Measurements of the Doppler spectra of breaking waves

A number of experiments have been carried out in two large wave tanks with three different radar systems. The radar frequency, grazing angle, azimuth angle, water wavelength, wave steepness and the breaking wave strength were all varied systematically. The velocity of the peak Doppler power spectral density was found to depend on the phase velocity of the breaking wave in the radar line of sight, but was independent of the radar frequency. The spectral width depended on the phase velocity of the wave, but not on the grazing angle used. The peak Doppler power and radar cross-section of the breaking waves was found to scale with the radar wavelength (proplambda_r ^1.5)