Upper stratospheric and mesospheric temperatures derived from lidar observations at Aberystwyth

Abstract

From lidar observations of relative atmospheric density above Aberystwyth (52.4°N, 4.1°W) upper stratospheric and mesospheric temperatures have been derived for a total of 93 nights between December 1982 and February 1985. Excellent agreement was found between radiances synthesised from these temperatures and those measured by satellite-borne instruments. Summer temperatures showed a smooth and regular variation with altitude and reasonably good agreement with the CIRA (1972) model atmosphere. By contrast, winter temperatures showed a much greater variability with altitude and greater changes from night to night, with the frequent occurrence of a large amplitude wave-like perturbation in the mesosphere with about 15 km vertical wavelength and amplitude about 20K between 60 and 80 km. Pronounced warmings of the stratosphere were observed during the three winters of observation. During the warming event occurring in early February 1983 the stratopause temperature increased to 303K at 43 km, while the major warming event of late December 1984/early January 1985 produced a stratospheric temperature gradient of 16K km −1 between 34 and 36 km. During the latter event a distinct local temperature minimum at 32.6 km was observed on New Year's Eve, this descending to 29 km by the following night and being accompanied by a lowering of the stratopause from 43 to 38.5 km in the same period. These results demonstrate the ability of the present technique to resolve the high stratopause temperatures and steep stratospheric temperature gradients which occur during stratospheric warmings, in marked contrast to the limited resolution achieved by satellite experiments.