Electromagnetic Scattering from Deterministic Sea Surface With Oceanic Internal Waves via the Variable-Coefficient Gardener Model

Abstract

In this paper, a hydrodynamic-electromagnetic model is proposed for analyzing the electromagnetic scattering characteristic of a multiscale deterministic sea surface with internal waves in a two-layer ocean system. A variable-coefficient Gardner model is applied to establish the profile of the internal waves, and the spectrum induced by a variable current is then derived by the action balance equation. The slope-deterministic facet-based two-scale method (SDFb-TSM) is used to calculate the scattering characteristics of the multiscale deterministic sea surface. The total coefficient distribution is then quantitatively obtained from this composite model considering Bragg resonance, tilting effect, and specular reflection effect. Numerical results show that the shape and modulated depth of normalized radar cross section induced by the internal soliton of the Gardner model agree quite well with the measured data. Thus, the Gardner model combined with the SDFb-TSM method performes better than the KdV model combined with statistical scattering methods for the prediction of scattering characteristics of a sea surface with internal waves. The variation in scattering signature characteristics for the depression internal wave are discussed for both one- and two-soliton cases. The influences on the scattering coefficients under different parameters of the internal wave, sea state, and radar system are analyzed. Furthermore, both overtaking-type and head-on-type internal waves are presented and the effect of the perturbed term on internal wave profiles and the scattering characteristics of both one- and two-soliton cases are discussed.