Foam effects on polarimetric passive microwave remote sensing of ocean wind vectors

In this paper, polarimetric microwave emissions from wind-generated foam-covered ocean surfaces are investigated. A dense media radiative transfer model (DMRT) is applied to the foam layer. The effects of boundary roughness are implemented by using the small perturbation method (SPM) describing the bistatic reflection coefficients between foam and ocean. An empirical wavenumber spectrum is used to generate the small-scale wind-generated sea surfaces. The iterative method is employed to solve DMRT equations. The method was applied to simulate results of all four Stokes parameters for 2-dimensional random rough surfaces. The theoretical results of four Stokes brightness temperatures with typical parameters of foam in passive remote sensing at 19 GHz and 37 GHz are illustrated. It is found that, at both frequencies, the first two Stokes parameters are increased with the presence of foam, and the third and fourth parameters, on the contrary, are reduced. The contribution of the foam layer to emission is larger at 37 GHz than at 19 GHz. The azimuth variations of polarimetric brightness temperature are calculated. Emission with various wind speed and foam layer thickness is also studied. Results are compared with the experimental measurements.