Radar scattering of ocean surfaces at L band based on numerical solutions of maxwell equations in three-dimensions (NMM3D)

We applied the Numerical Maxwell Model in 3 Dimensions (NMM3D) to radar scattering from ocean surfaces at L band. The formulation is based on the PMCHWT surface integral equation which uses separate Green's functions for air and ocean permittivities. The Sparse Matrix Canonical Grid (SMCG) is used to compute Method of Moments (MoM) solutions in conjunction with Rao-Wilton-Glisson (RWG) basis functions with the surface electric field and surface magnetic field as the unknowns. Surface sizes used are up to 64 wavelengths by 64 wavelengths. Isotropic sea surfaces simulated using the Durden-Vesecky spectrum are studied for wind speeds ranging from 5 m/s to 10 m/s and incidence angles varying from 29° to 46°. Backscattering from NMM3D and composite two-scale model computations are compared with Aquarius satellite scatterometer estimates. Unlike the two-scale model, NMM3D does not impose separation between large scale roughness and small scale roughness elements. Results show that, in spite of using just the isotropic DV spectrum, NMM3D are in measurably better agreement with data than the composite surface model for co-polarized returns as well as the polarization ratio.