failure of simulation of the 1961 and 1994 events suggests that other types of climate forcings in addition to the ENSO must play a role in triggering an IODM event."
"7102948268;7003633107;","Vertical dimensions of seasonal trends in the diurnal temperature range across the central United States",2003,"10.1029/2003GL017776","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0348108165&doi=10.1029%2f2003GL017776&partnerID=40&md5=cb12f2c1fa8013718544564ceae0465a","Many investigators have used near-surface air temperature measurements to document a downward global trend in the diurnal temperature range (DTR). In this paper, we use radiosonde-based tropospheric measurements to examine vertical dimensions in trends in the DTR over the central United States. We find declining trends in DTR only at 85 kPa and the surface in the high-sun season, with the absolute trend at 85 kPa being greater than the trend at the surface suggesting that the trend in DTR is far more than an urban artifact in the data. There are no significant trends in DTR from 70 kPa to 25 kPa in any season. These results suggest that DTR trends in the low troposphere are likely influenced by near-surface processes such as variations in cloudiness, vegetation, or precipitation but not dominated by urban effects."
"7103274591;7003480967;7004479957;7101755461;6507197212;57202951657;","Convective forcing in the intertropical convergence zone of the eastern Pacific",2003,"10.1175/1520-0469(2003)060<2064:CFITIC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141573102&doi=10.1175%2f1520-0469%282003%29060%3c2064%3aCFITIC%3e2.0.CO%3b2&partnerID=40&md5=251d3b19b5f0cc65c116994f6d82474b","One of the goals of the East Pacific Investigation of Climate, year 2001 process study (EPIC2001), was to understand the mechanisms controlling the forcing of deep atmospheric convection over the tropical eastern Pacific. An intensive study was made of convection in a 4° × 4° square centered on 10°N, 95°W in September and October of 2001. This is called the intertropical convergence zone (ITCZ study region because it encompasses the eastern Pacific intertropical convergence zone. Starting from an analysis of the theoretical possibilities and a plethora of dropsonde, in situ, radar, and satellite data, it is found that newly developing convection occurs where a deep layer of air (of order 1 km deep or deeper) is conditionally unstable with only weak convective inhibition. Shallower conditionally unstable layers are associated with numerous small clouds, but do not seem to produce deep convection. The occurrence of deep convection over the ITCZ study region is resumably related to the propensity of the environment to produce areas of weak convective inhibition over such a deep layer. Three theoretically possible factors control the formation of such convectively unstable areas: 1) the strength of the total surface heat (or moist entropy) fluxes; 2) the advection of moisture into the region; and 3) temperature anomalies caused by dry adiabatic ascent of the inhibition layer, which lies typically between 700 and 850 mb. The areal fraction covered by such instability is small even on highly convective days. In the tropical eastern Pacific, it is found that the total surface entropy flux is the most significant of these factors, with a warm layer in the 700-850-mb range, resulting presumably from subsidence, playing an important suppressive role in certain cases. These two factors account for approximately two-thirds of the variance in satellite infrared brightness temperature averaged over the study region. Moisture (or moist entropy) advection appears to be of less importance. Tropical disturbances such as easterly waves, Kelvin waves, and the Madden-Julian oscillation presumably control convection primarily via these two mechanisms during their passage through this region."
"7101936669;","Seasonal climate summary southern hemisphere (spring 2002): The El Niño reaches maturity and dry conditions dominate Australia",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346125296&partnerID=40&md5=92e7ce24a1d56dfb8cb6059ddff37555","Atmospheric and oceanic conditions in the southern hemisphere are reviewed for the 2002 austral spring season. Particular emphasis is given to the Australian and Pacific regions. The El Niño event that emerged in the equatorial Pacific Ocean during autumn and winter reached its peak late in the spring of 2002. Ocean surface and sub surface temperatures in the tropical Pacific remained well above normal throughout the period, driving changes in the overlying Walker circulation and hence modifying many atmospheric parameters, including cloudiness, winds and surface pressures. Teleconnections ensured that such changes induced remote impacts throughout the southern hemisphere. The El Niño event, its growth earlier in the year, the start of its decay late in spring as well as its broadscale modification of the southern hemisphere atmosphere, was highly consistent with theoretically expected behaviour. For Australia, widespread dry conditions dominated the country, with low cloud amounts and a southwards shift in the westerlies; both consistent with the impacts of an El Niño in the Pacific. The generally low rainfall during spring was further exacerbated by very high maximum temperatures and hence greatly increased evaporation, consolidating the event as one of the worst Australian droughts in recorded history. Over the Antarctic, the springtime ozone hole expanded to its smallest size since 1988, reaching only 19 million square kilometres before splitting into two regions."
"6602244257;56744278700;","Sensitivity of the atmospheric lapse rate to solar cloud absorption in a radiative-convective model",2003,"10.1029/2002jd002966","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342268706&doi=10.1029%2f2002jd002966&partnerID=40&md5=3f37014fba7c9f64a42dfc0fea4880c3","Previous radiative-convective model studies of the radiative forcing due to absorbing aerosols such as soot and dust have revealed a strong dependence on the vertical distribution of the absorbers. In this study, we extend this concept to absorption in cloud layers, using a one-dimensional radiative-convective model employing high, middle, and low cloud representations to investigate the response of the surface temperature and atmospheric lapse rate to increases in visible cloud absorption. The visible single-scattering albedo (ssa) of the clouds is prescribed, ranging from 1.0 to 0.6, where 0.99 is the minimum that would be expected from the presence of absorbing aerosols within the cloud drops on the basis of recent Monterey Area Ship Track (MAST) Experiment case studies. Simulations are performed with respect to both a constant cloud optical depth and an increasing cloud optical depth and as a function of cloud height. We find that increases in solar cloud absorption tend to warm the troposphere and surface and stabilize the atmosphere, while increases in cloud optical depth cool the troposphere and surface and slightly stabilize the atmosphere between the low cloud top and surface because of the increase in surface cooling. In the absence of considerations involving microphysical or cloud-climate feedbacks, we find that two conditions are required to yield an inversion from a solar cloud absorption perturbation: (1) The solar absorption perturbation must be included throughout the tropospheric clouds column, distributing the solar heating to higher altitudes, and (2) the ssa of the clouds must be ≤0.6, which is an unrealistically low value. The implication is that there is very little possibility of significant stabilization of the global mean atmosphere due to perturbation of cloud properties given current ssa values. Copyright 2003 by the American Geophysical Union."
"7203001286;7006084942;","Simulating the impact of sea salt on global nss sulphate aerosols",2003,"10.1029/2002jd003181","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342289969&doi=10.1029%2f2002jd003181&partnerID=40&md5=ec8d35d60aabcd15eda5b2c5ec941a5c","The Canadian Aerosol Module coupled with the Canadian third generation Global Climate Model was used to simulate the global distributions of size-segregated sea salt and sulphate aerosols of both anthropogenic and natural origins in the atmosphere. A sectional model of 12 size bins was used to treat the size distribution of sea salt and sulphate, which is assumed to be internally mixed in each size bin. The spatial and temporal distributions predicted by the model compare reasonably well with observations. The mixed aerosol simulations yield number and volume size distributions in the marine boundary layer (MBL) comparable with observations. Sea salt particles redistribute the mass and number distributions of sulphate aerosols by serving as a quenching agent to nucleation and as an additional surface area for condensation and by changing the cloud properties in the MBL. By differential simulations of global sea salt and sulphate it is found that the presence of sea salt increases the mass mean diameter of sulphate aerosols by up to a factor of 2 over the MBL with high sea salt concentrations and reduces the global sulphate aerosol mass in the surface MBL layer from 5 to 75% depending on the sea salt distributions. The high impacts are in the midlatitudes of both Northern and Southern Hemispheres with a minimum in the equatorial regions. In the polluted anthropogenic regions of North Pacific and Atlantic, sea salt reduces the sulphate concentration from 10 to 30%. The peak reductions of 50-75% occur in the roaring 40s of the Southern Hemisphere in spring and fall. The impact of sea salt on the annual global mass and number loading is estimated to be 9.13 and 0.76%, respectively. A reduction of 20-60% in the marine cloud droplet number concentrations (CDNC) was predicted because of the presence of sea salt, with greatest reductions in the roaring 40s south (40-70%) and in the midlatitude north (20-40%) where the sea salt concentrations were high. Along the equatorial regions some enhancement of total CDNC was simulated because of the presence of sea salt aerosols. Copyright 2003 by the American Geophysical Union."
"55886067800;7402883211;7005793536;56230578500;7201438966;26667390100;8918197800;6507472270;6506087749;8551312700;6602296992;6508190640;6603034566;36789199700;","Actinic flux determination from measurements of irradiance",2003,"10.1029/2002jd003236","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342268694&doi=10.1029%2f2002jd003236&partnerID=40&md5=b496c796240df03be883fe2a47772345","The actinic flux describes the number of photons incident at a point, while the irradiance describes the radiant energy crossing a surface. An algorithm for conversion of irradiance to downwelling actinic flux has been developed and tested. The algorithm uses a simple method to distinguish between a cloudy and a cloudless sky. It is necessary to separate cloudy and cloudless situations, as the irradiance to actinic flux conversion depends on the radiance field which is rather different for cloudy and cloudless skies. Surface UV irradiance and downwelling actinic flux spectra were measured at five European locations which were representative of different climates. A total of 9015 synchronized actinic flux and irradiance spectra were available to test the proposed algorithm. The measured irradiance spectra were used to estimate downwelling actinic flux spectra. The estimated actinic flux spectra were compared with the measured actinic flux spectra for all cloud and aerosol situations encountered, a wide range of solar zenith angles, and surface conditions. The average ratio of the reproduced to measured downwelling actinic flux is 1.021 ± 0.085 in the UV-B and 1.015 ± 0.105 in the UV-A. In general, the performance of the algorithm is better at smaller solar zenith angles. Copyright 2003 by the American Geophysical Union."
"7006359574;7007087267;7006057137;57200319386;","Isotopic fractionation of water during evaporation",2003,"10.1029/2003jd003597","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342311221&doi=10.1029%2f2003jd003597&partnerID=40&md5=73181e10d54a7cff7a6ed62b8f034d2c","Variations in the isotopic content (18O/16O and D/H ratios) of water in the natural environment provide a valuable tracer of the present-day global hydrologic cycle and a record of the climate over at least 400,000 years that is preserved in glacial ice. The interpretation of observed isotopic ratios in water vapor, rain, snow, and ice depends on our understanding of the processes (mainly phase changes) that produce isotopic fractionation. Whereas equilibrium isotopic fractionation is well understood, kinetic effects, or diffusion-controlled fractionation, has a limited experimental foundation. Kinetic effects are significant during evaporation into unsaturated air and during condensation to form ice from vapor. Kinetic effects are also thought to control the deuterium excess (d = δD - 8δ18O) of precipitation. We describe experiments to observe kinetic effects associated with evaporation. Analysis of our own and previous experiments shows that surface cooling of the liquid is a crucial variable affecting fractionation from evaporating water that has not been properly considered before. Including the effects of evaporative surface cooling reconciles observed D/H fractionation with kinetic theory and removes the need to invoke an unusual size for the HDO molecule. Thus the isotopic molecular diffusivity ratios are D(H218O)/D(H216O) = 0.9691 and D(HD16O)/D(H216O) = 0.9839. Implications of this work for representation of kinetic fractionation in global circulation models and cloud physics models are briefly discussed. Copyright 2003 by the American Geophysical Union."
"7103246957;7401813827;6701552501;7003994238;7601318782;7004540083;","Intercomparison of water and energy budgets for five Mississippi subbasins between ECMWF reanalysis (ERA-40) and NASA Data Assimilation Office fvGCM for 1990-1999",2003,"10.1029/2002jd003127","https://www.scopus.com/inward/record.uri?eid=2-s2.0-19244382898&doi=10.1029%2f2002jd003127&partnerID=40&md5=27c50ea6afa8ce0465cace629d377e25","Using monthly means for 1990-1999, we assess the systematic biases in temperature and humidity and the surface energy and water budgets of both European Centre for Medium-Range Weather Forecasts (ECMWF) 40-year reanalysis (ERA-40) and the of the NASA Data Assimilation Office atmospheric finite-volume general circulation model (fvGCM) for five Mississippi subbasins. We compare ERA-40 and the fvGCM with basin averages of surface observations of temperature, humidity and precipitation, the river basin estimates for the hydrological balance from Maurer et al. [2002], and the International Satellite Cloud Climatology Project (ISCCP) retrieved skin temperature and surface radiation fluxes. We show the role of the soil water analysis in ERA-40, which generally supplies water in summer and removes it in winter and spring. The ERA-40 snow analysis increments are a significant contribution to the (smaller) frozen water budget. Compared with National Climate Data Center (NCDC) observations of screen temperature, ERA-40 generally has a relatively small (≤1 K) positive temperature bias in all seasons for the Mississippi basins, while the fvGCM has a large cold bias in temperature in winter. The ISCCP skin temperature estimate is generally high in winter and a little low in summer, compared to ERA-40 and the NCDC screen level temperature. For the western basins, summer precipitation is high in the fvGCM, while for the eastern basins it is high in ERA-40 (in 12-24 hour forecasts after spin-up). Summer evaporation is higher in the fvGCM than in ERA-40, while winter evaporation has a high bias in ERA-40, leading to a corresponding high bias in specific humidity. Net shortwave radiation probably has a high bias in the fvGCM in summer. The seasonal cycle of incoming shortwave is much flatter in ERA-40 than the ISCCP data, suggesting that the reanalysis may have too much reflective cloud in summer and too little in the cooler seasons. The temperature biases at the surface in both the fvGCM and the ISCCP data clearly have a negative impact on the surface long-wave radiation fluxes, although the bias in the net long-wave flux is rather less. Copyright 2003 by the American Geophysical Union."
"6603139566;7005256983;","Modulation of the Great Plains low-level jet and moisture transports by orography and large-scale circulations",2003,"10.1029/2002jd003005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342289983&doi=10.1029%2f2002jd003005&partnerID=40&md5=5c33dfcf899772026b8c17b75968acd2","This paper describes orographic processes that modulate the Great Plains low-level jet (LLJ) and related hydrology of the Mississippi River basin. Mechanical flow deflection by the Rocky Mountains is diagnosed in 50 years of monthly averaged National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) Reanalysis fields and in a series of integrations using a primitive equation version of the Utah Global Model (UGM). Although the mountain profiles are fixed over periods of short-to medium-range climate changes, their influence on the LLJ is not stationary because evolving ambient flows produce changing LLJ responses. Ensembles of medium-range forecasts are made for the 1993 U.S. floods and for the 1988 U.S. drought. The forecasts distinguish some of the observed precipitation differences between these years, but the magnitude of the differences is underestimated. Seasonal and longer-term changes of the ambient flow occur on large scales, while the response of the LLJ occurs on smaller scales that may promote cloud generation and precipitation. Month-long simulations with monthly averaged conditions suggest that the Great Plains LLJ is a component of the large-scale circulation associated with the topography of the western United States. Orography thus provides a scale transfer mechanism that focuses global-scale features into the regional-scale responses. These are relevant to precipitation distribution and to moisture budgets of the larger individual river basins comprising the GCIP domain. A theoretical interpretation of the large-scale, mechanical influence of orography on surrounding low-level circulations is proposed. Copyright 2003 by the American Geophysical Union."
"55896920900;","Introduction to Special Section: An experimental study of the aerosol indirect effect for validation of climate model parameterizations",2003,"10.1029/2003jd003849","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342269859&doi=10.1029%2f2003jd003849&partnerID=40&md5=3f45c66b45fb7ec2dcafe52755fb6c8e",[No abstract available]
"57214899685;57203053317;","Sensitivity of single column model simulations of Arctic springtime clouds to different cloud cover and mixed phase cloud parameterizations",2003,"10.1029/2002jd003136","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342269950&doi=10.1029%2f2002jd003136&partnerID=40&md5=57dbf5041ddcf15788a5e2540ca55e9c","The single column model of the Canadian Centre for Climate Modeling and Analysis (CCCma) climate model is used to simulate Arctic spring cloud properties observed during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment. The model is driven by the rawinsonde observations constrained European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis data. Five cloud parameterizations, including three statistical and two explicit schemes, are compared and the sensitivity to mixed phase cloud parameterizations is studied. Using the original mixed phase cloud parameterization of the model, the statistical cloud schemes produce more cloud cover, cloud water, and precipitation than the explicit schemes and in general agree better with observations. The mixed phase cloud parameterization from ECMWF decreases the initial saturation specific humidity threshold of cloud formation. This improves the simulated cloud cover in the explicit schemes and reduces the difference between the different cloud schemes. On the other hand, because the ECMWF mixed phase cloud scheme does not consider the Bergeron-Findeisen process, less ice crystals are formed. This leads to a higher liquid water path and less precipitation than what was observed. Copyright 2003 by the American Geophysical Union."
"6701596624;55896920900;","An observational study of drizzle formation in stratocumulus clouds for general circulation model (GCM) parameterizations",2003,"10.1029/2002jd002679","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342269923&doi=10.1029%2f2002jd002679&partnerID=40&md5=93020ec07e62c9d0588982e8f33fc695","Climate model parameterization of precipitation formation in boundary layer stratocumulus clouds is a challenge that needs to be carefully addressed for simulations of the aerosol impact on precipitation and on cloud life time and extent, the so-called second indirect effect of aerosol on climate. Existing schemes are generally tuned against global observations of the liquid water path, as very few in situ observations are available for their validation. This issue is addressed here with data collected during the second Aerosol Characterization Experiment. The methodology is different from previous experimental studies in the sense that each case study is first analyzed for retrieving properties that are representative of the observed cloud system as a whole, such as the cloud system geometrical thickness, droplet concentration, precipitation flux, etc. Special attention is given to the characterization of the droplet number concentration by deriving a value that is representative of the aerosol activation process instead of the mean value over the cloud system. The analysis then focuses on the variability of these cloud system values for eight case studies with different aerosol backgrounds. The data set reveals that precipitation forms when the maximum mean volume droplet radius in the cloud layer reaches values >10 μm, the same critical value as previously used in cloud resolving models. This maximum radius can be predicted with an adiabatic diagnostic on the basis of cloud geometrical thickness and droplet number concentration. The measured reduction rate of drizzle water content by precipitation is also compared to predictions of auto-conversion and accretion production rates derived from existing bulk parameterizations initialized with the measured values of cloud droplet and drizzle water content. The good agreement with the parameterizations suggests that the cloud layer reaches a nearly steady state characterized by a balance between the production and reduction rates of cloud and drizzle water content. Finally, it is shown that the cloud system precipitation rate can be expressed as a power law of cloud geometrical thickness and cloud droplet number concentration, hence providing a simple large-scale parameterization of the precipitation process in boundary layer clouds. Copyright 2003 by the American Geophysical Union."
"55896920900;6701596624;56706602500;","Cloud microphysical and radiative properties for parameterization and satellite monitoring of the indirect effect of aerosol on climate",2003,"10.1029/2002jd002682","https://www.scopus.com/inward/record.uri?eid=2-s2.0-19244377495&doi=10.1029%2f2002jd002682&partnerID=40&md5=c4aab2f5e8e2787127adcbe1a888f78d","The spatial variability of the microphysical fields in stratocumulus clouds is documented in this paper with statistics of droplet number concentration, droplet mean volume radius, and liquid water content for eight cases of the second Aerosol Characterization Experiment. Statistics are calculated in five sublayers, from cloud base to cloud top, and they are utilized for deriving estimates of cloud optical thickness and liquid water path, by assuming either random or maximum overlap. The resulting in situ frequency distributions of optical thickness and liquid water path are validated against distributions of these two parameters retrieved from independent remote sensing measurements of cloud radiances. They are also used for testing parameterizations of optical thickness based on liquid water path and either the droplet effective radius or the cloud droplet number concentration. This unique data set of extensive, concomitant, and independent measurements of cloud microphysical and radiative properties is finally used for assessing the detectability of the aerosol indirect effect through examination of the correlation between cloud optical thickness and droplet effective radius. If only cases of comparable values of geometrical thickness are considered, the correlation between optical thickness and effective radius is negative, as anticipated by Twomey [1977]. However, if the most polluted cases are also accounted for, the trend suggests a positive correlation. In fact, the most polluted cloud systems sampled during ACE-2 were slightly drier, hence thinner, than the marine and intermediate cases, hence producing a positive correlation between optical thickness and droplet effective radius. This study demonstrates that the monitoring of the aerosol indirect effect with satellite observations requires an independent retrieval of the liquid water path together with the cloud optical thickness and droplet effective radius. Copyright 2003 by the American Geophysical Union."
"6603312650;7006646563;7006667679;6506904135;8760271700;7005650796;6603829269;7005376539;","Multisensor analysis of integrated atmospheric water vapor over Canada and Alaska",2003,"10.1029/2002jd002721","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342269824&doi=10.1029%2f2002jd002721&partnerID=40&md5=84c5a35aa4edc1f636027e236a500a87","Atmospheric water vapor is a key parameter for the analysis of climatic systems (greenhouse gas effect), in particular over high latitudes where water vapor displays an important seasonal variability. The sparse spatial and temporal sampling of atmospheric water vapor observations across Canada needs to be improved. A series of instruments and methods including a 940-nm solar absorption band radiometer (R) and radiosonde (S) analysis from a numerical weather prediction model and a ground-based bi-frequency Global Positioning System (GPS) were used to evaluate the integrated atmospheric water vapor (IWV) at various sites in Canada and Alaska from a multiyear database. The IWV-R measurements were collected within the framework of the North American Sun Radiometry network (AERONET/AEROCAN). Intercomparisons between [IWV-GPS and IWV-S], [IWV-R and IWV-GPS], and [IWV-R and IWV-S] show root mean square (RMS) differences of 1.8, 1.9, and 2.2 kg m-2, respectively. GPS meteorology appears to be the easiest approach to calibrate the solar radiometer water vapor band owing to its flexibility, and it allows us to overcome the Sun radiometry limitation in high-latitude areas like the Arctic. The sensitivity of the GPS retrieval to various parameters like GPS satellite constellation and meteorological data are discussed. The classical linear relationship between the surface temperature and the integrated weighted mean temperature profile needed for IWV-GPS retrieval may be significantly different for Arctic air masses compared with midlatitude air masses in the case of tropospheric temperature profile inversion. An ever-expanding multiyear (1994-2001) North American summer water vapor climatology, derived from AERONET/Canadian Sun Radiometer Network, is presented and analyzed, showing a mean value of 19.8 ± 6.1 kg m-2 and variations from 17 kg m-2 in Alaska to 23 kg m-2 in southeastern Canada. The results in Bonanza Creek, Alaska, show significant interannual variations with a peak in 1997, which may be linked to an EI Niño event that occurred in the same year. Such a database may also be useful for climate model validation as shown for the Canadian Global Environmental Model (RMS difference of 3.4 kg m-2). In the end we show that, even if data are selected only for cloud-free atmospheres, there are no significant differences as compared with radiosonde climatology at Canadian Northwestern sites (≤3% relatively to Bonanza Creek summer mean value). Copyright 2003 by the American Geophysical Union."
"6603642315;7003371535;7003656857;","Size distributions and dynamical properties of shallow cumulus clouds from aircraft observations and satellite data",2003,"10.1175/1520-0469(2003)060<1895:SDADPO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141459890&doi=10.1175%2f1520-0469%282003%29060%3c1895%3aSDADPO%3e2.0.CO%3b2&partnerID=40&md5=e5dc8dc08fae7fdd64f035109a6138a9","In this paper aircraft observations of shallow cumulus over Florida during the Small Cumulus Microphysics Study (SCMS) are analyzed. Size distributions of cloud fraction, mass flux, and in-cloud buoyancy flux are derived. These distributions provide information on the specific contribution of clouds with a certain horizontal size and reveal, for example, which size has the largest effect on cloud fraction or vertical transport. The analysis of four flights shows that the mass flux and buoyancy flux are dominated by intermediate-sized clouds (horizontal dimension of about 1 km). The cloud fraction, on the other hand, is found to be dominated by the smallest clouds observed. These clouds are additionally found to have a negative contribution to the mass flux, yet a positive contribution to the buoyancy flux. About 200 flight intersections of cumuli with horizontal sizes larger than 500 m are used to obtain average horizontal cross-section profiles of vertical velocity, liquid water content, liquid water potential temperature, and virtual potential temperature. A thin shell of descending air just around the cloud emerges as a conspicuous feature. Evidence is found that the descent is mainly caused by evaporative cooling, which results from lateral mixing at the cloud boundary. A Landsat satellite image near the flight region is analyzed to compare the cloud size distributions with the aircraft data. The cloud cover in the image appears to be dominated by much larger clouds than the aircraft observations indicated. To account for the different measurement methodology (two-dimensional versus one-dimensional) an equation with which one can predict the cloud size distribution that results from performing line measurements in a prescribed two-dimensional cumulus field is derived. The equation reveals that the aircraft cloud size distributions are always biased toward smaller cloud sizes. This effect is nevertheless not enough to reconcile the aircraft and satellite data, presumably because the analysis neglects the variability of clouds in the vertical direction."
"25941200000;7202899330;6602209040;7202048299;6603276395;6603239832;7006204393;35412628400;56363371300;6701562494;57193920163;7402215419;6603892183;6603396333;6603752490;8636990400;56493740900;7410070663;6602513845;24322005900;6602356307;6701511324;56744278700;7005496842;7003683808;7202496599;7403544649;6602276370;7404240633;7005174340;7202962414;8380111100;","Assessing 1D atmospheric solar radiative transfer models: Interpretation and handling of unresolved clouds",2003,"10.1175/1520-0442(2003)016<2676:ADASRT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038792524&doi=10.1175%2f1520-0442%282003%29016%3c2676%3aADASRT%3e2.0.CO%3b2&partnerID=40&md5=6620484981e6a32792650a7acc12f2e4","The primary purpose of this study is to assess the performance of 1D solar radiative transfer codes that are used currently both for research and in weather and climate models. Emphasis is on interpretation and handling of unresolved clouds. Answers are sought to the following questions: (i) How well do 1D solar codes interpret and handle columns of information pertaining to partly cloudy atmospheres? (ii) Regardless of the adequacy of their assumptions about unresolved clouds, do 1D solar codes perform as intended? One clear-sky and two plane-parallel, homogeneous (PPH) overcast cloud cases serve to elucidate 1D model differences due to varying treatments of gaseous transmittances, cloud optical properties, and basic radiative transfer. The remaining four cases involve 3D distributions of cloud water and water vapor as simulated by cloud-resolving models. Results for 25 1D codes, which included two line-by-line (LBL) models (clear and overcast only) and four 3D Monte Carlo (MC) photon transport algorithms, were submitted by 22 groups. Benchmark, domain-averaged irradiance profiles were computed by the MC codes. For the clear and overcast cases, all MC estimates of top-of-atmosphere albedo, atmospheric absorptance, and surface absorptance agree with one of the LBL codes to within ±2%. Most 1D codes underestimate atmospheric absorptance by typically 15-25 W m 2 at overhead sun for the standard tropical atmosphere regardless of clouds. Depending on assumptions about unresolved clouds, the 1D codes were partitioned into four genres: (i) horizontal variability, (ii) exact overlap of PPH clouds, (iii) maximum/random overlap of PPH clouds, and (iv) random overlap of PPH clouds. A single MC code was used to establish conditional benchmarks applicable to each genre, and all MC codes were used to establish the full 3D benchmarks. There is a tendency for 1D codes to cluster near their respective conditional benchmarks, though intragenre variances typically exceed those for the clear and overcast cases. The majority of 1D codes fall into the extreme category of maximum/random overlap of PPH clouds and thus generally disagree with full 3D benchmark values. Given the fairly limited scope of these tests and the inability of any one code to perform extremely well for all cases begs the question that a paradigm shift is due for modeling 1D solar fluxes for cloudy atmospheres."
"56031450100;7201994547;","Modeling decadal variability of the Baltic Sea: 1. Reconstructing atmospheric surface data for the period 1902-1998",2003,"10.1029/2003jc001797","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344552821&doi=10.1029%2f2003jc001797&partnerID=40&md5=606c15d8599718e48c86f906be61ca00","A statistical model is developed to reconstruct atmospheric surface data for the period 1902-1998 to force a coupled sea ice-ocean model of the Baltic Sea. As the response timescale of the Baltic Sea on freshwater inflow is of the order of 30-40 years, climate relevant model studies should cover at least century-long simulations. Such an observational atmospheric data set is not available yet. We devised a statistical model using a ""redundancy analysis"" to reconstruct daily sea level pressure (SLP) and monthly surface air temperature (SAT), dew-point temperature, precipitation, and cloud cover of the Baltic. The predictor fields are daily SLP at 19 stations and monthly coarse gridded SAT and precipitation available for the period 1902 to 1998. The second input is a gridded atmospheric data set, with high resolution in space and time, based on synoptic stations, which is available for the period 1970-2001. Spatial patterns are selected by maximizing predictand variance during the ""learning"" period 1980-1998. The remainder period 1970-1979 is used for validation. We found the highest skill of the statistical model for SLP and the lowest skill for cloud cover. For wintertime the dominant modes of variability on the interannual to interdecadal timescales of the reconstruction are discussed. It is shown that the wintertime variability of SLP, SAT, and precipitation is related to well-known atmospheric patterns of the Northern Hemisphere: the North Atlantic Oscillation, the Scandinavia patterns, the East Atlantic/West Russia pattern, and the Barents Sea Oscillation."
"23502460300;57196612909;7202326662;6602676167;6506886754;7102508467;6507885759;7005043888;","Performance of operational radiosonde humidity sensors in direct comparison with a chilled mirror dew-point hygrometer and its climate implication",2003,"10.1029/2003GL016985","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0345393159&doi=10.1029%2f2003GL016985&partnerID=40&md5=6169dc371daf4cac03143711f7af5858","This study evaluates performance of humidity sensors in two widely used operational radiosondes, Vaisala and Sippican (formally VIZ), in comparison with a research quality, and potentially more accurate, chilled mirror dew-point hygrometer named ""Snow White"". A research radiosonde system carrying the Snow White (SW) hygrometer was deployed in the Oklahoma panhandle and at Dodge City, KS during the International H2O Project (IHOP02). A total of sixteen sondes were launched with either Vaisala RS80 or Sippican VIZ-B2 radiosondes on the same balloons. Comparisons of humidity data from the SW with Vaisala and Sippican data show that (a) Vaisala RS80-H agrees with the SW very well in the middle and lower troposphere, but has dry biases in the upper troposphere (UT), (b) Sippican carbon hygristor (CH) has time-lag errors throughout the troposphere and fails to respond to humidity changes in the UT, sometimes even in the middle troposphere, and (c) the SW can detect cirrus clouds near the tropopause and possibly estimate their ice water content (IWC). The failure of CH in the UT results in significant and artificial humidity shifts in radiosonde climate records at stations where a transition from VIZ to Vaisala radiosondes has occurred."
"57203053317;6603452105;","Comparing continental and oceanic cloud susceptibilities to aerosols",2003,"10.1029/2003GL017828","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242368920&doi=10.1029%2f2003GL017828&partnerID=40&md5=d7cd969b95e13a4b5480384625c5074b","A common practice in remote sensing studies of the aerosol indirect effect is to consider the correlation between the droplet effective radius and the aerosol index. However, this correlation is not unique as the relationship depends also on the liquid water path. Moreover, it differs for oceanic and continental clouds because clouds over land generally have higher cloud bases, are thinner and have a higher average cloud droplet number concentration for a given aerosol index than marine clouds. Only when using aerosol number concentration at cloud base instead of aerosol index and using an effective radius representative for the whole cloud rather than just at cloud top, do the defined susceptibilities of oceanic and continental clouds obtained from ECHAM4 climate model simulations agree within the standard errors. This has important consequences for properly interpreting the magnitude of the anthropogenic indirect aerosol effect on climate."
"7005890514;51360903200;","Climate sensitivity and climate state",2003,"10.1007/s00382-003-0323-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038407006&doi=10.1007%2fs00382-003-0323-7&partnerID=40&md5=39b828699c563d95bdeef85bb88879ee","The effective climate feedback/sensitivity, including its components, is a robust first order feature of the Canadian Centre for Climate Modelling and Analysis (CCCma) coupled global climate model (GCM) and presumably of the climate system. Feedback/sensitivity characterizes the surface air temperature response to changes in radiative forcing and is constant, to first order, independent of the nature, history, and magnitude of the forcing and of the changing climate state. This ""constancy"" can only be approximate, however, and modest second order changes of 10-20% are found in stabilization simulations in which the forcing, based on the IS92a scenario, is fixed (stabilized) at year 2050 and 2100 values and the system is integrated for an additional 1000 years toward a new equilibrium. Both positive and negative feedback mechanisms tend to strengthen, with the balance tilted toward stronger negative feedback and hence weaker climate sensitivity, as the system evolves and warms. Some feedback mechanisms weaken locally, however, and an example of such is the ice/snow albedo feedback which is less effective in areas of the Northern Hemisphere where ice/snow has retreated. Changes in the geographical distribution of the feedbacks are modest and weakening feedback in one region is often counteracted by strengthening feedback in other regions so that global and zonal values do not reflect the dominance of a particular mechanism or region but rather the residual of changes in different components and regions. The overall 10-20% strengthening of the negative feedback (decrease in climate sensitivity) in the CCCma model contrasts with a weakening of negative feedback (increase in climate sensitivity) of over 20% in the Hadley Centre model under similar conditions. The different behaviour in the two models is due primarily to solar cloud feedback with a strengthening of the negative solar cloud feedback in the CCCma model contrasting with a weakening of it in the Hadley Centre model. The importance of processes which determine cloud properties and distribution is again manifest both in determining first order climate feedback/sensitivity and also in determining its second order variation with climate state."
"6602501796;","Diagnostic study on vertical structure of tropical precipitating cloud systems using lower atmospheric wind profiler",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749357804&partnerID=40&md5=02f8a18d5336f10972c42129c3a0882d","Temporal variations of vertical structure of precipitating clouds in tropical India have been studied based on the observations of 1.357 GHz lower atmospheric wind profiler (LAWP) at Gadanki. In the presence of precipitating clouds, backscattering from hydrometeors is dominant and the vertically pointing LAWP measures the backscattered energy and the vertical velocities of the hydrometeors directly overhead. These observations yield time-altitude cross-sections of equivalent reflectivity, Doppler velocity and spectral width that illustrate the evolution of precipitating cloud systems. The vertical structure of these three parameters has been used to classify the precipitating cloud systems into three types: convective, transition and stratiform. Diurnal and seasonal variations of the occurrence of precipitating cloud systems show that the precipitation primarily occurs in the afternoon and also the convective and transition clouds are most frequent in the southwest monsoon, while the occurrence of stratiform clouds is predominant in the north-east monsoon. Gadanki-LAWP provides means for the development of climatology of tropical precipitating cloud systems. Such climatology is needed to specify diabatic heating rates in large-scale numerical weather prediction and climate models."
"57034458200;7403566096;7402270607;","A numerical study of early summer regional climate and weather over LSA-East. Part I: Model implementation and verification",2003,"10.1175//2572.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141571567&doi=10.1175%2f%2f2572.1&partnerID=40&md5=f9965dfc0f2b6e0f4bb89a77c386ef76","The Pennsylvania State University-NCAR Mesoscale Model (MM5) and a simplified simple biosphere (SSiB) scheme are modified and then coupled to study various regional climate and weather problems. These modifications include correcting the moisture and cloud hydrometeor fields to ensure the mass conservation; incorporating the effects of dissipative heating to ensure total energy conservation; decoupling soil and vegetation types in specifying various surface parameters; and eliminating the shortwave radiation reaching the surface at points where deep convection occurs. A 30-day integration of June 1998 over the Midwest states was used to examine the model's capability in capturing the observed wet regional climate and the passage of several mesoscale weather events. It is found that the coupled model reproduces the distribution and magnitude of monthly accumulated precipitation, the time series of area-integrated precipitation, surface pressures, and diurnal changes in surface temperatures, lowlevel winds and precipitation, as well as the evolution of precipitation systems across the central United States. In particular, the model reproduces well many daily weather events, including the distribution and intensity of low-level temperature and pressure perturbations and precipitation, even up to a month. The results suggest that the daily temperature, clouds, and precipitation events from the weekly to monthly scales, as well as their associated regional climate phenomena, could be reasonably simulated if the surface, boundary layer, radiation, and convective processes are realistically parameterized, and the large-scale forcing could be reasonably provided by general circulation models."
