【作者】 于华明；

【导师】 鲍献文； Dr.Thomas Pohlmann；

【作者基本信息】 中国海洋大学 ， 物理海洋学， 2010， 博士

【摘要】 为进一步提高我国全球海洋潮汐的数值模拟和数值预报精度,发展较高分辨率的全球海洋环流和潮汐数值模型,本文基于FVCOM (Finite Volume Coastal Ocean Model)有限体积数值模式,建立了全球海洋无结构网格环流潮汐模型(Global Ocean Circulation and Tide Model based on the Unstructured Mesh, GOCTM-UM).该模型充分利用无结构三角形网格在不同区域具有不同空间分辨率的特点,根据不同区域环流和潮汐的运动尺度进行全球海洋网格设计。该模型巧妙地避免了开边界条件的引入,平衡了模型网格高分辨率需求和大计算量要求之间的矛盾,并且在垂向上采用通用混合坐标,有效地提高了海表和海底混合层的垂向分辨率。在考虑海水自吸引和负荷潮作用(Sea Water Self-Attraction and Earth-Loading Effects, SAL)的情况下,利用TOPEX/POSEIDON系列卫星高度计模型数据对全球海洋潮汐模型进行了最优插值(Optimal Interpolation)数值同化实验。在一定程度上,提高了我国全球海洋潮汐模拟的精度,具有较为广阔的应用前景。通过将本文数值模拟结果与大洋潮汐站数据、近岸潮汐站数据、卫星高度计数据,以及与其它潮汐模型、环流模型等结果进行对比验证,认为本文模型结果基本可信,数值模拟方案可行。本文充分利用GOCTM-UM模型采用无结构三角型网格在渤、黄、东海和南海等中国近海网格加密的优点,对全球海洋环流和潮流进行了多种方案的数值模拟实验,以分析东中国海及毗邻海域环流和潮流运动的能量结构为主线,探讨了东中国海及毗邻海域潮流对环流的作用及其机制问题。分析结果发现：(1)海洋潮流对于海洋环流主要具有三方面的作用和贡献,即潮汐余流、非线性平流相互作用和湍混合耗散相互作用。整体来说,三者相比,非线性平流相互作用和湍混合耗散相互作用对东中国陆架海海洋环流的影响相对较强；相比冬季东中国海环流,潮汐余流的大小较为微弱,仅在海峡和近岸浅水等部分海区潮汐余流对海洋环流具有较为重要的影响。(2)在冬季东中国陆架海区,由于潮流的加入,对于海洋环流模型来说,模拟环流动能的改变约占环流动能的9.8%,其中表层影响约占6.3%,而底层影响约占15.7%。通过理论分析和数值实验分析,认为海洋潮流和海洋环流非线性平流相互作用和混合耗散相互作用在海洋中占有较为重要的作用,忽略海洋潮流与海洋环流之间的非线性相互作用,将带来非线性平流机械能输送项和能量湍耗散项各约10%以上的误差,理论分析和数值分析的结果基本一致。(3)潮汐对于东中国海底层海域湍混合具有主导作用,其重要性强于潮流在海表的湍混合作用。在地形梯度较大的区域和浅水区域,底层混合强度最强,潮流的加入对于环流模型底层湍涡动粘性系数具有较大的改变,改变量可以达到10-3m2/s的量级。正压潮汐模型所得到的湍涡动粘性系数与海洋环流模型得到的湍涡动粘性系数直接相加所得到的结果,与含潮海洋环流模型得到的湍涡动粘性系数相比,较大,具有一定的差异,尤其在底层海洋,这是考虑潮流作用而改进海洋环流湍封闭方案所需要考虑的。更多还原

【Abstract】 In order to further improve our global ocean tide prediction accuracy and develop high-resolution global ocean circulation and tide numerical model, the Global Ocean Circulation and Tide Model based on Unstructured Mesh (GOCTM-UM) is configured and established, based on Finite Volume Coastal Ocean Model (FVCOM), in this dissertation. This model takes advantage of the unstructured triangular grids, which have the different spatial resolutions in the different regions, to design the global ocean mesh according to the different scales of the circulation and tides in different regions. Thus, the model avoides introducting the open boundary conditions cleverly, and balances the contradiction between the high resolution requirement and the large computation. Furthermore, the model uses the general layers in the vertical coordinate, which can improve the vertical resolution of mixing layers effectively in both the sea surface and the sea bottom.Considering the Effects of the Sea Water Self-Attraction and Earth-Loading (SAL), GOCTM-UM assimilates the tidal elevation data of TOPEX/POSEIDON satellite altimeter model using the optimal interpolation. That improves the accuracy of our global ocean tide numerical simulation in some aspects so that it has some broad application prospects. By comparing the numerical simulation results with the data of tide gauges in the pelagic ocean, the data of coastal tidal gauges and the satellite altimeter data, as well as with other tidal models and the results of general circulation models, the credibility of the GOCTM-UM’s results is verified, and the solution of the numerical simulation is feasible.By utilizing the GOCTM-UM model with fine unstructured triangular grids in the Bohai Sea, the Yellow Sea, the East China Sea and the South China Sea, a variety of numerical simulation experiments have been conducted to analyse the energy structure of ocean circulation and tidal current, and discuss the mechanism of the tidal current effects on the ocean circulation in the East China Sea and its adjacent waters. The results show that:(1) The roles of ocean tidal current on the ocean circulation include the tidal residual current, the non-linear advection interaction and the turbulent mixing dissipation. Overall, the non-linear advection and the turbulent mixing nonlinear interaction play important roles on the ocean circulation of the East China Shelf Seas. Compared to the winter circulation in the East China Seas, the tidal residual current is relatively weak, only in some straits and the coastal sea area of shallow water, the tidal residual current has more important influence.(2) The change of the kinetic energy takes 9.8% of the kinetic energy of the ocean circulation, of which about 6.3% at the surface and about 15.7% at the bottom, when the tidal current is added into the ocean circulation model in the East China Seas in winter. By the theoretical analyses and the numerical analyses, the ocean interaction of nonlinear advection and the interaction of the mixing dissipation between the ocean tidal current and the ocean circulation take important roles in the ocean dynamic numerical simulation. If ignoring the nonlinear interaction between the ocean tidal current and the ocean circulation, it will produce more than 10% errors of these two items. And the results of the theoretical analyses are consistent with the results of the numerical analyses.(3) Tide has great effects on the ocean bottom turbulent mixing in the East China Seas, and the effects at the bottom are much stronger than that at the sea surface. Paticularly, in the areas of large topographic gradient and in the shallow water areas, the turbulent mixing is stronger at the bottom layer. The turbulent edd viscosity can be changed significantly at the scale about 10-3 m2/s when the ocean tidal current is added into the ocean circulation model. The sum of turbulent eddy viscosity obtained from barotropic tide model and that obtained from the ocean circulation model is different from that obtained from the circulation and tide coupling model, especially, at the bottom. This is what should be considered when improving the turbulent closure scheme of the ocean circulation model.更多还原