ASA 124th Meeting New Orleans 1992 October

3aUW2. Downslope conversion in oceanic sound propagation: CENTRO/ANTS code interpretation.

J. R. Yuan

H. Uberall

Phys. Dept., Catholic Univ. of America, Washington, DC 20064

W. S. Hodgkiss

Scripps Inst. of Oceanogr., San Diego, CA 92152

The 1989 experiment by the Scripps Marine Physical Laboratory, studying sound propagation down the continental slope off Pt. Arguello and Pt. Conception, CA, has furnished evidence for the downslope conversion effect in which sound propagating down from a source over the continental shelf, by its interaction with the sloping ocean floor, gets trapped into the sound channel. As a consequence, the horizontal arrival structure observed at a distant receiver over deep water (the Scripps FLIP array, in this case) shows a flat ``pedestal'' shape centered at (plus or minus)20(degrees) about the horizontal, while with a source also over deep water, a central minimum would be apparent due to Snell's law. Our calculations, using the CENTRO/ANTS normal mode code written by J. I. Arvelo and developed further at Catholic University, bears out the pedestal shape of the arrival structure. In these calculations, downslope propagation is treated adiabatically, and the bottom structure (sediment with underlying rock) is correctly taken into account. [Work supported by the ONR.]