A ray variability analysis of sound transmission from Heard Island to California. Free

In support of the Heard Island experimental effort, the influence of mesoscale and seasonal ocean variability on three‐dimensional acoustic ray paths from Heard Island through the Indian and Pacific Oceans to the California coast is investigated. For the simulation of these global acoustic ray paths, a three‐dimensional Hamiltonian ray tracing code is used. The input sound‐speed fields to the acoustic ray model are interpolated from gridded temperature and salinity output data from the Semtner–Chervin eddy‐resolving, global, general circulation model. A previous ray analysis was conducted using ocean fields containing only the mesoscale variability. This analysis provided input to experimental planners for receiver placement off the California coast [C. S. Chiu and A. J. Semtner, J. Acoust. Soc. Am. Suppl. 1 88, S92–S93 (1990)]. Here, a new analysis is presented that includes the acoustic effects of ocean seasonal cycles. In particular, the variability of the paths, arrival azimuthal angles, and travel times are discussed.