This paper examines the performance of an atmospheric general circulation model (AGCM) developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of ...This paper examines the performance of an atmospheric general circulation model (AGCM) developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics (LASG/IAP). It is a spectral model truncated at R42(2.8125°long×1.66°lat) resolution and with nine vertical levels, and referred to as R42L9/LASG hereafter. It is also the new version of atmospheric component model R15L9 of the global ocean-atmosphere-land system (GOALS/LASG). A 40-year simulation in which the model is forced with the climatological monthly mean sea surface temperature is compared with the 40-year (1958-97) U.S. National Center for Environmental Prediction (NGEP) global reanalysis and the 22-year (1979-2000) Xie-Arkin monthly precipitation climatology. The mean DJF and JJA geographical distributions of precipitation, sea level pressure, 500-hPa geopotential height, 850-hPa and 200-hPa zonal wind, and other fields averaged for the last 30-year integration of the R42L9 model are analyzed. Results show that the model reproduces well the observed basic patterns, particularly precipitation over the East Asian region. Comparing the new model with R15L9/LASG, the old version with coarse resolution (nearly 7.5°long×4.5°lat), shows an obvious improvement in the simulation of regional climate, especially precipitation. The weaknesses in simulation and future improvements of the model are also discussed.展开更多
Seasonal prediction of Asian-Australian monsoon （A-AM） precipitation is one of the most important and challenging tasks in climate prediction. In this paper, we evaluate the performance of Grid Atmospheric Model of ...Seasonal prediction of Asian-Australian monsoon （A-AM） precipitation is one of the most important and challenging tasks in climate prediction. In this paper, we evaluate the performance of Grid Atmospheric Model of IAP LASG （GAMIL） on retrospective prediction of the A-AM interannual variation （IAV）, and determine to what extent GAMIL can capture the two major observed modes of A-AM rainfall IAV for the period 1979-2003. The first mode is associated with the turnabout of warming （cooling） in the Nifio 3.4 region, whereas the second mode leads the warming/cooling by about one year, signaling precursory conditions for ENSO. We show that the GAMIL one-month lead prediction of the seasonal precipitation anomalies is primarily able to capture major features of the two observed leading modes of the IAV, with the first mode better predicted than the second. It also depicts the relationship between the first mode and ENSO rather well. On the other hand, the GAMIL has deficiencies in capturing the relationship between the second mode and ENSO. We conclude： （1） successful reproduction of the E1 Nifio-excited monsoon-ocean interaction and E1 Nifio forcing may be critical for the seasonal prediction of the A-AM rainfall IAV with the GAMIL; （2） more efforts are needed to improve the simulation not only in the Nifio 3.4 region but also in the joining area of Asia and the Indian-Pacific Ocean; （3） the selection of a one-tier system may improve the ultimate prediction of the A-AM rainfall IAV. These results offer some references for improvement of the GAMIL and associated seasonal prediction skill.展开更多
A fast version of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG）/Institute of Atmospheric Physics （IAP） climate system model is briefly documented. Th...A fast version of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG）/Institute of Atmospheric Physics （IAP） climate system model is briefly documented. The fast coupled model employs a low resolution version of the atmospheric component Grid Atmospheric Model of IAP/LASG （GAMIL）, with the other parts of the model, namely an oceanic component LASG/IAP Climate Ocean Model （LICOM）, land component Common Land Model （CLM）, and sea ice component from National Center for Atmospheric Research Community Climate System Model （NCAR CCSM2）, as the same as in the standard version of LASG/IAP Flexible Global Ocean Atmosphere Land System model （FGOALS_g）. The parameterizations of physical and dynamical processes of the atmospheric component in the fast version are identical to the standard version, although some parameter values are different. However, by virtue of reduced horizontal resolution and increased time-step of the most time-consuming atmospheric component, it runs faster by a factor of 3 and can