A Lagrangian vertical coordinate version of the ENDGame dynamical core. Part I: Formulation, remapping strategies, and robustness
A Lagrangian vertical coordinate version of the ENDGame dynamical core. Part I: Formulation, remapping strategies, and robustness
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DOI：
10.1002/qj.3368
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发表时间：
2018-07
影响因子：
8.9
通讯作者：
I. Kavčič;J. Thuburn
中科院分区：
文献类型：
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作者：
I. Kavčič;J. Thuburn
前人的工作证明，通过使用拉格朗日或准拉格朗日垂直坐标(LVC)可以改善数值模型动力核心的拉格朗日守恒和相关性质。大多数以前基于这一思想的模型发展都进行了静力近似。在这里，LVC是在一个非静力可压缩的欧拉方程动力核心中实现的，使用几乎相同的数值方法来结束英国气象局大气统一模式的业务动力核心EndGAME。这使得能够使用尽可能相似的数值方法对动力学核心的LVC和高度坐标版本进行干净的比较。由于拉格朗日曲面会随着时间的推移而变形，因此模型高度会不断地重置为特定的“目标高度”，并且模型场的值会重新映射到它们的新位置。讨论了这些目标水平的不同选择，以及侧重于不同守恒或平衡性质的重新映射策略。给出了一个斜压不稳定试验的样本结果。LVC公式被发现比高度坐标形式的健壮性要差一些；讨论了其中的一些原因。
Previous work provides evidence that Lagrangian conservation and related properties of a numerical model dynamical core can be improved by the use of a Lagrangian or quasi‐Lagrangian vertical coordinate (LVC). Most previous model developments based on this idea have made the hydrostatic approximation. Here the LVC is implemented in a non‐hydrostatic compressible Euler equation dynamical core using almost identical numerical methods to ENDGame, the operational dynamical core of the Met Office atmospheric Unified Model. This enables a clean comparison of LVC and height‐coordinate versions of the dynamical core using numerical methods that are as similar as possible. Since Lagrangian surfaces distort over time, model level heights are continually reset to certain “target levels” and the values of model fields are remapped onto their new locations. Different choices for these target levels are discussed, along with remapping strategies that focus on different conservation or balance properties. Sample results from a baroclinic instability test case are presented. The LVC formulation is found to be rather less robust than the height‐coordinate version; some reasons for this are discussed.