Coastal upwelling in the East China Sea in winter
Coastal upwelling in the East China Sea in winter
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DOI：
10.1029/2005jc003264
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发表时间：
2006-10-24
影响因子：
3.6
通讯作者：
Yuan, Yeli
中科院分区：
文献类型：
--
作者：
Qiao, Fangli;Yang, Yongzeng;Yuan, Yeli
[1]研究了冬季中国东海岸上升流的动力机制。首先，根据1999年1月巡航期间观测到的温度、盐度、营养物质和溶解氧数据，确定了ECS海岸外的上升流信号。然后采用MASNUM波-潮-环流耦合模式对环流的水文过程进行了模拟。仿真结果与观测结果的比较表明，该模型的性能令人满意。在成功模拟的基础上，进行了四次数值试验，对上升流机理进行了研究。结果表明，分隔近岸低盐度沿岸水和近岸台湾暖流(TWC)的密度(或盐度)锋是上升流的主要诱因。由于密度梯度较大，锋区附近的斜压压力梯度力(PGF)较大，并沿地形坡度产生一支上升支。风、TWC和潮汐影响密度锋的范围和强度，从而对上升流产生辅助影响。根据埃克曼的理论，北风季风对下沉有利。然而，风对冬季ECS沿岸上升流的净影响是正的，因为它驱动长江冲淡水(CDW)向南流动，形成密度锋。同样，TWC对上升流的综合作用也不利于阻塞CDW的路径。由于潮汐混合促进了CDW的扩展，因此潮汐对上升流有一定的贡献。
[ 1] The dynamic mechanisms of the upwelling off the East China Sea (ECS) coast in wintertime are studied. First, the upwelling signals off the ECS coast are identified by the observed temperature, salinity, nutrients, and dissolved oxygen data obtained during the cruises in January 1999. The MASNUM wave-tide-circulation coupled model is then employed to simulate the hydrography of the ECS. Comparisons between the simulations and observations show that the model performance is satisfactory. On the basis of successful simulation, four numerical experiments are conducted to investigate the upwelling mechanisms. The results suggest that the density ( or salinity) front, which separates the inshore Low Salinity Coastal Water and the offshore Taiwan Warm Current (TWC), is the primary inducement for the upwelling. Owing to strong density gradient, the baroclinic pressure gradient force (PGF) is quite large near the frontal zone, and this PGF elicits an upwelling branch along the topography slope. Wind, TWC, and tide affect the density front in extension and intensity, thus exerting subsidiary influences on the upwelling. According to Ekman's theory, the northerly monsoon is downwelling favorable. However, the net effects of wind on the upwelling off the ECS coast in winter are positive because it drives the Changjiang River Diluted Water (CDW) flowing southward and forms the density front. Similarly, the resultant effects of TWC on the upwelling are negative for obstructing the pathway of CDW. Tide contributes to the upwelling because tidal mixing facilitates the expansion of CDW.