serve as a useful tool for longterm and large-ensemble integrations. A 1000-year control simulation of the present-day climate has been completed without flux adjustments. The final 600 years of this simulation has virtually no trends in global mean sea surface temperatures and is recommended for internal variability studies. Several aspects of the control simulation＇s mean climate and variability are evaluated against the observational or reanalysis data. The strengths and weaknesses of the control simulation are evaluated. The mean atmospheric circulation is well simulated, except in high latitudes. The Asian-Australian monsoonal meridional cell shows realistic features, however, an artificial rainfall center is located to the eastern periphery of the Tibetan Plateau persists throughout the year. The mean bias of SST resembles that of the standard version, appearing as a ＂double ITCZ＂ （Inter-Tropical Convergence Zone） associated with a westward extension of the equatorial eastern Pacific cold tongue. The sea ice extent is acceptable but has a higher concentration. The strength of Atlantic meridional overturning is 27.5 Sv. Evidence from the 600-year simulation suggests a modulation of internal variability on ENSO frequency, since both regular and irregular oscillations of ENSO are found during the different time periods of the long-term simulation.展开更多
High computational performance is extremely important for climate system models, especially in ultra-high-resolution model development. In this study, the computational performance of the Finite-volume Atmospheric Mod...High computational performance is extremely important for climate system models, especially in ultra-high-resolution model development. In this study, the computational performance of the Finite-volume Atmospheric Model of the IAP/LASG （FAMIL） was comprehensively evaluated on Tianhe-2, which was the world＇s top-ranked supercomputer from June 2013 to May 2016. The standardized Atmospheric Model Inter-comparison Project （AMIP） type of experiment was carried out that focused on the computational performance of each node as well as the simulation year per day （SYPD）, the running cost speedup, and the scalability of the FAMIL. The results indicated that （1） based on five indexes （CPU usage, percentage of CPU kernel mode that occupies CPU time and of message passing waiting time （CPU SW）, code vectorization （VEC）, average of Gflops （Gflops_ AVE）, and peak of Gflops （Gflops_PK））, FAMIL shows excellent computational performance on every Tianhe-2 computing node; （2） considering SYPD and the cost speedup of FAMIL systematically, the optimal Message Passing Interface （MPI） numbers of processors （MNPs） choice appears when FAMIL use 384 and 1536 MNPs for C96 （100 km） and C384 （25 km）, respectively; and （3） FAMIL shows positive scalability with increased threads to drive the model. Considering the fast network speed and acceleration card in the MIC architecture on Tianhe-2, there is still significant room to improve the computational performance of FAMIL.展开更多
The extreme summer precipitation over East China during 1982-2007 was simulated using the LASG/IAP regional climate model CREM(the Climate version of a Regional Eta-coordinate Model).The results show that the probabil...The extreme summer precipitation over East China during 1982-2007 was simulated using the LASG/IAP regional climate model CREM(the Climate version of a Regional Eta-coordinate Model).The results show that the probability density functions(PDFs) of precipitation intensities are reasonably simulated,except that the PDFs of light and moderate rain are underestimated and that the PDFs of heavy rain are overestimated.The extreme precipitation amount(R95p) and the percent contribution of extreme precipitation to the total precipitation(R95pt) are also reasonably reproduced by the CREM.However,the R95p and R95pt over most of East China are generally overestimated,while the R95p along the coastal area of South China(SC) is underestimated.The bias of R95pt is consistent with the bias of precipitation intensity on wet days(SDII).The interannual variation for R95p anomalies(PC1) is well simulated,but that of R95pt anomalies(PC2) is poorly simulated.The skill of the model in simulating PC1(PC2) increases(decreases) from north to south.The bias of water vapor transport associated with the 95th percentile of summer daily precipitation(WVTr95) explains well the bias of the simulated extreme precipitation.展开更多
