A BROADBAND MODEL FOR PREDICTING BISTATIC SURFACE SCATTERING STRENGTHS

摘要

A 3-D model is presented which provides a physics-based estimate of the dependence of surface scattering strength on the incident and scattered angles, the acoustic frequency (50-5000 Hz), and physical descriptors of the environment. The model describes scattering from both the rough air-sea interface (small-slope theory) and subsurface bubbles due to breaking waves (a semi-empirical Lloyd-mirror model). Model comparisons with open-ocean data demonstrate that interface backscattering can be dominant at moderate-to-high grazing angles, while bubble-cloud backscattering becomes increasingly important with decreasing grazing angle and increasing wind speed, and that, below ～1 kHz, bubble-cloud backscattering has a strong frequency dependence.