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

Abstract. A narrow field of view Rayleigh lidar has been constructed at Millstone Hill / MIT Haystack Observatory (42.6◦N, 71.5◦W) for observations of middle atmospheric temperatures throughout the diurnal cycle. During a 31.5 h measurement on 19-21 March 2001 a mesospheric ther-mal inversion layer was observed in both the night and day. It developed near 60 km in altitude, progressed downward at 0.40 ± 0.06 km/h, and had an overlying adiabatic lapse rate. The inversion amplitude correlated with the evolution of stratospheric gravity wave activity, although the meso-spheric perturbations were too large to be due to conserva-tive gravity-wave growth alone. The 24 h mean temperature profile shows no evidence of a residual inversion layer