1998年南海西南季风活动的初步分析

利用NCEP再分析资料和OLR、SST观测数据,分析了1998年南海西南季风的建立日期、强度的多时间尺度变化特征、与海面温度的相互作用以及对广东降水的影响.得出南海西南季风建立的日期为5月17日(5月4候).1998年为弱季风年,OLR具有1个月左右的振荡周期,西南风具有半个月左右的振荡周期.孟加拉湾地区季风和105°E越赤道气流是南海季风低频变化的重要策源地.1998年南海季风弱,主要是由于初春赤道东太平洋海温正距平,并导致南海-阿拉伯海海温正距平的结果.

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 17^th 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.