ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

1aAO12. Internal wave effects on long-range ocean acoustic tomography.

M. A. Wolfson

J. L. Spiesberger

Dept. Meteorol. and ARL, Penn State Univ., 602 Walker Building, University Park, PA 16802

F. D. Tappert

Univ. of Miami, Miami, FL 33149

Full-wave numerical simulations of internal wave scattering of low-frequency sound in the deep ocean are performed with an efficient broadband PE model based on a new parabolic approximation that is second-order accurate, and an internal wave model based on a new representation of the GM spectrum that allows efficient generation of internal wave fields that evolve in geophysical time. Results are displayed as plots of acoustic travel time versus geotime for various source--receiver separations (up to 8 Mm), and various center frequencies and bandwidths. Quantitative examination (coherent and incoherent geotime averages) yields information about the temporal coherence and stability of each multipath. It is found that the later near-axial arrivals are unstable and unresolvable, and therefore not useful for tomography, at ranges and frequencies that are consistent with the predictions of Dozier and Tappert [ 533--547 (1978)] who used a coupled mode model. [Work supported by ONR and ARPA.]