Coupled ocean-atmospheric general circulation models are the only tools to quantitatively simulate the climate system. Since the end of the 1980s, a group of scientists in the State Key Laboratory of Numerical Modelin...Coupled ocean-atmospheric general circulation models are the only tools to quantitatively simulate the climate system. Since the end of the 1980s, a group of scientists in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS), have been working to develop a global OGCM and a global coupled ocean-atmosphere general circulation modei (CGCM). Prom the original flux anomaly-coupling modei developed in the beginning of the 1990s to the latest directly-coupling modei, LASG scientists have developed four global coupled GCMs. This study summarizes the development history of these models and describes the third and fourth coupled GCMs and selected applications. Strengths and weaknesses of these models are highlighted.展开更多
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 lo...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.展开更多
Due to the decrease in grid size associated with the convergence of meridians toward the poles inspherical coordinates, the time steps in many global climate models with finite-difference method are restrictedto be un...Due to the decrease in grid size associated with the convergence of meridians toward the poles inspherical coordinates, the time steps in many global climate models with finite-difference method are restrictedto be unpleasantly small. To overcome the problem, a reduced grid is introduced to LASG/IAP world oceangeneral circulation models. The reduced grid is implemented successfully in the coarser resolutions versionmodel L30T63 at first. Then, it is carried out in the improved version model LICOM with finer resolutions. Inthe experiment with model L30T63, under time step unchanged though, execution time per single model run isshortened significantly owing to the decrease of grid number and filtering execution in high latitudes. Resultsfrom additional experiments with L30T63 show that the time step of integration can be quadrupled at most inreduced grid with refinement ratio 3. In the experiment with model LICOM and with the model’s original timestep unchanged, the model covered area is extended to the whole globe from its original case with the grid pointof North Pole considered as an isolated island and the results of experiment are shown to be acceptable.展开更多
The authors examine extreme summer temperatures over East China during 19844004 using a regional climate model named CREM （the Climate version of Regional Eta-coordinate Model）, which was developed by LASG/IAP. The ...The authors examine extreme summer temperatures over East China during 19844004 using a regional climate model named CREM （the Climate version of Regional Eta-coordinate Model）, which was developed by LASG/IAP. The results show that the main features of the extreme summer temperatures over East China are reproduced well by CREM, and the skill for the minimum temperature is higher than that for the maximum tem- perature, especially along the Yangtze-Huai River Valley （YHV）. The simulated extreme temperatures are lower than those of observation, especially for the maximum temperature. The bias of extreme temperatures is consistent with the cold bias of the climatological mean summer surface air temperature. The skill of the model in simulating the interannual variability of extreme temperatures increases from north to south. The simulated interannual variation of the minimum temperature is more reasonable than the maximum temperature. The underestimation of net solar radiation at the surface leads to a cold bias of the climatological mean temperature. Furthermore, the model underestimates the light and moderate rain, while overestimates heavy rain. It causes the simulated minimum temperature more reasonable than the maximum temperature.展开更多
基于2010~2019年ERA5单层再分析资料,结合安徽省淮南森林观测站2016年5月1日至2017年4月30日的大气边界层塔(PBL塔)观测资料,驱动陆面模式CLM4.5(Community Land Model Version 4.5),模拟了淮南山地森林下垫面上的陆面过程,并比较分析...基于2010~2019年ERA5单层再分析资料,结合安徽省淮南森林观测站2016年5月1日至2017年4月30日的大气边界层塔(PBL塔)观测资料,驱动陆面模式CLM4.5(Community Land Model Version 4.5),模拟了淮南山地森林下垫面上的陆面过程,并比较分析了不同驱动场对其影响,同时设计了土壤质地对土壤湿度影响的三个模拟试验。结果表明,CLM4.5对淮南森林陆气交换过程表现了较好的模拟性能,PBL塔观测资料驱动的总体模拟效果优于ERA5再分析资料的。在辐射模拟方面,CLM4.5利用ERA5资料和PBL塔观测资料,都很好地模拟了辐射分量,特别是PBL塔观测资料驱动的全年模拟结果与观测相关系数达0.97以上,均方根误差在25.056 W m^(-2)以下。ERA5再分析资料强迫模拟的相关系数略低,但也达到了0.92,均方根误差在29.939 W m^(-2)以下。在土壤温度模拟方面,相关系数都达到0.98以上;土壤湿度模拟的相关系数都在0.86以上,但系统性偏高;对感热通量的模拟全年平均的相关系数分别为0.72和0.78。实测的三层土壤质地加上深层给定的土壤质地的数据对土壤湿度的模拟结果与观测最为接近,土壤质地的准确描述可以大幅提高土壤湿度的模拟。本研究发现ERA5单层再分析资料在淮南森林站精度较好,可以应用于该山地森林区域陆—气交换过程的模拟研究。展开更多
