机载C波段全极化SAR海面风矢量反演理论研究及实验验证

机载全极化SAR海面风矢量反演研究对于近海岸复杂气象条件下风矢量探测具有重要意义. 本文从极化散射理论出发,通过分析全极化SAR探测数据与海面风矢量的关系, 设计了全极化SAR海面风矢量反演方案.依据机载SAR高机动性和全极化两个探测特点, 针对VV极化探测数据,提出了基于最大似然估计的海面风矢量反演方法,并设计了飞行实验方案; 针对VH极化探测数据,提出了通过带约束最优拟合的VH极化海面散射模型反演风速, 再利用CMOD5地球物理模型函数计算风向的海面风矢量反演方法. 利用机载全极化SAR探测的台风'海葵'边缘数据,开展了海面风矢量反演实验研究. 研究结果表明,两种风矢量反演方法均可不借助辅助信息,反演复杂气象条件下的海面风矢量. 前者反演风向、风速的均方根误差分别为18.0°, 1.8 m/s, 后者反演风向、风速的均方根误差分别为9.3°, 1.2 m/s,后者的反演精度优于前者. 这是因为VH极化归一化雷达截面与风向和雷达入射角无关,仅与风速密切相关, 更适合复杂气象条件下的海面风矢量反演. 关键词： 机载全极化SAR 海面风矢量 理论研究 实验验证

Theoretical research and experimental verification for ocean surface wind vector retrieval from airborne C-band fully polarimetric SAR

Ocean surface wind vector retrieval research on airborne fully polarimetric SAR (synthetic aperture radar) is of great significance for wind vector sounding under complex weather conditions near the coast. Starting from polarization scattering theory, we designed an ocean surface wind vector retrieval scheme for fully polarimetric SAR, by analyzing the relationship between fully polarimetric SAR sounding data and ocean surface wind vector. According to the high mobility and fully polarimetric two sounding characteristics of airborne SAR, firstly, we presented an ocean surface wind vector retrieval method based on maximum likelihood estimates for VV-polarized sounding data, and designed the flight experiment scheme. Secondly, we proposed an ocean surface wind vector retrieval method for VH-polarized sounding data, retrieved wind speed by VH-polarized ocean surface scattering model from optimum fitting with constraints, and calculated wind direction by CMOD5 geophysical model function. Using typhoon 'Haikui' edge sounding data from airborne fully polarimetric SAR, we carried out the ocean surface wind vector retrieval experimental research. Results show that two wind vector retrieval methods can retrieve ocean surface wind vector under complex weather conditions without auxiliary information. Wind direction and wind speed retrieval root mean square errors of the former are 18.0°, 1.8 m/s, wind direction and wind speed retrieval root mean square errors of the latter are 9.3°, 1.2 m/s, and the accuracy of the latter is better than that of the former. The VH-polarized normalized radar cross section is more suitable for ocean surface wind vector retrieval under complex weather conditions, because it is independent of wind direction and radar incidence angle but has a linear relationship with respect to wind speed.
Keywords： airborne fully polarimetric SAR ocean surface wind vector theoretical research experimental verification