Intensity fluctuations dominated by horizontal refraction during a strong nonlinear internal wave event.

Abstract

During the Shallow Water 2006 (SW06) experiment, a J‐15 acoustic source deployed from the Research Vessel Sharp transmitted broadband (100–500 Hz) chirp signals 15 km away from a vertical line array. The array was intentionally positioned near the shelf‐break front and in an area where internal waves are known to occur. During the same time an internal wave, “Event 44,” passed through the sound field such that the internal wave front was near parallel to the acoustic transmission path. Measured data show substantial intensity fluctuations that vary over time and space due to complex multimode and multipath (both 2‐ and 3‐D) interference patterns. This presentation compares 3‐D modeling results using the experimental geometry, acoustic signal parameters, and a simulated oceanographic environment based on environmental moorings and ship‐born sensors to mimic the measured internal wave event. A modified version of the 3‐D Monterey‐Miami parabolic equation (MMPE) code which incorporates a user‐defined sound s...