Rayleigh lidar observations of mesospheric inversion layers at poker flat,Alaska (65 degrees N, 147 degrees W)

Rayleigh lidar measurements of the stratosphere and mesosphere have been ma de on an ongoing basis over a three-year period at Poker Flat, Alaska (65 d egrees N, 147 degrees W). These observations have yielded 27 nightly measur ements of the middle atmosphere temperature profile (similar to 40-80 km). These nighttime measurements are distributed between August and April. Meso spheric inversion layers have been observed on five occasions. The average altitude of the inversion layer peak is 60 km, with average amplitude of 18 K. The temperature gradients on the topside of the inversion layers approa ch the adiabatic lapse rate. The inversion layers do not exhibit the appare nt downward phase velocities that are commonly observed at lower latitudes. Furthermore, the inversion layers appear significantly less frequently tha n at lower latitudes. The observations are discussed in terms of current mo dels and observations at other sites.