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首页> 外文期刊>Journal of Physical Oceanography >Inhomogeneous Turbulent Dispersion across the Nearshore Induced by Surfzone Eddies
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Inhomogeneous Turbulent Dispersion across the Nearshore Induced by Surfzone Eddies

机译：Surfzone涡流引起的近岸非均匀湍流扩散

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摘要

In various oceanic regions, drifter-derived diffusivities reach a temporal maximum and subsequently decrease. Often, these are regions of inhomogeneous eddies, however, the effect of inhomogeneous turbulence on dispersion is poorly understood. The nearshore region (spanning from the surfzone to the inner shelf) also has strong cross-shore inhomogeneous turbulence. Nearshore Lagrangian statistics are estimated from drifter trajectories simulated with a wave-resolving two-dimensional Boussinesq model with random, normally incident, and directionally spread waves. The simulation is idealized and does not include other (wind, tidal, Coriolis) processes. The eddy field cross-shore inhomogeneity affects both the mean cross-shore drift and cross- and alongshore diffusivities. Short-time diffusivities are locally ballistic, and the mean drift is toward the eddy velocity variance maximum. The diffusivities reach a maximum and subsequently decrease, that is, are subdiffusive. The diffusivity maximum and time to maximum are parameterized taking into account the eddy field inhomogeneity. At long times, the cross- and alongshore diffusivities scale as t(-1/2) and t(-1/4), respectively, which is related to the offshore decay of the eddy intensity. A diffusion equation, with a space-dependent Fickian diffusivity related to the eddy velocity variance, reproduced the short-, intermediate-, and long-time behavior of the mean drift and cross-shore diffusivity. The small Middleton parameter, indicating fixed float dispersion, suggests the Eulerian time scale can parameterize the Lagrangian time scale in this region. Although this idealized simulation had no mean currents, and thus no shear dispersion or mixing suppression, inhomogeneous turbulence effects may be relevant in other regions such as the Antarctic Circumpolar Current (ACC) and western boundary current extensions.
机译：在各个海洋区域中，漂移产生的扩散率达到了时间上的最大值，随后减小。通常，这些区域是不均匀涡流的区域，但是，人们对不均匀湍流对分散的影响知之甚少。近岸区域（从海浪区到内陆架）也具有很强的跨岸非均匀湍流。通过使用具有随机波，垂直入射波和定向波的解析波二维Boussinesq模型模拟的漂移轨迹，可以估算近岸拉格朗日统计量。模拟是理想化的，并且不包括其他（风，潮，科里奥利）过程。涡场跨岸非均质性影响平均跨岸漂流以及跨岸和沿岸扩散率。短时扩散是局部弹道的，平均漂移朝向涡流方差最大值。扩散率达到最大值并随后减小，即是亚扩散性的。考虑到涡流场的不均匀性，将最大扩散率和达到最大值的时间参数化。长期以来，跨岸和沿岸扩散系数分别为t（-1/2）和t（-1/4），这与涡旋强度的离岸衰减有关。具有与涡流速度方差有关的空间依赖的Fickian扩散率的扩散方程再现了平均漂移和跨岸扩散率的短期，中期和长期行为。小的Middleton参数表示固定的浮子分散，表明欧拉时标可以参数化该区域中的拉格朗日时标。尽管这种理想化的模拟没有平均电流，因此没有剪切分散或混合抑制，但是在其他区域，例如南极绕极电流（ACC）和西边界电流扩展，非均质湍流效应可能是相关的。

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