Impact of Spectral Spreading Functions on Modeling the Sea Backscatter Cross Section at Microwave Frequencies

The spectral description of the wind-roughened ocean surface usually involves an omnidirectional spectral model and an azimuthal spreading function that describes the fraction of the waves of a certain length propagating at a given angle with respect to the wind direction. A number of such functions have been introduced and refined over the years. We use the 2
^nd
-order Small Slope Approximation (SSA2) to calculate and compare the backscattered normalized radar cross sections resulting from several of them. In the process, the same Hwang omnidirectional spectrum is used. The SSA2 allows evaluating both co-polarized and cross-polarized backscattering cross sections. This study focuses on L and Ku radar bands and wind speeds between 5 and 9 m/s and covers a wide range of incidence angles. The results are compared with geophysical model functions where available.