Review Article. Directional ocean wave spectra as observed with multifrequency continuous wave radar

A multifrequency continuous wave radar has been developed. By means of this, the directional spectra of ocean irregularities (waves and turbulence) can be measured by illuminating the sea surface simultaneously over a frequency band of some 30 MHz in the 6 GHz region, using 15 frequency spacings. By measuring amplitude and phase, the power spectrum (Doppler spectrum) associated with each of the 15 discrete sea surface irregularity scales is obtained, as is, independently, information about velocity. From the Doppler spectra associated with each of the 15 irregularity scales investigated (6-150 m) it is possible to distinguish between the contribution from the coherent gravity waves and the incoherent random irregularities. Experimental results from a set of different geophysical situations are given with reference to a general theoretical presentation.