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A chemical perspective of day and night tropical (10°N–15°N) mesospheric inversion layers
Author(s) -
Ramesh K.,
Sridharan S.,
Raghunath K.,
Rao S. Vijaya Bhaskara
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023721
Subject(s) - daytime , solstice , atmospheric sciences , exothermic reaction , depth sounding , mixing ratio , inversion (geology) , mean kinetic temperature , thermosphere , kinetic energy , environmental science , meteorology , climatology , chemistry , ionosphere , geology , physics , astrophysics , geodesy , thermodynamics , geomorphology , oceanography , geophysics , latitude , structural basin , quantum mechanics
The various occurrence characteristics of day and night tropical (10°N–15°N, 60°E–90°E) mesospheric inversion layers (MILs) are studied by using TIMED Sounding of the Atmosphere using Broadband Emission Radiometry satellite data products of kinetic temperature; volume mixing ratios of O, H, and O 3 ; volume emission rates of O 2 ( 1 Δ) and OH (1.6 µm channel), and chemical heating rates due to seven dominant exothermic reactions among H, O, O 2 , O 3 , OH, HO 2 , and CO 2 cooling rates for the year 2011. Although both dynamics and chemistry play important roles, the present study mainly focuses on the chemical processes involved in the formation of day and night MILs. It is found that the upper level height of daytime (nighttime) MIL descends (ascends) from ~88 km (~80 km) in winter to ~72 km (~90 km) in summer. The day and night inversion amplitudes are correlated with total chemical heating rates and CO 2 cooling rates, and they show semi annual variation with larger (smaller) values during equinoxes (solstices). The daytime (nighttime) inversion layers are predominantly due to the exothermic reaction, R 5 : O + O + M → O 2 + M and R 6 : O + O 2 + M → O 3 + M (R 3 : H + O 3 → OH + O 2 ). In addition, the CO 2 causes large cooling at the top and small heating at the bottom levels of both day and night MILs. In the absence of dynamical effects, the chemical heating and CO 2 cooling jointly contribute for the occurrence of day and night MILs.