The International Satellite Cloud Climatology Project (ISCCP) D2 dataset is used to study the global dis- tribution of low, middle and high cloud amounts and their trends of 1983—2001. Evidences have shown that globa...The International Satellite Cloud Climatology Project (ISCCP) D2 dataset is used to study the global dis- tribution of low, middle and high cloud amounts and their trends of 1983—2001. Evidences have shown that global warming has accelerated over the past 20 a and the 1990s was the warmest decade in the instrumental records since 1861. Trends of various clouds amounts over this period are analyzed by employing the linear regression method. The results show that global mean total cloud amounts, in general, have tended to reduce over the past 20 a. But there are slightly increasing by about 2% before 1987 and decreasing by about 4% since then. Cloudiness trends of both low and high clouds decrease while increase for the middle cloud. And there exist remarkable discrepancies in different regions. The preliminary analyses suggest that it is likely that the cloud change occurring over the past 20 a is a positive feed- back to global warming.展开更多
Based on time series and linear trend analysis, the authors evaluated the performance of the fourth gen- eration atmospheric general circulation model developed at the Institute of Atmospheric Physics, Chinese Academy...Based on time series and linear trend analysis, the authors evaluated the performance of the fourth gen- eration atmospheric general circulation model developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences （IAP AGCM4.0）, in simulating surface air temperature （SAT） during the twentieth century over China and the globe. The numerical experiment is con- ducted by driving the model with the observed sea surface temperature and sea ice. It is shown that IAP AGCM4.0 can simulate the warming trend of the global SAT, with the major wanning regions in the high latitudes of the Northern Hemisphere and the mid-latitudes of the South- ern Hemisphere. While the simulated trend over the whole globe is close to the observation, the model trader- estimates the observed trend over the continents. More- over, the model simulates the spatial distribution of SAT in China, with a bias of approximately -2℃ in eastern China, but with a more serious bias in western China. Compared with the global mean, however, the correlation coefficient between the simulation and observation in China is significantly lower, indicating that there is large uncertainty in simulating regional climate change.展开更多
Seasonal variations in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon are analyzed using 10-year (1998-2007) Tropical Rainfall Measuring Mission (TRMM) precipitation radar (...Seasonal variations in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon are analyzed using 10-year (1998-2007) Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) rain products (2A25). Datasets from the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) 24 general circulation models (GCMs) are evaluated using TRMM PR rain products in terms of their ability to simulate convective and stratiform precipitation and their deficiencies. The results show that Asian monsoon convective and stratiform precipitation increases significantly after onset of the summer monsoon, but the percentage of convective precipitation clearly decreases over tropical areas while it increases in subtropical regions. The GCMs simulate well the seasonal variation in the contribution of Asian monsoon subtropical convective precipitation to the total rainfall; however, the simulated convective precipitation amount is high while the simulated stratiform precipitation amount is low relative to TRMM measurements, especially over the Asian monsoon tropical region. There is simultaneous TRMM-observed convective and stratiform precipitation in space and time, but GCMs cannot simulate this relationship between convective and stratiform precipitation, resulting in the deficiency of stratiform precipitation simulations.展开更多
The summer rainfall over the middle-lower reaches of the Yangtze River valley (YRSR) has been estimated with a multi-linear regression model using principal atmospheric modes derived from a 500 hPa geopotential height...The summer rainfall over the middle-lower reaches of the Yangtze River valley (YRSR) has been estimated with a multi-linear regression model using principal atmospheric modes derived from a 500 hPa geopotential height and a 700 hPa zonal vapor flux over the domain of East Asia and the West Pacific.The model was developed using data from 1958 92 and validated with an independent prediction from 1993 2008.The independent prediction was efficient in predicting the YRSR with a correlation coefficient of 0.72 and a