Dominant Interannual and Decadal Variability of Winter Surface Air Temperature over Asia and the Surrounding Oceans

Abstract

To clarify the interannual variability of winter surface air temperature (SAT) over Asia and the surrounding oceans, the authors applied principal component analysis to normalized monthly SATs. The first mode represents the Asian north?south dipole pattern with a node over the Tibetan Plateau. This component has close relationships to the Arctic Oscillation and cold surge variability around Southeast Asia, showing decadal oscillation with signal changes in 1988 and 1997. The second mode is the inner-Asian mode with a center to the north of the Tibetan Plateau. This component connects to fluctuations of not only the western Siberian high but also the Icelandic low, which is associated with the pattern of the polar vortex over Eurasia. A recent warming trend and possible relationship to solar activity are also shown. The modes of Asian SAT variability associated with ENSO are extracted as the north?south dipole mode over the tropical western Pacific and Japan (the third mode) and Silk Road mode (the fourth mode). The two independent modes appear to be caused by different sea surface temperature (SST) anomalies over the western Pacific and Indian Ocean and their associated atmospheric Rossby wave responses: the atmospheric wave trains over both the north and south of the Tibetan Plateau in the third mode, and the atmospheric wave train that propagates toward the Silk Road via Greenland in the fourth mode.