| Lidar measurements of mesospheric Fe were conducted at Urbana, Illinois, during four nights in late October 1989. The average Fe abundances, layer centroid heights and rms widths varied between 1.0-2.0 {dollar}times{dollar} 10{dollar}sp{lcub}10{rcub}{dollar} cm{dollar}sp{lcub}-2{rcub}{dollar}, 89.0-90.5 km and 3.2-4.1 km, respectively. The peak densities of the layer near 90 km varied between 15-25 {dollar}times{dollar} 10{dollar}sp3{dollar} cm{dollar}sp{lcub}-3{rcub}{dollar}. On three nights the formation and dissipation of three large sporadic Fe (Fe{dollar}sb{lcub}rm s{rcub}{dollar}) layers were observed.; A new two-frequency lidar technique for measuring mesospheric Na temperature profiles is described. This system uses a stabilized cw single-mode dye laser oscillator (rms frequency jitter {dollar}<{dollar}1 MHz) followed by a pulsed dye power amplifier (140 MHz FWHM linewidth) which is pumped by an injection-seeded Nd:YAG laser. The laser oscillator is tuned to the two operating frequencies by observing the Doppler-free structure of the Na D{dollar}sb2{dollar} fluorescence spectrum in a vapor cell. The lidar technique and the initial observations are described. Absolute temperature accuracies at the Na layer peak of better than {dollar}pm{dollar}3 K with a vertical resolution of 1 km and an integration period of approximately 5 min were achieved in this initial experiment.; Fourteen nights of Na temperature lidar data spanning 6 months were collected at Urbana, Illinois, using the two-frequency technique. The temperature structure over the 80-100 km region was highly variable due to the influence of gravity waves, tides, and sporadic layers (Na{dollar}sb{lcub}rm s{rcub}).{dollar} Extreme temperatures of 140 K and 255 K were measured. A mesopause cooling rate of 9 K/month was exhibited from winter to summer at the mesopause height localized between 85 and 90 km. The temperature dependence of the Na column abundance is analyzed, and a 9 {dollar}times{dollar} 10{dollar}sp7{dollar} atoms/cm{dollar}sp2/{dollar}K Na abundance rate of change was observed from winter to summer. The rms perturbations, wave dynamics, and Brunt-Vaisala periods are also investigated.; The first observations of vertically resolved Na density, temperature, and wind profiles in the mesopause region were made using a new four-frequency Doppler/temperature lidar. The initial zonal wind and temperature observations were obtained with a profile resolution of 30 min and 1.5 km and rms accuracies of 12 m/s and 2 K. These measurements were conducted simultaneously with the medium frequency (MF) radar at the Urbana Atmospheric Observatory (40{dollar}spcirc{dollar}N, 88{dollar}spcirc{dollar}W) during the night of 14-15 March, 1991. Although both the lidar and radar wind measurements exhibited the same general trends, the velocity estimates differed by as much as 40 m/s at some times during the night. |
