A case of sudden variation in nocturnal mesospheric temperatures: Variability and its causative mechanism

We report nighttime mesospheric OH and O2 temperature measurements during 21–29 April, 2009, over Gadanki (13.5°N, 79.2°E), India. Large night-to-night variability is observed, which is dominated by large amplitudes of short period gravity wave features. It is noted that on 21 and 23 April 2009, the mean nocturnal temperature values for OH emissions altitudes were higher than the O2 emissions, which reversed on 27 April 2009. Further, the wavelet analysis of nighttime mesospehric temperature shows a persistent 35–50 min wave for all the durations of observations. In this paper, we discuss the observed variability in the mesospheric OH and O2 temperatures in connection with the passage of convective activity noted over South India along the west coast.

► Large variability in mesospheric OH and O2 temperatures is noted.
► Gravity waves of 35–50 min periodicity are found to be dominant.
► Results reveal thermal response of mesosphere to the tropical cyclone, Bijli.
► First data from India to report effects of tropical cyclone on the mesosphere.