Response of the Atlantic thermohaline circula- tion (THC) to global warming is examined by using the cli- mate system model developed at IAP/LASG. The evidence indicates that the gradually warming climate associated w...Response of the Atlantic thermohaline circula- tion (THC) to global warming is examined by using the cli- mate system model developed at IAP/LASG. The evidence indicates that the gradually warming climate associated with the increased atmospheric carbon dioxide leads to a warmer and fresher sea surface water at the high latitudes of the North Atlantic Ocean, which prevents the down-welling of the surface water. The succedent reduction of the pole-to- equator meridional potential density gradient finally results in the decrease of the THC in intensity. When the atmos- pheric carbon dioxide is doubled, the maximum value of the Atlantic THC decreases approximately by 8%. The associ- ated poleward oceanic heat transport also becomes weaker. This kind of THC weakening centralizes mainly in the northern part of the North Atlantic basin, indicating briefly a local scale adjustment rather than a loop oscillation with the whole Atlantic “conveyor belt” decelerating.展开更多
文摘This paper examines the performance of an atmospheric general circulation model (AGCM) developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics (LASG/IAP). It is a spectral model truncated at R42(2.8125°long×1.66°lat) resolution and with nine vertical levels, and referred to as R42L9/LASG hereafter. It is also the new version of atmospheric component model R15L9 of the global ocean-atmosphere-land system (GOALS/LASG). A 40-year simulation in which the model is forced with the climatological monthly mean sea surface temperature is compared with the 40-year (1958-97) U.S. National Center for Environmental Prediction (NGEP) global reanalysis and the 22-year (1979-2000) Xie-Arkin monthly precipitation climatology. The mean DJF and JJA geographical distributions of precipitation, sea level pressure, 500-hPa geopotential height, 850-hPa and 200-hPa zonal wind, and other fields averaged for the last 30-year integration of the R42L9 model are analyzed. Results show that the model reproduces well the observed basic patterns, particularly precipitation over the East Asian region. Comparing the new model with R15L9/LASG, the old version with coarse resolution (nearly 7.5°long×4.5°lat), shows an obvious improvement in the simulation of regional climate, especially precipitation. The weaknesses in simulation and future improvements of the model are also discussed.
基金the support of the National Natural Science Foundation of China(Grant Nos.40523001 and 40605022)the Chinese Acadiemy of the International Partnership Creative Group entitled"Climate System Model Development and Application Studies".
文摘Seasonal prediction of Asian-Australian monsoon （A-AM） precipitation is one of the most important and challenging tasks in climate prediction. In this paper, we evaluate the performance of Grid Atmospheric Model of IAP LASG （GAMIL） on retrospective prediction of the A-AM interannual variation （IAV）, and determine to what extent GAMIL can capture the two major observed modes of A-AM rainfall IAV for the period 1979-2003. The first mode is associated with the turnabout of warming （cooling） in the Nifio 3.4 region, whereas the second mode leads the warming/cooling by about one year, signaling precursory conditions for ENSO. We show that the GAMIL one-month lead prediction of the seasonal precipitation anomalies is primarily able to capture major features of the two observed leading modes of the IAV, with the first mode better predicted than the second. It also depicts the relationship between the first mode and ENSO rather well. On the other hand, the GAMIL has deficiencies in capturing the relationship between the second mode and ENSO. We conclude： （1） successful reproduction of the E1 Nifio-excited monsoon-ocean interaction and E1 Nifio forcing may be critical for the seasonal prediction of the A-AM rainfall IAV with the GAMIL; （2） more efforts are needed to improve the simulation not only in the Nifio 3.4 region but also in the joining area of Asia and the Indian-Pacific Ocean; （3） the selection of a one-tier system may improve the ultimate prediction of the A-AM rainfall IAV. These results offer some references for improvement of the GAMIL and associated seasonal prediction skill.
