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Optimum Inversion of Mesoscale Velocity Fields for the Ocean Acoustic Tomography

 

J.-H. Park and A. Kaneko

Faculty of Engineering, Hiroshima University

Higashi-Hiroshima, Hiroshima 739-8527, Japan

 

Abstract

 

Computer simulations of the ocean acoustic tomography with five, seven and nine transceivers are applied to two-dimensional mesoscale eddy stream function fields of horizontal domain 300km×300km. As the a priori information on stream function fields is difficult to be acquired, the travel time data obtained between all pairs of transceivers are analyzed by the damped least squares method instead of the stochastic inverse method to reconstruct the eddy fields. The optimum values of weighting factor appearing in the inversion are determined by applying the L-curve which describes the size of solution versus the size of the corresponding residual and by searching the point where the curvature of the L-curve is maximum. The application of this method for the real coastal ocean region also shows good estimation result.

 

1. Introduction

 

The ocean acoustic tomography is now developing quickly as a modern technology to image mesoscale temperature structures in the ocean (Kaneko et al. 1994; Morawitz et al. 1996; Gaillard et al. 1997; Yuan et al. 1999). The temperature tomography uses as data the travel time for one-way transmitted sound or the mean of the travel times for reciprocally transmitted sound, while the travel time difference between reciprocally transmitted sounds is used for the velocity tomography. In contrast with the temperature tomography which needs the precise positioning accuracy, the precise clock accuracy is required for the velocity tomography.

This study is concerned with the computer simulation of the ocean acoustic tomography of mesoscale velocity fields which deals with only a barotropic mode as a simplest case for reducing computational time. The optimum condition of inversion for the velocity field tomography is investigated with a barotropic ocean model in which eddies on various scales are included.

 

 

 

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