An empirical microwave emissivity model for a foam-covered sea

A model for computing microwave emissivity of a wind-driven foam-covered sea is presented. The effect of roughness and foam is modeled by combining early measurement results and theoretical analysis. Recent Seasat-SMMR measurements are used to fine tune the model and derive an "effective" fractional foam coverage expression in terms of frequency and wind speed. The model incorporates polarization characterization and view angle dependence of the foam-cover emissivity. For incidence angle and wind speed less than 15 m/s, the emissivity values calculated from this model differs by <8 percent from those calculated from Wilheit\´s model. At nadir and at 25 m/s wind speed, the emissivity calculated from the two models differ by percent.