Using the low-resolution （T31, equivalent to 3.75°× 3.75°） version of the Community Earth System Model （CESM） from the National Center for Atmospheric Research （NCAR）, a global climate simulation ...Using the low-resolution （T31, equivalent to 3.75°× 3.75°） version of the Community Earth System Model （CESM） from the National Center for Atmospheric Research （NCAR）, a global climate simulation was carried out with fixed external forcing factors （1850 Common Era. （C.E.） conditions） for the past 2000 years. Based on the simulated results, spatio-temporal structures of surface air temperature, precipitation and internal variability, such as the E1 Nifio-Southem Oscillation （ENSO）, the Atlantic Multi-decadal Oscilla- tion （AMO）, the Pacific Decadal Oscillation （PDO）, and the North Atlantic Oscillation （NAO）, were compared with reanalysis datasets to evaluate the model performance. The results are as follows： 1） CESM showed a good performance in the long-term simulation and no significant climate drift over the past 2000 years; 2） climatological patterns of global and regional climate changes simulated by the CESM were reasonable compared with the reanalysis datasets; and 3） the CESM simulated internal natural variability of the climate system performs very well. The model not only reproduced the periodicity of ENSO, AMO and PDO events but also the 3-8 years vari- ability of the ENSO. The spatial distribution of the CESM-simulated NAO was also similar to the observed. However, because of weaker total irradiation and greenhouse gas concentration forcing in the simulation than the present, the model performances had some differences from the observations. Generally, the CESM showed a good performance in simulating the global climate and internal natu- ral variability of the climate system. This paves the way for other forced climate simulations for the past 2000 years by using the CESM.展开更多
The role of sea surface temperature(SST)variability in the pre-monsoonal(April to July)intraseasonal oscillation(ISO)over the South China Sea(SCS)is investigated using the Community Earth System Model Version 2(CESM2)...The role of sea surface temperature(SST)variability in the pre-monsoonal(April to July)intraseasonal oscillation(ISO)over the South China Sea(SCS)is investigated using the Community Earth System Model Version 2(CESM2).An Atmospheric Model Intercomparison Project(AMIP)simulation forced by daily sea surface temperatures(SSTs)derived from a parallel coupled general circulation model(CGCM)run was compared with observations and the mother coupled simulation.In the coupled model,the SST warming leads the peak convection about 1/4 period as in observations.The paralell uncoupled model fails to simulate this phase relationship,implying the importance of air-sea coupling in reproducing realistic ISO.Due to the near-quadrature phase relationship between SST and precipitation ISOs during the ISO events,it is difficult to distinguish the active/passive role of SST from observations alone.Significant correlation in intraseasonal precipitation between the daily SST-forced AMIP and mother CGCM runs indicates that SST plays a role in driving the atmospheric ISO.展开更多
In this study,the mechanisms underlying the decadal variability of late spring precipitation in South China are investigated by using the latest Community Earth System Model version 1 （CESM1）.We aim to unravel the e...In this study,the mechanisms underlying the decadal variability of late spring precipitation in South China are investigated by using the latest Community Earth System Model version 1 （CESM1）.We aim to unravel the effects of different climate forcing agents such as aerosols and greenhouse gases （GHGs） on the decadal variation of precipitation,based on transient experiments from pre-industry （for year 1850） to present-day （for year 2000）.Our results reveal that：（1） CESM1 can reproduce the climatological features of atmospheric circulation and precipitation for the late spring in South China; （2） only simulations including the forcing of anthropogenic aerosols can reproduce the observed decreasing trend of late spring precipitation from 1950-2000 in South China; （3） aerosols affect the decadal change of precipitation mainly by altering the large-scale atmospheric circulation,and to a less extent by increasing the lower-tropospheric stability to inhibit the convective precipitation; and （4） in comparison,other climate forcing agents such as GHGs have much smaller effects on the decadal change of spring precipitation in South China.展开更多
