Modeling of acoustic propagation across warm-core eddies

Abstract

A theoretical investigation has been made into the effect on acoustic propagation of oceanic fronts at the edge of warm-core eddies. The investigation utilized modeling of acoustic propagation using the parabolic approximation to the wave equation. Propagation was examined using typical parameters for a wintertime warm-core eddy in the Tasman Sea. Propagation across the eddy boundary (at a frequency of 100 Hz) is shown to create a second series of convergence zones, in addition to the normal series. This occurred for propagation both into and out of the eddy. For a source outside the eddy, energy is shown to strongly couple from deep refracted paths to mixed layer paths within the eddy. The eddy boundary was found to have significant effects on convergence zone properties. Acoustic propagation was also modeled using parameters from a particular realization of a summertime warm-core eddy in the Tasman Sea (for which realization there was environmental and acoustic data available). This eddy had a surface duct and a separate subsurface duct. Reasonable agreement between model and experiment was found for source and receiver both in the subsurface duct at frequencies from 50 to 1000 Hz; disagreement occurred at 25 Hz. However, for source in surface duct but receiver in subsurface duct, the agreement was poor at most frequencies. The effect of minor variations in oceanic and experimental parameters was examined to determine the experimental resolution required of these parameters.

Effect of Subsurface Mediterranean Water Eddies on Sound Propagation Using ROMS Output and the Bellhop Model

“…They discovered how a warm eddy affects sound propagation: the low-frequency sound propagation from the eddy center to the eddy edge is more affected by the eddy in comparison with the sound propagation from the eddy edge to the eddy center. In another study, Li Jia et al (2012) [14] found that an eddy with a warm core can make the acoustic convergence zone recede and increase its width, while a cold eddy has an opposite effect. Using the parabolic equation (PE), Lawrence (1983) [14] calculated the transmission loss as a function of depth and distance for an acoustic signal crossing the Tasman warm eddy.…”

Oceanographic, topographic, and sediment interactions in deep water acoustic propagation. Part I. Sediment effects on water column propagation patterns

“…Most recently, the focus has been on studying the effects of oceanographic variations on underwater acoustic propagation. Lawrence (1983) studied the acoustic effects of warm-core eddies in the Tasman Sea, noting surface ducted sound in the eddy converting to convergence zone propagation outside the eddy, and a change of convergence zone location. Lee et al (1989) demonstrated convergence zone shifts of 5-10 km in acoustic propagation across Gulf Stream eddies, and Mellberg et al (1990) showed that the changing ocean structure within a few days can cause convergence zone shifts of up to 10-km range and magnitude changes of up to 5 dB in a Gulf Stream meander.…”

Effects of Warm Eddy on Long-range Sound Propagation in the East Sea

“…[3] 해외의 경우 소용돌이의 발달 및 해양학적 특 성과 소용돌이가 음파전달에 미치는 영향에 대해 활 발하게 진행되어 왔다. [4][5][6] 국내의 경우 동해에 많이 발달하는 난수성 소용돌이에 대한 해양학적 연구는 많이 진행되어 온 반면에 [7,8]…”