TEMPERATURE VARIABILITY OVER THE TROPICAL MIDDLE ATMOSPHERE

A study on the variability of temperature in the tropical middle atmos phere over Thumba (8 32' N, 76 52'E), located at the southern part of India, has been carried out based on rocket observations for a period of 20 years, extending from 1970 to 1990. The rocket-sonde-derived mea n temperatures over Thumba are corrected prior to 1978 and then compar ed with the middle atmospheric reference model developed from satellit e observations and Solar Mesosphere Explorer (SME) satellite data. Tem perature variability at every 1 km interval in the 25-75 km region was analysed. The tropical stratospbere is found to be highly stable, whe reas considerable variability is noted in the middle mesosphere. The e ffect of seasonal cycle is least in the lower stratosphere. Annual and semi-annual oscillations in temperature are the primary oscillations in the tropical middle atmosphere. Annual temperature oscillations are dominant in the mesosphere and semiannual oscillations are strong in the stratosphere. The stratopause region is noted to be the part of th e middle atmosphere least sensitive to the changes in solar activity a nd long-term variability.