基金Acknowledgements. This work was jointly supported by the Chinese Academy of Sciences through the International Partnership Creative Group entitled ＂The Climate System Model Development and Application Studies＂, the Major State Basic Research Development Program of China （973 Program） under Grant No. 2005CB321703, and the National Natural Science Foundation of China （Grant Nos. 40675050, 40221503, 40625014）. The long-term integration of the coupled model was finished on the Lenovo DeepComp 6800 supercomputer at the Supercomputing Center of the Chinese Academy of Sciences, and the IBM SP690 at the Institute of Atmospheric Physics, Chinese Academy of Sciences. The authors appreciate the contribution of Drs. R. C. Yu, Y. Q. Yu, H. L. Liu, W. P. Zheng, J. Li, X. G Xin, and Mrs. H. Wan, H. M. Li in the model development and validations.
文摘A fast version of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG）/Institute of Atmospheric Physics （IAP） climate system model is briefly documented. The fast coupled model employs a low resolution version of the atmospheric component Grid Atmospheric Model of IAP/LASG （GAMIL）, with the other parts of the model, namely an oceanic component LASG/IAP Climate Ocean Model （LICOM）, land component Common Land Model （CLM）, and sea ice component from National Center for Atmospheric Research Community Climate System Model （NCAR CCSM2）, as the same as in the standard version of LASG/IAP Flexible Global Ocean Atmosphere Land System model （FGOALS_g）. The parameterizations of physical and dynamical processes of the atmospheric component in the fast version are identical to the standard version, although some parameter values are different. However, by virtue of reduced horizontal resolution and increased time-step of the most time-consuming atmospheric component, it runs faster by a factor of 3 and can serve as a useful tool for longterm and large-ensemble integrations. A 1000-year control simulation of the present-day climate has been completed without flux adjustments. The final 600 years of this simulation has virtually no trends in global mean sea surface temperatures and is recommended for internal variability studies. Several aspects of the control simulation＇s mean climate and variability are evaluated against the observational or reanalysis data. The strengths and weaknesses of the control simulation are evaluated. The mean atmospheric circulation is well simulated, except in high latitudes. The Asian-Australian monsoonal meridional cell shows realistic features, however, an artificial rainfall center is located to the eastern periphery of the Tibetan Plateau persists throughout the year. The mean bias of SST resembles that of the standard version, appearing as a ＂double ITCZ＂ （Inter-Tropical Convergence Zone） associated with a westward extension of the equatorial eastern Pacific cold tongue. The sea ice extent is acceptable but has a higher concentration. The strength of Atlantic meridional overturning is 27.5 Sv. Evidence from the 600-year simulation suggests a modulation of internal variability on ENSO frequency, since both regular and irregular oscillations of ENSO are found during the different time periods of the long-term simulation.
