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首页> 外文期刊>Journal of Physical Oceanography >Baroclinic Instabilities of the Two-Layer Quasigeostrophic Alpha Model
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Baroclinic Instabilities of the Two-Layer Quasigeostrophic Alpha Model

机译：两层拟地营养阿尔法模型的斜压不稳定性

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摘要

The class of alpha models for turbulence may be derived by applying Lagrangian averaging to the exact fluid equations and then making a closure approximation based on Taylor's hypothesis of frozen-in fluctuations. This derivation provides a closed expression for the unknown pseudomomentum in the generalized Lagrangian mean theory of Andrews and Mclntyre. In the current study, the mean effects of turbulence on baroclinic instability are explored, as determined by the two-layer quasigeostrophic-alpha model in quasigeostrophic (QG) balance. The QG-alpha model is found to lower the critical wavenumber, reduce the bandwidth of instability, and preserve the value of forcing at onset in the baroclinic case. It also preserves the fundamental dependence of baroclinic instability on the gradient of the potential vorticity. These results encourage using the alpha-model approach—based on combining Lagrangian averaging with Taylor's hypothesis closure approximations—in simulations of global ocean circulation, because this class of turbulence closure models allows Lagrangian-averaged effects of baroclinic instability to be simulated on a coarse mesh.
机译：可以通过将拉格朗日平均应用于确切的流体方程，然后基于冻结波动的泰勒假设进行闭合近似，来得出湍流的α模型类别。该推导为安德鲁斯和麦金太尔的广义拉格朗日均值理论中的未知假动量提供了一个封闭式。在当前的研究中，探索了湍流对斜压不稳定性的平均影响，这是由两层拟营养营养-α模型在拟营养营养（QG）平衡中确定的。发现QG-alpha模型可以降低临界波数，减少不稳定性的带宽，并在斜压情况下保留发病时的强迫值。它还保留了斜压不稳定性对潜在涡度梯度的基本依赖性。这些结果鼓励在基于全球海洋环流的模拟中使用基于拉格朗日平均与泰勒假设封闭近似相结合的alpha模型方法，因为此类湍流封闭模型允许在粗网格上模拟斜压不稳定性的拉格朗日平均效应。

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