SEMIDIURNAL AND DIURNAL TIDAL EFFECTS IN THE MIDDLE ATMOSPHERE AS SEEN BY RAYLEIGH LIDAR

The Rayleigh lidar at the Centre d'Essais des Landes has been adjusted to provide continuous day and nighttime measurements when clear weather permits with high resolution in both time and space. These measurements are processed to show tidal effects in the 30- to 80-km height range. The observed temperature variations in two 11-day series of data, from November 1988 and January 1989, are treated by spectral analysis and by least squares fitting sinusoids for 12- and 24-hour periods. The observed tidal amplitudes correspond with experimental results from rocket studies and are generally consistent, though somewhat larger than predicted in theoretical models. Observed lidar phases are roughly corroborated by radar observations and also follow the same general trends as model predictions.