"7202772927;7006423931;7006957668;7202400272;7004160106;","A cumulus parameterization workshop",2003,"10.1175/BAMS-84-8-1055","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042913247&doi=10.1175%2fBAMS-84-8-1055&partnerID=40&md5=846887f08e446cb7c59ec9e83e0998f5","Each spring and fall, the Laboratory for Atmospheres in the Goddard Earth Sciences Directorate presents a seminar series on a wide range of atmospheric topics. Just recently, the group hosted a workshop on cumulus parameterization schemes. In particular, cloud modelers, large-scale modelers, observationalists, and parameterization developers discussed the past, current, and future research and applications for cumulus parameterization."
"35572096100;7007108728;","Roundness and aspect ratio of particles in ice clouds",2003,"10.1175/1520-0469(2003)060<1795:RAAROP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141626549&doi=10.1175%2f1520-0469%282003%29060%3c1795%3aRAAROP%3e2.0.CO%3b2&partnerID=40&md5=6319ca0c0af035a75a97c00a9230cd06","The frequency of occurrence of the aspect ratio and roundness of particles in ice clouds from aircraft observations have been examined. Images of cloud particles were measured by a cloud particle imager (CPI) at 2.3-μm resolution, installed on the National Research Council (NRC) of Canada Convair-580. Data were collected in winter midlatitude and polar stratiform clouds associated with frontal systems during three field projects in the Canadian and U.S. Arctic and over the Great Lakes. Approximately 106 images of particles measured in ice clouds were included in the statistics. The frequency of occurrence of the aspect ratio and roundness were calculated in eight 5° temperature intervals from -40°C to 0°C. In each temperature interval, the distributions were calculated for 12 size intervals in the range from 20 μm to 1 mm. It was found that the roundness is a function of particle size and within each size interval it does not depend significantly on temperature. However, the aspect ratio of particles with 60 μm &lt; D &lt; 1000 μm is mainly a function of temperature and does not depend on size. The fraction of spherical particles in ice clouds rapidly decreases with particle size. The fraction of spherical particles in the size range 20 μm &lt; Dmax &lt; 30 μm on average does not exceed 50%. Ice clouds do not contain significant numbers of spherical particles larger than 60 μm. The information on the habits of small ice particles obtained here gives an insight on the mechanisms of ice formation in clouds. The results can be used for parameterization of particle habits in radiation transfer, weather and climate models, and in remote sensing retrievals. It may also be of interest for calculations of collision efficiency in modeling of interaction of cloud particles with moving platforms related to in-flight icing."
"6603452942;6603133549;","Analysis and prediction of cirrus-top altitude and ice water path in a mesoscale area",2003,"10.1175/1520-0450(2003)042<1092:AAPOCA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141849064&doi=10.1175%2f1520-0450%282003%29042%3c1092%3aAAPOCA%3e2.0.CO%3b2&partnerID=40&md5=0011abb80b7086197a5622df9d77f7f5","Vertical distributions of clouds have been a focus of many studies, motivated by their importance in radiative transfer processes in climate models. This study examines the horizontal distribution of cirrus clouds by means of satellite imagery analyses and numerical weather prediction model forecasts. A ground-truth dataset based on two aircraft mission periods flying particle probes through cirrus over a ground-based cloud radar is developed. Particle probe measurements in the cirrus clouds are used to compute ice water content and radar reflectivity averages in short time periods (25-30 s). Relationships for ice water content as a function of reflectivity are developed for 6-K ambient temperature categories. These relationships are applied to the radar-measured shorterm-averaged reflectivities to compute vertical profiles of ice water content, which are vertically integrated over the depth of the observed cirrus clouds to form ice water path estimates. These and cloud-top height are compared with the same quantities as retrieved by the Geostationary Operational Environmental Satellite (GOES) level-2B algorithm applied to four channels of GOES-8 imagery measurements. The agreement in cloud-top height is reasonable (generally less than 2-km difference). The ice water path retrievals are smaller in magnitude than the radar estimates, and this difference grows with increasing cirrus thickness. Comparisons of a sequence of the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5) predictions and GOES level-2B retrievals of ice cloud tops for the convectively active second mission period showed that the MM5 cirrus areal extent was somewhat greater than the GOES depictions. Cloud-top height ranges were similar. MM5 is capable of producing ice water path magnitudes similar to the radar estimates, but the GOES retrievals are much more limited. Ninety-eight percent of the GOES grid points had ice water paths no greater than 60 g m-2, as compared with 74% for MM5. Ten percent of MM5 points had ice water content &gt;200 g m-2, as compared with 0.07% for GOES retrievals. Based on this study, we conclude that GOES level-2B cloud-top retrievals are a reliable tool for prediction evaluations but the algorithm's retrievals of ice water path are not."
"7004076402;7005851232;24556796800;7103033688;","The role of the oceans in climate",2003,"10.1002/joc.926","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0041924703&doi=10.1002%2fjoc.926&partnerID=40&md5=78bd1639852fffcbbcff519c75d2af73","The ocean is increasingly seen as a vital component of the climate system. It exchanges with the atmosphere large quantities of heat, water, gases, particles and momentum. It is an important part of the global redistribution of heat from tropics to polar regions keeping our planet habitable, particularly equatorward of about 30°. In this article we review recent work examining the role of the oceans in climate, focusing on research in the Third Assessment Report of the IPCC and later. We discuss the general nature of oceanic climate variability and the large role played by stochastic variability in the interaction of the atmosphere and ocean. We consider the growing evidence for biogeochemical interaction of climatic significance between ocean and atmosphere. Air-sea exchange of several radiatively important gases, in particular CO2, is a major mechanism for altering their atmospheric concentrations. Some more reactive gases, such as dimethyl sulphide, can alter cloud formation and hence albedo. Particulates containing iron and originating over land can alter ocean primary productivity and hence feedbacks to other biogeochemical exchanges. We show that not only the tropical Pacific Ocean basin can exhibit coupled ocean-atmosphere interaction, but also the tropical Atlantic and Indian Oceans. Longer lived interactions in the North Pacific and Southern Ocean (the circumpolar wave) are also reviewed. The role of the thermohaline circulation in long-term and abrupt climatic change is examined, with the freshwater budget of the ocean being a key factor for the degree, and longevity, of change. The potential for the Mediterranean outflow to contribute to abrupt change is raised. We end by examining the probability of thermohaline changes in a future of global warming. Copyright © 2003 Royal Meteorological Society."
"7006033356;35425197200;7401548835;6603949518;","Impact on regional winter climate by CO2 increases vs. by maritime-air advection",2003,"10.1029/2003GL017545","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242318271&doi=10.1029%2f2003GL017545&partnerID=40&md5=12a584317ade0eff28a70d598a45c4c1","Fractional Outgoing Radiation, FOR (dimensionless), defined as the ratio of Outgoing Longwave Radiation, OLR (W/m2), to upward Surface Longwave Emission, SLE (W/m2), is a basic parameter for analyzing regional greenhouse effect. Here, FOR values are derived from a General Circulation Model by extracting OLR and SLE over areas in east-central Europe (at about 60°N) one hour after injecting appropriate CO2 concentration (adjustments to the atmospheric profile are thus excluded) to the Feb. 1 midnight simulation. The reduction in FOR is 0.00051 when atmospheric CO2 increases by 14 ppm, which is the currently expected per-decade increase. Fluctuations in the North-Atlantic surface winds produce fluctuations in FOR over central Europe: monthly-mean FOR in strong-wind February 1990 was 0.679, but 0.758 in weak-wind, lower cloud-fraction February 1996. Strong maritime-air advection in 1990 resulted thus in FOR reduced by 0.079, effect by two orders-of-magnitude stronger than the decrease effected by the per-decade increase in CO2."
"55468534200;7003371432;7103172539;","Radiation budgets in the Mackenzie River Basin: Retrieval from satellite observations and an evaluation of the Canadian Regional Climate Model",2003,"10.1175/1525-7541(2003)004<0731:RBITMR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141872362&doi=10.1175%2f1525-7541%282003%29004%3c0731%3aRBITMR%3e2.0.CO%3b2&partnerID=40&md5=0cd5939d9ecad277adfa448fc762e632","The Canadian Global Energy and Water Cycle Experiment (GEWEX) Enhanced Study (CAGES) was a 14-month period in 1998-99 during which there were enhanced measurements of water vapor, precipitation, snow cover, radiation, snowmelt, evaporation, stream discharge, and other variables in the Mackenzie River basin (MRB). These measurements provided the initialization and validation fields for modeling and remote sensing studies. During the CAGES period there were only limited broadband satellite observations of radiation fluxes over the MRB from the second flight module of the Scanner for Radiation Budget (ScaRaB) instrument. A more extensive dataset of solar radiation fluxes at the top of the atmosphere (TOA) and at the surface was derived for CAGES from the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) observations. The derived solar radiation fluxes at the surface were evaluated against the surface measurements in the basin. The results show that mean differences are generally less than 10 W m-2 at each site. Solar fluxes at the TOA and at the surface, and longwave (LW) fluxes at the TOA from the Canadian Regional Climate Model (CRCM) are compared with those from satellite measurements and retrievals. It is found that the CRCM overestimated the TOA reflected solar flux consistently by an average of 33 W m-2 during summer months, while during months when the surface is mainly covered by snow, the CRCM agrees with satellite retrievals well, with a mean difference of 2.1 W m-2. The differences in the basin monthly mean atmospheric absorption between the CRCM and the satellite retrievals for 9 months during the CAGES period vary from -11 to 12 W m-2. The overestimation of the TOA-reflected fluxes in the model during the summer months is mainly at the expense of an underestimation of the net surface solar fluxes. A comparison of cloud amount from the CRCM and the satellite retrievals shows an overprediction by the CRCM, which is responsible for the overestimation of the TOA-reflected flux during the summer months. A comparison of outgoing LW flux from the CRCM with satellite measurements in winter months during the CAGES period shows the CRCM fluxes to be 6-12 W m-2 less than the measured fluxes, which is at least partly due to the underestimation of surface temperature in the model."
"55373058100;","The use of an objective index in the synoptic routine work in order to forecast low stratus",2003,"10.1007/s00703-002-0572-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344984211&doi=10.1007%2fs00703-002-0572-8&partnerID=40&md5=735d59581baf4500a0f80ff7b80eb587","The cold seasons (October to March) of the years 1960 to 1984 have been investigated for inversions around Vienna. The basic material consists of climate and synoptic data as well as soundings taken at 0000 UTC and 1200 UTC at Vienna - Hohe Warte. These observations are filtered in three steps. First all days with inversions in the planetary boundary layer are selected which yields 1795 cases. For these cases the sounding data are used to calculate a so called inversion index I. This index has been developed as an objective measure for the intensity and the vertical extent of inversions. It is used as criterion for the information of low stratus. The second filter discards episodes with precipitation leaving 664 cases with dry but cloudy or foggy weather in the low lands. These remaining cases, for which the large scale weather patterns are determined, are again filtered to leave those with clear skies on the mountains, yielding 187 final cases. They are used to define rules for the formation of low stratus around Vienna, comprising rules for the time of onset and the persistency of low stratus. Further the large scale weather patterns leading to such situations are determined and the limiting values of the inversion index associated with persistent low stratus are found for every month of the cold saison of the year. So this work aims at improving the score of forecasting the formation and persistence of low stratus in the region of Vienna. There was made a verification with this inversion index for the cold season 1999/2000. Using the inversion index the results show that the score of low stratus forecasts are improving. In nearly 30% oft the investigated cases (16 out of 57) the forecasts would have been better, in 62% (36 out of 57) the criteria of the inversion index would have supported the forecasts."
"6602991169;7003652738;6507162029;","Use of radar remote sensing (RADARSAT) to map winter wetland habitat for shorebirds in an agricultural landscape",2003,"10.1007/s00267-002-2920-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342306174&doi=10.1007%2fs00267-002-2920-3&partnerID=40&md5=84c00f3a0f4c15bf62686a6ddb1f406e","Many of today's agricultural landscapes once held vast amounts of wetland habitat for waterbirds and other wildlife. Successful restoration of these landscapes relies on access to accurate maps of the wetlands that remain. We used C-band (5.6-cm-wavelength), HH-polarized radar remote sensing (RADARSAT) at a 38° incidence angle (8-m resolution) to map the distribution of winter shorebird (Charadriiformes) habitat on agricultural lands in the Willamette Valley of western Oregon. We acquired imagery on three dates (10 December 1999, 27 January 2000, and 15 March 2000) and simultaneously collected ground reference data to classify radar signatures and evaluate map accuracy of four habitat classes: (1) wet with ≤ 50% vegetation (considered optimal shorebird habitat), (2) wet with > 50% vegetation, (3) dry with ≤ 50% vegetation, and (4) dry with > 50% vegetation. Overall accuracy varied from 45 to 60% among the three images, but the accuracy of focal class 1 was greater, ranging from 72 to 80%. Class 4 coverage was stable and dominated maps (40% of mapped study area) for all three dates, while class 3 coverage decreased slightly throughout the study period. Among wet classes, class 1 was most abundant (30% coverage) in December and January, decreasing in March by 15%. Conversely, class 2 increased dramatically from January to March, likely due to transition from class 1 as vegetation grew. This approach was successful in detecting optimal habitat for shorebirds on agricultural lands. For modest classification schemes, radar remote sensing is a valuable option for wetland mapping in areas where cloud cover is persistent. © 2003 Springer-Verlag New York Inc."
"7004715270;7005171879;6602550636;7007061674;7402049334;7401651197;6603385031;7005968859;","African dust aerosols as atmospheric ice nuclei",2003,"10.1029/2003GL017410","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141976756&doi=10.1029%2f2003GL017410&partnerID=40&md5=e7a927a3ea56c1d0f20eaca3f6dc8f1e","Measurements of the ice nucleating ability of aerosol particles in air masses over Florida having sources from North Africa support the potential importance of dust aerosols for indirectly affecting cloud properties and climate. The concentrations of ice nuclei within dust layers at particle sizes below 1 μm exceeded 1 cm 3; the highest ever reported with our device at temperatures warmer than homogeneous freezing conditions. These measurements add to previous direct and indirect evidence of the ice nucleation efficiency of desert dust aerosols, but also confirm their contribution to ice nuclei populations at great distances from source regions."
"10139397300;57203200427;55947099700;7003478309;","Aerosol absorption over the clear-sky oceans deduced from POLDER-1 and AERONET observations",2003,"10.1029/2003GL017121","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141942137&doi=10.1029%2f2003GL017121&partnerID=40&md5=7b35534f4efcf1cb77f57eacd723340d","We estimate aerosol absorption over the clear-sky oceans using aerosol geophysical products from POLDER-1 space measurements and absorption properties from ground-based AERONET measurements. Our best estimate is 2.5 Wm 2 averaged over the 8-month lifetime of POLDER-1. Low and high absorption estimates are 2.2 and 3.1 Wm 2 based on the variability in aerosol single-scattering albedo observed by AERONET. Main sources of uncertainties are the discrimation of the aerosol type from satellite measurements, and potential clear-sky bias induced by the cloud-screening procedure."
"7403968239;6602098362;55729083100;15760875400;","On the radiative and dynamical feedbacks over the equatorial Pacific cold tongue",2003,"10.1175/2786.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042890458&doi=10.1175%2f2786.1&partnerID=40&md5=da311c5a46946cbdfc0fc360f8ccf562","An analysis of the climatic feedbacks in the NCAR Community Climate Model, version 3 (CCM3) over the equatorial Pacific cold tongue is presented. Using interannual signals in the underlying SST, the radiative and dynamical feedbacks have been calculated using both observations and outputs from the NCAR CCM3. The results show that the positive feedback from the greenhouse effect of water vapor in the model largely agrees with that from observations. The dynamical feedback from the atmospheric transport in the model is also comparable to that from observations. However, the negative feedback from the solar forcing of clouds in the model is significantly weaker than the observed, while the positive feedback from the greenhouse effect of clouds is significantly larger. Consequently, the net atmospheric feedback in the CCM3 over the equatorial cold tongue region is strongly positive (5.1 W m-2 K-1), while the net atmospheric feedback in the real atmosphere is strongly negative (-6.4 W m-2 K-1). A further analysis with the aid of the International Satellite Cloud Climatology Project (ISCCP) data suggests that cloud cover response to changes in the SST may be a significant error source for the cloud feedbacks. It is also noted that the surface heating over the cold tongue in CCM3 is considerably weaker than in observations. In light of results from a linear feedback system, as well as those from a more sophisticated coupled model, it is suggested that the discrepancy in the net atmospheric feedback may have contributed significantly to the cold bias in the equatorial Pacific in the NCAR Climate System Model (CSM)."
"7004369046;7407016988;6603145318;23502460300;","Corrected TOGA COARE sounding humidity data: Impact on diagnosed properties of convection and climate over the warm pool",2003,"10.1175/2790.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0041387508&doi=10.1175%2f2790.1&partnerID=40&md5=c963c354b1aa778c9113a79814150658","This study reports on the humidity corrections in the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) upper-air sounding dataset and their impact on diagnosed properties of convection and climate over the warm pool. During COARE, sounding data were collected from 29 sites with Vaisala-manufactured systems and 13 sites with VIZ-manufactured systems. A recent publication has documented the characteristics of the humidity errors at the Vaisala sites and a procedure to correct them. This study extends that work by describing the nature of the VIZ humidity errors and their correction scheme. The corrections, which are largest in lower-tropospheric levels, generally increase the moisture in the Vaisala sondes and decrease it in the VIZ sondes. Use of the corrected humidity data gives a much different perspective on the characteristics of convection during COARE. For example, application of a simple cloud model shows that the peak in convective mass flux shifts from about 8°N with the uncorrected data to just south of the equator with corrected data, which agrees better with the diagnosed vertical motion and observed rainfall. Also, with uncorrected data the difference in mean convective available potential energy (CAPE) between Vaisala and VIZ sites is over 700 J kg 1: with the correction, both CAPEs are around ∼ 1300 J kg 1, which is consistent with a generally uniform warm pool SST field. These results suggest that the intensity and location of convection would differ significantly in model simulations with humidity-corrected data, and that the difficulties which the reanalysis products had in reproducing the observed rainfall during COARE may be due to the sonde humidity biases. The humidity-corrected data appear to have a beneficial impact on budget-derived estimates of rainfall and radiative heating rate, such that revised estimates show better agreement with those from independent sources."
"7006174850;7101795549;","Unified treatment of thermodynamic and optical variability in a simple model of unresolved low clouds",2003,"10.1175/1520-0469(2003)60<1621:UTOTAO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0041845372&doi=10.1175%2f1520-0469%282003%2960%3c1621%3aUTOTAO%3e2.0.CO%3b2&partnerID=40&md5=84a9bb1aa63819b366ca65e9b97a880e","Comparative studies of global climate models have long shown a marked sensitivity to the parameterization of cloud properties. Early attempts to quantify this sensitivity were hampered by diagnostic schemes that were inherently biased toward the contemporary climate. Recently, prognostic cloud schemes based on an assumed statistical distribution of subgrid variability replaced the older diagnostic schemes in some models. Although the relationship between unresolved variability and mean cloud amount is known in principle, a corresponding relationship between ice-free low cloud thermodynamic and optical properties is lacking. The authors present a simple, analytically tractable statistical optical depth parameterization for boundary layer clouds that links mean reflectivity and emissivity to the underlying distribution of unresolved fluctuations in model thermodynamic variables. To characterize possible impacts of this parameterization on the radiative budget of a large-scale model, they apply it to a zonally averaged climatology, illustrating the importance of a coupled treatment of subgrid-scale condensation and optical variability. They derive analytic expressions for two response functions that characterize two potential low cloud feedback scenarios in a warming climate."
"57208765879;35468686100;7101677832;7102063963;7201826462;8680433600;7201607592;","The MODIS cloud products: Algorithms and examples from terra",2003,"10.1109/TGRS.2002.808301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36549071073&doi=10.1109%2fTGRS.2002.808301&partnerID=40&md5=cf6fdda50a620228179e73a4a144dacc","The Moderate Resolution Imaging Spectroradiometer (MODIS) is one of five instruments aboard the Terra Earth Observing System (EOS) platform launched in December 1999. After achieving final orbit, MODIS began earth observations in late February 2000 and has been acquiring data since that time. The instrument is also being flown on the Aqua spacecraft, launched in May 2002. A comprehensive set of remote sensing algorithms for cloud detection and the retrieval of cloud physical and optical properties have been developed by members of the MODIS atmosphere science team. The archived products from these algorithms have applications in climate change studies, climate modeling, numerical weather prediction, as well as fundamental atmospheric research. In addition to an extensive cloud mask, products include cloud-top properties (temperature, pressure, effective emissivity), cloud thermodynamic phase, cloud optical and microphysical parameters (optical thickness, effective particle radius, water path), as well as derived statistics. We will describe the various algorithms being used for the remote sensing of cloud properties from MODIS data with an emphasis on the pixel-level retrievals (referred to as Level-2 products), with 1-km or 5-km spatial resolution at nadir. An example of each Level-2 cloud product from a common data granule (5 min of data) off the coast of South America will be discussed. Future efforts will also be mentioned. Relevant points related to the global gridded statistics products (Level-3) are highlighted though additional details are given in an accompanying paper in this issue. © 2003 IEEE."
"7201472576;","A 10 year cloud climatology over Scandinavia derived from NOAA Advanced Very High Resolution Radiometer imagery",2003,"10.1002/joc.916","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042974064&doi=10.1002%2fjoc.916&partnerID=40&md5=3512889763413565f9ab88bc4ff48658","Results from a satellite-based method to compile regional cloud climatologies covering the Scandinavian region are presented. Systematic processing of multispectral image data from the NOAA Advanced Very High Resolution Radiometer (AVHRR) instrument has been utilized to provide monthly cloud climatologies covering the period 1991-2000. Considerable local-scale variation of cloud amounts was found in the region. The inland Baltic Sea and adjacent land areas exhibited a large-amplitude annual cycle in cloudiness (high cloud amounts in winter, low cloud amounts in summer) whereas a weak-amplitude reversed annual cycle (high cloud amounts with a weak maximum in summer) was found for the Scandinavian mountain range. As a contrast, conditions over the Norwegian Sea showed high and almost unchanged cloud amounts during the course of the year. Some interesting exceptions to these patterns were also seen locally. The quality of the satellite-derived cloud climatology was examined through comparisons with climatologies derived from surface cloud observations, from the International Satellite Cloud Climatology Project (ISCCP) and from the European Centre for Medium-range Weather Forecasts ERA-40 data set. In general, cloud amount deviations from surface observations were smaller than 10% except for some individual winter months, when the separability between clouds and snow-covered cold land surfaces is often poor. The ISCCP data set showed a weaker annual cycle in cloudiness, generally caused by higher summer-time cloud amounts in the region. Very good agreement was found with the ERA-40 data set, especially for the summer season. However, ERA-40 showed higher cloud amounts than SCANDIA and ISCCP during the winter season. The derived cloud climatology is affected by errors due to temporal AVHRR sensor degradation, but they appear to be small for this particular study. The data set is proposed as a valuable data set for validation of cloud description in numerical weather prediction and regional climate simulation models. © 2003 Royal Meteorological Society."
"6602132130;7006095466;","A probabilistic description of convective mass fluxes and its relationship to extreme-value theory",2003,"10.1256/qj.01.124","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0043128740&doi=10.1256%2fqj.01.124&partnerID=40&md5=fe9c16d020b50b9022a13b967077244b","The vertical flux of mass by atmospheric convection, and convective cloud systems in particular, is a key quantity used in parametrization schemes for numerical weather-prediction models and climate models. The concept of formulating mass fluxes in terms of statistical quantities is discussed and a probabilistic description of the upward mass fluxes, based on extreme-value theory, is presented. This approach is illustrated by a statistical analysis of two-dimensional, numerical realizations of two regimes of tropical convection, namely squall lines and non-squall clusters. Our statistical model allows these distinct cloud systems, which play a key role in determining the shape of the mass-flux profile, to be efficiently integrated. Also taken into account is the distinction between mesoscale and convective components of the mass flux."
"7402523567;57203348817;","Cloud timescales and orographic precipitation",2003,"10.1175/2995.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042463631&doi=10.1175%2f2995.1&partnerID=40&md5=659ea7b2b3f6a11bb0b148d2f97e7398","Orographic precipitation is studied by analyzing the sensitivity of numerical simulations to variations in mountain height, width, and wind speed. The emphasis is on upslope lifting over isolated mountains in cold climates. An attempt is made to capture the essential steady-state volume-averaged cloud physics in a pair of coupled nonlinear algebraic equations. To do this, single-pathway snow formation models are analyzed with both linear and nonlinear accretion formulations. The linear model suggests that the precipitation efficiency is determined by three timescales-the advection timescale (Ta), fallout timescale (Tf), and a constant timescale for snow generation (Tes). Snow generation is controlled by the ratio of Tes/Ta and the fraction of the snow that falls to the ground is controlled by the ratio of Tf/Ta. Nonlinear terms, representing accretion, reduce the utility of the timescale concept by introducing a threshold or ""bifurcation"" point, that is, a critical condensation rate that separates two states: A precipitating state and a nonprecipitating state. If the condensation rate is below the threshold value, no snow is generated. As it surpasses the threshold value, the snow generation rate increases rapidly. The threshold point is a function of advection and fallout timescales, low-level water content, mountain height, and a collection factor, which is further dependent on the geometries, terminal velocity, and density of snow particles. An approximate formula for precipitation efficiency is given in closed form."
"7102128820;7202154370;6603603545;7007114756;7003728829;7006577245;","Characteristics of mixed-phase clouds. I: Lidar, radar and aircraft observations from CLARE'98",2003,"10.1256/rj.01.208","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0041488809&doi=10.1256%2frj.01.208&partnerID=40&md5=fcb43a8ccdaf16ee6ebb758ce3f71a5e","Results are presented from two case-studies during the 1998 Cloud Lidar And Radar Experiment (CLARE'98) in which mixed-phase clouds were observed by a multitude of ground-based and airborne instruments. In both cases supercooled liquid water was present in the form of highly reflective layers in lidar imagery, while the radar echo was dominated by the contribution from the much larger ice particles. In the first case-study, four individual liquid-water layers were observed by an airborne nadir-pointing polarimetric lidar at temperatures between -7 °C and -15 °C, embedded within a warm-frontal ice cloud. Their phase was confirmed by the in situ measurements and by their very low depolarization of the lidar signal. The effective droplet radius ranged from 2 to 5 μm. Simultaneous temperature and vertical-wind measurements by the aircraft demonstrated that they were generated by a gravity wave with a wavelength of around 15 km. Thin sector plates grew rapidly in the high-supersaturation conditions and were responsible for the high values of differential reflectivity measured by the ground-based radar in the vicinity of the layers. In the second case-study a liquid-water altocumulus layer was observed at -23 °C, which was slowly glaciating. Profiles of liquid and ice extinction coefficient, water content and effective radius were derived from the remote measurements taken in both cases, using radar-lidar and dual-wavelength radar techniques to size the ice particles; where in situ validation was available, agreement was good. Radiative-transfer calculations were then performed on these profiles to ascertain the radiative effect of the supercooled water. It was found that, despite their low liquid-water path (generally less than 10-20 g m-2 , these clouds caused a significant increase in the reflection of solar radiation to space, even when cirrus was present, above which the long-wave signal dominated. In the cases considered, their capacity to decrease the net absorbed radiation was at least twice as large as that of the ice. The layers were typically 100-200 m thick, suggesting that they are unlikely to be adequately represented by the resolutions of current forecast and climate models. These results suggest that a spaceborne lidar and radar would be ideally suited to characterizing the occurrence and climatological importance of mixed-phase clouds on a global scale."
"7005304841;7004920873;","Regional temperature response due to indirect sulfate aerosol forcing: Impact of model resolution",2003,"10.1007/s00382-003-0311-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042442077&doi=10.1007%2fs00382-003-0311-y&partnerID=40&md5=5c18e08455be7451852e50c1261d8ccb","A regional atmospheric climate model, including an interactive module of the tropospheric sulfur cycle, has been used to conduct yearlong equilibrium simulations of the temperature response due to anthropogenic sulfate aerosol forcing on cloud albedo. A main purpose is to examine differences in the magnitudes as well as patterns of forcing and response between simulations conducted with high (0.4° × 0.4°, HR) and low (2.0° × 2.0°, LR) spatial resolutions. Averaged over the model domain, the annual mean indirect forcing differs by only 7% between HR and LR and there is no difference in the annual mean temperature response. The results thus indicate that it is not important to represent small-scale variability (≤ 2.8°) when the average indirect climate effect over Europe is considered. However, a notable difference in the geographical distributions of forcing and response is obtained when different resolutions are employed. In addition, a clear correspondence between the patterns of radiative forcing and temperature response is obtained when HR is used. The correspondence is less obvious in the LR simulation. It is interesting to compare the present results with those of Roeckner et al. 1999, who found a poor correspondence between the patterns of forcing and response in their simulations using a coarse resolution GCM."
"36951461600;6506944401;6504642969;7007170257;","Conservation assessment of current and proposed nature reserves of Tamaulipas state, Mexico",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042814865&partnerID=40&md5=1b362da4365b22eb38608d14ce03b27e","The Mexican state of Tamaulipas located in the northeastern portion of the country currently has five state nature reserves covering slightly less than 3% of its land area. These reserves were established for a variety of reasons, many unrelated to the protection of biological resources. In 2000 in response to a growing concern about the lack of organized conservation reserve planning to protect the important biological and physical features of Mexico, the Mexican Commission for Knowledge and Use of Biodiversity (CONABIO) proposed 13 new terrestrial reserves for Tamaulipas. If established these new reserves would increase the proportion of terrestrial protected lands in the state to over 21%. We compiled a geographic information system (GIS) using existing digital thematic maps of physical and biological features to examine how the existing and proposed reserves might serve to protect the biodiversity and physical features of the state. We found that most of the existing protected sites occur in areas with elevations > 1000-2000 m with temperate climate and dominated by pine forest, oak forest, and cloud forest vegetation cover types. The state's dominant biotic region - low elevation coastal plain with tropical and arid climate types and xeric scrub vegetation - is disproportionately underrepresented in the current reserve system. The creation of the proposed areas would substantially increase the protection of mid and high elevation lands. The largest gap in the protected lands network would be low elevation, level, coastal lands."
"35414069200;7005995192;7003995144;55730024500;7403897936;7003426743;7402480218;","Radiosonde humidity soundings and microwave radiometers during Nauru99",2003,"10.1175/1520-0426(2003)20<953:RHSAMR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0043166318&doi=10.1175%2f1520-0426%282003%2920%3c953%3aRHSAMR%3e2.0.CO%3b2&partnerID=40&md5=16bd473f0f1ec0e545ceb7a4e6a772da","During June-July 1999, the NOAA R/V Ron H. Brown (RHB) sailed from Australia to the Republic of Nauru where the Department of Energy's Atmospheric Radiation Measurement (ARM) Program operates a long-term climate observing station. During July, when the RHB was in close proximity to the island of Nauru, detailed comparisons of ship- and island-based instruments were possible. Essentially identical instruments were operated from the ship and the island's Atmospheric Radiation and Cloud Station (ARCS)-2. These instruments included simultaneously launched Vaisala RS80-H radiosondes, the Environmental Technology Laboratory's (ETL) Fourier transform infrared radiometer (FTIR), and ARM's atmospheric emitted radiance interferometer (AERI), as well as cloud radars/ceilometers to identify clear conditions. The ARM microwave radiometer (MWR) operating on Nauru provided another excellent dataset for the entire Nauru99 experiment. The calibration accuracy was verified by a liquid nitrogen blackbody target experiment and by consistent high quality tipping calibrations throughout the experiment. Comparisons were made for calculated clear-sky brightness temperature (Tb) and for precipitable water vapor (PWV). These results indicate that substantial errors, sometimes of the order of 20% in PWV, occurred with the original radiosondes. When a Vaisala correction algorithm was applied, calculated Tbs were in better agreement with the MWR than were the calculations based on the original data. However, the improvement in Tb comparisons was noticeably different for different radiosonde lots and was not a monotonic function of radiosonde age. Three different absorption algorithms were compared: Liebe and Layton, Liebe et al., and Rosenkranz. Using AERI spectral radiance observations as a comparison standard, scaling of radiosondes by MWR data was compared with both original and corrected soundings."
"6603054569;6602624175;57192804561;6506713636;6602633306;9249236100;","Description and evaluation of the bergen climate model: ARPEGE coupled with MICOM",2003,"10.1007/s00382-003-0317-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0043011244&doi=10.1007%2fs00382-003-0317-5&partnerID=40&md5=f5d9ff16b239e6cb11c9c1c4a8fd5e9e","A new coupled atmosphere-ocean-sea ice model has been developed, named the Bergen Climate Model (BCM). It consists of the atmospheric model ARPEGE/IFS, together with a global version of the ocean model MICOM including a dynamic-thermodynamic sea ice model. The coupling between the two models uses the OASIS software package. The new model concept is described, and results from a 300-year control integration is evaluated against observational data. In BCM, both the atmosphere and the ocean components use grids which can be irregular and have non-matching coastlines. Much effort has been put into the development of optimal interpolation schemes between the models, in particular the non-trivial problem of flux conservation in the coastal areas. A flux adjustment technique has been applied to the heat and freshwater fluxes. There is, however, a weak drift in global mean sea-surface temperature (SST) and sea-surface salinity (SSS) of respectively 0.1 °C and 0.02 psu per century. The model gives a realistic simulation of the radiation balance at the top-of-the-atmosphere, and the net surface fluxes of longwave, shortwave, and turbulent heat fluxes are within observed values. Both global and total zonal means of cloud cover and precipitation are fairly close to observations, and errors are mainly related to the strength and positioning of the Hadley cell. The mean sea-level pressure (SLP) is well simulated, and both the mean state and the interannual standard deviation show realistic features. The SST field is several degrees too cold in the equatorial upwelling area in the Pacific, and about 1 °C too warm along the eastern margins of the oceans, and in the polar regions. The deviation from Levitus salinity is typically 0.1 psu - 0.4 psu, with a tendency for positive anomalies in the Northern Hemisphere, and negative in the Southern Hemisphere. The sea-ice distribution is realistic, but with too thin ice in the Arctic Ocean and too small ice coverage in the Southern Ocean. These model deficiencies have a strong influence on the surface air temperatures in these regions. Horizontal oceanic mass transports are in the lower range of those observed. The strength of the meridional overturning in the Atlantic is 18 Sv. An analysis of the large-scale variability in the model climate reveals realistic El Niño - Southern Oscillation (ENSO) and North Atlantic-Arctic Oscillation (NAO/AO) characteristics in the SLP and surface temperatures, including spatial patterns, frequencies, and strength. While the NAO/AO spectrum is white in SLP and red in temperature, the ENSO spectrum shows an energy maximum near 3 years."
"24080112400;7102866124;7005247310;","The impact of deforestation on cloud cover over the Amazon arc of deforestation",2003,"10.1016/S0034-4257(03)00095-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038606454&doi=10.1016%2fS0034-4257%2803%2900095-6&partnerID=40&md5=94a82fc5e12bde238f8da7323a828d12","Atmospheric general circulation model (AGCM) simulations predict that a complete deforestation of the Amazon basin would lead to a significant climate change; however, it is more difficult to determine the amount of deforestation that would lead to a detectable climate change. This paper examines whether cloudiness has already changed locally in the Brazilian arc of deforestation, one of the most deforested regions of the Amazon basin, where over 15% of the primary forest has been converted to pasture and agriculture. Three pairs of deforested/forested areas have been selected at a scale compatible with that of climate model grids to compare changes in land cover with changes in cloudiness observed in satellite data over a 10-year period from 1984 to 1993. Analysis of cloud cover trends suggests that a regional climate change may already be underway in the most deforested part of the arc of deforestation. Although changes in cloud cover over deforested areas are not significant for interannual variations, they are for the seasonal and diurnal distributions. During the dry season, observations show more low-level clouds in early afternoon and less convection at night and in early morning over deforested areas. During the wet season, convective cloudiness is enhanced in the early night over deforested areas. Generally speaking, the results suggest that deforestation may lead to increased seasonality; however, some of the differences observed between deforested and forested areas may be related to their different geographical locations. © 2003 Elsevier Science Inc. All rights reserved."
