Horizontal focusing/defocusing due to shallow-water internal waves.

Abstract

During the New Jersey Shallow Water 2006 (SW06) experiment, an acoustic source was towed by the Research Vessel Sharp and followed the front of an internal wave packet. The source was transmitting broadband acoustic signals (50–450 Hz) in different angles with respect to the internal wave front. The receptions of transmitted signal on a vertical hydrophone line array are analyzed to study the horizontal focusing/defocusing that occurred when the internal wave front and acoustic track aligned closely. Based on ship-board radar images and temperature data collected on the environmental moorings at various locations along the acoustic track, a detailed three-dimensional (3D) environment is reconstructed for a 3-D parabolic approximation model to study the unique propagation scenario. Construction of index of normal mode refraction for these data provides a clear picture of acoustic energy focusing for this event. Data and model comparison are in good agreement. [Work supported by ONR321 OA]