资源环境科技发展态势分析平台

A colder winter over Northeast Asia (NEA) has traditionally been attributed to the stronger East Asian winter monsoon (EAWM) on interannual timescale. However, the present work proposes this robust linkage becomes weak during 1993-2003, along with the changes of the underlying condition in the last three decades. During 1981-1992 and 2004-2016, the loss of autumn Arctic sea ice condensation (SIC) leads to the stratospheric warming and the polar vortex weakening, which results in the enhancement of the Siberian High (SH) and the colder surface air temperature (SAT) over NEA. In particular, the persisting anomalies of snow cover near the Mongolian Plateau from autumn to winter could amplify the influences of Arctic SIC on the EAWM during 1981-1992. However, during 1993-2003 both the EAWM and the SAT over NEA are modulated by the tropical SSTAs in the western Pacific warm pool, corresponding to a weak association between the EAWM and the SAT over NEA. These tropical warm SSTAs could excite a meridional teleconnection over East Asia to generate a barotropic anticyclonic anomaly in situ. It not only weakens the SH and EAWM but also decreases the SAT over NEA. Therefore, the predictor of winter SAT over NEA is altered from the cryosphere to the tropical SSTAs in this episode. The changes of interdecadal background may contribute to the distinct interannual relationship between EAWM and winter SAT over NEA. This will increase the uncertainty in seasonal forecast on the winter climate over East Asia.