Structure and Instability of the Ekman Spiral in the Presence of Surface Gravity Waves
Structure and Instability of the Ekman Spiral in the Presence of Surface Gravity Waves
复制标题
表面重力波存在下埃克曼螺旋的结构和不稳定性
DOI：
10.1175/1520-0485(1995)025
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发表时间：
1995
影响因子：
3.5
通讯作者：
R. Weller
中科院分区：
文献类型：
--
作者：
A. Gnanadesikan;R. Weller
通过考虑速度结构，考察了维持混合层的物理过程。非层结混合层内部的低频Ekman响应比用再现温度结构的涡粘性模式所预测的要小得多。然而，与将混合层参数化为板的模型预测的相比，响应的剪切力更大。通过考虑无限大的表面重力波列对平均Ekman螺线的影响来寻求解释。在某些实际条件下，仅假设小尺度扩散所预测的Ekman螺线对波流相互作用驱动的朗缪尔环流是很不稳定的。在北半球，这些单体都朝向风的右侧，这是在最大化波流强迫、最大化这种强迫产生单体的效率和最小化交叉单体切变之间取得平衡的结果。这些电池能够取代小规模的湍流。
Abstract The physical processes responsible for maintaining the mixed layer am examined by considering the velocity structure. The low-frequency Ekman response in the interior of unstratified mixed layers is much less sheared than is predicted using eddy viscosity models that reproduce the temperature structure. However, the response is more sheared than predicted by models that parameterize the mixed layer as a slab. An explanation is sought by considering the effect of an infinite train of surface gravity waves on the mean Ekman spiral. For some realistic conditions, the Ekman spiral predicted by assuming small-scale diffusion alone is strongly unstable to Langmuir cells driven by wave-current interaction. In the Northern Hemisphere, these cells are oriented to the right of the wind, the result of a balance between maximizing the wave-current forcing, maximizing the efficiency of this forcing in producing cells, and minimizing the crosscell shear. The cells are capable of replacing small-scale turbulent...