Abstract:
With the emphasis of USW shifting to littoral environments, the understanding and, ultimately, prediction of acoustic propagation in the vicinity of the shelf break become increasingly important. The sloping bathymetry, the extreme seasonal changes in the vertical sound-speed structure, and the significant horizontal variability generated by the shelf-break front are just a few of the environmental factors that make this problem both interesting and complex. An ONR-sponsored field study known as PRIMER is designed to examine the influence of both the shelf-break front and the sloping bathymetry on propagation onto the shelf in the vicinity of the mid-Atlantic Bight. Recent results using a three-dimensional (3-D) acoustic ray model suggest that 3-D effects are not observable directly upslope but could be significant along tracks oblique to the continental slope. A more thorough investigation of these influences on pulse propagation has been performed using an advanced, full-wave, 3-D parabolic equation model. Specifically, this analysis will focus on the predictability of the 3-D, broadband acoustic wave fields in a complex shallow-water environment, and the dependence of those effects on acoustic frequency. A description of the data to be examined will also be provided. [Work supported by ONR Code 321OA.]