A study of the sensitivity of the Greenland Sea acoustic tomography array.
Miller, James H.
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An acoustic tomography array consisting of six transceiver moorings was jointly deployed by Woods Hole Oceanographic Institution and Scripps Institution of Oceanography in the Greenland Sea during the second half of 1988. Two of the primary objectives of this thesis are: (1) to set up and test a stochastic 3-D inversion code for the Greenland Sea Acoustic Tomography data analysis; and (2) to evaluate the performance of the acoustic system through resolution and variance analyses. In acoustic tomography, the sound speed perturbation field is estimated from measured acoustic travel time perturbation data. A unique sound speed perturbation estimate can be constructed using the Guass-Markoff theorem. However, the theorem requires the specification of the covariance of the sound speed perturbation field, which is generally not exactly known. Via computer simulation, we examined the sensitivity of the estimate to uncertainty in the sound speed field correlation specified. In addition, we also examined the effects of an increased random experimental noise level and a change in array geometry due to mooring failure on the estimate. The three major results are that: (1) the estimate is less sensitive to a positive uncertainty in correlation length than to a negative uncertainty in an ocean volume containing large structures, while it is more sensitive to a positive uncertainty than to a negative uncertainty in an ocean volume containing small structures; (2) the estimate error is primarily bias error rather than random error; and (3) the failure of a mooring causes a large increase in RMS error in regions no longer containing acoustic rays, but it results in an increase in RMS error of only 25% in regions which still contain acoustic rays.
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