Mesospheric temperature inversions over the Indian tropical region

To study the mesospheric temperature inversion, daily temperature profiles obtained from the Halogen Occultation Experiment (HALOE) aboard the Upper Atmospheric Research Satellite (UARS) during the period 19912001 over the Indian tropical region (0-30degrees N, 60-100degrees E) have been analyzed for the altitude range 34-86 km. The frequency of occurrence of inversion is found to be 67% over this period, which shows a strong semiannual cycle, with a maximum occurring one month after equinoxes (May and November). Amplitude of inversion is found to be as high as 40 K. Variation of monthly mean peak and bottom heights along with amplitude of inversions also show the semiannual cycle. The inversion layer is detected most frequently in the altitude range of 70-85 km, with peak height ranging from 80 to 83 krn and that of the bottom height from 72 to 74 km. A comparison of frequency of temperature inversion with that obtained from Rayleigh lidar observations over Gadanki (13.5degrees N, 60-100degrees E) is found to be reasonable. The seasonal variation of amplitude and frequency of occurrence of temperature inversion indicates a good correlation with seasonal variation of average ozone concentration over the altitude range of the inversion layer.