Electromagnetic scattering from wind blown waves and ripples modulated by longer waves under laboratory conditions

Laboratory radar measurements at low grazing angle of long waves of different steepness in the presence of wind waves were examined. The radar cross-section (RCS) variation was found to agree closely with the composite model. The effect of the orbital velocity of the long waves was observable in the Doppler spectra and could be used to determine the wave height; however, other aspects of the Doppler spectra could not be satisfactorily explained by the composite model. Electromagnetic (EM) scattering results were also generated using the Forward-backward code in conjunction with a two-dimensional hydrodynamic code that produced time-dependent wave profiles of long waves with wind blown ripples. The numerical results showed close agreement with the normalised RCS calculated from Bragg scattering theory, ??⁰==B|², but not with the composite model.