Polarimetric Simulations of Bistatic Scattering From Perfectly Conducting Ocean Surfaces With 3 m/s Wind Speed at L-Band

Abstract

In this paper, we simulate the fully polarimetric bistatic scattering behavior resulted from the interaction of electromagnetic wave with all scales of ocean waves, with a focus on the dependence of such behavior on wind direction and incidence angle. The numerical approach is our recently developed second stochastic degree iterative algorithm with sparse matrix (SM) and Chebyshev approximation. The illuminated area is 86 wavelength ${\times}$ 86 wavelength, which represents about 2.5 dominant wavelengths for a 3 m/s Elfouhaily spectrum at L-band, implying that the effect of gravity wave has been adequately included. The total number of surface unknowns is 2 130 048. Our numerical treatment is capable of pushing down the numerical noise floor to below $-50\;\text{dB}$ and providing excellent agreement of cross-polarized backscattering coefficients, hence the fulfillment of the reciprocity relation. The numerical results confirm the interesting bistatic patterns for the copolarized signals such as the change with the wind direction of shape of a strong signal region (SSR) which includes the specular direction and its vicinity, and the more visually identifiable double-peaked mound at lower incidence angle. In addition, the results reveal a deep signal level valley across elevation seen by either polarization, and quite different behaviors of HH and VV outside of the vicinity of specular direction. The bistatic scattering behaviors of the two cross-polarized signals appear generally similar. The polarization ratio (PR) is larger than unity except for a very limited scattering range around the specular direction, and rises quickly with scattering angles, in both the forward and backward directions.