各向异性海面全极化微波双站散射的仿真与分析

Simulation and analysis of fully polarimetric microwave bistatic scattering from an anisotropic ocean surface

为了解各向异性随机粗糙海面的微波双站散射机制及其特性,本文利用解析近似的积分方程模型以及一种改进的半经验海浪谱模型实现了对各向异性随机粗糙海面的全极化微波散射仿真模拟,并与卫星观测数据、经验的地球物理模式函数及已有的解析近似散射模型仿真结果进行了对比,验证了仿真结果的可行性和准确性。利用该模型分析了入射波频率、入射角、极化方式、海面风速及风向等参数对各向异性海面双站散射的影响。模拟结果表明,在不同的入射角、散射角及方位角等观测几何条件下,海面不同波段的双站散射表现出不同的空间散射特性,且对风速、风向等海面动力学参数表现出不同的敏感性,以L波段为例,海面向后半球双站散射在各个极化方式下都对风速较为敏感,而在同极化方式下,其对风向的响应在中低风速和高风速条件下相反,整体而言,低风速下海面双站散射对风向更为敏感。这表明对于海面动力参数的反演,双站散射可以提供比传统单站雷达后向散射更丰富的物理信息。本文探讨了各向异性海面微波双站散射特性,为基于主动式及分布式微波传感器的海洋动力参数遥感反演提供了理论分析基础。

In order to explore the possibilities of ocean geophysical parameter retrievals with bistatic scattering signals,thorough understanding of ocean bistatic scattering,both its spatial feature and sensitivity to geophysical parameters,will be crucial and meaningful.In this study,the integral equation model(IEM)combined with an improved directional sea spectrum are adopted to simulate the fully polarimetric microwave bistatic scattering from an anisotropic ocean surface.By comparing the simulation results with satellite observations,the geophysical model function CMOD5 and the simulations of Small Slope Approximation(SSA),the practicability of proposed method in simulating ocean surface microwave scattering is validated.Furthermore,the sensitivities of sea surface bistatic scattering to several geometric and physical parameters,i.e.,microwave frequency,incidence,polarization,wind speed and direction,are investigated with this method.The simulation results indicate that ocean surface bistatic scatterings show different spatial scattering characteristics under different observation geometry,and have various sensitivities to ocean dynamic parameters,namely,wind speed and wind direction.Specifically,L-band bistatic scatterings in the backward directions are more sensitive to sea surface wind speed,and the co-polarized ones have opposite responses to wind direction changes for low and high wind speed.At low wind speeds,L-band ocean surface bistatic scatterings have higher sensitivities to wind direction.It is also found that the bistatic scattering contains more spatial information than the conventional monostatic scattering.This work expands the understanding of ocean surface scattering in fully bistatic configuration and explore the potential of parameter retrieval with bistatic radar observations.