Abstract:
Depth diffusion of acoustic energy in the finale of acoustic pulses has been observed for transmissions of 1 Mm (Slice89, Mid-Pacific), 3.5 Mm (ATOC, California to Hawaii), and 5.1 Mm (ATOC, California to Christmas Island). This depth diffusion is a measure of the strength of internal waves in the main thermocline. A measure of the strength of internal waves is defined as the variance of displacement at a reference buoyancy frequency of 3 cph. The standard Garrett--Munk spectrum has a strength of 50 m[sup 2]. In the case of Slice89, an internal-wave strength of 25 (+/-) 10 m[sup 2], was observed (July 1989). Internal-wave strength will be presented for the two ATOC location paths, for dates beginning in November 1995. Information from identifiable time fronts in the early-arriving part of the pulse will also be presented. [Work supported by ONR and by the Strategic Environmental Research and Development Program through ARPA.]