Characterizing water column variability and its impact on underwater acoustic propagation.

Abstract

During the Shallow Water Experiment 2006 (SW06), a low-frequency acoustic source was towed out and back along radials from a receiver array located at the origin. Measurements were made along three radials, separated by 45 deg, with each track repeatedly traversed over a period of 6–10 h. Concurrently with the acoustic measurements, the water column sound speed field was estimated both along the source track and at the receiver location. The objective was to fully characterize the environment in the water column over the acoustic path during transmissions. In this way, variability in the acoustic field measured along the repeated tracks could be associated with variability in the water column. The variability in the water column, measured independently at the source and at the receiver, is examined and related to variability observed in the acoustic fields. Spatial and temporal variability is characterized on transect-to-transect, radial-to-radial, and day-to-day basis. Over 3 days, variability in the water column could be attributed to thermohaline intrusions, linear and non-linear internal waves, as well as mesoscale variability. This talk will focus on the requirements for characterizing these features and understanding their impact on acoustic propagation and prediction. [Work supported by ONR.]