Numerical analysis of acoustical propagation characteristics in Central Equatorial Pacific Ocean with ridges of seabed used by three-dimensional parabolic equation method

Ocean acoustic tomagraphy (OAT) using sound propagation times in the ocean is a useful observation system to determine the actual temperature of water . OAT needs an adequate numerical method of sound propagation to obtain the prior information about the ocean. We reported about the wide-angle parabo lic equation (PE) calculation method for long-range propagation. However, i f the ridges on a seabed exist near the SOund Fixing And Ranging (SOFAR) ax is, it blocks sound pulses passing near the SOFAR axis. Sound pulses are re flected not only in the vertical direction such as sea surface, but also in the horizontal direction because of ridges of seabed. Two-dimensional (2-D ) analysis of the sound pressure distribution many have a slight error behi nd ridges or islands. Therefore, it is necessary to consider the sound prop agation characteristics using the three-dimensional parabolic equation (3-D PE) calculation method but the 2-DPE calculation method. We obtained accura te results for sound pressure distribution on the SOFAR axis using 3-DPE ca lculation method, when the sound pulse was blocked by the seabed. The calcu lation results of underwater characteristics by 3-DPE calculation were comp ared with those of the 2-DPE calculation method.