Mesospheric temperature inversions observed in long-term Iidar measurements at mid- and low-latitudes.

Abstract. Results of an investigation of mesospheric temperature inversion layers using long-term lidar measurements at mid- and low-latitudes are reported. Observations of inversions above Table Mountain, California, (34.4”N) and Mauna ha, Hawaii, (19.5”N) are in very good agreement with previous lidar and satellite observations. At least two distinct types of events have been observed. The winter inversions occur near 70 km altitude at rnidlatitudes in Deccmbcr-January and about 1-2 months later at subtropical latitudes. Also, some higher altitude inversions (80-85 km) have been observed at lower latitudes around the equinoxes and 1-2 months later at mid-latitudes. Several previously proposed mechanisms for the formation of these inversions are reviewed, including gravity wave breaking and tidal effects. 1