"7005171879;7004715270;7007020226;6602550636;","Saharan dust storms and indirect aerosol effects on clouds: CRYSTAL-FACE results",2003,"10.1029/2003GL017371","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141922248&doi=10.1029%2f2003GL017371&partnerID=40&md5=04d8bdccacde1615ad89c34238acf214","A recent field experiment in southern Florida using aircraft and polarization lidar shows that mineral dust particles transported from Saharan Africa are effective ice nuclei, apparently capable of glaciating a mildly supercooled (-5.2° to -8.8°C) altocumulus cloud. These results are similar to those from Asian dust storm particles observed over the western US, suggesting that in the northern hemisphere major dust storms play a role in modulating climate through the indirect aerosol effect on cloud properties. If this is true of desert dusts in general, then even minor aeolian emissions could have an effect on regional weather and climate."
"6701606453;7202899330;","The tropical oceanic energy budget from the TRMM perspective. Part I: Algorithm and uncertainties",2003,"10.1175/1520-0442(2003)016<1967:TTOEBF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042847367&doi=10.1175%2f1520-0442%282003%29016%3c1967%3aTTOEBF%3e2.0.CO%3b2&partnerID=40&md5=1eb967c5c6058b8028fd545cfc0a78d8","The earth's weather and climate is driven by the meridional transport of energy required to establish a global balance between incoming energy from the sun and outgoing thermal energy emitted by the atmosphere and surface. Clouds and precipitation play an integral role in the exchange of these sources of energy between the surface, atmosphere, and space-enhancing reflection of solar radiation to space, trapping thermal emission from the surface, and providing a mechanism for the direct transfer of energy to the atmosphere through the release of latent heat in precipitation. This paper introduces a new multisensor algorithm for extracting longwave, shortwave, and latent heat fluxes over oceans from the sensors aboard the Tropical Rainfall Measuring Mission (TRMM) satellite. The technique synthesizes complementary information from distinct retrievals of high and low clouds and precipitation from the TRMM Microwave Imager (TMI) and Visible and Infrared Scanner (VIRS) instruments to initialize broadband radiative transfer calculations for deriving the structure of radiative heating in oceanic regions from 40°S to 40°N and its evolution on daily and monthly timescales. Sensitivity studies using rigorous estimates of the uncertainties in all input parameters and detailed comparisons with flux observations from the Clouds and Earth's Radiant Energy System (CERES) are used to study the dominant influences on the algorithm's performance and to assess the accuracy of its products. The results demonstrate that the technique provides monthly mean estimates of oceanic longwave fluxes at 1° resolution to an accuracy of ∼ 10 W m-2. Uncertainties in these estimates are found to arise primarily from a lack of explicit vertical cloud boundary information and errors in prescribed temperature and humidity profiles. Corresponding shortwave flux estimates are shown to be accurate to ∼ 25 W m-2, with uncertainties due to errors in cloud detection, poorly constrained cloud particle sizes, and uncertainties in the prescribed surface albedo. When viewed as a whole, the components of the method provide a tool to diagnose relationships between the climate, hydrologic cycle, and the earth's energy budget."
"6603258995;6701700126;7004497359;","Empirical estimation of the effect of urban heat advection on the temperature series of De Bilt (The Netherlands)",2003,"10.1002/joc.902","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037743391&doi=10.1002%2fjoc.902&partnerID=40&md5=4d492bc08ef961d338e750e2d9c8ac51","The influence of urban heat advection on the temperature time series of the Dutch GCOS station De Bilt has been studied empirically by comparing the hourly meteorological observations (1993-2000) with those of the nearby (7.5 km) rural station at Soesterberg. Station De Bilt is in the transition zone (TZ) between the urban and rural area, being surrounded by three towns. Utrecht, De Bilt and Zeist. The dependence of the hourly temperature differences between De Bilt and Soesterberg on wind direction has been examined as a function of season, day- and night-time hours and cloud amount. Strong dependence on wind direction was apparent for clear nights, with the greatest effects (up to 1 °C on average) for wind coming from the towns. The magnitude of the effect decreased with increasing cloudiness. The analysis suggests that most of the structure in the wind direction dependence is caused by urban heat advection to the measuring site in De Bilt. The urban heat advection is studied in more detail with an additive statistical model. Because the urban areas around the site expanded in the past century, urban heat advection trends contaminate the long-term trends in the temperature series (1897-present) of De Bilt. Based on the present work, we estimate that this effect may have raised the annual mean temperatures of De Bilt by 0.10 ± 0.06 °C during the 20th century, being almost the full value of the present-day urban heat advection. The 0.10 ± 0.06 °C rise due to urban heat advection corresponds to about 10% of the observed temperature rise of about 1.0 °C in the last century. Copyright © 2003 Royal Meteorological Society."
"6508068503;35592560600;7102084129;","Sensitivity of the global circulation to the suppression of precipitation by anthropogenic aerosols",2003,"10.1016/S0921-8181(02)00191-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038694813&doi=10.1016%2fS0921-8181%2802%2900191-1&partnerID=40&md5=df8162115283968496224f92e0f3b86f","From recent satellite observations, it is evident that an increase in cloud condensation nuclei - for instance, due to biomass burning - can substantially reduce rain efficiency of convective clouds. This is potentially important for the global climate since the release of latent heat due to condensation of water vapour and fallout of rain from cumulus convection is the most important source for available potential energy in the free troposphere. Beyond this, cumulus convection is a key process in controlling the water vapour content of the atmosphere. The sensitivity of the global climate to modification in rain efficiency of convective clouds due to the suppression of drop coalescence by anthropogenic aerosols is studied by using the atmospheric general circulation model (A-GCM), ECHAM4. This paper presents results from a 15-year sensitivity study, which considers the aerosol effect on warm precipitation formation. Effects on ice processes are not included yet, and therefore the results likely underestimate the magnitude of the full effects due to suppression of precipitation. Instantaneous forcing is large locally (up to 100% reduction of precipitation and the related latent heat release) but confined to small areas, leading to small large-scale mean anomalies in the convective heating and therefore the vertical temperature gradient. We found a definite perturbation of the global circulation, showing distinct sensitivity to the impact of aerosols on suppressing rainfall. © 2003 Elsevier Science B.V. All rights reserved."
"7601492669;57219122737;56962915800;","A highly resolved regional climate model (IPRC-RegCM) and its simulation of the 1998 severe precipitation event over China. Part I: Model description and verification of simulation",2003,"10.1175/1520-0442(2003)016<1721:AHRRCM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037669719&doi=10.1175%2f1520-0442%282003%29016%3c1721%3aAHRRCM%3e2.0.CO%3b2&partnerID=40&md5=aab9dddc9c0f1b399cead1691a8fcb72","East Asia is a region with complex topography, land surface conditions, coastlines, and with large contribution from mesoscale phenomena, such as the mei-yu/baiu frontal systems and tropical storms. To study the regional climate in such a region, a highly resolved regional climate model (IPRC-RegCM) has been recently developed at the International Pacific Research Center (IPRC). The distinct features of this model include the direct feedback of cumulus detrained cloud ice and cloud water into the grid-resolved quantities; the effect of cloud buoyancy on turbulence production with mixed-ice phase clouds: an explicit coupling between the cloud microphysics and radiation via cloud properties; an explicit coupling between land surface and radiation via surface albedo. direct and diffuse radiation fluxes; and the effect of frictionally generated dissipative heating. The model is documented in detail and the performance of the model is demonstrated by its simulation of the 1998 severe flooding event over China, the worst one since 1955. With the use of the objective analysis of the European Centre for Medium-Range Weather Forecasts (ECMWF), which is available at 12-h intervals with a resolution of 2.5° × 2.5°, as both the initial and lateral boundary conditions, the model was integrated from 26 April to 31 August 1998 with a resolution of 0.5° × 0.5° covering the area 5°-45°N. 90°-140°E. The model simulated realistically not only the temporal evolution of the area-averaged precipitation and the monthly mean precipitation spatial pattern but also the daily precipitation intensity distribution. The model reproduced the monsoon circulations, in particular, two episodes of the intraseasonal oscillation events that are believed to be closely related to the unusual double mei-yu periods over the Yangtze River basin in 1998."
"6507789680;55738957800;","Development and test of a cirrus parameterization scheme using NCAR CCM3",2003,"10.1175/1520-0469(2003)060<1325:DATOAC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038544389&doi=10.1175%2f1520-0469%282003%29060%3c1325%3aDATOAC%3e2.0.CO%3b2&partnerID=40&md5=0b8c5122d3c528d54a8511b3defe1092","Recent research has shown that depending on the cloud properties, cirrus clouds can either increase or decrease the overall heating of the earth-atmosphere system. Hence, the representation of cirrus clouds in GCMs is recognized as an important contemporary problem. In this study a new diagnostic cirrus parameterization scheme is developed with the intention of improving the simulation of cirrus macro- and microphysical properties in large-scale models. The scheme allows both large-scale motions and convective detrainment to be a source of moisture for cirrus. Water vapor depletion is calculated as diffusional growth of ice crystals with known size distributions, and the effective fallout from a model layer is estimated using mass-weighted fall velocities of the bulk precipitation. The scheme was implemented and tested with the NCAR Community Climate Model (CCM3). The seasonal means of cirrus cloud cover and ice water contents over the warm pool region, as simulated with the new cirrus parameterization, appeared to be much more realistic than in the standard model version when compared to satellite and in situ data. In contrast to the high amount of optically thin cirrus at all cirrus levels simulated by the standard CCM3, cirrus formed with the new scheme are significantly thicker with a reduced amount in the lower part of the upper troposphere (approximately 10-14 km), whereas cirrus formed below the tropopause (approximately 14-17 km) stay thin but have higher cover. It has also been found that a more realistic precipitation treatment not only results in the formation of thicker anvil cirrus, but also increases the rain and evaporation rates in the middle troposphere. These results suggest that cirrus clouds can be an important potential water vapor source in the tropical troposphere."
"6603025800;16637291100;","Antarctic cloud radiative forcing at the surface estimated from the AVHRR Polar Pathfinder and ISCCP D1 datadets, 1985-93",2003,"10.1175/1520-0450(2003)042<0827:ACRFAT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038267587&doi=10.1175%2f1520-0450%282003%29042%3c0827%3aACRFAT%3e2.0.CO%3b2&partnerID=40&md5=d9fc5f27aa2098ad8134f62d1f519ec4","Surface cloud radiative forcing from the newly extended Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder (APP-x) dataset and surface cloud radiative forcing calculated using cloud and surface properties from the International Satellite Cloud Climatology Project (ISCCP) D-series product were used in this 9-yr (1985-93) study. On the monthly timescale, clouds were found to have a warming effect on the surface of the Antarctic continent every month of the year in both datasets. Over the ocean poleward of 58.75°S, clouds were found to have a warming effect on the surface from March through October in the ISCCP-derived dataset and from April through September in the APP-x dataset. Net surface fluxes from both datasets were validated against net surface fluxes calculated from measurements of upwelling and downwelling shortwave and longwave radiation at the Neumayer and Amundsen-Scott South Pole stations in the Antartctic. The net all-wave surface flux from the ISCCP-derived dataset was found to be within 0.4-50 W m-2 of the net all-wave flux at the two stations on the monthly timescale. The APP-x net all-wave surface flux was found to be within 0.9-24 W m-2. Model sensitivity studies were conducted to gain insight into how the surface radiation budget in a cloudy atmosphere will change if certain cloud and surface properties were to change in association with regional and/ or global climate change. The results indicate that the net cloud forcing will be most sensitive to changes in cloud amount, surface reflectance, cloud optical depth, and cloud-top pressure."
"7202429440;7201432984;","North American, Asian, and Indian haze: Similar regional impacts on climate?",2003,"10.1029/2003GL016934","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042412176&doi=10.1029%2f2003GL016934&partnerID=40&md5=a0cab208d7594428b096f70e6ec9200c","Pollution plumes recur seasonally downwind of the Indian subcontinent and Asian continent due to industrial and vehicular emissions, biomass burning, and wind-blown dust. These plumes have been well documented by field campaigns and satellite observations and the environmental implications of the ""Asian Brown Cloud"" have been widely publicized in a recently released UNEP report [UNEP and C4, 2002]. Recent field experiments, however, demonstrate that the U.S. pollution plume can be as intense (in terms of aerosol mass concentration, aerosol optical depth, and ozone mixing ratio) as those downwind of India and Asia affecting regional climate along the U.S. East Coast. The use of identical sampling protocols in these experiments has been key in eliminating sampling biases and making the data directly comparable."
"35570389600;","Climate model studies of synchronously rotating planets",2003,"10.1089/153110703769016488","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4344717620&doi=10.1089%2f153110703769016488&partnerID=40&md5=d41588287f5ec05b5116b7a8118ed9fe","M stars constitute 75% of main sequence stars though, until recently, their star systems have not been considered suitable places for habitable planets to exist. In this study the climate of a synchronously rotating planet around an M dwarf star is evaluated using a three-dimensional global atmospheric circulation model. The presence of clouds and evaporative cooling at the surface of the planet result in a cooler surface temperature at the subsolar point. Water ice forms at the polar regions and on the dark side, where the minimum temperature lies between -30°C and 0°C. As expected, rainfall is extremely high on the starlit side and extremely low on the dark side. The presence of a dry continent causes higher temperatures on the dayside, and allows accumulation of snow on the nightside. The absence of any oceans leads to higher day-night temperature differences, consistent with previous work. The present study reinforces recent conclusions that synchronously rotating planets within the circumstellar habitable zones of M dwarf stars should be habitable, and therefore M dwarf systems should not be excluded in future searches for exoplanets. © Mary Ann Liebert, Inc."
"7005631653;","Climatic, environmental and human con sequences of the largest known historic eruption: Tambora volcano (Indonesia) 1815",2003,"10.1191/0309133303pp379ra","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0013113840&doi=10.1191%2f0309133303pp379ra&partnerID=40&md5=7e44a50e847706143c438c4d079542ac","The 1815 eruption of Tambora volcano (Sumbawa island, Indonesia) expelled around 140 gt of magma (equivalent to ≈50 km3 of dense rock), making it the largest known historic eruption. More than 95% by mass of the ejecta was erupted as pyroclastic flows, but 40% by mass of the material in these flows ended up as ash fallout from the 'phoenix' clouds that lofted above the flows during their emplacement. Although they made only a minor contribution to the total magnitude of the eruption, the short-lived plinian explosions that preceded the climactic eruption and caldera collapse were powerful, propelling plumes up to 43 km altitude. Over 71 000 people died during, or in the aftermath of, the eruption, on Sumbawa and the neighbouring island of Lombok. The eruption injected ≈60 mt of sulfur into the stratosphere, six times more than was released by the 1991 Pinatubo eruption. This formed a global sulfate aerosol veil in the stratosphere, which resulted in pronounced climate perturbations. Anomalously cold weather hit the northeastern USA, maritime provinces of Canada, and Europe the following year. 1816 came to be known as the 'Year without a summer' in these regions. Crop failures were widespread and the eruption has been implicated in accelerated emigration from New England, and widespread outbreaks of epidemic typhus. These events provide important insights into the volcanic forcing of climate, and the global risk of future eruptions on this scale."
"7003785403;7101833247;55206018900;55424975000;57217271893;","Explicit representation of subgrid heterogeneity in a GCM land surface scheme",2003,"10.1175/1525-7541(2003)004<0530:EROSHI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038287088&doi=10.1175%2f1525-7541%282003%29004%3c0530%3aEROSHI%3e2.0.CO%3b2&partnerID=40&md5=84823f5c822ce14a64712006600d47a5","A land surface scheme that may be run with or without a tiled representation of subgrid heterogeneity and includes an implicit atmospheric coupling scheme is described. Simulated average surface air temperatures and diurnal temperature ranges in a GCM using this surface model are compared with climatology. Surface tiling is not found to give a clear improvement in the simulated climate but offers more flexibility in the representation of heterogeneous land surface processes. Using the same meteorological forcing in offline simulations using versions of the surface model with and without tiling, the tiled model gives slightly lower winter temperatures at high latitudes and higher summer temperatures at midlatitudes. When the surface model is coupled to a GCM, reduced evaporation in the tiled version leads to changes in cloud cover and radiation at the surface that enhance these differences."
"7005675320;57201387751;6701778248;7004694114;","Distribution of organochlorine pesticides in pine needles of an oceanic island: The case of tenerife (Canary islands, Spain)",2003,"10.1023/A:1023906306701","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037667755&doi=10.1023%2fA%3a1023906306701&partnerID=40&md5=9cf2c76feb097817076580a9698c85bd","The distribution of persistent organochlorine pesticides (HCB, HCH, DDT and its metabolites) was studied by analyzing pine needles in the oceanic island of Tenerife (Canary Islands, Spain). Tenerife is a subtropical oceanic island, characterized by the presence of a high mountain (Pico de Teide, 3,718 m a.s.l.) and by a peculiar climatic condition. The southern side is warm and sometimes during the year influenced by dry winds coming from Africa, while the northern side is cool and wet, with an almost persistent cloudiness (called 'mar de nubes), due to winds coming from the northern Atlantic. Furthermore a developed agricultural area is present at sea level. Pine needle samples were collected on both sides of the island, from the sea level up to the upper level of pine distribution (2,100 m a.s.l.). The distribution patterns of organochlorine pesticides seem to be affected mainly by local emissions. Up to the considered altitude layer, the influence of global circulation of persistent organic pollutants seems to play a negligible role. The behavior of chemicals is consistent with their physical-chemical properties, with some influence due to climatic conditions."
"7006018872;7005626683;7006204393;7202776785;35375959000;7101798907;","Time correlations and 1/f behavior in backscattering radar reflectivity measurements from cirrus cloud ice fluctuations",2003,"10.1029/2002jd003000","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346639339&doi=10.1029%2f2002jd003000&partnerID=40&md5=1f7dd239fb3e890a1b8c61e51483390b","The state of the atmosphere is governed by the classical laws of fluid motion and exhibits correlations in various spatial and temporal scales. These correlations are crucial to understand the short- and long-term trends in climate. Cirrus clouds are important ingredients of the atmospheric boundary layer. To improve future parameterization of cirrus clouds in climate models, it is important to understand the cloud properties and how they change within the cloud. We study correlations in the fluctuations of radar signals obtained at isodepths of winter and fall cirrus clouds. In particular, we focus on three quantities: (1) the backscattering cross-section, (2) the Doppler velocity, and (3) the Doppler spectral width. They correspond to the physical coefficients used in Navier Stokes equations to describe flows, i.e., bulk modulus, viscosity, and thermal conductivity. In all cases we find that power law time correlations exist with a crossover between regimes at about 3 to 5 min. We also find that different type of correlations, including 1/f behavior, characterize the top and the bottom layers and the bulk of the clouds. The underlying mechanisms for such correlations are suggested to originate in ice nucleation and crystal growth processes."
"7004885872;","Measurement of the timescale of hygroscopic growth for atmospheric aerosols",2003,"10.1029/2002jd002757","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346639340&doi=10.1029%2f2002jd002757&partnerID=40&md5=27f565a3419b86a9b6c6d95d9723550b","The rate of condensational growth is relevant to a variety of atmospheric processes, in particular the activation of cloud condensation nuclei to form cloud droplets. It has been hypothesized that the presence of organic films on the surface of aerosols can strongly inhibit condensational growth, but few relevant observations of atmospheric aerosol growth rates appear to have been previously reported. A brief review of the literature on the effects of films on the mass transfer of water is presented. A novel experiment based on tandem differential mobility analysis for the measurement of the timescale for condensational growth (τg) for ambient aerosols is introduced. Measurements were taken during the wet season (25-27 September 2000) and dry season (16-17 November 2000) in Mexico City for particles with diameters of 50 and 100 nm. The results show that most of the particles exhibit τg &lt; 2 to 3 s. However, a small number (between 0 and 2.0% depending on particle size and season) do exhibit timescales larger than this. The accommodation coefficient of this minority of particles is estimated to be approximately in the range of 1 to 4 × 10-5, which is in the lowest range of observed values for laboratory aerosols. The observations show a strong dependence of the occurrence of such particles on season and time of day. It is hypothesized that these measurements suggest that an even larger concentration of particles exhibiting accommodation coefficients in the range of 10-5 to 10-4 may exist. The existence of such particles would be important to the indirect effect of aerosols on climate."
"36862677400;7202145115;","Interactions among cloud, water vapor, radiation, and large-scale circulation in the tropical climate. Part I: Sensitivity to uniform sea surface temperature changes",2003,"10.1175/1520-0442-16.10.1425","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038128200&doi=10.1175%2f1520-0442-16.10.1425&partnerID=40&md5=4fd899fd3cb01714efe20d919927dcf8","The responses of tropical clouds and water vapor to SST variations are investigated with simple numerical experiments. The fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model is used with doubly periodic boundary conditions and a uniform constant sea surface temperature (SST). The SST is varied and the equilibrium statistics of cloud properties, water vapor, and circulation at different temperatures are compared. The top of the atmosphere (TOA) radiative fluxes have the same sensitivities to SST as in observations averaged from 20°N to 20°S over the Pacific, suggesting that the model sensitivities are realistic. As the SST increases, the temperature profile approximately follows a moist-adiabatic lapse rate. The rain rate and cloud ice amounts increase with SST. The average relative humidity profile stays approximately constant, but the upper-tropospheric relative humidity increases slightly with SST. The clear-sky mean temperature and water vapor feedbacks have similar magnitudes to each other and opposite signs. The net clear-sky feedback is thus about equal to the lapse rate feedback, which is about -2 W m-2 K-1. The clear-sky outgoing longwave radiation (OLR) thus increases with SST, but the high cloud-top temperature is almost constant with SST, and the high cloud amount increases with SST. The result of these three effects is an increase of cloud longwave forcing with SST and a mean OLR that is almost independent of SST. The high cloud albedo remains almost constant with increasing SST, but the increase in high cloud area causes a negative shortwave cloud radiative forcing feedback, which partly cancels the longwave cloud feedback. The net radiation decreases slightly with SST, giving a small net negative feedback, implying a stable, but very sensitive climate."
"7005171879;7102018821;7401622015;6701324864;","Diurnal effects in the composition of cirrus clouds",2003,"10.1029/2003gl017034","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042784176&doi=10.1029%2f2003gl017034&partnerID=40&md5=d1fae593bb66cdd9bc9e181ac3f42711","Extended (7-y) polarization lidar data, which are sensitive to ice crystal shape and orientation, are used to search for diurnal changes in cirrus clouds caused by solar heating. Average linear depolarization ratios are ∼0.02 lower during the day than night, minimizing at a 45° sun angle at ∼0.05 lower than the 0.350 nighttime average. Analysis of the diurnal pattern using scattering simulations suggests that plate crystals are more common during daylight, and that a feedback occurs between solar heating and the maintenance of horizontal plate orientations. This anisotropy also affects the cirrus solar albedo, representing an additional complication confronting climate modelers."
"36862677400;7202145115;","Interactions among cloud, water vapor, radiation, and large-scale circulation in the tropical climate. Part II: Sensitivity to spatial gradients of sea surface temperature",2003,"10.1175/1520-0442-16.10.1441","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038467220&doi=10.1175%2f1520-0442-16.10.1441&partnerID=40&md5=0d094d46996187e46218244188c3a100","The responses of the large-scale circulation, clouds, and water vapor to an imposed sea surface temperature (SST) gradient are investigated. Simulations compare reasonably to averaged observations over the Pacific, considering the simplifications applied to the model. The model responses to sinusoidal SST patterns have distinct circulations in the upper and lower troposphere. The upper circulation is sensitive to the heating from deep convection over the warmest SST. Stronger SST gradients are associated with stronger longwave cooling above stratus clouds in the subsidence region, stronger lower-tropospheric large-scale circulation, a reduction of the rain area, and larger area coverage of low clouds. A similar SST gradient with a warmer mean temperature produces slightly weaker lower-tropospheric circulation, and slightly reduced low cloud coverage. The outgoing longwave radiation (OLR) is not sensitive to the mean SST or the range of the imposed sinusoidal SST gradient. The positive feedbacks of water vapor and decreasing high cloud OLR compensate for the increase in longwave emission with increasing mean temperature in these simulations. As the SST gradient is increased keeping the mean SST constant, the positive high cloud feedback is still active, but the air temperature increases in proportion to the maximum SST in the domain, increasing the clear-sky OLR value and keeping the average OLR constant. The net absorbed shortwave radiation (SWI) is found to be extremely sensitive to the SST gradient. The stronger lower-tropospheric large-scale circulation produces a higher water content in the high and low clouds, increasing the absolute magnitude of the shortwave cloud forcing. A 25% increase in the maximum zonal mass flux of the lower circulation of the 300-K mean, 4-K SST range simulation leads to a 7.4 W m-2 decrease in SWI. Increasing the mean SST creates a positive feedback in these simulations because of the decrease in the lower-tropospheric large-scale circulation and the resultant decrease in cloud optical depth."
"6506553288;7407663727;","Global and regional diurnal variations of organized convection",2003,"10.1175/1520-0442-16.10.1562","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037929480&doi=10.1175%2f1520-0442-16.10.1562&partnerID=40&md5=0f36b668b66cccc13fb8fce579a4b293","An automated objective classification procedure, the Convection Classification and Automated Tracking System (CCATS), is used to analyze the mean life cycles of organized convection in the global Tropics and midlatitudes (40°N-40°S). Five years (1989-93) of infrared satellite imagery are examined for the Pacific and Atlantic basins and one year (April 1988-March 1989) is studied for the Indian basin. Two main classes of organized convection (lifetime of 6 h or more) are tracked: MCT and CCC. MCT represent a combined dataset of tropical cyclones and mesoscale convective complexes (MCC). Convective cloud clusters (CCC) meet the same cold cloud-top temperature, time, and size criteria used to distinguish MCC, but fail to sustain the same high degree of symmetry for at least 6 h. That is, CCC represent more elongated systems, such as squall lines. The frequency of CCC exceeds that of MCT by a factor of 30 over both land and sea. MCT and CCC are each stratified to into 12 continental and oceanic regions and the diurnal variation of system characteristics in each geographic region are studied, leading to composite life cycle descriptions for each region. Oceanic CCC formed overnight and the shorter-lived, land-based CCC formed in the afternoon; apart from this time offset, oceanic and land-based CCC were found to have very similar life cycle evolution patterns. Continental MCT exhibit a rapid size expansion early: this is not part of the oceanic system life cycle. Apart from this growth spurt, the evolution of land and ocean MCT follows the same pattern of CCC with early symmetry, then size expansion until just before termination. Land-based MCT are longer lived and more symmetric than oceanic MCT."
"7406228987;7404165290;24423610300;","Relationship of the Arctic and Antarctic Oscillations to the outgoing longwave radiation",2003,"10.1175/1520-0442-16.10.1583","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038266819&doi=10.1175%2f1520-0442-16.10.1583&partnerID=40&md5=44ada140c0db5978067bff07aebfc5f9","While several mechanisms have been suggested to account for the association of the Arctic and Antarctic Oscillations (AO/AAO) with atmospheric parameters, this paper focuses on the relationship with the atmospheric outgoing longwave radiation (OLR). The main objective of this paper is to demonstrate through AO/AAO composite analysis that the NCEP-NCAR reanalysis OLR agrees with the independent observations of the NASA Earth Radiation Budget Experiment (ERBE) broadband satellite instruments both in zonal averages and in geographically mapped space, and to verify AO/AAO characterized general circulations derived from models and analyses. The results indicate several pronounced areas of storminess that are AO/AAO dependent. One is the well-known variation over the North Atlantic Ocean toward Europe. Also, several major areas are indicated in the tropical region-one in the Indian Ocean and the others in the west and central Pacific Ocean. In addition to demonstrating that the signals are statistically significant, also tested is the relationship of the features to other well-known tropical forcing mechanisms: the Madden-Julian oscillation (MJO) and the El Niño-La Niña sea surface temperature variations. It is shown that the tropical features do, in fact, have a strong relationship to the MJO, which indicates an additional tropical-extratropical interaction. With regard to the sea surface temperature, no correlation associated with the AO/AAO variability is seen. These associations with the cloudiness and atmospheric radiation budget suggest that if there is to be improvement of numerical model forecasts to an extended time period that numerical model radiation physics will have to be taken into consideration and improved."
"7201443624;6504825610;","Inconsistencies between satellite estimates of longwave cloud forcing and dynamical fields from reanalyses",2003,"10.1029/2003GL017019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042740431&doi=10.1029%2f2003GL017019&partnerID=40&md5=f5e7d93098c9f900f185612d438edff9","The greenhouse effect of cloud may be quantified as the difference between outgoing longwave radiation (OLR) and its clear-sky component (OLRc). Clear-sky measurements from satellite preferentially sample drier, more stable conditions relative to the monthly-mean state. The resulting observational bias is evident when OLRc is stratified by vertical motion; differences to climate model OLRc of 15 Wm-2 occur over warm regions of strong ascent. Using data from the ECMWF 40-year reanalysis, an estimate of cloud longwave radiative effect is made which is directly comparable with standard climate model diagnostics. The impact of this methodology on the cancellation of cloud longwave and shortwave radiative forcing in the tropics is estimated."
"6603711967;6507011962;","Mineral aerosol and cloud interactions",2003,"10.1029/2002GL016762","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0041738955&doi=10.1029%2f2002GL016762&partnerID=40&md5=f69e361c306e0b7b9886681e8310ce4e","Interactions between aerosols and clouds are the subject of considerable scientific research, due to the importance of clouds in controlling climate. Here we consider the relationship between mineral aerosols and cloud properties over North Africa and the North Atlantic using monthly mean observations of mineral aerosols and clouds over 16 years. The results of this study are consistent with mineral aerosols suppressing precipitation in thin low altitude clouds and changing cloud amounts in ice phase clouds. Because we cannot eliminate either spurious correlations, or that the cloud and dust changes are both driven by the same meteorological conditions, we cannot provide definitive conclusions. However, these results suggest complicated and tantalizing feedbacks between mineral aerosols and climate. This question becomes crucial as we note that mineral aerosols from North Africa have increased substantially since the 1960s for reasons which are poorly understood but that may be linked to human activity."
"56501802200;7102692123;7101830914;7004107599;6507272055;7003501762;","In-situ formation of light-absorbing organic matter in cloud water",2003,"10.1023/A:1024060428172","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038236738&doi=10.1023%2fA%3a1024060428172&partnerID=40&md5=2dba2b211159be13f5c6b4034b70f39c","Current climate models seem to underestimate the flux of solar energy absorbed by the global troposphere. All of these models are constrained with the assumption that cloud droplets consist of pure water. Here we demonstrate in a simple laboratory experiment that aromatic hydroxyacids which are found in continental fine aerosol can react with hydroxyl radicals under typical conditions prevalent in cloud water influenced by biomass burning. The reactions yield colored organic species which do absorb solar radiation. We also suggest that the products of such reactions may be humic-like substances whose presence in continental aerosol has been confirmed but their source mechanisms are still much sought after. We also attempt to give a first order estimate of the enhancement of water absorption at a visible wavelength under atmospheric conditions."
"7004854393;7202326662;7003495982;6701764745;","Evaluating mesoscale model predictions of clouds and radiation with SGP ARM data over a seasonal timescale",2003,"10.1175/1520-0493(2003)131<0926:EMMPOC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037645912&doi=10.1175%2f1520-0493%282003%29131%3c0926%3aEMMPOC%3e2.0.CO%3b2&partnerID=40&md5=62f3da208c72318172832034016b68c7","This study evaluates the predictions of radiative and cloud-related processes of the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model (MM5). It is based on extensive comparison of three-dimensional forecast runs with local data from the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site collected at the Central Facility in Lamont, Oklahoma, over a seasonal timescale. Time series are built from simulations performed every day from 15 April to 23 June 1998 with a 10-km horizontal resolution. For the one single column centered on this site, a reasonable agreement is found between observed and simulated precipitation and surface fields time series. Indeed, the model is able to reproduce the timing and vertical extent of most major cloudy events, as revealed by radiative flux measurements, radar, and lidar data. The model encounters more difficulty with the prediction of cirrus and shallow clouds whereas deeper and long-lasting systems are much better captured. Day-to-day fluctuations of surface radiative fluxes, mostly explained by cloud cover changes, are similar in simulations and observations. Nevertheless, systematic differences have been identified. The downward longwave flux is overestimated under moist clear sky conditions. It is shown that the bias disappears with more sophisticated parameterizations such as Rapid Radiative Transfer Model (RRTM) and Community Climate Model, version 2 (CCM2) radiation schemes. The radiative impact of aerosols, not taken into account by the model, explains some of the discrepancies found under clear sky conditions. The differences, small compared to the short timescale variability, can reach up to 30 W m-2 on a 24-h timescale. Overall, these results contribute to strengthen confidence in the realism of mesoscale forecast simulations. They also point out model weaknesses that may affect regional climate simulations: representation of low clouds, cirrus, and aerosols. Yet, the results suggest that these finescale simulations are appropriate for investigating parameterizations of cloud microphysics and radiative properties, as cloud timing and vertical extension are both reasonably captured."
"6701762451;7004715270;7005284577;57192107995;6603405398;7005968859;6603385031;57213019449;7202586843;7404062492;","A method for single particle mass spectrometry of ice nuclei",2003,"10.1080/02786820300976","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242684713&doi=10.1080%2f02786820300976&partnerID=40&md5=9996d31bfdcced9f980ffd2a2c6046d8","High altitude cirrus clouds play an important role in the terrestrial radiation budget. Cirrus clouds are composed of ice particles that generally form on only a small subset, from 1 in 10 to 1 in 105, of the background aerosol. Ice particles may form due to the homogeneous freezing of aqueous aerosols or by the action of heterogeneous ice nuclei (IN). IN possess the ability to form ice at a higher temperature for a given vapor pressure of water than is required for homogeneous freezing. Apart from a few studies of refractory components, the chemical composition of these climatically important particles remains largely unknown. Almost nothing has been reported about the semivolatile and volatile components of IN. One of the principal reasons is that collection of cirrus precursors ideally should take place immediately after ice formation, before significant alteration of the crystals due to particle and gas-phase scavenging. Here we describe a method to measure the concentration and activation conditions of aerosols by exposure to temperatures and relative humidities (RH) similar to those that initiate cirrus cloud formation in the atmosphere. Laser mass spectrometry was subsequently used to investigate only those particles that nucleated ice. With this technique we were able to differentiate particles known to act as IN from those that entered the ice phase homogeneously. Deployment to study aerosol effects on ice formation in cirrus clouds is presented, although this method is applicable to the entire tropospheric mixed-phase and ice-phase regimes."
