Kevin D. Heaney
Planning Systems, Inc., McLean, VA 22102
W. A. Kuperman
B. Edward McDonald
Michael D. Collins
Naval Res. Lab., Washington, DC 20375
A propagation model that combines the horizontal refraction of the adiabatic mode solution and the accurate field computation of the parabolic equation (PE) method is applicable to long-range problems. In a previous application of this model, qualitative agreement was achieved for narrow-band data from the Heard Island Feasibility Test (HIFT). The broad-band extension of this model has been applied to two long-range propagation paths. Data have been analyzed from a single-slice tomography experiment that involved a 1000-km propagation path in deep water and a source centered at 250 Hz. These data were previously modeled with a WKB solution [Duda et al., J. Acoust. Soc. Am. 92, 939--955 (1992)], which breaks down for the lower modes in the sound channel. These results are in agreement with these data even for the arrivals associated with the lower modes. The Heard Island to Christmas Island propagation path of the HIFT has also been analyzed. Several features along this path cause significant mode coupling, including a sloping bottom near the source, the Antarctic Circumpolar Convergence, and a sea mount. Although there is variability in this data due to fluctuations, the observed dispersion and arrival structure is consistent with these results.