The interdecadal change of ENSO impact on wintertime East Asian climate

摘要

The interdecadal change in the relationship between the winter mean surface air temperature (SAT) over East Asia (EA) and the El Ni?o–Southern Oscillation (ENSO) is investigated using both observational data and a simple general circulation model. The positive phase of the first empirical orthogonal function (EOF) of SAT over EA is characterized by significant warming over midlatitude to high-latitude EA and is linked to the Arctic Oscillation. The second EOF (SAT-EOF2) is represented by significant cooling extending from 55°N to the tropics and abnormal warming over high-latitude EA. Focus is given to SAT-EOF2 which has a close relationship with the La Ni?a-type sea surface temperature (SST) anomalies. A clear shift in SAT-EOF2 is observed in the mid-1980s. The relationships between SAT-EOF2 and ENSO in two subperiods, i.e., 1957 to 1982 (P1) and 1986 to 2010 (P2), are discussed and compared. Results show that the relationship between SAT-EOF2 and ENSO significantly strengthens after the mid-1980s due to stronger SST and precipitation anomalies in P2 than in P1 associated with ENSO in the tropical western Pacific. In the midlatitudes, the Pacific-North American teleconnection pattern is more closely related to ENSO in P2, whereas in P1, the ENSO-related atmospheric circulation anomalies are more similar to a zonally orientated teleconnection pattern. Numerical experiments suggest that the difference in the ENSO-related circulation anomaly in the midlatitudes is likely related to the difference in the climatological mean flows of these two subperiods.