Numerical Analysis of Acoustical Propagation in Ocean with Warm and Cold Water Mass Used by The Three-Dimensional Wide-Angle Parabolic Equation Method

Abstract

The three-dimensional parabolic equation method (3DPE) is useful for analyzing the three-dimensional transmission characteristics of the propagation sound in the Pacific Ocean which has a spatial temperature distribution caused by a warm or a cold water mass. Sound pulses passing through a spatial water mass are curved not only in the vertical direction but also in the horizontal direction because of the temperature gradient of the water mass. In ocean acoustical tomography, it is important to estimate the distribution of sound pressure on the sound fixing and ranging (SOFAR) axis, because a small number of sound sources and receivers are placed on the SOFAR axis. We obtained accurate results of sound pressure distribution on the SOFAR axis using three-dimensional (3-D) simulation, when the sound pulse passed through a spatial water mass. The calculations of underwater acoustical propagation for comparison in a cold or a warm water mass were carried out using by the 3DPE method to compare with the two-dimensional (2-D) calculation results. The maximum temperature fluctuation at the center of the water mass was assumed to be varied from -6.0 to 5.0°C. The propagation sound fields are a larger extent than shown by the estimation results of 2-D simulation.