Temperature inversions are frequently observed in the boundary layer and lower troposphere of polar regions.Future variations of the low-level temperature inversions in these regions,especially the Antarctic,are still...Temperature inversions are frequently observed in the boundary layer and lower troposphere of polar regions.Future variations of the low-level temperature inversions in these regions,especially the Antarctic,are still poorly understood.Due to the scarcity of observations in the Antarctic,reanalysis data and numerical simulations are often used in the study of Antarctic climate change.Based on ERA-Interim,ERA5,JRA-55,and NCEP-NCAR reanalysis products,this study examines temporal and spatial variations of Antarctic inversion depth in austral autumn and winter during 1979-2020.Deeper inversions are found to occur over the high plateau areas of the Antarctic continent.Based on the Mann-Kendall test,ERA-Interim and ERA5 data reveal that the Antarctic inversion depth in austral autumn and winter increased during 1992-2007,roughly maintained afterwards,and then significantly decreased since around 2016.The decrease trend is more obvious in the last two months of winter.Overall,JRA-55 better represents the spatial distribution of inversion depth,and ERA-Interim has better interannual variability.The Community Earth System Model Large Ensemble(CESM-LE)30-member simulations in 1979-2005 were first verified against JRA-55,showing reasonable consistency,and were then used to project the future changes of Antarctic low-level inversion depth over 2031-2050 under RCP8.5.The CESM-LE projection results reveal that the temperature inversion will shallow in the Antarctic at the end of the 21st century,and the decrease in depth in autumn will be more pronounced than that in winter.In particular,the temperature inversion will weaken over the ice-free ocean,while it will remain stable over the ice sheet,showing certain spatial heterogeneity and seasonal dependence on the underlying cryospheric surface conditions.In addition,the decrease of inversion depth is found closely linked with the reduction in sea ice,suggesting the strong effect of global warming on the thermal structure change of the Antarctic.展开更多
基金Under the auspices of National Basic Research Program of China(No.2010CB950102)Strategic and Special Frontier Project of Science and Technology of Chinese Academy of Sciences(No.XDA05080800)+3 种基金National Natural Science Foundation of China(No.41371209,41420104002)Special Research Fund for Doctoral Discipline of Higher Education Institutions(No.20133207110015)Natural Science Foundation of Jiangsu Higher Education Institutions(No.14KJA170002)Priority Academic Program Development of Jiangsu Higher Education Institutions(No.164320H101)
文摘Using the low-resolution （T31, equivalent to 3.75°× 3.75°） version of the Community Earth System Model （CESM） from the National Center for Atmospheric Research （NCAR）, a global climate simulation was carried out with fixed external forcing factors （1850 Common Era. （C.E.） conditions） for the past 2000 years. Based on the simulated results, spatio-temporal structures of surface air temperature, precipitation and internal variability, such as the E1 Nifio-Southem Oscillation （ENSO）, the Atlantic Multi-decadal Oscilla- tion （AMO）, the Pacific Decadal Oscillation （PDO）, and the North Atlantic Oscillation （NAO）, were compared with reanalysis datasets to evaluate the model performance. The results are as follows： 1） CESM showed a good performance in the long-term simulation and no significant climate drift over the past 2000 years; 2） climatological patterns of global and regional climate changes simulated by the CESM were reasonable compared with the reanalysis datasets; and 3） the CESM simulated internal natural variability of the climate system performs very well. The model not only reproduced the periodicity of ENSO, AMO and PDO events but also the 3-8 years vari- ability of the ENSO. The spatial distribution of the CESM-simulated NAO was also similar to the observed. However, because of weaker total irradiation and greenhouse gas concentration forcing in the simulation than the present, the model performances had some differences from the observations. Generally, the CESM showed a good performance in simulating the global climate and internal natu- ral variability of the climate system. This paves the way for other forced climate simulations for the past 2000 years by using the CESM.
