Surfzone Vorticity

破碎的波浪在传递动量的同时消散能量，迫使水朝着波浪传播的方向前进。在冲浪区的浅水中，时间平均的波浪驱动的强迫提高了海岸线附近的水位，在倾斜入射的海浪的情况下，驱动了沿岸的水流。由此产生的环流模式包括丰富的涡旋和漩涡。表面带涡流被认为是由沿岸剪切流的不稳定性、海面的波群调制、破碎波的末端以及与复杂的水深测量相互作用的洋流产生的。这个项目将通过一套独特的高空间分辨率的遥感和现场传感器对海流的估计来解决这些假设，这些估计是在先前的实地研究中获得的，包括广泛的波浪条件和水深测量。现有的对海浪、环流模式和基本水深的现场观测将被用来检验从数值研究中得出的关于海浪涡度的假设。这些假设包括：(1)在近岸可变海底，表面带涡度的主要空间尺度取决于下伏水深的空间尺度，而这些大尺度涡旋与海底的非均质性有关；(2)小的空间尺度涡度还取决于在破碎波末端注入水柱的涡度，该涡量随着波场的定向传播而增加；(3)在高能条件下，沿岸流的动量可以克服引起复杂环流模式的力(例如测深引起的压力梯度)，从而导致沿岸均匀流动，大尺度涡度显著减少。虽然这里使用的数据来自特定的现场，但十年来观察到的广泛的海浪和水深条件允许开发适用于许多地点的表面带涡度气候学。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Breaking waves dissipate energy while transferring momentum that forces water in the direction of wave propagation. In the shallow water of the surf zone the time-averaged wave-driven forcing raises water levels near the shoreline and, in the case of obliquely incident waves, drives alongshore currents. The resulting circulation patterns include a rich field of eddies and vortices. Surfzone eddies have been hypothesized to be generated by instabilities of sheared alongshore currents, by wave-group modulations of the sea surface, by the ends of breaking waves, and by currents interacting with complex bathymetry. This project will address these hypotheses with a unique suite of high spatial resolution estimates of currents from remote sensing and in situ sensors obtained during prior field studies that include a wide range of wave conditions and bathymetries.Existing extensive field observations of surfzone waves, circulation patterns, and underlying bathymetry will be used to test hypotheses about surfzone vorticity that were derived from numerical studies. These hypotheses include: (1) on an alongshore variable seafloor, the dominant spatial scales of surfzone vorticity depend on spatial scales of the underlying bathymetry, and these large-scale eddies are tied to the seafloor inhomogeneities; (2) small spatial-scale vorticity also depends on the vorticity injected into the water column at the ends of breaking waves, which increases with the directional spread of the wave field; (3) during energetic conditions, the momentum of alongshore currents can overcome forces (such as bathymetry-induced pressure gradients) that cause complex circulation patterns, resulting in alongshore-uniform flow with significantly reduced large-scale vorticity. Although the data used here are from a specific field site, the wide range of wave and bathymetric conditions observed over a decade allows development of a surfzone vorticity climatology that will be applicable at many locations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.