Projections And Analysis The Inter-model Spread Of Global Monsoon Precipitation By CMIP5 Models

The global monsoon precipitation(GMP)has a far-reaching effect on more than 60% of the population around the world,and is of great importance to the national economic development and people's lives.The fifth phase of the Coupled Model Intercomparison Project(CMIP5)provides us with many models to study GMP activities.In this study,the ability of 40 CMIP5 models to simulate GMP activities are evaluated,and the change of monsoon precipitation under global warming is projected.In addition,the sources of intermodel spread of the change in monsoon precipitation under RCP4.5 scenario are analyzed.(1)The multi-model ensemble(MME)mean result of the CMIP5 models has a good skill in reproducing annual mean precipitation,annual range precipitation and six major monsoon areas.(2)Under global warming,the CMIP5 models have shown a unified increased precipitation in global and Northern Hemisphere monsoon areas.The MME result indicates that the change rates of global,Northern Hemisphere(NH),Southern Hemisphere(SH)monsoon precipitation are about 1.37%,2.35% and 0.26% respectively when global mean surface temperature increased by 1K,but the results show a great inter-model spread among CMIP5 models.(3)The change in annual mean precipitation is tightly related to the change in local summer monsoon precipitation.The change in Northern Hemisphere Summer Monsoon(NHSM)precipitation is robustly negatively correlative to the Southern Hemisphere Summer Monsoon(SHSM)precipitation change.(4)Over the NH,the high change rate in monsoon precipitation is accompanied by the high inter-hemispheric thermal contrast,i.e.,a warm NH and a cool SH.The inter-hemispheric thermal contrast is associated with an enhanced low-level cross-equatorial flow over the Indian Ocean,Western Pacific Ocean,and Atlantic Ocean.The enhanced low-level crossequatorial flow can transport more moisture to the NH.The anomalous moisture convergence over the NH tropical region enhances the Hadley circulation and moves the Intertropical Convergence Zone(ITCZ)northward.As a result,the NHSM precipitation increases.The change in monsoon precipitation over the SH is dominated by a warm SH and a cool NH,which indicates similar mechanism is valid during the austral summer over the SH.The results suggest that the inter-model spread of change in monsoon precipitation is mostly driven by the differences in thermal contrast between hemispheres among the CMIP5 models.