Doppler Shifts of Backscattering Fields from One Dimensional Linear and Nonlinear Oceanic Surface by SSA-II

Based on the general framework of the second order small slope approximation (SSA-II), Doppler shifts of backscattered fields from linear and nonlinear hydrodynamic sea surfaces are predicted. Comparisons are performed at incidence angles varying from near-nadir to moderate-grazing for different radar frequencies. The predicted Doppler shifts for nonlinear hydrodynamic model are somewhat larger than the results corresponding to linear surface. Meanwhile, the dependences of the Doppler shifts on the wind speed and radar polarizations are also analyzed, and the comparisons are shown to confirm the sensitivities to the polarization and wind speed. At the same time, the results of the small perturbation method (SPM) and geometrical optics approximation (GO) are also presented for comparisons.