Abstract To resolve nonlinear internal wave motions in regional domains, we propose a one-way ocean model nesting framework in which a nonhydrostatic model is nested within a regional model. The nesting scheme produces internal tides that propagate freely into and out of the nonhydrostatic model domain with no reflections while nudging the low-frequency motions. We demonstrate the method with idealized test cases and a field-scale simulation of the South China Sea. The method relies on four parameters, the time scale of low-pass filtering, the time scale of low frequency forcing, the time scale of sponge damping and the width of the sponge damping layer. We present guidelines for selecting these four parameters based on the background stratification. The internal tides from the large-scale model steepen through nonlinear and nonhydrostatic effects and reasonably match observations at a fraction of the computational cost needed with a single uncoupled model. The model critically relies on the background stratification inherited from the large-scale model, which in this case leads to an underpredicted phase speed and amplitude in the nested model result. This highlights the need for large-scale ocean models to incorporate observational stratification data, especially in the ocean interior.

中文翻译：

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内部波浪解析海洋模型的无缝单向嵌套框架

摘要 为了解决区域域中的非线性内部波浪运动，我们提出了一种单向海洋模型嵌套框架，其中非静水模型嵌套在区域模型中。嵌套方案会产生内部潮汐，这些潮汐在推动低频运动的同时，在无反射的情况下自由进出非静力学模型域。我们通过理想化的测试用例和南海的现场规模模拟来演示该方法。该方法依赖于四个参数，即低通滤波时间尺度、低频强迫时间尺度、海绵阻尼时间尺度和海绵阻尼层宽度。我们提出了基于背景分层选择这四个参数的指南。来自大型模型的内部潮汐通过非线性和非流体静力效应变得陡峭，并以单个非耦合模型所需的计算成本的一小部分来合理地匹配观测。该模型严重依赖于从大规模模型继承的背景分层，在这种情况下，这会导致嵌套模型结果中的相位速度和幅度被低估。这凸显了大型海洋模型需要纳入观测分层数据，尤其是在海洋内部。