"6601977242;","Ocean radiant heating in climate models",2003,"10.1175/1520-0442-16.9.1337","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038606805&doi=10.1175%2f1520-0442-16.9.1337&partnerID=40&md5=40b05c1f223f5946ed32e7d9f1a64bc5","A computationally simple, double exponential, chlorophyll-dependent solar transmission parameterization for ocean general circulation models used in climate studies is presented. The transmission parameterization comes from empirical fits to a set of in-water solar flux profiles calculated with an atmosphere-ocean radiative transfer model system, run with chlorophyll concentration values over the range observed in oligotrophic, open ocean waters. Transmission parameters are available from a lookup table, or can be written as logarithmic and square root functions of chlorophyll concentration, available globally from remotely sensed ocean color data. The rms and maximum errors introduced by curve fitting are less than 3 × 10-3 and 1.5 × 10-2, respectively. Error associated with neglect of second-order cloud and solar zenith angle influences is mostly a few percent. An extension to account for second-order processes in cases where they are large (&gt;10%) is given. The double exponential form enables solar transmission to be resolved at depths beyond 2 m. Only the first exponential term need be considered to accurately determine transmission at depths greater than 8 m. The transmission parameterization is validated with in situ optical and biological data collected in the eastern equatorial Pacific during the Eastern Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System (EPIC) field program, and in the western equatorial Pacific during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). The rms (maximum) errors between parameterized transmission and the mean transmission profile computed from in situ values are 0.5 (1.5) and 1.9 (6.6) W m-2, for the eastern and western equatorial Pacific regions, respectively. For comparison, rms (maximum) errors between transmission from a commonly used Jerlov water type-based parameterization and mean measured values are 7.3 (26.7) and 5.0 (8.8) W m-2 for the eastern and western Pacific, respectively (both cases assume a climatological surface flux of 200 W m-2). Proper use of the solar transmission parameterization should increase the accuracy of modeled SST and upper ocean stratification. The parameterization allows ocean radiant heating in climate models to be discussed in terms of chlorophyll concentration, the physical parameter on which solar transmission most heavily depends."
"6701404949;7003372165;","Coastal lows along the subtropical West coast of South America: Numerical simulation of a typical case",2003,"10.1175/1520-0493(2003)131<0891:CLATSW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037983847&doi=10.1175%2f1520-0493%282003%29131%3c0891%3aCLATSW%3e2.0.CO%3b2&partnerID=40&md5=7edcb6b61a0b130336b828eb9cf9fd8d","Subsynoptic, warm core low pressure areas are frequently observed along the west coast of subtropical South America during austral winter. These so-called coastal lows (CLs) tend to develop as an upper-air, midlatitude ridge is approaching the subtropical Andes and, therefore, while pressure is increasing aloft and farther to the south. These CLs have a profound impact in the coastal weather associated with a rapid transition from clear skies and stronger than average equatorward low-level flow to overcast conditions and relaxed equatorward (or even poleward) flow. Weather conditions inland mostly reflect the associated changes in the strength and height of the base of the subsidence inversion. In this work, a mesoscale simulation of a typical CL episode is performed using a numerical weather prediction model [the fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5)] Comparison with observations reveals that the model simulation properly captures the large-scale pattern as well as many of the mesoscale features that characterize the CL. The model results were then used to diagnose the CL. It is found that the coastal troughing is largely due to the marked adiabatic warming of the lower troposphere (including a significant strengthening of the temperature inversion). The large-scale subsidence ahead of the incoming upper-air ridge axis is enhanced as the low-level easterly flow is constrained by the western slope of the subtropical Andes. The low-level wind off the subtropical coast is close to geostrophic balance and it is fed by air parcels that 1-2 days before had been located in the middle troposphere over the Pacific Ocean. The easterly flow is set up as the alongshore pressure gradient becomes poleward oriented because of the extratropical ridging. This gradient is further enhanced as the CL develops at subtropical latitudes. As soon as the ridge axis crosses, the low-level easterly flow vanishes and a shallow, narrow tongue of northwesterlies and stratocumulus clouds propagates poleward from northern Chile. Shortly thereafter, the trapped wind reversal merges with the incoming synoptic-scale, tropospheric deep-cyclonic circulation."
"6701670597;7201772478;55703600300;7101736036;","Diurnal patterns of rainfall in northwestern South America. Part I: Observations and context",2003,"10.1175/1520-0493(2003)131<0799:DPORIN>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037983863&doi=10.1175%2f1520-0493%282003%29131%3c0799%3aDPORIN%3e2.0.CO%3b2&partnerID=40&md5=d3d08b563af67057cc93cb763707db6f","One of the rainiest areas on earth, the Panama Bight and Pacific (western) littoral of Colombia, is the focal point for a regional modeling study utilizing the fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5) with nested grids. In this first of three parts, the observed climatology of the region is presented. The seasonal march of rainfall has a northwest-southeast axis, with western Colombia near the center, receiving rain throughout the year. This study focuses on the August-September season. The diurnal cycle of rainfall over land exhibits an afternoon maximum over most of South and Central America, typically composed of relatively small convective cloud systems. Over some large valleys in the Andes, and over Lake Maracaibo, a nocturnal maximum of rainfall is observed. A strong night/morning maximum of rainfall prevails over the coastal ocean, propagating offshore and westward with time. This offshore convection often takes the form of mesoscale convective systems with sizes comparable to the region's coastal concavities and other geographical features. The 10-day period of these model studies (28 August-7 September 1998) is shown to be a period of unusually active weather, but with a time-mean rainfall pattern similar to longer-term climatology. It is concluded that the rain-producing processes during this time period are likely to be typical of those that shape the seasonal climatology."
"7006508549;7103142686;7201914101;35453054300;","Impact of land use on Costa Rican tropical montane cloud forests: Sensitivity of cumulus cloud field characteristics to lowland deforestation",2003,"10.1029/2001jd001135","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346461695&doi=10.1029%2f2001jd001135&partnerID=40&md5=9162992f23633e33d7a03cdee39320b4","Recent studies have shown that there has been a reduction in dry season moisture input from direct interception of cloud water and wind-blown mist at the lee edge of the Monteverde cloud forest, Costa Rica, since the mid 1970s. This reduction of moisture could be responsible for the population crashes of anurans observed in the region. It has been hypothesized that this behavior is a result of increases in cloud base height, linked to increased sea surface temperatures. In this study we present a complementary hypothesis, that deforestation upwind of the Monteverde cloud forest preserve is responsible for the observed changes in cloud base height. An automated cumulus cloud classification scheme extracts monthly spatial maps of the frequency of occurrence of cumulus cloudiness over Costa Rica from GOES 8 visible channel satellite imagery. We find that cumulus cloud formation in the morning hours over deforested regions is suppressed compared to forested areas. The degree of suppression appears to be related to the extent of deforestation. This difference in cloud formation between forested and deforested areas is a clear signal of land use change influencing the regional climate. Regional Atmospheric Modeling System numerical modeling simulations are used to explore the differences in cloud field characteristics over the lowland pasture and forest landscapes. Statistically significant differences in cloud base height and cloud thickness occur between the forest and pasture simulations. Clouds have higher base heights and are thinner over pasture landscapes than over forested ones. On the other hand, these simulations show no statistically significant differences in cloud top heights, cloud cover, mean cloud water mixing ratio, or cloud liquid water path between pasture and forest simulations. However, in the simulations there are enhanced sensible heat fluxes and reduced latent heat fluxes over pasture compared to forest. It is the drier and warmer air over pasture surfaces that results in the formation of elevated thinner clouds. This study suggests that deforestation results in warmer, drier air upwind of the Monteverde cloud forests and that this could influence the base height of orographic cloudbanks crucial to the region during the dry season."
"6505639112;6701832375;7003591311;7202258620;55113736500;55697757300;55717074000;7102604282;6701378450;57196499374;","Modification of aerosol mass and size distribution due to aqueous-phase SO2 oxidation in clouds: Comparisons of several models",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0345975881&partnerID=40&md5=9114b429f958e9eb9a120e8c11d103cf","Models of aerosol scavenging and aqueous-phase oxidation of SO2 by H2O2 and O3 in a cloud updraft are compared. Bulk models considering only a single droplet size are compared with size-resolved models that explicitly simulate multiple aerosol and drop sizes. All models simulate growth of cloud drops on a lognormal ammonium bisulfate aerosol distribution, and subsequent aqueous-phase chemistry during adiabatic ascent. In agreement with earlier published studies, it is found that relative to bulk models, the size-resolved cloud chemical models consistently calculate 2-3 times more oxidation via the SO2 + O3 pathway, due to calculated variability of cloud water pH among cloud drops. All models calculate high scavenging of the input dry aerosol mass, but the calculated number of cloud drops formed varies from 275-358 drops cm-3. Differences in the calculated number of cloud drops formed result from the treatment of gaseous species uptake, solution thermodynamics, applied water condensation mass accommodation coefficient, and bin size range definitions over which the input aerosol distribution is numerically approximated. The difference in calculated cloud drop number can under many conditions propagate to appreciable variations in cloud albedo. It is found that the modifications to the aerosol size and mass spectrum are sensitive to the number of cloud drops formed, and differences in the processed aerosol spectra were found to induce up to 13% differences in calculated light extinction properties of the modified particle distributions. These significant discrepancies among cloud aerosol chemistry interaction models, even when used to simulate relatively simple conditions, suggest that parameterizations of these processes used in larger-scale cloud, regional and longer-term climate models can contain high levels of uncertainty."
"7201796620;7501757094;57208346904;57212815233;","Global and seasonal variations of O3 and NO2 photodissociation rate coefficients",2003,"10.1029/2002jd002760","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346461683&doi=10.1029%2f2002jd002760&partnerID=40&md5=ec068e074431273a56ff0d79df164507","The global and seasonal variations in the photodissociation rate coefficients (J values) of the reactions of ozone forming O(1D) (J(O1D)) and nitrogen dioxide forming O(3P) (J(NO2)) were investigated systematically with a focus on the troposphere. The corresponding mechanisms were studied through sensitivity modeling experiments of temperature, surface albedo, aerosols, ozone column, and clouds. The one-dimensional radiative transfer model PHODIS was applied with Total Ozone Mapping Spectrometer (TOMS) aerosol optical depth and surface reflectivity, observation-based three-dimensional ozone distributions, and other numerically simulated climate variables. Our results showed that under clear-sky conditions, the zonal averaged J(O1D) and J(NO2) peaked in magnitude at 3 × 10-5 and 8 × 10-3 s-1, respectively, in the region of 30°S to 30°N with small latitudinal and vertical variations, and decreased precipitously at 30°/60° in the winter/summer hemisphere. J(O1D) exhibited a large meridional and vertical gradient as a result of high sensitivity to temperature and ozone. The predominant effect of surface albedo led to significant longitudinal variation in J(NO2) and a poleward increase beyond 60° of the summer hemisphere. Surface J(O1D) changes were regressed as a second-degree polynomial function of changes in temperature (±20°K). The impact of low and middle clouds on J values was stronger than high clouds by a factor of 2 to 3 because of thick optical depth. In addition, the cloud-induced changes in J values calculated by PHODIS differed by up to 20% from those parameterized in the Regional Acid Deposition Model (RADM) and Intermediate Model for the Global and Annual Evolution of Species (IMAGES). Regional photochemical model simulations showed that an arbitrary increase/decrease of 20% above/below the cloud base (750 m) in J(O1D) resulted in decreases up to 6% in the ozone concentration below 200 m at noon and late afternoon and increases ubiquitously elsewhere."
"7103159253;6701410484;8839842400;55482223200;16444930500;6504173221;55947319900;","Improved mesospheric temperature, water vapor and polar mesospheric cloud extinctions from HALOE",2003,"10.1029/2002GL016859","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042384959&doi=10.1029%2f2002GL016859&partnerID=40&md5=9ba93a06e6e659c624772b3653c612f8","We present a new retrieval technique for mesospheric measurements from the Halogen Occultation Experiment (HALOE). Previous HALOE retrievals did not account for polar mesospheric clouds (PMCs) and were biased whenever PMCs were in the sample volume. In the new algorithm we eliminate this bias by retrieving and correcting for PMC extinction, and we optimize the algorithm for this region of the atmosphere. We have reprocessed over ten years (1991-2002) of HALOE data with the improved algorithm, yielding nearly 75,000 vertical profiles of temperature, H2O, O3, NO and extinction at five infrared wavelenghts. In this paper we describe the new algorithm in detail, present several examples of the results and discuss some initial validation and quality assessments."
"56962915800;7402944490;7406372329;","Atmosphere-warm ocean interaction and its impacts on Asian-Australian monsoon variation",2003,"10.1175/1520-0442(2003)16<1195:AOIAII>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141857717&doi=10.1175%2f1520-0442%282003%2916%3c1195%3aAOIAII%3e2.0.CO%3b2&partnerID=40&md5=d2ad9f803e2d575f712421d366dc9b04","Asian-Australian monsoon (A-AM) anomalies depend strongly on phases of El Niño (La Niña). Based on this distinctive feature, a method of extended singular Value decomposition analysis was developed to analyze the changing characteristics of A-AM anomalies during El Niño (La Niña) from its development to decay. Two off-equatorial surface anticyclones dominate the A-AM anomalies during an El Niño-one over the south Indian Ocean (SIO) and the other over the western North Pacific (WNP). The SIO anticyclone, which affects climate conditions over the Indian Ocean, eastern Africa, and India, originates during the summer of a growing El Niño, rapidly reaches its peak intensity in fall, and decays when El Niño matures. The WNP anticyclone, on the other hand, forms in fall, attains maximum intensity after El Niño matures, and persists through the subsequent spring and summer, providing a prolonged impact on the WNP and east Asian climate. The monsoon anomalies associated with a La Niña resemble those during an El Niño but with cyclonic anomalies. From the development summer to the decay summer of an El Niño (La Niña), the anomalous sea level pressure, low-level winds, and vertical motion tend to reverse their signs in the equatorial Indian and western Pacific Oceans (10°S-20°N, 40°-160°E . This suggests that the tropospheric biennial oscillation is intimately linked to the turnabouts of El Niño and La Niña. The remote El Niño forcing alone can explain neither the unusual amplification of the SIO anticyclone during a developing El Niño nor the maintenance of the WNP anticyclone during a decaying El Niño. The atmosphere-ocean conditions in the two anticyclone regions are similar, namely, a zonal sea surface temperature (SST) dipole with cold water to the east and warm water to the west of the anticyclone center. These conditions result from positive feedback between the anomalous anticyclone and the SST dipole, which intensifies the coupled mode in the SIO during El Niño growth and maintains the coupled mode in the WNP during El Niño decay. The interactions in the two anticyclone regions share common wind evaporation/entrainment and cloud-radiation feedback processes but they differ with regard to the oceanic dynamics (vertical and horizontal advection and thermocline adjustment by oceanic waves). The outcome of the interactions in both regions, however, depends crucially on the climatological surface winds. The SIO-coupled made is triggered by El Niño-induced subsidence and alongshore winds off the coast of Sumatra. However, other independent El Niño local and remote forcing can also trigger this coupled mode. The traditional view has regarded SST anomalies in the Indian and western Pacific Oceans as causing the A-AM variability. The present analysis suggests that the SST anomalies in these warm ocean regions are, to a large extent, a result of anomalous monsoons. Thus, the atmosphere-warm ocean interaction may significantly modify the impacts of remote El Niño forcing and should be regarded as one of the physical factors that determine the variability of the A-AM. During the summer at El Niño development, the remote El Niño forcing plays a major role in the A-AM anomalies that exhibit obvious equatorial asymmetry. A tilted anticyclonic ridge originates in the Maritime Continent and extends to southern India, weakening the Indian monsoon while strengthening the WNP monsoon. Numerical modeling experiments suggest that the mean monsoon circulation enhances the equatorial Rossby wave response in the easterly vertical shear region of the Northern Hemisphere and creates the equatorial asymmetry."
"7202208382;7103119050;7004479957;7202162685;7003371535;7006095466;7101945366;7006423931;16441664100;7004540083;6603422104;7004325649;","Confronting models with data: The GEWEX cloud systems study",2003,"10.1175/BAMS-84-4-455","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037692715&doi=10.1175%2fBAMS-84-4-455&partnerID=40&md5=cd2090ddc6527560f3d2d6559e7634ef","The Global Energy and Water Cycle Experiment (GEWEX) Cloud System Study (GCSS) was organized to promote the development of improved parameterizations of cloud systems for use in climate and numerical weather prediction models, with an emphasis on the climate applications. GCSS uses models to analyze and understand observations of the behavior of cloud systems. Cloud-system-resolving models (CSRMs) have sufficient spatial and temporal resolution to represent individual cloud elements, but cover a wide enough range of time and space scales to permit statistical analysis of simulated cloud systems. Results from CSRMs are compared with detailed observations, representing specific cases based on field experiments, and also with statistical composites obtained from satellite and meteorological analyses. Single-column models (SCMs) are the column physics components of atmospheric general circulation models (GCMs). SCMs are used to test cloud parameterizations in an uncoupled mode, by comparison with field data and statistical composites. In the original GCSS strategy, data are collected in various field programs and provided to the CSRM community, which first uses the data to ""certify"" the CSRMs as reliable tools for the simulation of particular cloud regimes, and then uses the CSRMs to develop parameterizations, which are provided to the GCM community. Results of a rethinking of the scientific strategy of GCSS, which takes into account the practical issues that arise in confronting models with data, are reported on herein. The main elements of the proposed new strategy are a more active role for the large-scale modeling community, an explicit recognition of the importance of data integration, and an increasing use of observed cloud-scale statistics for model evaluations."
"7003280188;56235078800;7403892030;7401555723;34882516100;7404212806;","A simple global carbon and energy coupled cycle model for global warming simulation: Sensitivity to the light saturation effect",2003,"10.1034/j.1600-0889.2003.00035.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037569205&doi=10.1034%2fj.1600-0889.2003.00035.x&partnerID=40&md5=9c0b09f3d9dda005ab78fd103fa61fee","A simple Earth system model, the Four-Spheres Cycle of Energy and Mass (4-SCEM) model, has been developed to simulate global warming due to anthropogenic CO2 emission. The model consists of the Atmosphere-Earth Heat Cycle (AEHC) model, the Four Spheres Carbon Cycle (4-SCC) model, and their feedback processes. The AEHC model is a one-dimensional radiative convective model, which includes the greenhouse effect of CO2 and H2O, and one cloud layer. The 4-SCC model is a box-type carbon cycle model, which includes biospheric CO2 fertilization, vegetation area variation, the vegetation light saturation effect and the HILDA oceanic carbon cycle model. The feedback processes between carbon cycle and climate considered in the model are temperature dependencies of water vapor content, soil decomposition and ocean surface chemistry. The future status of the global carbon cycle and climate was simulated up to the year 2100 based on the ""business as usual"" (IS92a) emission scenario, followed by a linear decline in emissions to zero in the year 2200. The atmospheric CO2 concentration reaches 645 ppmv in 2100 and a peak of 760 ppmv approximately in the year 2170, and becomes a steady state with 600 ppmv. The projected CO2 concentration was lower than those of the past carbon cycle studies, because we included the light saturation effect of vegetation. The sensitivity analysis showed that uncertainties derived from the light saturation effect of vegetation and land use CO2 emissions were the primary cause of uncertainties in projecting future CO2 concentrations. The climate feedback effects showed rather small sensitivities compared with the impacts of those two effects. Satellite-based net primary production trends analyses can somewhat decrease the uncertainty in quantifying CO2 emissions due to land use changes. On the other hand, as the estimated parameter in vegetation light saturation was poorly constrained, we have to quantify and constrain the effect more accurately."
"7201993533;8832546900;7004414913;7403544649;57201282288;35426110900;8733292100;7004065709;7102392374;8842994000;","Stratospheric ozone loss over Eureka in 1999/2000 observed with ECC ozonesondes",2003,"10.2151/jmsj.81.295","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042848648&doi=10.2151%2fjmsj.81.295&partnerID=40&md5=49e0b96487dccdbfafc3b2ced2448627","In 1999/2000, as many as 51 Electrochemical Concentration Cell (ECC) ozonesondes were launched from December to March at the Canadian Arctic Eureka observatory (80°N, 86°W), one of the most northern stations in the Arctic, and the temporal evolution of the vertical ozone profiles was obtained in detail. During the winter, monthly average total ozone and temperature at 50 hPa, both observed with the ECC ozonesondes, were substantially lower than normal over Eureka since 1993. From December to March, Eureka was most of the time inside the polar vortex in the lower stratosphere (475 K isentropic surface level), except for early March. When Eureka was inside the polar vortex, very low temperatures were observed in the lower stratosphere, in accordance with the detection of Polar Stratospheric Clouds (PSCs) by Mie lidar between the 17 and 22 km level in January. However, PSCs were not observed over Eureka around the same altitude in February. Together with the observations of large HNO3-containing particles by the ER-2, and depleted HNO3 by the UARS Microwave Limb Sounder, the lidar observations suggest the denitrification in the lower stratosphere in late winter inside the vortex. Under these conditions, the intravortex ozone mixing ratio on the 475 K isentrope decreased by about 2.2 ppmv from 3.1 ppmv on the 497 K isentrope (4 February), to 0.9 ppmv on the 475 K isentrope (29 March) in late winter to early spring, following the diabatic descent. In this period, the loss rate inside the vortex was found to be 0.041 ± 0.008 ppmv/day (90% confidence interval). These findings and results are consistent with other observations (THESEO 2000/SOLVE campaign), and suggest that significant chemical ozone loss did occur in the lower stratosphere inside the polar vortex during the winter of 1999/2000."
"7102834404;6602940714;","Galactic cosmic ray and El Niño-Southern Oscillation trends in International Satellite Cloud Climatology Project D2 low-cloud properties",2003,"10.1029/2001jd001264","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347899468&doi=10.1029%2f2001jd001264&partnerID=40&md5=d9836d00d1a0431f505852c4c4fd857e","The recently reported correlation between clouds and galactic cosmic rays (GCR) implies the existence of a previously unknown process linking solar variability and climate. An analysis of the interannual variability of International Satellite Cloud Climatology Project D2 (ISCCP-D2) low-cloud properties over the period July 1983 to August 1994 suggests that low clouds are statistically related to two processes, (1) GCR and (2) El Niño-Southern Oscillation (ENSO), with GCR explaining a greater percentage of the total variance. Areas where satellites have an unobstructed view of low cloud possess a strong correlation with GCR, which suggests that low-cloud properties observed in these regions are less likely to be contaminated from overlying cloud. The GCR-low cloud correlation cannot easily be explained by internal climate processes, changes in direct solar forcing, or UV-ozone interactions. Instead, it is argued that a mechanism involving solar variability via GCR ionization of the atmosphere is consistent with these results. However, the results are marginal when including the recently extended ISCCP-D2 data covering the period until September 2001. This, we believe, is related to problems experienced with the ISCCP intercalibration between September 1994 and January 1995."
"6506643480;7003430284;7005975931;","Effects of organics of low solubility on the growth rate of cloud droplets",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347899451&partnerID=40&md5=7be5ef809c0aaabfdb1ba700a6f1a335","Organic aerosols represent an important fraction of the fine particle aerosol, yet little is known about the role that these particles play in the indirect effect of aerosols on climate. The growth rates of organic acid particles due to the condensation of water were measured in a cloud condensation nucleus chamber. Delays in the cloud activation of organic acid particles were observed relative to ammonium sulfate, (NH4)2SO4. The inclusion of particle dissolution with time according to its water solubility in a kinetic model of condensational growth of droplets was able to reasonably reproduce the observed delays, indicating that the delays in the growth of the organic acid particles were mainly due to their lower solubilities. Applying the results in an adiabatic simulation of cloud droplet nucleation, the number of cloud droplets nucleated on particles with solubility equivalent to adipic acid were reduced relative to those nucleated on (NH4)2SO4 by up to 85%. The relative solubility of organic species must be considered when simulating the indirect effect of organic aerosol particles."
"7404457584;7004208584;35577912900;56486548700;24755928100;7006708838;56247781100;7402146514;","Consistency of MODIS surface bidirectional reflectance distribution function and albedo retrievals: 1. Validation",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347899456&partnerID=40&md5=984ac179c9748535a2c996b18cab6a04","The evaluation of the first available satellite-based global albedo product at 1-km resolution is essential for its application in climate studies. We evaluate the accuracy of the Moderate-Resolution Imaging Spectroradiometer (MODIS) albedo product using available field measurements at Surface Radiation Budget Network (SURFRAD) and Cloud and Radiation Testbed-Southern Great Plains (CART/SGP) stations and examine the consistency between the MODIS surface albedos and the Clouds and Earth's Radiant Energy System (CERES) top-of-the-atmosphere albedos as well as historical global albedos from advanced very high resolution radiometer (AVHRR) and Earth Radiation Budget Experiment (ERBE) observations. A comparison with the field measurements shows that the MODIS surface albedo generally meets an absolute accuracy requirement of 0.02 for our study sites during April-September 2001, with the root mean square errors less than 0.018. Larger differences appear in the winter season probably due to the increased heterogeneity of surface reflectivity in the presence of snow. To examine the effect of spatial heterogeneity on the validation of the MODIS albedos using fine resolution field measurements, we derive an intermediate albedo product from four Landsat Enhanced Thematic Mapper Plus (ETM+) images at 30-m spatial resolution as a surrogate for the distributed field measurements. The surface albedo is relatively homogeneous over the study stations in growing seasons, and therefore the validation during April-September is supported. A case study over three SURFRAD stations reveals that the MODIS bidirectional reflectance distribution function model is able to capture the solar zenith angle dependence of surface albedo as shown by the field measurements. We also find that the MODIS surface shortwave albedo is consistent with the contemporary and collocated CERES top-of atmosphere albedos derived directly from broadband observations. The MODIS albedo is also well correlated with historical surface albedos derived from AVHRR and ERBE observations, and a high bias of 0.016 and a low bias of 0.034 compared to those of the latter albedos are reasonable considering the differences in instruments and retrieval algorithms as well as environmental changes."
"7801654745;7005156578;6603757377;","The contribution of increased incoming shortwave radiation to the retreat of the Rwenzori glaciers, East Africa, during the 20th century",2003,"10.1002/joc.877","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037444075&doi=10.1002%2fjoc.877&partnerID=40&md5=eae0765212c4e3b8e329b7962c7167e8","Based on (i) the observation of spatially differential glacier retreats in the tropical Rwenzori Range (East Africa) during the 20th century, which are most striking on the mountains Baker and Speke, and (ii) the information on an abrupt climate change to drier conditions in East Africa at the end of the 19th century, the following hypothesis is derived: owing to a drier atmosphere than in a previous period, both accumulation (possibly supported by increasing air temperatures) and convective cloud activity have decreased. Consequently, increased incoming shortwave radiation, especially during the morning hours, induced a differentially increased ablation that could not be compensated by mass advection on the mountains Baker and Speke. The results obtained from a combined radiation-terrain model, run for one more humid and one drier climatic scenario, confirm the hypothesis by quantifying the correlation between increased incoming shortwave radiation and glacier surface area loss. In the context of modern climate fluctuations, the results are a further indicator for a drastic climatic dislocation in East Africa at the end of the 19th century, leaving a humid regime behind and leading to a relatively dry regime, which is forcing the recession of glaciers not only by less accumulation but also by less protection against shortwave radiation through clouds. © 2003 Royal Meteorological Society."
"57211106013;57196499374;","Disproportionate impact of particulate emissions on global cloud condensation nuclei concentrations",2003,"10.1029/2002gl016303","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042701606&doi=10.1029%2f2002gl016303&partnerID=40&md5=b8438ffb5b1ad85eb01ee4e736b97d9c","Estimates of indirect aerosol radiative forcing have focused on increased sulfate aerosol mass concentrations caused by anthropogenic emissions of gas-phase sulfur dioxide, implicitly neglecting the impact of direct particulate emissions. Emissions of primary particles and gas-phase precursors have different effects on cloud condensation nuclei (CCN) concentrations as they impact CCN concentrations via different microphysical pathways. We present a theoretical analysis and evidence from a three-dimensional global model of aerosol microphysics to show that particulate emissions are more efficient per unit mass than gas-phase emissions at increasing CCN concentrations. Both analyses show that the few percent of anthropogenic sulfur emitted as particulate sulfate results in an increase in CCN concentrations comparable to that resulting from much larger emissions of gas-phase sulfur dioxide. Therefore, models should explicitly distinguish between the microphysical impacts of particulate and gas-phase emissions to accurately estimate the magnitude of the indirect effect of aerosols on climate."
"7102128820;7007114756;","Parameterizing ice cloud inhomogeneity and the overlap of inhomogeneities using cloud radar data",2003,"10.1175/1520-0469(2003)060<0756:PICIAT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0142189853&doi=10.1175%2f1520-0469%282003%29060%3c0756%3aPICIAT%3e2.0.CO%3b2&partnerID=40&md5=ac3badde460d19e14c32f791a221d2ad","Cloud variability on scales smaller than the gridbox size of numerical forecast and climate models is believed to be important in determining the radiative effects of clouds, and increasingly attempts are being made to parameterize these fluctuations in the radiation schemes of current models. In order to calculate the radiative effects of an inhomogeneous cloud, a model needs to know not only the degree of variability within a gridbox but also the degree to which the inhomogeneities in vertically adjacent levels are overlapped. In this paper these two parameters are derived for ice clouds from an 18-month midlatitude 94-GHz cloud radar dataset and parameterized in terms of horizontal gridbox size (d), the vertical shear of the horizontal wind (s), and the vertical position in the cloud. The vertical decorrelation length Δz0 (i.e., the depth over which the correlation coefficient of either ice water content or optical extinction coefficient in separate vertical levels falls to e-1) is found to be well represented in the mean by log10Δz0 = 0.3 log10d - 0.031s - 0.315, where Δz0 and d are in kilometers and s is in meters per second per kilometer. As expected, higher shear results in more rapid decorrelation, although the rms deviation from this expression is around a factor of 2.5. It is found that the probability distribution of ice water content within a gridbox is usually well represented by a lognormal or gamma distribution. The fractional variance in ice water content (f1wc) may be expressed to within a factor of 2 by log10f1wc = 0.3 log10d - 0.04s - 0.93, valid for d &lt; 60 km, above which f1wc is constant with increasing d. The expression for the fractional variance of visible extinction coefficient is the same except with the -0.93 term replaced by -0.96. The s dependence indicates a tendency for increased shear to result in decreased cloud variability. This can be explained by the presence of ice fallstreaks in a sheared flow: a parcel of air in the middle of a cloud is alternately fed from above by ice-rich and ice-poor air, resulting in a homogenization of the layer at a rate dependent on the shear. A more complicated formula is derived to express the dependence of f1wc on the vertical position within the cloud; it is found that fractional variance tends to be largest at cloud top and decreases into the interior before increasing again in the lowest third of the cloud. Thicker clouds tend to have lower fractional variance. No significant dependence on temperature or absolute altitude was found for either f1wc or Δz0. © 2003 American Meteorological Society."
"7007173443;56236783400;6506514896;7003816068;","First measurements of tropospheric aerosol profiles above Durban using a LIDAR",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038610954&partnerID=40&md5=e630898636b790ff609c5d40a7d80165","The importance of aerosols in influencing the earth's climate is well recognized. In this study we investigated the vertical distribution of aerosols over Durban based on LIDAR measurements taken on six cloud-free days between July and October 1997. The aerosol loading in the lower troposphere (<5 km) varied between 100 and 320 photon counts and was characterized by marked stratification. Peaks occurred in the intervening layers between shallow stable layers that inhibited vertical mixing. A marked discontinuity, which coincided with the presence of a persistent and ubiquitous stable layer over southern Africa, occurred at 5 km, where aerosol concentrations dropped to zero. Above 5 km, concentrations increased slightly but remained below values recorded in the lower troposphere. The discontinuity in aerosol loading at 5 km marks the top of the haze layer, which is commonly observed over South Africa, particularly in winter. The vertical distribution of aerosols changed dramatically as a function of synoptic weather patterns. Anticyclonic circulation over the subcontinent was associated with high aerosol loadings, whereas the passage of a mid-latitude westerly wave cleansed the atmosphere and was associated with photon counts below 50 throughout the troposphere."
"57203048908;7003303148;","Global measurement of sea surface temperature from space: Some new perspectives",2003,"10.1080/1023673031000080385","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0043195265&doi=10.1080%2f1023673031000080385&partnerID=40&md5=f20f04fa8bc95c38ba22bd5cb3c89de3","The measurement of global sea surface temperature (SST) from space is well established with 20 years of useful data already acquired, but the more stringent sampling requirements and the higher degree of accuracy now demanded for applications in both climate monitoring and operational oceanography are increasingly difficult to meet with the standard meteorological polar orbiting sensors that have been the basic sensors used for global SST mapping. The established methods and sensors for measuring SST, both in situ and in space, are reviewed, compared, and their major limitations are identified. Mention is made of phenomena which complicate an apparently simple measurement, including diurnal stratification, the presence of clouds and the contamination of the stratosphere by volcanic aerosols. Recent developments in remote sensing of SST are mentioned, noting the improved microwave sensors now becoming available, the calibrated infrared sensors planned for geostationary platforms, and weighing the benefits of merging these data. The conventional buoy-calibration of SST measurements from space is complicated by the variable thermal structure of the upper few metres of the ocean. The recent improvement of radiometers for ship deployment has led to better understanding of the thermal skin of the ocean which suggests a new approach for the validation of SST algorithms based on radiation transfer models. Finally, a future strategy is outlined for combining measurements from many types of sensor in order to achieve the required accuracy and sampling rate of SST data products. and to identify some of the remaining scientific challenges in this field."
"6603079729;","New satellite sensor and method for the direct measurement of the planetary albedo, results for 1999, 2000 and 2001 in South America",2003,"10.1016/S0169-8095(02)00157-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037374361&doi=10.1016%2fS0169-8095%2802%2900157-6&partnerID=40&md5=d7eb29c883377c54ece13fa27bc8323f","The second satellite of the Brazilian Complete Space Mission (SCD2/MECB) was launched on October 23, 1998 and it hosts a solar cell experiment. The solar cell senses visible radiation (400-1100 nm) and permits the simultaneous inference of direct insolation and the insolation that is reflected outside of the earth. The global albedo is obtained using the ratio between these two values after spherical angular corrections. The SCD2 has a circular orbit 750 km high and its spin is 35 rpm. The solar cell data are transmitted in real-time and received by the ground station of Cuiabá, MT-Brazil (16°S, 56°W), which limits their spatial coverage to South America. The albedo data can be grouped in periods of time (annual, seasonal or monthly) or studied for several places during the orbit time. A new method to obtain the planetary albedo is tested through a numerical simulation using the data (cloud and land area) extracted from a GOES image. The solar cell experiment albedo values are shown as a function of SCD2 satellite orbit time to six local in South America. The values are in the range between 6% and 68%. The statistic analysis of the main values (minimum, maximum, mean and deviation) is done for 1999, 2000 and 2001. The results show several climate characteristics. For example, Recife-PE (8°S, 35°W) has good weather nearly all-year round. São Paulo (24°S, 47°W), in contrast, is famous for weather instability, with temperatures governed by cold fronts that come suddenly from the south. The described method for evaluating the planetary albedo of the earth starts from a simple and relatively inexpensive experiment and does not rely upon sensor calibration because the measure is self-calibrated by the simultaneous reading of both irradiation peaks, namely, from the sun and its reflection by the earth, during each spin of the satellite. © 2002 Elsevier Science B.V. All rights reserved."
"8600097900;6701606453;7202899330;","The impact of explicit cloud boundary information on ice cloud microphysical property retrievals from infrared radiances",2003,"10.1029/2002jd002611","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0043035582&doi=10.1029%2f2002jd002611&partnerID=40&md5=2a42acc11336c443afa957e2d7ffcec9","Cirrus clouds have a profound impact on the radiation balance of the Earth-atmosphere system. Accurate representation of their radiative properties is critical to understanding climate and predicting climate change. This paper casts the split-window cirrus cloud retrieval technique in an optimal estimation framework facilitating direct inclusion of explicit cloud boundary information from complementary sensors as well as providing a suite of diagnostic tools for evaluating the dominant sources of uncertainty in all retrieved quantities. Errors in retrieved microphysical properties are used to determine the resulting errors in the calculation of global-scale radiative budgets. Uncertainties in optical depth and effective radius are found to diminish from ∼45% and ∼80%, respectively, in the absence of explicit cloud boundary information to ∼15% and ∼60% when accurate radar-based or lidar-based estimates are included. It is demonstrated that the improvements to cirrus cloud optical properties afforded by accurate cloud boundary information may lead to as much as a factor of 3 increase in the accuracy to which their impact on the Earth's radiative balance can be modeled. Colocated infrared radiances from the Moderate-Resolution Imaging Spectroradiometer (MODIS) instrument aboard the Earth Observing System (EOS) Aqua satellite and cloud radar observations from the CloudSat satellite will soon allow the retrieval presented here to be integrated into an operational retrieval of the vertical distribution of cloud properties on a global scale."
