ASA 126th Meeting Denver 1993 October 4-8

5pUW7. High-frequency propagation in a turbulent shallow water environment.

Daniela DiIorio David M. Farmer

Inst. of Ocean Sci., P.O. Box 6000, Sidney, BC V8L 4B2, Canada

A high-frequency (67-kHz) acoustic propagation experiment conducted in a shallow tidal channel provides an opportunity for comparison of observed acoustical scintillations with available theory. The tidal current ensures that the acoustic path runs through a turbulent boundary layer at all times. Analysis of log-amplitude, phase, and phase-difference signals shows close agreement with the weak scattering theory of Tatarski using the Kolmogorov turbulence model together with the Taylor hypothesis of ``frozen'' advected turbulence. By combining acoustic data with direct measurement of temperature and salinity fluctuations using in situ sensors, the contribution of turbulent velocity fluctuations to the scintillation signal is evaluated. The results show that turbulent velocity fluctuations rather than temperature and salinity variability are the dominant source of observed acoustic fluctuations, leading to estimates of turbulent energy dissipation in the range (epsilon)(approximately equal to)10[sup -5] m[sup 2] s[sup -3].