Three‐dimensional ray trace studies over a rough ocean bottom topography

Abstract

In sea areas where long‐range acoustic propagations involves repeated bottom reflection, it is essential to consider the three‐dimensional aspect of the reflection. Computational methods by DeWitt [J. Acoust. Soc. Am. 62, S19(A), (1977)] have been extended to include horizontal changes in the sound speed profile and bottom loss at each reflection. It is now possible to study horizontal ray deflections in areas containing a mid‐ocean ridge. An area of 120 000 km2 of sea bottom is represented by triangular facets developed from a grid of bathymetric points at one km intervals. This completely describes the bottom to the degree that it is presently known from the best existing charts. Sound speed profiles can change at large zone boundaries but horizontal refraction is neglected. Bottom reflection losses are calculated as a function of grazing angle for each bottom bounce of the ray. Rays which have accumulated a loss greater than a selected threshold can then be discontinued. Illustration and conclusions of the study will be given.