ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

3aUW7. Temporal coherence and stability of bottom interacting sound pulses.

Xin Tang

Fred D. Tappert

Appl. Marine Phys., RSMAS, Univ. of Miami, 4600 Rickenbacker Cswy., Miami, FL 33149

Sound propagation at moderate frequencies (depth to wavelength ratio between 20 and 100) in shallow-water environments is extremely complicated, variable, and poorly understood due to multiple processes that cover a wide range of temporal and spatial scales. Broadband full-wave numerical simulations are performed with the UMPE model at a large number of geophysical times to display the temporal variability, stability, and coherence of acoustic pulse arrivals in a multipath environment that includes multiple rough bottom forward scattering and multiple forward volume scattering by internal waves that are described by either a Garrett--Munk type of spectral model or a soliton type of model. It is found that the effects of rough bottom scattering change the phase structure while the effects of internal waves account for the observed temporal fluctuations, leading to coherence times of minutes for individual multipaths at 20-km ranges, and a stable envelope having a coherence time of hours. [Work supported by ONR.]