The Interdecadal Transition Of Summer Precipitation In North China In The Early 2010s And Its Influence On North Atlantic Sea Temperature And Arctic Sea Ic

Based on CN05.1 monthly precipitation data from 1961 to 2021,ERA5 reanalysis data,and Hadley Center monthly sea ice(SIC)data and sea surface temperature(SST)data,this research studies the interdecadal transition of summer precipitation in North China in the early 2010 s,and reveals the influence and possible mechanism of Eurasian teleconnection and Arctic sea ice on the interdecadal transition of summer precipitation in North China.The main conclusions are as follows:(1)The summer precipitation in North China has significant interdecadal variation from1961 to 2021.When the summer precipitation in North China is positive,The Mongolia-Northeast China region is controlled by significant cyclonic anomalies.The anomalous northerly wind transports high-latitude cold air into North China,which is conducive to the intersection of cold and warm air in North China,thus contributing to the increase of precipitation in North China.There are cyclonic water vapor transport anomalies over Mongolia-Northeast China,and the water vapor transport from the western boundary is enhanced.The anomalous ascending motion over North China is mainly located in the plain area,which is conducive to the increase of precipitation in North China.(2)The summer precipitation in North China experienced an interdecadal transition from less to more in the early 2010 s,and the mutation time was 2012.In the wet period(2012-2021),the Mongolia-Baikal region is controlled by cyclonic anomalies,which are conducive to the entry of cold air from the north into North China.During the wet period,the pseudo-equivalent potential temperature increases,and its vertical variation enhances,indicating that the atmosphere over North China is warmer and wetter,and the atmospheric stratification is unstable,which is also in favor of the development of vertical movement.This interdecadal transition is weakly affected by the East Asian summer monsoon.The horizontal advection term of the relative vorticity causes the jet position to extend eastward and northward,so that most of North China is located on the south side of the jet axis.The divergence of the deviation wind on the south side is conducive to the upward movement of North China,which is conducive to the increase of precipitation in North China.(3)During the wet period,the North Atlantic SST tripole pattern excites positive geopotential height anomalies and anticyclonic anomalies in Atlantic,which affects the Eurasian(EU)teleconnection wave train.There is a strong meridional geopotential height gradient in the north of North China,which leads to the eastward extension and northward movement of the East Asian jet.The anticyclonic anomalies over East China Sea are conducive to the entry of water vapor into North China.The decrease of Arctic sea ice from May to July during the wet period leads to divergent wind anomalies over the Arctic.The divergence wind anomaly propagates energy to the mid-latitude region,which leads to the generation of vorticity in the mid-latitude region.As a result,there are significant convergence wind anomalies and positive velocity potential anomalies in East Asia in summer,accompanied by positive Rossby wave source anomalies.The positive Rossby wave source anomalies can enhance the Rossby wave train,and stimulate the cyclonic anomaly in Lake Baikal and the anticyclonic anomaly in western Japan.This anomalous circulations are conducive to the entry of water vapor into North China,which is conducive to the increase of precipitation in North China.(4)Through partial regression analysis,it is concluded that the local circulations excited by NAT affect the EU wave train,and the EU wave train propagates into North China along the middle latitude through Eurasia,thus influencing the precipitation in North China;Arctic sea ice reduction excites high-latitude wave train and enters North China through Lake Baikal,thus influencing precipitation in North China.