Investigation of the variability of Doppler spectra with radar frequency and grazing angle

The effect of varying grazing angle on the Doppler spectra of radar backscatter from wind waves has been investigated in a laboratory wave tank. Five different radar frequencies were used and six different wind conditions, for a range of grazing angles between 3° and 24°. The results show linear relationships between the velocity of the dominant scattering components and the grazing angle. This effect is hard to reconcile with a scattering mechanism based on Bragg resonance. Data from a cliff-top radar were also examined.