This analysis of the multi-model aerosol optical depth (AOD) in eastern China using the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) datasets shows that the global models underestimate the ...This analysis of the multi-model aerosol optical depth (AOD) in eastern China using the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) datasets shows that the global models underestimate the AOD by 33% and 44% in southern and northern China, respectively, and decrease the relative humidity (RH) of the air in the surface layer to 71%–80%, which is less than the RH of 77%–92% in reanalysis meteorological datasets. This indicates that the low biases in the RH partially account for the errors in the AOD. The AOD is recalculated based on the model aerosol concentrations and the reanalysis humidity data. Improving the mean value of the RH increases the multi-model annual mean AOD by 45% in southern China and by 33% in June–August in northern China. This method of improving the AOD is successful in most of the ACCMIP models, but it is unlikely to be successful in GISS-E2-R, in which the plot of its AOD efficiency against RH strongly deviates from the rest of the models. The effect of the improvement in the modeled RH on the AOD depends on the concentration of aerosols. The shape error in the frequency distribution of the RH is likely to be more important than the error in the mean value of the RH, but this requires further research.展开更多
Experimental outputs of 11 Atmospheric Model Intercomparison Project （AMIP） models from phase 5 of the Coupled Model Intercomparison Project （CMIP5） are analyzed to assess the atmospheric circulation anomaly over ...Experimental outputs of 11 Atmospheric Model Intercomparison Project （AMIP） models from phase 5 of the Coupled Model Intercomparison Project （CMIP5） are analyzed to assess the atmospheric circulation anomaly over Northern Hemisphere induced by the anomalous rainfall over tropical Pacific and Indian Ocean during boreal winter.The analysis shows that the main features of the interannual variation of tropical rainfall anomalies,especially over the Central Pacific （CP） （5°S-5°N,175°E-135°W） and Indo-western Pacific （IWP） （20°S-20°N,110°-150°E） are well captured in all the CMIP5/AMIP models.For the IWP and western Indian Ocean （WIO） （10°S-10°N,45°-75°E）,the anomalous rainfall is weaker in the 11 CMIP5/AMIP models than in the observation.During El Ni（n）o/La Ni（n）a mature phases in boreal winter,consistent with observations,there are geopotential height anomalies known as the Pacific North American （PNA） pattern and Indo-western Pacific and East Asia （IWPEA） pattern in the upper troposphere,and the northwestern Pacific anticyclone （cyclone） （NWPA） in the lower troposphere in the models.Comparison between the models and observations shows that the ability to simulate the PNA and NWPA pattern depends on the ability to simulate the anomalous rainfall over the CP,while the ability to simulate the IWPEA pattern is related to the ability to simulate the rainfall anomaly in the IWP and WIO,as the SST anomaly is same in AMIP experiments.It is found that the tropical rainfall anomaly is important in modeling the impact of the tropical Indo-Pacific Ocean on the extratropical atmospheric circulation anomaly.展开更多
E1 Nifio-Southem Oscillation （ENSO） events significantly affect the year-by-year variations of the East Asian winter monsoon （EAWM）. However, the effect of La Nifia events on the EAWM is not a mirror image of that...E1 Nifio-Southem Oscillation （ENSO） events significantly affect the year-by-year variations of the East Asian winter monsoon （EAWM）. However, the effect of La Nifia events on the EAWM is not a mirror image of that of E1 Nifio events. Although the EAWM becomes generally weaker during El Nifio events and stronger during La Nifia winters, the enhanced precipitation over the southeastern China and warmer surface air temperature along the East Asian coastline during E1 Nifio years are more significant. These asymmetric effects are caused by the asymmetric longitudinal positions of the western North Pacific （WNP） anticyclone during El Nifio events and the WNP cyclone during La Nifia events; specifically, the center of the WNP cyclone during La Nifia events is westward-shifted relat- ive to its El Nifio counterpart. This central-position shift results from the longitudinal shift of remote E1 Nifio and La Nifia anomalous heating, and asymmetry in the amplitude of local sea surface temperature anomalies over the WNP. However, such asymmetric effects of ENSO on the EAWM are barely reproduced by the atmospheric models of Phase 5 of the Coupled Model Intercomparison Project （CMIP5）, although the spatial patterns of anomalous circula- tions are reasonably reproduced. The major limitation of the CMIP5 models is an overestimation of the anomalous WNP anticyclone/cyclone, which leads to stronger EAWM rainfall responses. The overestimated latent heat flux an- omalies near the South China Sea and the northern WNP might be a key factor behind the overestimated anomalous circulations.展开更多
