Identification and extraction length of dry spells in arid and semi-arid regions is very important. Thus, the use of climate change prediction models for study the behavior of the climatic parameters in the future tim...Identification and extraction length of dry spells in arid and semi-arid regions is very important. Thus, the use of climate change prediction models for study the behavior of the climatic parameters in the future time is inevitable. With recognition of the spatial and temporal behavior variables such as precipitation, we can prevent from destructive effects. In this research, the performance of Atmosphere-Ocean General Circulation Models (AOGCMs) was evaluated for simulation length of dry spells in the south-western area of Iran. The results show that the length of dry spell is relatively decreased in cold seasons (autumn and winter) and increased in the warm season (spring and summer) in both A2 and B2 Scenarios. The length of the dry spell on monthly scale for scenario A2 is 6% (equivalent to 2 days) and for scenario B2 is 9 percent (approximately 2.4 day) increased compared to the baseline period. For assess the uncertainty, AOGCMs were weighting. The results show that the best model for simulation of dry spells is HADCM3 and GFCM2.1, because the results have a less error. On the other hand, NCCCSM have the lowest weight for simulation dry spells in both scenarios.展开更多
The summer mean water vapor transport （WVT） and cross-equatorial flow （CEF） over the Asian- Australian monsoon region simulated by 22 coupled atmospheric-oceanic general circulation models （AOGCMs） from the Worl...The summer mean water vapor transport （WVT） and cross-equatorial flow （CEF） over the Asian- Australian monsoon region simulated by 22 coupled atmospheric-oceanic general circulation models （AOGCMs） from the World Climate Research Programme＇s Coupled Model Intercomparison Project Phase 5 （CMIP5） were evaluated. Based on climatology of the twentieth-century simulations, most of models have a reason- ably realistic representation of summer monsoon WVT characterized by southeast water vapor conveyor belt over the South Indian Ocean and southwest belt from the Arabian Sea to the East Asian. The correlation coefficients between NCEP reanalysis and simulations of BCC-CSMI-1, BNU-ESM, CanESM2, FGOALS-s2, MIROC4h and MPI-ESM-LR are up to 0.8. The simulated CEF depicted by the meridional wind along the equator includes the Somali jet and eastern CEF in low atmosphere and the reverse circulation in upper atmosphere, which were generally consistent with NCEP reanalysis. Multi-model ensemble means （MME） can reproduce more reasonable climatological features in spatial distribution both of WVT and CEF. Ten models with more reasonable WVT simulations were selected for future projection studies, including BCC- CSMI-1, BNU-ESM, CanESM2, CCSM4, FGOALS-s2, FIO-ESM, GFDL-ESM2G, MRIOCS, MPI-ESM-LR and NorESM-1M. Analysis based on the future projection experiments in RCP （Representative Concentra- tion Pathway） 2.6, RCP4.5, RCP6 and RCP8.5 show that the global warming forced by different RCP scenarios will results in enhanced WVT over the Indian area and the west Pacific and weaken WVT in the low latitudes of tropical Indian Ocean.展开更多
The Argo(Array for Real-time Geostrophic Oceanography) data from 1998 to 2003 were used in the Beijing Climate Center-Global Ocean Data Assimilation System(BCC-GODAS). The results show that the utilization of Argo glo...The Argo(Array for Real-time Geostrophic Oceanography) data from 1998 to 2003 were used in the Beijing Climate Center-Global Ocean Data Assimilation System(BCC-GODAS). The results show that the utilization of Argo global ocean data in BCC-GODAS brings about remarkable improvements in assimilation effects. The assimilated sea surface temperature(SST) of BCC-GODAS can well represent the climatological states of observational data. Comparison experiments based on a global coupled atmosphere-ocean general circulation model(AOCGM) were conducted for exploring the roles of ocean data assimilation system with or without Argo data in improving the climate predictability of rainfall in boreal summer. Firstly, the global ocean data assimilation system BCC-GODAS was used to obtain ocean assimilation data under the conditions with or without Argo data. Then, the global coupled atmosphere-ocean general circulation model(AOCGM) was utilized to do hindcast experiments with the two sets of the assimilation data as initial oceanic fields. The simulated results demonstrate that the seasonal predictability of rainfall in boreal summer, particularly in China, increases greatly when initial oceanic conditions with Argo data are utilized. The distribution of summer rainfall in China hindcast by the AOGCM under the condition when Argo data are used is more in accordance with observation than that when no Agro data are used. The area of positive correlation between hindcast and observation enlarges and the hindcast skill of rainfall over China in summer improves significantly when Argo data are used.展开更多
