The Cloud Feedback Model Intercomparisons Project (CFMIP) Observation Simulator Package (COSP) is adopted in the Grid-point Atmospheric Model of IAP LASG (GAMIL2) during CFMIP at Phase II to evaluate the model cloud f...The Cloud Feedback Model Intercomparisons Project (CFMIP) Observation Simulator Package (COSP) is adopted in the Grid-point Atmospheric Model of IAP LASG (GAMIL2) during CFMIP at Phase II to evaluate the model cloud fractions in a consistent way with satellite observations. The cloud simulation results embedded in the Atmospheric Model Intercomparison Project (AMIP) control experiment are presented using three satellite simulators: International Satellite Cloud Climatology Project (ISCCP), Moderate Resolution Imaging Spectroradiometer (MODIS), and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar onboard the Cloud- Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Overall, GAMIL2 can produce horizontal distributions of the low cloud fraction that are similar to the satellite observations, and its similarities to the observations on different levels are shown in Taylor diagrams. The discrepancies among satellite observations are also shown, which should be considered during evaluation.展开更多
Based on the variation of cloud fraction revealed by D2 Cloud Climatic Data of the InternationalSatellite Cloud Climatology Project and trend analysis methods, the trend of different types of cloud fractionover East A...Based on the variation of cloud fraction revealed by D2 Cloud Climatic Data of the InternationalSatellite Cloud Climatology Project and trend analysis methods, the trend of different types of cloud fractionover East Asia during 1984-2006 is obtained. The analysis focuses on the relationship between temperatureand different cloud fraction under the background of globe warming. The result shows a fluctuatingdecreasing tendency in the total cloud fraction, high-level cloud and low-level cloud over East Asia with thedecrement being 2.24%, 1.65% and 1.68%, respectively, while the mid-level cloud increases by 1.07%. Inaddition, there are great regional differences in cloud fraction. Temperature and water-vapor contentvariation caused by the greenhouse effects over East Asia is the primary reason for the variation of cloudfraction. Over the Tibetan Plateau, the Bay of Bengal and the Intertropical Convergence Zone, thetemperature is negatively correlated with high-level cloud, but positively correlated with mid- and low-levelcloud. However, over the West Pacific and the ocean east and north of Japan, the temperature is negativelycorrelated with low-level cloud but positively correlated with high-level cloud.展开更多
Cloud diurnal variation is crucial for regulating cloud radiative effects and atmospheric dynamics.However,it is often overlooked in the evaluation and development of climate models.Thus,this study aims to investigate...Cloud diurnal variation is crucial for regulating cloud radiative effects and atmospheric dynamics.However,it is often overlooked in the evaluation and development of climate models.Thus,this study aims to investigate the daily mean(CFR)and diurnal variation(CDV)of cloud fraction across high-,middle-,low-level,and total clouds in the FGOALS-f3-L general circulation model.The bias of total CDV is decomposed into the model biases in CFRs and CDVs of clouds at all three levels.Results indicate that the model generally underestimates low-level cloud fraction during the daytime and high-/middle-level cloud fraction at nighttime.The simulation biases of low clouds,especially their CDV biases,dominate the bias of total CDV.Compensation effects exist among the bias decompositions,where the negative contributions of underestimated daytime low-level cloud fraction are partially offset by the opposing contributions from biases in high-/middle-level clouds.Meanwhile,the bias contributions have notable land–ocean differences and region-dependent characteristics,consistent with the model biases in these variables.Additionally,the study estimates the influences of CFR and CDV biases on the bias of shortwave cloud radiative effects.It reveals that the impacts of CDV biases can reach half of those from CFR biases,highlighting the importance of accurate CDV representation in climate models.展开更多
Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study...Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study investigated cloud fractions and cloud radiative effects(CREs)over SC and SCS simulated by CMIP6 atmospheric models.Remarkable differences in cloud-radiation characteristics appeared over these two regions.In observations,considerable amounts of low-middle level clouds and cloud radiative cooling effect appeared over SC.In contrast,high clouds prevailed over SCS,where longwave and shortwave CREs offset each other,resulting in a weaker net cloud radiative effect(NCRE).The models underestimated NCRE over SC mainly due to weaker shortwave CRE and less cloud fractions.Conversely,most models overestimated NCRE over SCS because of stronger shortwave CRE and weaker longwave CRE.Regional CREs were closely linked to their dominant cloud fractions.Both observations and simulations showed a negative spatial correlation between total(low)cloud fraction and shortwave CRE over SC,especially in winter,and exhibited a positive correlation between high cloud fraction and longwave CRE over these two regions.Compared with SCS,most models overestimated the spatial correlation between low(high)cloud fraction and SWCRE(LWCRE)over SC,with larger bias ranges among models,indicating the exaggerated cloud radiative cooling(warming)effect caused by low(high)clouds.Moreover,most models struggled to describe regional ascent and its connection with CREs over SC while they can better reproduce these connections over SCS.This study further suggests that reasonable circulation conditions are crucial to simulating well cloud-radiation characteristics over the East Asian regions.展开更多
