Rayleigh lidar observations of a mesospheric inversion layer during night and day

A narrow field of view Rayleigh lidar has been constructed at Millstone Hil l / MIT Haystack Observatory (42.6 degreesN, 71.5 degreesW) for observation s of middle atmospheric temperatures throughout the diurnal cycle. During a 31.5 h measurement on 19-21 March 2001 a mesospheric thermal inversion lay er was observed in both the night and day. It developed near 60 km in altit ude, progressed downward at 0.40 +/- 0.06 km/h, and had an overlying adiaba tic lapse rate. The inversion amplitude correlated with the evolution of st ratospheric gravity wave activity, although the mesospheric perturbations w ere too large to be due to conservative gravity-wave growth alone. The 24 h mean temperature profile shows no evidence of a residual inversion layer.