大风作用下渤海环流和水交换的数值模拟研究

发布时间：2019-03-29 15:49

【摘要】：渤海是我国一个半封闭的内陆浅海，其特殊的地理位置在我国经济建设中起到了极为重要的作用。但是，随着近年来沿岸经济的快速发展，渤海的水质也在不断的恶化，而海洋的物理自净能力主要由海洋的物理动力过程决定。因此，本文以渤海海域的外强迫力作用为出发点，利用ROMS区域模式，对不同风场（CFSR日平均风场与CFSR月平均风场）、不同地形（渤海实际地形、Etopo2地形）作用下，渤海冬、夏季环流、温度以及水交换的变化情况进行探讨，重点分析了大风过程对冬季环流及夏季垂直分布结构的影响。研究结果表明，在风场改变后，冬季环流场流速变化也相当明显，最大可相差6cm/s；在2005年12月一次冬季大风过程前后，水位瞬时减小可达2m；由于渤海冬季盛行西北风，并且大风过程频发，从而导致渤海冬季环流受风场作用显著；除此之外，仅占冬季大约1/4时间的大风时段所导致的渤海环流形态分布同渤海冬季平均环流分布非常相似。而夏季环流结构的变化，则是风场与地形共同作用的结果：当地形中无法体现渤中浅滩后，渤海中央顺时针环流的范围、形状以及流速都发生巨大变化。因为温度与环流结构相互影响的原因，致使温度在冬季受风场影响较大，即使渤中浅滩在地形中没有体现，除了三个湾顶的温度会有所升高以外，温度的分布格局整体变化不大。通过对夏季渤海断面温度分布状况的研究发现，温跃层厚度以及中央高温水柱的形成是风场与地形共同作用的结果：当渤中浅滩在地形中不能体现时，渤海夏季无法形成温跃层，整个温度垂直分布与冬季类似，基本呈现上下一致的状态；当风场为日平均强迫时，渤海中央高温水柱在没有潮混合的作用下，依然也可以很好的出现。因此，对于夏季渤海断面温度垂向分布的形成原因，除去Lin et al.（2006）提出的潮流混合、波浪作用、地形的影响之外，还应该考虑高时空分辨率风场特别是大风的混合作用。对不同风场及地形作用下，对渤海水体平均存留时间研究发现：相较于月平均风场，在日平均风场驱动下，渤海整体平均存留时间有所较小，平均在100天左右，在渤中浅滩附近，最大可相差200天；当渤中浅滩无法在地形数据中体现时，渤海中部及辽东湾平均存留时间明显减少，最大可相差100天左右；除此之外，渤海水交换能力与环流之间存在一定的联系。本文主要的创新点在于：首次使用高时空分辨率风场资料作为渤海驱动场，并与气候平均态风场作用下环流、温度、平均存留时间进行对比。通过结果之间的对比发现，对于渤海而言，冬春季大风过程比较常见，其造成的强烈的流动可能对渤海内外水文环境起着非常重要作用，因此使用气候平均态的风场作为模式驱动场的行为，，可能会导致我们认识和研究渤海水动力过程不全面的结果。
[Abstract]:Bohai Sea is a semi-closed inland shallow sea in China, and its special geographical position plays a very important role in China's economic construction. However, with the rapid development of coastal economy in recent years, the water quality in the Bohai Sea is deteriorating, and the physical self-purification capacity of the ocean is mainly determined by the physical dynamic process of the ocean. Therefore, based on the external compulsive force in the Bohai Sea, using the ROMS regional model, under the action of different wind fields (CFSR daily mean wind field and CFSR monthly mean wind field) and different topography (Bohai Sea actual topography, Etopo2 topography), the Bohai Sea winter, under the action of different wind fields (CFSR daily average wind field and CFSR monthly mean wind field), The variations of circulation, temperature and water exchange in summer are discussed, and the effects of gale on winter circulation and vertical distribution in summer are emphatically analyzed. The results show that after the wind field changes, the velocity change of winter circulation field is also quite obvious, the maximum difference can be 6 cm / s, and the instantaneous decrease of water level can reach 2 m before and after a winter gale process in December 2005. Due to the prevalence of northwest wind in the Bohai Sea in winter and the frequent occurrence of strong winds, the circulation in the Bohai Sea is affected by wind field in winter. In addition, the distribution of circulation patterns in the Bohai Sea is very similar to that of the average circulation in the Bohai Sea during the strong wind period, which only accounts for about 1 ~ 4 hours in winter. The change of circulation structure in summer is the result of the interaction of wind field and topography. After the local shape can't reflect the Bohai Sea-middle shoal, the scope, shape and velocity of clockwise circulation in the center of Bohai Sea have changed enormously. Because of the interaction between temperature and circulation structure, the temperature is greatly affected by the wind field in winter. Even if the Bohai Sea-Central Shoal is not reflected in the topography, except that the temperature at the top of the three bays will rise, The distribution pattern of temperature has little change as a whole. By studying the temperature distribution of the Bohai Sea in summer, it is found that the thickness of thermocline and the formation of the central high temperature water column are the result of the interaction between wind field and topography. There is no thermocline in the Bohai Sea in summer, and the vertical distribution of the whole temperature is similar to that in winter. When the wind field is daily average forcing, the central high-temperature water column in the Bohai Sea can still appear well under the action of no tidal mixing. Therefore, in addition to the influence of tidal current mixing, wave action and topography proposed by Lin et al. (2006, the high spatial and temporal resolution wind field, especially the mixing effect of gale, should be taken into account for the formation of vertical distribution of temperature in the Bohai Sea in summer. The study on the average retention time of the Bohai Sea water body under different wind fields and topography shows that compared with the monthly average wind field, the overall average retention time of the Bohai Sea is smaller than that of the monthly average wind field, and the average retention time of the Bohai Sea is about 100 days, which is driven by the daily average wind field. Near the Bozhong Shoal, the maximum difference can be 200 days; The average retention time of the middle Bohai Sea and Liaodong Bay can be reduced obviously when the middle Bohai shoal can not be reflected in the topographic data, and the maximum difference is about 100 days. In addition, there is a certain relationship between the water exchange capacity and the circulation in the Bohai Sea. The main innovation of this paper is that the wind data with high spatial and temporal resolution are used for the first time as the driving field in the Bohai Sea, and compared with the circulation, temperature and average retention time under the action of the climatic mean wind field. Through the comparison between the results, it is found that the strong wind process in winter and spring is more common in the Bohai Sea, and the strong flow caused by it may play a very important role in the hydrologic environment inside and outside the Bohai Sea. Therefore, the use of the climate average wind field as the model driving field may lead us to understand and study the incomplete results of the hydrodynamic process in the Bohai 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】：P731.2

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