Turning point filters: Analysis of sound propagation on a gyre-scale

Acoustic transmissions from Pioneer Seamount off California to a vertical a rray near Hawaii are analyzed using a technique which we call a turning-poi nt filter. The observables, travel time and axial inclination, are interpre ted in terms of the ocean sound-speed field. The method permits a uniform t reatment of the arrival pattern, from the early ray-like arrivals to the la te mode-like arrivals, including peak arrivals which cannot be identified a s either rays or modes. An adiabatic range dependence is assumed, and Wentz el-Kramers-Brillouin-Jeffreys formalism is applied. (C) 2001 Acoustical Soc iety of America.