Turbulence dissipation rates and vertical diffusivity in the stratosphere from radar observations

Abstract

The turbulence parameters in the stratosphere are estimated from the backscattered power of VHF radar at the Observatoire de Haute-Provence (OHP). Under the classical hypothesis of homogeneous and isotropic turbulence, we propose a slightly different method for extracting turbulent dissipation rates from radar measurements. The temperature structure parameter, C2T, and the diffusivity, Kz are directly expressed as a function of the dissipation rate of half temperature variance, ϵθ, (and not from the dissipation rate of kinetic energy), this approach appearing weakly dependent on unknown parameters (as the mixing efficiency Rf/(1 − Rf) where Rf is the flux Richardson number and the vertical stratification ∂θ/∂z). Our estimations of ϵθ and Kz are of the same order as aircraft and balloon measurements and considerably weaker than radar measurements using the bandwidth of the Doppler spectrum.