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

Between 1983 and 1989, acoustic pulse-like signals at 133-Hz, 60-ms resolut ion, were transmitted from Oahu to Northern California. Analysis of the dat a indicates that the early arriving, steep paths are stable over basin scal es, whereas the late, near-axial paths are sensitive to ocean structure. Th e late paths undergo vertical scattering on the order of the acoustic waveg uide, i.e., 1 km [J. Acoust. Sec. Am. 99, 173-184 (1996)]. The parabolic ap proximation is used to simulate pulse propagation over the vertical plane c onnecting the source and receiver. Several prescriptions art used for the s peed 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 vertica l 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 relev ant contribution in accounting for the travel times of the last arrival. (C ) 1999 Acoustical Society of America. [S0001-4966(99)03108-2].