复杂海面多波段全极化雷达后向散射机理模型研究

As the rapid advancement of multi-Frequency multi-polarization synthetic aperture radar (SAR) programs, rainfall and other complicated ocean events is observed by SAR. High-resolution SAR is a potential powerful tool for ocean observation. However, it brings some difficulties in understanding many interesting rain-related and other complicated phenomena revealed by SAR images because of low precision of current models and poor theoretical modeling of rain-wind-wave and other interactions. In addition, it is difficult to quantify estimation various scattering mechanisms contribution to the radar backscattering signals over the complicated sea surface. According to these problems, this project presents a research on theoretical modeling of multi-band qual-polarization radar backscattering for a comprehensive ocean scene.The main purposes of this study are to explore the whole process of radar electromagnetic wave scattering and radiative transfer over the complicated sea surface, which takes account scattering, attenuation, shadowing, and multiple scattering of spatially distributed volumetric and surface scatterers over the comprehensive ocean scene and establish the general physics-based scattering model for rainfall and oil film over the sea surface.These works can provide scientific reference for better understanding and interpreting various phenomena observed by SAR and it is meaningful to extend applications of the marine environment monitoring using radar observations.

随着多频率、多极化、高分辨率合成孔径雷达（SAR）系统的开发与应用，降雨和其它一些复杂海面场景被雷达成像，对复杂海洋环境下的遥感探测机理研究提出了更高要求。针对现有海面雷达散射模型多关于单一均质海面，业务化应用精度不高且复杂海面因素对雷达后向散射信号影响难以量化估计等问题，本课题提出开展对复杂海面多波段全极化雷达后向散射机理进行正向模拟研究，探索复杂海面场景下的雷达探测海面电磁波传输过程，综合考虑复杂海面场景下多种穿透和非穿透对象或体散射和面散射目标对后向散射信号影响机制，建立复杂海面雷达后向散射综合分析模型，进行降雨和油污海面各种SAR成像特征分析和解译。该研究成果为充分利用多波段多极化雷达观测数据提供理论模型支持，可扩展微波海洋遥感监测技术的应用领域，对促进我国海洋遥感科学的发展具有重要的意义。

高分辨合成孔径雷达系统发展对迫切需要明确复杂海洋环境下的遥感探测机理。本项目针对现有海面雷达散射模型多关于单一均值海面，难以量化估计复杂海面因素对雷达后向散射影响等问题，开展了复杂海面多波段全极化雷达后向散射特性模拟研究。综合考虑多波段多极化雷达探测海面散射机理，旨在发展复杂海面多波段全极化海面散射模型，重点研究了电磁波与海面相互作用机理及海面形态建模方法，从全向海谱、方向传递函数、曲率谱、高方差和斜率方差等多个方面系统分析了常用海谱，在此基础上提出了新的方向传递函数，使得二维海面在短波的描述更准确，特别是在雷达电磁波比较敏感的短重力波和毛细波范围。将多种海浪谱模型与最新的IEM/AIEM散射理论结合组建了一个海面散射机理模型。将从多种海浪谱提取的粗糙尺度参数输入统一散射模型模拟了不同入射角、风速和风向的海面雷达后向散射系数，并与L和C波段的经验地球物理模型函数以及多类型观测数据进行了对比分析，定量评价了海面粗糙尺度对雷达后向散射的贡献。深入研究降雨条件下的雨滴的散射机制，降雨和油污海面相互作用机理及对电磁波的散射效应，将降雨体散射和缓冲以及降雨和油污海面粗糙度影响关系模型引入风驱动海面散射模型，发展了复杂海面散射机理模型。分别选取降雨条件和油污海面的SAR成像典型案例数据结合发展的机理模型对复杂海面场景散射特性进行了定量分析。分析结果表明，本项目开发的复杂海面散射机理模型能够刻画复杂海面雷达散射系数在不同波段和极化方式下随入射角、方位角、风速和风向、降雨强度和油膜特性参数变化的规律。项目成果为充分利用我国已有和正在部署的多波段合成孔径雷达卫星构建形成我国自主的海洋环境监测能力奠定了基础。