"8068314800;26643408200;7005399437;7003364719;7103082408;","Validation of two-channel VIRS retrievals of aerosol optical thickness over ocean and quantitative evaluation of the impact from potential subpixel cloud contamination and surface wind effect",2003,"10.1029/2002jd002346","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642578944&doi=10.1029%2f2002jd002346&partnerID=40&md5=44fb91217c05d41670f32e7d44067705","TRMM/CERES-VIRS Single Satellite Footprint (SSF) data and AERONET Sun/sky radiometer observations from 1998 have been combined to validate SSF aerosol optical thickness (Τ) retrievals over ocean along with a quantitative evaluation of the effects of potential subpixel cloud contamination and surface wind on the satellite Τ retrievals. Potential subpixel cloud contamination is verified in Visible/Infrared Scanner (VIRS) SSF aerosol retrievals and constitutes a major source of systematic and random errors of the retrieval algorithm as determined from comparisons with AERONET observations. A positive correlation between the surface wind speed (which determines the roughness of the ocean surface) and the SSF Τ has been observed for large surface wind speed. The validation results imply this correlation represents the real relationship between the surface wind and the wind-driven aerosols rather than the disturbing effect of the surface reflectance associated with the rough ocean surface. After the potential subpixel cloud contamination is minimized and the effects of large surface wind are removed in the Τ match-ups, the positive biases in the SSF Τ (compared to AERONET Τ) for mean conditions have been reduced from 0.05 to 0.02 in VIRS channel 1 (0.63 μm) and 0.05 to 0.03 in channel 2 (1.61 μm). Random errors have also been reduced from 0.09 to 0.06 at 0.63 μm, and from 0.06 to 0.05 at 1.61 μm. The validation results support the application of the SSF aerosol data in radiation and climate studies as well as supply useful guidance for the adjustment and improvement of the aerosol retrieval algorithm."
"6701346974;7202208382;","Cloud resolving modeling of the ARM summer 1997 IOP: Model formulation, results, uncertainties, and sensitivities",2003,"10.1175/1520-0469(2003)060<0607:CRMOTA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342283059&doi=10.1175%2f1520-0469%282003%29060%3c0607%3aCRMOTA%3e2.0.CO%3b2&partnerID=40&md5=51bce0c05623e942a9dbcd5fcc46fbe5","A new three-dimensional cloud resolving model (CRM) has been developed to study the statistical properties of cumulus convection. The model was applied to simulate a 28-day evolution of clouds over the Atmospheric Radiation Measurement Program (ARM) Southern Great Plains site during the summer 1997 Intensive Observation Period. The model was forced by the large-scale advective tendencies and surface fluxes derived from the observations. The sensitivity of the results to the domain dimensionality and size, horizontal grid resolution, and parameterization of microphysics has been tested. In addition, the sensitivity to perturbed initial conditions has also been tested using a 20-member ensemble of runs. The model captures rather well the observed temporal evolution of the precipitable water and precipitation rate, although it severely underestimates the shaded cloud fraction possibly because of an inability to account for the lateral advection of clouds over the ARM site. The ensemble runs reveal that the uncertainty of the simulated precipitable water due to the fundamental uncertainty of the initial conditions can be as large as 25% of the mean values. Even though the precipitation rates averaged over the whole simulation period were virtually identical among the ensemble members, the timing uncertainty of the onset and reaching the precipitation maximum can be as long as one full day. Despite the predictability limitations, the mean simulation statistics are found to be almost insensitive to the uncertainty of the initial conditions. The overall effects of the third spatial dimension are found to be minor for simulated mean fields and scalar fluxes but are quite considerable for velocity and scalar variances. Neither changes in a rather wide range of the domain size nor the horizontal grid resolution have any significant impact on the simulations. Although a rather strong sensitivity of the mean hydrometeor profiles and, consequently, cloud fraction to the microphysics parameters is found, the effects on the predicted mean temperature and humidity profiles are shown to be modest. It is found that the spread among the time series of the simulated cloud fraction, precipitable water, and surface precipitation rate due to changes in the microphysics parameters is within the uncertainty of the ensemble runs. This suggests that correlation of the CRM simulations to the observed long time series of the aforementioned parameters cannot be generally used to validate the microphysics scheme. © 2003 American Meteorological Society."
"7103399784;23104422600;56981752400;7202298252;6701853567;26643043700;","Intercomparison of heat fluxes in the South Atlantic. Part I: The seasonal cycle",2003,"10.1175/1520-0442(2003)016<0706:IOHFIT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141788144&doi=10.1175%2f1520-0442%282003%29016%3c0706%3aIOHFIT%3e2.0.CO%3b2&partnerID=40&md5=8a33e97f01759d8f106260e6fe468110","Intercomparison of the seasonal cycle for the fluxes of sensible and latent heat for four observation-based products [DaSilva, NCEP, Esbensen-Kushnir (EK), and the Southampton Oceanography Centre (SOC)] and the results for the NCAR Community Climate System Model (CCSM) are examined in order to gain an improved understanding of the South Atlantic characteristic spatial patterns. Their seasonal structure associated with ocean dynamics, evolution, and the net heat flux patterns are also discussed. The key regions of the Brazil-Malvinas confluence, Agulhas retroflection, and Benguela upwelling region off Africa were chosen for a closer examination of the fluxes. All climatologies show very different behavior The SOC product presents sudden changes in the seasonal cycle evolution, departing from the annual or semiannual observed pattern of EK and NCEP. Compared to the other climatologies, EK shows equivalent temporal behavior but different magnitudes because this climatology covers a period where much less data was available. It was found that the eastern Atlantic shows more differences among the climatologies than the Brazil-Malvinas confluence region in the west. It is also in the eastern Atlantic that the difference between NCAR CCSM results and observations are bigger, probably due to a bias in cloud simulation, which affects the air-sea interaction dynamics. In the Brazil-Malvinas confluence region differences between the NCAR CCSM and the observed datasets are comparable to the difference between the observations themselves."
"6603699075;55903834200;7004926126;57208097294;","Potential impact of climate change on marine dimethyl sulfide emissions",2003,"10.1034/j.1600-0889.2003.042.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037330793&doi=10.1034%2fj.1600-0889.2003.042.x&partnerID=40&md5=51bc43454733cebb71a32581453209e9","Dimethyl sulfide (DMS) is a biogenic compound produced in sea-surface water and outgased to the atmosphere. Once in the atmosphere, DMS is a significant source of cloud condensation nuclei in the unpolluted marine atmosphere. It has been postulated that climate may be partly modulated by variations in DMS production through a DMS-cloud condensation nuclei-albedo feedback. We present here a modelled estimation of the response of DMS sea-water concentrations and DMS fluxes to climate change, following previous work on marine DMS modeling (Aumont et al., 2002) and on the global warming impact on marine biology (Bopp et al., 2001). An atmosphere-ocean general circulation model (GCM) was coupled to a marine biogeochemical scheme and used without flux correction to simulate climate response to increased greenhouse gases (a 1% increase per year in atmospheric CO2 until it has doubled). The predicted global distribution of DMS at 1 × CO2 compares reasonably well with observations; however, in the high latitudes, very elevated concentrations of DMS due to spring and summer blooms of Phaeocystis can not be reproduced. At 2 × CO2, the model estimates a small increase of global DMS flux to the atmosphere (+2%) but with large spatial heterogeneities (from -15% to +30% for the zonal mean). Mechanisms affecting DMS fluxes are changes in (1) marine biological productivity, (2) relative abundance of phytoplankton species and (3) wind intensity. The mean DMS flux perturbation we simulate represents a small negative feedback on global warming: however, the large regional changes may significantly impact regional temperature and precipitation patterns."
"7006518289;7005965757;7005591860;6701508272;7005231450;","Solar and greenhouse gas forcing and climate response in the twentieth century",2003,"10.1175/1520-0442(2003)016<0426:SAGGFA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038364313&doi=10.1175%2f1520-0442%282003%29016%3c0426%3aSAGGFA%3e2.0.CO%3b2&partnerID=40&md5=5326a3d63ced728731c69b098147d12a","Ensemble experiments with a global coupled climate model are performed for the twentieth century with time-evolving solar, greenhouse gas, sulfate aerosol (direct effect), and ozone (tropospheric and stratospheric) forcing. Observed global warming in the twentieth century occurred in two periods, one in the early twentieth century from about the early 1900s to the 1940s, and one later in the century from, roughly, the late 1960s to the end of the century. The model's response requires the combination of solar and anthropogenic forcing to approximate the early twentieth-century warming, while the radiative forcing from increasing greenhouse gases is dominant for the response in the late twentieth century, confirming previous studies. Of particular interest here is the model's amplification of solar forcing when this acts in combination with anthropogenic forcing. This difference is traced to the fact solar forcing is more spatially heterogeneous (i.e., acting most strongly in areas where sunlight reaches the surface) while greenhouse gas forcing is more spatially uniform. Consequently, solar forcing is subject to coupled regional feedbacks involving the combination of temperature gradients, circulation regimes, and clouds. The magnitude of these feedbacks depends on the climate's base state. Over relatively cloud-free oceanic regions in the subtropics, the enhanced solar forcing produces greater evaporation. More moisture then converges into the precipitation convergence zones, intensifying the regional monsoon and Hadley and Walker circulations, causing cloud reductions over the subtropical ocean regions, and, hence, more solar input. An additional response to solar forcing in northern summer is an enhancement of the meridional temperature gradients due to greater solar forcing over land regions that contribute to stronger West African and South Asian monsoons. Since the greenhouse gases are more spatially uniform, such regional circulation feedbacks are not as strong. These regional responses are most evident when the solar forcing occurs in concert with increased greenhouse gas forcing. The net effect of enhanced solar forcing in the early twentieth century is to produce larger solar-induced increases of tropical precipitation when calculated as a residual than for early century solar-only forcing, even though the size of the imposed solar forcing is the same. As a consequence, overall precipitation increases in the early twentieth century in the Asian monsoon regions are greater than late century increases, qualitatively consistent with observed trends in all-India rainfall. Similar effects occur in West Africa, the tropical Pacific, and the Southern Ocean tropical convergence zones."
"57195549023;55918418100;","The fully developed superrotation simulated by a general circulation model of a Venus-like atmosphere",2003,"10.1175/1520-0469(2003)060<0561:tfdssb>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042388198&doi=10.1175%2f1520-0469%282003%29060%3c0561%3atfdssb%3e2.0.co%3b2&partnerID=40&md5=28c81a4e7cc15ff4123956978b12dbfd","Formation and maintenance of the fully developed superrotation in the Venus atmosphere are investigated by using a Center for Climate System Research/National Institute for Environmental Study (CCSR/NIES) Venuslike atmospheric general circulation model. Under the condition that zonally uniform solar heating is used, the meridional circulation is dominated by a single cell in a whole atmosphere, and the superrotation with velocities faster than 100 m s-1 is formed near 60-km altitude. The meridional circulation effectively pumps up angular momentum from the lower to the middle atmosphere. Then the angular momentum is transported by poleward flows of the meridional circulation, and a part of the transported momentum is returned back to the low-latitudinal regions by waves. As a result, the simulated superrotation is formed by the Gierasch mechanism. Equatorward angular momentum flux required in the Gierasch mechanism is caused by not only barotropic waves but also various waves. Rossby, mixed Rossby-gravity, and gravity waves transport the angular momentum equatorward. Although vertically propagating gravity waves decelerate the superrotation above 70 km, the fully developed superrotation can be maintained in the cloud layer (45-70 km)."
"7003314664;6602228015;7102696626;6507112497;9636904200;","Scale interactions on diurnal to seasonal timescales and their relevance to model systematic errors",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141693062&partnerID=40&md5=b8fae98a555ee8b993aa244700380793","Examples of current research into systematic errors in climate models are used to demonstrate the importance of scale interactions on diurnal, intraseasonal and seasonal timescales for the mean and variability of the tropical climate system. It has enabled some conclusions to be drawn about possible processes that may need to be represented, and some recommendations to be made regarding model improvements. It has been shown that the Maritime Continent heat source is a major driver of the global circulation but yet is poorly represented in GCMs. A new climatology of the diurnal cycle has been used to provide compelling evidence of important land-sea breeze and gravity wave effects, which may play a crucial role in the heat and moisture budget of this key region for the tropical and global circulation. The role of the diurnal cycle has also been emphasized for intraseasonal variability associated with the Madden Julian Oscillation (MJO). It is suggested that the diurnal cycle in Sea Surface Temperature (SST) during the suppressed phase of the MJO leads to a triggering of cumulus congestus clouds, which serve to moisten the free troposphere and hence precondition the atmosphere for the next active phase. It has been further shown that coupling between the ocean and atmosphere on intraseasonal timescales leads to a more realistic simulation of the MJO. These results stress the need for models to be able to simulate firstly, the observed tri-modal distribution of convection, and secondly, the coupling between the ocean and atmosphere on diurnal to intraseasonal timescales. It is argued, however, that the current representation of the ocean mixed layer in coupled models is not adequate to represent the complex structure of the observed mixed layer, in particular the formation of salinity barrier layers which can potentially provide much stronger local coupling between the atmosphere and ocean on diurnal to intraseasonal timescales."
"7003311618;6701562494;6602513845;35412628400;","Evaluation of upper tropospheric water vapor in the NCAR Community Climate Model (CCM3) using modeled and observed HIRS radiances",2003,"10.1029/2002jd002539","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18744417455&doi=10.1029%2f2002jd002539&partnerID=40&md5=b8b1ebecd2403a786526c75296a28cdd","Upper tropospheric water vapor (UTWV) simulated by the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3) is evaluated by comparing modeled, clear-sky, brightness temperatures (BTs) to those observed from space by the High-Resolution Infrared Radiation Sounder (HIRS). The climate model was modified to utilize a highly accurate longwave radiation model (RRTM) and a separate radiance module, which contains physics consistent with RRTM, to calculate BTs in the National Oceanic and Atmospheric Administration (NOAA-7) HIRS 6.7 μm water vapor channel (CH12) and the 14.2 μm temperature channel (CH04). The CCM3 simulations follow the Atmospheric Model Intercomparison Project (AMIP) protocol for the period 1982-1984 to provide a basis for evaluating the water vapor distribution over a wide range of atmospheric conditions. BT differences of 2 K or less in CH04 indicate that CH12 differences are primarily due to water vapor rather than cloud effects or temperature variations. Regionally, CCM3 exhibits considerable positive and negative differences of 5-10 K in CH12 that are apparent in both convective and dry subtropical areas. This suggests that significant moist and dry discrepancies in UTWV amount of 50% or more are present in CCM3. These biases are also shown to persist through several annual cycles and at shorter timescales, and they are only slightly influenced by the improved longwave radiation model, which suggests a dynamical cause. Comparison to HIRS radiances provides a considerably more effective and comprehensive means of globally evaluating general circulation model (GCM)-simulated UTWV on various timescales than surface-based water vapor measurements."
"55506783800;35395776600;7102717744;7401844779;","Direct aerosol radiative forcing in the Yangtze delta region of China: Observation and model estimation",2003,"10.1029/2002jd002550","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347269103&doi=10.1029%2f2002jd002550&partnerID=40&md5=5d2b73958a0dc47be49c092a7c846a26","The Yangtze delta region of China is a key agricultural area that experiences relatively high aerosol loadings [Xu et al., 2002]. In order to characterize the aerosol radiative properties and estimate direct aerosol radiative forcing in this region, measurements of the multiwavelength aerosol optical depth, τλ, light scattering coefficient, σsp, and absorption coefficient, σap, as well as the downward photosynthetically active radiation (400-700 nm), DPAR, were conducted during November 1999 in Linan, China. The direct aerosol radiative forcing for photosynthetically active radiation (PAR) and total solar radiation (0.2-4.0 μm, TSR) at both the surface and top of atmosphere (TOA) are estimated based on the measurements using two radiative transfer models. The model estimates indicate that the mean cloud-free instantaneous direct aerosol radiative forcing efficiency (for solar zenith angle &lt; 70°) at the surface for PAR is - 73.5 W m-2, which is in agreement with the value of 74.4 W m-2 derived directly from the measurements of DPAR and 500 nm aerosol optical depth (τ500). On the basis of the measured mean τ500 of 0.61, and the estimated cloud optical depth and cloud coverage of 5.0 and 50%, respectively, the 24-hr mean direct aerosol radiative forcing at the surface for PAR is estimated to be approximately -11.2 W m-2 . This suggests that the amount of PAR reaching the surface over the Yangtze delta region is reduced by ∼16% as a result of the direct radiative effect of aerosols. The model results also indicate that the cloud-free 24-hr average direct aerosol radiative forcing efficiency at the TOA for TSR is -30.4 W m-2. When the presence of clouds is considered, the mean direct aerosol radiative forcing at the TOA for TSR is estimated to be approximately -12.1 W m-2 . This value is roughly an order of magnitude greater than the estimated global mean aerosol radiative forcing of -0.3 to -1.0 W m-2 suggested by the Intergovernmental Panel on Climate Change [1996]. Overall, this study indicates that aerosols have a substantial impact on the amount of radiation reaching the surface as well as the radiation balance at the TOA in the Yangtze delta region."
"7409080503;7402280263;7403588034;6602192723;7005780974;57211236643;7005182947;55359577800;","Evaluation of algorithms for fire detection and mapping across North America from satellite",2003,"10.1029/2001jd001377","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347269106&doi=10.1029%2f2001jd001377&partnerID=40&md5=a1659d28df9c6a3fa32bbbdd98ac24b6","This paper presents an evaluation of advanced very high resolution radiometer (AVHRR)-based remote sensing algorithms for detecting active vegetation fires [Li et al., 2000a] and mapping burned areas [Fraser et al., 2000] throughout North America. The procedures were originally designed for application in Canada with AVHRR data aboard the NOAA 14 satellite. They were tested here with both NOAA 11 and NOAA 14 covering the period 1989-2000. It was found that the active fire detection algorithm performs well with low commission and omission error rates over forested regions in the absence of cloud cover. Moderate errors were found over semi-arid areas covered by thin clouds, as well as along rivers and around lakes observed from sun-glint angles. A modification to a fire algorithm threshold and the addition of a new test can significantly improve the detection accuracy. Burned areas mapped by satellite were compared against extensive fire polygon data acquired by U.S. forest agencies in five western states. The satellite-based mapping matches nearly 90% of total forested burned area, with the difference being mainly attributable to omission of some nonburned islands and patches within the fire polygons. In addition, it maps a significant area of burning outside the fire polygons that appear to be true fires. The 10% omission error was found to be caused mainly by three factors: lack or insufficient number of active fires, partial burning, and vegetation recovery after early season burning. In addition to total area, the location and shapes of burned scars are consistent with the ground-based maps. Overall, the two algorithms are competent for detecting and mapping forest fires in North America north of Mexico with minor modifications."
"7201646465;","Efficiency of storm tracks an important climate parameter? The role of cloud radiative forcing in poleward heat transport",2003,"10.1029/2002jd002756","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347899408&doi=10.1029%2f2002jd002756&partnerID=40&md5=e991a9ce40c4d7cdfcf6f6ca939fe65b","Variability in poleward atmosphere-ocean heat transport has been suggested as one driver of climate change on long timescales. The radiative impact of clouds, particularly extratropical clouds, is an important factor in determining the equilibrium value of this heat transport in the current climate. Therefore, significant changes in cloudiness and cloud radiative forcing could potentially force equally significant adjustments in total poleward heat transport, and thus in atmospheric and/or oceanic dynamics. At the same time, these extratropical clouds and their strong radiative impact are largely the result of the atmospheric eddies that make up the storm tracks. Coincidentally, these storm track eddies also accomplish most of the extratropical poleward heat transport. At high latitudes, the annual-mean radiative cooling of these clouds is shown here to be of the same order as the atmospheric eddy heat transport convergence, and of opposite sign. Some potential implications of these points for climate change studies are discussed."
"7405459515;7006783796;7004325649;7403531523;7005070958;55745955800;6701464149;24611027600;","Characteristics of the 1997/1998 El Niño cloud distributions from SAGE II observations",2003,"10.1029/2002jd002501","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346639249&doi=10.1029%2f2002jd002501&partnerID=40&md5=269a074489e1304a37a02ad51e090b8b","The present study examines the characteristics of cloud distributions with emphasis on cloud longwave radiative forcing (CLRF) during the peak of the 1997/1998 El Niño in relation to climatological conditions, based on measurements from the Stratospheric Aerosol and Gas Experiment (SAGE) II. The observed distinct cloud occurrence and CLRF during this unusual 1997/1998 El Niño constitutes a unique data set for validating and improving cloud-radiation-climate interactions in general circulation and climate models. Using the solar occultation technique, the SAGE II satellite instrument is capable of providing measurements with a 1-km vertical resolution facilitating the analysis with sufficient vertical as well as near global scale (70°S-70°N) details. The present study indicates (1) above normal high-altitude opaque cloud occurrence over the eastern tropical Pacific and an opposite situation over the Pacific warm pool, leading to a distribution of the cumulative opaque cloud anomalies above 3 km generally consistent with the pattern of observed tropical sea surface temperature and precipitation anomalies; (2) a similar behavior in the subvisual cloud distributions near the tropical tropopause; (3) a zonally averaged cloud distribution that is characterized by reduced opaque clouds at low latitudes, except in the southern tropics below 10 km, and by enhanced opaque clouds at high latitudes, along with increased subvisual clouds in the southern tropics and decreased subvisual clouds in the northern subtropics in the upper troposphere; and (4) a geographic distribution of model-calculated CLRF anomalies that resembles closely that inferred from the Earth Radiation Budget Experiment and the Clouds and the Earth's Radiant Energy System. A discussion on the influence of the El Niño on large-scale mean tropospheric circulations is also provided."
"55745955800;8859530100;7004479957;7005814217;7006705919;","A modified formulation of fractional stratiform condensation rate in the NCAR Community Atmospheric Model (CAM2)",2003,"10.1029/2002jd002523","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346639253&doi=10.1029%2f2002jd002523&partnerID=40&md5=fb07e880041a3b485c68f83fd8572269","This paper describes a modified formulation of stratiform condensation rate associated with fractional cloudiness in the Community Atmospheric Model Version 2 (CAM2). It introduces an equation to link cloudiness change with the variation of total condensate. Together with a diagnostic cloud relationship that represents subgrid-scale variability of relative humidity, a closed system is formed to calculate the fractional condensation rate. As a result, the new formulation eliminates the two closure assumptions in the Rasch and Kristjànsson [1998] prognostic cloud scheme. It also extends the Sundqvist [1978] scheme by including the influence of convective detrainment and advection of condensates on the fractional cloudiness. Comparison is made between the present formulation and the Rasch and Kristjànsson scheme by using data from the Atmospheric Radiation Measurement Program and through global model simulations with CAM2. It is shown that relative to the Rasch and Kristjànsson scheme, the new formulation produces less clouds and a slightly warmer troposphere, thus reducing the original cold bias in the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM). Even though the overall impact of the new formulation on the model climate is small, the modifications lead to more consistent treatments of fractional cloudiness change, condensation rate, and cloud water change in the model."
"7203001286;7006084942;27267529400;6603613067;57203053317;6603452105;6701553081;16173929000;7003908632;55807293800;7801611677;7003371432;7007067997;16444196600;","Canadian Aerosol Module: A size-segregated simulation of atmospheric aerosol processes for climate and air quality models 1. Module development",2003,"10.1029/2001jd002002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347269076&doi=10.1029%2f2001jd002002&partnerID=40&md5=4d6ca4ea531045897e125adb7bee107e","A size-segregated multicomponent aerosol algorithm, the Canadian Aerosol Module (CAM), was developed for use with climate and air quality models. It includes major aerosol processes in the atmosphere: generation, hygroscopic growth, coagulation, nucleation, condensation, dry deposition/sedimentation, below-cloud scavenging, aerosol activation, a cloud module with explicit microphysical processes to treat aerosol-cloud interactions and chemical transformation of sulphur species in clear air and in clouds. The numerical solution was optimized to efficiently solve the complicated size-segregated multicomponent aerosol system and make it feasible to be included in global and regional models. An internal mixture is assumed for all types of aerosols except for soil dust and black carbon which are assumed to be externally mixed close to sources. To test the algorithm, emissions to the atmosphere of anthropogenic and natural aerosols are simulated for two aerosol types: sea salt and sulphate. A comparison was made of two numerical solutions of the aerosol algorithm: process splitting and ordinary differential equation (ODE) solver. It was found that the process-splitting method used for this model is within 15% of the more accurate ODE solution for the total sulphate mass concentration and <1% accurate for sea-salt concentration. Furthermore, it is computationally more than 100 times faster. The sensitivity of the simulated size distributions to the number of size bins was also investigated. The diffusional behavior of each individual process was quantitatively characterized by the difference in the mode radius and standard deviation of a lognormal curve fit of distributions between the approximate solution and the 96-bin reference solution. Both the number and mass size distributions were adequately predicted by a sectional model of 12 bins in many situations in the atmosphere where the sink for condensable matter on existing aerosol surface area is high enough that nucleation of new particles is negligible. Total mass concentration was adequately simulated using lower size resolution of 8 bins. However, to properly resolve nucleation mode size distributions and minimize the numerical diffusion, a sectional model of 18 size bins or greater is needed. The number of size bins is more important in resolving the nucleation mode peaks than in reducing the diffusional behavior of aerosol processes. Application of CAM in a study of the global cycling of sea-salt mass accompanies this paper [Gong et al, 2002]."
"7401984344;","Cloudiness over the contiguous United States: Contemporary changes observed using ground-based and ISCCP D2 data",2003,"10.1029/2002GL015887","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037591051&doi=10.1029%2f2002GL015887&partnerID=40&md5=0cc6f28c3cf0a9497016bd55579d6ffd","Comparisons of monthly daytime cloudiness time series of total cloud cover (TCL) and cloud types' occurrences between the ground-based and International Satellite Cloud Climatology Project (ISCCP) D2 datasets were conducted over the contiguous United States. Despite its large bias (+6.7% to +20.8%), TCL in ISCCP D2 is highly correlated with the surface observations in all seasons. Close correspondence of seasonal and interannual variability between these two datasets is also seen in low stratiform and cirrus clouds. Reconstruction of these cloud characteristics using ISCCP data was performed for the 1990s when the Automated Surface Observation System (ASOS) implementation irreversibly broke the homogeneity of ground-based cloudiness time series over the United States. Verification of reconstructed cloudiness characteristics was conducted using the independent insitu climatic variables such as diurnal temperature range and precipitation."
"7404142321;7003976079;7004764167;","Evaluating the cloud response to climate change and current climate variability",2003,"10.1007/s00382-002-0303-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038266961&doi=10.1007%2fs00382-002-0303-3&partnerID=40&md5=72a264c344c68ad5e5136718cfc69745","The radiative feedback from clouds remains one of the largest uncertainties in determining the climate sensitivity to increasing greenhouse gas (GHG) concentrations. This study presents a diagnostic method of evaluating the simulated tropical cloud response to climate change. The method is illustrated by comparing the effect on the climate response of several new developments to the Meteorological Office's Hadley Centre atmosphere model coupled to a mixed-layer ocean. It is shown that the cloud response over tropical oceans to a doubling of CO2 at individual locations appears to depend more upon the change in vertical velocity and whether the sea surface warms more or less than the tropical mean, rather than the absolute value of the surface temperature. By using compositing techniques, the model cloud response to doubling CO2 is related to the model cloud response to present-day spatio-temporal sea surface temperature anomalies. The use of special model diagnostics to take account of cloud overlap assumptions allows comparison of the modelled present-day variability with satellite data to evaluate the cloud response. Based upon this evaluation, it is possible to identify which of the new physical schemes are likely to provide a more reliable cloud response in the climate change simulation. It is found that overall, the model developments improve the simulation of present-day cloud processes and, through the relation with the climate change simulation, we may have more confidence in the cloud response to increasing GHGs occurring via these processes."
"57212781009;","A comparison of climate feedbacks in general circulation models",2003,"10.1007/s00382-003-0310-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038170025&doi=10.1007%2fs00382-003-0310-z&partnerID=40&md5=2565fdb9efcd7a994721c5a932479a33","A comparison is performed for water vapour, cloud, albedo and lapse rate feedbacks taken from published results of 'offline' feedback calculations for general circulation models (GCMs) with mixed layer oceans performing 2 × CO2 and solar perturbation experiments. All feedbacks show substantial inter-model spread. The impact of uncertainties in feedbacks on climate sensitivity is discussed. A negative correlation is found between water vapour and lapse rate feedbacks, and also between longwave and shortwave components of the cloud feedback. The mean values of the feedbacks are compared with results derived from model intercomparisons which evaluated cloud forcing derived feedbacks under idealized climate forcing. Results are found to be comparable between the two approaches, after allowing for differences in experimental technique and diagnostic method. Recommendations are made for the future reporting of climate feedbacks."
"7005070958;6507163086;","Climate change during 1985-1999: Cloud interactions determined from satellite measurements",2003,"10.1029/2002gl016128","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038168999&doi=10.1029%2f2002gl016128&partnerID=40&md5=784a1dc9a24850e2e3616d8590e40121","We have extended two recent studies that present evidence for significant decadal variability in the top-of-atmosphere (TOA) tropical radiative energy budget by combining satellite measurements of the TOA energy budget and cloud cover with measurements of the Earth's surface temperature. The domain studied is from 40°S to 40°N. As in the prior studies, which were restricted to lower latitudes, there is a significant increase in the TOA outgoing longwave radiation during the period 1985 to 1999 together with an increase in solar (shortwave) radiation absorbed by the climate system. It is suggested that these changes are related to an observed reduction in cloud cover."
"7403508241;7006783796;7005673120;","Cloud liquid water path variations with temperature observed during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment",2003,"10.1029/2002jd002851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742305189&doi=10.1029%2f2002jd002851&partnerID=40&md5=596ff54e8ce53344c4d3eac078cebe61","Because clouds play such a significant role in climate, understanding their responses to climatic temperature changes is essential to determining the overall impact of a given climate forcing. Cloud liquid water path (LWP) over tropical and midlatitude oceans has been observed to decrease with increasing cloud temperature. The presence of an ice sheet over the Arctic Ocean alters the energy and moisture exchange between the ocean and the atmospheric boundary layer and thus may affect the relationship between LWP and temperature. The variations of LWP with cloud and surface temperatures are examined in this paper using a combination of surface and satellite data taken during the 1998 Surface Heat Budget of the Arctic Ocean and the FIRE Arctic Clouds Experiments. The results show that LWP increases with temperature primarily because of an increase in cloud thickness that is enabled by the rise in surface moisture during the melt season. Cloud base heights and lifting condensation levels decrease as a result of the greater surface relative humidity and temperature. The average change rate of LWP with cloud temperature is 3.3% K-1, a value slightly smaller than earlier observations taken over cold midlatitude land areas. This cloud LWP feedback with temperature differs significantly from that estimated over other marine environments and should be taken into account in all climate models with explicit cloud feedbacks."
"57212781009;","Seasonal contributions to climate feedbacks",2003,"10.1007/s00382-002-0301-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037929583&doi=10.1007%2fs00382-002-0301-5&partnerID=40&md5=6d965fb918e35bbb5a6385b37001a330","This study addresses the question: How do the contributions to feedbacks in a climate model vary over the seasonal cycle? To answer this the feedbacks are evaluated from an equilibrium doubled CO2 experiment performed using the Bureau of Meteorology Research Centre (BMRC) General Circulation Model. Monthly means of the top-of-atmosphere radiative perturbations (which together comprise the annual climate feedbacks) are extracted to produce a mean annual cycle. It is found that the radiative contributions to the total longwave (LW) feedback are fairly constant throughout the year. Those to the total shortwave (SW) feedback, on the other hand, vary by a factor of three, from a maximum in July to a minimum in November. Of the LW feedbacks, contributions to the lapse rate shows greatest seasonal variation, while those to water vapour and cloud feedbacks vary by relatively small amounts throughout the year. Contributions to the lapse rate feedback as a function of surface type and latitude reveal conflicting positive and negative radiative perturbations, which vary most strongly at high latitudes. Of the SW feedbacks, contributions to both albedo and cloud show large seasonal variations. Radiative perturbations contributing to albedo feedback vary in strength with snow and sea-ice retreat which occurs at different latitudes and in different months. They are shown to be highly sensitive to the amount of incident solar radiation in a given month. SW radiative perturbations due to cloud changes vary in sign between opposite seasons. Contributions to the seasonal variations of the cloud component feedbacks, which make up the total cloud feedback, are also examined. In the LW, the feedback is dominated by the total cloud water term. Radiative perturbations due to this component show relatively little variation throughout the year. In the SW, the main source of seasonal variation occurs for contributions to the cloud amount feedback: Radiative perturbations vary from strongly positive in July to close to zero in December. The seasonal cycle of the perturbations making up the other cloud component feedbacks is also considered. Implications for climate sensitivity, and for the diagnosis of climate feedbacks are discussed."
"24827532700;6603745487;","Visual meteorological observations as indicators of climate changes, derived from long-term time series of the Potsdam station",2003,"10.1127/0941-2948/2003/0012-0047","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645448921&doi=10.1127%2f0941-2948%2f2003%2f0012-0047&partnerID=40&md5=c9725bb7aea9d82f2f07daac1f257cc0","On the basis of the visual meteorological observations at the Potsdam station for the ""type of precipitation"" (period 1893-2000) and the ""cloud coverage"" (1894-2000) it is shown that such subjectively registered values have a strong connection with measured parameters. Moreover they reflect climate changes very well. A main result is the fact that in summer a clear decrease in advective precipitation can be observed combined with an increase in convective precipitation. This development is accompanied by a change in the daily course of the cloud cover. © Gebrüder Borntraeger, Berlin, Stuttgart 2003."
"55505400300;7403393470;7406074682;57198575228;","Information about low cloud amount recorded in δ13 C series of tree ring cellulose of Pinus Koraiensis in Antu area, Jilin",2003,"10.1007/bf02831543","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038209040&doi=10.1007%2fbf02831543&partnerID=40&md5=22849fd640568eb316f2b0959a0d19a5","Relationship between the δ 13 C of tree ring cellulose from Pinus Koraiensis and climate parameters was investigated. A significantly negative correlation between δ 13 C and mean low-cloud amount from May to July was discovered, which contributes to reconstructing the mean low-cloud amount from May to July at Antu in recent 200 years. Periodicals of quasi-8-year, quasi-4-year and quasi-2-year were detected both in δ 13 C series and in the reconstructed low cloud amount series with 95% confidence level. Quasi-8-year period may reflect the integrated influence of solar activity, monsoon activity and local regional factors. Quasi-4-year and quasi-2-years periods indicate the influences of ENSO and Quasi Biennial Oscillation (QBO) of East Asian monsoon, respectively."
"7201866492;","Ice age mystery: A proposed theory for the cause of long term climate change",2003,"10.1007/s00704-002-0710-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038067845&doi=10.1007%2fs00704-002-0710-8&partnerID=40&md5=106851907fdae72e7d8d00b1883ed19d","Analysis of available data shows that the duration of the glacial/interglacial cycle is determined by the time for the ocean to go through one major temperature cycle. At the start of an interglacial period, clear skies with consequent release of CO2 from the ocean, warms the atmosphere, which in turn eventually warms the ocean to its maximum. Cloudy skies then cause the climate (land and air temperature) to cool and the CO2 to be reabsorbed to start glaciation preliminaries. The albedo feedback effect of the glacial ice, a relatively warm ocean, which produces enhanced cloud cover, and the increased solubility of CO2 in cold seawater ensure a long period of glaciation. Glacial periods end when pack ice spreads out on the ocean cooling it until reduced cloud cover once again allows the Sun's heat, unreflected by cloud cover, to melt the ice and release CO2 back into the atmosphere."
