用广义随底坐标海洋模式研究南海2000年夏季环流

王惠群; 袁耀初; 管卫兵; 楼如云; 王康墡

用广义随底坐标海洋模式研究南海2000年夏季环流

1.
国家海洋局, 第二海洋研究所, 浙江, 杭州, 310012;国家海洋局, 海洋动力过程和卫星海洋学重点实验室, 浙江, 杭州, 310012
2.
国家海洋局, 第二海洋研究所, 浙江, 杭州, 310012;国家海洋局, 海洋动力过程和卫星海洋学重点实验室, 浙江, 杭州, 310012;香港科技大学, 海岸与大气研究中心, 香港, 九龙

基金项目: 国家重点基础研究发展规划项目(G1999043805);预研项目(2001ccb00500);国家海洋局青年基金资助项目(2000209)

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出版历程
- 收稿日期: 2003-03-01
- 修回日期: 2003-05-07

A study of the circulation in the South China Sea during the summer of 2000 using a generalized terrain-following ocean model

1.
Key Laboratory of Ocean Dynamic Processes and Satellite Oceanography, Hangzhou 310012, China;Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
2.
Key Laboratory of Ocean Dynamic Processes and Satellite Oceanography, Hangzhou 310012, China;Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China;Center for Coastal and Atmospheric Research, Hong Kong University of Science and Technology, Hong Kong, China

摘要

摘要: 基于2000年8月在南海调查航次得到的水文资料,首次采用广义随底坐标形式的改进POM模式对南海夏季环流进行了数值研究.用正交曲线性水平网格覆盖观测区域,在垂向上对近表海面层次采用近似z坐标,而近底层则为随底坐标.在计算海区实际地形及假设的水平均匀而垂直层化的密度分布下,实施的两个数值计算试验表明,本模式采用的垂直坐标方案比传统的σ坐标方案优越,随底坐标模式因压力梯度项在起伏地形下产生的系统计算误差将变得十分的微小.在南海2000年夏季环流的实际计算中,首先对观测资料进行了60d的诊断计算,然后在诊断已得到的动力场结果基础上,又进行了10d左右的预报运行得到半诊断结果.从计算结果来看,它依赖于参数C_vis与C_dif的选择,特别是参数C_vis,文中取值为C_vis=C_dif=008.比较诊断与半诊断两个计算过程的结果,它们在定性上较为一致,在定量上有些差别.这是因为半诊断计算的方法对密度场作适当的动力调整,使其与地形、风场等更加匹配.在大尺度环流结构不受影响的情况下,尽可能地消除了小尺度噪声,可使计算得到的流场更为清晰.2000年8月南海计算区域环流的最大特点是多涡结构,其中有些反气旋暖涡和气旋式冷涡相间分布.在越南东南海域自表层至1000m水层稳定存在着一个显著的反气旋暖涡,其中心位置在11°51'N,112°07'E(诊断计算),水平尺度约为300km.此暖涡以东存在一个气旋式冷涡,这两个冷、暖涡是研究海区夏季环流的重要环流特征之一.在计算区域东北部夏季环流以反气旋环流系统为主;在计算区域东南部夏季环流以气旋系统为主;南海夏季环流分布,明显出现西部强化特征.
- 南海环流 /
- 广义随底坐标海洋模式 /
- 三维数值模拟
Abstract: Based on the hydrographic data obtained by the cruise in August 2000 in the South China Sea (SCS), the revised Princeton Ocean Model (POM) with a generalized terrain-following coordinate system, i.e., the -T-F ocean model (GTFOM) was firstly adopted to study the circulation in the SCS during summer.The observational area is covered well by an orthogonal curvilinear grid in the horizontal, while in the vertical a generalized terrain following grid is set up which is similar to a z-level grid in most part of z-direction, but departs from the z level constraint near the bottom boundary, such that the lowest layer follows the bottom topography.With the actual topography and horizontally uniform, vertically varying buoyancy field, the comparison between the two numerical experiments shows that the adopted vertical grid scheme of GTFOM is better than the traditional sigma coordinate scheme, and the systematic error produced by the horizontal pressure gradient calculation near steep topography be comes much smaller when the scheme GTFOM is used.For the calculation of circulation in the SCS during the summer of 2000, there are two computed methods, i.e., the diagnostic and semidiagnostic calculations.The horizontal mixing coefficients for viscosity and diffusivity are calculated by two Smagorinsky-type for mulations.It is found by several numerical experiments that the computational results are sensitive to the taken values of their parameters.Comparisons between the diagnostic and semi diagnostic results indicate that they agree qualitatively, but there are some differences between them in quantity.In the semi diagnostic calculation, the flow field is hy drodynamically adjusted with the density field, wind stress and bottom topography, moreover, the small scale noises are removed.The main feature of circulation over the computational domain of SCS during August 2000 is as follows: There exists many warm and cold eddies, and among them the most notable eddy is the anticyclonic warm eddy southeast off Vietnam, and its center is located at 11°51'N, 112°11'E and its horizontal scale is about 300 km.East off this warm eddy there is a cyclonic cold eddy.The existence of such two cold and warm eddies is one of important circulation char acteristics in the SCS during the summer of 2000.The northeast part of SCS is dominated mainly by an anticyclonic circulation system, while it becomes cyclonic circulation system in the southeast part of SCS.Additionally, a western intensification phenomenon obviously occurs in the distribution of circulation in the SCS.
- circulation in the South China Sea /
- generalized terrain-following ocean model /
- three dimensional numerical simulation

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