| ZHANG Yi,JIANG Xingwei,SONG Qingtao,LIN Mingsen,XIE Xuetong. 2014. Coastal wind field retrieval from polarimetric synthetic aperture radar. Acta Oceanologica Sinica, 33(5):54－61 |
| Coastal wind field retrieval from polarimetric synthetic aperture radar |
| 全极化合成孔径雷达近岸风场反演研究 |
| Received:September 16, 2013 Revised:January 16, 2014 |
| DOI：10.1007/s13131-014-0479-5 |
| Key words:polarimetric synthetic aperture radar coastal wind field polarimetric correlation backscattering coefficients |
| 中文关键词: 全极化合成孔径雷达 近岸风场 极化相关后向散射系数 |
| 基金项目:The National Natural Science Foundation of China under contract Nos 41306186, 41076012 and 41276019; the Youth Science Fund Project of State Oceanic Administration of China. |
| Author Name | Affiliation | E-mail | | ZHANG Yi | National Satellite Ocean Application Service, State Oceanic Administration, Beijing 100081, China
Key Laboratory of Space Ocean Remote Sensing and Applications, State Oceanic Administration, Beijing 100081, China | zhangyi@mail.nsoas.gov.cn | | JIANG Xingwei | National Satellite Ocean Application Service, State Oceanic Administration, Beijing 100081, China
Key Laboratory of Space Ocean Remote Sensing and Applications, State Oceanic Administration, Beijing 100081, China | | | SONG Qingtao | National Satellite Ocean Application Service, State Oceanic Administration, Beijing 100081, China
Key Laboratory of Space Ocean Remote Sensing and Applications, State Oceanic Administration, Beijing 100081, China | | | LIN Mingsen | National Satellite Ocean Application Service, State Oceanic Administration, Beijing 100081, China
Key Laboratory of Space Ocean Remote Sensing and Applications, State Oceanic Administration, Beijing 100081, China | | | XIE Xuetong | National Satellite Ocean Application Service, State Oceanic Administration, Beijing 100081, China | |
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| Abstract: |
| Coastal winds are strongly influenced by topology and discontinuity between land and sea surfaces. Wind assessment from remote sensing in such a complex area remains a challenge. Space-borne scatterometer does not provide any information about the coastal wind field, as the coarse spatial resolution hampers the radar backscattering. Synthetic aperture radar (SAR) with a high spatial resolution and all-weather observation abilities has become one of the most important tools for ocean wind retrieval, especially in the coastal area. Conventional methods of wind field retrieval from SAR, however, require wind direction as initial information, such as the wind direction from numerical weather prediction models (NWP), which may not match the time of SAR image acquiring. Fortunately, the polarimetric observations of SAR enable independent wind retrieval from SAR images alone. In order to accurately measure coastal wind fields, this paper proposes a new method of using co-polarization backscattering coefficients from polarimetric SAR observations up to polarimetric correlation backscattering coefficients, which are acquired from the conjugate product of co-polarization backscatter and cross-polarization backscatter. Co-polarization backscattering coefficients and polarimetric correlation backscattering coefficients are obtained form Radarsat-2 single-look complex (SLC) data.The maximum likelihood estimation is used to gain the initial results followed by the coarse spatial filtering and fine spatial filtering. Wind direction accuracy of the final inversion results is 10.67 with a wind speed accuracy of 0.32 m/s. Unlike previous methods, the methods described in this article utilize the SAR data itself to obtain the wind vectors and do not need external wind directional information. High spatial resolution and high accuracy are the most important features of the method described herein since the use of full polarimetric observations contains more information about the space measured.This article is a useful addition to the work of independent SAR wind retrieval. The experimental results herein show that it is feasible to employ the co-polarimetric backscattering coefficients and the polarimetric correlation backscattering coefficients for coastal wind field retrieval. |
| 中文摘要: |
| 提出了利用全极化合成孔径雷(SAR)达观测数据中同极化后向散射系数及由同极化与交叉极化后向散射信号所获得的相关极化后向散射系数协同进行海面风场反演的方法。本文从Radarsat-2单视复数据(SLC)获取同极化和极化相关后向散射系数，并利用最大似然估计以及空间滤波等方法获得海面风矢量。与以往基于合成孔径雷达的风场反演方法相比，本文完全由SAR数据本身获得风矢量，不依赖于外部风向信息，最终反演结果风向精度为±10.67°，风速精度为±0.32m/s。本实验的结果证明了利用同极化后向散射系数和极化相关后向散射系数进行SAR风场反演的可行性，是对SAR数据独立风场反演的有益尝试。 |
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