Abstract:

The continental shelf off the New Jersey coast is a site of intense internal-wave activity. The space--time variability of an acoustic field in this shallow-water region was studied using oceanographic measurements along a 42-km track from the SWARM95 [shallow-water acoustics in a random medium] experiment. A sound--speed model based on the KdV equation was developed to include the nonlinear contribution of the internal wave field, with parameters estimated from towed yo-yo ctd data, ship radar images of internal-wavesurface expression and acoustic backscatter images of subsurface internal-wave structure. The linear internal-wave contribution was modeled by an ADCP-derived displacement power spectrum. Bathymetry and sub-bottom parameters were previously estimated from wave-field inversions using chirp sonar surveys. Simulation results are presented for acoustic propagation at frequencies of 224 and 400 Hz using a wide-angle parabolic equation method to compute realizations of the acoustic field. Results include estimates of the intensity fluctuations and coherence for two vertical arrays located at 33 and 42 km from the moored sources. [Work supported by ONR.]