Polarization Dependence of Radar Contrast for Sea Surface Oil Slicks

The polarization dependence of microwave radar image contrast between clean sea and oil slicks is investigated in the framework of a two-scale scattering model. The Cox & Munk large-scale slope probability density function (PDF) is used for a clean sea surface and for the oil slicks along with the Elfouhaily power spectrum of sea roughness. The sea roughness modification in the slicks is modeled by cutting off the power spectrum at a sea wavelength of an order of several decimeters and by nulling the skewness coefficients in the Cox & Munk slope PDF. It is shown that the contrast in the radar image of sea surface slicks obtained at HH and HV polarizations exceeds significantly that at VV polarization; the polarization-dependent part of the contrast increases as the grazing angle decreases and the wind speed and the radar frequency increase (at K_u band it exceeds the one at C band); the contrast is azimuth dependent, and it differs for upwind and downwind directions as a result of the skewness of the slope PDF.