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Abstract:
Volume scattering strengths at selected frequencies from 3.85 to 15.50 kHz, determined from Ocean Acre measurements in June 1972, are described in terms of diurnal variations, daily variability, frequency characteristics, and seasonal trends. Day-night comparisons of profiles at 13.50 and 15.50 kHz showed a maximum increase in scattering strength of 35 dB in the depth range from 120 to 330 m and of 15 dB above 120 m. Integrated scattering strengths varied with depth by as much as 15 dB, whereas total-column strengths at night were only 3 to 4 dB above daytime levels. Because of this small difference, the latter result is considered inadequate in describing the large diurnal variations associated with the vertical migration of scatterers. Unlike earlier results, night-to-night variability of scattering strength during the stable period was as large as 10 dB for all of the frequencies over most of the water columns. At all of the frequencies, nighttime scattering strengths peaked within 120 m of the surface. At 13.50 and 15.50 kHz, additional contributions occurred in the depth interval from 250 to 550 m. The spectra of total-column strengths exhibited a broad resonance centered about 9.00 kHz which was unlike the low- and high-frequency resonances found in earlier studies. Scattering strength at 3.85 kHz experienced an increase from spring to summer, although the amounts were not the same in two different years.
| Description: |
Technical rept. |
| Pages: |
35 |
| Report Date: |
03 JAN 1977 |
| Report Number: |
A668530 |
Report Unavailable |
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