relative root mean square error of 18%.The downscaling model was applied to two general circulation models (GCMs) of Flexible Global Ocean-Atmosphere-Land System Model (FGOALS) and Geophysical Fluid Dynamics Laboratory coupled climate model version 2.1 (GFDL-CM2.1) to project rainfall for present and future climate under B1 and A1B emission scenarios.The downscaled results pro-vided a closer representation of the observation compared to the raw models in the present climate.In addition,compared to the inconsistent prediction directly from dif-ferent GCMs,the downscaled results provided a consistent projection for this half-century,which indicated a clear increase in the YRSR.Under the B1 emission scenario,the rainfall could increase by an average of 11.9% until 2011 25 and 17.2% until 2036 50 from the current state;under the A1B emission scenario,rainfall could increase by an average of 15.5% until 2011 25 and 25.3% until 2036 50 from the current state.Moreover,the increased rate was faster in the following decade (2011 25) than the latter of this half-century (2036 50) under both emissions.展开更多
Regional climate models (RCMs) have the potential for more detailed surface characteristic and mesoscale modeling results than general circulation models (GCMs).These advantages have drawn significant focus on RCM dev...Regional climate models (RCMs) have the potential for more detailed surface characteristic and mesoscale modeling results than general circulation models (GCMs).These advantages have drawn significant focus on RCM development in East Asia.The Regional Integrated Environment Modeling System,version 2.0 (RIEMS2.0),has been developed from an earlier RCM,RIEMS1.0,by the Key Laboratory of Regional ClimateEnvironment for Temperate East Asia (RCE-TEA) and Nanjing University.A numerical experiment covering 1979 to 2008 (simulation duration from 1 January 1978 to 31 December 2008) with a 50-km spatial resolution was performed to test the ability of RIEMS2.0 to simulate long-term climate and climate changes in East Asia and to provide a basis for further development and applications.The simulated surface air temperature (SAT) was compared with observed meteorological data.The results show that RIEMS2.0 simulation reproduced the SAT spatial distribution in East Asia but that it was underestimated.The simulated 30-year averaged SAT was approximately 2.0°C lower than the observed SAT.The annual and interannual variations in the averaged SAT and their anomalies were both well reproduced in the model.A further analysis of three sub-regions representing different longitudinal ranges showed that there is a good correlation and consistency between the simulated results and the observed data.The annual variations,interannual variations for the averaged SAT,and the anomalies in the three sub-regions were also captured well by the model.In summary,RIEMS2.0 shows stability and does well both in simulating the long-term SAT in East Asia and in expressing sub-regional characteristics.展开更多
The future climate dynamical downscaling method is that output of general circulation models( GCMs) is employed to provide initial conditions,lateral boundary conditions,sea surface temperatures,and initial land surfa...The future climate dynamical downscaling method is that output of general circulation models( GCMs) is employed to provide initial conditions,lateral boundary conditions,sea surface temperatures,and initial land surface conditions to regional climate models( RCMs). There are two methods of downscaling: offline coupling and online coupling. The two kinds of coupling methods are described in detail by coupling the Weather Research and Forecasting model( WRF) with the Institute of Atmospheric Physics of Chinese Academy of Sciences Atmospheric General Circulation Model Version 4. 0( IAP AGCM4. 0) in the study. And the extreme precipitation event over Beijing on July 212012 is simulated by using the two coupling methods. Results show that online coupling method is of great value in improving the model simulation. Furthermore,the data exchange frequency of online coupling has some effect on simulation result.展开更多
