A Planetary Wave Analysis Using the Acoustic and Conventional Arrays in the 1981 Ocean Tomography Experiment

Abstract

Using the maximum likelihood estimation method, quasi-geostrophic wave solutions are 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 over a duration of approximately 80 days. The dataset consists of acoustic travel-time records, moored temperature records and CTD profiles. The acoustic data correspond to integral measurements of the temperature (or sound speed) filed. The optimal fit to the data corresponds to three waves in the first baroclinic mode, evolving under the presence of a westward mean flow with vertical shear. The mean flow is found to be weak (approximately 2 cm s?1, but changes the wave periods significantly by producing large Doppler shifts. The waves are found to be dynamically stable to the mean flow, have weak nonlinear interactions with each other, and do not form a resonant triad; thus they constitute a fully linear solution. Evidence for the existence of the waves is strongly supported by the high correlation (approximately 0.9) between the data and the fit, the large amount of signal energy resolved (approximately 80%), the excellent quality of the wave-parameter estimate (only about 10% in error), and the general agreement between the observations and quasi-geostrophic linear dynamics.