Signatures of microwave scattering and emission from foam-vovered ocean surface

This study presents signatures of microwave scattering and emission from foam-covered ocean surfaces, calling for vertically stratified foam layers with rough top and bottom boundaries. A model is proposed that incorporates both foam-layer properties (temperature, salinity, thickness, and void-fraction profile) and observation parameters (polarization, frequency, and look angle). The model describes both coherent and incoherent scattering and accounts for coupling between the foam layer and the rough sea surface, enabling a quantitative description of the foam layer’s geometric and physical properties in terms of emission signatures. The model predicts emission across a wide range of frequencies (1–37 GHz) and foam thicknesses (0–2 cm), revealing significant emission features that enhance our understanding of the underpinning physical phenomena. Specific signatures, including the sensitivity of brightness temperature to the vertical void fraction profile and the influence of surface roughness on emission saturation, are detailed and discussed. To verify the accuracy of the model’s predictions, three independent experimental datasets are used, resulting in a remarkable accuracy: root-mean-square error (RMSE) <2% and r > 0.99, which also demonstrates its robustness across varying conditions. This physically-based model offers an alternative to empirical regressions for foam thickness retrieval, enhancing geophysical retrieval estimations for L-band missions like satellite observations