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| Titel |
Trend in ice moistening the stratosphere – constraints from isotope data of water and methane |
| VerfasserIn |
J. Notholt, G. C. Toon, S. Fueglistaler, P. O. Wennberg, F. W. Irion, M. McCarthy, M. Scharringhausen, T. Siek Rhee, A. Kleinböhl, V. Velazco |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 1 ; Nr. 10, no. 1 (2010-01-12), S.201-207 |
| Datensatznummer |
250007900
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| Publikation (Nr.) |
 copernicus.org/acp-10-201-2010.pdf |
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| Zusammenfassung |
| Water plays a major role in the chemistry and radiative budget of the
stratosphere. Air enters the stratosphere predominantly in the tropics,
where the very low temperatures around the tropopause constrain water vapour
mixing ratios to a few parts per million. Observations of stratospheric
water vapour show a large positive long-term trend, which can not be
explained by change in tropopause temperatures. Trends in the partitioning
between vapour and ice of water entering the stratosphere have been
suggested to resolve this conundrum. We present measurements of
stratospheric H2O, HDO, CH4 and CH3D in the period 1991–2007
to evaluate this hypothesis. Because of fractionation processes during phase
changes, the hydrogen isotopic composition of H2O is a sensitive
indicator of changes in the partitioning of vapour and ice. We find that the
seasonal variations of H2O are mirrored in the variation of the ratio
of HDO to H2O with a slope of the correlation consistent with water
entering the stratosphere mainly as vapour. The variability in the
fractionation over the entire observation period is well explained by
variations in H2O. The isotopic data allow concluding that the trend in
ice arising from particulate water is no more than (0.01±0.13)
ppmv/decade in the observation period. Our observations suggest that between
1991 and 2007 the contribution from changes in particulate water transported
through the tropopause plays only a minor role in altering in the amount of
water entering the stratosphere. |
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