Determination of the Rate of Dissipation of Turbulent Energy from Simultaneous Temperature and Velocity Shear Microstructure Measurements

Abstract

Spectra of turbulence have been examined for both temperature gradient and velocity shear. The data for this comparison are to-IS m segments of vertical microstructure profiles (at depths of 5-100 m) obtained during the 1978 Joint Air Sea Interaction experiment (JASIN). From the simultaneous measurement of these two microstructure quantities, the. universal spectral constant q (the least principal rate of strain of the velocity spectrum) has b~n determined to be 3.7 ± 1.5. As well, the dissipation rate has been calculated from the high-wavenumber cut-off of the temperature microstructure spectra (fa) and from velocity shear (ESH). For a range of values from 8'X 10-9 to 5 X 10-7 m2 5-3 these two measures, f~ and ESH, agree to within a factor of 2 on average. And finally, estimates of Xe (temperature dissipation rate), f and mean temperature gradient have been used to estimate a mixing efficiency, r '" 0.24.