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Absorption and emission by carbon‐dioxide in the mesosphere
Author(s) -
Houghton J. T.
Publication year - 1969
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49709540302
Subject(s) - radiative transfer , carbon dioxide , absorption (acoustics) , mesosphere , excited state , relaxation (psychology) , thermodynamic equilibrium , radiative equilibrium , atomic physics , atmospheric sciences , atmosphere (unit) , vibrational energy relaxation , materials science , chemistry , physics , thermodynamics , stratosphere , optics , psychology , social psychology , organic chemistry
Theoretical and experimental evidence is presented which leads to a vibrational relaxation time appropriate for the v 2 vibration of CO 2 at 15 μ under atmospheric conditions at 210°K and standard pressure of 6·0 × 10 −6 sec. The effect of this on the atmospheric cooling rate near 90 km due to emission by CO 2 is discussed. It is shown that absorption of solar radiation by the v 3 band (at 4·3 μ) and the combination bands of CO 2 (at 2·7 μ) leads to a heating rate of about 2°C (12 hr) −1 near 80 km, this being one of the largest contributions to the radiative heating rate at this altitude. The processes by which relaxation from the v 3 vibration of CO 2 occurs involve vibrationally excited oxygen and the v 2 vibration of H 2 O. The magnitude of heating‐rate depends considerably, therefore, on the H 2 O concentration. For thermal radiative exchange by the v 3 band, thermodynamic equilibrium begins to break down at 30 km; its contribution to the radiative budget of the mesosphere is consequently very small.