The paper deals with experimental determination of the wind-driven wave spectrum by using the remote method of high-resolution coherent radar sensing of the water surface. The method is applied to the conditions of the fetch-limited wind wave growth, which is typical for enclosed waters and the sea nearshore, where the dominant wavelength is of the order of ten meters. The experiments were performed using a coherent X-band panoramic digital radar operating with the horizontal polarization for transmission and reception. The paper considers an algorithm used to form velocity images of the water surface from the data of coherent radar sensing on the basis of the phase angle difference method. The paper shows the possibility to recover wind wave spectra from the data on the Doppler shift of microwave radio waves. A theoretical justification and an experimental verification of the method are provided. Appearance of the third harmonic of the wind waves recovered from the radar sensing data of the spatio-temporal spectra of Doppler velocities is demonstrated for the first time. The functions that relate to the wave elevation spectra and the Doppler velocity spectra are determined. It is shown that the linear free-surface wave approximation is valid for the reconstruction of wave spectra. The temporal and spatial omnidirectional wave spectra obtained in the experiment are described well by the power model functions using the exponent factor of −4" role="presentation">-4
Coherent radar, Doppler velocity, wind wave spectra
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