Full-wave simulation of the forward scattering of sound in a structured ocean: a comparison with observations

• Published in: The Journal of the Acoustical Society of America 1999-01, Vol.103 (3), p.1293-1306
• Main Authors: Wolfson, Michael A, Spiesberger, John L
• Format: Article
• Language: English
• ISSN: 0001-4966

Between 1983 and 1989, acoustic pulse-like signals at 133-Hz, 60-ms resolution, were transmitted from Oahu to Northern California. Analysis of the data indicates that the early arriving, steep paths are stable over basin scales, whereas the late, near-axial paths are sensitive to ocean structure. The late paths undergo vertical scattering on the order of the acoustic waveguide, i.e., 1 km [J. Acoust. Soc. Am. 99, 173-184 (1996)]. The parabolic approximation is used to simulate pulse propagation over the vertical plane connecting the source and receiver. Several prescriptions are used for the speed of sound: (1) Climatologically averaged sound speed with and without a realization of internal waves superposed; (2) Measured mesoscale structure with and without a realization of internal waves superposed. The spectrum of the internal waves is given by Garrett and Munk. Modeled internal waves and the measured mesoscale structure are sufficient to explain the vertical scattering of sound by 1 km. The mesoscale structure contributes a travel time bias of 0.6 s for the late multipath. This bias is seen to be a relevant contribution in accounting for the travel times of the last arrival.