Research On The Response Mechanism Of Temperature And Precipitation In East Asia Under Different Forcing Scenarios

The East Asian climate system is complex and controled by multiple factor.The processes and mechanisms of East Asian climate change are extremely complex with the global climate changes.Based on a set of atmosphere-only experiments from the Cloud Feedback Model Intercomparison Project Phase 3?CFMIP-3?,the changes of winter surface air temperature?SAT?and summer precipitation over East Asia as the responses to the uniform SST warming,4×CO₂ radiation effect,SST pattern change,and plant effect are analyzed.The uniform SST warming to 4K presents the most significant influence on SAT change,which strengthens the East Asian winter monsoon?EAWM?by intensifying the land-sea thermal contrast.As for the summer precipitation,the uniform SST warming effect could reduce rainfall in many parts of land regions over East Asia including eastern and southern of China,and southern slope of the Tibetan Plateau,while it increases rainfall over the west Pacific and South China Sea significantly.We can see that the SAT increases remarkably,which is induced by the heating from the warmer ocean,leading to the decreased surface relative humidity.Meanwhile,the land-sea thermal contrast is weakened as well as the East Asian summer monsoon?EASM?.As the result,both of the changes of circulation and water vapor transportation are not beneficial to the formation of rainfall.As the result of enhanced insulating effect,the CO₂ radiation effect can also induce the SAT increase over East Asia but with a magnitude smaller than that corresponding to the uniform sea surface temperature?SST?warming,in which more warming shows in land than ocean,and the EAWM could be weakened due to the decreased land-sea thermal contrast in response to the CO₂ radiation effect.Simulation results show the increased rainfall throughout East Asia continent,especially in Central China and the southern slope of the Tibetan Plateau.When the concentration of CO₂ rises,the enhanced insulating effect could warm the atmosphere,and the counter radiation heats the ground,which increases the land-sea thermal contrast and enhances the EASM,leading to the anticyclone anomaly over the low layer of East Asia,combined with the south westerly flow anomaly from the ocean,the precipitation increases over most areas of East Asia.The SAT changes in response to the SST pattern change show the largest difference among the three models,indicating that the SST pattern change could be the primary source of inter-model uncertainties for the East Asian SAT change.The precipitation response to the influence of SST pattern change is not significant,but also shows the slightly increase over most parts of land regions,which could probably be the results of increased relative humidity and the beneficial circulation changes.As for the influence of the plant effect,it could generate a SAT increase in most parts of land regions,particularly in the southern East Asia.Though the vegetation evaporation could be reduced when the CO₂ concentration rises,leading to the decreases of atmospheric water vapor and relative humidity,the atmosphere temperature increases more significantly at lower level than higher level,which reduces the atmospheric stability,and enhances the convection as well as the precipitation over south East Asia,though not so significant.We can see that the formation of precipitation is induced by a complex mix of factors.