"11241983900;6603939930;7004122764;","3d cloud products for weather prediction and climate modelling [Produits 3D des nuages pour les modèles numériques de prévisions et les modéles climatologi-ques] [3D Wolkenprodukte für Wettervorhersage-und Klimamodelle]",2003,"10.5194/gh-58-90-2003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751431234&doi=10.5194%2fgh-58-90-2003&partnerID=40&md5=0c7ed2a37c42186fa70e59a431824f6e","3D Cloud Products for Weather Prediction and Climate Modelling In this paper, the possibilities of satellite-based and ground-based stereoscopy of clouds are examined, with the objective to derive cloud top and cloud base heights and motion. These parameters are very important for a better description of clouds for nowcasting and numerical weather prediction models. For the satellite part, images of ATSR2 (on ERS-2) and MISR (on EOS Terra) are used. As Stereo image pairs from polar-orbiting satellites are never perfectly synchro-nous (time delay of some seconds between the image reception from the different viewing angles), the height error of the cloud top heights, introduced by the along-track motion component, is corrected with the cloud top winds extracted from Meteosat-6 and -7. For MISR, with nine viewing angles, this height cor-rection is not needed when at least three images from non-symmetric Cameras are used; then, it is possible to directly separate the along-track parallax (due to cloud height) from the along-track wind contribution (due to cloud motion). Our new ground-based imager System was operated in coincidence with an overpass of ERS-2 in October 1999. The ground measurements proved to be an interesting technique to validate satellite-based cloud top height and motion of vertically thin clouds and to additionally detect more detailed cloud features, which is particularly important for accu-rate nowcasting in mountainous terrain. © Author(s) 2003. This work is distributed."
"36069892200;6701590980;","Identifying drizzle within marine stratus with W-band radar reflectivity",2003,"10.1016/j.atmosres.2003.08.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0345550399&doi=10.1016%2fj.atmosres.2003.08.001&partnerID=40&md5=83cc69fc9a985da682a1de0fb10b15de","Airborne cloud radar and cloud microphysical data, collected in summertime stratus clouds off the Oregon coast, are analyzed to obtain an empirical threshold radar reflectivity above which drizzle can be expected in warm marine stratus. Such clouds, which are prevalent over the eastern subtropical oceans, have a profound impact on global climate. This study finds that the threshold reflectivity for drizzle is a strong function of height within the cloud layer. Both radar reflectivities and calculated reflectivities (based on measured droplet spectra) indicate that the threshold is most crisply defined in the lower half of the stratus cloud deck. The use of the threshold reflectivity profile to flag drizzle is illustrated by examining the dependency of radar reflectivity on cloud water content. Such dependency is non-existent in marine stratus in general, but a clear relationship emerges when drizzle cases are excluded. © 2003 Elsevier B.V. All rights reserved."
"57205867148;25941200000;24322005900;","A fast, flexible, approximate technique for computing radiative transfer in inhomogeneous cloud fields",2003,"10.1029/2002jd003322","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742270233&doi=10.1029%2f2002jd003322&partnerID=40&md5=1f9b4805d590910ad90c9c4691cbe2ec","Radiative transfer schemes in large-scale models tightly couple assumptions about cloud structure to methods for solving the radiative transfer equation, which makes these schemes inflexible, difficult to extend, and potentially susceptible to biases. A new technique, based on simultaneously sampling cloud state and spectral interval, provides radiative fluxes that are guaranteed to be unbiased with respect to the benchmark Independent Column Approximation and works equally well no matter how cloud structure is specified. Fluxes computed in this way are subject to random, uncorrelated errors that depend on the distribution of cloud optical properties. Seasonal forecasts, however, are not sensitive to this noise, making the method useful in weather and climate prediction models."
"36868302600;","Solar activity and terrestrial climate: An analysis of some purported correlations",2003,"10.1016/S1364-6826(03)00041-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037971543&doi=10.1016%2fS1364-6826%2803%2900041-5&partnerID=40&md5=873e46816c08fce78c49b6d45fad6aea","The last decade has seen a revival of various hypotheses claiming a strong correlation between solar activity and a number of terrestrial climate parameters: Links between cosmic rays and cloud cover, first total cloud cover and then only low clouds, and between solar cycle lengths and Northern Hemisphere land temperatures. These hypotheses play an important role in the scientific as well as in the public debate about the possibility or reality of a man-made global climate change. I have analyzed a number of published graphs which have played a major role in these debates and which have been claimed to support solar hypotheses. My analyses show that the apparent strong correlations displayed on these graphs have been obtained by an incorrect handling of the physical data. Since the graphs are still widely referred to in the literature and their misleading character has not yet been generally recognized, I have found it appropriate to deliver the present overview. Especially, I want to caution against drawing any conclusions based upon these graphs concerning the possible wisdom or futility of reducing the emissions of man-made greenhouse gases. My findings do not by any means rule out the existence of important links between solar activity and terrestrial climate. Such links have over the years been demonstrated by many authors. The sole objective of the present analysis is to draw attention to the fact that some of the widely publicized, apparent correlations do not properly reflect the underlying physical data. © 2003 Elsevier Science Ltd. All rights reserved."
"35572096100;7007108728;6603734019;7003535385;7102331727;","Microphysical characterization of mixed-phase clouds",2003,"10.1256/qj.01.204","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037284055&doi=10.1256%2fqj.01.204&partnerID=40&md5=37490716698cda85e43c188e59589b9f","A detailed study of mixed-phase clouds associated with frontal systems obtained from a large dataset collected by the Convair 580 aircraft of the National Research Council (NRC) of Canada is presented. The total length of analysed in-cloud legs having total-water content (TWC) &gt; 0.01g m-3 was about 44 × 103 km. The ice-water fraction (μ3 = ice-water content/TWC) had a minimum in the range 0.1 &lt; μ3 &lt; 0.9, and two maxima for liquid clouds (μ3 &lt; 0.1) and ice clouds (μ3 &gt; 0.9). The concentration of particles in glaciated clouds was found to be nearly constant at 2-5 cm-3 for temperatures -35 °C &lt; T &lt; 0°C. The concentration of droplets in liquid clouds decreased with decreasing temperature. The mean volume diameter of particles in ice clouds varied between 20 μm and 35 μm, and in liquid clouds between 10 μm and 12 μm. Both ice- and liquid-water content decreased with decreasing temperature. The results of this study may be used for validation of remote-sensing retrievals, and for weather- and climate-models."
"7102948268;7003633107;","Cosmic ray flux impact on clouds? An analysis or radiosonde, cloud cover, and surface temperature records from the United States",2003,"10.1007/s00704-003-0732-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0142199445&doi=10.1007%2fs00704-003-0732-x&partnerID=40&md5=32ffef62e9df1f0f26f79d1696f8c3ff","Many scientists have suggested that variations in cosmic ray flux may impact cloudiness at regional, hemispheric, or global scales. However, considerable debate surrounds (a) whether high or low clouds are most strongly impacted by cosmic rays, (b) the degree of seasonality in cloud responses to cosmic rays, and (c) the determination of physical processes involved in cosmic ray/cloud interactions. Some scientists find strong correlation coefficients between cloud measurements and cosmic ray flux, while others find no relationship whatsoever; virtually all scientists working on this issue are hampered by the relatively short time period with accurate cloud and cosmic ray flux records. In an attempt to extend the period of record, we assembled surface and radiosonde data for the United States over the period 1957-1996 along with sunspot records which are known to be strongly, but inversely, related to cosmic ray flux. We also assembled cloud cover data and cosmic ray measurements over a reduced time period. We found that periods with low sunspot number (times with high cosmic ray flux) are associated with significantly higher dew point depressions, a higher diurnal temperature range, and less cloud cover. Our results do not support suggestions of increased cloud cover during periods of high cosmic ray flux."
"6603196991;6603868770;","Accuracy of cloud liquid water path from ground-based microwave radiometry. 1. Dependency on cloud model statistics",2003,"10.1029/2002rs002654","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0041883488&doi=10.1029%2f2002rs002654&partnerID=40&md5=80ca2e2cd7d336e2c81bc7e31cdcb15f","This paper investigates the influence of cloud model statistics on the accuracy of statistical multiple-frequency liquid water path (LWP) retrievals for a ground-based microwave radiometer. Statistical algorithms were developed from a radiosonde data set in which clouds were modeled by using a relative humidity threshold and a modified adiabatic assumption. Evaluation of the algorithms was then performed by applying the algorithms to four data sets in which clouds were generated in different ways (i.e., threshold method, gradient method, and cloud microphysical model). While classical two-channel algorithms, in this case using frequencies at 22.985 and 28.235 GHz, do not show a significant dependency on the cloud model, the inclusion of an additional 50-GHz channel can introduce significant systematic errors. The addition of a 90-GHz frequency to the two-channel algorithm leads to a larger increase in LWP accuracy than in case of the 50-GHz channel and is less sensitive to the choice of cloud model. A drizzle case from the cloud microphysical model shows no significant loss of accuracy for the microwave radiometer algorithms, in contrast to simple cloud radar retrievals of liquid water. In case of rain, however, the results deteriorate when the total liquid water path is larger than 700 g m-2."
"7006393918;7005981420;8304837900;","Combined infrared stereo and laser ranging cloud measurements from shuttle mission STS-85",2003,"10.1175/1520-0426(2003)020<0067:CISALR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141789769&doi=10.1175%2f1520-0426%282003%29020%3c0067%3aCISALR%3e2.0.CO%3b2&partnerID=40&md5=5066dcc7b161d240d65a97d8dd69fc2b","Multiangle remote sensing provides a wealth of information for earth and climate monitoring, such as the ability to measure the height of cloud tops through stereoscopic imaging. Further, as technology advances so do the options for developing spacecraft instrumentation versatile enough to meet the demands associated with multiangle measurements. One such instrument is the infrared spectral imaging radiometer, which flew as part of mission STS-85 of the space shuttle Columbia in 1997 and was the first earth-observing radiometer to incorporate an uncooled microbolometer array detector as its image sensor. Specifically, a method for computing cloud-top height with a precision of ±620 m from the multispectral stereo measurements acquired during this flight has been developed, and the results are compared with coincident direct laser ranging measurements from the shuttle laser altimeter. Mission STS-85 was the first space flight to combine laser ranging and thermal IR camera systems for cloud remote sensing."
"7005890514;51360903200;","Climate sensitivity and response",2003,"10.1007/s00382-002-0283-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037302663&doi=10.1007%2fs00382-002-0283-3&partnerID=40&md5=6cd9bbd3c77babb229d377efdb1f4bd8","Results from climate change simulations indicate a reasonably robust proportionality between global mean radiative forcing and global mean surface air temperature response. The ""constant"" of proportionality is a measure of the overall strength of climate feedback processes and hence of global climate sensitivity. Geographically, however, temperature response patterns are generally not proportional to, nor do they resemble, their parent forcing patterns. Temperature response patterns, nevertheless, exhibit a remarkable additivity whereby the sum of response patterns for different forcings closely resembles the response pattern for the sum of the forcings. The geographical distribution of contributions to the climate sensitivity/feedback are obtained diagnostically from simulations with the Canadian Centre for Climate Modelling and Analysis (CCCma) coupled global climate model (GCM). There is positive feedback over high-latitude oceans, over northern land areas, and over the equatorial Pacific. The remaining regions over oceans and tropical land areas exhibit negative feedback. The feedback results are decomposed into components associated with short-and longwave radiative processes and in terms of cloud-free atmosphere/surface and cloud feedbacks. While the geographic pattern of the feedbacks may generally be linked to local processes, all feedback processes display regions of both positive and negative values (except for the solar atmosphere/surface feedback associated with the retreat of ice and snow which is positive) and all vary from place to place so that there is no simple physical picture that operates everywhere. The stable geographical pattern of the feedback is a consequence of the balance between local physical processes rather than the dominance of a particular process. The feedback results indicate that, to first order, temperature response patterns are determined by the geographical pattern of local feedback processes. The feedback processes act to localize forcing changes and to generate temperature response patterns which depend firstly on the pattern of feedbacks and only secondarily on the pattern of the forcing. The geographical distribution of feedback processes can be regarded as a feature of the climate model (and by inference of the climate system) and not (or only comparatively weak) functions of forcing and climate state. An illustrative model is able to reproduce qualitatively the kinds of forcing/temperature response behavior seen in the CCCma GCM including the quasi-independence of forcing and response patterns, the additivity of temperature response patterns, and the resulting ""nonconstancy"" of the global climate sensitivity."
"7103248807;57203049177;7004169476;7405666962;7407104838;25030776200;7406514318;57198966831;7103373205;7402383878;7006280684;6506416205;","Anthropogenic climate change for 1860 to 2100 simulated with the HadCM3 model under updated emissions scenarios",2003,"10.1007/s00382-002-0296-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038656472&doi=10.1007%2fs00382-002-0296-y&partnerID=40&md5=c60596d97bf9eeedb229452e8f3b8160","In this study we examine the anthropogenically forced climate response over the historical period, 1860 to present, and projected response to 2100, using updated emissions scenarios and an improved coupled model (HadCM3) that does not use flux adjustments. We concentrate on four new Special Report on Emission Scenarios (SRES) namely (AlFI, A2, B2, B1) prepared for the Intergovernmental Panel on Climate Change Third Assessment Report, considered more self-consistent in their socio-economic and emissions structure, and therefore more policy relevant, than older scenarios like IS92a. We include an interactive model representation of the anthropogenic sulfur cycle and both direct and indirect forcings from sulfate aerosols, but omit the second indirect forcing effect through cloud lifetimes. The modelled first indirect forcing effect through cloud droplet size is near the centre of the IPCC uncertainty range. We also model variations in tropospheric and stratospheric ozone. Greenhouse gas-forced climate change response in B2 resembles patterns in IS92a but is smaller. Sulfate aerosol and ozone forcing substantially modulates the response, cooling the land, particularly northern mid-latitudes, and altering the monsoon structure. By 2100, global mean warming in SRES scenarios ranges from 2.6 to 5.3 K above 1900 and precipitation rises by 1%/K through the twenty first century (1.4%/K omitting aerosol changes). Large-scale patterns of response broadly resemble those in an earlier model (HadCM2), but with important regional differences, particularly in the tropics. Some divergence in future response occurs across scenarios for the regions considered, but marked drying in the mid-USA and southern Europe and significantly wetter conditions for South Asia, in June-July-August, are robust and significant."
"7005270430;7003915935;56210486400;7102080550;57205299261;","Impact of cloud analysis on numerical weather prediction in the Galician region of Spain",2003,"10.1175/1520-0450(2003)042<0129:IOCAON>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141539307&doi=10.1175%2f1520-0450%282003%29042%3c0129%3aIOCAON%3e2.0.CO%3b2&partnerID=40&md5=a9c9a149c1ed4e96103f3baff7faf859","The Advanced Regional Prediction System (ARPS) is applied to operational numerical weather prediction in Galicia, northwest Spain. The model is run daily for 72-h forecasts at a 10-km horizontal spacing. Located on the northwest coast of Spain and influenced by the Atlantic weather systems, Galicia has a high percentage (nearly 50%) of rainy days per year. For these reasons, the precipitation processes and the initialization of moisture and cloud fields are very important. Even though the ARPS model has a sophisticated data analysis system (""ADAS"") that includes a 3D cloud analysis package, because of operational constraints, the current forecast starts from the 12-h forecast of the National Centers for Environmental Prediction Aviation Model (AVN). Still, procedures from the ADAS cloud analysis are being used to construct the cloud field, based on AVN data and then are applied to initialize the microphysical variables in ARPS. Comparisons of the ARPS predictions with local observations show that ARPS can predict very well both the daily total precipitation and its spatial distribution. ARPS also shows skill in predicting heavy rains and high winds, as observed during November 2000, and especially in the prediction of the 5 November 2000 storm that caused widespread wind and rain damage in Galicia. It is demonstrated that the cloud analysis contributes to the success of the precipitation forecasts."
"7406040464;","Uranium and thorium series radionuclides in rainwater over several tropical storms",2003,"10.1016/S0265-931X(02)00060-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037212397&doi=10.1016%2fS0265-931X%2802%2900060-7&partnerID=40&md5=e21ab1bf710085798ff70a0870cea7d1","The activity concentrations of uranium and thorium series radionuclides were measured in rainwater samples from 16 storms in northern Australia. For six of these storms, sequential intra-storm samples were collected. The results indicate that a substantial fraction of the measured activity concentrations of 238U, 234U, 230Th, 226Ra and, to a lesser extent, 210Po were due to below-cloud washout of dust transported from the nearby Ranger uranium mine. For the six intra-storm studies, the concentrations of these dust-related radionuclides decreased to one half or less of their initial value after the first one to two millimetres of rainfall, although in some cases they later increased when the rainfall intensity reduced. Most of the 210Pb activity appears to have been sourced from in-cloud rainout, although below-cloud washout was probably responsible for significant reductions in concentrations observed over the course of three of the six storms. 210Pb residence times based on the 210Pb-210Po couple varied significantly from storm to storm, but relatively little over the course of each of the six storms studied in detail. This implies that, apart from the initial reduction in below-cloud washout, there was no substantial change in the source air mass for the 210Pb during these storms. © 2002 Elsevier Science Ltd. All rights reserved."
"7003561442;12239699000;13406672500;","Large aerosol radiative forcing due to the 1997 Indonesian forest fire",2003,"10.1029/2002GL015979","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038168972&doi=10.1029%2f2002GL015979&partnerID=40&md5=54230eb246c2f39d4107caa42b0c409c","During the last decade, the feedback between El Niño and biomass burning caused the Indonesia's forest fire aerosols to be the second most significant source of anthropogenic aerosol over the tropical Indian Ocean after the South Asian Haze. In this paper, the estimates of the radiative forcing during the 1997 Indonesia's forest fire have been obtained by integrating satellite derived aerosol optical depths and cloud cover with in-situ observations of single scattering albedo and a Monte-Carlo Aerosol-Cloud radiation model. The haze reduced the seasonal average solar radiation absorbed by the equatorial Indian ocean by as much as 30 to 60 W m-2 during September to November 1997, and increased the atmospheric solar heating by as much as 50% to 100% within the first 3 kilometers. The radiative forcing at the top of the atmosphere (TOA) was in the range of 5 to 15 W m-2 under cloudy skies. The significance of such large radiative flux changes to the tropical ocean-atmosphere heat budget and climate needs to be examined with climate models."
"7004153293;56618721800;6507989667;7006442960;","Climate system modeling in the framework of the tolerable windows approach: The ICLIPS climate model",2003,"10.1023/A:1021300924356","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037285052&doi=10.1023%2fA%3a1021300924356&partnerID=40&md5=6af9802e74de6071a4e50d21d02d3f29","The computational burden associated with applications of the Tolerable Windows Approach (TWA) considerably exceeds that of traditional integrated assessments of global climate change. As part of the ICLIPS (Integrated Assessment of Climate Protection Strategies) project, a computationally efficient climate model has been developed that can be included in integrated assessment models of any kind. The ICLIPS climate model (ICM) is implemented in GAMS. It is driven by anthropogenic emissions of CO2, CH4, N2O, halocarbons, SF6, and SO2. The output includes transient patterns of near-surface air temperature, total column-integrated cloud cover fraction, precipitation, humidity, and global mean sea-level rise. The carbon cycle module explicitly treats the nonlinear sea water carbon chemistry and the nonlinear CO2 fertilized biosphere uptake. Patterns of the impact-relevant climate variables are derived form empirical orthogonal function (EOF) analysis and scaled by the principal component of temperature change. The evolution of the latter is derived from a box-model-type differential analogue to its impulse response function convolution integral. We present a description of the ICM components and some results to demonstrate the model's applicability in the TWA setting."
"6701378450;57196499374;","Parameterization of cloud droplet formation in global climate models",2003,"10.1029/2002jd002911","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742287914&doi=10.1029%2f2002jd002911&partnerID=40&md5=271d066b3d68ebe7c2cebd63a909f56d","An aerosol activation parameterization has been developed based on a generalized representation of aerosol size and composition within the framework of an ascending adiabatic parcel; this allows for parameterizing the activation of chemically complex aerosol with an arbitrary size distribution and mixing state. The new parameterization introduces the concept of ""population splitting,"" in which the cloud condensation nuclei (CCN) that form droplets are treated as two separate populations: those that have a size close to their critical diameter and those that do not. Explicit consideration of kinetic limitations on droplet growth is introduced. Our treatment of the activation process unravels much of its complexity. As a result of this, a substantial number of conditions of droplet formation can be treated completely free of empirical information or correlations; there are, however, some conditions of droplet activation for which an empirically derived correlation is utilized. Predictions of the parameterization are compared against extensive cloud parcel model simulations for a variety of aerosol activation conditions that cover a wide range of chemical variability and CCN concentrations. The parameterization tracks the parcel model simulations closely and robustly. The parameterization presented here is intended to allow for a comprehensive assessment of the aerosol indirect effect in general circulation models."
"57196676724;7102805852;","Solar radiative forcing by biomass burning aerosol particles during SAFARI 2000: A case study based on measured aerosol and cloud properties",2003,"10.1029/2002jd002315","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742287623&doi=10.1029%2f2002jd002315&partnerID=40&md5=67344d93d2d16710b99fb4a89bd4a0da","This study investigates the top of atmosphere (TOA) solar radiative forcing by biomass burning aerosol from the African continent. Radiative transfer calculations are based on airborne aerosol and cloud measurements made on 7 September 2000, being representative for the aerosol optical properties and the relative location of aerosol and clouds during Southern African Fire-Atmosphere Research Initiative (SAFARI) 2000. We focus on how the radiative effects of biomass aerosol are changed in the presence of clouds to the west of the southern African coastline. The typical scenario observed showed a clear separation between an elevated biomass aerosol layer (1.8-3.7 km altitude) and low-level stratiform clouds (below 1 km, liquid water path 85 g m-2). The aerosol was characterized by particle concentrations of 1800 cm-3 and a single scattering albedo at 550 nm wavelength of around 0.90. Presuming no effect by the biomass aerosol on the clouds themselves, the presence of clouds converted the negative TOA forcing by the biomass aerosol in clear skies into a positive one (-13.0 W m-2 converted to + 11.5 W m-2 for average optical properties of the biomass aerosol and a solar zenith angle of 60°). As biomass aerosol was found above cloud thousands of kilometers away from the southern African coastline, positive direct TOA forcings can be expected in extended sea areas over the Namibian cloud sheet. These results suggest errors in global climate model (GCM) modeling assessments of the direct radiative forcing due to biomass aerosols. Additionally, we estimate the possibility that a potential indirect effect dominates the overall forcing, resulting generally in strong negative TOA forcings."
"7003976079;57193920163;7004034323;","Simulation of satellite channel radiances in the Met Office Unified Model",2003,"10.1256/qj.02.61","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037255456&doi=10.1256%2fqj.02.61&partnerID=40&md5=0c9bdad02ddcdb67be3d4fc2d93dc1ff","A system is described which allows satellite channel radiances to be simulated within both the numerical weather prediction and climate versions of the Met Office Unified Model. It is based on a spherical harmonics version of the radiation code that calculates radiative fluxes and heating rates in the climate model and it uses the same pre-processing software and molecular absorption database. In the results shown here, fractional cloud cover is represented by decomposition into separate columns. The methodology is described and results of off- line tests of the code against high spectral resolution calculations are presented. Examples of infrared window and water vapour channel brightness temperatures simulated using the global forecast model are then compared with Meteosat 7 imagery. The utility of radiance simulations for model validation studies is illustrated by these comparisons, and other applications are also discussed."
"6603868770;6603196991;","Accuracy of cloud liquid water path from ground-based microwave radiometry 2. Sensor accuracy and synergy",2003,"10.1029/2002rs002634","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042384796&doi=10.1029%2f2002rs002634&partnerID=40&md5=84a32abc491ad11231cafbe68e1b57e0","The influence of microwave radiometer accuracy on retrieved cloud liquid water path (LWP) was investigated. Sensor accuracy was assumed to be the sum of the relative (i.e., Gaussian noise) and the absolute accuracies of brightness temperatures. When statistical algorithms are developed the assumed noise should be as close as possible to the real measurements in order to avoid artifacts in the retrieved LWP distribution. Typical offset errors of 1 K in brightness temperatures can produce mean LWP errors of more than 30 g m-2 for a two-channel radiometer retrieval, although positively correlated brightness temperature offsets in both channels reduce this error to 16 g m-2. Large improvements in LWP retrieval accuracy of about 50% can be achieved by adding a 90-GHz channel to the two-channel retrieval. The inclusion of additional measurements, like cloud base height from a lidar ceilometer and cloud base temperature from an infrared radiometer, is invaluable in detecting cloud free scenes allowing an indirect evaluation of LWP accuracy in clear sky cases. This method was used to evaluate LWP retrieval algorithms based on different gas absorption models. Using two months of measurements, the Liebe 93 model provided the best results when the 90-GHz channel was incorporated into the standard two-channel retrievals."
"7102055821;7401436524;55715215300;7406250414;8546937700;","The impact of low-level cloud over the Eastern Subtropical Pacific on the ""Double ITCZ"" in LASG FGCM-0",2003,"10.1007/BF02690804","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0142156174&doi=10.1007%2fBF02690804&partnerID=40&md5=42bf226b9e9c12d4fa14e6c82760bdda","Like many other coupled models, the Flexible coupled General Circulation Model (FGCM-0) suffers from the spurious ""Double ITCZ"". In order to understand the ""Double ITCZ"" in FGCM-0, this study first examines the low-level cloud cover and the bulk stability of the low troposphere over the eastern subtropical Pacific simulated by the National Center for Atmospheric Research (NCAR) Community Climate Model version 3 (CCM3), which is the atmosphere component model of FGCM-0. It is found that the bulk stability of the low troposphere simulated by CCM3 is very consistent with the one derived from the National Center for Environmental Prediction (NCEP) reanalysis, but the simulated low-level cloud cover is much less than that derived from the International Satellite Cloud Climatology Project (ISCCP) D2 data. Based on the regression equations between the low-level cloud cover from the ISCCP data and the bulk stability of the low troposphere derived from the NCEP reanalysis, the parameterization scheme of low-level cloud in CCM3 is modified and used in sensitivity experiments to examine the impact of low-level cloud over the eastern subtropical Pacific on the spurious ""Double ITCZ"" in FGCM-0. Results show that the modified scheme causes the simulated low-level cloud cover to be improved locally over the cold oceans. Increasing the low-level cloud cover off Peru not only significantly alleviates the SST warm biases in the southeastern tropical Pacific, but also causes the equatorial cold tongue to be strengthened and to extend further west. Increasing the low-level cloud fraction off California effectively reduces the SST warm biases in ITCZ north of the equator. In order to examine the feedback between the SST and low-level cloud cover off Peru, one additional sensitivity experiment is performed in which the SST over the cold ocean off Peru is restored. It shows that decreasing the SST results in similar impacts over the wide regions from the southeastern tropical Pacific northwestwards to the western/central equatorial Pacific as increasing the low-level cloud cover does."
"56054901100;","New developments in using solar cells as remote sensors to gauge climate change",2003,"10.1306/eg100202051","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4644291989&doi=10.1306%2feg100202051&partnerID=40&md5=280e2f68d7205fc99c4f56359bc8198e","Earth's albedo is the fraction between the radiation reflected outside and the incident solar radiation, and regional albedo is this parameter obtained in the nadir point of a satellite. This work describes a new self-calibrated method for the assessment of albedo using the telemeterized data from the solar cell experiment of the second data collection satellite, second ""Satelite de Copeta de Dados"" (SCD2), launched on October 1998. A numerical simulation shows that the albedo data of this experiment is a function of the local weather condition (clouds). The continuous monitoring of this data permits one to infer climate change. This work shows and makes analysis of albedo in three cities of Brazil (South America) during 1999 and 2000, which have different climate conditions. The albedo graphics help explain the climate behavior in these regions. The experiment and the method of this work may establish a cost-effective innovation for space programs. © 2003. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved."
"7006847648;26643250500;7102862273;6602914876;57203053317;7004292082;7006107059;","Freezing thresholds and cirrus cloud formation mechanisms inferred from in situ measurements of relative humidity",2003,"10.5194/acp-3-1791-2003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949120427&doi=10.5194%2facp-3-1791-2003&partnerID=40&md5=3d966d19c990cb47a6f82d9d4e522298","Factors controlling the microphysical link between distributions of relative humidity above ice saturation in the upper troposphere and lowermost stratosphere and cirrus clouds are examined with the help of microphysical trajectory simulations. Our findings are related to results from aircraft measurements and global model studies. We suggest that the relative humidities at which ice crystals form in the atmosphere can be inferred from in situ measurements of water vapor and temperature close to, but outside of, cirrus clouds. The comparison with concomitant measurements performed inside cirrus clouds provides a clue to freezing mechanisms active in cirrus. The analysis of field data taken at northern and southern midlatitudes in fall 2000 reveals distinct differences in cirrus cloud freezing thresholds. Homogeneous freezing is found to be themost likely mechanismby which cirrus form at southern hemisphere midlatitudes. The results provide evidence for the existence of heterogeneous freezing in cirrus in parts of the polluted northern hemisphere, but do not suggest that cirrus clouds in this region form exclusively on heterogeneous ice nuclei, thereby emphasizing the crucial importance of homogeneous freezing. The key features of distributions of upper tropospheric relative humidity simulated by a global climate model are shown to be in general agreement with both, microphysical simulations and field observations, delineating a feasible method to include and validate ice supersaturation in other largescale atmospheric models, in particular chemistry-transport and weather forecast models. © 2003 European Geosciences Union."
"35609833400;7005921461;","Analysis of convective precipitation in the western Mediterranean Sea through the use of cloud-to-ground lightning",2003,"10.1016/S0169-8095(02)00160-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037389845&doi=10.1016%2fS0169-8095%2802%2900160-6&partnerID=40&md5=a386537d5197b7c687faaa87c408324c","The monthly convective precipitation (CP) and convective precipitation rate (CPR) over the western Mediterranean Sea are estimated using cloud-to-ground lightning flashes for the June to October period using data of 3 years (1992-1994). Rain yield was computed using the precipitation data from seven observing stations (all equipped with rain gauges) located on the Mediterranean coast of the Iberian Peninsula and in the Balearic Islands. The values obtained were 0.93 × 108 kg/fl for the negative flashes and 20.63 × 108 kg/fl for the positive flashes. Convective precipitation over sea was estimated from the rain yield using the cloud-to-ground (CG) lightning activity detected by a lightning detection network. Because no measured data on precipitation over sea are available, the estimated convective precipitation was compared with the monthly diagnostic surface convective precipitation data from the NOAA NCEP/NCAR climate data assimilation system. Analysis of the results revealed that convective precipitation over the western Mediterranean Sea is maximum in the months September and October and near the northeastern coast of the Iberian Peninsula (maximum in the order of 240 mm/month). The convective precipitation rate exhibits less time variability than convective precipitation, although its spatial distribution is similar. © 2002 Elsevier Science B.V. All rights reserved."
"36950518200;56132618000;7006319396;","The cloud radiative forcing over Asian-Pacific summer monsoon region",2003,"10.3319/TAO.2003.14.4.445(A)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342331600&doi=10.3319%2fTAO.2003.14.4.445%28A%29&partnerID=40&md5=29ec1fe21279c9a6e48477e1ee7e8419","The strength of the Asian-Pacific summer monsoon (APSM) is associated with intensities from two major convective heat sources centered primarily over the Bay of Bengal (BB) and the western North Pacific (WNP). Because of the complexity of the APSM, especially over WNP, almost all of the general circulation models (GCMs) cannot simulate the climate features around the Asian monsoon region satisfactorily. This could be due to the inability of the GCMs to simulate correct cloud formations and radiative properties of clouds. In this study we will focus on the role of clouds and cloud radiative forcing (CRF) in the evolution of the APSM. Our study relies on radiative fluxes at the top of the atmosphere from the Earth Radiation Budget Experiment (ERBE) and cloud data from the International Satellite Cloud Climatology Project (ISCCP-D1) to inquire about some common properties of CRF in the four regions of East and Southern Asia: the BB, South China Sea (SCS), WNP, and Central China (CC). During the APSM, we arrived at the following conclusions: After the onset of the summer monsoon, there is a lower OLR and a larger high cloud fraction with heavy and persistent rainfall in the BB throughout the whole summer. At the same time, extremely dense clouds (with thick optical depth) reaching into the higher atmosphere associated with strong convergence in the lower layers and divergences over the upper troposphere persistently occur in the BB. The strong dynamic force associated with closed spaced convective updrafts, as in BB, can result in a significant negative CRF (as low as -70 W m-2). However, WNP and SCS are different from BB, not only in the CRF but also in the cloud's temporal and spatial distributions. A brief recess of deep convection occurs in mid-July in WNP and SCS, which causes the magnitude of precipitation, cloud amount, optical depth and CRF for the entire summer to average less than in BB. In both WNP and SCS, individual elements within the convective cloud system show a wide range of net radiative forcing (from the thick anvil clouds near convective cores to thin cirrus clouds near the edges of the anvil cloud) which produces a net CRF of near zero when averaged over the convective cloud system. Through spectral analysis of high cloud amounts, we can find that over BB, the highest power is in the period around 75 days, which is the intraseasonal timescale. While over WNP, the leading spectral peaks are at 10-20 days and 8-9 days. These two dominant frequencies are definitely related to the fast annual cycle (proposed by LinHo and Wang). Failure to simulate correctly these two frequencies may be the primary reason why the GCMs exhibit great difficulty in reproducing correct precipitation in the WNP. The cloud structures and CRF in CC are very different from the oceanic regions in our analysis and where mid-low level clouds with thick optical depths play more of a role than does the high, thin cloud."
"25953950400;35453054300;7004134577;7003377229;6602365657;55017656900;6701521849;7202784114;7202358048;6507731482;35451476400;","RAMS 2001: Current status and future directions",2003,"10.1007/s00703-001-0584-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038283849&doi=10.1007%2fs00703-001-0584-9&partnerID=40&md5=7e6f1114b507b974956b893d5d742244","An overview of the Regional Atmospheric Modeling System (RAMS) is presented. We focus on new developments in the RAMS physics and computational algorithms since 1992. We also summarize some of the recent applications of RAMS that includes synoptic-scale weather systems and climate studies, to small-scale research using RAMS configured as a large eddy simulation model or to even flow around urban buildings. The applications include basic research on clouds, cloud systems, and storms, examination of interactions between tropical deep convective systems and ocean circulations, simulations of tropical cyclones, extreme precipitation estimation, regional climatic studies of the interactions between the atmosphere and the biosphere or snow-covered land-surfaces, prototype realtime mesoscale numerical weather prediction, air pollution applications, and airflow around buildings."
"35570389600;7004942632;6602831555;8326850700;7004194999;24511929800;","A comparison of climate response to different radiative forcings in three general circulation models: Towards an improved metric of climate change",2003,"10.1007/s00382-003-0305-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038375955&doi=10.1007%2fs00382-003-0305-9&partnerID=40&md5=8d632dc9d3bca371e54af00e6d86dd2e","In order to review, and possibly refine, the concept of radiative forcing as a suitable metric for climate change, the responses of three general circulation models to distinct forcing scenarios are compared. CO2, solar radiation, and O3 are added in different locations, whilst keeping the globally averaged radiative forcing constant at 1 Wm-2. The three models react differently to the forcings, as feedback mechanisms such as sea-ice albedo and clouds behave differently in each model. However, we find that their climate sensitivities λ (defined as the ratio of the globally averaged surface temperature change to the radiative forcing), normalised by the climate sensitivity for a control case (e.g. CO2 added globally), match each other to within 30% in most experiments. Moreover, the models indicate generic deviations of λ from the case of global CO2 perturbations: upper tropospheric O3 increases generally produce lower values of λ, while lower stratospheric O3 perturbations lead to higher values of λ, as found in some previous work. λ tends to be higher for extratropical forcings than tropical forcings; a phenomenon which can be partially accounted for by a new explanation based on the variation of the outgoing longwave radiation with latitude. Our results suggest that if the radiative forcing associated with some perturbation is multiplied by some factor accounting for the efficiency of that mechanism, then such modified forcings can be compared more robustly than the forcings themselves."
