An Improved Two-scale Model for EM Scattering from Electrically Large Rough Surface with Breaking Waves

Abstract

Breaking waves have been suggested to be a great contributor to the electromagnetic (EM) scattering from rough sea surface in large incident angles under high sea states, which is much different from the backscattering of rough sea surface with no breaking waves. Good understanding of microwave scattering properties from rough sea surface is of great value. An improved two-scale model for the backscattering from rough sea surface with breaking waves is proposed in this paper. In this proposed method, the sea surface with breaking waves is divided into two components: the large-scale and small-scale components. For the large scale components, the geometric structure of the surface is dominated by the large breaking waves. The large scale surface is divided into facets. Kirchhoff approximation (KA) method is applied to compute the backscattering for each facet. While for the small scale components, short capillary-type sea waves and the small-scale roughness is distributed over the slope distribution of the large-scale roughness. Integral electromagnetic method (IEM) is applied to calculate the electromagnetic backscattering form the small roughness. The total scattering of the sea surface with breaking wave is given by the electromagnetic scattering from the large-scale roughness added by the scattering from the small-scale roughness. The backscattering from rough sea surface with breaking waves is calculated by this improved two-scale model in large incident angles. The results show that the proposed method has the merits of high calculation efficiency as well as calculation accuracy at moderate incident angles.