Simulation of scattering on a time-varying sea surface beneath which an internal solitary wave travels

摘要

Many internal waves (IWs) have been observed in synthetic aperture radar images. However, few studies have simulated the scattering characteristic of such waves. The present study focuses on the modulation of the scattering coefficient and of the Doppler spectrum in the presence of time-varying internal solitary wave (ISW). The IW gradient facilitates the hydrodynamic modulation of rough capillary waves. In addition, this study adopts the wave-current interaction to modify the capillary wave spectrum. Then, the facet model is applied to calculate the scattering characteristics of a large-scope two-dimensional sea surface, beneath which an ISW travels. This model simplifies the sea surface into a two-scale profile. Long waves are locally approximated by a tilted facet that is considerably longer than the electromagnetic wavelength. Capillary waves are considered to be a set of sinusoidal ripple patches that superimpose on these long waves. The wavenumber of the sinusoidal waves must satisfy the resonant condition of Bragg waves that dominate the scattered wave component.