Characteristics of Langmuir Turbulence in the Ocean Mixed Layer
Characteristics of Langmuir Turbulence in the Ocean Mixed Layer
复制标题
DOI：
10.1175/2009jpo4119.1
复制
发表时间：
2009-08-01
影响因子：
3.5
通讯作者：
Belcher, Stephen E.
中科院分区：
文献类型：
--
作者：
Grant, Alan L. M.;Belcher, Stephen E.
本文采用大涡模拟（LES）方法，通过紊流动能（TKE）预算来研究Langmuir湍流的特性。在分析TKE预算的基础上，提出了Langmuir湍流的速度标度。速度尺度取决于摩擦速度和与波场相关的表面斯托克斯漂移。当波场的Stokes漂移与表面摩擦速度相比足够大时，标度导致了独特的无因次耗散率和速度分量方差曲线。这种标度的存在表明，Langmuir湍流可以被视为一种独立的湍流状态，而不是剪切驱动湍流的修正。将LES结果与观测结果进行比较，但由于缺乏有关波场的信息，这些结果主要限于比较剖面形状。LES剖面的形状与观测剖面一致。Langmuir湍流的耗散长度尺度与剪切驱动边界层的耗散长度尺度相似。除此之外，不可能使用可用数据直接测试所建议的扩展。混合层底部的夹带比正常剪切湍流明显增强。
This study uses large-eddy simulation (LES) to investigate the characteristics of Langmuir turbulence through the turbulent kinetic energy (TKE) budget. Based on an analysis of the TKE budget a velocity scale for Langmuir turbulence is proposed. The velocity scale depends on both the friction velocity and the surface Stokes drift associated with the wave field. The scaling leads to unique profiles of nondimensional dissipation rate and velocity component variances when the Stokes drift of the wave field is sufficiently large compared to the surface friction velocity. The existence of such a scaling shows that Langmuir turbulence can be considered as a turbulence regime in its own right, rather than a modification of shear-driven turbulence.Comparisons are made between the LES results and observations, but the lack of information concerning the wave field means these are mainly restricted to comparing profile shapes. The shapes of the LES profiles are consistent with observed profiles. The dissipation length scale for Langmuir turbulence is found to be similar to the dissipation length scale in the shear-driven boundary layer. Beyond this it is not possible to test the proposed scaling directly using available data. Entrainment at the base of the mixed layer is shown to be significantly enhanced over that due to normal shear turbulence.