海流对表面波的散射：U2H映射
Scattering of surface waves by ocean currents: the U2H map
AI总结：
针对海流引起的有效波高空间调制问题，利用海流与波群速度比的渐近小性推导出线性U2H映射，揭示了波谱各向异性在SWH异常中的关键作用，并通过WAVEWATCH III模拟验证了其预测。
摘要：
中尺度及亚中尺度的海洋湍流通过折射和散射影响表面波的传播，引起有效波高（SWH）的空间调制。我们构建了一个理论框架，将这些调制与诱发它们的海流联系起来。利用典型海流速度与波群速度之比的渐近小性，我们推导出了表面海流速度与SWH异常之间的线性映射——U2H映射。U2H映射是一个空间非局部的卷积，在傅里叶空间中可表示为与一个独立于波数矢量幅度的因子相乘。U2H映射的解析表达式表明，SWH对海流的涡旋部分和发散部分有不同的响应，以及波谱的各向异性是产生大尺度海流诱导SWH异常的关键。我们在数值上实现了U2H映射，并在理想化和实际海流配置下，通过WAVEWATCH III数值模拟检验了其预测。
英文摘要：
Ocean turbulence at meso- and submesocales affects the propagation of surface waves through refraction and scattering, inducing spatial modulations in significant wave height (SWH). We develop a theoretical framework that relates these modulations to the current that induces them. We exploit the asymptotic smallness of the ratio of typical current speed to wave group speed to derive a linear map -- the U2H map -- between surface current velocity and SWH anomaly. The U2H map is a convolution, non-local in space, expressible as a product in Fourier space by a factor independent of the magnitude of the wavenumber vector. Analytic expressions of the U2H map show how the SWH responds differently to the vortical and divergent parts of the current, and how the anisotropy of the wave spectrum is key to large current-induced SWH anomalies. We implement the U2H map numerically and test its predictions against WAVEWATCH III numerical simulations for both idealised and realistic current configurations.
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