Interaction of Langmuir Turbulence and Inertial Currents in the Ocean Surface Boundary Layer under Tropical Cyclones
Interaction of Langmuir Turbulence and Inertial Currents in the Ocean Surface Boundary Layer under Tropical Cyclones
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DOI：
10.1175/jpo-d-17-0258.1
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发表时间：
2018-09
影响因子：
3.5
通讯作者：
Dong Wang;T. Kukulka;B. Reichl;T. Hara;I. Ginis;P. Sullivan
中科院分区：
文献类型：
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作者：
Dong Wang;T. Kukulka;B. Reichl;T. Hara;I. Ginis;P. Sullivan
基于大涡模拟方法，研究了热带气旋(TCS)作用下海洋表面边界层(OSBL)和朗缪尔湍流(LT)对极风和复杂波浪强迫的响应。驱动LT的斯托克斯漂移矢量是从频谱波模拟中确定的。在最大TC风期间，LT显著增强了冷水的夹带，导致OSBL迅速加深。这与相对较强的波浪强迫、较弱的惯性流和较浅的OSBL深度相吻合，通过较小的比率测量，其中表示斯托克斯漂移衰减长度尺度。它直接影响到近地表，其深度是根据速度变化的增强各向异性比估计的。在OSBL快速加深的过程中，与LT成正比，LT有效地在相干结构中传输动量，局部增强了受LT控制的较深剪切驱动层的剪切不稳定性。TC通过后，惯性流越强越大，而惯性流越浅且与之成正比。在此期间，受LT影响的表层太浅，不能直接影响更深的剪切驱动层，因此两层是弱耦合的。同时，LT减少了在后期表面能量输入中起关键作用的表面电流。这两个因素导致TC通过后TKE水平和夹带率相对较小。因此，我们的研究表明，在TC条件下，需要考虑惯性流才能完全理解LT及其对OSBL动力学的影响。
Based on a large-eddy simulation approach, this study investigates the response of the ocean surface boundary layer (OSBL) and Langmuir turbulence (LT) to extreme wind and complex wave forcing under tropical cyclones (TCs). The Stokes drift vector that drives LT is determined from spectral wave simulations. During maximum TC winds, LT substantially enhances the entrainment of cool water, causing rapid OSBL deepening. This coincides with relatively strong wave forcing, weak inertial currents, and shallow OSBL depth , measured by smaller ratios of , where denotes a Stokes drift decay length scale. LT directly affects a near-surface layer whose depth is estimated from enhanced anisotropy ratios of velocity variances. During rapid OSBL deepening, is proportional to , and LT efficiently transports momentum in coherent structures, locally enhancing shear instabilities in a deeper shear-driven layer, which is controlled by LT. After the TC passes, inertial currents are stronger and is greater while is shallower and proportional to . During this time, the LT-affected surface layer is too shallow to directly influence the deeper shear-driven layer, so that both layers are weakly coupled. At the same time, LT reduces surface currents that play a key role in the surface energy input at a later stage. These two factors contribute to relatively small TKE levels and entrainment rates after TC passage. Therefore, our study illustrates that inertial currents need to be taken into account for a complete understanding of LT and its effects on OSBL dynamics in TC conditions.