Three-Dimensional Parabolic-Equation-Based Estimation of the Ocean Acoustic Field

摘要

This report describes a three-dimensional parabolic-equation-based model for deterministic acoustic propagatin in a deep-ocean environment. It constitutes one of the outputs of a research program in spatial properties of the low-frequency acoustic field initiated in 1974 to describe the effects of intgernal ocean inhomogeneities on the performance of large undersea acoustic antennas. In that program these inhomogeneities were divided into large-scale internal-wave-type features thought to be more evenly distributed throughout the ocean. This model deals with the former case and enables the complete calculation of the three-dimensional acoustic field, that is, the azimuthal as well as the vertical distribution of energy. It can handle both a three-dimensionally varying sound-speed field and a triangularly faceted bathymetry. To facilitate calculations with moderate horizontal gradients and little or no crossangle scattering generated by the bottom, a modified version that in effect enables the propagation of a coherent phase-tracked fan is also described and developed.