基金Supported by the National Natural Science Foundation of China(No.42090042)the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.2019BT02H594)the Chinese Academy of Sciences(Nos.XDB42010304,133244KYSB20190031,183311KYSB20200015,SCSIO202201)。
文摘The role of sea surface temperature(SST)variability in the pre-monsoonal(April to July)intraseasonal oscillation(ISO)over the South China Sea(SCS)is investigated using the Community Earth System Model Version 2(CESM2).An Atmospheric Model Intercomparison Project(AMIP)simulation forced by daily sea surface temperatures(SSTs)derived from a parallel coupled general circulation model(CGCM)run was compared with observations and the mother coupled simulation.In the coupled model,the SST warming leads the peak convection about 1/4 period as in observations.The paralell uncoupled model fails to simulate this phase relationship,implying the importance of air-sea coupling in reproducing realistic ISO.Due to the near-quadrature phase relationship between SST and precipitation ISOs during the ISO events,it is difficult to distinguish the active/passive role of SST from observations alone.Significant correlation in intraseasonal precipitation between the daily SST-forced AMIP and mother CGCM runs indicates that SST plays a role in driving the atmospheric ISO.
基金Supported by the U.S.Department of Energy(DOE),Ofce of Science(BER)Earth System Modeling Program
文摘In this study,the mechanisms underlying the decadal variability of late spring precipitation in South China are investigated by using the latest Community Earth System Model version 1 （CESM1）.We aim to unravel the effects of different climate forcing agents such as aerosols and greenhouse gases （GHGs） on the decadal variation of precipitation,based on transient experiments from pre-industry （for year 1850） to present-day （for year 2000）.Our results reveal that：（1） CESM1 can reproduce the climatological features of atmospheric circulation and precipitation for the late spring in South China; （2） only simulations including the forcing of anthropogenic aerosols can reproduce the observed decreasing trend of late spring precipitation from 1950-2000 in South China; （3） aerosols affect the decadal change of precipitation mainly by altering the large-scale atmospheric circulation,and to a less extent by increasing the lower-tropospheric stability to inhibit the convective precipitation; and （4） in comparison,other climate forcing agents such as GHGs have much smaller effects on the decadal change of spring precipitation in South China.
基金Supported by the National Natural Science Foundation of China(42122047)National Key Research and Development Program of China(2021YFC2802504)Basic Fund of Chinese Academy of Meteorological Sciences(2021Z006).
文摘Temperature inversions are frequently observed in the boundary layer and lower troposphere of polar regions.Future variations of the low-level temperature inversions in these regions,especially the Antarctic,are still poorly understood.Due to the scarcity of observations in the Antarctic,reanalysis data and numerical simulations are often used in the study of Antarctic climate change.Based on ERA-Interim,ERA5,JRA-55,and NCEP-NCAR reanalysis products,this study examines temporal and spatial variations of Antarctic inversion depth in austral autumn and winter during 1979-2020.Deeper inversions are found to occur over the high plateau areas of the Antarctic continent.Based on the Mann-Kendall test,ERA-Interim and ERA5 data reveal that the Antarctic inversion depth in austral autumn and winter increased during 1992-2007,roughly maintained afterwards,and then significantly decreased since around 2016.The decrease trend is more obvious in the last two months of winter.Overall,JRA-55 better represents the spatial distribution of inversion depth,and ERA-Interim has better interannual variability.The Community Earth System Model Large Ensemble(CESM-LE)30-member simulations in 1979-2005 were first verified against JRA-55,showing reasonable consistency,and were then used to project the future changes of Antarctic low-level inversion depth over 2031-2050 under RCP8.5.The CESM-LE projection results reveal that the temperature inversion will shallow in the Antarctic at the end of the 21st century,and the decrease in depth in autumn will be more pronounced than that in winter.In particular,the temperature inversion will weaken over the ice-free ocean,while it will remain stable over the ice sheet,showing certain spatial heterogeneity and seasonal dependence on the underlying cryospheric surface conditions.In addition,the decrease of inversion depth is found closely linked with the reduction in sea ice,suggesting the strong effect of global warming on the thermal structure change of the Antarctic.
