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On the role of atomic oxygen in the dynamics and energy budget of the mesosphere and lower thermosphere
Author(s) -
Ward William E.,
Fomichev Victor I.
Publication year - 1993
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/93gl00842
Subject(s) - thermosphere , oxygen , mesosphere , energy budget , diffusion , mixing (physics) , radiative transfer , atmospheric sciences , convection , radiative cooling , atomic oxygen , atomic physics , atmosphere (unit) , slowdown , chemical physics , thermodynamics , physics , geophysics , ionosphere , stratosphere , optics , quantum mechanics , law , political science
Atomic oxygen affects both the heating and cooling of the mesosphere and lower thermosphere through its recombination and collisional deactivation of CO 2 . Recent increases in the accepted value of the deactivation constant, k o in CO 2 ‐O collisions enhance the role of the latter process in the dynamics and energy budget of this region. There are strong increases in the radiative cooling due to CO 2 in the 90–120 km region. The sensitivity of the cooling rate in the 15 μm band to variations in atomic oxygen concentration, [O], is enhanced so that the atmosphere in this region is unstable to these variations in concentration. Convection appears possible thereby providing a vertical mixing mechanism which is ineffective in the diffusion of heat but is effective in mixing constituents, and some justification for the use of different eddy diffusivities for heat and constituents. Heating rate calculations are intrinsically more complicated because both the heating and the cooling processes involving atomic oxygen are nonlinear functions of its concentration. The damping of atmospheric waves will be affected because radiative damping will be stronger up to 100 km and the cooling rate dependence on the atomic oxygen mixing ratio affords a new mechanism for photochemical damping. It appears that the overall dynamics and energy budget of this region must be reconsidered.