RAYLEIGH LIDAR SYSTEM FOR MIDDLE ATMOSPHERE RESEARCH IN THE ARCTIC

A Rayleigh/Mie lidar system deployed at the Sondrestrom Atmospheric Re search Facility located on the west coast of Greenland near the town o f Kangerlussuaq (67.0 deg N, 50.9 deg W) has been in operation since 1 993 making unique observations of the arctic middle atmosphere. The ve rtically directed lidar samples the elastically back-scattered laser e nergy from molecules (Rayleigh) and aerosols (Mie) over the altitude r ange from 15 to 90 km at high spatial resolution. The limited amount o f arctic observations of the middle atmosphere currently available emp hasizes the importance and utility of a permanent Rayleigh lidar syste m in Greenland. The lidar system consists of a frequency-doubled, 17-W Nd:YAG laser at 532 nm, a 92 cm Newtonian telescope, and a two-channe l photon counting receiver. The principal objective of the lidar proje ct is to contribute to studies concerned with the climatology and phen omenology of the arctic middle atmosphere. To this end, we describe th e lidar system in detail, evaluate system performance, describe data a nalysis, and discuss the system capabilities in determining the densit y, temperature, and the presence of aerosols in the arctic middle atmo sphere. Particular emphasis is placed on the derivation of temperature from the lidar measurement and on the impact of signal-induced noise on this analysis. Also, we develop a statistical filter based on a Bay esian approach to optimally smooth the lidar profile in range. This fi lter preserves the short-term fluctuations in the low-altitude data co nsisting of relatively high SNR, whereas more smoothing is applied to the high-altitude data as the SNR decreases. (C) 1997 Society of Photo -Optical Instrumentation Engineers.