Evaluation And Projection Of The CMIP5 Models In Simulating The Change Of The East Asian Winter Monsoon

As one of the major tools to better understand the phenomenon of climate system and to project the future climate change,global climate models have been widely used in present researches of numerous fields.However due to the complexity of the climate system,the models' ability to simulate the climate system is far from perfect.Thus it is necessary to evaluate the performance of these models comprehensively and systematically,so as to provide reference and suggestions not only for model improvement,but for the researchers from different fields who will use the results from climate models.Based on the observation and the simulations of 44 models archived in the Coupled Model Intercomparison Project phase 5(CMIP5),this study evaluated their performance in modeling the East Asian winter monsoon(EAWM),associated atmospheric circulation and temperature,and indices measure the strength of the EAWM,and the features of the anomalies in atmospheric circulation and temperature related to the four indices.Then the models with rather better performances are selected to project the future change of the EAWM.The CMIP5 models have the best capacity to simulate the surface air temperature and 500 hPa geopotential height,followed by the 200 hPa zonal wind and then the sea level pressure and the 850 hPa meridional wind of the East Asia.As for the climatology of atmospheric circulation and temperature,the multimodel ensemble(MME)can well capture the spatial distribution of the Siberian high,the Aleutian low,the prevailing northerly wind over East Asia in the lower troposphere,the East Asian major trough in the middle troposphere,and the East Asian jet stream in the upper troposphere as well as the surface air temperature,but the simulated circulation is generally weaker than the magnitude of observation.Four indices named IJhun,IWang,ICui and IGuo that were defined respectively by Jhun and Lee(2004)from 300 hPa zonal winds,by Wang and Jiang(2004)from 850 hPa winds,by Cui and Sun(1999)from 500 hPa geopotential height,and by Guo(1994)from seal level pressure were selected to represent the EAWM intensity.The results show that: the features of the anomalies in EAWM related different indices,which are simulated by MME,are distinct.The best one is that related IJhun.Not only the intensity,but the domain of change of each variation is consistent with observation.The results of other three indices are similar,all of them show the difference with the observation in 200 hPa zonal wind.The projection show that: in the late twenty-first century,the major change of the EAWM is that,the Aleutian low become weak and move toward north,the anomaly of anticyclonic circulation for 850 hPa wind appear in the area of the west Pacific,the weaker East Asian major trough,the stronger East Asian westerly jet stream and the higher surface air temperature.The results of projection about indices are different,IJhun and ICui show that the EAWM would be weaker,another two indices show the EAWM would be stronger.Comparing with the features of present,the abnormal amplitude of EAWM in the future would be reduce.