南海的季节环流──TOPEX/POSEIDON卫星测高应用研究

Seasonal circulation in the South China Sea ──a TOPEX/POSEIDON satellite altimetry study

应用１９９２～１９９６年的ＴＯＰＥＸ／ＰＯＳＥＩＤＯＮ卫星高度计遥感资料，研究了 冬、夏季风强盛期多年平均的南海上层环流结构．研究结果表明，南海上层流结构呈 明显的季节变化，在很大程度上受该海区冬、夏交替的季风支配．冬季总环流呈气旋 型，并发育有两个次海盆尺度气旋型环流；夏季总环流大致呈反气旋型、但在南海东 部１８°Ｎ以南海域未见明显流系发育．研究还表明，南海环流的西向强化趋势明显， 无论冬、夏在中南半岛沿岸和巽他陆架外缘均存在急流，其流向冬、夏相反，是南海上 层环流中最强劲的一支．鉴于该海流的动力特征与海洋动力学中定义的漂流不同， 有相当大的地转成分，建议称为“南海季风急流（Ｓｏｕｔｈ Ｃｈｉｎａ Ｓｅａ Ｍｏｎｓｏｏｎ Ｊｅｔ）”．冬 季南下的季风急流在南海南部受巽他陆架阻挡折向东北，沿加里曼丹岛和巴拉望岛 外海有较强东北向流发育．夏季北上的季风急流在海南岛东南分为两支：北支沿陆 架北上，似为传统意义上的南海暖流；南支沿１８°Ｎ向东横穿南海后折向东北；二者 之间（陆架坡折附近）为弱流区．两分支在汕头外海汇合后，南海暖流流速增强．就 多年平均而言，黑潮只在冬季侵入南海东北部，并在南海北部诱生一个次海盆尺度的 气旋型环流。

The mean seasonal circulation in upper layer of the South China Sea (SCS) is studied using TOPEX/ POSEIDON altimetry remote sensing products from 1992 to 1996. The research results reveal that upper layer circulation in the SCS is predominated by seasonal alternating monsoons and its pattern varies seasonally. The winter general circulation appears to be cyclone consisted of two sub-basin cyclonic gyres. The summer circulation is generally anticyclonic, but no systematic current structure is found in the eastern SCS south of 18°N. The results also indicate that circulation in the SCS is notably westen intensified. A jet is observed, in both winter and summer, off the coast of Vietnam and the outer edge of Sunda shelf. It appears to be the strongest current in the SCS, which flows southword in winter, hut northward in summer. Since the dynamic feature of this jet is mainly geostrophic rather than wind drifting, it is suggested that name it as a jet (the SCS Monson Jet) instead of a drift. In winter, the Sunda shelf blocks the southward flowing jet and a northeastward return current is developed along coasts of Kalimantan and Palawan Ialands. In summer, the northward flowing jet splits off the southeast coast of Hainan Island. The northern branch flows along the China shelf, consisting with the traditional path of the SCS Warm Current. The southern branch flows to the east along 18°N across the basin, turns to northeast, and joints the northern branch again off Shantou. The SCS Warm Current is strengthened there by reunification and a zone of weak flow is observed near the shelf break between these branches. In the sense of multiyear mean, the Kuroshio intrudes into the northeastern SCS only in winter and induces a sub-basin cyclonic gyre in the northern SCS. At this period, the SCS Warm Current only exists in the area east of Shantou. In summer, the predominated current in the northern SCS is northeastward. There is no indication of Kuroshio invasion there. Validation using observations from satellite tracking surface drifting buoy shows that these remote sensing results are in good agreement with surface observation.