Mean thermal structure of the low-latitude middle atmosphere studied using Gadanki Rayleigh lidar, Rocket, and SABER/TIMED observations

Abstract

The present study delineates the low-latitude thermal structure in the altitude range of 30 to 110 km using Gadanki (13.5°N, 79.2°E) Rayleigh lidar (1998-2007), Thumba (8.5°N,77°E) rocketsondes (1970-1991), and SABER/TIMED satellite (2002-2007) observations. This study particularly addresses whether (1) the lidar data available only during nighttime is sufficient to study the background mean thermal structure in 30-80 km altitude region, (2) the nonavailability of the lidar data during cloudy seasons (monsoon) will affect the derived background mean thermal structure, and (3) any alternate satellite observations can be used for getting the thermal structure of the middle atmosphere. The comparisons between temperatures measured by Rayleigh lidar and SABER show good agreement, suggesting that SABER data can be used effectively to study the mean thermal structure. The nocturnal average and diurnal average of temperature from SABER show similar features, suggesting that data available from lidar only during nighttime can be effectively used to study the mean background thermal structure between 30 and 80 km. Large difference between SABER and lidar observations during monsoon suggests that low data rate available from the lidar is not sufficient to obtain the mean thermal structure during cloudy seasons. Beside this, variations in stratopause (mesopause) height and temperature are also studied. The stratopause and mesopause lie in the height region of 47-49 km and 97-99 km, with peak temperature of 265 K and 170 K, respectively. Stratopause height and temperature show clear semiannual oscillation. No significant seasonal variation is observed either in mesopause height or in temperature at this low latitude.