Surfzone Vorticity

破碎的波浪在传递动量的同时耗散了能量，而动量迫使水沿着波浪传播的方向运动。在冲浪区的浅水区，时间平均波浪驱动力提高了海岸线附近的水位，在波浪斜入射的情况下，推动了沿岸的水流。由此产生的环流模式包括丰富的涡流和涡旋场。据推测，表面漩涡是由沿岸剪切流的不稳定性、海面的波群调制、破碎波的末端以及洋流与复杂的水深测量相互作用产生的。该项目将通过一套独特的高空间分辨率估计值来解决这些假设，这些估计值来自遥感和在先前的实地研究中获得的原位传感器，包括广泛的波浪条件和水深测量。现有的广泛的表面带波、环流模式和海底测深的实地观测将用于检验从数值研究中得出的关于表面带涡度的假设。这些假设包括：(1)在沿海变化的海底，表层涡度的主要空间尺度取决于海底测深的空间尺度，这些大尺度涡旋与海底的不均匀性有关；(2)小的空间尺度涡量还取决于破碎波末端注入水柱的涡量，随着波场的定向传播而增加；(3)在高能条件下，沿岸水流的动量可以克服引起复杂环流模式的力（如测深引起的压力梯度），导致大尺度涡度显著降低的沿岸均匀流动。虽然这里使用的数据是来自一个特定的现场，但十多年来观察到的广泛的波浪和水深条件，使地表涡度气候学得以发展，这将适用于许多地方。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.