Lidar measurements taken with a large-aperture liquid mirror. 2. sodium resonance-fluorescence system

Sodium resonance-fluorescence lidar is an established technique for measuring atmospheric composition and dynamics in the mesopause region. A large-power-aperture product (6.6-W m²) sodium resonancefluorescence lidar has been built as a part of the Purple Crow Lidar (PCL) at The University of Western Ontario. This sodium resonance-fluorescence lidar measures, with high optical efficiency, both sodium density and temperature profiles in the 83-100-km region. The sodium lidar operates simultaneously with a powerful Rayleigh- and Raman-scatter lidar (66Wm²). The PCL is thus capable of simultaneous measurement of temperature from the tropopause to the lower thermosphere. The sodium resonancefluorescence lidar is shown to be able to measure temperature to an absolute precision of 1.5 K and a statistical accuracy of 1 K with a spatial-temporal resolution of 72 (km s) at an altitude of 92 km. We present results from three nights of measurements taken with the sodium lidar and compare these with coincident Rayleigh-scatter lidar measurements. These measurements show significant differences between the temperature profiles derived by the two techniques, which we attribute to variations in the ratio of molecular nitrogen to molecular oxygen that are not accounted for in the standard Rayleighscatter temperature analysis.