基金supported by the National Natural Science Foundation of China[grant number 41675100],[grant number91337110]the Third Tibetan Plateau Scientific Experiment:Observations for Boundary Layer and Troposphere[GYHY201406001]+1 种基金the Key Research Program of Frontier Sciences,Chinese Academy of Science(CAS)(QYZDY-SSW-DQC018)the Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund(the 2nd phase)
文摘High computational performance is extremely important for climate system models, especially in ultra-high-resolution model development. In this study, the computational performance of the Finite-volume Atmospheric Model of the IAP/LASG （FAMIL） was comprehensively evaluated on Tianhe-2, which was the world＇s top-ranked supercomputer from June 2013 to May 2016. The standardized Atmospheric Model Inter-comparison Project （AMIP） type of experiment was carried out that focused on the computational performance of each node as well as the simulation year per day （SYPD）, the running cost speedup, and the scalability of the FAMIL. The results indicated that （1） based on five indexes （CPU usage, percentage of CPU kernel mode that occupies CPU time and of message passing waiting time （CPU SW）, code vectorization （VEC）, average of Gflops （Gflops_ AVE）, and peak of Gflops （Gflops_PK））, FAMIL shows excellent computational performance on every Tianhe-2 computing node; （2） considering SYPD and the cost speedup of FAMIL systematically, the optimal Message Passing Interface （MPI） numbers of processors （MNPs） choice appears when FAMIL use 384 and 1536 MNPs for C96 （100 km） and C384 （25 km）, respectively; and （3） FAMIL shows positive scalability with increased threads to drive the model. Considering the fast network speed and acceleration card in the MIC architecture on Tianhe-2, there is still significant room to improve the computational performance of FAMIL.
基金supported by the China-UK-Swiss Adapting to Climate Change in China Project (ACCC)- Climate Sciencethe Public Science and Technology Research Funds Projects of Ocean (Grant No. 201105019-3)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-Q11-04)
文摘The extreme summer precipitation over East China during 1982-2007 was simulated using the LASG/IAP regional climate model CREM(the Climate version of a Regional Eta-coordinate Model).The results show that the probability density functions(PDFs) of precipitation intensities are reasonably simulated,except that the PDFs of light and moderate rain are underestimated and that the PDFs of heavy rain are overestimated.The extreme precipitation amount(R95p) and the percent contribution of extreme precipitation to the total precipitation(R95pt) are also reasonably reproduced by the CREM.However,the R95p and R95pt over most of East China are generally overestimated,while the R95p along the coastal area of South China(SC) is underestimated.The bias of R95pt is consistent with the bias of precipitation intensity on wet days(SDII).The interannual variation for R95p anomalies(PC1) is well simulated,but that of R95pt anomalies(PC2) is poorly simulated.The skill of the model in simulating PC1(PC2) increases(decreases) from north to south.The bias of water vapor transport associated with the 95th percentile of summer daily precipitation(WVTr95) explains well the bias of the simulated extreme precipitation.
基金supported by the Chinese Academy of Sciences(CAS)“Innovation Program”(ZKCX2-SW-210)State Key Project(G2000078502)the National Natural Science Foundation of China(Nos.40231004,40221503,and 40023001).
文摘Coupled ocean-atmospheric general circulation models are the only tools to quantitatively simulate the climate system. Since the end of the 1980s, a group of scientists in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS), have been working to develop a global OGCM and a global coupled ocean-atmosphere general circulation modei (CGCM). Prom the original flux anomaly-coupling modei developed in the beginning of the 1990s to the latest directly-coupling modei, LASG scientists have developed four global coupled GCMs. This study summarizes the development history of these models and describes the third and fourth coupled GCMs and selected applications. Strengths and weaknesses of these models are highlighted.
基金the National Natu-ral Science Foundation of China under Grant No.40023001and No.40233031 and"Innovation Program"under GrantZKCX2-SW-210and the National Key Basic ResearchProject under Grant G200078502.
文摘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.
基金National Natural Science Foundation of China (40233031)
文摘Due to the decrease in grid size associated with the convergence of meridians toward the poles inspherical coordinates, the time steps in many global climate models with finite-difference method are restrictedto be unpleasantly small. To overcome the problem, a reduced grid is introduced to LASG/IAP world oceangeneral circulation models. The reduced grid is implemented successfully in the coarser resolutions versionmodel L30T63 at first. Then, it is carried out in the improved version model LICOM with finer resolutions. Inthe experiment with model L30T63, under time step unchanged though, execution time per single model run isshortened significantly owing to the decrease of grid number and filtering execution in high latitudes. Resultsfrom additional experiments with L30T63 show that the time step of integration can be quadrupled at most inreduced grid with refinement ratio 3. In the experiment with model LICOM and with the model’s original timestep unchanged, the model covered area is extended to the whole globe from its original case with the grid pointof North Pole considered as an isolated island and the results of experiment are shown to be acceptable.
