We consider whether it is possible in principle to retrieve the key parameters of the mixed layer in the upper ocean (its thickness, bulk eddy viscosity and the pycnocline stratification below) using a theoretical model, which assumes the surface velocity and wind stress to be known from observations. To this end we examine the dynamics of the Ekman current in the novel two-layer model of the upper ocean made of two layers with greatly differing constant eddy viscosities. The presence of stratification manifests itself through suppression of turbulence and, hence, in much smaller value of the eddy viscosity compared to the bulk eddy viscosity ve1 in the mixed layer. Within this two-layer model the general solution in terms of Green’s function has been derived and analyzed. It was found that a spectral component of frequency ω of the Ekman current on the surface “feels” the presence of the stratified layer when the mixed layer depth d is less then or comparable to the Ekman scale $$ \sqrt{2{v}_{\mathrm{e}1}/f+\omega } $$ , where f is the Coriolis parameter. Thus, under conditions of strong wind resulting in large eddy viscosity ve1, the depth of the mixed layer could be (in principle) inferred from the observations of wind and surface velocity. We conclude by stating that to retrieve the mixed layer parameters from the wind and surface velocity data, the theoretical model has to be extended by taking into account the effects of the Stokes drift due to surface waves and the possibility of intense mixing at the bottom of the mixed layer.

中文翻译：

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我们需要什么来远程探测上层海洋分层？

我们考虑是否有可能原则上使用理论模型反演上层海洋混合层的关键参数（其厚度、体积涡粘性和下面的pycnocline分层），假设表面速度和风应力是已知的从观察。为此，我们研究了上层海洋的新型两层模型中埃克曼海流的动力学，该模型由具有极大不同的恒定涡流粘度的两层组成。分层的存在通过抑制湍流而表现出来，因此，与混合层中的整体涡流粘度 ve1 相比，涡流粘度值要小得多。在这个两层模型中，已经导出并分析了格林函数方面的一般解决方案。发现当混合层深度 d 小于或与 Ekman 标度 $$ \sqrt{2{v} 相当时，表面上 Ekman 电流的频率 ω 的频谱分量“感觉到”分层层的存在_{\mathrm{e}1}/f+\omega } $$ ，其中 f 是科里奥利参数。因此，在强风导致大涡粘度 ve1 的条件下，混合层的深度可以（原则上）从风和表面速度的观察中推断出来。我们的结论是，为了从风和表面速度数据中检索混合层参数，必须通过考虑由表面波引起的斯托克斯漂移的影响以及底部强烈混合的可能性来扩展理论模型。混合层。