Winter extreme precipitation over the Tibetan Plateau influenced by Arctic sea ice on interdecadal timescale

The Tibetan Plateau(TP)and the Arctic are the most sensitive regions to global climate change.However,the interdecadal varibility of winter extreme precipitation over the TP and its linkage with Arctic sea ice are still unclear.In this study,the characteristics and mechisnems of the TP extreme precipitation(TPEP)influenced by Arctic sea ice on interdecadal timescale are studied based on the daily precipitation,monthly sea ice concentration and ERA5 reanalysis data from 1980 to 2018.We found that the dominant mode of the TPEP in winter mostly exhibits a uniform spatial variation on the interdecadal timescale,with an opposite weak variation in the southeastern TP,and the Arctic sea ice concentration(SIC)before 2002 are larger than that after 2003.The interdecadal variation of TPEP is affected by two teleconnection wave trains regulated by the Barents and Kara Sea ice.In the light ice years,a remarkable positive geopotential height(HGT)anomaly appears over the Barents-Kara Sea and a remarkable negative HGT anomaly is located over the Lake Baikal.Two wave trains originating over the Barents-Kara Sea can be observed.The southern branch forms a wave train through the North Atlantic along the subtropical westerly jet stream,showing a‘+-+-+'pattern of HGT anomalies from Arctic to the TP.Negative HGT anomaly controls the western TP,which creates dynamic and water vapor conditions for the TPEP.The northern branch forms a wave train through the Lake Baikal and the southeast of the TP,showing a‘+-+'HGT anomaly distribution.Positive HGT anomaly controls the southeastern TP,which is not conducive to precipitation in the region.When the SIC in the Barents-Kara Sea increases,the situation is opposite.The above analysis also reveals the reason for the difference in the east-west distribution of the TPEP.

Asian summer monsoon responses to the change of land‒sea thermodynamic contrast in a warming climate:CMIP6 projections

It is of practical significance to use the updated Coupled Model Intercomparison Project Phase 6(CMIP6)models to study the impact of changes in land‒sea thermodynamic contrast(TC)on the Asian summer monsoon under different scenarios and to compare the similarities and differences of the impact mechanisms between different monsoon regions.In this study,we investigated future changes of the Asian summer monsoon under four Shared Socioeconomic Pathway(SSP)scenarios using 19 CMIP6 models.The intensity of the South Asian summer monsoon(SASM)is projected to decrease by 2.6%,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 21st 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 near-surface 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.