ANALYSIS OF OCEAN SURFACE ACOUSTICAL DATA FROM APL/UW-IOS EXPERIMENTS IN JANUARY, 1992

Authors
  1. Trevorrow, M.V.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN);Institute of Ocean Sciences, Sidney BC (CAN)
Abstract
The purpose of this work was to investigate the effects of surface waves and bubbles on high frequency forward scattered sound. The experiments were conducted January 10 - 27, 1992 in the open Pacific approximates to 400 miles offshore of San Diego, California (near N32 degrees, W123 degrees). During the experiment the IOS group performaed 11 deployments of the SeaScan acousics drifter, yielding 88 hours of acoustic data. The APL-UW group performed 20 - 50 kHz bistatic and monostatic ssurface acoustic scattering tests from the R.P. Flip from January 15 until February 3. The SeaScan instrument collected both upward-looking sonar and horizontal-looking sidescan sonar acoustic back-scattering data. The winds were sufficiently strong to produce breaking waves and natural micro-bubble clouds for only 5 of the 11 deployments. These occurred when the wind speed exceeded approximates to 12 knots. These microbubble plumes were observed to extend as much as 9 m below the surface, and have peak spectral densities in the top meter of 1.0 x 10 super 5 bubbles/m cube (re 1 mu m) at radii near 16 mu m. Acoustic extinction due to these ambient microbubbles was observed to be highly variable in space and time, with integrated losses (at 20 - 50 kHz and grazing angles of 10 degrees) in the range 1 to 22 dB.
Keywords
Ambient microbubbles;Surface scattering;Bubble clouds;Surface wave spectra;Flip 92;APL Open ocean experiment 92;SeaScan;Bubble densities;Upward looking sonar
Report Number
DREA-CR-93-446 — Contractor Report
Date of publication
01 Aug 1993
Number of Pages
67
DSTKIM No
94-00382
CANDIS No
136332
Format(s):
Hardcopy;Originator's fiche received by DSIS

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