The understanding of the Changma (Korean rainy season) is the most essential in identify the characteristics of summer rainfall in Korea, which accounts for over 50 percent of the annual rainfall totals. In particular, the accurate prediction of the onset of the Changma with the evolutionary features of the Asian summer monsoon circulation is imperative for the prevention of natural disasters that may occur during the Changma period. From examining the characteristics of the Changma in Korea and the predictability of the onset and withdrawal of the Changma, the following results are obtained 1) The onset and withdrawal of the Changma are closely related to the evolutionary features of the Asian summer monsoon circulation associated with the lower-level western Pacific high and upper-level South Asian anticyclone. 2) The onset of the Changma tends to commence about 30 days after the appearance of predominant easterly at the 100 hPa in Nanning of China. It is found that the withdrawal dates of the Changma are generally coincident with the dates when the first negative sign appears. 3) There is an apparent association between sea surface temperature anomalies in the tropical Pacific and in the middle latitude in prior monsoon and monsoon months and the onset and withdrawal dates of the Changma in the middle part of the Korean peninsula, respectively.
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