THE PRELIMINARY ANALYSES ON THE ACTIVITIES OF SOUTH CHINA SEA SUMMER MONSOON IN 1998

Based on the NCEP reanalyzed data, OLR and SST observations, the onset time and the multi-time scales features of South China sea (SCS) summer monsoon of 1998 have been analyzed. The interactions between the SCS summer monsoon and SSTs anomalies have been studied. We found that: 1) The 1998 SCS summer monsoon was set up in 17th of May. 2)1998 was a weak summer monsoon year. OAR and Southwest component over SCS have the low frequency characteristics/with the period of one month and half a month respectively. The important sources of the low frequencies may come from the oscillations of the summer mon- soon over the Bay of Bengal and the cross equatorial flow at 105°E. 3) the weak summer monsoon may be produced by the strong warm event of eastern tropical Pacific, resulting in the positive SST anomalies over SCS-Arabian Ocean.