CHARACTERISTICS OF ATMOSPHERIC CIRCULATION DURING SUMMER DROUGHTS/FLOODS OVER BEIJING AREA AND THEIR RELATION WITH THE EARLIER STAGE SST OVER THE NORTH PACIFIC

Using the monthly re-analyzed NOAA/NCAR grid point data of 1979 to 1995, the monthly SST data over the Pacific and summer equivalent torrential rain day data of the Beijing area, a composite analysis of the mean atmospheric circulation during droughts and floods and the correlation analysis between summer mean atmospheric circulation and earlier Pacific SST are carried out. There exist obvious discrepancies in the mean atmospheric circulation during summer droughts and floods over the Beijing area. Both the departure field of the mean atmospheric circulation in summer in flood years and the correlation field between the summer mean atmospheric circulation in East Asia and the number of summer equivalent torrential rain days in the Beijing area possess the main characteristics of the mean circulation pattern for the torrential rain process in North China. The correlation between SST of the Warm Pool and the number of summer equivalent torrential rain days in the Beijing area passed the significance test. The earlier SSTA of the warm pool is a strong signal for the summer droughts/floods over the Beijing area.