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首页> 外文期刊>IEEE Transactions on Geoscience and Remote Sensing >Low-grazing-angle scattering from 3-D breaking water wave crests
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Low-grazing-angle scattering from 3-D breaking water wave crests

机译：来自3-D破碎水波峰的低掠角散射

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摘要

The low-grazing-angle (high incidence angle) microwave back scattering from three-dimensional (3-D) surfaces approximating the crests of plunging-breaker water waves has been numerically found using the multilevel fast multipole algorithm. The test profiles were synthesized from a series of two-dimensional (2-D) profiles that represent the time evolution of a breaker. The results show that the strong cancellation of the vertically polarized backscattering (VV) midway through breaking that was previously identified with the 2-D profiles is maintained when the azimuthal variation of the 3-D wave is included. An optical-based model confirms that this is due to interference between back reflection from points on the forming jet and cavity of the wave. This is matched by constructive interference at horizontal polarization (HH), leading to HH-to-VV backscattering ratios that are much larger than unity. This effect remains when the azimuthal look angle is moved from directly upwave. When looking upwave, the interference disappears later in breaking when the fully formed jet shadows the cavity region. However, it returns when looking sufficiently away from directly upwave so that the cavity again becomes visible. The HH-to-VV ratios are typically greater than unity at this time, although HH cancellation can appear very late in the breaking when the round-trip distances to the jet and cavity specular points are sufficiently different.
机译：使用多级快速多极子算法，从数值上发现了接近掠过的水波波峰的三维（3-D）表面的低掠角（高入射角）微波反向散射。测试轮廓是由代表断路器时间演变的一系列二维（2-D）轮廓合成的。结果表明，当包含3-D波的方位角变化时，可以保持以前通过2-D轮廓识别的垂直极化反向散射（VV）的强烈抵消。基于光学的模型确认这是由于来自成形射流上的点的反反射与波腔之间的干扰所致。这与水平极化（HH）处的相长干涉相匹配，导致HH与VV的反向散射比远大于1。当方位角从直接上波移开时，这种效果仍然存在。当仰波时，当完全形成的射流遮盖空腔区域时，干扰会在断裂中消失。但是，当从直接上波看足够远时，它会返回，从而使空腔再次变得可见。 HH与VV的比值此时通常大于1，尽管当到射流和腔镜面反射点的往返距离足够不同时，HH取消可能会在断裂中出现得很晚。

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