Observations of the Upper Ocean Using a Multi-Beam Doppler Sonar

摘要

This dissertation presents several different applications of Doppler sonar measurements. Data were collected from four downward-slanting sonars operated on the Research Platform FLIP. The sonars provide profiles of backscattered intensity and slant velocity from approximately 100 m to 1000 m in depth with 20 m depth resolution. A technique to measure the vertically-acting Reynolds stresses, (u'w') ave and (v'w') ave, in the oceanic internal wave field using a multibeam Doppler sonar is presented. The stress measurement technique is applied to the Doppler velocity data collected during the experiment. The principal result is a lack of observed Reynolds stresses in the high vertical wavenumber, high frequency internal wave band which can be considered significantly different from zero, despite the use of a scale separation which is more restrictive than that of previous investigators, and the consideration of stresses on several different time scales. A characterization of the diurnal migration patterns of acoustic scattering layers based on the Doppler sonar measurements is presented. The effects of the diurnal migration of scatters are evident in both backscattered intensity and Doppler velocity, and two measurements provide complementary methods of analysis. The principal result is the observation of three distinct scattering layers whose patterns of vertical migration show a high degree of persistence in both space and time.