The Chinese Academy of Meteorological Sciences(CAMS)has been devoted to developing a climate system model(CSM)to meet demand for climate simulation and prediction for the East Asian region.In this study,we evaluated t...The Chinese Academy of Meteorological Sciences(CAMS)has been devoted to developing a climate system model(CSM)to meet demand for climate simulation and prediction for the East Asian region.In this study,we evaluated the performance of CAMS-CSM in regard to sensible heat flux(H),latent heat flux(LE),surface temperature,soil moisture,and snow depth,focusing on the Atmospheric Model Intercomparison Project experiment,with the aim of participating in the Coupled Model Intercomparison Project phase 6.We systematically assessed the simulation results achieved by CAMS-CSM for these variables against various reference products and ground observations,including the FLUXNET model tree ensembles H and LE data,Climate Prediction Center soil moisture data,snow depth climatology data,and Chinese ground observations of snow depth and winter surface temperature.We compared these results with data from the ECMWF Interim reanalysis(ERA-Interim)and Global Land Data Assimilation System(GLDAS).Our results indicated that CAMS-CSM simulations were better than or comparable to ERA-Interim reanalysis for snow depth and winter surface temperature at regional scales,but slightly worse when simulating total column soil moisture.The root-mean-square differences of H in CAMS-CSM were all greater than those from the ERA-Interim reanalysis,but less than or comparable to those from GLDAS.The spatial correlations for H in CAMS-CSM were the lowest in nearly all regions,except for North America.CAMS-CSM LE produced the lowest bias in Siberia,North America,and South America,but with the lowest spatial correlation coefficients.Therefore,there are still scopes for improving H and LE simulations in CAMS-CSM,particularly for LE.展开更多
基金jointly supported by the National Key Research and Development Program of China [grant number2016YFE0201400]the Basic Research Program of the State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry,Institute of Atmospheric Physics,Chinese Academy of Sciences [grant number 7-082999]
文摘This analysis of the multi-model aerosol optical depth (AOD) in eastern China using the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) datasets shows that the global models underestimate the AOD by 33% and 44% in southern and northern China, respectively, and decrease the relative humidity (RH) of the air in the surface layer to 71%–80%, which is less than the RH of 77%–92% in reanalysis meteorological datasets. This indicates that the low biases in the RH partially account for the errors in the AOD. The AOD is recalculated based on the model aerosol concentrations and the reanalysis humidity data. Improving the mean value of the RH increases the multi-model annual mean AOD by 45% in southern China and by 33% in June–August in northern China. This method of improving the AOD is successful in most of the ACCMIP models, but it is unlikely to be successful in GISS-E2-R, in which the plot of its AOD efficiency against RH strongly deviates from the rest of the models. The effect of the improvement in the modeled RH on the AOD depends on the concentration of aerosols. The shape error in the frequency distribution of the RH is likely to be more important than the error in the mean value of the RH, but this requires further research.
基金supported by the Ministry of Science and Technology of China (National Basic Research Program of China Grant No. 2012CB955602)the National Natural Science Foundation of China (Grant Nos. 41176006 and 41221063)
文摘Experimental outputs of 11 Atmospheric Model Intercomparison Project （AMIP） models from phase 5 of the Coupled Model Intercomparison Project （CMIP5） are analyzed to assess the atmospheric circulation anomaly over Northern Hemisphere induced by the anomalous rainfall over tropical Pacific and Indian Ocean during boreal winter.The analysis shows that the main features of the interannual variation of tropical rainfall anomalies,especially over the Central Pacific （CP） （5°S-5°N,175°E-135°W） and Indo-western Pacific （IWP） （20°S-20°N,110°-150°E） are well captured in all the CMIP5/AMIP models.For the IWP and western Indian Ocean （WIO） （10°S-10°N,45°-75°E）,the anomalous rainfall is weaker in the 11 CMIP5/AMIP models than in the observation.During El Ni（n）o/La Ni（n）a mature phases in boreal winter,consistent with observations,there are geopotential height anomalies known as the Pacific North American （PNA） pattern and Indo-western Pacific and East Asia （IWPEA） pattern in the upper troposphere,and the northwestern Pacific anticyclone （cyclone） （NWPA） in the lower troposphere in the models.Comparison between the models and observations shows that the ability to simulate the PNA and NWPA pattern depends on the ability to simulate the anomalous rainfall over the CP,while the ability to simulate the IWPEA pattern is related to the ability to simulate the rainfall anomaly in the IWP and WIO,as the SST anomaly is same in AMIP experiments.It is found that the tropical rainfall anomaly is important in modeling the impact of the tropical Indo-Pacific Ocean on the extratropical atmospheric circulation anomaly.
