Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 5.509 IF 5.509
  • IF 5-year value: 5.689 IF 5-year 5.689
  • CiteScore value: 5.44 CiteScore 5.44
  • SNIP value: 1.519 SNIP 1.519
  • SJR value: 3.032 SJR 3.032
  • IPP value: 5.37 IPP 5.37
  • h5-index value: 86 h5-index 86
  • Scimago H index value: 161 Scimago H index 161
Volume 10, issue 20
Atmos. Chem. Phys., 10, 9953-9964, 2010
https://doi.org/10.5194/acp-10-9953-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 10, 9953-9964, 2010
https://doi.org/10.5194/acp-10-9953-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  20 Oct 2010

20 Oct 2010

Do vibrationally excited OH molecules affect middle and upper atmospheric chemistry?

T. von Clarmann1, F. Hase1, B. Funke2, M. López-Puertas2, J. Orphal1, M. Sinnhuber1,3, G. P. Stiller1, and H. Winkler3 T. von Clarmann et al.
  • 1Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Karlsruhe, Germany
  • 2Instituto de Astrof{í}sica de Andaluc{í}a, CSIC, Granada, Spain
  • 3Bremen University, Institute of Environmental Physics, Bremen, Germany

Abstract. Except for a few reactions involving electronically excited molecular or atomic oxygen or nitrogen, atmospheric chemistry modelling usually assumes that the temperature dependence of reaction rates is characterized by Arrhenius' law involving kinetic temperatures. It is known, however, that in the upper atmosphere the vibrational temperatures may exceed the kinetic temperatures by several hundreds of Kelvins. This excess energy has an impact on the reaction rates. We have used upper atmospheric OH populations and reaction rate coefficients for OH(v=0...9)+O3 and OH(v=0...9)+O to estimate the effective (i.e. population weighted) reaction rates for various atmospheric conditions. We have found that the effective rate coefficient for OH(v=0...9)+O3 can be larger by a factor of up to 1470 than that involving OH in its vibrational ground state only. At altitudes where vibrationally excited states of OH are highly populated, the OH reaction is a minor sink of Ox and O3 compared to other reactions involving, e.g., atomic oxygen. Thus the impact of vibrationally excited OH on the ozone or Ox sink remains small. Among quiescent atmospheres under investigation, the largest while still small (less than 0.1%) effect was found for the polar winter upper stratosphere and mesosphere. The contribution of the reaction of vibrationally excited OH with ozone to the OH sink is largest in the upper polar winter stratosphere (up to 4%), while its effect on the HO2 source is larger in the lower thermosphere (up to 1.5% for polar winter and 2.5% for midlatitude night conditions). For OH(v=0...9)+O the effective rate coefficients are lower by up to 11% than those involving OH in its vibrational ground state. The effects on the odd oxygen sink are negative and can reach −3% (midlatitudinal nighttime lowermost thermosphere), i.e. neglecting vibrational excitation overestimates the odd oxygen sink. The OH sink is overestimated by up to 10%. After a solar proton event, when upper atmospheric OH can be enhanced by an order of magnitude, the excess relative odd oxygen sink by consideration of vibrational excitation in the reaction of OH(v=0...9)+O3 is estimated at up to 0.2%, and the OH sink by OH(v=0...9)+O can be reduced by 12% in the thermosphere by vibrational excitation.

Publications Copernicus
Download
Citation
Share