A modal/WKB inversion method for determining sound speed profiles in the ocean and ocean bottom
A modal/WKB inversion method for determining sound speed profiles in the ocean and ocean bottom
Date
1988-06
Authors
Casey, Kevin D.
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Date Created
Location
Gulf of Mexico
DOI
10.1575/1912/4803
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Keywords
Underwater acoustics
Sound
WKB approximation
Sound
WKB approximation
Abstract
Two approaches to determining the ocean sound speed profile using measured acoustic modal
eigenvalues are examined. Both methods use measured eigenvalues and mode dependent
assumed values of the WKB phase integral as input data and use the WKB phase integral
as a starting point for relating the index of refraction to depth. Inversion method one is
restricted to monotonic or symmetric sound speed profiles and requires a measurement of the
sound speed at one depth to convert the index of refraction profile to a sound speed profile.
Inversion method two assumes that the sound speed at the surface and the minimum sound
speed in the profile are known and is applicable to monotonic profiles and to general single
duct sound speed profiles. For asymmetric profiles, inversion method two gives the depth
difference between two points of equal sound speed in the portion of the profile having two
turning points, and in the remainder of the profile it gives sound speed versus depth directly.
A numerical implementation of the methods is demonstrated using idealized ocean sound
speed profiles numerical experiments used to test the performance of the inversions using
noisy data. The two methods are used to determine the sediment sound speed profiles in
two shallow water waveguide models, and inversion method one is used to find the sediment
sound speed profile using data from an experiment performed in the Gulf of Mexico.
Description
Submitted in partial fulfillment of the requirements for the degree of Ocean Engineer at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 1988
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Citation
Casey, K. D. (1988). A modal/WKB inversion method for determining sound speed profiles in the ocean and ocean bottom [Doctoral thesis, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution]. Woods Hole Open Access Server. https://doi.org/10.1575/1912/4803