Response Of The Asian Summer Monsoon To Global Warming And Its Feedback Attribution

The monsoon has an important impact on the weather and climate change in Asia.Based on the updated Coupled Model Intercomparison Project Phase 6(CMIP6)models,we investigated future changes of the Asian summer monsoon under four Shared Socioeconomic Pathway(SSP)scenarios using 19 CMIP6 models.The mechanism of future Asian summer precipitation changes was analyzed from the perspective of dynamic and thermodynamic effects.Attribute the tropospheric temperature changes in the monsoon region by applying a coupled climate feedback-response analysis method to reveal the radiative and non-radiative processes leading to tropospheric temperature changes in the monsoon region.The intensity of the South Asian summer monsoon(SASM)is projected to decrease by2.6%,6.3%,10.1%,and 11.1%,while the East Asian summer monsoon(EASM)intensity is projected to increase by 4.6%,7.9%,7.4%,and 9.8% until the end of the 21 st century for SSP126,SSP245,SSP370,and SSP585 scenarios,respectively.Moreover,summer precipitation in Asia is projected to increase remarkably in 2015-2099 under all four scenarios.The inconsistent warming trends over the Tibetan Plateau(TP),Northwest Pacific,and tropical Indian Ocean would greatly impact the monsoon circulations.The upper-troposphere warming trend over the surrounding oceans is remarkably greater than that over the TP,while the nearsurface warming trend over the surrounding oceans is smaller than that over the TP.The decrease of upper-troposphere TC between the TP and tropical Indian Ocean results in a weakening of the SASM circulation.The enhancement of the lower-troposphere TC between the TP and Northwest Pacific would strengthen the EASM circulation.Moisture budget analysis shows that the water-vapor would increase in the future,which would thermodynamically enhance summer precipitation through the anomalous vertical moisture transport associated with mean flow.The strengthening of the meridional circulation of the EASM would increase monsoon precipitation,while the weakening of zonal circulation of the SASM would dynamically reduce South Asian summer precipitation.Two dominant modes of summer upper tropospheric temperature(UTT)in the South Asian monsoon region were identified.The first mode features a monopole cooling anomaly,while the second mode features a meridional dipole mode,with the positive center located north of30°N,and the negative center in the Indian Ocean.Using CFRAM to quantify the contribution of the feedback process,the UTT anomalies of the two modes were decomposed into partial temperature anomalies arising from radiative and nonradiative processes.The results show that the summer UTT modes in the South Asian monsoon region were mainly attributable to the nonradiative feedback processes of atmospheric dynamics,ocean dynamics,surface heat fluxes,and land-sea heat storage processes,and the synergistic effects of ocean heat storage and surface heat flux processes play a dominant role in the temperature change of the Indian Ocean region.The atmospheric dynamic process has a great contribution to the temperature anomalies of the middle and high latitudes.The atmospheric dynamic process has a great contribution to the temperature anomalies of the middle and high latitudes.The first mode is mainly due to the teleconnection effect caused by the decadal transition of the Atlantic SST,which provokes the eastward propagation of Rossby wave and causes the abnormal upper troposphere atmospheric circulation,which affects the transport of temperature and vorticity,and thus leads to the warming of UTT.The anomalous transport of temperature and vorticity in the second mode is related to the intensification of Walker circulation during the decay stage of El Ni(?)o and the strengthening and northward movement of the South Asian high.