Using NCC/IAP T63 coupled atmosphere-ocean general circulation model （AOGCM）, two 20-yr integrations were processed, and their ability to simulate cloud and radiation was analysed in detail. The results show that th...Using NCC/IAP T63 coupled atmosphere-ocean general circulation model （AOGCM）, two 20-yr integrations were processed, and their ability to simulate cloud and radiation was analysed in detail. The results show that the model can simulate the basic distribution of cloud cover, and however, obvious differences still exist compared with ISCCP satellite data and ERA reanalysis data. The simulated cloud cover is less in general, especially the abnormal low values in some regions of ocean. By improving the cloud cover scheme, simulated cloud cover in the eastern Pacific and Atlantic, summer hemisphere＇s oceans from subtropical to mid-latitude is considerably improved. But in the tropical Indian Ocean and West Pacific the cloud cover difference is still evident, mainly due to the deficiency of high cloud simulation in these regions resulting from deep cumulus convection. In terms of the analysis on radiation and cloud radiative forcing, we find that simulation on long wave radiation is better than short wave radiation. The simulation error of short wave radiation is caused mostly by the simulation difference in short wave radiative forcing, sea ice, and snow cover, and also by not involving aerosol＇s effect. The simulation error of long wave radiation is mainly resulting from deficiency in simulating cloud cover and underlying surface temperature. Corresponding to improvement of cloud cover, the simulated radiation （especially short wave radiation） in eastern oceans, summer hemisphere＇s oceans from subtropical to mid-latitude is remarkably improved. This also brings obvious improvement to net radiation in these regions.展开更多
文摘Identification and extraction length of dry spells in arid and semi-arid regions is very important. Thus, the use of climate change prediction models for study the behavior of the climatic parameters in the future time is inevitable. With recognition of the spatial and temporal behavior variables such as precipitation, we can prevent from destructive effects. In this research, the performance of Atmosphere-Ocean General Circulation Models (AOGCMs) was evaluated for simulation length of dry spells in the south-western area of Iran. The results show that the length of dry spell is relatively decreased in cold seasons (autumn and winter) and increased in the warm season (spring and summer) in both A2 and B2 Scenarios. The length of the dry spell on monthly scale for scenario A2 is 6% (equivalent to 2 days) and for scenario B2 is 9 percent (approximately 2.4 day) increased compared to the baseline period. For assess the uncertainty, AOGCMs were weighting. The results show that the best model for simulation of dry spells is HADCM3 and GFCM2.1, because the results have a less error. On the other hand, NCCCSM have the lowest weight for simulation dry spells in both scenarios.
基金supported by the National Basic Research Program of China(973 Program)under Grant 2010CB950500 and 2010CB950304the Scientific Research Foundation of the First Institute of Oceanography,State Oceanic Administration(Grant No.GY02-2001G26)the National Natural Science Foundation of China under Grant No.41206026
文摘The summer mean water vapor transport （WVT） and cross-equatorial flow （CEF） over the Asian- Australian monsoon region simulated by 22 coupled atmospheric-oceanic general circulation models （AOGCMs） from the World Climate Research Programme＇s Coupled Model Intercomparison Project Phase 5 （CMIP5） were evaluated. Based on climatology of the twentieth-century simulations, most of models have a reason- ably realistic representation of summer monsoon WVT characterized by southeast water vapor conveyor belt over the South Indian Ocean and southwest belt from the Arabian Sea to the East Asian. The correlation coefficients between NCEP reanalysis and simulations of BCC-CSMI-1, BNU-ESM, CanESM2, FGOALS-s2, MIROC4h and MPI-ESM-LR are up to 0.8. The simulated CEF depicted by the meridional wind along the equator includes the Somali jet and eastern CEF in low atmosphere and the reverse circulation in upper atmosphere, which were generally consistent with NCEP reanalysis. Multi-model ensemble means （MME） can reproduce more reasonable climatological features in spatial distribution both of WVT and CEF. Ten models with more reasonable WVT simulations were selected for future projection studies, including BCC- CSMI-1, BNU-ESM, CanESM2, CCSM4, FGOALS-s2, FIO-ESM, GFDL-ESM2G, MRIOCS, MPI-ESM-LR and NorESM-1M. Analysis based on the future projection experiments in RCP （Representative Concentra- tion Pathway） 2.6, RCP4.5, RCP6 and RCP8.5 show that the global warming forced by different RCP scenarios will results in enhanced WVT over the Indian area and the west Pacific and weaken WVT in the low latitudes of tropical Indian Ocean.
