A revisit of the tropical-midlatitude interaction in East Asia caused by cold surges

Abstract

A short-wave train emanating from the Southeast Asian tropics which links interannual variations of the winter climate systems in both East Asia and North America was identified recently. This short-wave train may affect the activity of cold-surge disturbances over the eastern seaboard of East Asia, and the northwestern Pacific. The interaction between cold surges and the planetary-scale winter monsoon circulation in East Asia, was extensively explored after the Winter Monsoon Experiment (WMONEX). However, the finding of the North-Pacific short-wave train motivates us to revisit three aspects of the East-Asian circulation related to cold surges, with an emphasis on the effect of the wave activity in East Asia. First, the well-developed local Hadley circulation coupled with the East-Asian stationary waves and tropical troughs facilitates the interaction between cold surges, and planetary-scale circulation in East Asia. Second, the intensification of the East-Asian jet following cold surges is attributed to the ridge amplification/trough deepening of the East-Asian stationary waves by the cold-surge disturbances. Finally, the downward branch of the local Hadley circulation in East Asia provides the large-scale vortex compression, which enhances the development of cold-surge disturbances along the east coast of Northeast Asia.