Abstract The ability of high-resolution synthetic aperture radar (SAR) to detect marine atmospheric boundary layer (MABL) roll-induced roughness modulation of the sea surface wave field is well known. This study presents SAR measurements of MABL rolls using global coverage data collected by the European Space Agency's C-band Sentinel-1A satellite in 2016–2017. An automated classifier is used to identify likely roll events from more than 1.3 million images that were acquired at two incidence angles of 23° and 36.5° in either VV or HH polarization. Characteristics of the detected rolls are examined for different wind speeds, polarizations, incidence and relative azimuth angles. Roll detection counts are much higher at the higher incidence angle and nearly equivalent for VV and HH polarizations. Detection depends strongly on the relative azimuth with roll detection rates at crosswind being 3–10 times lower than for up- or downwind. All data show a low wind speed threshold near 2 m s−1 and that rolls are most commonly observed at wind speeds near 9 m s−1. For all viewing configurations, we find that rolls induce a wide range of mean surface wind speed modulation with the most frequent value being 8% (±3.5%). Roll detection at crosswind is associated with stronger roll-induced surface wind enhancement. Dependencies of roll detection on the incidence and relative azimuth angles are consistent with rapid short-scale wind-wave adjustments to the roll-induced surface wind gusts. These cm-scale waves are highly directional and provide limited crosswind backscatter at shallower incidence angles. The same roll-induced surface forcing is thus not equally detectable at all viewing geometries or polarizaions. Stronger and possibly longer-duration wind forcing is likely needed to produce detectable roll-induced modulations at crosswind.

中文翻译：

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使用 Sentinel-1 SAR 数据评估海洋大气边界层滚动检测

摘要 高分辨率合成孔径雷达 (SAR) 探测海洋大气边界层 (MABL) 横摇引起的海面波场粗糙度调制的能力是众所周知的。本研究使用欧洲航天局 C 波段 Sentinel-1A 卫星在 2016-2017 年收集的全球覆盖数据展示了 MABL 滚动的 SAR 测量结果。自动分类器用于从超过 130 万张图像中识别可能的侧倾事件，这些图像是在 VV 或 HH 偏振中以 23° 和 36.5° 两个入射角采集的。针对不同的风速、偏振、入射角和相对方位角检查检测到的滚轮的特性。在更高的入射角下，滚动检测计数要高得多，并且对于 VV 和 HH 偏振几乎相等。检测很大程度上取决于相对方位角，侧风时的横滚检测率比顺风或顺风低 3-10 倍。所有数据都显示 2 m s-1 附近的低风速阈值，并且在 9 m s-1 附近的风速下最常观察到侧倾。对于所有观察配置，我们发现滚动会引起大范围的平均表面风速调制，最常见的值为 8% (±3.5%)。侧风下的侧倾检测与更​​强的侧倾诱导表面风增强相关。滚转检测对入射角和相对方位角的依赖性与对滚转引起的表面阵风的快速短尺度风波调整一致。这些厘米级的波是高度定向的，并在较浅的入射角下提供有限的侧风反向散射。因此，在所有观察几何形状或极化情况下，不能同样检测到相同的滚动引起的表面力。可能需要更强且可能持续时间更长的风力来在侧风中产生可检测的滚转诱导调制。