"7006241374;22973650100;7003512303;","Major Δ 14C excursions during the late glacial and early Holocene: Changes in ocean ventilation or solar forcing of climate change?",2003,"10.1016/s1040-6182(02)00152-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037268383&doi=10.1016%2fs1040-6182%2802%2900152-0&partnerID=40&md5=5c83b28008d2dca5af85fae2a65c59a1","The atmospheric 14C record during the Late Glacial and the early Holocene shows sharp increases simultaneous with cold climatic phases. These increases in the atmospheric 14C content are usually explained as the effect of reduced occanic CO2 ventilation after episodic outbursts of large meltwater reservoirs into the North Atlantic. In this hypothesis the stagnation of the thermohaline circulation is the cause of both climate change as well as an increase in atmospheric 14C. As an alternative hypothesis we propose that changes in 14C production give an indication for the cause of the recorded climate shifts: changes in solar activity cause fluctuations in the solar wind, which modulate the cosmic ray intensity and related 14C production. Two possible mechanisms amplifying the changes in solar activity may result in climate change. In the case of a temporary decline in solar activity: (1) reduced solar UV intensity may cause a decline of stratospheric ozone production and cooling as a result of less absorption of sunlight. This might influence atmospheric circulation patterns (extension of Polar Cells and equatorward relocation of mid-latitude storm tracks), with effects on oceanic circulation, and (2) increased cosmic ray intensity may stimulate cloud formation and precipitation, while 14C production increases. © 2002 Elsevier Science Ltd and INQUA. All rights reserved."
"7004469363;7004013316;","Can solar variability explain global warming since 1970?",2003,"10.1029/2002JA009753","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892021717&doi=10.1029%2f2002JA009753&partnerID=40&md5=e9f03141a89bd984b4da04a360668236","The magnitude of the Sun's influence on climate has been a subject of intense debate. Estimates of this magnitude are generally based on assumptions regarding the forcing due to solar irradiance variations and climate modeling. This approach suffers from uncertainties that are difficult to estimate. Such uncertainties are introduced because the employed models may not include important but complex processes or mechanisms or may treat these in too simplified a manner. Here we take a more empirical approach. We employ time series of the most relevant solar quantities, the total and UV irradiance between 1856 and 1999 and the cosmic rays flux between 1868 and 1999. The time series are constructed using direct measurements wherever possible and reconstructions based on models and proxies at earlier times. These time series are compared with the climate record for the period 1856 to 1970. The solar records are scaled such that statistically the solar contribution to climate is as large as possible in this period. Under this assumption we repeat the comparison but now including the period 1970-1999. This comparison shows without requiring any recourse to modeling that since roughly 1970 the solar influence on climate (through the channels considered here) cannot have been dominant. In particular, the Sun cannot have contributed more than 30% to the steep temperature increase that has taken place since then, irrespective of which of the three considered channels is the dominant one determining Sun-climate interactions: tropospheric heating caused by changes in total solar irradiance, stratospheric chemistry influenced by changes in the solar UV spectrum, or cloud coverage affected by the cosmic ray flux. Copyright 2003 by the American Geophysical Union."
"7202772927;35467186900;57214502541;7201804746;7201844203;7005045912;55699179200;7005742394;7401701196;7006191743;6701681018;7006423931;7006329926;36616626800;7006191878;","Microphysics, radiation and surface processes in the Goddard Cumulus Ensemble (GCE) model",2003,"10.1007/s00703-001-0594-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0345329910&doi=10.1007%2fs00703-001-0594-7&partnerID=40&md5=833ebf1cdc190080528178f862997898","The response of cloud systems to their environment is an important link in a chain of processes responsible for monsoons, frontal depression, El Nĩno-Southern Oscillation (ENSO) episodes and other climate variations (e.g., 30-60 day intra-seasonal oscillations). Numerical models of cloud properties provide essential insights into the interactions of clouds with each other, with their surroundings, and with land and ocean surfaces. Significant advances are currently being made in the modeling of rainfall and rain-related cloud processes, ranging in scales from the very small up to the simulation of an extensive population of raining cumulus clouds in a tropical- or midlatitude-storm environment. The Goddard Cumulus Ensemble (GCE) model is a multi-dimensional non-hydrostatic dynamic/microphysical cloud resolving model. It has been used to simulate many different mesoscale convective systems that occurred in various geographic locations. In this paper, recent GCE model improvements (microphysics, radiation and surface processes) will be described as well as their impact on the development of precipitation events from various geographic locations. The performance of these new physical processes will be examined by comparing the model results with observations. Specifically, the impact of different ice schemes (i.e., three-class ice scheme, four-class two-moment ice scheme) on precipitation processes are examined and compared. Spectral bin microphysics are used to investigate precipitation processes under clean and dirty environments. The coupled GCE-radiation model shows that the modulation of relative humidity by radiative processes is the main reason for the diurnal variation of precipitation in the tropics. The coupled GCE-land surface model is used to examine the impact of heterogeneous land surface characteristics (soil-vegetation) on precipitation processes. The effect of ocean flux algorithms (e.g., the TOGA COARE flux algorithm and a simple bulk aerodynamic method) on surface fluxes, environmental convective available potential energy (CAPE) and precipitation processes are compared. In addition, the coupled GCE-ocean mixed layer (OML) model is used to investigate the physical processes that affect the variation of sea surface temperature, mixed layer depth and salinity."
"55547107844;7404976222;7406308680;","Energy budget bias in global coupled ocean-atmosphere-land model",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042739763&partnerID=40&md5=2061064eec7e7207a3583a69585048a4","The energy budget of the two versions of the GOALS model (GOALS-1.1 and GOALS-2) is described and compared to observational estimates. The results illustrate that the simulated surface net shortwave radiation flux is underestimated in the high-latitude regions while the surface net longwave radiation flux is substantially overestimated in that region, which results in the lower surface air temperature (SAT) of the polar region and the stronger negative sensible heat flux in high latitudes. The overestimated sensible heat flux from surface to atmosphere in the continents causes the much warmer SAT centers, which may be the reason for the bias of the model SAT. The bias that the simulated precipitation is less than observation in most regions is closely related to the underestimated latent heat flux over most of the Eurasian Continent and the oceans, especially over the subtropical oceans. It can be seen that the bias in the OLR of the two models lies in low and middle latitudes, where the absorbed solar shortwave radiation flux at the top of the atmosphere is comparable to the NCEP reanalysis, but much less than ERBE data. This indicates that the improvement of cloud-radiation parameterization scheme in low and middle latitudes is of critical importance to the simulation of global energy budget. The simulated cloud cover from the GOALS-2 model with diagnosed cloud scheme is generally less except at equatorial areas, especially in the mid-latitude areas, which causes the large bias of energy budget there. It is suggested that the refinement of cloud parameterization is one of the most important tasks in the model's future development."
"6603707613;","Signatures of solar activity variability in meteorological parameters",2003,"10.1016/S1364-6826(02)00295-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037374595&doi=10.1016%2fS1364-6826%2802%2900295-X&partnerID=40&md5=52b461fa9258babdfcbab108a51dc3e1","Solar radiation (both total and in various wavelengths) varies at different time scales-from seconds to decades or centuries-as a consequence of solar activity. The energy received from the Sun is one of the natural driving forces of the Earth's atmosphere and since this energy is not constant, it has been argued that there must be some non-zero climate response to it. This response must be fully specified in order to improve our understanding of the climate system and the impact of anthropogenic activities on it. However, despite all the efforts, if and how subtle variations of solar radiation affect climate and weather still remains an unsolved puzzle. One key element that is very often taken as evidence of a response, is the similarity of periodicities between several solar activity indices and different meteorological parameters. The literature contains a long history of positive or negative correlations between weather and climate parameters like temperature, rainfall, droughts, etc. and solar activity cycles like the 27-day cycle, the prominent 11-year sunspot cycle, the 22-year Hale cycle and the Gleissberg cycle of 80-90 years. A review of these different cycles is provided as well as some of the correlative analyses between them and several stratospheric parameters (like stratospheric geopotential heights, temperature and ozone concentration) and tropospheric parameters (like temperature, rainfall, water level in lakes and river flooding, clouds) that point to a relationship of some kind. However, the suspicion on these relationships will remain as long as an indisputable physical mechanism, which might act to produce these correlations, is not available. © 2003 Elsevier Science Ltd. All rights reserved."
"57191076887;6506688395;8729829000;8125488700;36865248900;8125488900;7003699073;","Activities of sprites and elves in the winter season, Japan",2003,"10.1016/S1364-6826(02)00330-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037737966&doi=10.1016%2fS1364-6826%2802%2900330-9&partnerID=40&md5=544c593550af2e35218b8d5bd4084470","Sprites and elves observation has been carried out in three winter seasons in Japan since December 1998. Thirtyfive sprites' features have been imaged with CCD cameras and 95 optical emission from elves have been captured with hi-speed array photometers. The number of events observed on a night is dependent on the occurrence of intense cloud to ground lightning activity and cloud condition above the observation site. Most of the sprites/elves are directly associated with storms produced by a cold front passing over Japan. It is found that sprites/elves appear not only in the west coast of Japan but also above the Pacific Ocean. The average vertical length of winter sprites in the west cost is shorter than that of summer sprites in the US by about a factor of 2. The altitude of the causative thunderstorm for winter sprites and elves is comparatively lower than that of the summer events in the US and the horizontal width of the cloud is sometimes smaller than 30 km. The sprites' detection in winter in Japan suggests the possibility of winter sprite occurrence in Scandinavia and/or Israel where the climate condition is similar to Japan. © 2003 Elsevier Science Ltd. All rights reserved."
"26643250500;7102862273;","The roles of dynamical variability and aerosols in cirrus cloud formation",2003,"10.5194/acp-3-823-2003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642584560&doi=10.5194%2facp-3-823-2003&partnerID=40&md5=db85cac57eeb03350e98224f1ce532ee","The probability of occurrence of ice crystal number densities in young cirrus clouds is examined based on airborne measurements. The observations have been carried out at midlatitudes in both hemispheres at equivalent latitudes (52 - 55° N/S) during the same season (local autumn in 2000). The in situ measurements considered in the present study include temperatures, vertical velocities, and total ice crystal concentrations, the latter determined with high precision and accuracy using a counterflow virtual impactor. Most young cirrus clouds typically contain high number densities (1-10 cm-3) of small (diameter &gt; 20μm) ice crystals. This mode dominates the probability distributions and is shown to be caused by rapid cooling rates associated with updraft speeds in the range 10 - 100 cm s-1. A second mode containing larger crystals extends from ∼ 1 cm-3 to low concentrations close to the detection threshold (∼ 3 × 10-4 cm -3) and could be associated with lower updraft speeds. Results of a statistical analysis provide compelling evidence that the dynamical variability of vertical air motions on the mesoscale is the key factor determining the observed probability distributions of pristine ice crystal concentrations in cirrus. Other factors considered are changes of temperature as well as size, number, and ice nucleation thresholds of the freezing aerosol particles. The variability in vertical velocities is caused by atmospheric gravity waves leading to small-scale temperature fluctuations. Inasmuch as gravity waves are widespread, mesoscale variability in vertical velocities can be viewed as a universal feature of young cirrus clouds. Large-scale models that do not account for this subgrid-scale variability yield erroneous predictions of the variability of basic cirrus cloud properties. Climate change may bring about changes in the global distribution of updraft speeds, mean air temperatures, and aerosol properties. As shown in this work, these changes could significantly modify the probability distribution of cirrus ice crystal concentrations. This study emphasizes the key role of vertical velocities and mesoscale variability in vertical velocities in controlling cirrus properties. The results suggest that, in any effort to ascribe cause to trends of cirrus cloud properties, a careful evaluation of dynamical changes in cloud formation should be done before conclusions regarding the role of other anthropogenic factors, such as changes in aerosol composition, are made. © 2003 European Geosciences Union."
"7403159332;7202367208;","Factors contributing to diurnal temperature range trends in twentieth and twenty-first century simulations of the CCCma coupled model",2003,"10.1007/s00382-002-0288-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037654727&doi=10.1007%2fs00382-002-0288-y&partnerID=40&md5=853ce8806702baeb38e9ebb5f7bba046","Trends in the diurnal temperature range (DTR) are examined in the late twentieth and the twenty-first centuries in a coupled climate model representing the atmosphere, ocean, sea ice, and land surface systems. Consistent with past studies, the DTR decreases during this time. These decreases are concentrated in middle latitudes, with much smaller changes occurring in the low latitudes. Strong seasonal characteristics to this pattern exist, although these are different in either hemisphere. In the model integrations, variations in the DTR are much more sensitive to changes in feedbacks than in direct forcings. The DTR is found to be insensitive to the scattering of sunlight by sulfate aerosols and the increased mean temperature. Instead, variations in the DTR arise mostly from changes in clouds and in soil moisture. Consequently, the decreasing trends stem from increases in the reflection of solar radiation by clouds moderated by decreases in soil moisture, mostly through its effect on the ground heat capacity. Both factors contribute about equally to the DTR trend. The exception to this relation occurs in the middle latitudes during winter, when snow cover reduces the influence of changes in solar radiation and soil moisture. Decreases during this season are a consequence of the artificial tendency in the model for the DTR to be very small when the mean temperature is near the freezing point. While the accuracy of these conclusions depends upon the model's ability to represent the relevant processes, the results highlight the importance of clouds and land surface processes to the DTR and its long-term change. The importance of soil moisture found here implies that changes in the physiological response of vegetation and in land use could have important effects on the DTR."
"57209147154;7101667328;56228672600;","Enhanced climatic warming in the Tibetan Plateau due to doubling CO2: A model study",2003,"10.1007/s00382-002-0282-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037301744&doi=10.1007%2fs00382-002-0282-4&partnerID=40&md5=d376bc685a631346260aa89310da66eb","The National Center for Atmospheric Research (NCAR) regional climate model (RegCM2), together with initial conditions and time-dependent lateral boundary conditions provided by a 130-year transient increasing CO2 simulation of the NCAR Climate System Model (CSM), has been used to investigate the mechanism of ground warming over the Tibetan Plateau (TP). The model results show that when CO2 in the atmosphere is doubled, a strong ground warming occurs in the TP. Two regions within it with the largest warming are in the eastern TP (region I) and along the southwestern and western slopes (region II). Moreover, in region I the ground warming in the winter half year is stronger than that in the summer half year, but in region II the warming difference between the seasons becomes opposite to that in region I, i.e., the warming is strong in the summer half year and weak in the winter half year. There are indications that the summer monsoon enhances but the winter monsoon weakens when CO2 is doubled. A strong elevation dependency of ground warming is found in region I for the winter half year, and in region II for both winter and summer half years at elevations below 5 km. The simulated characteristics of ground warming in the TP are consistent with the observations. In region I, when CO2 is doubled, the cloud amount increases at lower elevations and decreases at higher elevation for the winter half year. As a consequence, at lower elevations the short wave solar radiation absorbed at the surface declines, and the downward long wave flux reaching the surface enhances; on the other hand, at higher elevations the surface solar radiation flux increases and the surface infrared radiation flux shows a more uniform increase. The net effect of the changes in both radiation fluxes is an enhanced surface warming at higher elevations, which is the primary cause of the elevation dependency in the surface warming. In the summer half year the cloud amount reduces as a result of doubling CO2 in region I for all elevations, and there is no elevation dependency detected in the ground warming. Furthermore, there is little snow existing in region I for both summer and winter half years, and the impact of snow-albedo feedback is not significant. In region II, although the changes in the cloud amount bear a resemblance to those in region I, the most significant factor affecting the surface energy budget is the depletion of the snow cover at higher elevations, which leads to a reduction of the surface albedo. This reduction in turn leads to an enhancement in the solar radiation absorbed in the surface. The snow-albedo feedback mechanism is the most essential cause of the elevation dependency in the surface warming for region II."
"6701590980;","Empirical estimation of the monthly-mean daily temperature range",2003,"10.1007/s00704-002-0715-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037994206&doi=10.1007%2fs00704-002-0715-3&partnerID=40&md5=c04ad609fa04b5cf804020235bbe14a5","This is a sequel to a study of the empirical estimation of the annual mean temperature and its range, at any location on land, based on the historical surface climate record. Here the spatial patterns of the daily temperature range (DTR) and its seasonal variation are examined. The DTR is highest in the subtropical deserts and is less at high latitudes, as well as within 30-150 km from an ocean. It is generally higher in winter (summer) at low (high) latitudes. The coastal DTR reduction is explained by sea breezes, onshore advection, and low-level cloud cover. Even large bodies of water, such as Lake Michigan, affect the near-shore DTR. Elevation does not directly affect the DTR, but valleys tend to have a DTR that is 2-6 K larger than adjacent hills or ridges. The main factor affecting the DTR is the afternoon relative humidity, which is dynamically linked to low-level cloud cover. An empirical relationship between DTR and afternoon relative humidity has an uncertainty of about 1.4 K for monthly-mean values."
"6602176524;6701481007;","Observed variability of North Atlantic oceanic precipitating systems during winter",2003,"10.1029/2002jd003343","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742270498&doi=10.1029%2f2002jd003343&partnerID=40&md5=ad56a4673052130d421eb9e468039d5e","The variability of large precipitating weather systems as observed from polar satellites over the North Atlantic Ocean is investigated using a statistical analysis. Nine winters (from 1987 to 1995) have been considered. Cloud systems and troughs over the area 40-60°N, 70-10°W are automatically detected with retrievals of the cloud top pressure, a precipitation index, and the temperature of the lower stratosphere. A classification of the largest precipitating systems as characterized by these variables leads to eight classes, whose occurrence significantly differs over the years. It also shows the systematic presence of a trough upstream of the precipitating area covered by high-level clouds, as expected in the case of baroclinic interaction. In order to understand the large interannual variability an attempt to identify systematic differences in cyclone structures during different flow regimes is then performed. It shows that the large-scale (typically 3000 km wide) and zonally elongated cloud systems are observed mainly to the south of 45°N when the phase of the Arctic Oscillation (AO) is negative (which also corresponds to the Greenland Anticyclone regime). Conversely, zonally elongated cloud systems of smaller scale (1000 km wide) associated with frontal waves are favored also to the south but during the positive AO phase (particularly during zonal regimes). The most tilted weather systems, without any preferential AO phase, are found mostly during the blocking regime. These systems are cyclonically tilted in the northeastern branch of the storm track and anticyclonically tilted in the southwestern branch. It must be noted that similar results are obtained when the AO daily index is replaced by the North Atlantic Oscillation index. This analysis gives observational evidence of previous idealized simulations linking the large-scale circulation to preferential life cycles of weather systems. In addition, a weak response to extreme El Niño Southern Oscillation events has been observed in the location of cyclones but not in their average structure."
"57205342499;7403253358;55878640000;","An improvement of the mass flux convection parameterization scheme and its sensitivity test for seasonal prediction over China",2003,"10.1007/bf02915521","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346907334&doi=10.1007%2fbf02915521&partnerID=40&md5=54b58ebeec0253eabea2e1ef9ff0ec09","A modified cumulus parameterization scheme, suitable for use in a seasonal forecast model, is presented. This parameterization scheme is an improvement of the mass flux convection scheme developed by Gregory and Rowntree (1989; 1990). This convection scheme uses a ""bulk"" cloud model to present an ensemble of convective clouds, and aims to represent shallow, deep, and mid-level convection. At present, this convection scheme is employed in the NCC T63L20 model (National Climate Center, China Meteorological Administration). Simulation results with this scheme have revealed some deficiencies in the scheme, although to some extent, it improves the accuracy of the simulation. In order to alleviate the deficiencies and reflect the effect of cumulus convection in the actual atmosphere, the scheme is modified and improved. The improvements include (i) the full estimation of the effects of the large-scale convergence in the lower layer upon cumulus convection, (ii) the revision of the initial convective mass flux, and (iii) the regulation of convective-scale downdrafts. A comparison of the results obtained by using the original model and the modified one shows that the improvement and modification of the original convection scheme is successful in simulating the precipitation and general circulation field, because the modified scheme provides a good simulation of the main features of seasonal precipitation in China, and an analysis of the anomaly correlation coefficient between the simulation and the observations confirms the improved results."
"6507986327;6602624799;","Objective method for classifying air masses: An application to the analysis of Buenos Aires' (Argentina) urban heat island intensity",2003,"10.1007/s00704-002-0714-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037286254&doi=10.1007%2fs00704-002-0714-4&partnerID=40&md5=16f55adbd71288450794b69d07b66fd8","During recent years, numerous studies have examined the Buenos Aires urban climate, but the relationship between large-scale weather conditions and the Buenos Aires urban heat island (UHI) intensity has not been studied. The goal of this paper is to apply an objective synoptic climatological method to identify homogeneous air masses or weather types affecting Buenos Aires during winter, and to relate the results to the UHI intensity. A K-means clustering method was used to define six different air masses considering the 03:00, 09:00, 15:00 and 21:00 LT surface observations of dry bulb temperature, dew point, cloud cover, atmospheric pressure and wind direction and velocity at Ezeiza, the most rural meteorological station of the Buenos Aires metropolitan area. Results show that the mean UHI intensity is at its maximum (2.8°C) a few hours before sunrise when conditions are dominated by cold air masses associated with cold-core anticyclones, weak winds and low cloud cover. Inverse heat islands are found during the afternoon for all air masses indicating that surface processes are not dominant at that time. The relatively infrequent and warmest air mass is the only one that presents a mean negative urban-rural temperature difference (-0.1°C) during the afternoon with the smallest diurnal cycle of the UHI intensity probably due to the prevailing high humidity and cloudy sky conditions. The paper provides an insight into the Buenos Aires urban-rural temperature difference under a variety of winter weather types and results could be useful to improve local daily temperature forecasts for the metropolitan area of Buenos Aires on the basis of the routine forecasts of weather types."
"8602676200;7404232143;55388515800;7406099977;","Characteristics of the heat island effect in Shanghai and its possible mechanism",2003,"10.1007/bf02915522","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0348167908&doi=10.1007%2fbf02915522&partnerID=40&md5=7843cf2557423bd91b9ca5b1c903c46c","The characteristics of the urban heat island effect and the climate change in Shanghai and its possible mechanism are analyzed based on monthly meteorological data from 1961 to 1997 at 16 stations in Shanghai and its adjacent areas. The results indicate that Shanghai City has the characteristics of a heat island of air temperature and maximum and minimum air temperature, a cold island of surface soil temperature, a weak rainy island of precipitation, and a turbid island of minimum visibility and aerosols, with centers at or near Longhua station (the urban station of Shanghai). Besides theses, the characteristics of a cloudy island and sunshine duration island are also obvious, but their centers are located in the southern part of the urban area and in the southern suburbs. A linear trend analysis suggests that all of the above urban effects intensified from 1961 to 1997. So far as the heat island effect is concerned, the heat island index (difference of annual temperature between Longhua and Songjiang stations) strengthens (weakens) as the economic development increases (decreases). The authors suggest that the heating increase caused by increasing energy consumption due to economic development is a main factor in controlling the climate change of Shanghai besides natural factors. On the other hand, increasing pollution aerosols contribute to the enhancement of the turbid island and cooling. On the whole, the heating effect caused by increasing energy consumption is stronger than the cooling effect caused by the turbid island and pollution aerosols."
"7201707877;6603489730;","Validation of a watershed model without calibration",2003,"10.1029/2002WR001940","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1542436773&doi=10.1029%2f2002WR001940&partnerID=40&md5=d7cf73ae2e0b67d51248ffc594605ef6","Traditional approaches for the validation of watershed models focus on the ""goodness of fit"" between model predictions and observations. It is possible for a watershed model to exhibit a ""good"" fit, yet not accurately represent hydrologic processes; hence ""goodness of fit"" can be misleading. Instead, we introduce an approach which evaluates the ability of a model to represent the observed covariance structure of the input (climate) and output (streamflow) without ever calibrating the model. An advantage of this approach is that it is not confounded by model error introduced during the calibration process. We illustrate that once a watershed model is calibrated, the unavoidable model error can cloud our ability to validate (or invalidate) the model. We emphasize that model hypothesis testing (validation) should be performed prior to, and independent of, parameter estimation (calibration), contrary to traditional practice in which watershed models are usually validated after calibrating the model. Our approach is tested using two different watershed models at a number of different watersheds in the United States."
"7005829052;16315817300;22946301100;6701363731;6603422104;6602742025;","Evidence of impact of aviation on cirrus cloud formation",2003,"10.5194/acp-3-1633-2003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-11844281605&doi=10.5194%2facp-3-1633-2003&partnerID=40&md5=121b22cc3a84a4b80d743f3b55e334f9","This work examines changes in cirrus cloud cover (CCC) in possible association with aviation activities at congested air corridors. The analysis is based on the latest version of the International Satellite Cloud Climatology Project D2 data set and covers the period 1984-1998. Over the studied areas, the effect of large-scale modes of natural climate variability such as ENSO, QBO and NAO as well as the possible influence of the tropopause variability, were first removed from the cloud data set in order to calculate long-term changes of observed cirrus cloudiness. The results show increasing trends in (CCC) between 1984 and 1998 over the high air traffic corridors of North America, North Atlantic and Europe. Of these upward trends, only in the summertime over the North Atlantic and only in the wintertime over North America are statistically significant (exceeding +2.0% per decade). Over adjacent locations with low air traffic, the calculated trends are statistically insignificant and in most cases negative both during winter and summer in the regions studied. These negative trends, over low air traffic regions, are consistent with the observed large scale negative trends seen in (CCC) over most of the northern middle latitudes and over the tropics. Moreover, further investigation of vertical velocities over high and low air traffic regions provide evidence that the trends of opposite signs in (CCC) over these regions, do not seem to be caused by different trends in dynamics. It is also shown that the longitudinal distribution of decadal changes in (CCC) along the latitude belt centered at the North Atlantic air corridor, parallels the spatial distribution of fuel consumption from highflying air traffic, providing an independent test of possible impact of aviation on contrail cirrus formation. The correlation between the fuel consumption and the longitudinal variability of (CCC) is significant (+0.7) over the middle latitudes but not over the tropics. This could be explained by the fact that over the tropics the variability of (CCC) is dominated by dynamics while at middle latitudes microphysics explain most of its variability. Results from this study are compared with other studies and for different periods of records and it appears that there exists general agreement as to the evidence of a possible aviation effect on high cloud positive trends over regions with congested air traffic. © 2003 European Geosciences Union."
"7004372110;7006689582;","Amplitude-phase characteristics of the annual cycle of surface air temperature in the Northern Hemisphere",2003,"10.1007/BF03342045","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0142199361&doi=10.1007%2fBF03342045&partnerID=40&md5=a1f958ec99a55f4baf5619531ac29fa1","The amplitude-phase characteristics (APC) of surface air temperature (SAT) annual cycle (AC) in the Northern Hemisphere are analyzed. From meteorological observations for the 20th century and meteorological reanalyses for its second half, it is found that over land negative correlation of SAT AC amplitude with annual mean SAT dominates. Nevertheless, some exceptions exist. The positive correlation between these two variables is found over the two desert regions: in northern Africa and in Central America. Areas of positive correlations are also found for the northern Pacific and for the tropical Indian and Pacific Oceans. Southward of the characteristic annual mean snow-ice boundary (SIB) position, the shape of the SAT AC becomes more sinusoidal under climate warming. In contrast, northward of it, this shape becomes less sinusoidal. The latter is also found for the above-mentioned two desert regions. In the Far East (southward of about 50°N), the SAT AC shifts as a whole: here its spring and autumn phases occur earlier if the annual mean SAT increases. From energy-balance climate considerations, those trends for SAT AC APC in the middle and high latitudes are associated with the influence of the albedo-SAT feedback due to the SIB movement. In the Far East the trends are attributed to the interannual cloudiness variability, and in the desert regions, to the influence of a further desertification and/or scattering aerosol loading into the atmosphere. In the north Pacific, the exhibited trends could only be explained as a result of the influence of the greenhouse-gases loading on atmospheric opacity. The trends for SAT AC APC related to the SIB movement are simulated reasonably well by the climate model of intermediate complexity (IAP RAS CM) in the experiment with greenhouse gases atmospheric loading. In contrast, the tendencies resulting from the cloudiness variability are not reproduced by this model. The model also partly simulates the tendencies related to the desertification processes."
"7006246996;14048818700;57199989445;7004225735;7202601128;","Increasing reflectivity of the Antarctic ocean-atmosphere system: Analysis of Total Ozone Mapping Spectrometer (TOMS) and passive microwave data for 1979-1994",2003,"10.1029/2002jd002702","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742270247&doi=10.1029%2f2002jd002702&partnerID=40&md5=cf408fca15003e350aea7cb1224d175b","Measurements of Lambert equivalent reflectance at 380 nm from the Total Ozone Mapping Spectrometer (TOMS) instrument have shown increases in reflectivity between 1979 and 1994 over much of the Southern Ocean, encompassing 280° in longitude. These trends represent a possible change in the state of the Antarctic ocean-atmosphere system related to recent climate warming. To determine if these reflectivity trends are due to changes in cloud cover or sea ice, or both, the TOMS data were collocated with a contemporaneous passive microwave satellite data set from the scanning multichannel microwave radiometer and the Special Sensor Microwave Imager. The passive microwave data sets specify total sea ice concentration, retrieved by a uniform method for all years using the NASA Team algorithm. To first order the locations of TOMS reflectivity increases coincide with regions where sea ice concentration has increased over the past 2 decades, signifying that the TOMS trends are the result of trends in underlying sea ice and not cloud cover. However, when the TOMS reflectivity measurements are sorted into fixed sea ice concentration bins of 0.1 width, the TOMS data also show increasing reflectivity trends in regions where sea ice extent has been decreasing (Amundsen and Bellingshausen Seas and the Western Antarctic Peninsula). Over open water, TOMS reflectivity trends are less convincing and may be artifacts related to uncertainties in passive microwave sea ice identification. These results suggest that a significant component of the Southern Ocean TOMS reflectivity trends may be a gradual increase in the albedo of the underlying sea ice. This could be caused by a gradual lengthening of the sea ice season, with a concomitant increase in the persistence of dry snow on the sea ice cover."
"7003465848;55965624000;55393706100;6603247427;21735084500;","A new interactive chemistry-climate model: 2. Sensitivity of the middle atmosphere to ozone depletion and increase in greenhouse gases and implications for recent stratospheric cooling",2003,"10.1029/2002jd002977","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346069193&doi=10.1029%2f2002jd002977&partnerID=40&md5=14c61de3106086a174b080589bf34db2","The sensitivity of the middle atmosphere circulation to ozone depletion and increase in greenhouse gases is assessed by performing multiyear simulations with a chemistry-climate model. Three simulations with fixed boundary conditions have been carried out: one simulation for the near-past (1960) and two simulations for the near-present (1990 and 2000) conditions, including changes in greenhouse gases, in total organic chlorine, and in average sea surface temperatures. Changes in ozone are simulated interactively by the coupled model. It is found that in the stratosphere, ozone decreases, and that in the Antarctic, the ozone hole develops in both the 1990 and the 2000 simulations but not in the 1960 simulation, as observed. The simulated temperature decreases in the stratosphere and mesosphere from the near past to the present, with the largest changes at the stratopause and at the South Pole in the lower stratosphere, in agreement with current knowledge of temperature trends. In the Arctic lower stratosphere, a cooling in March with respect to the 1960 simulation is found only for the 2000 simulation. Wave activity emerging from the troposphere is found to be comparable in the winters of the 1960 and 2000 simulations, suggesting that ozone depletion and greenhouse gases increase contribute to the 2000-1960 March cooling in the Arctic lower stratosphere. These results therefore provide support to the interpretation that the extreme low temperatures observed in March in the last decade can arise from radiative and chemical processes, although other factors cannot be ruled out. The comparison of the 1960 and 2000 simulations shows an increase in downwelling in the mesosphere at the time of cooling in the lower stratosphere (in March in the Arctic; in October in the Antarctic). The mesospheric increase in downwelling can be explained as the response of the gravity waves to the stronger winds associated with the cooling in the lower stratosphere. Planetary waves appear to contribute to the downward shift of the increased downwelling, with a delay of about a month. The increase in dynamical heating associated with the increased downwelling may limit the cooling and the strengthening of the lower stratospheric polar vortex from above, facilitating ozone recovery and providing a negative dynamical feedback. In both the Arctic and Antarctic the cooling from ozone depletion is found to affect the area covered with polar stratospheric clouds in spring, which is substantially increased from the 1960 to the 2000 simulations. In turn, increased amounts of polar stratospheric clouds can facilitate further ozone depletion in the 2000 simulation."
"55502994400;6701418794;6506126751;7004459129;","A fast H2O total column density product from GOME - Validation with in-situ aircraft measurements",2003,"10.5194/acp-3-651-2003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642570716&doi=10.5194%2facp-3-651-2003&partnerID=40&md5=ed4b2649e716a100ae946466b55ccca8","Atmospheric water vapour is the most important greenhouse gas which is responsible for about 2/3 of the natural greenhouse effect, therefore changes in atmospheric water vapour in a changing climate (the water vapour feedback) is subject to intense debate. H2O is also involved in many important reaction cycles of atmospheric chemistry, e.g. in the production of the OH radical. Thus, long time series of global H2O data are highly required. Since 1995 the Global Ozone Monitoring Experiment (GOME) continuously observes atmospheric trace gases. In particular it has been demonstrated that GOME as a nadir looking UV/visinstrument is sensitive to many tropospheric trace gases. Here we present a new, fast H2O algorithm for the retrieval of vertical column densities from GOME measurements. In contrast to existing H2O retrieval algorithms it does not depend on additional information like e.g. the climatic zone, aerosol content or ground albedo. It includes an internal cloud-, aerosol-, and albedo correction which is based on simultaneous observations of the oxygen dimer O4. From sensitivity studies using atmospheric radiative modelling we conclude that our H2O retrieval overestimates the true atmospheric H2O vertical column density (VCD) by about 4% for clear sky observations in the tropics and sub-tropics, while it can lead to an underestimation of up to -18% in polar regions. For measurements over (partly) cloud covered ground pixels, however, the true atmospheric H 2O VCD might be in general systematically underestimated. We compared the GOME H2O VCDs to ECMWF model data over one whole GOME orbit (extending from the Arctic to the Antarctic) including also totally cloud covered measurements. The correlation of the GOME observations and the model data yield the following results: a slope of 0.96 (r2 = 0.86) and an average bias of 5%. Even for measurements with large cloud fractions between 50% and 100% an average underestimation of only -18% was found. This high accuracy of our GOME H2O data is also confirmed by the excellent agreement with in-situ aircraft measurements during the MINOS campaign in Greece in summer 2001 (slope of 0.97 (r2 = 0.86), and an average bias of only 0.2%). Our H2O algorithm can be directly adapted to the nadir observations of SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY) which was launched on ENVISAT in March 2002. Near real time H 2O column data from GOME and SCIAMACHY might be of great value for meteorological weather forecast. © 2003 European Geophysical Society."
"22944066200;7004423053;15028140400;7006151875;7202641466;6603113016;9036745800;","Constraining temperature variations over the last millennium by comparing simulated and observed atmospheric CO2",2003,"10.1007/s00382-002-0270-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037271674&doi=10.1007%2fs00382-002-0270-8&partnerID=40&md5=5cbfdc936d00cec3f5277d1341006433","The response of atmospheric CO2 and climate to the reconstructed variability in solar irradiance and radiative forcing by volcanoes over the last millennium is examined by applying a coupled physical-biogeochemical climate model that includes the Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM) and a simplified analogue of a coupled atmosphere-ocean general circulation model. The modeled variations of atmospheric CO2 and Northern Hemisphere (NH) mean surface temperature are compatible with reconstructions from different Antarctic ice cores and temperature proxy data. Simulations where the magnitude of solar irradiance changes is increased yield a mismatch between model results and CO2 data, providing evidence for modest changes in solar irradiance and global mean temperatures over the past millennium and arguing against a significant amplification of the response of global or hemispheric annual mean temperature to solar forcing. Linear regression (r = 0.97) between modeled changes in atmospheric CO2 and NH mean surface temperature yields a CO2 increase of about 12 ppm for a temperature increase of 1 °C and associated precipitation and cloud cover changes. Then, the CO2 data range of 12 ppm implies that multi-decadal NH temperature changes between 1100 and 1700 AD had to be within 1 °C. Modeled preindustrial variations in atmospheric δ13C are small compared to the uncertainties in ice core δ13C data. Simulations with natural forcings only suggest that atmospheric CO2 would have remained around the preindustrial concentration of 280 ppm without anthropogenic emissions. Sensitivity experiments show that atmospheric CO2 closely follows decadal-mean temperature changes when changes in ocean circulation and ocean-sediment interactions are not important. The response in terrestrial carbon storage to factorial changes in temperature, the seasonality of temperature, precipitation, and atmospheric CO2 has been determined."
