Abstract 5 years of Systematic Envisat Advanced Synthetic Aperture Radar (ASAR) acquisitions and 8 years of observations from the Jason 2 altimeter are used to investigate the signature of the Agulhas Current on high resolution (between 1 and 5 km) satellite-derived winds. The satellite wind observations are analysed together with co-located ocean current, Sea Surface Temperature (SST) and significant wave height information. Satellite-derived winds cannot be considered current relative over the Agulhas Current. SAR and altimeter winds increase in magnitude over the Agulhas Current in all up-, down- and cross-current wind conditions, with contributions from both the ocean surface current and SST. When winds blow against the current, strong accelerations in satellite winds are observed at the Agulhas Current's inshore front, with the strongest winds observed 10 km offshore from the location of maximum SST gradient. The strong SST gradient appears to drive a thermal wind with a magnitude of about 1 m/s and which intensifies/abates the predominant alongfront winds at the Agulhas Current's northern wall. The SAR dataset shows abnormally high increases in wind speeds during up-current conditions in comparisons to the Jason-2 derived winds. We argue that these differences are caused by the inability of the CMOD_type algorithms to taken into account the wave field and provide accurate wind speed estimates in conditions where wave height exceed the expected value for a given wind speed. Our analysis suggests that wave-current interactions in regions of strong current shear produce enhanced sea surface roughness signatures and lead to artificially high estimates of SAR-derived wind speeds. There is future potential in using high resolution SAR imagery to map strong ocean current fronts and thus improve our ability to monitor ocean surface currents from space.

中文翻译：

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阿古拉斯海流在高分辨率卫星风场中的特征

摘要 5 年的系统 Envisat 高级合成孔径雷达 (ASAR) 采集和 8 年的 Jason 2 高度计观测用于研究阿古拉斯海流在高分辨率（1 至 5 公里之间）卫星风上的特征。卫星风观测与同位洋流、海面温度 (SST) 和显着波高信息一起进行分析。卫星衍生的风不能被认为是相对于阿古拉斯海流的当前风。SAR 和高度计风在所有向上、向下和横流风条件下在 Agulhas Current 上的幅度增加，同时来自海面流和 SST。当风逆流而过时，在厄加勒斯海流的近岸前沿观察到卫星风的强烈加速，从最大海温梯度位置离岸 10 公里处观察到最强风。强烈的 SST 梯度似乎驱动了大约 1 m/s 的热风，并增强/减弱了 Agulhas Current 北壁的主要沿风。SAR 数据集显示，与 Jason-2 派生的风相比，在逆流条件下风速异常高。我们认为，这些差异是由 CMOD_type 算法无法考虑波场并在波高超过给定风速的预期值的情况下提供准确的风速估计造成的。我们的分析表明，强电流切变区域中的波流相互作用会产生增强的海面粗糙度特征，并导致人为高估 SAR 衍生的风速。使用高分辨率 SAR 图像绘制强洋流前沿图，从而提高我们从太空监测洋流的能力，未来具有潜力。