Vertical structure and arrival times of the axial wave based upon conductivity, temperature, and depth data acquired during the Long‐range Ocean Acoustic Propagation Experiment

Abstract

In the LOAPEX experiment at some distances from VLA the sound source was deployed to depths quite close to the sound‐channel axis. This took place at stations T1000, T500, T250, and T50 where, in particular, the source was deployed to 800 m and the depth of the sound‐channel axis at these ranges is about 680 m. The interference of the wave fields corresponding to near‐axial rays leads to formation of a complex interference wave (‘‘the axial wave’’) that propagates along the axis being a component of the axial crescendo. The talk will present the results on simulation of the axial wave as a function of depth of the receiver and the calculation of its arrival time at frequencies 56.25–93.75 Hz. In the time domain the pulse propagation modeling is carried out for the broadband acoustic signals with the pulse center frequency of 75‐ and 37.5‐Hz bandwidth. The obtained results are compared with those for the lowest mode in the adiabatic approximation. Calculations are made for the range‐dependent ocean model based upon LOAPEX CTD data and use the integral representation of the axial wave in a local coordinate system introduced in the vicinity of the range‐variable sound‐channel axis. [Work supported by ONR.]