Recent observations of mesospheric temperature inversions over a tropical station (13.5°N, 79.2°E)

Present study mainly deals with recent observations of mesospheric temperature inversions (MTI) over Gadanki (13.5degreesN, 79.2degreesE), a tropical station in India using for about 40 months of Nd:YAG lidar data. Long-term measurements of halogen occultation experiment, high resolution Doppler imager on board upper atmospheric research satellite and solar mesospheric explorer have been used to compare the characteristics (amplitude, height and percentage of occurrences) of the inversions observed with ground-based lidar measurements for the first time. In general, the height and percentage occurrence of the inversions are matching well between ground and satellite based measurements most of the time and there exists a large discrepancy in the amplitudes of MTI measured by these instruments as expected. The height occurrence of these inversions is at similar to 76 km and for about 60% of the time, strong inversions can be seen at this tropical latitude. The height occurrence of the inversions shows annual oscillation with peak during summer and minimum in winter. The percentage occurrences of these inversions are showing semi-annual oscillation with peak during equinoxes and minimum during solstice. The possible causative mechanism for the frequent occurrence of these inversions over this tropical latitude are explained in light of current understanding of the gravity wave activity and also with the chemical heating/cooling taking place at these heights. (C) 2003 Elsevier Science Ltd. All rights reserved.