Dynamics and Stability of Acoustic Wavefronts in the Ocean

Abstract

LONG-TERM GOALS• To develop a method of modeling sound propagation in an environment with multi-scale inhomogeneities, which preserves the efficiency and intuitive qualities of the ray theory but is free from spurious environmental sensitivity and strong perturbations associated with ray trajectories.• To investigate and quantify effects on underwater acoustic wavefronts of internal gravity waves, sea swell, "spice," and other small-scale processes in the water column. OBJECTIVES1. To assess significance of time dependence of the sound speed and flow velocity perturbations on predictability of acoustic wavefronts and timefronts.2. To quantify horizontal refraction of sound by random meso-scale inhomogeneities at O(1)Mm propagation ranges.3. To find the variance and bias of random ray travel times in the regime, where the ray displacement may be comparable to the vertical extent of the underwater waveguide but the clustering has not developed yet.4. To determine, using a perturbation theory and numerical simulations, typical propagation ranges where clustering of chaotic rays replaces the anisotropy of ray scattering as the main physical mechanism responsible for acoustic wavefront stability.5. To develop an efficient technique for modeling acoustic wavefronts and their perturbations in range-dependent and horizontally inhomogeneous oceans.6. To model perturbations of acoustic wavefronts and timefronts by internal gravity waves, internal tides, sea swell, and "spice" in the ocean.7. To investigate implications of wavefront stability on the downward extension of acoustic timefronts and deepening of lower turning points of steep rays due to small-and meso-scale physical processes in the upper ocean.