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 shortwave 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.