Acoustic Sensing of Ocean Turbulence

Abstract

The need for direct turbulence measurements in the upper ocean arise from widespread requirements to correctly parameterize momentum and scalar fluxes across the air/ocean interface. Until recently these observations were limited by a lack of instrumentation capable of measuring the fine-structure velocity field down to dissipation scales. The recently developed CDV package allows simultaneous sub-centimeter resolution measurements of temperature, conductivity, pressure, shear and the 3 component velocity field. As part of the development of this system a Monte-Carlo simulation was used to analyze the performance of several spectral estimators of the mean acoustic Doppler shifts, from which the velocity components are derived. The selected algorithms were implemented on a Digital Signal Processor allowing real-time estimation of the velocity, shear and scalar quantities. To verify the performance of the CDV package, it was deployed off Wharf 2 in Monterey for 24 hours while simultaneously recording meteorological data. Reynold's stresses, buoyancy fluxes and fine scale stratification were characterized and the surface gravity waves field identified.