THE FNWF SOUND MAP PROGRAM 



Captain Paul M, Wolff, U.S. Navy 



LCDR Peter R. Tatro, U. S. Navy 



LCDR Louis D. Megehee, Jr., U. S. Navy 



Fleet Numerical Weather Facility 



Monterey, California 



ABSTRACT 



A high precision computer ray trace program developed at the 

 Fleet Numerical Weather Facility in Monterey is used as a research 

 tool to investigate the effects of temperature and salinity variations 

 on the path of sound through the sea. In one case, the temperature 

 profile as a function of depth is described in terms of its basic 

 parameters: sea surface temperature , mixed layer depth, thermocline 

 gradient, and 400 meter temperature. These are systematically 

 varied, individually and in combinations, to determine their effect on 

 convergence zone formation. 



In a second case, a highly detailed cross-section of the Gulf 

 Stream taken by XBT's is used to demonstrate the effect of water mass 

 and current boundaries on convergence zone propagation. 



INTRODUCTION 



A ray tracing program developed at the Fleet Numerical Weather 

 Facility for use on the CDC 1604, 3200 and 6400 computers has been 

 used as a research tool to investigate the effects of oceanic 

 variability on the paths of sound through the sea. The program is a 

 highly sophisticated one incorporating a correction for the curvature 

 of the earth and utilizing a time step of l/128th of a second or less. 

 It operates in two dimensional x - z space, and is capable of 

 accepting any arbitrary specification of the sound velocity in x and z. 

 This represents a significant improvement over earlier numerical ray 

 trace programs , many of which were capable of handling only linear 

 gradients of sound velocity or sound velocity profiles which could be 



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