North Pacific Acoustic Laboratory: Analysis of Shadow Zone Arrivals and Acoustic Propagation in Numerical Ocean Models
2009
Dushaw, Brian
Over the decade 1996-2006, acoustic sources located off central California and north of Kauai transmitted to receivers distributed throughout the northeast and north central Pacific. Some of the observations included "shadow-zone arrivals", that appear at travel times aligned with the lower cusps of the acoustic time front predicted by ray calculations, but with the depth of the receiver lies well below the depths of the predicted cusps. Several models for the temperature and salinity in the North Pacific Ocean were obtained and processed to enable simulations of acoustic propagation for comparison to the observations. New tools were developed to manage the large size of the model output, to extract and construct the relevant acoustic properties from the model output, and to make the acoustic calculations. Computer codes using ray tracing and the parabolic equation to calculate acoustic properties were significantly developed. The acoustic data show that WOA05 is a better estimate of the time-mean hydrography than either the JPL-ECCO or the POP estimates, which proved incapable of reproducing the observed acoustic arrival patterns.
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