赤道印度洋中部断面东西水交换的季节变化及其区域差异

Seasonal variability of the west-east water mass exchange on the section of central equatorial Indian Ocean and its regional difference

采用海洋再分析资料和实测资料研究了热带印度洋中部东西水交换特征。结果表明存在两个相互独立的过程,即北印度洋过程(4°～6°N)和赤道过程(2°S-2°N)。北印度洋过程受季风影响显著,11月至翌年3月冬季风期间表现出很强的低盐水向西输送,5-9月夏季风期间则为高盐水向东输送;由于冬季风期间的输送较强,年平均表现为低盐水向西输送。赤道过程分为表层过程和次表层过程。表层赤道过程受局地风场驱动,有明显的半年周期;4-5月和10-11月的东向流将赤道西印度洋的高盐水向东输送,其余月份相反;向东的输送较强,年平均表现为净高盐水向东输送。在次表层赤道过程没有明显的季节变化,海流全年一致向东,将海盆西部的高盐水向东输送。

Based on the ocean reanalysis data sets and observations,the authors analyze the west-east water mass exchange in the central Indian Ocean.It is found that there are two independent processes in the equatorial Indian Ocean（EIO,2°S-2°N） and the North Indian Ocean（NIO,4°-6°N）,respectively.The NIO process is mainly induced by monsoon current,which advects low-salinity water westward from November to March,and during May—September the high-salinity water is carried to the east.The westward advection is stronger than the eastward,so the annual mean shows westward.The EIO process can be divided into the surface and the subsurface process.The surface equatorial process driven by equatorial wind is characterized by a semiannual cycle.During April—May and October—November,the high-salinity water of Arabian Sea is transported eastward,and the low-salinity water of Bay of Bengal westward in the other months.The annual mean advoction is eastward.The high-salinity water is eastward conveyed by subsurface equatorial process all year around.