Some consequences of turbulent dissipation on diurnal thermal tide

It is shown that the phase difference between the horizontal components of the wind velocity induced by the first diurnal propagating tidal mode between 90 and 100 km altitude is modified by turbulent diffusion. Experimental data are compared with calculations made by two different methods. The calculated results agree well with the data for a coefficient of eddy diffusion K = 5 × 10⁶ cm² s⁻¹ which is a realistic one at this altitude. Incidentally, it is shown that some measurements which have been interpreted as a presence of evanescent modes are probably due to an increase in vertical wavelength of the first propagating diurnal mode due to turbulent diffusion.