Towards a Deterministic High-Frequency Shallow Water Ray Propagation Model

High frequency acoustic scattering from the ocean bottom and the ocean surface has been the subject of continuing interest for many years. Data and models have shown that as the signal frequency increases, the scattering pattern from such rough surfaces evolves from specular to quasi omni-directional. Multipath structures observed in shallow waters exhibit angular spreads that cannot be explained by assuming purely specular reflection. Most ray propagation models treat surface bounces as being essentially specular which poorly accounts for the multipath structures and in turn introduce errors in the estimation of the propagated and reverberated fields. For several applications such as high frequency Synthetic Aperture Sonar (SAS), minehunting and communi- cations there is a need for reliable and fast propagation models able to correctly treat scattering at the rough waveguide boundaries. The Bellhop ray tracing model has been modified to introduce deterministic properties of the sea surface and sea bottom. Scattering from these surfaces is treated using solutions from the integral equation. Simulations display a significant effect of the angular spreading of the multipath structure increasing with roughness that is closer to the one observed on in-situ data.