Constructing Three-dimensional Ray Paths ForUnderwater Sound From Heard Island ToAscension Island

Abstract

For the prediction of global ocean sound propagation, a set of three-dimensional (3-D) ray equations have previously been derived [J. Yan, and K. Yen, J. Acoust. Soc. Am, 97, 15381544 (1995)]. The new equations take into account the curvature of an ellipsoidal earth, as well as horizontal refraction, so that for long-range transmissions they are more accurate than conventional ray equations. In this paper, the new ray equations are used to compute 3-D ray paths for underwater sound propagation from Heard Island to Ascension Island. A measured sound speed data base is used for this computation. The fourth-order Runger-Kutta method with adaptive step-size control is used to solve the ray equations. At every step of the numerical integration, sound speed is estimated by using 3-D interpolation of the measured sound speed data. Eigenrays are constructed using Successive Shooting Method. The vertical paths of the eigenrays are presented. The propagation range is about 9223 km. The computed travel times range from 6252.5 s to 6258.3 s, which are in good agreement with the measurement (6257 s).