Fengyun-4 A(FY-4 A),the second generation of China’s geostationary meteorological satellite,provides high spatiotemporal resolution cloud products over East Asia.In this study,cloud fraction(CFR)and cloud top pressur...Fengyun-4 A(FY-4 A),the second generation of China’s geostationary meteorological satellite,provides high spatiotemporal resolution cloud products over East Asia.In this study,cloud fraction(CFR)and cloud top pressure(CTP)products in August 2017 derived from the Advanced Geosynchronous Radiation Imager(AGRI)aboard FY-4 A(AGRI/FY-4 A)are retrospectively compared with those from the Moderate Resolution Imaging Spectroradiometer(MODIS)aboard Terra(MODIS/Terra)over East Asia.To avoid possible errors in the comparison caused by the lower temporal coverage of MODIS/Terra products compared to that of AGRI/FY-4 A over the same region and to account for time lags between observations of the two instruments,we construct datasets of AGRI/FY-4 A CFR and CTP to match those of MODIS/Terra in each scan over East Asia in August 2017.Results show that the CFR and CTP datasets of the two instruments generally agree well,with the linear correlation coefficients(R)between CFR(CTP)data of 0.83(0.80)regardless of time lags.Though longer time lags contribute to the worse consistency between CFR(CTP)data derived from observations of the two instruments in most cases,large CFR/CTP discrepancies do not always match with long time lags.Large CFR discrepancies appear in the vicinity of the Tibetan Plateau(TP;28°–45°N,75°–105°E).These differences in the cloud detection by the two instruments largely occur when MODIS/Terra detects clear-sky while AGRI/FY-4 A detects higher values of CFR,and this accounts for 61%of the CFR discrepancy greater than 50%near the TP.In the case of CTP,the largest discrepancies appear in the eastern Iranian Plateau(IP;25°–45°N,60°–80°E),where there are some samples with long time lags(20–35 min)and fewer daily data samples are available for computing monthly means compared to other regions since there are many clearsky data samples there during the study period.展开更多
The modern development in cloud technologies has turned the idea of cloud gaming into sensible behaviour. The cloud gaming provides an interactive gaming application, which remotely processed in a cloud system, and it...The modern development in cloud technologies has turned the idea of cloud gaming into sensible behaviour. The cloud gaming provides an interactive gaming application, which remotely processed in a cloud system, and it streamed the scenes as video series to play through network. Therefore, cloud gaming is a capable approach, which quickly increases the cloud computing platform. Obtaining enhanced user experience in cloud gaming structure is not insignificant task because user anticipates less response delay and high quality videos. To achieve this, cloud providers need to be able to accurately predict irregular player workloads in order to schedule the necessary resources. In this paper, an effective technique, named as Fractional Rider Deep Long Short Term Memory (LSTM) network is developed for workload prediction in cloud gaming. The workload of each resource is computed based on developed Fractional Rider Deep LSTM network. Moreover, resource allocation is performed by fractional Rider-based Harmony Search Algorithm (Rider-based HSA). This Fractional Rider-based HSA is developed by combining Fractional calculus (FC), Rider optimization algorithm (ROA) and Harmony search algorithm (HSA). Moreover, the developed Fractional Rider Deep LSTM is developed by integrating FC and Rider Deep LSTM. In addition, the multi-objective parameters, namely gaming experience loss QE, Mean Opinion Score (MOS), Fairness, energy, network parameters, and predictive load are considered for efficient resource allocation and workload prediction. Additionally, the developed workload prediction model achieved better performance using various parameters, like fairness, MOS, QE, energy and delay. Hence, the developed Fractional Rider Deep LSTM model showed enhanced results with maximum fairness, MOS, QE of 0.999, 0.921, 0.999 and less energy and delay of 0.322 and 0.456.展开更多
Based on the data from International Satellite Cloud Climatology Project (ISCCP) and Earth Radiation Budget Experiment (ERBE), the climatic cloud properties and cloud radiative forcing in the eastern China and the Ind...Based on the data from International Satellite Cloud Climatology Project (ISCCP) and Earth Radiation Budget Experiment (ERBE), the climatic cloud properties and cloud radiative forcing in the eastern China and the Indian monsoon region are compared. Although both of the Indian monsoon region and the eastern China are included in the Asian monsoon region and the seasonal cycles of rainfall are in phase, the properties of clouds and related cloud radiative forcing are significantly different. All of cloud components in the Indian region have similar phase structure of seasonal cycle. The maximum cloud fractions occur in the summer monsoon period and high clouds dominate the total cloud fraction. However, the seasonal features of clouds in the eastern China are complex. It is the mid-low clouds rather than high clouds dominating the total cloud fraction. The maximum total cloud fraction occurs in spring season. The total cloud and mid-low cloud fractions in winter season are larger than that in summer season. A unique global distinction of clouds in the eastern China is the largest cover of nimbostratus clouds. Reflecting to the cloud properties, the maximums of negative short wave, positive long wave and negative net cloud radiative forcing in the Indian monsoon region are in the summer season. In the eastern China, large negative short wave cloud radiative forcing occurs in early summer. The annual mean negative net cloud radiative forcing in the eastern China is obviously larger than that in the Indian region. Key words Cloud Radiative Forcing - Cloud Fraction Monsoon - Nimbostratus This work was jointly supported by the National Natural Science Foundation of China (Grant No.40023001) and Chinese Academy of Sciences under grant “ Hundred Talents” for “ Validation of Coupled Climate system models”.展开更多
