ABSTRACT

“Mesopause” is the altitude of absolute temperature minimum in the MLT (Mesosphere and Lower Thermosphere) region of terrestrial atmosphere. In the present study, the long term (2002-2012) data of monthly averaged zonal mean temperature and ozone volume mixing ratio (O3 vmr) obtained from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite are used to investigate the influence of solar cycle (during 23-24 solar cycles) and chemistry on tropical (10°N-15°N) mesopause variabilities. It is evident that the mesopause temperature and O3 vmr are positively correlated with 11 year solar cycle (F10.7 solar radio flux) due to the corresponding changes in CO2 and O. It is found that the tropical mesopause temperature is higher in September (~190 K), slightly lower in May and July (~185 K), and lowest (~175–178 K) in other months during 2002-2012. Also the mesopause height is varying between ~95 km (November-April) and ~99-100 km (May-October). The mesopause ozone is larger (~10-12 ppmv) during equinoxes and smaller (~4 ppmv) during solstices for all these years. Further it is clearly evident that the CO2 causes cooling (the only cooling mechanism) and O3 causes heating at 15 μm infrared emission (IR) in the mesopause region. In addition, the net heating rates due to (i) solar heating by O2 and O3, (ii) chemical heating due to seven major exothermic reactions, (iii) O3 long wave (IR) radiative heating and (iv) CO2 cooling rates are being used in the present study.