南沙群岛海域风场特征——卫星散射计观测资料分析

WIND FIELD FEATURES IN NANSHA ISLANDS WATERS,SOUTHERN SOUTH CHINA SEA—SATELLITE SCATTEROMETER DATA ANALYSIS

通过对欧空局提供的ERS卫星微波散射计风场资料的再分析,研究了南沙群岛海域的风场特征,主要包括南沙群岛海域的东北季风和西南季风随纬度的变化以及一年中根据风应力特征划分的4个时期的风应力与风应力旋度的分布特征。

The ERS microwave scatterometer wind data was reanalyzed to study the fea- tures of the wind field in the Nansha Islands waters, southern South China Sea, inclu- ding the latitudinal variations of northeast and southwest monsoons and the distribution characters of wind stress fields as well as the wind stress vorticity fields in four phases which are divided according to the different features of wind stress in the Nansha Islands waters. The following results were obtained. (1) The presence frequency of northeast (southwest) monsoon decreases (increases) with latitude decreasing. (2) In the north- east monsoon phase (from Nov. to Mar. ), strong northeast monsoon prevails over the Nansha Islands waters, stronger in the northwest part than in the southeast part. The wind stress vorticity is the strongest in the first three months and starts to weaken in February and becomes the weakest in March. (3) During the transition between mon- soons in Apr. and May, the northeast monsoon still controls the Nansha Islands wa- ters, but the vorticity almost reaches 0. Usually the southwest monsoon bursts in May, when the Nansha Islands waters is still controlled by the very weak southwest monsoon, but the vorticity has become negative in most parts. (4) The southwest monsoon phase is from June to the end of September. The distribution of wind speed is similar to that in the northeast monsoon phase. The wind stress vorticity is negative in the south and pos- itive in the northwest part. (5) During the transition between monsoons in Oct., the northeast monsoon firstly controls the north part, while the southwest monsoon still controls the south part (south to 8°N), which indicates that the transition begins in the north part of the Nansha Islands waters.