基于双尺度模型的中等与大入射角海面微波散射场频谱特性分析.doc

  Doppler spectra of microwave scattering fields from nonlinear oceanic surface at moderate- and low-grazing 5 10 15 20 25 30 35 angles# WANG Yunhua1, ZHANG Yanmin2, CHEN Haihua1* (1. Ocean Remote Sensing Institute, Ocean University of China; 2. Department of Physics, Ocean University of China) Abstract: Results of microwave radar Doppler spectra from one dimensional (1D) nonlinear ocean surface at moderate- and low-grazing angles (LGA) are calculated by the composite surface scattering model. For the large-scale undulating surface description, the narrow-band Lagrange model is used, which takes into account the vertical and horizontal skewnesses. Moreover, the shadow and the curvature effects of large-scale waves on the Doppler spectra are also considered in our calculations. Comparisons of computed curves with experimentally measured Doppler spectra at different incidence angles and at various wind speeds show that the simulated results can fit the measured data well at moderate incident angles. From the simulations, we also find that the hydrodynamic modulation and the horizontal skewness of the large-scale waves can induce remarkable influence on Doppler shift. In addition, when the shadow and the curvature effects of large-scale waves are considered in the calculations, the Doppler shifts grow more quickly and the spectral widths become narrower at low-grazing angles. And this is consistent with the numerical results given by Toporkov et al. in nonlinear surface case. The conclusions obtained in this work seem promising for better understanding the properties of time dependent radar echoes from oceanic surfaces. Key words: Doppler spectra; scattering; Lagrange sea surface 0 Introduction Doppler spectra of electromagnetic signals backscattered from time-varying oceanic surfaces have attracted much attention, experimentally as well as theoretically [1]-[13]. This issue is of practical importance in areas of sea surface wind retrieving, sea waves monitoring,