Lidar measurements of mesospheric temperature inversion at a low latitude

The Rayleigh lidar data collected on 119 nights from March 1998 to February 2000 were used to study the statistical characteristics of the low latitud e mesospheric temperature inversion observed over Gadanki (13.5 degrees N, 79.2 degrees E), India. The occurrence frequency of the inversion showed se miannual variation with maxima in the equinoxes and minima in the summer an d winter, which was quite different from that reported for the mid-latitude s. The peak of the inversion layer was found to be confined to the height r ange of 73 to 79 kin with the maximum occurrence centered around 76 km, wit h a weak seasonal dependence that fits well to an annual cycle with a maxim um in June and a minimum in December. The magnitude of the temperature devi ation associated with the inversion was found to be as high as 32 K, with t he most probable value occurring at about 20 K. Its seasonal dependence see ms to follow an annual cycle with a maximum in April and a minimum in Octob er. The observed characteristics of the inversion layer are compared with t hat of the mid-latitudes and discussed in light of the current understandin g of the source mechanisms.