Interdecadal Change of the Interannual Relationship Between Autumn North Atlantic Horseshoe Sea Surface Temperature Anomaly Pattern and Winter Temperature Over Northeast China

This study investigates the interdecadal change of the relationship between the interannual variation of autumn sea surface temperature (SST) anomalies in the North Atlantic and winter surface air temperature (SAT) anomalies over Northeast China (NEC) during 1961–2020. The analysis reveals that the first empirical orthogonal function (EOF) mode of autumn North Atlantic SST anomalies is the North Atlantic horseshoe (NAH) pattern. The connection between the autumn NAH SST anomaly pattern and winter SAT anomalies over NEC has experienced an interdecadal shift around 1990. It is weak during 1961–1989 (P1), whereas it is strong during 1990–2020 (P2). Further analysis suggests this change is related to the difference in the persistence of the NAH SST anomaly pattern. During P1, the NAH SST anomalies decay rapidly. There are negative–positive–negative geopotential height anomalies around the Western Europe–Ural Mountains–Northeast Asia, resulting in negative SAT anomalies over NEC. In contrast, during P2, the SST anomalies maintain from autumn to winter. The North Atlantic SST anomalies during P2 exert positive–negative–positive geopotential height anomalies around the Davis Strait–Ural Mountains–Northeast Asia, leading to significantly positive SAT anomalies over NEC. The NCAR CAM5.3 simulation results indicate differences in atmospheric circulation over Eurasia, especially Northeast Asia, under different SST forcings during the two periods. The simulation results are basically consistent with the observations.