A quasi-continuous survey of the stratospheric and mesospheric temperature was performed, between June 1981 and April 1982, using the lidar station of the Observatory of Haute-Provence (44°N,6°E). During the period of easterly winds in the lower stratosphere (i.e., from June to September), the variability of the temperature is observed to be very low. As long as prevailing winds are westerlies, from October to March, temperature profiles are continuously perturbed by planetary waves, with a maximum of amplitude in January 1982, before the `strong minor warning' of the winter. Spectral analysis of the data indicates the presence of a well-defined 18-day wave interpreted as a free Rossby wave and the existence of large perturbations with periods of 25 to 40 days which are tentatively explained as a succession of minor upper stratospheric warmings due to the interference of the 18 day traveling Rossby wave and a stationary wave.