Development of an arctic ray model.

Abstract

Recent additions to a previously developed ray model [E. K. Westwood and P. J. Vidmar, J. Acoust. Soc. Am. 81, 912–924 (1987); E. K. Westwood and C. T. Tindle, ibid. 81, 1752–1761 (1987)] have been completed. The inclusion of top layering above the user-specified ocean and bottom layer environment makes the updated model (ICERAY) applicable to ice-covered regions. Sources are specified in the ocean, while receivers may be located in either the ocean or top layers. The implementation consisted of the calculation of several ray types, and energy contributions from the various ray paths were analyzed independently. Compressional and shear rays were included in the ice. The analysis of evanescent waves showed them to be the most important for propagation to receivers in the ice from sources at longer ranges. The evanescent contribution was implemented by calculating an eigenray to a receiver just below the ice–water interface at the location of the actual ice-embedded receiver and including an appropriate transmission coefficient and exponential decay factor. Comparisons to the full-wave model SAFARI [H. Schmidt, SafariUser’sGuide, SACLANTCEN SR-113, NATO SACLANT Undersea Research Centre, La Spezia, Italy (1989)] demonstrated the accuracy of the ray model for various source and receiver geometries starting with simple environments and evolving to a realistic arctic environment. [Work supported by the Office of Naval Research and the Internal Research and Development Program of the Applied Research Laboratories, The University of Texas.]