The turbulence parameters in the upper troposphere - lower stratosphere are estimated from the backscattered power of a VHF radar located at the Observatoire de Haute-Provence (OHP). Under the classical framework of locally homogeneous and isotropic turbulence, we propose a slightly different method for estimating the turbulent diffusivity from radar measurements. The temperature structure parameter, CT2, and the vertical heat diffusivity, K&thgr;, are expressed as a function of the dissipation rate of the temperature variance, &egr;&thgr; (and not from the dissipation rate of kinetic energy). This parameter appears weakly dependent on unknown quantities such as the mixing efficiency Rf/(1-Rf) (Rf is the flux Richardson number) and the vertical stratification ∂&thgr;¿/∂z. Our estimations of &egr;&thgr; are of the same order as in situ measurements. The inferred diffusivity K&thgr; appears considerably weaker (one order of magnitude) than radar estimates using the bandwidth of the Doppler spectrum. ¿ 2000 American Geophysical Union