Impact of the November/December Arctic Oscillation on the following January temperature in East Asia

We investigated the impacts of the preceding Arctic Oscillation (AO) on winter East Asian temperature (T-EA) and the possible mechanisms. It was found that the correlation of the November AO (Nov AO) with the following January T-EA is more significant than that with the following December and February T-EA. Moreover, the January T-EA is also closely related to the preceding December AO (Dec AO). Further analysis revealed that a Rossby wave associated with the Nov AO is confined to high latitudes in December but shifts southeastward to East Asia in January. Similarly, the Dec AO-related wave activities propagating southeastward to East Asia could persist into the following January. Consequently, the signals of the Nov/Dec AO could be transmitted to the following January. Besides, an air-sea interaction might exist over the North Pacific (NP). The sea surface temperature (SST) over the central subtropical NP (west coast of North America) often rapidly rises (drops) a month later and peaks in the following January when the preceding Nov/Dec AO is in positive phase, causing horseshoe SST anomalies (SSTAs) to form in the NP, with positive SSTAs located in the central subtropical NP and surrounded by negative ones. Such a horseshoe SSTA could lead to a strengthening of the air temperature gradient in the north and a weakening in the south due to effective turbulent mixing in the boundary layer. A huge anomalous anticyclone therefore emerges in the NP and favors a weaker East Asian winter monsoon. Warmer January T-EA is eventually generated.