Estimation of planetary wave parameters from the data of the 1981 ocean acoustic tomography experiment
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Using the maximum-likelihood estimation method and minimization techniques, quasi-geostrophic wave solutions were fitted to the observations of the 1981 Ocean Acoustic Tomography Experiment. The experiment occupied a 300 km square area centered at 26°N, 70°W, and had a duration of ~80 days. The data set consisted of acoustic travel-time records, temperature records and CTD profiles, obtained from the acoustic tomographic array, moored temperature sensors and recorders, and ship surveys, respectively. While the latter two were conventional spot measurements, the former corresponds to integral measurements of the temperature (or sound-speed) field. The optimal fit to the data corresponded to 3 waves in the first baroclinic mode, evolving under the presence of a westward mean flow with vertical shear. The flow was estimated to be weak (~2 cm/s), but it changed the wave periods significantly by producing large Doppler shifts. The waves were dynamically stable to the mean flow, had weak nonlinear interactions with each other and did not form a resonant traid; thus they constituted a fully linear solution. Evidence for the existence of the waves was strongly supported by the high correlation (~0.9) between the data and the fit, the large amount of signal energy resolved (~80 percent), the excellent quality of the wave-parameter estimate (only about 10 percent in error), and the general agreement between the observations and quasi-geostrophic linear dynamics.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1985
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