Resonance lidar system for mesospheric sodium measurements

Abstract

This paper describes a newly developed resonance lidar system at Gadanki (13.5°N, 79.2°E), India. The lidar system is set up to probe the natural layer of neutral sodium atoms existing between 80 and 110 km. The lidar employs a YAG pumped dye laser as a transmitter. The laser is tuned to the sodium D2 line at 589.0 nm. The lidar achieved first light on 10 January 2005 and made the first mesospheric sodium measurements from India. The lidar-measured vertical profiles of resonant backscatter are found to have sufficient signal strength for deriving the mesospheric sodium concentration profiles. Using the system, sodium concentration profiles are obtained with a vertical resolution of 300 m and a time integration of 120 s. These features allow the system to detect the time and space variability of Na concentration profiles. During the initial six nights of observation, the average nocturnal columnar abundances were in the range (2 to 8.3)×109 cm−2. The nightly mean centroid heights range between 92.7 and 95.1 km, and the rms widths vary between 4.3 and 4.9 km. The preliminary analysis of Na layer dynamics on 10 January 2005 shows the presence of wavelike structures with characteristics similar to those of propagating gravity waves. The preliminary analyses of data show a considerable variability in Na concentration distribution in the mesopause region during a sporadic Na event.