The planetary boundary layer turbulence and moist convection parameterizations have been modified recently in the NASA Goddard Institute for Space Studies （GISS） Model E2 atmospheric general circulation model （GCM;...The planetary boundary layer turbulence and moist convection parameterizations have been modified recently in the NASA Goddard Institute for Space Studies （GISS） Model E2 atmospheric general circulation model （GCM; post-CMIP5, hereafter P5）. In this study, single column model （SCM_P5） simulated cloud fractions （CFs）, cloud liquid water paths （LWPs） and precipitation were compared with Atmospheric Radiation Measurement （ARM） Southern Great Plains （SGP） groundbased observations made during the period 2002-08. CMIP5 SCM simulations and GCM outputs over the ARM SGP region were also used in the comparison to identify whether the causes of cloud and precipitation biases resulted from either the physical parameterization or the dynamic scheme. The comparison showed that the CMIP5 SCM has difficulties in simulating the vertical structure and seasonal variation of low-level clouds. The new scheme implemented in the turbulence parameterization led to significantly improved cloud simulations in P5. It was found that the SCM is sensitive to the relaxation time scale. When the relaxation time increased from 3 to 24 h, SCM_P5-simulated CFs and LWPs showed a moderate increase （10%-20%） but precipitation increased significantly （56%）, which agreed better with observations despite the less accurate atmospheric state. Annual averages among the GCM and SCM simulations were almost the same, but their respective seasonal variations were out of phase. This suggests that the same physical cloud parameterization can generate similar statistical results over a long time period, but different dynamics drive the differences in seasonal variations. This study can potentially provide guidance for the further development of the GISS model.展开更多
The Multivariate and Minimum Residual （MMR） cloud detection and retrieval algorithm,previously developed and tested on simulated observations and Advanced Infrared Sounder radiance,was explored and validated using v...The Multivariate and Minimum Residual （MMR） cloud detection and retrieval algorithm,previously developed and tested on simulated observations and Advanced Infrared Sounder radiance,was explored and validated using various radiances from multiple sensors.For validation,the cloud retrievals were compared to independent cloud products from CloudSat,MODIS （Moderate Resolution Imaging Spectroradiometer）,and GOES （Geostationary Operational Environmental Satellites）.We found good spatial agreement within a single instrument,although the cloud fraction on each pixel was estimated independently.The retrieved cloud properties showed good agreement using radiances from multiple satellites,especially for the vertically integrated cloud mask.The accuracy of the MMR scheme in detecting mid-level clouds was found to be higher than for higher and lower clouds.The accuracy in retrieving cloud top pressures and cloud profiles increased with more channels from observations.For observations with fewer channels,the MMR solution was an ＂overly smoothed＂ estimation of the true vertical profile,starting from a uniform clear guess.Additionally,the retrieval algorithm showed some meaningful skill in simulating the cloudy radiance as a linear observation operator,discriminating between numerical weather prediction （NWP） error and cloud effects.The retrieval scheme was also found to be robust when different radiative transfer models were used.The potential application of the MMR algorithm in NWP with multiple radiances is also discussed.展开更多
Clouds are a dominant modulator of the energy budget.The cloud shortwave radiative effect at the surface(CRE)is closely related to the cloud macro-and micro-physical properties.Systematic observation of surface irradi...Clouds are a dominant modulator of the energy budget.The cloud shortwave radiative effect at the surface(CRE)is closely related to the cloud macro-and micro-physical properties.Systematic observation of surface irradiance and cloud properties are needed to narrow uncertainties in CRE.In this study,1-min irradiance and Total Sky Imager measurements from 2005 to 2009 at Xianghe in North China Plain are used to estimate cloud types,evaluate cloud fraction(CF),and quantify the sensitivities of surface irradiance with respect to changes in CF whether clouds obscure the sun or not.The annual mean CF is 0.50,further noting that CF exhibits a distinct seasonal variation,with a minimum in winter(0.37)and maximum in summer(0.68).Cumulus occurs more frequently in summer(32%),which is close to the sum of the occurrence of stratus and cirrus.The annual CRE is–54.4 W m^(–2),with seasonal values ranging from^(–2)9.5 W m^(–2)in winter and–78.2 W m^(–2)in summer.When clouds do not obscure the sun,CF is a dominant factor affecting diffuse irradiance,which in turn affects global irradiance.There is a positive linear relationship between CF and CRE under sun-unobscured conditions,the mean sensitivity of CRE for each CF 0.1 increase is about 1.2 W m^(–2)[79.5°<SZA(Solar Zenith Angle)<80.5°]to 7.0 W m^(–2)(29.5°<SZA<30.5°).When clouds obscure the sun,CF affects both direct and diffuse irradiance,resulting in a non-linear relationship between CF and CRE,and the slope decreases with increasing CF.It should be noted that,although only data at Xianghe is used in this study,our results are representative of neighboring areas,including most parts of the North China Plain.展开更多
Clouds can influence climate through many complex interactions within the hydrological cycle. Due to the important effects of cloud cover on climate, it is essential to study its variability over certain geographical ...Clouds can influence climate through many complex interactions within the hydrological cycle. Due to the important effects of cloud cover on climate, it is essential to study its variability over certain geographical areas. This study provides a spatial and temporal distribution of sky conditions, cloudy, partly cloudy, and clear days, in Iran. Cloud fraction parameters were calculated based on the cloud product （collection 6_L2） obtained from the Moderate Resolution Imaging Spectroradiorneter （MODIS） sensors on board the Terra （MOD06） and Aqua （MYD06） satellites. The cloud products were collected daily from January 1, 2003 to December 31, 2014 （12 years） with a spatial resolution of 5 km × 5 km. First, the cloud fraction data were converted into a regular geographic coordinate network over Iran. Then, the estimations from both sensors were analyzed. Results revealed that the maximum annual frequency of cloudy days occurs along the southern shores of the Caspian Sea, while the minimum annual frequency occurs in southeast Iran. On average, the annual number of cloudy and clear-sky days was 88 and 256 d from MODIS Terra, as compared to 96 and 244 d from MODIS Aqua. Generally, cloudy and partly cloudy days decrease from north to south, and MODIS Aqua overestimates the cloudy and partly cloudy days compared to MODIS Terra.展开更多
