High-Frequency Acoustic Backscatter from the Sea Surface
NAVAL UNDERWATER SYSTEMS CENTER NEW LONDON CT
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This document contains the slide presentation entitled High- Frequency Acoustic Backscatter From the Sea Surface, given at the 107th meeting of the Acoustic Society of America on 8 May 1984 in Norfolk, Virginia. A high resolution scattering experiment was conducted in the shallow waters of the North Atlantic. A narrow beam parametric array, which was rotatable in both azimuth and elevation, was utilized as a broadband high-frequency acoustic projector. Acoustic surface scattering data were obtained at normal incidence and low grazing angles less than 10 deg as a function of acoustic transmit frequency and sea state conditions. Meteorologic and oceanographic data were obtained in concert with the acoustic measurements and included wind speed and direction, ocean surface wave spectra and currents, and ocean sound speed. Surface backscattering strength, Doppler spectra shift and spread, and envelope statistics were some of the measured parameters. It will be shown that the Doppler spectra are approximately Gaussian and the spectral shift could be predicted from Bragg diffraction theory modified by the induced Doppler due to surface currents. The measured Doppler spreads, however, were greater than those predicted by composite roughness theory.
- Physical and Dynamic Oceanography