Upwelling off Yangtze River estuary in summer
Upwelling off Yangtze River estuary in summer
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DOI：
10.1029/2005jc003250
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发表时间：
2006-11
影响因子：
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通讯作者：
Xingang Lü;F. Qiao;Changshui Xia;Jianrong Zhu;Yeli Yuan
中科院分区：
文献类型：
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作者：
Xingang Lü;F. Qiao;Changshui Xia;Jianrong Zhu;Yeli Yuan
用数值模拟方法研究了长江口及邻近海域夏季北寒带上升流的形成机制。首先，利用巡航观测、卫星海表温度（SST）和海表温度气候资料证实了这一现象的持续性特征。然后，采用MASNUM （Marine Science and Numerical Modeling）波浪-潮汐-环流耦合数值模式对上升流模式进行模拟。在模拟的基础上，设计了一组数值实验，探讨了引起上升流的主要机制。结果表明，潮汐混合对上升流的形成起主导作用。在近海海域，强烈的潮汐混合导致了相当大的潮锋水平密度梯度。上升流是次级环流的一个分支，由横锋密度梯度刺激。地形对上升流也有深远的影响，它引导底流向上上升，调节潮锋的位置和强度。除了潮汐和地形外，其他动力因素也会局部改变上升流的强度。长江流量（YRD）和台湾暖流（TWC）分别对YRE和舟山群岛附近的上升流起了部分作用。风对上升流的影响较小。在舟山群岛附近海域，风强迫通过减弱TWC对大陆架的侵蚀而对上升流产生负面影响，可能超过Ekman泵送的正面影响。
[1] The mechanisms of upwelling off the Yangtze River estuary (YRE) and in the adjacent waters in boreal summer are studied using numerical modeling. First, the persistent feature of this phenomenon is confirmed using cruise observations, satellite sea surface temperature (SST), and SST climatologic data. Then, the MASNUM (Marine Science and Numerical Modeling) wave-tide-circulation coupled numerical model is employed to simulate the upwelling patterns. On the basis of the simulation, a set of numerical experiments are designed to explore the main mechanisms inducing the upwelling. The results suggest that tidal mixing plays a predominant role in inducing the upwelling. In offshore waters, strong tidal mixing results in considerable horizontal density gradient across tidal fronts. Upwelling is induced as a branch of the secondary circulation, which is stimulated by the cross-frontal density gradient. Topography also exerts profound influences on upwelling by steering bottom currents to ascend upward and regulating tidal fronts in both location and intensity. Besides the tides and topography, other dynamical factors also alter the strength of upwelling locally. The Yangtze River discharge (YRD) and Taiwan Warm Current (TWC) account partly for the upwelling off the YRE and near Zhoushan Islands, respectively. The influence of wind on upwelling is small. In the coastal waters near Zhoushan Islands, the wind forcing exerts negative influences on upwelling by weakening the encroachment of TWC onto the continental shelf, which may exceed the positive effects of Ekman pumping.