Open AccessTotal hydrogen mixing ratio anomaly around the mesopause region
Author(s) -
Sonnemann G. R.,
Körner U.
Publication year - 2003
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2002jd003015
Subject(s) - mesopause , hydrogen , mixing (physics) , mixing ratio , diffusion , atmosphere (unit) , eddy diffusion , flux (metallurgy) , turbulence , atmospheric sciences , physics , mesosphere , chemistry , materials science , thermodynamics , stratosphere , organic chemistry , quantum mechanics
The strong turbulent mixing within the middle atmosphere should prevent a change of the value of the total hydrogen mixing ratio regardless of the transformation of the hydrogen species in one another within the homosphere. Within the heterosphere the corresponding mixing ratio should drastically increase due to the action of molecular diffusion. We show on the basis of a global three‐dimensional model of the dynamics and chemistry of the middle atmosphere that the total mixing ratio decreases under certain conditions when an (escape) flux flows through the domain. The effect occurs particularly above and around the mesopause region, reaching a distinct minimum at about 108 km height. Hunten and Strobel [1974] also found a small reduction on the basis of simplified model calculations, but they stated that the total mixing ratio of hydrogen atoms remains nearly the same. The cause of this apparently paradoxical behavior lies in the fact that under the condition of a hydrogen flux just in the domain of transition of predominant turbulent diffusion to predominant molecular diffusion, a strong decomposition of the heavier H 2 O component into the light hydrogen constituents takes place, and the temperature increases strongly with height above the mesopause. The marked reduction of the total hydrogen mixing ratio within the extended mesopause region is extremely important for all questions concerning the physics and chemistry of this domain.