The Dynamical Effects of Divergent Wind on the Intraseasonal variabinty of the East Asian Circulation

In this paper, the dynamical effeCts of divergent wind on the intraseasonal variability of atmospheric circulationover East Asia are analyzed by using the function of Rossby-wave source and the energy exchanging function between divergent component and rotahonal component of the flow.The results analyzed from the observed data show that the advection of voracity by divergent wind caused by theheating due to the monsoon rainfall in the south to the Yangals River and the strong convective activities around thePhilippines may play an important role in the northward jump of westerly jet stream during the seasonal transitionfrom sprillg circulation to summer circulahon over East Asia. Due to the northward movement of the advechon ofvorticity by the divergent willd, the energy transformation from divergent component into rotational component canbe caused over the Yellow River basin and Northwest China and will cause the intensification of the zonal flow there.Thus, the jet stream abruptly shifts northward to North China.Moreover, the analysed results also show that the advection of vorticity by divergent wind caused by the heatingdue to the strong convective activities around the Philippines also plays an important role in the intraseasonal variability of the circulation over East Asia during the seasonal transition from summer to winter. With the southward'movement of the advection of vorticity by the divergent wind, the energy transformation from divergent componentinto rotational comPOnent can be caused over East Asia, espeially over the Yangtze-Huaihe River basin. Therefore,the jet stream gradually moves southward from North China to the YangtZe River basin.