Mean Lagrangian flow behavior on an open coast rip-channeled beach: A new perspective
Mean Lagrangian flow behavior on an open coast rip-channeled beach: A new perspective
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DOI：
10.1016/j.margeo.2009.09.011
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发表时间：
2010-01
期刊：
影响因子：
2.9
通讯作者：
J. MacMahan;Jeff L. Brown;Jenna A. Brown;E. Thornton;A. Reniers;T. Stanton;M. Henriquez;E. Gallagher;J. Morrison;M. Austin;T. Scott;N. Sénéchal
中科院分区：
文献类型：
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作者：
J. MacMahan;Jeff L. Brown;Jenna A. Brown;E. Thornton;A. Reniers;T. Stanton;M. Henriquez;E. Gallagher;J. Morrison;M. Austin;T. Scott;N. Sénéchal
对于裂流的公认观点是，裂流是将物质运出碎波带的有效机制。以前在天然海滩上的激流运动集中在欧拉测量与稀疏的现场压力和电流仪表阵列。在这里，第一次，空间天气的估计，撕裂电流的流动模式，涡度和拉格朗日运输行为测量在现场使用的30个位置跟踪冲浪区漂流在多个撕裂电流发生在加利福尼亚州蒙特雷的开放海岸海滩。与经典观点相反（谢泼德等人，1941年），裂流流场包括半封闭的，大规模的漩涡，保留漂流物，并导致大量的拉格朗日观测，在时间和空间上重复。在实验期间，平均每小时约有19%的漂流者在离岸流中离开冲浪区。所观察到的碎波区保留的漂流物是一致的测量从不同的开放海岸海滩撕裂流系统（14%，在中大潮特吕克Vert，法国和16%，在大潮Perranporth，英国）。蒙特利的三小时平均跨岸裂流速度为30 cm/s，峰值时均速度为40- 60 cm/s，取决于波浪和潮汐条件。偶然离开碎波带的漂流物以120 cm/s的速度被运送到离岸约2个碎波带宽度处。
The accepted view of rip currents is that they are an efficient mechanism for transporting material out of the surf zone. Previous rip current campaigns on natural beaches have focused on Eulerian measurements with sparse in situ pressure and current meter arrays. Here, for the first time, spatially synoptic estimates of rip current flow patterns, vorticity, and Lagrangian transport behavior are measured in the field using a fleet of 30 position-tracking surfzone drifters during multiple rip current occurrences on an open coast beach in Monterey, CA. Contrary to the classic view (Shepard et al., 1941), the rip current flow field consisted of semi-enclosed, large-scale vortices that retained the drifters and resulted in a high number of Lagrangian observations that are temporally and spatially repeated. Approximately 19% of the drifters deployed in the rip currents exited the surf zone per hour, on average during the experiments. The observed surf zone retention of drifters is consistent with measurements from different open coast beach rip current systems (14% at meso-macrotidal Truc Vert, France and 16% at macrotidal Perranporth, United Kingdom). The three-hour-average cross-shore rip current velocity at Monterey was 30cm/s with peak time-averaged velocities of 40–60cm/s depending on wave and tidal conditions. Drifters that episodically exited the surf zone were transported approximately 2 surf zone widths offshore at ∼20cm/s.