How can we improve a global ocean tide model at a regional scale? A test on the Yellow Sea and the East China Sea
How can we improve a global ocean tide model at a regional scale? A test on the Yellow Sea and the East China Sea
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DOI：
10.1029/1999jc900281
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发表时间：
2000-04
影响因子：
--
通讯作者：
F. Lefèvre;C. Provost;F. Lyard
中科院分区：
文献类型：
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作者：
F. Lefèvre;C. Provost;F. Lyard
在 TOPEX/Poseidon (T/P) 的背景下，基于有限元流体动力学建模方法与基于代表方法的数据同化相结合，开发了全球海洋模型。在全球范围内产生的解决方案比 T/P 时代之前的解决方案有了显着的改进。通常，主要潮汐分量与 100 个现场验潮仪之间的平均差异对于 M2 为 1.7 厘米，对于其他潮汐分量为 1 厘米或更小。然而，该解决方案以及 T/P 潮汐工作组内不同作者提出的解决方案的准确性在海岸线附近和大陆架上都较差。我们的黄海和东海有限元解决方案 (FES) FES94.1 解决方案 (YS-ECS) 就是这种情况，与沿海岸线分布的一组 192 个验潮仪相比，M2 潮汐的差异为 33 厘米，K1 潮汐的差异为 9 厘米。这主要是由于盆地的复杂几何形状和水深测量知识有限。本文的目的是研究如何通过专注于最具活力的沿海盆地之一的专用应用来改进我们的 FES 模型：YS-ECS（M2 约为 180 吉瓦，即整个海洋中消耗的全球能量的 8%）。对于此应用，沿海岸和大陆架断裂处实施了分辨率低至 5 公里的有限网格。通过用区域地图补充 ETOP05 数据库，特别关注水深测量。对底部摩擦力调整以及日和半日分量之间的非线性相互作用的敏感性测试使我们能够研究耗散参数化的影响，并在没有任何数据同化的情况下为潮汐谱的九个主要分量生成最佳解决方案（提高了 2 倍）。 M2 到观测值的距离现在为 ∼17.5 cm（全局方差为 92 cm），K1 为 4 cm（全局方差为 21 cm）。由于这些盆地的非线性分量很重要，因此计算了两个主要的四分之一日分量。这些改进可以通过五点来解释：（1）混合摩擦的选择，（2）网格的细化，（3）可靠边界条件的选择，（4）细化的地形，（5）使用特定的摩擦系数1.5×10−3。令人惊讶的是，M2 组件的能量预算导致的耗散与全球 FES94.1 估计的值相似。这是本研究的一个主要结果，它使我们得出这样的结论：当沿着开放边界强制具有海平面边界条件的区域模型时，模拟速度场会根据摩擦系数的调整进行调整，以便耗散在其开放边界上可用的相同数量的能量。
A global ocean model has been developed within the context of TOPEX/Poseidon (T/P) on the basis of a finite element hydrodynamic modeling approach combined with data assimilation based on the representer method. The solution produced at global scale represents a spectacular improvement over what was available before the era of T/P. Typically, the mean discrepancy between the main tidal components and a hundred in situ tide gauges is 1.7 cm for M2 and 1 cm or less for the other components. However, the accuracies of this solution and of that produced by different authors within the T/P tide working group are all worse near coastlines and over continental shelves. This is the case for our finite element solution (FES) FES94.1 solution over the Yellow Sea and the East China Sea (YS-ECS) where the discrepancy is 33 cm for the M2 tide and 9 cm for the K1 tide when compared to a set of 192 tide gauges distributed along the coastlines. This is due largely to the complex geometry of the basin and the limited knowledge of the bathymetry. The aim of this paper is to investigate how our FES model can be improved with a dedicated application focused on one of the most energetic coastal basins: the YS-ECS (∼180 Gigawatts for M2, i.e. 8% of the global energy dissipated in the whole ocean). For this application, a finite grid was implemented with a resolution down to 5 km along the coasts and over the continental shelf break. Particular attention was paid to bathymetry by complementing the ETOP05 database with regional maps. Sensitivity tests to the tuning of the bottom friction and the nonlinear interactions between the diurnal and semidiurnal components allow us to investigate the impact of dissipation parameterization and to produce an optimal solution, without any data assimilation, for nine main components of the tidal spectrum (improvement by a factor of 2). M2 distance to the observations is now ∼17.5 cm (global variance of 92 cm), and K1 is 4 cm (global variance of 21 cm). As nonlinear components are significant over these basins, the two main quarterdiurnal components are calculated. The improvements are explained by five points: (1) the choice of a mixed friction, (2) a refinement of the mesh, (3) a choice of reliable boundary conditions, (4) a refined topography and, (5) the use of a specific friction coefficient 1.5×10−3. Surprisingly, the energy budget for the M2 component leads to a dissipation similar to the value estimated by the global FES94.1. This is a major result of this study, which leads us to the conclusion that when forcing a regional model with sea level boundary conditions along the open limits, the simulated velocity field adjusts to the tuning of friction coefficients in order to dissipate the same amount of energy made available at its open boundaries.