中文摘要：

利用1951～1998年多种大气和海洋资料,研究了太平洋和印度洋在南海夏季风爆发中的作用。结果表明,影响南海夏季风爆发早晚的因素存在着年代际变化：1951～1970年,印度洋起主要作用;1970～1998年西太平洋起主要作用。该年代际变化主要是1970年前后北极涛动（AO）的跃变以及西太平洋副高强度变化的结果。1951～1970年间,AO指数为负值,北印度洋出现西风异常,同时西太平洋副高强度偏弱,有利于南海夏季风早爆发。此时,北印度洋纬向风成为控制南海夏季风爆发的主要因素。同时,南印度洋副热带偶极子（IOSD）对南海夏季风的爆发也具有一定影响。当IOSD为正偶极子[西南印度洋海表面温度异常（SSTA）为正,印度洋的其它区域为负]时,北印度洋盛行西风异常,南海夏季风爆发偏早;反之偏晚。1970～1998年间,AO指数为正值,北印度洋盛行东风异常,同时西太平洋副高强度偏强,不利于南海夏季风爆发。在此期间,西太平洋暖池热含量成为控制南海夏季风爆发的主要因素：当西太平洋暖池热含量为正异常时,南海夏季风爆发早,反之偏晚。

英文摘要：

The role of the western Pacific and the Indian Ocean in the South China Sea（SCS） summer monsoon onset is investigated by analyzing various atmospheric and oceanic datasets.The Results show that the impact factor of the SCS summer monsoon onset exhibits interdecadal variation.From 1951 to 1970,the impact factor exists in the Indian Ocean,from 1970 to 1998 it occurs in the western Pacific Ocean.The interdecadal variation of impact factor results from the significant abrupt change of the Arctic Oscillation（AO） and the intensity of the Western Pacific Subtropical High（WPSH）.For the period of 1951 through 1970,an anomalous westerly wind over the northern Indian Ocean induced by a negative AO index and the weak WPSH that are helpful to the SCS summer monsoon onset make the zonal wind over the northern Indian Ocean the main factor controlling the SCS summer monsoon onset.Meanwhile,during the period,the southern Indian Ocean Subtropical Dipole（IOSD） is closely related to the SCS summer onset.The positive IOSD（with positive SST anomaly in the southwestern Indian Ocean,a negative SST anomaly in the other regions） results in anomalous westerly wind over the northern Indian Ocean and early onset of the SCS summer monsoon,and vice versa.For the period of 1971 to 1998,an anomalous easterly wind induced by a positive AO index and stronger WPSH offer an unhelpful condition for the SCS summer monsoon onset when the heat content in the western Pacific warm pool become the main factor controlling the SCS summer monsoon onset.The positive（negative） anomalous heat content in the western Pacific warm pool leads to earlier（later） onset of the SCS summer monsoon.