High-Frequency Acoustic Backscatter from the Sea Surface

• Main Authors: Roderick, William I, Chester, John B, Dullea, Robert K
• Other Authors: NAVAL UNDERWATER SYSTEMS CENTER NEW LONDON CT
• Format: Text
• Language: English
• Published: 1984
• Subjects: Physical and Dynamic Oceanography; Acoustics; *ACOUSTIC MEASUREMENT; *ACOUSTIC SCATTERING; *BACKSCATTERING; *OCEAN SURFACE; *SEA STATES; ACOUSTIC DATA; ARRAYS; CURRENTS; DOPPLER SYSTEMS; GRAZING; HIGH FREQUENCY; HIGH RESOLUTION; LOW ANGLES; ROUGHNESS; SCATTERING; SHALLOW WATER; SHIFTING; STATISTICS; SURFACE ROUGHNESS; SURFACES; THEORY; WIND VELOCITY; PHYSICAL OPTICS; DIFFRACTION THEORY; LPN-NUSC-A67001; PE62759N; North Atlantic
• Online Access: http://www.dtic.mil/docs/citations/ADA143536; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA143536

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. Presented at the Meeting of the Acoustical Society of America (107th), 8 May 1984, Norfolk, VA.