Effect of a Rossby wave on the phase of an underwater acoustic signal

The effects of sound-speed variations, produced by an assumed Rossby wave, on ray geometry, travel time, and spreading loss are investigated for an ocean region such as the Sargasso Sea. A horizontally discretized sound-speed model is used, and a bottomed source and receiver are assumed. The phase of the total acoustic field is examined, and it is found that the major effects of the Rossby wave arise through travel-time variations. The period of the phase is that of the Rossby wave, and a formula for maximum phase variation is presented. In an example, the Eleuthera-Bermuda area is modeled approximately, and the total-field phase variation is examined as a function of Rossby wave propagation direction. The phase variation and period are highly sensitive to this direction, to the choice of parameter values, and to source and receiver depth.