黄渤海环流对冬季大风过程的响应机制研究

发布时间：2018-08-19 06:26

【摘要】：冬季，黄渤海域常有寒潮引发的大范围的大风过程，本文关注于黄渤海环流对冬季大风天气的高频响应，包括黄海暖流的延迟响应、黄海暖流的西偏过程以及渤黄海的水交换过程，并研究天气尺度的黄海陆架波以及开尔文波在黄渤海环流响应过程中的作用。关于大风过程下的黄海暖流延迟响应，现场观测以及数值模式结果均显示，黄海暖流很好地响应大风爆发过程，但是存在响应时间上的滞后（形成滞后和峰值滞后），并且黄海暖流的响应过程伴随着黄海陆架波的传播。进一步的理论分析揭示了陆架波使黄海暖流产生延迟响应的动力学机制：黄海暖流在纬向上处于地转平衡，陆架波通过调整纬向上的压强梯度力来调整黄海暖流的强度。在大风爆发阶段，激发的陆架波传播之后才可以提供纬向上的压强梯度力，此时黄海暖流才得以形成，故将滞后大风的爆发时刻；在大风衰退阶段，随着动力平衡打破陆架波被释放再次传播，纬向上的压强梯度力将会达到极值，此时黄海暖流达到峰值，故将滞后大风峰值时刻。关于大风过程下的黄海暖流西偏过程，数值模式与理想数值试验结果均显示，，在大风过程期间，黄海暖流西向偏移至黄海西侧陆架（大风爆发阶段），并在黄海西侧陆架上增强与衰减（大风衰退阶段）。进一步的理论分析揭示了陆架波影响黄海暖流流轴位置的动力学机制。通过海盆北部的连续地形波导，海盆东侧的陆架波可以将高水位传入海盆西侧，导致纬向压强梯度力的极值位置也被向西推移，使得黄海暖流流轴发生西向偏移（因为黄海暖流在纬向上处于地转平衡）。进一步研究发现海盆北部地形波导是否连续（即是否存在位势涡度障碍）将决定黄海暖流是否西偏，底摩擦通过捕获陆架波将影响逆风流的西偏程度。关于大风过程下的渤黄海水交换过程，现场观测以及数值模式结果均显示，在大风爆发阶段，渤海水位下降，海水从渤海流入黄海，在大风衰退阶段，渤海水位回升，海水从黄海流入渤海，并且整个水交换过程伴随着开尔文波的传播调整。进一步的理论分析揭示了开尔文波影响渤黄海水交换的动力学机制。在大风爆发阶段，朝鲜半岛沿岸的开尔文波传入渤海导致整个渤海海平面下降，使得海水从渤海流入黄海，开尔文波被捕获在渤海海盆。在大风衰退阶段，开尔文波被释放而传出渤海，整个渤海海平面上升，使得海水从黄海流入渤海。因此，旋转效应下的开尔文波调整过程是影响渤黄海水交换的主要因素。
[Abstract]:In winter, there is a wide range of windy processes in the Yellow Sea and Bohai Sea. This paper focuses on the high frequency response of the circulation of the Yellow Sea and Bohai Sea to the windy weather in winter, including the delayed response of the Huang Hai warm current. The westward process of the Huang Hai warm current and the water exchange process of the Bohai Sea (Huang Hai), and the role of the synoptic scale Huang Hai shelf wave and Kelvin wave in the response process of the circulation in the Yellow Sea and Bohai Sea are studied. The results of field observation and numerical model show that the Huang Hai warm current is well responsive to the gale burst process, and the results of field observation and numerical model show that the response of Huang Hai warm current to the gale burst is very good. However, there is a lag in response time (formation lag and peak lag), and the response process of Huang Hai warm current is accompanied by the propagation of Huang Hai continental shelf waves. Further theoretical analysis reveals the dynamic mechanism of the delay response of the Huang Hai warm current caused by the continental shelf wave: the Huang Hai warm current is in geostrophic equilibrium at the latitudinal level, and the continental shelf wave adjusts the intensity of the Huang Hai warm current by adjusting the pressure gradient force in the zonal direction. In the gale burst stage, the induced continental shelf wave propagation can provide the upward pressure gradient force, and then the Huang Hai warm current can be formed, so it will lag behind the gale burst time, and in the gale recession stage, As the dynamic balance breaks the shelf wave is released and propagates again, the pressure gradient force will reach the extreme value, and the Huang Hai warm current will reach the peak value, so it will lag the peak moment of strong wind. The numerical model and ideal numerical test results show that, during the gale process, the Huang Hai warm current deviates from the west. The Huang Hai warm current shifts westward to the west shelf of Huang Hai (gale burst stage) and increases and attenuates on the west side of Huang Hai (gale recession phase). Further theoretical analysis reveals the dynamic mechanism of the influence of continental shelf waves on the position of the Huang Hai warm current axis. Through the continuous topographic waveguides in the northern part of the basin, the continental shelf waves on the east side of the basin can spread high water level to the west side of the basin, resulting in the extreme position of the zonal pressure gradient force also moving westward. The Huang Hai warm current axis is shifted westward (because the Huang Hai warm current is in geostrophic equilibrium at latitudes). It is further found that the continuity of topographic waveguides in the northern part of the basin (that is, the existence of potential vorticity barriers) will determine the westward deviation of the Huang Hai warm current, and the degree of westward deviation of the inverse wind current will be affected by the bottom friction through capturing the continental shelf waves. As to the exchange process of Bohai Sea and Yellow Sea under the strong wind, the field observation and numerical model results show that the Bohai Sea water level decreases during the gale burst stage, the seawater flows into Huang Hai from the Bohai Sea, and the Bohai Sea water level rises in the period of strong wind recession. Seawater flows from Huang Hai to the Bohai Sea, and the whole process of water exchange is adjusted by Kelvin wave propagation. Further theoretical analysis revealed the dynamic mechanism of Kelvin wave affecting sea water exchange in Bohai Sea and Yellow Sea. In the stage of strong wind burst, the Kelvin waves along the coast of the Korean Peninsula spread to the Bohai Sea, which caused the sea level to fall, which made the sea water flow from the Bohai Sea to Huang Hai, and the Kelvin wave was captured in the Bohai Sea basin. During the period of strong wind and recession, Kelvin wave was released and spread out to the Bohai Sea, and the sea level of the whole Bohai Sea rose, which caused the sea water to flow from Huang Hai into the Bohai Sea. Therefore, the adjustment process of Kelvin wave under rotation effect is the main factor affecting the sea water exchange between Bohai Sea and Yellow Sea.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P731.27;P732

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