Broadband PE propagation through mesoscale perturbations

Abstract

When acoustic ray paths are computed in a range-dependent environment with mesoscale perturbations, the behavior of the smaller angle, axial rays has been shown to be chaotic−imposing a limitation on ray predictability to within the first few thousand km [Smith etal., J. Acoust. Soc. Am. 91, 1939–1959 (1992)]. This may be indicative of nonadiabatic behavior. A manifestation of this may be observable in the SLICE-89 data set [Cornuelle etal., SIO Reference Series 92-17 (1992)], which displays a broad, late arrival in depth of acoustic energy, as opposed to a narrow region of late arrivals at the sound channel axis as predicted by range-independent models. A broadband version of the parabolic wave equation is implemented for both a range-independent and range-dependent (consisting of a superposition of baroclinic Rossby waves) deep ocean environment. The results are compared qualitatively with experimental data. Acoustic mode coupling due to mesoscale ocean structure is addressed and the effects on long-range acoustic tomography is discussed.