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首页> 外文期刊>Journal of Physical Oceanography >Small-Scale Dispersion in the Presence of Langmuir Circulation
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Small-Scale Dispersion in the Presence of Langmuir Circulation

机译：朗缪尔环流下的小尺度色散

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We present an analysis of ocean surface dispersion characteristics, on 1-100-m scales, obtained by optically tracking a release of O(600) bamboo plates for 2 h in the northern Gulf of Mexico. Under sustained 5-6 m s(-1) winds, energetic Langmuir cells are clearly delineated in the spatially dense plate observations. Within 10 min of release, the plates collect in windrows with 15-m spacing aligned with the wind. Windrow spacing grows, through windrow merger, to 40 m after 20 min and then expands at a slower rate to 50 m. The presence of Langmuir cells produces strong horizontal anisotropy and scale dependence in all surface dispersion statistics computed from the plate observations. Relative dispersion in the crosswind direction initially dominates but eventually saturates, while downwind dispersion exhibits continual growth consistent with contributions from both turbulent fluctuations and organized mean shear. Longitudinal velocity differences in the crosswind direction indicate mean convergence at scales below the Langmuir cell diameter and mean divergence at larger scales. Although the second-order structure function measured by contemporaneous GPS-tracked surface drifters drogued at similar to 0.5 m shows persistent r(2/3) power law scaling down to 100-200-m separation scales, the second-order structure function for the very near surface plates observations has considerably higher energy and significantly shallower slope at scales below 100 m. This is consistent with contemporaneous data from undrogued surface drifters and previously published model results indicating shallowing spectra in the presence of direct wind-wave forcing mechanisms.
机译：我们通过光学跟踪墨西哥湾北部2小时的O（600）竹板释放，对1-100米尺度的海洋表面弥散特征进行了分析。在持续的5-6 m s（-1）风下，在空间密集的板块观测中清楚地描绘出高能Langmuir细胞。在释放后的10分钟内，这些板块以15米的间距与风对齐排列成行。通过合并成行，成行间距在20分钟后增加到40 m，然后以较慢的速度扩展到50 m。朗格缪尔细胞的存在会在由板块观测值计算出的所有表面弥散统计数据中产生强烈的水平各向异性和尺度依赖性。逆风方向上的相对色散最初占主导地位，但最终达到饱和，而顺风方向的色散表现出持续的增长，这与湍流波动和有组织的平均切变的贡献一致。侧风方向的纵向速度差异表示在Langmuir像元直径以下的尺度上的平均收敛，在更大尺度上的平均发散。尽管同时GPS跟踪的表面漂移器在类似0.5 m的位置上滴落而测得的二阶结构函数显示出持续的r（2/3）幂定律可缩小至100-200-m的分离尺度，但对于在100 m以下的尺度上，非常靠近地表的平板观测到的能量更高，坡度也明显更浅。这与来自未淤积的表面漂移物的同期数据一致，并且先前公开的模型结果表明在存在直接风浪强迫机制的情况下光谱变浅。

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