Sea surface salinity can be measured by microwaveradiometry at L-band (1400–1427 MHz). This frequency is acompromise between sensitivity to the salinity, small atmosphericperturbation, and reasonable pixel resolution. The descriptionof the ocean emission depends on two main factors: 1) the seawater permittivity, which is a function of salinity, temperature,and frequency, and 2) the sea surface state, which depends on thewind-induced wave spectrum, swell, and rain-induced roughnessspectrum, and by the foam coverage and its emissivity. This studypresents a simplified two-layer emission model for foam-coveredwater and the results of a controlled experiment to measure thefoam emissivity as a function of salinity, foam thickness, incidenceangle, and polarization. Experimental results are presented, andthen compared to the two-layer foam emission model with themeasured foam parameters used as input model parameters. At37 psu salt water the foam-induced emissivity increase is 0.007per millimeter of foam thickness (extrapolated to nadir), increasingwith increasing incidence angles at vertical polarization,and decreasing with