基金supported by the China-UK-Swiss Adapting to Climate Change in China Project (ACCC)-Climate Sciencethe Public Science and Technology Research Funds Projects of Ocean (201105019-3)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW- Q11-04)
文摘The authors examine extreme summer temperatures over East China during 19844004 using a regional climate model named CREM （the Climate version of Regional Eta-coordinate Model）, which was developed by LASG/IAP. The results show that the main features of the extreme summer temperatures over East China are reproduced well by CREM, and the skill for the minimum temperature is higher than that for the maximum tem- perature, especially along the Yangtze-Huai River Valley （YHV）. The simulated extreme temperatures are lower than those of observation, especially for the maximum temperature. The bias of extreme temperatures is consistent with the cold bias of the climatological mean summer surface air temperature. The skill of the model in simulating the interannual variability of extreme temperatures increases from north to south. The simulated interannual variation of the minimum temperature is more reasonable than the maximum temperature. The underestimation of net solar radiation at the surface leads to a cold bias of the climatological mean temperature. Furthermore, the model underestimates the light and moderate rain, while overestimates heavy rain. It causes the simulated minimum temperature more reasonable than the maximum temperature.
文摘基于2010~2019年ERA5单层再分析资料,结合安徽省淮南森林观测站2016年5月1日至2017年4月30日的大气边界层塔(PBL塔)观测资料,驱动陆面模式CLM4.5(Community Land Model Version 4.5),模拟了淮南山地森林下垫面上的陆面过程,并比较分析了不同驱动场对其影响,同时设计了土壤质地对土壤湿度影响的三个模拟试验。结果表明,CLM4.5对淮南森林陆气交换过程表现了较好的模拟性能,PBL塔观测资料驱动的总体模拟效果优于ERA5再分析资料的。在辐射模拟方面,CLM4.5利用ERA5资料和PBL塔观测资料,都很好地模拟了辐射分量,特别是PBL塔观测资料驱动的全年模拟结果与观测相关系数达0.97以上,均方根误差在25.056 W m^(-2)以下。ERA5再分析资料强迫模拟的相关系数略低,但也达到了0.92,均方根误差在29.939 W m^(-2)以下。在土壤温度模拟方面,相关系数都达到0.98以上;土壤湿度模拟的相关系数都在0.86以上,但系统性偏高;对感热通量的模拟全年平均的相关系数分别为0.72和0.78。实测的三层土壤质地加上深层给定的土壤质地的数据对土壤湿度的模拟结果与观测最为接近,土壤质地的准确描述可以大幅提高土壤湿度的模拟。本研究发现ERA5单层再分析资料在淮南森林站精度较好,可以应用于该山地森林区域陆—气交换过程的模拟研究。
基金supported by the Knowledge Innovation Program of Chinese Academy of Sciences(Grant No.ZKCX2-SW-210)the National Natural Science Foundation of China(Grant Nos.40005004,40375029 and 40233031)the Major State Basic Research Development Program of China(973 Program)(Grant No.G200007850-2).
文摘Response of the Atlantic thermohaline circula- tion (THC) to global warming is examined by using the cli- mate system model developed at IAP/LASG. The evidence indicates that the gradually warming climate associated with the increased atmospheric carbon dioxide leads to a warmer and fresher sea surface water at the high latitudes of the North Atlantic Ocean, which prevents the down-welling of the surface water. The succedent reduction of the pole-to- equator meridional potential density gradient finally results in the decrease of the THC in intensity. When the atmos- pheric carbon dioxide is doubled, the maximum value of the Atlantic THC decreases approximately by 8%. The associ- ated poleward oceanic heat transport also becomes weaker. This kind of THC weakening centralizes mainly in the northern part of the North Atlantic basin, indicating briefly a local scale adjustment rather than a loop oscillation with the whole Atlantic “conveyor belt” decelerating.
