Reconciling estimates of the free surface height in Lagrangian vertical coordinate ocean models with mode-split time stepping
Reconciling estimates of the free surface height in Lagrangian vertical coordinate ocean models with mode-split time stepping
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DOI：
10.1016/j.ocemod.2009.02.008
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发表时间：
2009
期刊：
影响因子：
3.2
通讯作者：
R. Hallberg;A. Adcroft
中科院分区：
文献类型：
--
作者：
R. Hallberg;A. Adcroft
在使用模式分裂算法对内部和外部重力模式进行时间推进的海洋模型中，外部和内部解均可用于提供自由表面高度演变的估计。在垂直坐标间距不变的模型中，通过指定适当的垂直平均速度来强制自由面高度的内部解与外部解一致是标准的；因为这是一个线性问题，所以它相对简单。然而，在具有潜在消失层的拉格朗日垂直坐标海洋模式中，必须对每个内层使用连续性方程的非线性离散。本文讨论了在自由面高度的内部和外部估计之间强制一致的选项，以及每种选择的结果，并提出了一种最优的、本质上准确的方法。
In ocean models that use a mode splitting algorithm for time-stepping the internal- and external-gravity modes, the external and internal solutions each can be used to provide an estimate of the free surface height evolution. In models with time-invariant vertical coordinate spacing, it is standard to force the internal solutions for the free surface height to agree with the external solution by specifying the appropriate vertically averaged velocities; because this is a linear problem, it is relatively straightforward. However, in Lagrangian vertical coordinate ocean models with potentially vanishing layers, nonlinear discretizations of the continuity equations must be used for each interior layer. This paper discusses the options for enforcing agreement between the internal and external estimates of the free surface height, along with the consequences of each choice, and suggests an optimal, essentially exact, approach.