Electromagnetic scattering from finite conductivity wind-roughened water surfaces

Numerical moment-method calculations of the electromagnetic backscattering from experimentally measured wind-roughened water surfaces that were previo usly made assuming perfectly conducting surfaces have been repeated taking into account the finite conductivity of sea water. The finite conductivity of the scattering medium was treated using impedance boundary conditions. C omparison with the earlier calculations shows that the backscattering drops slightly at horizontal polarization and much more dramatically at vertical polarization when the finite conductivity is considered. At small and mode rate incidence angles, the magnitudes of the scattering drops are consisten t with that predicted by the two-scale scattering model. The asymmetry in t he upwind and downwind looking scattering that results from the non-uniform distribution of the Bragg-resonant electromagnetically small-scale waves a cross the larger scale waves is unaffected by the reduced conductivity at h orizontal polarization and reduced very slightly at vertical polarization. The limitations of the two-scale model are essentially the same whether the surface is treatedwith perfect or sea-water conductivity.