"8558549200;8558549300;6504179147;6506362668;7004289682;","Validation of NWP mesoscale models with Swiss GPS network AGNES",2003,"10.1175/1520-0450(2003)042<0141:VONMMW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141650503&doi=10.1175%2f1520-0450%282003%29042%3c0141%3aVONMMW%3e2.0.CO%3b2&partnerID=40&md5=3bb88e68cd628eaa2bb5359b61f66550","The importance of water vapor for the hydrological cycle of the earth and the atmosphere is well known but difficult to study and sample. In this respect, the vertically integrated water vapor (IWV) derived from global positioning system (GPS) delay is a potential source of valuable weather information. Because of the relatively dense station distribution, both the temporal and horizontal variability of water vapor are well captured by the GPS. This makes GPS data well suited for numerical weather prediction (NWP) models. In this paper the automated GPS network of Switzerland (AGNES) is used for calculation of IWV and for comparison with radiosonde data and two NWP mesoscale models from MeteoSwiss named Local Model (LM) and Swiss Model (SM). Reasonably good agreement between GPS and radiosonde data is reported. It has been identified that in some particular weather situations with low stratus clouds and temperature inversion, the radiosonde significantly overestimates the water vapor amount. The LM and SM verification with GPS data indicates good agreement during the winter period (November 2000-March 2001) and high variability and bias in the summer period (August 2000). The monthly mean IWV values from GPS and LM show a systematic deviation over the Swiss plateau region and a very good agreement for the high-altitude alpine station, Andermatt. The capability of GPS in monitoring the atmospheric phenomena has been demonstrated. Unrealistic IWV at Jungfraujoch (∼3600 m MSL) caused by GPS antenna problems is reported."
"7004762055;","The spiral structure of the Milky Way, cosmic rays, and ice age epochs on Earth",2003,"10.1016/S1384-1076(02)00193-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867958838&doi=10.1016%2fS1384-1076%2802%2900193-8&partnerID=40&md5=97417bc9a094b1e990e898ec32a47e15","The short term variability of the galactic cosmic ray flux (CRF) reaching Earth has been previously associated with variations in the global low altitude cloud cover. This CRF variability arises from changes in the solar wind strength. However, cosmic ray variability also arises intrinsically from variable activity of and motion through the Milky Way. Thus, if indeed the CRF climate connection is real, the increased CRF witnessed while crossing the spiral arms could be responsible for a larger global cloud cover and a reduced temperature, thereby facilitating the occurrences of ice ages. This picture has been recently shown to be supported by various data [PhRvL 89 (2002) 051102]. In particular, the variable CRF recorded in Iron meteorites appears to vary synchronously with the appearance ice ages. Here, we expand upon the original treatment with a more thorough analysis and more supporting evidence. In particular, we discuss the cosmic ray diffusion model which considers the motion of the galactic spiral arms. We also elaborate on the structure and dynamics of the Milky Way's spiral arms. In particular, we bring forth new argumentation using HI observations which imply that the galactic spiral arm pattern speed appears to be that which fits the glaciation period and the cosmic-ray flux record extracted from Iron meteorites. In addition, we show that apparent peaks in the star formation rate history, as deduced by several authors, coincides with particularly icy epochs, while the long period of 1 to 2 Gyr before present, during which no glaciations are known to have occurred, coincides with a significant paucity in the past star formation rate. © 2002 Elsevier Science B.V."
"7006748820;","Analysis of an anomalously severe thunderstorm system over Northern Ireland",2003,"10.1016/S0169-8095(03)00044-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141738360&doi=10.1016%2fS0169-8095%2803%2900044-9&partnerID=40&md5=377e7df826bbe46f24e7f9132cebc92f","In Northern Ireland, as elsewhere in Europe, attempts to reduce the societal impacts of severe convective storms are constrained by underestimations in frequency and intensity of extreme events within the present-day climate regime. Such underestimations also present difficulties in estimating probabilities of extreme storm frequency and intensity in relation to future climate change scenarios. Detailed analyses of past extreme events enhance the robustness of hydrometeorological and climatological models, and improve human perception of the true nature of present climate. In Northern Ireland, extensive thunderstorm development is infrequent due to relatively low relief and limited severe convectional activity in summer. On 25-26 July 1985 extensive thunderstorm activity occurred accompanied by hailstones 3 cm in diameter, some of the largest on record to fall over the Province. The event predates operation of the Northern Ireland component of the UK rainfall radar network. Nevertheless, utilizing quality- controlled autographic rain gauge records and radiosonde data, the synoptic situation was examined and the mesoscale precipitation signatures determined throughout the duration of thunderstorm activity. Within the cyclonic circulation covering Northern Ireland for much of the day, potential instability existed at three levels and on release the buoyant upward motion resulted in clouds of more than 11 km in depth. While upland areas recorded 30 to 50 mm, the greatest precipitation totals of up to 85 mm were received in lowland areas around Lough Neagh. Several lowland sites recorded rainfall totals and intensities with frequencies of about 1 in 100 years. Significant thunderstorm activity occurred over a period of 11 h and resulted in serious flooding. Observed mesoscale precipitation patterns displayed limited evidence of orographic enhancement within the moist southeast to south airflow. At best, orography assisted in terms of initial uplift, but thereafter precipitation distribution was reliant upon thunderstorm cell structure and movement with input from local site and exposure influences. A factor possibly reducing the potential for marked orographic enhancement was the absence of strong winds at low levels. Mesoscale precipitation patterns suggested enhancement locally around the west and north shores of Lough Neagh. Energy exchanges between the Lough surface and the overlying atmosphere may have had repercussions upon water vapour content and buoyancy within the cyclonic south to southeasterly airflow, leading to this precipitation enhancement. Occurrence in the Mournes of hailstones 3 cm in diameter was indicative of the strength and endurance of the updraught component within individually propagating cells. The remarkable amounts and high intensities of rainfall, accompanied by large hailstone development, emphasized the importance of the synoptic event within the climatological history of Northern Ireland. With an absence of notable orographic enhancement of precipitation, the event also highlighted the occurrence of deviations from the mean precipitation patterns normally expected within cyclonic circulations. © 2003 Elsevier B.V. All rights reserved."
"8720083500;57212397635;16205504100;56065666500;","Seasonal variations of anthropogenic sulfate aerosol and direct radiative forcing over China",2003,"10.1007/s00703-002-0581-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346361848&doi=10.1007%2fs00703-002-0581-7&partnerID=40&md5=0a5cf11e62fcee96dba21613e71ec70e","Regional climate model (RegCM2) and sulfur transport model (NJUADMS) were combined to simulate the distribution of anthropogenic sulfate aerosol burden over China, where a ""look up table"" method was applied to illustrate sulfate formation from SO2-oxidation. Direct radiative forcing of sulfate aerosol was further estimated using the scheme suggested by Charlson et al (1991 . Investigations show that the annual average total sulfate column over mainland China is 2.01 mg/m2 with high value in East and Central areas (more than 7 mg/m2). The annual average direct radiative forcing of China is about -0.85 W/m2. The forcing can reach - 7 W/m2 in Central and East China during the winter season. Total sulfate column shows significant seasonal variations with winter maximum-summer minimum in the Southern part of China and spring maximum-autumn minimum in the northern part of China. Strong seasonal cycles of direct radiative forcing are also found due to the influence of total sulfate column, cloud, relative humidity and the reflectivity of underlying surface."
"7402005920;57207511394;","Spatial variability in UV radiation during the growing season across the continental USA",2003,"10.1007/s00704-002-0719-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037994209&doi=10.1007%2fs00704-002-0719-z&partnerID=40&md5=5d3a1fa3f6a99269697825672bb18d8e","A major limitation in predicting the ultraviolet-B irradiance on humans, plant leaves and flowers and aquatic organisms is the difficulty in estimating exposure. This study analyzes the spatial variability in the daily exposure of narrow band 300 nm and 368 nm and broadband 290-315 nm (UVB) solar radiation between twelve paired locations in the United States Department of Agriculture (USDA) UVB Climate Network over two summer growing seasons (May through August of 2000 and 2001). The spatial correlation of the UVB, 300 nm and 368 nm daily exposures between locations was approximately 0.7 to 0.8 for spacing distances of 100 km. The 300 nm daily exposure was typically more highly correlated between locations than the 368 nm daily exposure. Both the diffuse and direct beam components to the 300 nm daily exposure were similarly correlated with distance between locations. The 368 nm diffuse component of the daily exposures was less correlated with distance than the direct beam component, limiting the ability to interpolate daily exposures from measurement locations. In general the variability in daily exposures of UVB in the USDA UVB Climate Network is too large to interpolate daily exposures of solar radiation, with estimated 300 nm, 368 nm and broadband UVB errors at one-half the mean station spacing of the USDA Network of 22%, 21% and 16% respectively. More accurate interpolations of UVB exposure from this network will require either the incorporation of cloud cover variability from satellite imagery for daily exposure or the use of longer periods of accumulated exposure."
"7006130951;7404105326;7404142321;","Modelling the atmospheric response to doubled CO2 and depleted stratospheric ozone using a stratosphere-resolving coupled GCM",2003,"10.1256/qj.02.102","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037261301&doi=10.1256%2fqj.02.102&partnerID=40&md5=3d4d5f5340fe34d9f3069cfc9aea4712","We investigate the atmospheric response to doubled CO2 and stratospheric ozone depletion in three versions of a general-circulation model with differing vertical resolution and upper-boundary heights. We find that an approximate doubling of the vertical resolution below 10 hPa reduces the temperature response to a doubling of CO2 from 3.4 K to 2.5 K. Much of this difference is associated with changes in the cloud response. All model versions show an increase in the Arctic Oscillation index in response to a doubling of CO2, but the increase is no larger in the model with an upper boundary at 0.01 hPa than in the standard model with a top level at 5 hPa. All models also show general stratospheric cooling in response to doubling CO2. However, unlike some other authors, we find no cooling in the Arctic winter vortex below around 10 hPa in the stratosphere-resolving model, and a weakening of the zonal winds throughout this region. This effect is due to enhanced upward propagation of planetary waves from the troposphere, and is an effect found only in the northern hemisphere, probably because of its larger zonal asymmetries. All models show a small but significant surface cooling in response to a reconstruction of 1998 stratospheric ozone depletion, and an increase in the Antarctic Oscillation index in the southern summer. The cooling extends through most of the atmosphere, and reaches a maximum in the region of the Antarctic ozone hole in November and December."
"55474342800;7005634455;6602926744;","Evaluation of polar MM5 simulations of Antarctic atmospheric circulation",2003,"10.1175/1520-0493(2003)131<0384:EOPMSO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038300273&doi=10.1175%2f1520-0493%282003%29131%3c0384%3aEOPMSO%3e2.0.CO%3b2&partnerID=40&md5=589d3f33bb37eba1303c05cf9471b360","Evaluation of a complete annual cycle of nonhydrostatic mesoscale model simulations of the Antarctic atmospheric circulation is presented. The year-long time series are compiled from a series of overlapping short-duration (72 h) simulations of the atmospheric state with the first 24 h being discarded for spinup reasons, and the 24-72-h periods used for model evaluation. The simulations are generated with the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5), which is modified for polar applications, and is refferred to as Polar MM5. With a horizontal resolution of 60 km, the Polar MM5 has been run for the period of January 1993-December 1993, creating short-term simulations from initial and boundary conditions provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) Tropical Ocean Global Atmosphere (TOGA) operational analyses. The model output is compared with observations from automatic weather stations, upper-air data, and global atmospheric analyses as well as climatological maps over timescales from diurnal to annual. In comparison with the observations, the evaluation shows that simulations with the Polar MM5 capture both the large- and regional-scale circulation features with generally small bias in the modeled variables. For example, the differences between the observations and simulations at the 500-hPa level are usually less than 2°C for temperature and dewpoint temperature, and 20 m for geopotential height. On the annual timescale the largest errors in the model simulations are the deficient total cloud cover and precipitation, and the colder near-surface temperature over the interior of the Antarctic plateau. The deficiencies in the cloud prediction and precipitation simulation follow from low-level dry biases found in the Polar MM5 simulations, and the cold bias is related to the low predicted downward longwave radiation under clear skies in the radiation parameterization scheme. The deficient predicted precipitation also reflects the limited ability of Polar MM5 to represent clear sky precipitation. On the seasonal timescale a persistent positive pressure bias is found in the model simulations, caused by the interaction between the gravity waves and the model upper boundary condition. The observed synoptic variability of the pressure, temperature, wind speed, wind direction, and water vapor mixing ratio, as well as the diurnal cycles of temperature, wind speed, and mixing ratio, are reproduced by the Polar MM5 with reasonable accuracy."
"7203001286;","A parameterization of sea-salt aerosol source function for sub- and super-micron particles",2003,"10.1029/2003gb002079","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642365865&doi=10.1029%2f2003gb002079&partnerID=40&md5=c011aadb4db6820c3595aec9824b694c","A parameterization of a sea-salt source function for both sub- and super-micron particles was developed based on the semi-empirical formulation of Monahan et al. [1986]. This new parameterization extends the range of Monahan's equation to below 0.2 μm in diameter where it has been found to overestimate submicron sea-salt aerosols, especially the sea-salt number concentrations. The new parameterization was used in a one-dimensional (1-D) column model to predict the number size distributions and compared with reasonable agreement to the observed distributions at various wind speeds reported by O'Dowd et at. [1997]. A global 3-D sea-salt simulation with this parameterization was also made and a much better dependence of sea-salt on surface wind speed was predicted than other schemes compared to observations. For an indirect impact assessment of sea-salt aerosols on climate where submicron particles may have a dominant contribution to aerosol-cloud interactions, this scheme provides the most realistic number flux of sea-salt particles between ocean and atmosphere. Copyright 2003 by the American Geophysical Union."
"6603751015;57213612187;7004215700;6507191414;7006082326;7801639573;35508431200;","Mesoscale aspects of the Urban Heat Island around New York City",2003,"10.1007/s00704-002-0724-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038267525&doi=10.1007%2fs00704-002-0724-2&partnerID=40&md5=7ce52a5b36d95cf43c1a5ff1e20062c8","A mesoscale analysis of the Urban Heat Island (UHI) of New York City (NYC) is performed using a mesoscale network of weather stations. In all seasons the UHI switches on rapidly in late afternoon and shuts down even more rapidly shortly after dawn. It averages about 4°C in summer and autumn and 3°C in winter and spring. It is largest on nights with clear skies, low relative humidity through much of the troposphere, and weak northwest winds, when it may exceed 8°C. The synoptic meteorological situation associated with the largest UHI occurs roughly two to three nights after cold front passages. During spring and summer, sea breezes commonly reduce and delay the UHI and displace it about 10 km to the west. Backdoor cold fronts, which occur most frequently in spring and early summer, reduce or even reverse the UHI, as cold air from the water to the northeast keeps NYC colder than the western suburbs. Cases documenting the sensitivity and rapidity of changes of the UHI to changes in parameters such as cloud cover, ceiling, and wind speed and direction are presented."
"6701354931;6508388076;57212792245;25653594600;7004660454;7004621645;","The use of earth observation techniques to improve catchment-scale pollution predictions",2003,"10.1016/j.pce.2003.09.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242698160&doi=10.1016%2fj.pce.2003.09.013&partnerID=40&md5=7df96a55f5c6f5fdd79ae18c61f71a4b","Remote sensing can potentially provide information useful in improving pollution transport modelling in agricultural catchments. Realisation of this potential will depend on the availability of the raw data, development of information extraction techniques, and the impact of the assimilation of the derived information into models. High spatial resolution hyperspectral imagery of a farm near Hereford, UK is analysed. A technique is described to automatically identify the soil and vegetation endmembers within a field, enabling vegetation fractional cover estimation. The aerially-acquired laser altimetry is used to produce digital elevation models of the site. At the subfield scale the hypothesis that higher resolution topography will make a substantial difference to contaminant transport is tested using the AGricultural Non-Point Source (AGNPS) model. Slope aspect and direction information are extracted from the topography at different resolutions to study the effects on soil erosion, deposition, runoff and nutrient losses. Field-scale models are often used to model drainage water, nitrate and runoff/sediment loss, but the demanding input data requirements make scaling up to catchment level difficult. By determining the input range of spatial variables gathered from EO data, and comparing the response of models to the range of variation measured, the critical model inputs can be identified. Response surfaces to variation in these inputs constrain uncertainty in model predictions and are presented. Although optical earth observation analysis can provide fractional vegetation cover, cloud cover and semi-random weather patterns can hinder data acquisition in Northern Europe. A Spring and Autumn cloud cover analysis is carried out over seven UK sites close to agricultural districts, using historic satellite image metadata, climate modelling and historic ground weather observations. Results are assessed in terms of probability of acquisition probability and implications for future earth observation missions. © 2003 Elsevier Ltd. All rights reserved."
"7003496215;6701825432;","Thermal performance analysis of highly reflective coating on residences in hot and arid climates",2003,"10.1061/(ASCE)0733-9402(2003)129:2(56)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14044261227&doi=10.1061%2f%28ASCE%290733-9402%282003%29129%3a2%2856%29&partnerID=40&md5=5ca3169bd2f1cb25b54f6f4bf9361d5e","A 1-D transient model (RESHEAT), developed by the writers, was used to study the thermal performance of a highly reflective paint applied sequentially to the outer walls and roof of a simulated residence in a hot and arid region of the southwestern United States. The model uses climatological inputs from a file that includes hourly data on ambient temperatures, insolation, cloud cover, and so on, at the particular location. The model focuses particularly on the potential cooling load reduction due to the reduced heat pickup from the inside attic surfaces to the outer surfaces of the supply duct. This simulation showed that a reduction of 33.6% (cooling load) on the average is achieved over the base case where no reflective paint is used when the outer surface of the roof and walls are painted. Alternatively, only a 11% reduction would be achieved if the reflective paint is applied only to the roof. Savings of $42 per month are conservatively estimated from calculations made when applying this technology to a typical residence (roof and walls) equipped with a 4 ton refrigeration unit in the Southwest."
"6506730133;7004416203;","Impact of ozone mini-holes on the heterogeneous destruction of stratospheric ozone",2003,"10.1016/S0045-6535(02)00599-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037258861&doi=10.1016%2fS0045-6535%2802%2900599-4&partnerID=40&md5=c4a3a57d54547b44e18c6d1b6c666aa0","A comprehensive study of ozone mini-holes over the mid-latitudes of both hemispheres is presented, based on model simulations with the coupled climate-chemistry model ECHAM4.L39(DLR)/CHEM representing atmospheric conditions in 1960, 1980, 1990 and 2015. Ozone mini-holes are synoptic-scale regions of strongly reduced total ozone, directly associated with tropospheric weather systems. Mini-holes are supposed to have chemical and dynamical impacts on ozone levels. Since ozone levels over northern mid-latitudes show a negative trend of ≈-4%/decade and since it exists a negative correlation between total column ozone and erythemally active solar UV-radiation reaching the surface it is important to understand and assess the processes leading to the observed ozone decline. The simulated mini-hole events are validated with a mini-hole climatology based on daily ozone measurements with the TOMS (total ozone mapping spectrometer) instrument on the satellite Nimbus-7 between 1979 and 1993. Furthermore, possible trends in the event frequency and intensity over the simulation period are assessed. In the northern hemisphere the number of mini-hole events in early winter decreases between 1960 and 1990 and increases towards 2015. In the southern hemisphere a positive trend in mini-hole event frequency is detected between 1960 and 2015 in spring associated with the increasing Antarctic Ozone Hole. Finally, the impact of mini-holes on the stratospheric heterogeneous ozone chemistry is investigated. For this purpose, a computer-based detection routine for mini-holes was developed for the use in ECHAM4.L39(DLR)/CHEM. This method prevents polar stratospheric cloud formation and therefore heterogeneous ozone depletion inside mini-holes. Heterogeneous processes inside mini-holes amount to one third of heterogeneous ozone destruction in general over northern mid- and high-latitudes during winter (January-April) in the simulation. © 2002 Elsevier Science Ltd. All rights reserved."
"7004696761;6701744876;57191595169;","The status of the Indo-Pacific Warm Pool and adjacent land at the Last Glacial Maximum",2003,"10.1016/S0921-8181(02)00089-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037211837&doi=10.1016%2fS0921-8181%2802%2900089-9&partnerID=40&md5=05c1f158390f4315c905f1cff4ce72a2","Since the Climate: Long Range Investigation, Mapping and Prediction (CLIMAP) reconstructions for the Earth at the Last Glacial Maximum (LGM), there have been conflicting views on the extent of cooling of the oceans of tropical Australasia - here, referred to as the Indo-Pacific Warm Pool - in contrast with those temperatures registered on land. Based on sea-surface temperature (=SST) reconstructions for the Indo-Pacific Warm Pool, and on vegetation reconstruction for SE Asia as well as by considering the increase of land mass area engendered during low sea levels, we identify for the LGM a significant drop in precipitation in the Warm Pool region that would explain an increase in salinity while SST decreased by about 2°C at the most. The latter would have caused a substantial decrease of large-scale atmospheric convection over the Indo-Pacific Warm Pool and suppressed deep atmospheric convection that would help maintain somewhat elevated SSTs. The drier atmosphere and diminished level of cloud cover would also have reduced nocturnal temperatures at elevation in the region and produced a steeper mean atmospheric lapse rate, forcing the tree line to drop and glaciers to be maintained down to much lower altitudes than today. © 2002 Elsevier Science B.V. All rights reserved."
"7402093416;7004214645;6602105959;55393706100;55919935700;7003465848;24470422300;7202400272;57062286700;7003800456;7003683808;6506061094;7103294731;","Uncertainties and assessments of chemistry-climate models of the stratosphere",2003,"10.5194/acp-3-1-2003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038374423&doi=10.5194%2facp-3-1-2003&partnerID=40&md5=7a74fdd18a2911b81824d66504d88ff7","In recent years a number of chemistry-climate models have been developed with an emphasis on the stratosphere. Such models cover a wide range of time scales of integration and vary considerably in complexity. The results of specific diagnostics are here analysed to examine the differences amongst individual models and observations, to assess the consistency of model predictions, with a particular focus on polar ozone. For example, many models indicate a significant cold bias in high latitudes, the ""cold pole problem"", particularly in the southern hemisphere during winter and spring. This is related to wave propagation from the troposphere which can be improved by improving model horizontal resolution and with the use of non-orographic gravity wave drag. As a result of the widely differing modelled polar temperatures, different amounts of polar stratospheric clouds are simulated which in turn result in varying ozone values in the models. The results are also compared to determine the possible future behaviour of ozone, with an emphasis on the polar regions and mid-latitudes. All models predict eventual ozone recovery, but give a range of results concerning its timing and extent. Differences in the simulation of gravity waves and planetary waves as well as model resolution are likely major sources of uncertainty for this issue. In the Antarctic, the ozone hole has probably reached almost its deepest although the vertical and horizontal extent of depletion may increase slightly further over the next few years. According to the model results, Antarctic ozone recovery could begin any year within the range 2001 to 2008. The limited number of models which have been integrated sufficiently far indicate that full recovery of ozone to 1980 levels may not occur in the Antarctic until about the year 2050. For the Arctic, most models indicate that small ozone losses may continue for a few more years and that recovery could begin any year within the range 2004 to 2019. The start of ozone recovery in the Arctic is therefore expected to appear later than in the Antarctic. Further, interannual variability will tend to mask the signal for longer than in the Antarctic, delaying still further the date at which ozone recovery may be said to have started. Because of this inherent variability of the system, the decadal evolution of Arctic ozone will not necessarily be a direct response to external forcing. © European Geosciences Union 2003."
"7007148434;7201610459;55414404600;57203200427;8783945600;6602765265;7403401100;7004864963;35461763400;","Physical properties and concentration of aerosol particles over the Amazon tropical forest during background and biomass burning conditions",2003,"10.5194/acp-3-951-2003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347790219&doi=10.5194%2facp-3-951-2003&partnerID=40&md5=ae26263b64930ce79e685061d8485c53","We investigated the size distribution, scattering and absorption properties of Amazonian aerosols and the optical thickness of the aerosol layer under the pristine background conditions typical of the wet season, as well as during the biomass-burning-influenced dry season. The measurements were made during two campaigns in 1999 as part of the European contribution to the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA-EUSTACH). In moving from the wet to the dry season, median particle numbers were observed to increase from values comparable to those of the remote marine boundary layer (∼400 cm -3) to values more commonly associated with urban smog (∼4000 cm-3), due to a massive injection of submicron smoke particles. Aerosol optical depths at 500 nm increased from 0.05 to 0.8 on average, reaching a value of 2 during the dry season. Scattering and absorption coefficients, measured at 550 nm, showed a concomitant increase from average values of 6.8 and 0.4Mm-1 to values of 91 and 10Mm-1, respectively, corresponding to an estimated decrease in single-scattering albedo from ca. 0.97 to 0.91. The roughly tenfold increase in many of the measured parameters attests to the dramatic effect that extensive seasonal biomass burning (deforestation, pasture cleaning) is having on the composition and properties of aerosols over Amazonia. The potential exists for these changes to impact on regional and global climate through changes to the extinction of solar radiation as well as the alteration of cloud properties. © 2003 European Geosciences Union."
"7004041202;7005035462;6603166240;","Validation of microwave sea surface temperature measurements for climate purposes",2003,"10.1175/1520-0442(2003)016<0073:VOMSST>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0041462874&doi=10.1175%2f1520-0442%282003%29016%3c0073%3aVOMSST%3e2.0.CO%3b2&partnerID=40&md5=a78b04638878bf9bce230e601f4b587d","A comparison is provided between recent SST observations obtained from the TRMM Microwave Imager (TMI) with the commonly used Reynolds and Smith SST analysis and in situ data that highlights the significant value added by the microwave SST observations above what can be obtained from infrared technology. The largest benefit of the microwave technology clearly comes from the unprecedented near all-weather sampling of ocean phenomena that yields measurements of ocean SST without the heavy smoothing in space and time that is traditionally being applied to close data gaps & resulting from clouds. This comparison of the TMI fields with the Reynolds and Smith analysis results in a mean offset of 0.l8°C and a standard deviation (STD) difference of 0.54°C over the latitude range ±36°. Regionally STD differences are found between both SST fields that reach 1°C or more, a number that is significantly larger than the error specification of either dataset alone. STD differences are obtained between Reynolds and Smith and in situ data of 0.55°C as compared to only 0.45°C from the TMI fields. Moreover, those uncertainties are time dependent and spatially varying, revealing a clear seasonal cycle with amplitudes varying by 0.35°C in the Reynolds and Smith SST fields around 25° latitude on the annual cycle in both hemispheres. Both TMI and the Reynolds and Smith analyses show temporal trends relative to in situ observations that differ in sign and amplitude."
"6603400519;8045690700;57213152523;","Mineral Dust Entrainment and Deposition (DEAD) model: Description and 1990s dust climatology",2003,"10.1029/2002jd002775","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347814598&doi=10.1029%2f2002jd002775&partnerID=40&md5=924a69b58664f1e9ca7a02c77e080306","We describe a model for predicting the size-resolved distribution of atmospheric dust for climate and chemistry-related studies. The dust distribution from 1990 to 1999 is simulated with our mineral aerosol entrainment and deposition module embedded in a chemical transport model. Mobilization processes include entrainment thresholds for saltation, moisture inhibition, drag partitioning, and saltation feedback. For mobilization we assume that soil texture is globally uniform and is replete with saltators. Soil erodibility is prescribed by a new physically based geomorphic index that is proportional to the runoff area upstream of each source region. Dry deposition processes include sedimentation and turbulent mix-out. Nucleation scavenging and size-resolved washout in both stratiform and convective cloud types are represented. Simulations of the 1990s broadly agree with station observations and satellite-inferred dust distributions. Without invoking anthropogenic mechanisms the model captures the seasonal migration of the transatlantic African dust plume, and it captures the spring maximum in Asian dust outflow and concentration over the Pacific. We estimate the 1990s global annual mean and variability of D &lt; 10 μm dust to be the following: emissions, 1490 ± 160 Tg yr-1; burden, 17 ± 2 Tg; and optical depth at 0.63 μm, 0.030 ± 0.004. This emission, burden, and optical depth are significantly lower than some recent estimates. The model underestimates transport and deposition of East Asian and Australian dust to some regions of the Pacific Ocean. An underestimate of long-range transport of particles larger than 3 μm contributes to this bias. Our experiments support the hypothesis that dust emission ""hot spots"" exist in regions where alluvial sediments have accumulated and may be disturbed."
"6506322102;6603898368;6603680545;","Evolution of the NOy-N2O correlation in the Antarctic stratosphere during 1993 and 1995",2003,"10.1029/2002jd002871","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742322562&doi=10.1029%2f2002jd002871&partnerID=40&md5=ad44fea9aefb1d0527ad7a5f5642c7d1","The sources and sinks of stratospheric reactive nitrogen (NOy) in the Antarctic are known only qualitatively, because of the very few measurements of NOy available in this region. As a result, the effects of stratospheric NOy short- and long-term changes on the stratospheric concentration of ozone, water vapor, and other climate-forcing agents are still uncertain. To better understand the annual cycle of polar stratospheric NOy, we estimate its concentration in the Antarctic stratosphere during part of 1993 and throughout 1995. These estimates are obtained at seven potential temperature levels, extending from ∼18 to 30 km of altitude, and are associated with ground-based measurements of another tracer, N2O, in order to produce NOy-N2O correlation curves that can provide insights on nitrogen sources and sinks. To estimate NOy mixing ratios, we use ground-based and satellite measurements of major NOy constituents, connected by using air parcel trajectories and supplemented by model calculations of minor contributing species for which no suitable measurements exist. All the available NOy-N2O correlation points are averaged over three representative seasonal time periods in 1993 and six periods in 1995. Results show very similar correlation curves during the late summer and the fall of 1995, and again during the early spring 1993 compared with the early and late winter of 1995, although there are large seasonal changes due to transport and to condensation of NOy onto polar stratospheric clouds. We calculate a loss from the latter process of ΔN = (6.3 ± 2.6) × 107 kg of stratospheric nitrogen in the southern polar vortex during 1995. We also compare our correlation curves with those obtained in the Antarctic stratosphere during the Atmospheric Trace Molecule Spectroscopy mission ATMOS/ATLAS-3 in November 1994, finding important similarities but also critical differences that suggest that extra-vortex air is generally not an adequate representation of prewinter inner vortex conditions. Calculations of NOy winter removal in the Antarctic stratosphere which have used extra-vortex measurements as a surrogate for prewinter conditions may thus have underestimated true NOy removal. Our prewinter NOy estimates in the vortex core match values obtained by atmospheric models that incorporate upper atmospheric sources of NOy, supporting the belief that such sources have a significant effect on polar stratospheric NOy."
"7005485117;6602615387;","A new approach to the cumulus parameterization issue",2003,"10.1034/j.1600-0870.2003.00021.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042942935&doi=10.1034%2fj.1600-0870.2003.00021.x&partnerID=40&md5=7d63cfbc7b2e12a6c680cad1a0a03cfd","Can the superensemble methodology provide improved precipitation forecasts by combining existing physical parameterizations? We recently addressed this question in the context of Numerical Weather Prediction (NWP). We feel, however, that the information provided here may be useful for seasonal climate modeling as well. In the NWP context, we have developed multi-model forecasts from six versions of the Florida State University global spectral model (at a horizontal resolution of 170 waves, triangular truncation). These different versions deployed six different cumulus parameterization schemes; these models were identical in all other aspects, including the initial states. Making the assumption that differences in short-range (one day) forecasts of precipitation arise largely from differences in the cumulus parameterization, a superensemble methodology, following a recent study, was deployed to assign geographically distributed weights to convective heating for the different cumulus parameterization schemes. This was done after completion of some 85 experiments for each model for the training phase of the superensemble. A new single spectral model was next designed that included the weighted sum of the six cumulus parameterization schemes strung out within this model. This model was next shown to outperform in NWP forecasts at precipitation compared to any of those models that used a single cumulus parameterization scheme. This merely suggests that no single, present scheme is superior to all other schemes over the entire tropical belt; they all seem to have some virtues over different geographical regions. This Unified collective scheme is physically based since it does carry mechanisms such as mass flux, moisture convergence. cloud detrainment, downdrafts, effects of sea surface temperature etc. that are explicitly carried within one or the other schemes. This collective scheme is, however, based on optimized weights for these processes that vary geographically. It is our premise that even if a new breakthrough in cumulus parameterization were to occur from the development of a new scheme, that scheme, at best, may only achieve a skill ranking of number three for precipitation forecasts. The first place, we noted, still belongs to a multi-model superensemble, based on the optimal combination of six separate models. The second place belongs to the single model that utilizes a strung out weighted sum of many cumulus parameterization schemes within it. The individual member models have larger precipitation forecast errors compared to the two above. The skills, here, are evaluated using standard metrics such as correlations, root mean square errors and the equitable threat scores; finally we also present the vertical profiles of the apparent heat source and the apparent moisture sink that also confirm these above findings."
"35894581100;","Atmospheric simulations using a GCM with simplified physical parametrizations. I: Model climatology and variability in multi-decadal experiments",2003,"10.1007/s00382-002-0268-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037273134&doi=10.1007%2fs00382-002-0268-2&partnerID=40&md5=41309f6f22069828d8ec71ee18b3b4d2","This work describes the formulation and climatology of an atmospheric general circulation model (GCM) of intermediate complexity, based on a spectral primitive-equation dynamical core and a set of simplified physical parametrization schemes. The parametrization package has been specially designed to work in models with just a few vertical levels, and is based on the same physical principles adopted in the schemes of state-of-the art GCMs. The parametrized processes include large-scale condensation, convection, clouds, short-wave and long-wave radiation, surface fluxes and vertical diffusion. In the current configuration, the model (nicknamed SPEEDY, from Simplified Parametrizations, primitivE-Equation DYnamics"") has five vertical levels and a spectral truncation at total wave number 30 (T30L5). The top vertical level (crudely) represents the stratosphere, the bottom one the planetary boundary layer. Computationally, SPEEDY requires (at least) one order of magnitude less CPU time than a state-of-the-art GCM at the same horizontal resolution, and is therefore suitable for studies of inter-decadal or inter-centennial variability. Statistics of the model mean state and variability are computed from an ensemble of 41-year simulations forced by observed sea-surface temperatures in the period 1952-1992. The model mean state is closer to the observed climatology during the (boreal) winter than during summer. In winter (i.e. December to February, DJF), the model underestimates the amplitude of the Northern Hemisphere stationary wave pattern, particularly in the European-Atlantic sector. Some aspects of the systematic error of SPEEDY are in fact typical of many GCMs, although the error amplitude is stronger than in state-of-the-art models. On the other hand, the global distribution of precipitation in DJF is quite realistic, and compares well with that of more complex GCMs. In summer (June to August), a strong negative bias in the mid-tropospheric temperature generates a Northern Hemisphere circulation with some springtime characteristics. In particular, the position of the Tropical Convergence Zone in the Indian Ocean remains too far south, leading to a deficient simulation of the monsoon circulation over South Asia. The simulated variability during the northern winter is reasonably realistic as far as the spatial distribution is concerned, although some underestimation in the intensity can be found, particularly in the low-frequency range and in the Atlantic sector. The atmospheric response to ENSO events is also weaker than observed, although the spatial patterns of the rainfall and geopotential response in the Pacific sector are in phase with their observed counterparts. In the Atlantic/Eurasian region, the spatial patterns associated with the interdecadal trends in the simulated and observed large-scale circulation show a clear positive correlation, consistent with the hypothesis of a positive ocean-atmosphere feedback on decadal time scales."