An Improved Two-Scale Analytical Model for Bistatic Scattering of Wind-Driven Sea Surfaces

The two-scale model (TSM) has been widely used to calculate scattering from surfaces with multiple roughness scales. In our study, we derived an improved TSM based on the angular composite model (ACM), which expresses the calculation of the scattering coefficient as an integral over the surface angles, making it possible to accelerate the process by combining with Monte Carlo integration. In addition, any method can be employed to calculate the small-scale scattering. We use the first-order small-slope approximation model (SSA1) with wider applicability instead of the small perturbation model (SPM) to calculate the scattering contribution from small-scale rough surfaces. We analyze the roughness of short waves on anisotropic wind-driven sea surfaces, give numerical examples of horizontally polarized backscattering and bistatic scattering, taking into account the L-band and different wind speeds, and compare them with the measurement data, classic TSM (KA + SPM), facet-based TSM (KA + SSA1), closed-form two-scale model [bistatic anisotropic polarimetric TSM (BA-PTSM)], and second-order small-slope approximation model (SSA2) algorithms. The proposed bistatic scattering model is in general agreement with the classic model and is demonstrated to be more consistent with measurements at larger scattering angles and more insensitive to the cutoff wavenumber.