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Ground‐based observations of atmospheric density profiles to 92 km were obtained for four successive seasons between summer 1989 and spring 1990. These results were obtained with a powerful Rayleigh lidar facility located at Wright Patterson Air Force Base (Dayton, Ohio). This instrument combined a 14‐W XeF laser transmitter with a 2.54‐m receiver mirror to observe returns from altitudes between 40 and 95 km. Analysis of the scale height dependence of the density profiles produced temperatures with a measurement error of about 5 K (∼2.5%) at 90 km when the lidar data was averaged for 20 min. and smoothed in height over 2.7 km. Examination of these profiles for the total of 18 nights showed that there often existed in the mesophere a layer of enhanced temperatures when compared with the U.S. standard profile. The layer centroid height was about 85 km for summer and 70 to 75 km for winter. Data obtained for the equinoctial periods showed the amplitude of these layers to be weak. The winter temperature profiles showed evidence forlong‐period waves passing through the region of the thermal anomaly while the equinox profiles revealed more sporadic wave activity with shorter vertical wavelengths. Both the winter and summer temperature data displayed regions where the observed lapse rate approached the adiabatic lapse rate. In the summer the wave activity near the inversion layer was weak.

The feasibility of lidar detection of noctilucent cloud (NLC) returns with the Rayleigh lidar technique was determined by calculations of lidar photocount profiles for the Nd:YAG lidar wavelength of 532 nm (Rayleigh temperature lidar). These results affirm the feasibility of the application of this instrument to study the high‐latitude summer phenomenon 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 the 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° was noted. At this time the sky was sufficiently dark, and if there had been any NLCs overhead, visual NLC sightings should have been possible. The lidar observations provided measurements of the middle atmosphere 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 standard model profile but with an increase of about 5% at the stratopause. Examination of the results for an indication of lidar Mie returns from NLCs was negative, which was consistent with the lack of visual detection.

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