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Impact of molecular diffusion on the CO 2 distribution and the temperature in the mesosphere
Author(s) -
Chabrillat Simon,
Kockarts Gaston,
Fonteyn Dominique,
Brasseur Guy
Publication year - 2002
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 - 10.1029/2002gl015309
Subject(s) - mesopause , mesosphere , thermosphere , diffusion , atmospheric sciences , altitude (triangle) , eddy diffusion , environmental science , polar , range (aeronautics) , physics , meteorology , geophysics , ionosphere , materials science , stratosphere , astronomy , thermodynamics , turbulence , geometry , mathematics , composite material
Modelling the energy budget in the mesosphere and lower thermosphere requires a precise evaluation of CO 2 distribution in this region. This distribution is primarily determined by competition between vertical eddy diffusion and molecular diffusion. A simple algorithm is proposed to take into account both processes, at all altitudes. Using the SOCRATES bi‐dimensional model of the middle atmosphere, we show that molecular diffusion has a direct impact on CO 2 vertical distribution down to approximately 80 km altitude, i.e. well into the mesosphere and below the turbopause altitude. A sensitivity study with regard to different aeronomical processes shows that molecular diffusion has the deepest influence in the mesospheric polar night region. Our model shows that molecular diffusion of CO 2 is responsible for a polar night mesopause 12 K warmer than if this process was neglected. Hence, dynamical models should take this process in account across the whole mesospheric altitude range.