Simulated outgoing longwave radiation （OLR） outputs by two versions of the grid-point atmospheric general circulation model （GAMIL） were analyzed to assess the influences of improvements in cloud microphysics and ...Simulated outgoing longwave radiation （OLR） outputs by two versions of the grid-point atmospheric general circulation model （GAMIL） were analyzed to assess the influences of improvements in cloud microphysics and convective parameterization schemes on the simulation of the Madden-Julian oscillation （MJO） and other tropical waves. The wavenumber-frequency spectral analysis was applied to isolate dominant modes of convectively coupled equatorial waves, including the M30, Kelvin, equatorial Rossby （ER）, mixed Rossby-gravity （MRG）, and inertio-gravity （1G） waves. The performances of different versions of the GAMIL model （version 1.0 （GAMIL1.0） and version 2.0 （GAMIL2.0）） were evalu- ated by comparing the power spectrum distributions of these waves among GAMIL 1.0, GAMIL2.0, and observational data. GAMIL1.0 shows a weak MJO signal, with the maximum variability occurring separately at wavenumbers 1 and 4 rather than being concentrated on wavenumbers 1-3, suggesting that GAMILI.0 could not effectively capture the intraseasonal variability. However, GAMIL2.0 is able to effectively reproduce both the symmetric and anti-symmetric waves, and the significant spectra of the MJO, Kelvin, and MRG waves are in agreement with observational data, indicating that the ability of GAMIL2.0 to simulate the MJO and other tropical waves is enhanced by improving the cloud microphysics and convective parameterization schemes and implying that such improvements are crucial to further improving this model＇s performance.展开更多
Instead of using complicated general circulation models (GCMs), a simple semi-analytical model based on ray theory has been used to study energy evolution and ray path of Rossby waves in slowly varying mean flows. Our...Instead of using complicated general circulation models (GCMs), a simple semi-analytical model based on ray theory has been used to study energy evolution and ray path of Rossby waves in slowly varying mean flows. Our model yields similar results to those calculated from barotropic models, and also provides a chance to study Rossby waves in the slowly varying flows with both vertical and meridional shears. The model results show that upward Rossby waves can only grow in westerlies, and decay when further ascend. The baroclinic Rossky waves are restrained by the β effect in lower latitude. In the westerly jet with meridional and vertical shears, the barotropic Rossby waves originated from south of the westerly jet, and these can grow while propagating upper-northward. The baroclinic Rossby waves originated from north of the westerly jet and can grow while propagating upward and southward. Such a semi-analytical model provides a simple forecasting tool to allow study of the local weather anomalies to the heating/topography forcing associated with the global warming.展开更多
文摘The International Satellite Cloud Climatology Project (ISCCP) D2 dataset is used to study the global dis- tribution of low, middle and high cloud amounts and their trends of 1983—2001. Evidences have shown that global warming has accelerated over the past 20 a and the 1990s was the warmest decade in the instrumental records since 1861. Trends of various clouds amounts over this period are analyzed by employing the linear regression method. The results show that global mean total cloud amounts, in general, have tended to reduce over the past 20 a. But there are slightly increasing by about 2% before 1987 and decreasing by about 4% since then. Cloudiness trends of both low and high clouds decrease while increase for the middle cloud. And there exist remarkable discrepancies in different regions. The preliminary analyses suggest that it is likely that the cloud change occurring over the past 20 a is a positive feed- back to global warming.
基金supported by the Strategic Priority Research Program-Climate Change: Carbon Budget and Related Issues of the Chinese Academy of Sciences (Grant No. XDA05110201)the Development and Validation of High Resolution Climate System Model of the National Basic Research Program of China (Grant No.2010CB951901)
文摘Based on time series and linear trend analysis, the authors evaluated the performance of the fourth gen- eration atmospheric general circulation model developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences （IAP AGCM4.0）, in simulating surface air temperature （SAT） during the twentieth century over China and the globe. The numerical experiment is con- ducted by driving the model with the observed sea surface temperature and sea ice. It is shown that IAP AGCM4.0 can simulate the warming trend of the global SAT, with the major wanning regions in the high latitudes of the Northern Hemisphere and the mid-latitudes of the South- ern Hemisphere. While the simulated trend over the whole globe is close to the observation, the model trader- estimates the observed trend over the continents. More- over, the model simulates the spatial distribution of SAT in China, with a bias of approximately -2℃ in eastern China, but with a more serious bias in western China. Compared with the global mean, however, the correlation coefficient between the simulation and observation in China is significantly lower, indicating that there is large uncertainty in simulating regional climate change.