基金National Program on Key Basic Research Project of China(2012CB955203,2013CB430202)National Natural Science Foundation of China(40231014,41175065)+1 种基金China Meteorological Administration R&D Special Fund for Public Welfare(meteorology)(GYHY201306021)National High Technology Research and Development Program of China(2010AA012404)
文摘The Argo(Array for Real-time Geostrophic Oceanography) data from 1998 to 2003 were used in the Beijing Climate Center-Global Ocean Data Assimilation System(BCC-GODAS). The results show that the utilization of Argo global ocean data in BCC-GODAS brings about remarkable improvements in assimilation effects. The assimilated sea surface temperature(SST) of BCC-GODAS can well represent the climatological states of observational data. Comparison experiments based on a global coupled atmosphere-ocean general circulation model(AOCGM) were conducted for exploring the roles of ocean data assimilation system with or without Argo data in improving the climate predictability of rainfall in boreal summer. Firstly, the global ocean data assimilation system BCC-GODAS was used to obtain ocean assimilation data under the conditions with or without Argo data. Then, the global coupled atmosphere-ocean general circulation model(AOCGM) was utilized to do hindcast experiments with the two sets of the assimilation data as initial oceanic fields. The simulated results demonstrate that the seasonal predictability of rainfall in boreal summer, particularly in China, increases greatly when initial oceanic conditions with Argo data are utilized. The distribution of summer rainfall in China hindcast by the AOGCM under the condition when Argo data are used is more in accordance with observation than that when no Agro data are used. The area of positive correlation between hindcast and observation enlarges and the hindcast skill of rainfall over China in summer improves significantly when Argo data are used.
基金Supported by the Ministry of Science and Technology of China Project under Grant No.2001BA611B-01.
文摘Using NCC/IAP T63 coupled atmosphere-ocean general circulation model （AOGCM）, two 20-yr integrations were processed, and their ability to simulate cloud and radiation was analysed in detail. The results show that the model can simulate the basic distribution of cloud cover, and however, obvious differences still exist compared with ISCCP satellite data and ERA reanalysis data. The simulated cloud cover is less in general, especially the abnormal low values in some regions of ocean. By improving the cloud cover scheme, simulated cloud cover in the eastern Pacific and Atlantic, summer hemisphere＇s oceans from subtropical to mid-latitude is considerably improved. But in the tropical Indian Ocean and West Pacific the cloud cover difference is still evident, mainly due to the deficiency of high cloud simulation in these regions resulting from deep cumulus convection. In terms of the analysis on radiation and cloud radiative forcing, we find that simulation on long wave radiation is better than short wave radiation. The simulation error of short wave radiation is caused mostly by the simulation difference in short wave radiative forcing, sea ice, and snow cover, and also by not involving aerosol＇s effect. The simulation error of long wave radiation is mainly resulting from deficiency in simulating cloud cover and underlying surface temperature. Corresponding to improvement of cloud cover, the simulated radiation （especially short wave radiation） in eastern oceans, summer hemisphere＇s oceans from subtropical to mid-latitude is remarkably improved. This also brings obvious improvement to net radiation in these regions.