Cloud distribution characteristics over the Tibetan Plateau in the summer monsoon period simulated by the Australian Community Climate and Earth System Simulator(ACCESS) model are evaluated using COSP [the CFMIP(Cloud...Cloud distribution characteristics over the Tibetan Plateau in the summer monsoon period simulated by the Australian Community Climate and Earth System Simulator(ACCESS) model are evaluated using COSP [the CFMIP(Cloud Feedback Model Intercomparison Project) Observation Simulator Package]. The results show that the ACCESS model simulates less cumulus cloud at atmospheric middle levels when compared with observations from CALIPSO and CloudSat, but more ice cloud at high levels and drizzle drops at low levels. The model also has seasonal biases after the onset of the summer monsoon in May. While observations show that the prevalent high cloud at 9–10 km in spring shifts downward to 7–9 km,the modeled maximum cloud fractions move upward to 12–15 km. The reason for this model deficiency is investigated by comparing model dynamical and thermodynamical fields with those of ERA-Interim. It is found that the lifting effect of the Tibetan Plateau in the ACCESS model is stronger than in ERA-Interim, which means that the vertical velocity in the ACCESS model is stronger and more water vapor is transported to the upper levels of the atmosphere, resulting in more high-level ice clouds and less middle-level cumulus cloud over the Tibetan Plateau. The modeled radiation fields and precipitation are also evaluated against the relevant satellite observations.展开更多
The improvement of the accuracy of simulated cloud-related variables,such as the cloud fraction,in global climate models(GCMs)is still a challenging problem in climate modeling.In this study,the influence of cloud mic...The improvement of the accuracy of simulated cloud-related variables,such as the cloud fraction,in global climate models(GCMs)is still a challenging problem in climate modeling.In this study,the influence of cloud microphysics schemes(one-moment versus two-moment schemes)and cloud overlap methods(observation-based versus a fixed vertical decorrelation length)on the simulated cloud fraction was assessed in the BCC_AGCM2.0_CUACE/Aero.Compared with the fixed decorrelation length method,the observation-based approach produced a significantly improved cloud fraction both globally and for four representative regions.The utilization of a two-moment cloud microphysics scheme,on the other hand,notably improved the simulated cloud fraction compared with the one-moment scheme;specifically,the relative bias in the global mean total cloud fraction decreased by 42.9%–84.8%.Furthermore,the total cloud fraction bias decreased by 6.6%in the boreal winter(DJF)and 1.64%in the boreal summer(JJA).Cloud radiative forcing globally and in the four regions improved by 0.3%−1.2% and 0.2%−2.0%,respectively.Thus,our results showed that the interaction between clouds and climate through microphysical and radiation processes is a key contributor to simulation uncertainty.展开更多
Yangbajing (YBJ) is located in the Tibetan Plateau, China. The characteristics of solar radiation and its relationship with clouds at YBJ from April 2009 to April 2010 were analyzed in this paper. The annual mean sola...Yangbajing (YBJ) is located in the Tibetan Plateau, China. The characteristics of solar radiation and its relationship with clouds at YBJ from April 2009 to April 2010 were analyzed in this paper. The annual mean solar radiation was 478.4 W m 2 , and the annual mean transmittance was 0.713. The atmospheric mean trans- mittance of clear skies reaches 0.828 when the solar elevation angle (SEA) is greater than 10 degrees. Comparisons with numerical simulations show that the atmosphere of YBJ is clean. Impacts from atmospheric conditions on solar radiation are similar for clear skies during the year because the standard deviation of transmittance in clear skies was less than 0.05 when the SEA was greater than 10 degrees. It is important to understand the impact of clouds on solar radiation without considering other impact factors. In the last part of this article, the authors analyzed and established a statistical quantitative relationship between surface solar radiation and cloud fraction.展开更多
An analysis of global radiation measurements and fractional cloud cover observations made in the Israel Meteorological Service’s network of climate stations demonstrated a significant decrease in the transmittance of...An analysis of global radiation measurements and fractional cloud cover observations made in the Israel Meteorological Service’s network of climate stations demonstrated a significant decrease in the transmittance of solar radiation through the atmosphere during the last 60 years. The major cause was the reduced transparency of clouds. Under completely overcast skies with complete cloud cover transmission in the industrialized central coastal region decreased from 0.41 in the mid-20th century to 0.21 in the first decade of the 21st century. Under cloudless skies the reduction in the transmission of global radiation was less, from 0.79 to 0.71, and not statistically significant. Similar but somewhat smaller changes were observed in the less industrialized central hill region. Multi-linear analysis showed that since 1970, 61% of the measured decline in global radiation was attributable to changes in fractional cloud cover but only 2% to the marked increase in local fuel combustion;there was no statistically significant interaction between the two parameters.展开更多
基金supported by the National High Technology Research and Development Program of China (863 Program) (Grant No. 2010AA012304)the National Basic Research Program of China (973 Program) (Grant No.2010CB951904)+1 种基金the China Meteorological Administration R &D Special Fund for Public Welfare (meteorology) (Grant No.GYHY201006014)the National Natural Science Foundation of China (Grant Nos. 41023002 and 41005053)
文摘The Cloud Feedback Model Intercomparisons Project (CFMIP) Observation Simulator Package (COSP) is adopted in the Grid-point Atmospheric Model of IAP LASG (GAMIL2) during CFMIP at Phase II to evaluate the model cloud fractions in a consistent way with satellite observations. The cloud simulation results embedded in the Atmospheric Model Intercomparison Project (AMIP) control experiment are presented using three satellite simulators: International Satellite Cloud Climatology Project (ISCCP), Moderate Resolution Imaging Spectroradiometer (MODIS), and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar onboard the Cloud- Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Overall, GAMIL2 can produce horizontal distributions of the low cloud fraction that are similar to the satellite observations, and its similarities to the observations on different levels are shown in Taylor diagrams. The discrepancies among satellite observations are also shown, which should be considered during evaluation.
