A PRIMARY STUDY OF SUMMER MONSOON INDEX OVER THE SOUTH CHINA SEA AND EAST ASIA BASED ON SATELLITE OBSERVATION

The results by statistical analysis of black body Temperature (TBB) pentad mean from the Japanese GMS in the period of May to August, 1980-2002, show that the summer monsoon index (SMI) is defined to be the pentad mean TBB(≤)273 K. Its intensity includes three levels: TBB＞268 K for weak monsoon, 268 K(≥)TBB＞263 K for normal monsoon and TBB(≤)263K for strong monsoon over the South China sea and East Asia. In the meantime, a diagnostic method using TBB pentad anomaly is also introduced to help identify monsoon intensity. The SMI is used to run statistical analyses of the initial onset of the monsoon and its pentad variations with the year and month. A fairly close relationship is found between pentad monsoon activity and heavy rainfall periods in the two typical flood years of 1994 and 1998,which resulted from heavy rainfall over the Yangtze River basin and south China.