Turbulence energy dissipation rates and inner scale sizes from rocket and radar data

Abstract

Estimates of turbulence energy dissipation rates and inner scale sizes have been obtained at altitudes of 80∼90 km, using simultaneous rocket and radar data from the STATE experiments. Spectral widths from radar Doppler spectra and the rocket‐derived temperatures were used to calculate the turbulence energy dissipation rate as a function of height; values generally ranged from 0.05 to 0.15 m2 s−3, with a long term average about 0.1 m2 s−3. The maximum observed energy dissipation rate was about 1.0 m2 s−3, but these occasional intense levels of turbulence lasted only a few minutes. The kinematic viscosity has been calculated from the rocket data, which was then used with the energy dissipation rates to estimate the turbulence microscale (η) as a function of height; values of about 1.5∼2.0 m were obtained from 80 to 87 km, with η increasing rapidly for heights above about 87 km. The inner scale for neutral turbulence is approximately 13 times η, which therefore possibly ranges from 20 to 26 m, which is in approximate agreement with other estimates for the mesosphere. This result shows that the 3‐m scattering wavelength for the Poker Flat Radar is well within the viscous subrange for neutral turbulence and raises questions as to why such large backscatterd signals are detected in the polar mesosphere. A companion paper (Kelley and Ulwick, this issue) discusses this within the context of the electron density fluctuation spectra measured during the STATE campaign.