Principle Study On Simulation Platform Of Ocean Surface Imaged By SAR

Based on the studies of radar backscattering model and current-wave interaction, a principle simulation platform of ocean surface imaged by SAR is developed, which can simulate radar backscattering coefficients when provided with current field and wind field.This platform is composed of two parts: one is hydrodynamic model which describes the modulation of Bragg wave by current and the other is radar backscattering model which describes the interaction between electromagnetic wave and Bragg wave. The hydrodynamic model is established on the basis of wave action equation which can be solved by the ray tracing method proposed by R. Romeiser. The numerical algorithm is programmed to compute wave spectrum modulated by surface currents. The spectrum coincides quite well in high frequency area with results of M4S. The radar backscattering model is established on the basis of a stochastic multi-scale model and its numerical algorithm proposed by W. Plant. In this model, radar backscattering coefficients are computed with different radar parameters and wind conditions, and then their influences on SAR images are analyzed.In this paper, corresponding radar backscattering coefficients under ERS-2/SAR parameters of the internal wave generated by simulating a moving submarine are computed using this platform. Results show that the convergence and divergence features of currents can be reproduced reasonably, and meanwhile radar backscattering coefficient images with different radar frequencies, polarizations, incidence angles and wind speeds are simulated and results are agreed with former literatures: the intensity of images of C and X bands look similar and X band is a little larger than C band; VV polarization is larger than HH polarization; the backscattering reduces when incidence angle increases and augments when wind speed increases, but features of currents become weak. The influences of different scattering models (including Bragg model, improved composite surface model and stochastic multi-scale model) on the SAR image are also studied. With the same current and wind, results show that the stochastic multi-scale model agrees with the improved composite surface model and both of them are better than the Bragg model because the latter one underestimates the radar backscattering.