A range-dependent analysis of acoustic transmission across a cold filament in the California Current.

Abstract

CTD data were taken in a area where satellite imagery had detected a cold water filament to frequently recur in the California Current System in order to determine the temporal and spatial variability of the hydrographic and velocity fields. Sound speed profiles were constructed from this data and predicted sonar ranges (PSRs) were computed for passive sonar using a range-dependent parabolic equation model. Analysis of model results applied to tactical scenarios showed the acoustic advantage between two adversaries to change as their positions relative to the front and to each other were changed. An investigation of the acoustic mechanisms involved in the variation of PSRs showed that small variations in surface temperature were enough to cause significant changes in PSRs. Changes in temperature of sufficient magnitude to effect PSRs were found also in SST imagery of cold filaments in other eastern boundary currents around the world.