基金Supported by the National Natural Science Foundation of China(41405103 and 41125017)China Meteorological Administration Special Public Welfare Research Fund(GYHY201506012)Joint Center for Global Change Studies(105019)
文摘E1 Nifio-Southem Oscillation （ENSO） events significantly affect the year-by-year variations of the East Asian winter monsoon （EAWM）. However, the effect of La Nifia events on the EAWM is not a mirror image of that of E1 Nifio events. Although the EAWM becomes generally weaker during El Nifio events and stronger during La Nifia winters, the enhanced precipitation over the southeastern China and warmer surface air temperature along the East Asian coastline during E1 Nifio years are more significant. These asymmetric effects are caused by the asymmetric longitudinal positions of the western North Pacific （WNP） anticyclone during El Nifio events and the WNP cyclone during La Nifia events; specifically, the center of the WNP cyclone during La Nifia events is westward-shifted relat- ive to its El Nifio counterpart. This central-position shift results from the longitudinal shift of remote E1 Nifio and La Nifia anomalous heating, and asymmetry in the amplitude of local sea surface temperature anomalies over the WNP. However, such asymmetric effects of ENSO on the EAWM are barely reproduced by the atmospheric models of Phase 5 of the Coupled Model Intercomparison Project （CMIP5）, although the spatial patterns of anomalous circula- tions are reasonably reproduced. The major limitation of the CMIP5 models is an overestimation of the anomalous WNP anticyclone/cyclone, which leads to stronger EAWM rainfall responses. The overestimated latent heat flux an- omalies near the South China Sea and the northern WNP might be a key factor behind the overestimated anomalous circulations.
基金Supported by the National Natural Science Foundation for Young Scientists of China(41505010 and 41605073)Basic Research Special Project of Chinese Academy of Meteorological Sciences(2017Y015 and 2017Y008)
文摘The Chinese Academy of Meteorological Sciences(CAMS)has been devoted to developing a climate system model(CSM)to meet demand for climate simulation and prediction for the East Asian region.In this study,we evaluated the performance of CAMS-CSM in regard to sensible heat flux(H),latent heat flux(LE),surface temperature,soil moisture,and snow depth,focusing on the Atmospheric Model Intercomparison Project experiment,with the aim of participating in the Coupled Model Intercomparison Project phase 6.We systematically assessed the simulation results achieved by CAMS-CSM for these variables against various reference products and ground observations,including the FLUXNET model tree ensembles H and LE data,Climate Prediction Center soil moisture data,snow depth climatology data,and Chinese ground observations of snow depth and winter surface temperature.We compared these results with data from the ECMWF Interim reanalysis(ERA-Interim)and Global Land Data Assimilation System(GLDAS).Our results indicated that CAMS-CSM simulations were better than or comparable to ERA-Interim reanalysis for snow depth and winter surface temperature at regional scales,but slightly worse when simulating total column soil moisture.The root-mean-square differences of H in CAMS-CSM were all greater than those from the ERA-Interim reanalysis,but less than or comparable to those from GLDAS.The spatial correlations for H in CAMS-CSM were the lowest in nearly all regions,except for North America.CAMS-CSM LE produced the lowest bias in Siberia,North America,and South America,but with the lowest spatial correlation coefficients.Therefore,there are still scopes for improving H and LE simulations in CAMS-CSM,particularly for LE.
