Modeled position and intensity statistics in deep water caustics

Abstract

Caustics are a form of natural focusing that occurs in deep water acoustic propagation, but acoustic intensity and position perturbations at caustics have not been investigated in detail. The positions, shapes, and intensities of caustics and cusps are controlled primarily by the large-scale sound speed profile, with perturbations primarily caused by deterministic features (fronts, eddies) and stochastic features (internal waves). We selected two representative deep water environments for our analysis: a north Pacific site and temperate profile. For each region, 100 independent and 100 time-coherent realizations of internal waves were generated. The model uses the statistics provided by the Garrett-Munk power spectrum to generate displacements, which are converted into sound speed realizations. In the north Pacific profile, internal waves were concentrated primarily in the upper 200 m of water. In the temperate profile, internal waves were concentrated in the upper 700 m of water. We used a Gaussian beam model to analyze position and intensity statistics of caustics for both types (independent and time-coherent) of internal wave fields at each site as a function of frequency, internal wave strength, and source depth. Simulations indicate that caustics are more stable than other portions of the acoustic field and that this stability is a function of internal wave strength and caustic location. This work is approved for public release, Distribution Unlimited.Caustics are a form of natural focusing that occurs in deep water acoustic propagation, but acoustic intensity and position perturbations at caustics have not been investigated in detail. The positions, shapes, and intensities of caustics and cusps are controlled primarily by the large-scale sound speed profile, with perturbations primarily caused by deterministic features (fronts, eddies) and stochastic features (internal waves). We selected two representative deep water environments for our analysis: a north Pacific site and temperate profile. For each region, 100 independent and 100 time-coherent realizations of internal waves were generated. The model uses the statistics provided by the Garrett-Munk power spectrum to generate displacements, which are converted into sound speed realizations. In the north Pacific profile, internal waves were concentrated primarily in the upper 200 m of water. In the temperate profile, internal waves were concentrated in the upper 700 m of water. We used a Gaussian beam ...