基金supported by National Natural Science Foundation of China (Grant No. 40428002)Scientific Research on Public Causes of China (Grant No. 2004 CB418303)
文摘Seasonal variations in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon are analyzed using 10-year (1998-2007) Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) rain products (2A25). Datasets from the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) 24 general circulation models (GCMs) are evaluated using TRMM PR rain products in terms of their ability to simulate convective and stratiform precipitation and their deficiencies. The results show that Asian monsoon convective and stratiform precipitation increases significantly after onset of the summer monsoon, but the percentage of convective precipitation clearly decreases over tropical areas while it increases in subtropical regions. The GCMs simulate well the seasonal variation in the contribution of Asian monsoon subtropical convective precipitation to the total rainfall; however, the simulated convective precipitation amount is high while the simulated stratiform precipitation amount is low relative to TRMM measurements, especially over the Asian monsoon tropical region. There is simultaneous TRMM-observed convective and stratiform precipitation in space and time, but GCMs cannot simulate this relationship between convective and stratiform precipitation, resulting in the deficiency of stratiform precipitation simulations.
基金supported by the National Basic Research Program of China (Grant No.2010CB950400)the National Natural Science Foundation of China (Key Project,Grant No.41030961)the Australia-China Bilateral Climate Change Partnerships Program of the Australian Department of Climate Change
文摘The summer rainfall over the middle-lower reaches of the Yangtze River valley (YRSR) has been estimated with a multi-linear regression model using principal atmospheric modes derived from a 500 hPa geopotential height and a 700 hPa zonal vapor flux over the domain of East Asia and the West Pacific.The model was developed using data from 1958 92 and validated with an independent prediction from 1993 2008.The independent prediction was efficient in predicting the YRSR with a correlation coefficient of 0.72 and a relative root mean square error of 18%.The downscaling model was applied to two general circulation models (GCMs) of Flexible Global Ocean-Atmosphere-Land System Model (FGOALS) and Geophysical Fluid Dynamics Laboratory coupled climate model version 2.1 (GFDL-CM2.1) to project rainfall for present and future climate under B1 and A1B emission scenarios.The downscaled results pro-vided a closer representation of the observation compared to the raw models in the present climate.In addition,compared to the inconsistent prediction directly from dif-ferent GCMs,the downscaled results provided a consistent projection for this half-century,which indicated a clear increase in the YRSR.Under the B1 emission scenario,the rainfall could increase by an average of 11.9% until 2011 25 and 17.2% until 2036 50 from the current state;under the A1B emission scenario,rainfall could increase by an average of 15.5% until 2011 25 and 25.3% until 2036 50 from the current state.Moreover,the increased rate was faster in the following decade (2011 25) than the latter of this half-century (2036 50) under both emissions.
基金supported by the National Basic Research Program of China under Grant 2011CB952003the Chinese Academy of Sciences Strategic Priority Program under Grant XDA05090206the National Natural Science Foundation of China under Grant 40975053
文摘Regional climate models (RCMs) have the potential for more detailed surface characteristic and mesoscale modeling results than general circulation models (GCMs).These advantages have drawn significant focus on RCM development in East Asia.The Regional Integrated Environment Modeling System,version 2.0 (RIEMS2.0),has been developed from an earlier RCM,RIEMS1.0,by the Key Laboratory of Regional ClimateEnvironment for Temperate East Asia (RCE-TEA) and Nanjing University.A numerical experiment covering 1979 to 2008 (simulation duration from 1 January 1978 to 31 December 2008) with a 50-km spatial resolution was performed to test the ability of RIEMS2.0 to simulate long-term climate and climate changes in East Asia and to provide a basis for further development and applications.The simulated surface air temperature (SAT) was compared with observed meteorological data.The results show that RIEMS2.0 simulation reproduced the SAT spatial distribution in East Asia but that it was underestimated.The simulated 30-year averaged SAT was approximately 2.0°C lower than the observed SAT.The annual and interannual variations in the averaged SAT and their anomalies were both well reproduced in the model.A further analysis of three sub-regions representing different longitudinal ranges showed that there is a good correlation and consistency between the simulated results and the observed data.The annual variations,interannual variations for the averaged SAT,and the anomalies in the three sub-regions were also captured well by the model.In summary,RIEMS2.0 shows stability and does well both in simulating the long-term SAT in East Asia and in expressing sub-regional characteristics.
