APPLICATION OF THE RAYLEIGH LIDAR TO OBSERVATIONS OF NOCTILUCENT CLOUDS

The feasibility of lidar detection of noctilucent cloud (NLC) returns with the Rayleigh lidar technique was determined by calculations of li dar photocount profiles for the Nd:YAG lidar wavelength of 532 nm (Ray leigh temperature lidar). These results affirm the feasibility of the application of this instrument to study the high-latitude summer pheno menon of NLCs. Rayleigh 532-nm lidar observations were carried out in Greenland for late July and August, 1990. Extended cloudiness hampered these measurements, and a display of NLCs was seen only on August 14- 15, 1990, out of a total of 11 nights. Examination of photographs of t he NLCs for this night indicates that the spatial distribution of the clouds was patchy and fragmentary. No visual detection of NLCs in the region of the zenith when the solar depression angle was 8.6-degrees w as noted. At this time the sky was sufficiently dark, and if there had been any NLCs overhead, visual NLC sightings should have been possibl e. The lidar observations provided measurements of the middle atmosphe re temperature from 25 km to about 70 km for times near local midnight . The shapes of these profiles agreed with that of the U.S. 76 standar d model profile but with an increase of about 5% at the stratopause. E xamination of the results for an indication of lidar Mie returns from NLCs was negative, which was consistent with the lack of visual detect ion.