(Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1988-08)
Rowe, Elizabeth Anne
In order to determine the efficacy of tomographic reconstructions of the ocean sound speed
structure in improving acoustic field predictions for source localization, a 150 km by 350
km volume of ocean 3000 meters deep was synthetically modeled to be similar to the Gulf
Stream system, including an eddy and a front. The features were Gaussian, with the eddy's
maximum sound speed perturbation being 10ms-1 and the front's maximum perturbation
15ms-1. Two vertical slices through this system were inverted in a synthetic tomography
experiment using linear optimal estimation theory. Inversions were also performed using
XSV and satellite sea surface temperature data. Gaussian fits to the reconstructed features
were constructed for use with a three dimensional raytrace program (HARPO). Three dimensional
rays were propagated both through the reconstructions and the original model.
Travel time versus intensity (transmission loss) for the eigenrays was used as a basis for
intercomparison. Tomographic results showed good reconstruction for a first iteration of
the inversion, but inadequate vertical resolution. Iterations and the use of more refractive
eigenrays are needed for improvement of the reconstruction, especially for the front. Reconstructed
results for the acoustic field should improve conventional beamforming, but are
probably inadequate for matched field processing.
