ASA 126th Meeting Denver 1993 October 4-8

3aAO9. Effects of perturbations on long-range propagation.

William A. Kuperman Michael D. Collins B. Edward McDonald

Naval Res. Lab., Washington, DC 20375

Kevin D. Heaney

Planning Systems, Inc., McLean, VA 22102

Results of numerical modeling of long-range (greater than 500-km) low-frequency acoustic propagation in the ocean have been presented previously. These results were in qualitative agreement with measurements for the Heard Island Feasibility Test and the SLICE89 experiments. To quantify the differences between experimental and parabolic equation (PE) results, time-dependent modal decomposition was applied to the received signals. This modal tomography gives us an indication of the depth-dependent differences between the actual and assumed sound-speed profiles. This work is extended to look at the effects of small perturbations in the sound-speed field (i.e., internal waves) on the arrival pattern. Internal waves were modeled using a statistical realization of the Garrett--Munk spectrum. Results of the effects of internal waves on specific deep ocean mode functions and model group velocities are presented. [sup a)]Present address: Marine Physical Labs., Scripps Inst. of Oceanogr., UCSD, La Jolla, CA 92093.