Based on the monthly mean data of Argo and Aquarius satellite observations, we analyze the seasonal variation of sea surface salinity (SSS) in the tropical South Indian Ocean. The results show that the SSS has significant seasonal variation characteristics, that is, the SSS is lower in winter and higher in summer in the region of 60°-80°E, 5°-15°S. However, the center of anomalous SSS does not correspond to the center of anomalous precipitation. The seasonal variation of precipitation cannot explain the seasonal variation of SSS. Salinity budget analysis indicates that the ocean dynamics contribute to the seasonal variation of SSS. During the summer half of the year, the SSS increasing is attributed to the meridional advection transport high salinity from the equatorial region to the South Indian Ocean, as well as the entrainment strengthening from April to May. In the winter half of the year, precipitation increases, the northward currents transport low-salinity water induced by increasing precipitation to the study region, which favors the accumulation of low-salinity water in the region; at the same time, the westward zonal advection transports the low-salinity water from the Southeastern Indian Ocean to the west, both of which have important contributions to the decreasing SSS.%采用Argo以及Aquarius卫星观测的海表盐度月平均资料研究了热带南印度洋海表盐度的季节变化特征.结果表明,在60°—80°E,5°—15°S海域海表盐度具有显著季节变化特征;夏半年盐度升高,冬半年盐度降低;但是其异常中心与降水异常中心不对应,降水不能解释盐度的季节变化.盐度收支分析显示,在夏半年,海表盐度增加的主要原因是经向平流将赤道地区的高盐输送至该地区;其中4—5月期间,海洋垂向卷夹作用加强,对海表高盐异常也起到重要作用.在冬半年,大气降水增加,海洋表层环流使得降水引起的局部低盐水体在该区域辐合;同时,向西的纬向平流将东南印度洋的低盐水体继续输送到该地区,二者对冬半年海表盐度降低都有重要贡献.
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