Multidecadal Changes in the Influence of the Arctic Oscillation on the East Asian Surface Air Temperature in Boreal Winter

The time-varying influences of the wintertime Arctic Oscillation (AO) on the concurrent East Asian surface air temperature (EAT) are investigated based on JRA-55 reanalysis data. Results reveal that there are multidecadal variations in the influences of wintertime AO on the EAT during 1958-2018. Before the mid-1980s, the impact of winter AO on the simultaneous EAT is weak and confined northward of 40 degrees N over East Asia. After the mid-1980s, by contrast, the winter AO's influence is stronger and can extend southward of 25 degrees N over East Asia. The multidecadal variations of the winter AO-EAT relationship are mainly modulated by the magnitudes of the North Pacific center of the winter AO. During the periods with strong North Pacific center of the winter AO, in association with the positive phase of the winter AO, the low-level southeasterly anomalies on the west side of the anticyclone over North Pacific bring warm air from the ocean to East Asia and lead to a significant winter AO-EAT relationship. In contrast, the southerly anomalies are weak and even reversed to northerly over the coast of East Asia during the periods with weak North Pacific center of winter AO, which confines the influence of winter AO on northern East Asia and lead to an insignificant winter AO-EAT relationship. Our finding provides new insight into the understanding of the decadal changes of AO's impacts on the regional climate.