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| Titel |
Evaluation of drought propagation in an ensemble mean of large-scale hydrological models |
| VerfasserIn |
A. F. Loon, M. H. J. Huijgevoort, H. A. J. Lanen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 16, no. 11 ; Nr. 16, no. 11 (2012-11-06), S.4057-4078 |
| Datensatznummer |
250013559
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| Publikation (Nr.) |
 copernicus.org/hess-16-4057-2012.pdf |
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| Zusammenfassung |
Hydrological drought is increasingly studied using large-scale
models. It is, however, not sure whether large-scale models
reproduce the development of hydrological drought correctly. The
pressing question is how well do large-scale models simulate the
propagation from meteorological to hydrological drought? To answer
this question, we evaluated the simulation of drought propagation in
an ensemble mean of ten large-scale models, both land-surface models
and global hydrological models, that participated in the model
intercomparison project of WATCH (WaterMIP). For a selection of case
study areas, we studied drought characteristics (number of droughts,
duration, severity), drought propagation features (pooling,
attenuation, lag, lengthening), and hydrological drought typology
(classical rainfall deficit drought, rain-to-snow-season
drought, wet-to-dry-season drought, cold snow season drought, warm
snow season drought, composite drought).
Drought characteristics simulated by large-scale models clearly
reflected drought propagation; i.e. drought events became fewer and
longer when moving through the hydrological cycle. However, more
differentiation was expected between fast and slowly responding
systems, with slowly responding systems having fewer and longer
droughts in runoff than fast responding systems. This was not found
using large-scale models. Drought propagation features were poorly
reproduced by the large-scale models, because runoff reacted
immediately to precipitation, in all case study areas. This fast
reaction to precipitation, even in cold climates in winter and in
semi-arid climates in summer, also greatly influenced the
hydrological drought typology as identified by the large-scale
models. In general, the large-scale models had the correct
representation of drought types, but the percentages of occurrence
had some important mismatches, e.g. an overestimation of
classical rainfall deficit droughts, and an underestimation
of wet-to-dry-season droughts and snow-related
droughts. Furthermore, almost no composite droughts were
simulated for slowly responding areas, while many multi-year drought
events were expected in these systems.
We conclude that most drought propagation processes are reasonably well
reproduced by the ensemble mean of large-scale models in contrasting
catchments in Europe. Challenges, however, remain in catchments
with cold and semi-arid climates and catchments with large storage
in aquifers or lakes. This leads to a high uncertainty in
hydrological drought simulation at large scales.
Improvement of drought simulation in
large-scale models should focus on a better representation of
hydrological processes that are important for drought development,
such as evapotranspiration, snow accumulation and melt, and
especially storage. Besides the more explicit inclusion of storage
in large-scale models, also parametrisation of
storage processes requires attention, for example through a global-scale
dataset on aquifer characteristics, improved large-scale datasets on other
land characteristics (e.g. soils, land cover), and calibration/evaluation of the
models against observations of storage (e.g. in snow, groundwater). |
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