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首页> 外文期刊>Journal of Physical Oceanography >Lagrangian Investigation of Wave-Driven Turbulence in the Ocean Surface Boundary Layer
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Lagrangian Investigation of Wave-Driven Turbulence in the Ocean Surface Boundary Layer

机译：海洋表面边界层中波驱动湍流的拉格朗日研究

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Turbulent processes in the ocean surface boundary layer (OSBL) play a key role in weather and climate systems. This study explores a Lagrangian analysis of wave-driven OSBL turbulence, based on a large-eddy simulation (LES) model coupled to a Lagrangian stochastic model (LSM). Langmuir turbulence (LT) is captured by Craik-Leibovich wave forcing that generates LT through the Craik-Leibovich type 2 (CL2) mechanism. Breaking wave (BW) effects are modeled by a surface turbulent kinetic energy flux that is constrained by wind energy input to surface waves. Unresolved LES subgrid-scale (SGS) motions are simulated with the LSM to be energetically consistent with the SGS model of the LES. With LT, Lagrangian autocorrelations of velocities reveal three distinct turbulent time scales: an integral, a dispersive mixing, and a coherent structure time. Coherent structures due to LT result in relatively narrow peaks of Lagrangian frequency velocity spectra. With and without waves, the high-frequency spectral tail is consistent with expectations for the inertial subrange, but BWs substantially increase spectral levels at high frequencies. Consistently, over short times, particle-pair dispersion results agree with the Richardson-Obukhov law, and near-surface dispersion is significantly enhanced because of BWs. Over longer times, our dispersion results are consistent with Taylor dispersion. In this case, turbulent diffusivities are substantially larger with LT in the crosswind direction, but reduced in the along-wind direction because of enhanced turbulent transport by LT that reduces mean Eulerian shear. Our results indicate that the Lagrangian analysis framework is effective and physically intuitive to characterize OSBL turbulence.
机译：海洋表面边界层（OSBL）中的湍流过程在天气和气候系统中起着关键作用。这项研究基于大涡模拟（LES）模型和拉格朗日随机模型（LSM），探索了波驱动OSBL湍流的拉格朗日分析。 Langmuir湍流（LT）由Craik-Leibovich波浪强迫捕获，后者通过Craik-Leibovich 2型（CL2）机制生成LT。破波（BW）效果由表面湍动能通量建模，该动能通量受输入到表面波的风能约束。未解决的LES亚网格规模（SGS）运动是使用LSM模拟的，与LES的SGS模型在能量上一致。使用LT，速度的拉格朗日自相关揭示了三个不同的湍流时间尺度：积分，分散混合和相干结构时间。 LT导致的相干结构导致拉格朗日频率谱的峰值相对较窄。有无波时，高频频谱尾部与惯性子范围的预期一致，但BW实质上增加了高频下的频谱水平。一致地，在短时间内，粒子对色散结果与Richardson-Obukhov定律一致，并且由于BW，近表面色散显着增强。在更长的时间内，我们的色散结果与泰勒色散一致。在这种情况下，湍流扩散率随着LT在侧风方向上的增大而大，但在顺风方向上减小，这是因为LT增强了湍流传输，从而减小了平均欧拉剪切力。我们的结果表明，拉格朗日分析框架可有效且直观地表征OSBL湍流。

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