Changma Indices from Inter-Annual Variability of Changma Rain and Their Prediction with a GCM

摘要

The monsoon rainfall, defined as the monsoon seasonal mean or intra-seasonal mean rainfall, plays as important role in affectingNwater resources as well as agricultural affairs. In relation to the strength of monsoon in conjunction with the variation of the large-scale atmospheric circulations, many researcher have compared the monsoon years as a "strong" and "weak" monsoon. The interannual variability of the June-July monsoon rainfall is very large as shown in Fig.1., particularly over Korea, southern China and southern Japan. The "Baiu" (Japanese), "Meiyu" (Chinese), and "Changma" (Korean), all of which possess characteristics of annual march and synoptic activities, in the sense of the study for prediction, are compared with similarity and difference in duration, intensity, and causes. So Changma indices inferred by the interannual variability from Changma rain are.required for the prediction in the intensity and duration year by year. In this study, Changma rain index is defined and its associated circulation are used for defining Changma indices. With the use of a GCM, predictability of Changma is evaluated in terms of Changma indices on the state of real May SST.