Frank S. Henyey
Terry E. Ewart
Stephen A. Reynolds
Appl. Phys. Lab., Univ. of Washington, 1013 NE 40th St., Seattle, WA 98105
Univ. of Sydney, NSW, Australia
Conditions for which an acoustic ray turns in a strong thermocline occur in both shallow and deep water. Internal wave induced fluctuations in the acoustic propagation are expected to be particularly large for such rays. A shallow-water example is the Synthetic Aperture Sonar experiment of summer, 1996, modeled with historical data for the site. A deep-water example is the upper path at the MATE experiment done a number of years ago. Conditions of validity of the Markov approximation are unlikely to hold under such conditions. In particular, the range derivative of the correlation length tangent to the ray greatly exceeds unity for the MATE upper path. Other approximations may also be inaccurate. A program to investigate standard approximation schemes for the MATE upper path has begun, whose purpose is to try to improve theories for such conditions, and to serve as a comparison case for the shallow-water experiment. Various statistical quantities are to be calculated in simulations, and compared to the same quantity calculated with standard approximations.