Development and validation of an ocean wave retrieval algorithm for VV-polarization Sentinel-1 SAR data
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摘要: 本文的目的是研究VV极化Sentinel-1合成孔径雷达图像反演得到海浪要素的准确性,包括有效波高(SWH)和平均波周期(MWP)。本研究利用浮标实测数据获得风向,并通过一种新的C波段地球物理(GMF)模型C-SARMOD来反演风速。接着,利用上述反演得到的风速,采用参数化初猜测谱算法(PFSM)反演SWH和MWP。我们在美国沿岸收集了45幅VV极化Sentinel-1 SAR图像,并从中选取52幅覆盖有浮标数据的子图像。将反演获得的结果与浮标实测结果进行对比,结果显示风速、SWH、MWP的标准差(STD)分别为1.6 m/s、0.54 m和2.14 s。此外,补充50幅中国沿海的SAR图像,采用PFSM算法,对比欧洲中长期天气预报中心(ECMWF)再分析波浪数据,反演得到的SWH和MWP的STD分别为0.67 m和2.21 s。该结果表明,通过使用C-SARMOD反演得到的风速,结合PFSM算法从VV极化Sentinel-1 SAR图像中反演海浪要素方法切实可行。
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关键词:
- 风速 /
- 有效波高 /
- 平均波周期 /
- Sentinel-1合成孔径雷达
Abstract: The purpose is to study the accuracy of ocean wave parameters retrieved from C-band VV-polarization Sentinel-1 Synthetic Aperture Radar (SAR) images, including both significant wave height (SWH) and mean wave period (MWP), which are both calculated from a SAR-derived wave spectrum. The wind direction from in situ buoys is used and then the wind speed is retrieved by using a new C-band geophysical model function (GMF) model, denoted as C-SARMOD. Continuously, an algorithm parameterized first-guess spectra method (PFSM) is employed to retrieve the SWH and the MWP by using the SAR-derived wind speed. Forty–five VV-polarization Sentinel-1 SAR images are collected, which cover the in situ buoys around US coastal waters. A total of 52 subscenes are selected from those images. The retrieval results are compared with the measurements from in situ buoys. The comparison performs good for a wind retrieval, showing a 1.6 m/s standard deviation (STD) of the wind speed, while a 0.54 m STD of the SWH and a 2.14 s STD of the MWP are exhibited with an acceptable error. Additional 50 images taken in China’s seas were also implemented by using the algorithm PFSM, showing a 0.67 m STD of the SWH and a 2.21 s STD of the MWP compared with European Centre for Medium-range Weather Forecasts (ECMWF) reanalysis grids wave data. The results indicate that the algorithm PFSM works for the wave retrieval from VV-polarization Sentinel-1 SAR image through SAR-derived wind speed by using the new GMF C-SARMOD. -
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