Energetics and dynamics associated with two typical mobile trough pathways over East Asia in boreal winter

Abstract

Two dominant types of East Asian mobile trough (EAMT) are identified by a novel mobile trough detection algorithm. The two major EAMTs likely pass through to the north and the south of Lake Baikal. In this study, both of synoptic and planetary time scales influences on East Asia are studied. For synoptic scale, southern path of mobile trough shows a higher rate of intensification that of northern path. Southern path has stronger impact on Southeast Asia temperature fluctuation because of more southern pathway and stronger magnitude of wave train. But duration of fluctuation is shorter in southern due to the downstream development. For planetary scale, the northern path shows a large warm anomaly over Southeast Asia and a cold anomaly over Northeast Asia, which is associated with the northward shift of the jet stream. The southern path shows a cold anomaly over East Asia due to a northwesterly anomaly. The forcing of high frequency eddy on low frequency eddy is estimated in terms of momentum and energy. The reinforcement of high frequency eddy flux on low frequency variation can be observed in northern path, but not in southern path. The energy difference for two paths is also caused by the variations of barotropic and baroclinic conversion. The energy tendency of interaction between two frequency eddies is only responsible for sustention of energy anomaly over southwestern Japan.