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@ARTICLE{Zahn:51204,
author = {Zahn, A. and Franz, P. and Bechtel, C. and Röckmann, T.
and Grooß, J.-U.},
title = {{M}odelling the budget of middle atmospheric water vapour
isotopes},
journal = {Atmospheric chemistry and physics},
volume = {6},
issn = {1680-7316},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {PreJuSER-51204},
pages = {2073 - 2090},
year = {2006},
note = {Record converted from VDB: 12.11.2012},
abstract = {A one-dimensional chemistry model is applied to study the
stable hydrogen ( D) and stable oxygen isotope (O-17, O-18)
composition of water vapour in stratosphere and mesosphere.
In the troposphere, this isotope composition is determined
by "physical" fractionation effects, that are phase changes
( e. g. during cloud formation), diffusion processes ( e. g.
during evaporation from the ocean), and mixing of air
masses. Due to these processes water vapour entering the
stratosphere first shows isotope depletions in D/H relative
to ocean water, which are similar to 5 times of those in
O-18/O-16, and secondly is mass-dependently fractionated
(MDF), i.e. changes in the isotope ratio O-17/O-16 are
similar to 0.52 times of those of O-18/O-16. In contrast, in
the stratosphere and mesosphere "chemical" fractionation
mechanisms, that are the production of H2O due to the
oxidation of methane, re-cycling of H2O via the HOx family,
and isotope exchange reactions considerably enhance the
isotope ratios in the water vapour imported from the
troposphere. The model reasonably predicts overall
enhancements of the stable isotope ratios in H2O by up to
similar to $25\%$ for D/H, similar to $8.5\%$ for O-17/O-16,
and similar to $14\%$ for O-18/O-16 in the mesosphere
relative to the tropopause values. The O-17/O-16 and
O-18/O-16 ratios in H2O are shown to be a measure of the
relative fractions of HOx that receive the O atom either
from the reservoirs O-2 or O-3. Throughout the middle
atmosphere, MDF O-2 is the major donator of oxygen atoms
incorporated in OH and HO2 and thus in H2O. In the
stratosphere the known mass-independent fractionation (MIF)
signal in O-3 is in a first step transferred to the NOx
family and only in a second step to HOx and H2O. In contrast
to CO2, O(D-1) only plays a minor role in this MIF transfer.
The major uncertainty in our calculation arises from poorly
quantified isotope exchange reaction rate coefficients and
kinetic isotope fractionation factors.},
keywords = {J (WoSType)},
cin = {ICG-I},
ddc = {550},
cid = {I:(DE-Juel1)VDB47},
pnm = {Atmosphäre und Klima},
pid = {G:(DE-Juel1)FUEK406},
shelfmark = {Meteorology $\&$ Atmospheric Sciences},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000238397900003},
url = {https://juser.fz-juelich.de/record/51204},
}