Turbulence measurement from an autonomous underwater vehicle

Horizontal profiles of the microstructure of velocity and temperature were obtained with a large autonomous underwater vehicle (AUV) using two piezoel ectric shear probes, an FF07 thermistor, and three orthogonal accelerometer s mounted on a sting at the forward end of the vehicle. A winter field tria l in Narragansett Bay provided a run in the midwater pycnocline at 8-m dept h that contained a thermal front, an ascending profile to 3-m depth, and a run in the weakly stratified surface layer at this depth. Although shear sp ectra were strongly contaminated by narrowband vibrations produced by the m otor and actuators, this contamination was highly coherent with the measure d acceleration and was removed with standard signal processing techniques. The corrected spectra agreed well with the Nasmyth universal spectrum for w avenumbers up to 40 cpm. The estimated rate of dissipation of kinetic energ y varied from 0.8 to 250 X 10(-8) W kg(-1) and was consistent with the rate of production of turbulence by surface wind forcing and bottom stress.