2014年9月南海西部冷涡及东向急流三维结构观测

Observed three-dimensional structures of a cold eddy and an eastward jet in the western South China Sea during September 2014

根据2014 年9 月1-9 日现场观测温度、盐度、深度（CTD）资料和法国卫星中心（AVISO）提供的海表面高度异常（SLA）资料, 调查南海西部冷涡和东向急流的三维结构.结果表明, 该冷涡于8 月3 日开始出现, 9 月29 日消亡, 持续大约2个月.现场观测期间, 冷涡水平尺度约为150km, 其形态受其东南边缘的东向急流影响呈长轴为西南-东北向椭圆状,冷涡的垂直尺度为自海表面到200m 深度.强的表层地转流（最大值达到1.0m·s^-1）出现在靠近东向急流区的冷涡东南侧.航次观测期间东向急流的纬向范围是在109？E 至113？E 之间, 最大地转流流速达到1.2m·s^-1, 流向基本呈偏东北向, 且流幅约为100km; 东向急流的垂直尺度可达到150m 深度.现场观测期及其前后的SLA 和海表面地转流分布表明, 东向急流和北侧的冷涡的形态季节内演变过程可能受到南海海盆尺度风应力影响.

By using in situ hydrographic measurements from a cruise during September 1~9, 2014 and real-time sea level anomaly (SLA) data provided by archiving validation and interpretaiton of satellite oceanographic data (AVISO), we survey three-dimensional structure of a cold eddy and eastward jet in the western South China Sea. The results indicate that the cold eddy began to appear on August 3 and disappeared on September 29, lasted for about two months. During the in situ observation, the horizontal scale of the cold eddy was about 150 km and its shape was an ellipse with the long axis located along the southwest-to-northeast direction, which was affected by an eastward jet on the southeast side of the cold eddy. And the cold eddy extended downward for more than 200 m with a vertically tilted central axis. Strong surface geostrophic flow (maximum value reaching 1.0 m×s-1) emerged on the southeastern area of the cold eddy, which was closest to the area of eastward jet. However, during the survey, the zonal range of the eastward jet was between 109°E and 113°E, its maximum geostrophic flow velocity reached 1.2 m×s-1 and it flowed in a northeast direction. The width of the eastward jet was approximately 100 km and the vertical structure of the eastward jet extended 150 m. The evolution of the SLA and the surface geostrophic currents during August and September showed that the development of the eastward jet and the northern cold eddy may be influenced by basin-scale wind stress in the South China Sea.