RELATIONSHIP BETWEEN THE INTENSITY OF SOUTH CHINA SEA SUMMER MONSOON AND THE PRECIPITATION IN RAINING SEASONS IN CHINA

Four indexes are compared and analyzed that indicate the intensity of the South China Sea summer monsoon in 1951～1998. It is found that they are generally consistent in the interannual variation and have basically the same years of monsoon intensity as determined by them, though with some differences in some years. The relationship between the monsoon intensity and the precipitation in raining seasons in China is statistically studied and the results are as follows. In the years of strong (weak) summer monsoon in the South China Sea, the rain bands are of Pattern One (Three) distribution in the summer of China and the rainfall of the Changjiang R. Valley in June and July is mainly below and drought (above and flood), whereas rainfall is flood (normal and drought) during the yearly-second raining season in the Guangdong province. The intensity indexes for the South China Sea summer monsoon are in high anticorrelation with the precipitation over the middle and lower reaches of the Changjiang R. Valley and Huaihe R. Valley but in high correlation with that in the region south of Changjiang R. and the yearly-second raining season in southern China. Severe floods taking place in the summertime of China (like the extra severe floods in the Changjiang R. Valley in 1998 and the extra severe heavy rains in southern China in 1994) are associated with intensity anomalies of the summer monsoon in the South China Sea. In addition, meridional wave train anomalies teleconnection of the 500 hPa geopotential height field in East Asia in the Northern Hemisphere, which is resulted from the strong and weak summer monsoon activity in the South China Sea, is an important mechanism contributing to the summer precipitation in China.