| HAN Lei. 2014. A two-time-level split-explicit ocean circulation model (MASNUM) and its validation. Acta Oceanologica Sinica, 33(11):11－35 |
| A two-time-level split-explicit ocean circulation model (MASNUM) and its validation |
| 一个两时间层分裂显格式海洋环流模式(MASNUM)及其检验 |
| Received:August 13, 2013 Revised:November 26, 2013 |
| DOI：10.1007/s13131-014-0553-z |
| Key words:ocean circulation model forward-backward method equatorial Rossby soliton Yellow Sea Cold Water Mass |
| 中文关键词: 海洋环流模式 前后差方法 赤道罗斯贝孤立波 黄海冷水团 |
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| Abstract: |
| A two-time-level, three-dimensional numerical ocean circulation model (named MASNUM) was established with a two-level, single-step Eulerian forward-backward time-differencing scheme. A mathematical model of large-scale oceanic motions was based on the terrain-following coordinated, Boussinesq, Reynolds-averaged primitive equations of ocean dynamics. A simple but very practical Eulerian forward-backward method was adopted to replace the most preferred leapfrog scheme as the time-differencing method for both barotropic and baroclinic modes. The forward-backward method is of second-order of accuracy, computationally efficient by requiring only one function evaluation per time step, and free of the computational mode inherent in the three-level schemes. This method is superior to the leapfrog scheme in that the maximum time step of stability is twice as large as that of the leapfrog scheme in staggered meshes thus the computational efficiency could be doubled. A spatial smoothing method was introduced to control the nonlinear instability in the numerical integration. An ideal numerical experiment simulating the propagation of the equatorial Rossby soliton was performed to test the amplitude and phase error of this new model. The performance of this circulation model was further verified with a regional (northwest Pacific) and a quasi-global (global ocean simulation with the Arctic Ocean excluded) simulation experiments. These two numerical experiments show fairly good agreement with the observations. The maximum time step of stability in these two experiments were also investigated and compared between this model and that model which adopts the leapfrog scheme. |
| 中文摘要: |
| 本文介绍了一个采用两时间层有限差分格式的、Boussinesq近似的、自由表面、模态分离的、采用地形坐标系的原始方程三维海洋环流数值模式(MASNUM)平台的建立。在时间差分格式方面, 该模式在正压和斜压模态均采用了简单实用的欧拉前后差格式替代常用的蛙跳格式。欧拉前后差格式具有二阶精度, 每个时间步仅计算一次右端函数, 并且不存在三时间层固有的计算模态问题。在交错网格下, 该格式的最大允许时间步长是蛙跳格式的两倍, 因此计算效率可以加倍。模式中还引入了一种空间平滑算法控制数值积分中的非线性不稳定。利用该模式进行了模拟赤道罗斯贝孤立波传播的理想数值实验, 以测试新模式的振幅和相位误差。本文还通过西太区域模拟和准全球模拟的数值实验来进一步验证该新环流模式的性能。两个数值实验的结果与观测都有很好的一致性。在两个实验中, 同时比较了该模式与采用蛙跳格式的模式的最大稳定性时间步长的差异。 |
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