Interdecadal Variability Of Atmospheric Teleconnection Patterns Affecting Winter Temperature In East Asia

Based on NCEP,JRA-55 and ERA5 reanalysis dataset from the boreal winters through1958/1959 to 2017/2018,under the premise of deducting the linear trend,the atmospheric teleconnection patterns that affect the primary modes of winter air temperature over East Asia are revealed,and the related interdecadal variation characteristics are further discussed via the conventional statistical methods,e.g.,EOF,REOF,correlation and regression.The results show that on the interannual timescales the Scandinavian teleconnection pattern(SCA)is the most relevant pattern to the first principle component(PC1)of East Asian air temperature,and the East Atlantic teleconnection pattern(EA)is the most relevant pattern to the PC2 of East Asian air temperature.On Note that the correlation coefficients between SCA index and the PC1 of the winter air remperature over East Asia are more large and significant than that between East Asia winter monsoon index.On the interdecadal timescales,they have also well correspondence.The phase-shifting of SCA at the late 1970 s and the beginning of the current century corresponds to that of PC1 of East Asia air temperature;likewise,the phase-shifting of EA at the early 1980 s and the beginning of the current century corresponds to that of PC2 of East Asia air temperature.It is noteworthy that the correlation coefficients between SCA index and PC1(R1)and between EA index and PC2(R2)exhibit different decadal variations from those of the two teleconnections.R1 shows a weakening feature before the mid-1980 s,and increases significantly there after,indicating a strengthening influence of SCA on East Asia air temperature.Such an interdecadal variation for R1 is related to whether the circulation anomalies centered at the western Russia for SCA can extend further eastward,which might be determined by the Atlantic Multidecadal Oscillation(AMO).During the positive phase of AMO,the related circulation anomalies can induce the eastward expansion of the SCA pattern,which is favorable for the south intrusion of cold air temperature from the polar region and forming a larger R1.There is also an evident decadal variation for R2.R2 is significant only during the periods from the 1970 s to the 1980 s and after 2000 s,which is related to whether EA can form a local meridional dipole circulation pattern over East Asia.However,the reasons from the external forcing are complex and no significant corresponding signal from the sea surface temperature or sea ice is detected.