Long-Range Propagation through Internal Waves

Abstract

Abstract : LONG-TERM GOALS: This project aims to understand the fluctuations in low frequency (100 Hz, for example) acoustical propagation in the ocean over long distances (50 km to thousands of km), as well as other effects of internal waves and other small-scale variability in the speed of sound. OBJECTIVES: The objective is to model results of recent low-frequency, deep-water acoustic-propagation experiments, constraining the model environment from the measurements of those environments. Phenomena such as intensity fluctuations and deep arrivals are of more concern than travel time fluctuations, as the physics of travel time fluctuations is much better understood. APPROACH: Simulation of acoustic propagation in a model ocean with internal waves is used to study the effects of internal waves on the propagation. A highly accurate mode code has been developed for these studies. WORK COMPLETED: The mode code has been developed and verified. Studies of the propagation starting with a single mode whose turning depth is within the main thermocline have begun. A comparison with transport theory has been made, and a new phenomenon in the propagation has been discovered.