3-D Canyon TL Forecast for 29 Aug 0000Z and 1500Z, Issued 29 Aug 2009

Model Setting and Implementation

Y.-T. Lin, Woods Hole Oceanographic Institution

PE source location:  25 38.993 N 122 36.014 E (Canyon SHRU deployed location on QPE IOP Leg 1, water depth 200 m); PE source frequency: 300 Hz
x-y-z convention: PE marching direction (x), transverse direction (y) and depth (z); Step sizes: dx = 20 m, dy = 1.25 m, dz = 0.833 m 
Water column: Real-time MIT MSEAS system (4.5 km resolution); Bathymetry: UNH 100 m resolution data
Bottom: General sandy bottom (sound speed 1,700 m/s, density 1.5 g/cm3, attenuation coef. 0.5 dB/λ)

General Information about the Model

This forecast is for predicting the 3-D canyon acoustic effect on sound propagation and also the temporal variability of the sound field due to water-column condition changes. The model is an acoustic propagation program that employs the split-step Fourier (SSF) technique to solve the 3-D parabolic acoustic wave equation (PE) for one-way propagating waves in a Cartesian coordinate system. Bottom density contrast and volume absorption have been taken into account, and the PE starter is a 3-D variant of the Thomsons wide angle starter. Most importantly, the PE approximation is made with the 3-D version of the Thompson-Chapman wide angle expansion. The initial program development efforts are made by J. Colosi of NPS, USA, and the later modification for the Thompson-Chapman wide angle PE is done by T. Duda of WHOI. The 3-D wide angle starter and the treatment on bottom density are added by Y.-T. Lin of WHOI. This work is sponsored by the ONR.

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