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| Titel |
Comparison of Eulerian and Lagrangian moisture source diagnostics – the flood event in eastern Europe in May 2010 |
| VerfasserIn |
A. Winschall, S. Pfahl, H. Sodemann, H. Wernli |
| 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 ; 14, no. 13 ; Nr. 14, no. 13 (2014-07-01), S.6605-6619 |
| Datensatznummer |
250118852
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| Publikation (Nr.) |
 copernicus.org/acp-14-6605-2014.pdf |
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| Zusammenfassung |
| Moisture convergence from different sources is an important
prerequisite for a heavy-precipitation event. The contributions from
different source regions can, however, hardly be quantified from
observations, and their assessment based on model results is
complex. Two conceptually different numerical methods are widely used
for the quantification of moisture sources: Lagrangian approaches
based on the analysis of humidity variations along backward
trajectories and Eulerian methods based on the implementation of
moisture tracers into a numerical model. In this study the moisture
sources for a high-impact, heavy-precipitation event that affected
eastern Europe in May 2010 are studied with both Eulerian and
Lagrangian moisture source diagnostics. The precipitation event was
connected to a cyclone that developed over northern Africa, moved over
the Mediterranean towards eastern Europe and induced transport of
moist air towards the Carpathian Mountains. Heavy precipitation and
major flooding occurred in Poland, the Czech Republic and Slovakia
between 16 and 18 May 2010. The Lagrangian and Eulerian diagnostics
consistently indicate a wide spatial and temporal range of moisture
sources contributing to the event. The source with the largest share is local
evapotranspiration from the European land surface, followed by
moisture from the North Atlantic. Further contributions come
from tropical western Africa (10–20° N) and the Mediterranean Sea.
Contrary to what could be expected, the Mediterranean contribution of
about 10% is relatively small. A detailed analysis of
exemplary trajectories corroborates the general consistency of the two
approaches, and underlines their complementarity. The Lagrangian
method allows for mapping out moisture source regions with
computational efficiency, whereas the more elaborate Eulerian model
requires predefined moisture sources, but includes also processes such
as precipitation, evaporation and turbulent mixing. However, in the
Eulerian model, uncertainty concerning the relative importance of
remote versus local moisture sources arises from different options to
parameterise moisture tagging at the surface. Ultimately a more
sophisticated parameterisation scheme will be required to reduce this
uncertainty. |
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