基金National Key Program for Developing Fundamental Sciences of China(2011CB952003)Natural Science Foundation of China(40975092,41275162)
文摘Based on the variation of cloud fraction revealed by D2 Cloud Climatic Data of the InternationalSatellite Cloud Climatology Project and trend analysis methods, the trend of different types of cloud fractionover East Asia during 1984-2006 is obtained. The analysis focuses on the relationship between temperatureand different cloud fraction under the background of globe warming. The result shows a fluctuatingdecreasing tendency in the total cloud fraction, high-level cloud and low-level cloud over East Asia with thedecrement being 2.24%, 1.65% and 1.68%, respectively, while the mid-level cloud increases by 1.07%. Inaddition, there are great regional differences in cloud fraction. Temperature and water-vapor contentvariation caused by the greenhouse effects over East Asia is the primary reason for the variation of cloudfraction. Over the Tibetan Plateau, the Bay of Bengal and the Intertropical Convergence Zone, thetemperature is negatively correlated with high-level cloud, but positively correlated with mid- and low-levelcloud. However, over the West Pacific and the ocean east and north of Japan, the temperature is negativelycorrelated with low-level cloud but positively correlated with high-level cloud.
基金supported by the National Natural Science Foundation of China[grant number 42275074].
文摘Cloud diurnal variation is crucial for regulating cloud radiative effects and atmospheric dynamics.However,it is often overlooked in the evaluation and development of climate models.Thus,this study aims to investigate the daily mean(CFR)and diurnal variation(CDV)of cloud fraction across high-,middle-,low-level,and total clouds in the FGOALS-f3-L general circulation model.The bias of total CDV is decomposed into the model biases in CFRs and CDVs of clouds at all three levels.Results indicate that the model generally underestimates low-level cloud fraction during the daytime and high-/middle-level cloud fraction at nighttime.The simulation biases of low clouds,especially their CDV biases,dominate the bias of total CDV.Compensation effects exist among the bias decompositions,where the negative contributions of underestimated daytime low-level cloud fraction are partially offset by the opposing contributions from biases in high-/middle-level clouds.Meanwhile,the bias contributions have notable land–ocean differences and region-dependent characteristics,consistent with the model biases in these variables.Additionally,the study estimates the influences of CFR and CDV biases on the bias of shortwave cloud radiative effects.It reveals that the impacts of CDV biases can reach half of those from CFR biases,highlighting the importance of accurate CDV representation in climate models.
基金Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)National Natural Science Foundation of China(72293604,42275026)Open Grants of the State Key Laboratory of Severe Weather(2023LASW-B09)。
文摘Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study investigated cloud fractions and cloud radiative effects(CREs)over SC and SCS simulated by CMIP6 atmospheric models.Remarkable differences in cloud-radiation characteristics appeared over these two regions.In observations,considerable amounts of low-middle level clouds and cloud radiative cooling effect appeared over SC.In contrast,high clouds prevailed over SCS,where longwave and shortwave CREs offset each other,resulting in a weaker net cloud radiative effect(NCRE).The models underestimated NCRE over SC mainly due to weaker shortwave CRE and less cloud fractions.Conversely,most models overestimated NCRE over SCS because of stronger shortwave CRE and weaker longwave CRE.Regional CREs were closely linked to their dominant cloud fractions.Both observations and simulations showed a negative spatial correlation between total(low)cloud fraction and shortwave CRE over SC,especially in winter,and exhibited a positive correlation between high cloud fraction and longwave CRE over these two regions.Compared with SCS,most models overestimated the spatial correlation between low(high)cloud fraction and SWCRE(LWCRE)over SC,with larger bias ranges among models,indicating the exaggerated cloud radiative cooling(warming)effect caused by low(high)clouds.Moreover,most models struggled to describe regional ascent and its connection with CREs over SC while they can better reproduce these connections over SCS.This study further suggests that reasonable circulation conditions are crucial to simulating well cloud-radiation characteristics over the East Asian regions.
