Numerical Simulation and Analysis of Microwave Backscattering Characteristics from Sea Surface with Breaking Waves and Foam

In the field of ocean remote sensing and detection, the normalized scattering cross-section (NRCS), an important statistical feature of sea surface, is usually employed to assess the severity of sea state. In high sea states, the sea surface wave becomes breaking and generating foam and spray which will affect the scattering characteristic of the sea surface. This study presents a modified NRCS model for sea surface, taking into account the impacts of wave breaking and foam. Firstly, the NRCS of the non-wave breaking sea surface area is calculated utilizing the two-scale method (TSM). Then, the NRCS of the sea surface encompassing the breaking wave and foam regions is determined by integrating the breaking wave NRCS semi-empirical model and vector radiative transfer (VRT) theory. Finally, the total NRCS of the sea surface containing breaking waves and foam is derived employing the white cap coverage rate. This model modifies the NRCS of a wind-driven rough sea surface composite model with breaking waves and a foam layer at a moderate incident angle. Based on the modified model, the NRCS of the sea surface for both horizontal polarization (HH-Pol) and vertical polarization (VV -Pol) are calculated at moderate incidence angles. The validity of the modified model is verified by comparing the Geophysical model function (GMF) results. The simulation results show that the effects of spray and foam on the NRCS of the sea surface cannot be ignored, especially for the results of HH-Pol. The proposed model provides a reference for the analysis of microwave backscattering characteristics of the sea surface in high sea states.