冬季黄海东海环流和长江冲淡水扩展

【作者】 张衡；

【导师】 朱建荣；

【作者基本信息】 华东师范大学 ， 自然地理学， 2004， 硕士

【摘要】 本文利用一个高分辨率的三维数值模型，综合考虑多种动力因素，首先对黄海东海各环流分量以及总环流进行了精确模拟，然后在此基础上模拟分析了风应力和径流量改变对长江冲淡水扩展的影响。在各种数值试验之前首先对M₂分潮进行了模拟，验证了模式采用潮位边界与潮流边界的等效性，并且为以后的数值试验提供了潮流边界数据。冬季的表层风生流场中，从渤海湾的南岸一直到台湾海峡的西海岸，均出现了沿岸向南的风生流。表层沿岸风生流的强度和范围都大于底层。黄海南部、济舟岛的西南还有一股逆风北上的流动，与黄海沿岸风生流构成一个气旋式环流。在边界力产生的余流数值试验中，台湾东北附近海区的表、底层都存在很强的入侵陆架的海流。还有一股沿陡峭陆架坡向东北流动的海流。该海流在127.6°E，30°N附近发生分支，一支向北通过对马海峡流出计算区域：另一支继续流向东北方，然后在九州西南由于受地形的影响转向东南。密度流场中，在表层沿大陆坡附近海域有很强的流向东北的密度流。而此处底层的流场则比较散乱。长江河口表层密度流流出口门后主体方向基本为东南，杭州湾内部出现一个气旋式环流。底层长江口、杭州湾外海区的密度流流向与表层正好相反，总体上向北或西北流动。各因素共同作用下的黄海东海总流场数值模拟中，模式较好的再现了黑潮、台湾暖流、对马暖流、黄海暖流和沿岸流等各环流流系。 冬季长江冲淡水在偏北风的作用下在一条狭窄的带内沿岸向南扩展。冬季冲淡水主要浮置于高盐海水之上，其平面和垂向影响范围以及流速大小都受到风速的显著影响。风速增大一倍后，冲淡水出长江口后迅速转向正南方流动，冲淡水向南扩散的态势和流速都会明显加强，而台湾暖流在长江口附近海区北上的趋势则明显减弱。风速减小一倍后，表层冲淡水流向更加偏东，而冲淡水的流速变化不是很明显。长江口附近海区北上的台湾暖流有所加强。径流量增大一倍后，表层冲淡水出口门后的流速明显增大很多，在长江口门附近形成很强的盐度锋面。径流量减小以后，表、底层口门附近的冲淡水流速略有减弱。远离长江口门的苏北沿岸外海区以及台湾暖流附近海区的流场变化很小。更多还原

【Abstract】 In this paper making use of a three dimension high resolution numerical model which takes into account various dynamical factors, Shelf currents in Yellow Sea and East China Sea are simulated exactly at first. Then based on the results the impact of wind and runoff on the expansion of the Changjiang diluted water are simulated and analyzed.This paper simulates the M2 tide before the other numerical experiments. The results testify that the numerical with the tidal current open boundary condition are consistent with those with the tidal level open boundary condition, and provide the boundary data for the experiments. In the winter wind-driven current field, the current flow south from the south coast of the Bohai Sea gulf to the west coast of Taiwan Strait. The surface currents strength are bigger than the bottom currents. And an ocean current in the south of the Yellow Sea flows north, constituting a cyclone type circulation with the wind-drift coast current. In the numerical experiment whose residual currents are induced by the boundary forces, there are strong currents invading the shelf in the area to the northeast of Taiwan. Another ocean current flows northeast along the steep continental shelf. The current divides into two branches at 127.6°E, 30°N. One branch flows north through the Tsushima Strait; the other still flows northeast, then turns to southeast to the southwest of Kyushu due to the impact of topography. In the density current field, a strong ocean current flows northeast along the shelf at surface. But the bottom current field is in disorder. In Changjiang estuary area, the surface density currents flow southeast mostly, and a cyclone type circulation appears in Hangzhou gulf. But the bottom currents flow north in the area near Changjiang estuary and Hangzhou gulf, just opposite to the surface currents. The numerical experiment reconstructed fairly successfully the circulation patterns of the Kuroshio, the Taiwan Warm Current, the Tsushima Warm Current and coast currents.In winter under the effect of north wind the Changjiang Diluted Water flows south in a narrow area along the coast. The intensity of the Changjiang Diluted Water on the high salt sea water is affected in evidence by the wind. In the case of increaseof wind speed, the diluted water away from Changjiang estuary turn south quickly, the current speed is enhanced obviously. And the Taiwan Warm Current dies down clearly in a trend for flowing north. In the case of decrease of wind speed, the surface diluted water trends east more, the variety of the current speed is not very obvious. And the Taiwan Warm Current flowing north in this area is enhanced. In the case of increase of runoff, the surface diluted water enhances greatly, and a very strong salinity front appears near the Changjiang estuary. In the case of decrease of runoff, the speed of the diluted water at the surface and bottom weakens. The current field far away from the Changjiang estuary area doesn’t change much.更多还原