基金Supported by the National Natural Science Foundation of China(41705021)Fundamental Research Funds for the Central Universities of China(lzujbky-2018-48)
文摘Fengyun-4 A(FY-4 A),the second generation of China’s geostationary meteorological satellite,provides high spatiotemporal resolution cloud products over East Asia.In this study,cloud fraction(CFR)and cloud top pressure(CTP)products in August 2017 derived from the Advanced Geosynchronous Radiation Imager(AGRI)aboard FY-4 A(AGRI/FY-4 A)are retrospectively compared with those from the Moderate Resolution Imaging Spectroradiometer(MODIS)aboard Terra(MODIS/Terra)over East Asia.To avoid possible errors in the comparison caused by the lower temporal coverage of MODIS/Terra products compared to that of AGRI/FY-4 A over the same region and to account for time lags between observations of the two instruments,we construct datasets of AGRI/FY-4 A CFR and CTP to match those of MODIS/Terra in each scan over East Asia in August 2017.Results show that the CFR and CTP datasets of the two instruments generally agree well,with the linear correlation coefficients(R)between CFR(CTP)data of 0.83(0.80)regardless of time lags.Though longer time lags contribute to the worse consistency between CFR(CTP)data derived from observations of the two instruments in most cases,large CFR/CTP discrepancies do not always match with long time lags.Large CFR discrepancies appear in the vicinity of the Tibetan Plateau(TP;28°–45°N,75°–105°E).These differences in the cloud detection by the two instruments largely occur when MODIS/Terra detects clear-sky while AGRI/FY-4 A detects higher values of CFR,and this accounts for 61%of the CFR discrepancy greater than 50%near the TP.In the case of CTP,the largest discrepancies appear in the eastern Iranian Plateau(IP;25°–45°N,60°–80°E),where there are some samples with long time lags(20–35 min)and fewer daily data samples are available for computing monthly means compared to other regions since there are many clearsky data samples there during the study period.
文摘The modern development in cloud technologies has turned the idea of cloud gaming into sensible behaviour. The cloud gaming provides an interactive gaming application, which remotely processed in a cloud system, and it streamed the scenes as video series to play through network. Therefore, cloud gaming is a capable approach, which quickly increases the cloud computing platform. Obtaining enhanced user experience in cloud gaming structure is not insignificant task because user anticipates less response delay and high quality videos. To achieve this, cloud providers need to be able to accurately predict irregular player workloads in order to schedule the necessary resources. In this paper, an effective technique, named as Fractional Rider Deep Long Short Term Memory (LSTM) network is developed for workload prediction in cloud gaming. The workload of each resource is computed based on developed Fractional Rider Deep LSTM network. Moreover, resource allocation is performed by fractional Rider-based Harmony Search Algorithm (Rider-based HSA). This Fractional Rider-based HSA is developed by combining Fractional calculus (FC), Rider optimization algorithm (ROA) and Harmony search algorithm (HSA). Moreover, the developed Fractional Rider Deep LSTM is developed by integrating FC and Rider Deep LSTM. In addition, the multi-objective parameters, namely gaming experience loss QE, Mean Opinion Score (MOS), Fairness, energy, network parameters, and predictive load are considered for efficient resource allocation and workload prediction. Additionally, the developed workload prediction model achieved better performance using various parameters, like fairness, MOS, QE, energy and delay. Hence, the developed Fractional Rider Deep LSTM model showed enhanced results with maximum fairness, MOS, QE of 0.999, 0.921, 0.999 and less energy and delay of 0.322 and 0.456.
基金the National Natural Science Foundation of China (GrantNo.40023001) Chinese Academy of Sciences under grant " Hundred Talent
文摘Based on the data from International Satellite Cloud Climatology Project (ISCCP) and Earth Radiation Budget Experiment (ERBE), the climatic cloud properties and cloud radiative forcing in the eastern China and the Indian monsoon region are compared. Although both of the Indian monsoon region and the eastern China are included in the Asian monsoon region and the seasonal cycles of rainfall are in phase, the properties of clouds and related cloud radiative forcing are significantly different. All of cloud components in the Indian region have similar phase structure of seasonal cycle. The maximum cloud fractions occur in the summer monsoon period and high clouds dominate the total cloud fraction. However, the seasonal features of clouds in the eastern China are complex. It is the mid-low clouds rather than high clouds dominating the total cloud fraction. The maximum total cloud fraction occurs in spring season. The total cloud and mid-low cloud fractions in winter season are larger than that in summer season. A unique global distinction of clouds in the eastern China is the largest cover of nimbostratus clouds. Reflecting to the cloud properties, the maximums of negative short wave, positive long wave and negative net cloud radiative forcing in the Indian monsoon region are in the summer season. In the eastern China, large negative short wave cloud radiative forcing occurs in early summer. The annual mean negative net cloud radiative forcing in the eastern China is obviously larger than that in the Indian region. Key words Cloud Radiative Forcing - Cloud Fraction Monsoon - Nimbostratus This work was jointly supported by the National Natural Science Foundation of China (Grant No.40023001) and Chinese Academy of Sciences under grant “ Hundred Talents” for “ Validation of Coupled Climate system models”.
