夏季南海上层环流动力机制的数值研究

The numerical study of the dynamic mechanism of the South China Sea upper circulation in summer

通过利用一个分区性的正压 -斜压衔接模式来探讨夏季南海的上层环流特征及其动力机制 ,结果表明 :夏季期间 ,由于风生环流的不稳定性促使在东沙群岛附近的气旋涡的强度及位置发生变化 ,并间接导致黑潮侵入南海北部的程度变化以及气旋涡南侧的反气旋式环流、西沙群岛西南侧的气旋涡的强度和范围出现波动现象 ;在南海南部的北向西边界流由于离岸的西南季风所驱动在中南半岛中部沿岸脱离岸线往东北方向的流动 ,导致沿岸的水体大量流失而在沿岸形成一支南向补偿流并在西沙群岛西南侧诱生一气旋涡 ,而上述的离岸西边界流则作顺时针方向流动 ,从而在南海南部形成反气旋式大环流 ;在南沙海槽附近出现的局地气旋涡和万安滩附近的气旋涡分别受β效应、底形效应的作用而形成 .

An divisional barptropic and baroclinic connection model is employed to study the South China Sea(SCS) upper circulation characteritics and its dynamic mechanism in summer. The results are: during summer, the strength and position of the cyclonic eddy adjacent to Dongsha Islands varies due to the instability of wind driven current, which indirectly cause the intrusion extent of Kuroshio into the northern SCS,the strength and range of the anticyclonic gyre to the south of the above eddy, the cyclonic eddy to the southwest of Xisha Isalnds etc. to fluctuate. The northward western boundary current in the southern SCS flows northeastward off the shoreline of middle Indo China Peninsular due to the driving of southwest monsoon offshore, which brings about loss of large amount water alongshore and the formation of a southward compensating current alongshore, and then a cyclonic eddy to the southwest of Xisha Isalnds is induced. The above offshore western boundary current flows clockwise, thus forms an anticyclonic gyre in the southern SCS. The local cyclonic eddies adjacent to Nansha Trough and Wanan Shoals are formed by the actions of β effect and bottom topographic effect.