Seasonal march of Asian summer monsoon

Abstract

This paper investigates the seasonal march of the summer monsoon through several different sub-divisions of the Asian monsoon region. Five data sets, the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP), the upper-tropospheric water vapour band Brightness Temperature (BT), the Outgoing Longwave Radiation (OLR), the lower tropospheric wind and Korean daily rainfall for 1980–1995, are used. Analysis shows that the largest area of deep convection in the global atmosphere is located over the tropical Indian Ocean–equatorial western Pacific; its centre being positioned 110°E along the equator in boreal winter and then moves northwestward to 80°E at 5°N in late July. In late April, the area of deep convection first extends northward into the Indo-China Peninsula (ICP). In mid-May it abruptly covers over the central South China Sea (SCS) region. After the onset of SCS monsoon, deep convection starts to develop northward along the eastern coast of China, East Tibet Plateau (ETP) and Indian sub-continent, simultaneously. Based on the analysis of BT and lower-tropospheric circulation, Asian summer monsoon can be divided into six inter-linked sub-regional monsoons. They are Indo-China Peninsula monsoon, SCS monsoon, South Asian (Indian) monsoon, ETP monsoon, East Asian (south China, lower Yangtze River and Japan) monsoon and Northeast Asian (north China and Korea) monsoon. In seasonal course, their onset periods take place in late April–mid-May, mid-May, mid-May–late July, mid-May–early June, mid-May–late June and late June–mid-July, respectively. Copyright © 2000 Royal Meteorological Society