基金supported by the DOE ASR program(Grant No.DESC008468)
文摘The planetary boundary layer turbulence and moist convection parameterizations have been modified recently in the NASA Goddard Institute for Space Studies （GISS） Model E2 atmospheric general circulation model （GCM; post-CMIP5, hereafter P5）. In this study, single column model （SCM_P5） simulated cloud fractions （CFs）, cloud liquid water paths （LWPs） and precipitation were compared with Atmospheric Radiation Measurement （ARM） Southern Great Plains （SGP） groundbased observations made during the period 2002-08. CMIP5 SCM simulations and GCM outputs over the ARM SGP region were also used in the comparison to identify whether the causes of cloud and precipitation biases resulted from either the physical parameterization or the dynamic scheme. The comparison showed that the CMIP5 SCM has difficulties in simulating the vertical structure and seasonal variation of low-level clouds. The new scheme implemented in the turbulence parameterization led to significantly improved cloud simulations in P5. It was found that the SCM is sensitive to the relaxation time scale. When the relaxation time increased from 3 to 24 h, SCM_P5-simulated CFs and LWPs showed a moderate increase （10%-20%） but precipitation increased significantly （56%）, which agreed better with observations despite the less accurate atmospheric state. Annual averages among the GCM and SCM simulations were almost the same, but their respective seasonal variations were out of phase. This suggests that the same physical cloud parameterization can generate similar statistical results over a long time period, but different dynamics drive the differences in seasonal variations. This study can potentially provide guidance for the further development of the GISS model.
基金sponsored by the 973 Program (Grant No. 2013CB430102)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)+3 种基金and the Air Force Weather Agencysupport from Craig S. SCHWARTZ, Allegrino Americo SAMUEL, and Gael DESCOMBES are greatly appreciatedsponsored by the National Science Foundationthe National Science Foundation
文摘The Multivariate and Minimum Residual （MMR） cloud detection and retrieval algorithm,previously developed and tested on simulated observations and Advanced Infrared Sounder radiance,was explored and validated using various radiances from multiple sensors.For validation,the cloud retrievals were compared to independent cloud products from CloudSat,MODIS （Moderate Resolution Imaging Spectroradiometer）,and GOES （Geostationary Operational Environmental Satellites）.We found good spatial agreement within a single instrument,although the cloud fraction on each pixel was estimated independently.The retrieved cloud properties showed good agreement using radiances from multiple satellites,especially for the vertically integrated cloud mask.The accuracy of the MMR scheme in detecting mid-level clouds was found to be higher than for higher and lower clouds.The accuracy in retrieving cloud top pressures and cloud profiles increased with more channels from observations.For observations with fewer channels,the MMR solution was an ＂overly smoothed＂ estimation of the true vertical profile,starting from a uniform clear guess.Additionally,the retrieval algorithm showed some meaningful skill in simulating the cloudy radiance as a linear observation operator,discriminating between numerical weather prediction （NWP） error and cloud effects.The retrieval scheme was also found to be robust when different radiative transfer models were used.The potential application of the MMR algorithm in NWP with multiple radiances is also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.41875183,41805021)the National Key R&D Program of China(Grant No.2017YFA0603504).
文摘Clouds are a dominant modulator of the energy budget.The cloud shortwave radiative effect at the surface(CRE)is closely related to the cloud macro-and micro-physical properties.Systematic observation of surface irradiance and cloud properties are needed to narrow uncertainties in CRE.In this study,1-min irradiance and Total Sky Imager measurements from 2005 to 2009 at Xianghe in North China Plain are used to estimate cloud types,evaluate cloud fraction(CF),and quantify the sensitivities of surface irradiance with respect to changes in CF whether clouds obscure the sun or not.The annual mean CF is 0.50,further noting that CF exhibits a distinct seasonal variation,with a minimum in winter(0.37)and maximum in summer(0.68).Cumulus occurs more frequently in summer(32%),which is close to the sum of the occurrence of stratus and cirrus.The annual CRE is–54.4 W m^(–2),with seasonal values ranging from^(–2)9.5 W m^(–2)in winter and–78.2 W m^(–2)in summer.When clouds do not obscure the sun,CF is a dominant factor affecting diffuse irradiance,which in turn affects global irradiance.There is a positive linear relationship between CF and CRE under sun-unobscured conditions,the mean sensitivity of CRE for each CF 0.1 increase is about 1.2 W m^(–2)[79.5°<SZA(Solar Zenith Angle)<80.5°]to 7.0 W m^(–2)(29.5°<SZA<30.5°).When clouds obscure the sun,CF affects both direct and diffuse irradiance,resulting in a non-linear relationship between CF and CRE,and the slope decreases with increasing CF.It should be noted that,although only data at Xianghe is used in this study,our results are representative of neighboring areas,including most parts of the North China Plain.
