A new, semiempirical model for predicting bistatic surface backscattering strengths

Abstract

A Lloyd-mirror model of bubble-cloud scattering, along with perturbation theory for the rough air–sea interface, have been used as a basis for generating a new algorithm for predicting the strength of acoustic backscatter from the ocean surface. Multiparameter curve fits of the model to acoustic data from the Critical Sea Test program (1988–1996) and other at-sea experiments have been used to derive a new, semiempirical description of the dependence of surface backscattering strength on the incident and scattered grazing angles, the acoustic frequency, and environmental descriptors. The model represents an advance on previous algorithms (Chapman–Harris, Ogden–Nicholas–Erskine) in several ways: (1) a much improved, physics-based description of the grazing-angle dependence, applicable to arbitrarily low grazing angles; (2) a much improved description of low-to-moderate sea-state bubble scattering; (3) can handle vertically bistatic geometries; and (4) is applicable to a broader range of frequencies (50 to 5000 Hz). [Work supported by ONR.]