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| Titel |
Seasonal, synoptic and diurnal variation of atmospheric water-isotopologues in the boundary layer of Southwestern Germany caused by plant transpiration, cold-front passages and dewfall. |
| VerfasserIn |
Emanuel Christner, Christoph Dyroff, Martin Kohler, Andreas Zahn, Yenny Gonzales, Matthias Schneider |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250082571
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| Zusammenfassung |
| Atmospheric water is an enormously crucial trace gas. It is responsible for ~70 % of the
natural greenhouse effect (Schmidt et al., JGR, 2010) and carries huge amounts of latent heat.
The isotopic composition of water vapor is an elegant tracer for a better understanding and
quantification of the extremely complex and variable hydrological cycle in Earth’s
atmosphere (evaporation, cloud condensation, rainout, re-evaporation, snow), which in turn is
a prerequisite to improve climate modeling and predictions. As H216O, H218O and HDO
differ in vapor pressure and mass, isotope fractionation occurs due to condensation,
evaporation and diffusion processes. In contrast to that, plants are able to transpire water with
almost no isotope fractionation. For that reason the ratio of isotopologue concentrations in
the boundary layer (BL) provides, compared to humidity measurements alone,
independent and additional constraints for quantifying the strength of evaporation and
transpiration. Furthermore the isotope ratios contain information about transport
history of an air mass and microphysical processes, that is not accessible by humidity
measurements.
Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for
investigating the Cycle of Atmospheric water) a commercial Picarro Analyzer L2120-i is
operated at Karlsruhe in Southwestern Germany, which is continuously measuring the
isotopologues H216O, HDO and H218O of atmospheric water vapor since January
2012.
A one year record of H216O, HDO and H218O shows clear seasonal, synoptic and
diurnal characteristics and reveals the main driving processes affecting the isotopic
composition of water vapor in the Middle European BL. Changes in continental
plant transpiration and evaporation throughout the year lead to a slow seasonal
HDO/H216O-variation, that cannot be explained by pure Rayleigh condensation.
Furthermore, cold-front passages from NW lead to fast and pronounced depletion of the
HDO/H216O-ratio within minutes. Superimposed to these variations are local diurnal
processes like dewfall, which cause a diurnal pattern captured by the deuterium excess. |
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