1998年夏季南海环流的三维结构

The three dimensional structure of the circulation in the South China Sea during the summer of 1998

利用1998年6月12日至7月6日南海的调查资料,采用三维海流诊断模式,计算了夏季南海三维海流,结合卫星海表面高度距平资料,得到结果如下:(1)南海北部,在吕宋岛以西海域和东沙群岛附近海域,分别存在一个反气旋式涡和东沙群岛西南的气旋式涡.(2)南海中部,越南以东海域出现由暖涡W3和冷涡C3组成的一个准偶极子.在冷涡C3和暖涡W3以北分别存在一个暖涡W2和冷涡C2.(3)在越南近岸存在较强的、北向的西边界射流,此北向射流在14°N附近离岸转为东,并流入两涡W3和C3之间.(4)南海南部,在巴拉望岛的西南海域,100 m以浅水层存在反气旋式涡,而在其较深水层,此处变为气旋式涡.(5)南海环流的动力机制有两个:最重要的动力因子为斜压场与地形相互作用项,其次为风应力与地形相互作用项.(6)讨论了夏季南海环流垂向速度w分布,例如在30 m层,Ekman抽吸对垂向速度w分布起着重要作用.(7)与2000年夏季南海环流的比较,1998年夏季计算海域涡旋W3,C3,C2等的位置变化并不大.

On the basis of hydrographic data obtained from 12 June to 6 July, 1998, the three dimensional structure of circulation in the South China Sea （SCS） is computed by using three dimensional diagnostic model. The combination of sea surface height anomaly from altimeter data and numerical results provides a consistent circulation pattern for the SCS, and the main circulation features can be summarized as follows： （1） In the northern SCS, there are a cyclonic eddy C1 near Dongsha Islands and an anti-cyclonic eddy Wl in the area west of Luzon Island. （2） In the central SCS, a stronger anti-cyclonic eddy W3 and a cyclonic eddy C3 compose a quasi-dipole in the area southeast of Vietnam. （3） A coastal northward jet is present at the western boundary near the coast of Vietnam. This northward coast jet flows northward and turns eastward at the about 14°N, and then it flows southeastward into the area between eddies W3 and C3. （4） In the southern SC~ the current is weaker. （5） Most important dynamical mechanism is because of the joint effect of the baroclinity and relief. The second dynamical mechanism is because of the interaction between the wind stress and relief. （6） The distribution of the vertical component of current velocity is discussed. （7）Comparing of the circulation in 1998 with 2000, their change is not large.