Surface gravity wave effects in the oceanic boundary layer: large-eddy simulation with vortex force and stochastic breakers
Surface gravity wave effects in the oceanic boundary layer: large-eddy simulation with vortex force and stochastic breakers
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DOI：
10.1017/s002211200700897x
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发表时间：
2007-11
影响因子：
3.7
通讯作者：
P. Sullivan;James C. McWilliams;W. Melville
中科院分区：
文献类型：
--
作者：
P. Sullivan;James C. McWilliams;W. Melville
对风生稳定层结的中纬海洋表面湍流边界层进行了数值模拟，模拟结果表明，在特定的海面重力波场存在的情况下，风致稳定层结的中纬海洋表面湍流边界层存在。在与平均风速接近平衡的情况下，重力波具有典型的测量条件的宽波数和频谱。模拟模式基于(I)波浪对平均边界层流的保守动力效应的渐近理论和(Ii)由破碎波浪场中的冲量和能量通量的随机表示所强迫的边界层。与没有波浪影响并由等效平均表面应力强迫的模拟相比，波浪对平均水流剖面和湍流统计的影响都是深远的。根据前人的研究，由于波浪平均涡旋力的部分组合，朗缪尔环流使垂直的动量和物质集中的涡通量更加有效和非局地(即在地表附近具有负的涡粘性)，它们与破碎物结合增加了湍流能量和耗散率。它们还结合在一个意想不到的正反馈中，其中由破碎物产生的涡度孕育了新的朗缪尔环流，并激发了一股穿透边界层的深而强的间歇性下流急流，增加了层底部的物质夹带率。波龄越小，平均风速越大，对边界层的影响越大。
The wind-driven stably stratified mid-latitude oceanic surface turbulent boundary layer is computationally simulated in the presence of a specified surface gravity-wave field. The gravity waves have broad wavenumber and frequency spectra typical of measured conditions in near-equilibrium with the mean wind speed. The simulation model is based on (i) an asymptotic theory for the conservative dynamical effects of waves on the wave-averaged boundary-layer currents and (ii) a boundary-layer forcing by a stochastic representation of the impulses and energy fluxes in a field of breaking waves. The wave influences are shown to be profound on both the mean current profile and turbulent statistics compared to a simulation without these wave influences and forced by an equivalent mean surface stress. As expected from previous studies with partial combinations of these wave influences, Langmuir circulations due to the wave-averaged vortex force make vertical eddy fluxes of momentum and material concentration much more efficient and non-local (i.e. with negative eddy viscosity near the surface), and they combine with the breakers to increase the turbulent energy and dissipation rate. They also combine in an unexpected positive feedback in which breaker-generated vorticity seeds the creation of a new Langmuir circulation and instigates a deep strong intermittent downwelling jet that penetrates through the boundary layer and increases the material entrainment rate at the base of the layer. These wave effects on the boundary layer are greater for smaller wave ages and higher mean wind speeds.