A Study of Acoustic Fluctuations from Basin-Scale Pulse Transmissions
WOODS HOLE OCEANOGRAPHIC INSTITUTION MA DEPT OF APPLIED OCEAN PHYSICS AND ENGINEERING
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LONG-TERM GOAL. The long-term goal of this research is to develop our understanding of long-range oceanic pulse propagation through random sound speed fields, like those caused by internal waves, so that we can use acoustic fluctuations like temporal, vertical, and horizontal coherence to infer average internal-wave spectral parameters. SCIENTIFIC OBJECTIVES. The scientific objective of this work is to develop analytical expressions for temporal, vertical, and horizontal coherence of the acoustic field as a function of internal-wave model parameters and compare these analytic model predictions to data and numerical models. Analytical results for these second moments are important because they eliminate the need for time-consuming Monte-Carlo runs and they allow an efficient treatment of the inverse problem1. A key element of this work is to understand the limits of geometrical optics GO at frequencies of order 75-Hz, and to evaluate the relative contributions of medium decoherence and intermittent structure2 on the acoustic coherence functions. It has been shown that acoustic fluctuations from energy which has ensonified the upper few hundred meters of the ocean cannot be explained using the Garrett-Munk GM internal wave model1, so a secondary, oceanographic objective of this work is to explore upper ocean internal-wave models.
- Physical and Dynamic Oceanography