基金Under the auspices of Faculty of Geographical Science and Planning,University of Isfahan,Doctoral Climatology Project(No.168607/94)
文摘Clouds can influence climate through many complex interactions within the hydrological cycle. Due to the important effects of cloud cover on climate, it is essential to study its variability over certain geographical areas. This study provides a spatial and temporal distribution of sky conditions, cloudy, partly cloudy, and clear days, in Iran. Cloud fraction parameters were calculated based on the cloud product （collection 6_L2） obtained from the Moderate Resolution Imaging Spectroradiorneter （MODIS） sensors on board the Terra （MOD06） and Aqua （MYD06） satellites. The cloud products were collected daily from January 1, 2003 to December 31, 2014 （12 years） with a spatial resolution of 5 km × 5 km. First, the cloud fraction data were converted into a regular geographic coordinate network over Iran. Then, the estimations from both sensors were analyzed. Results revealed that the maximum annual frequency of cloudy days occurs along the southern shores of the Caspian Sea, while the minimum annual frequency occurs in southeast Iran. On average, the annual number of cloudy and clear-sky days was 88 and 256 d from MODIS Terra, as compared to 96 and 244 d from MODIS Aqua. Generally, cloudy and partly cloudy days decrease from north to south, and MODIS Aqua overestimates the cloudy and partly cloudy days compared to MODIS Terra.
基金funded by the Third Scientific Experiment of the Tibetan Plateau (Grant No. GYHY201406001)the National Natural Science Foundation of China (Grant Nos. 41575045, 41205030, and 41175046)the Basic Research Fund of the Chinese Academy of Meteorological Sciences (Grant No. 2017Z013)
文摘Cloud distribution characteristics over the Tibetan Plateau in the summer monsoon period simulated by the Australian Community Climate and Earth System Simulator(ACCESS) model are evaluated using COSP [the CFMIP(Cloud Feedback Model Intercomparison Project) Observation Simulator Package]. The results show that the ACCESS model simulates less cumulus cloud at atmospheric middle levels when compared with observations from CALIPSO and CloudSat, but more ice cloud at high levels and drizzle drops at low levels. The model also has seasonal biases after the onset of the summer monsoon in May. While observations show that the prevalent high cloud at 9–10 km in spring shifts downward to 7–9 km,the modeled maximum cloud fractions move upward to 12–15 km. The reason for this model deficiency is investigated by comparing model dynamical and thermodynamical fields with those of ERA-Interim. It is found that the lifting effect of the Tibetan Plateau in the ACCESS model is stronger than in ERA-Interim, which means that the vertical velocity in the ACCESS model is stronger and more water vapor is transported to the upper levels of the atmosphere, resulting in more high-level ice clouds and less middle-level cumulus cloud over the Tibetan Plateau. The modeled radiation fields and precipitation are also evaluated against the relevant satellite observations.
基金supported by the National Key R&D Program of China(2017YFA0603502)(Key)National Natural Science Foundation of China(91644211)S&T Development Fund of CAMS(2021KJ004).
文摘The improvement of the accuracy of simulated cloud-related variables,such as the cloud fraction,in global climate models(GCMs)is still a challenging problem in climate modeling.In this study,the influence of cloud microphysics schemes(one-moment versus two-moment schemes)and cloud overlap methods(observation-based versus a fixed vertical decorrelation length)on the simulated cloud fraction was assessed in the BCC_AGCM2.0_CUACE/Aero.Compared with the fixed decorrelation length method,the observation-based approach produced a significantly improved cloud fraction both globally and for four representative regions.The utilization of a two-moment cloud microphysics scheme,on the other hand,notably improved the simulated cloud fraction compared with the one-moment scheme;specifically,the relative bias in the global mean total cloud fraction decreased by 42.9%–84.8%.Furthermore,the total cloud fraction bias decreased by 6.6%in the boreal winter(DJF)and 1.64%in the boreal summer(JJA).Cloud radiative forcing globally and in the four regions improved by 0.3%−1.2% and 0.2%−2.0%,respectively.Thus,our results showed that the interaction between clouds and climate through microphysical and radiation processes is a key contributor to simulation uncertainty.
基金support from the National Special Fund for the Commonweal Industry (Meteorology)of China (Grant No. GYHY200806031)
文摘Yangbajing (YBJ) is located in the Tibetan Plateau, China. The characteristics of solar radiation and its relationship with clouds at YBJ from April 2009 to April 2010 were analyzed in this paper. The annual mean solar radiation was 478.4 W m 2 , and the annual mean transmittance was 0.713. The atmospheric mean trans- mittance of clear skies reaches 0.828 when the solar elevation angle (SEA) is greater than 10 degrees. Comparisons with numerical simulations show that the atmosphere of YBJ is clean. Impacts from atmospheric conditions on solar radiation are similar for clear skies during the year because the standard deviation of transmittance in clear skies was less than 0.05 when the SEA was greater than 10 degrees. It is important to understand the impact of clouds on solar radiation without considering other impact factors. In the last part of this article, the authors analyzed and established a statistical quantitative relationship between surface solar radiation and cloud fraction.
文摘An analysis of global radiation measurements and fractional cloud cover observations made in the Israel Meteorological Service’s network of climate stations demonstrated a significant decrease in the transmittance of solar radiation through the atmosphere during the last 60 years. The major cause was the reduced transparency of clouds. Under completely overcast skies with complete cloud cover transmission in the industrialized central coastal region decreased from 0.41 in the mid-20th century to 0.21 in the first decade of the 21st century. Under cloudless skies the reduction in the transmission of global radiation was less, from 0.79 to 0.71, and not statistically significant. Similar but somewhat smaller changes were observed in the less industrialized central hill region. Multi-linear analysis showed that since 1970, 61% of the measured decline in global radiation was attributable to changes in fractional cloud cover but only 2% to the marked increase in local fuel combustion;there was no statistically significant interaction between the two parameters.
