LIDAR-OBSERVED TEMPERATURE STRUCTURES AND GRAVITY-WAVE PERTURBATIONS OF THE MESOPAUSE REGION IN THE SPRINGS OF 1990-1992 OVER FORT COLLINS,CO

The Na temperature lidar data taken during the nine nights in springs 1990 and 1991 at Fort Collins, CO, have been re-analyzed by a refined procedure, which takes into account the effects of (i) the more accura tely determined lidar operational frequencies, (ii) the proper inclusi on of extinction in the Na layer and (iii) additional temporal and spa tial smoothing. Depending on altitudes, the new lidar frequencies and the effect of Na extinction combined to lower the calculated temperatu re values by 2-8 K. Although the occasionally noted large rapid change (in 15 min) in the centroid temperature is reduced from approximately 40 K to approximately 20 K due to the added smoothing first employed by Bills and Gardner, the general conclusion presented in the recently published paper [1] remains valid. In this paper, we also present the analysis of new data (a total of 17 nights) taken during spring 1992 which further substantiates the fact that the averaged mesopause in sp ring rises from a lower altitude before midnight to a higher altitude after midnight. In addition, parameters depicting atmospheric gravity- wave perturbations have been derived from the measured temperature pro files. Using the data collected in 26 spring nights, we have determine d the averaged relative density (temperature) perturbation, Brunt Vais ala period and Richardson number to be, respectively, 5.1 +/- 1.1%, 5. 1 +/- 0.3 min, and 1.8 +/- 1.0.