Atmospheric Chemistry and Physics Discussions
www.atmos-chem-phys-discuss.net
1680-7367
1680-7375
4
1
2004
10.5194/acpd-4-833-2004
http://www.atmos-chem-phys-discuss.net/4/833/2004/
http://www.atmos-chem-phys-discuss.net/4/833/2004/acpd-4-833-2004.html
http://www.atmos-chem-phys-discuss.net/4/833/2004/acpd-4-833-2004.pdf
833
848
2004-02-05
The impact of anthropogenic chlorine, stratospheric ozone change and chemical feedbacks on stratospheric water
T. Röckmann
t.roeckmann@mpi-hd.mpg.de
J.-U. Grooß
R. Müller
Max-Planck-Institut für Kernphysik, Bereich Atmosphärenphysik, 69117 Heidelberg, Germany
Institut für Chemie und Dynamik der Geosphäre, Forschungszentrum Jülich, 52425 Jülich, Germany
Mixing ratios of water (H<sub>2</sub>O) in the stratosphere appear to increase due
to increased input of H<sub>2</sub>O
and methane (CH<sub>4</sub>) from the troposphere and due to intensified oxidation of
CH<sub>4</sub> in the stratosphere, but the underlying mechanisms are not yet understood. Here we identify and quantify
three chemical mechanisms which must have led to more efficient oxidation of
CH<sub>4</sub> over the past several decades: 1) The increase in stratospheric
chlorine levels due to anthropogenic CFC emissions, 2) the thinning of the
stratospheric ozone column and 3) enhanced OH levels in the stratosphere due
to increasing H<sub>2</sub>O
levels themselves. In combination with the increase in tropospheric CH<sub>4</sub>
mixing ratios and with solar cycle related variations of upper stratospheric ozone, these effects can explain about
50% of the additional conversion of CH<sub>4</sub> to H<sub>2</sub>O
as observed throughout the stratosphere. The relative contributions from the individual
processes have varied over the past decades.