Three dimensional parabolic equation modeling of an internal wave event during Shallow Water 2006.

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 two and three dimensional) interference patterns. Of specific interest are fluctuations of measured intensity preceding the internal wave’s arrival. Additionally, depth variability of the measured acoustic intensities can be attributed to a warm water intrusion coinciding with the internal wave event. This presentation shows recent modeling results using the experimental geometry, acoustic signal parameters, and a simulated oceanographic environment based on environmental moorings and ship‐born sensors. A new version of the three‐dimensional Monterey–Miami parabolic equation code, which incorporates a user‐defined sound speed field, is used. [Work sponsored by the Office of Naval Research.]