基金Supported by the National Natural Science Foundation of China(No.61602477)China Postdoctoral Science Foundation(No.2016M601158)National Key Research and Development Program of China(No.2016YFB0200804)
文摘The future climate dynamical downscaling method is that output of general circulation models( GCMs) is employed to provide initial conditions,lateral boundary conditions,sea surface temperatures,and initial land surface conditions to regional climate models( RCMs). There are two methods of downscaling: offline coupling and online coupling. The two kinds of coupling methods are described in detail by coupling the Weather Research and Forecasting model( WRF) with the Institute of Atmospheric Physics of Chinese Academy of Sciences Atmospheric General Circulation Model Version 4. 0( IAP AGCM4. 0) in the study. And the extreme precipitation event over Beijing on July 212012 is simulated by using the two coupling methods. Results show that online coupling method is of great value in improving the model simulation. Furthermore,the data exchange frequency of online coupling has some effect on simulation result.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW- Q11-04)the National Basic Research Program of China (2011 CB403505 and 2010CB950402)the National Natural Science Foundation of China (40975052)
文摘Simulated outgoing longwave radiation （OLR） outputs by two versions of the grid-point atmospheric general circulation model （GAMIL） were analyzed to assess the influences of improvements in cloud microphysics and convective parameterization schemes on the simulation of the Madden-Julian oscillation （MJO） and other tropical waves. The wavenumber-frequency spectral analysis was applied to isolate dominant modes of convectively coupled equatorial waves, including the M30, Kelvin, equatorial Rossby （ER）, mixed Rossby-gravity （MRG）, and inertio-gravity （1G） waves. The performances of different versions of the GAMIL model （version 1.0 （GAMIL1.0） and version 2.0 （GAMIL2.0）） were evalu- ated by comparing the power spectrum distributions of these waves among GAMIL 1.0, GAMIL2.0, and observational data. GAMIL1.0 shows a weak MJO signal, with the maximum variability occurring separately at wavenumbers 1 and 4 rather than being concentrated on wavenumbers 1-3, suggesting that GAMILI.0 could not effectively capture the intraseasonal variability. However, GAMIL2.0 is able to effectively reproduce both the symmetric and anti-symmetric waves, and the significant spectra of the MJO, Kelvin, and MRG waves are in agreement with observational data, indicating that the ability of GAMIL2.0 to simulate the MJO and other tropical waves is enhanced by improving the cloud microphysics and convective parameterization schemes and implying that such improvements are crucial to further improving this model＇s performance.
基金supported by the National Natural Science Foundation of China (U0733002,40810059005,40890155,40906014 and 40976015)the Youth Marine Science Foundation of State Oceanic Administration (2010218)
文摘Instead of using complicated general circulation models (GCMs), a simple semi-analytical model based on ray theory has been used to study energy evolution and ray path of Rossby waves in slowly varying mean flows. Our model yields similar results to those calculated from barotropic models, and also provides a chance to study Rossby waves in the slowly varying flows with both vertical and meridional shears. The model results show that upward Rossby waves can only grow in westerlies, and decay when further ascend. The baroclinic Rossky waves are restrained by the β effect in lower latitude. In the westerly jet with meridional and vertical shears, the barotropic Rossby waves originated from south of the westerly jet, and these can grow while propagating upper-northward. The baroclinic Rossby waves originated from north of the westerly jet and can grow while propagating upward and southward. Such a semi-analytical model provides a simple forecasting tool to allow study of the local weather anomalies to the heating/topography forcing associated with the global warming.
