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| Titel |
Optimising predictor domains for spatially coherent precipitation downscaling |
| VerfasserIn |
S. Radanovics, J.-P. Vidal, E. Sauquet, A. Ben Daoud, G. Bontron |
| 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 ; 17, no. 10 ; Nr. 17, no. 10 (2013-10-28), S.4189-4208 |
| Datensatznummer |
250085973
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| Publikation (Nr.) |
 copernicus.org/hess-17-4189-2013.pdf |
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| Zusammenfassung |
| Statistical downscaling is widely used to overcome the scale gap between
predictors from numerical weather prediction models or global circulation
models and predictands like local precipitation, required for example for
medium-term operational forecasts or climate change impact studies. The
predictors are considered over a given spatial domain which is rarely
optimised with respect to the target predictand location. In this study, an
extended version of the growing rectangular domain algorithm is proposed to
provide an ensemble of near-optimum predictor domains for a statistical
downscaling method. This algorithm is applied to find five-member ensembles
of near-optimum geopotential predictor domains for an analogue downscaling
method for 608 individual target zones covering France. Results first show
that very similar downscaling performances based on the continuous ranked
probability score (CRPS) can be achieved by different predictor domains for any
specific target zone, demonstrating the need for considering alternative
domains in this context of high equifinality. A second result is the large
diversity of optimised predictor domains over the country that questions the
commonly made hypothesis of a common predictor domain for large areas. The
domain centres are mainly distributed following the geographical location of
the target location, but there are apparent differences between the windward
and the lee side of mountain ridges. Moreover, domains for target zones
located in southeastern France are centred more east and south than the
ones for target locations on the same longitude. The size of the optimised
domains tends to be larger in the southeastern part of the country, while
domains with a very small meridional extent can be found in an east–west band
around 47° N. Sensitivity experiments finally show that results are
rather insensitive to the starting point of the optimisation algorithm except
for zones located in the transition area north of this east–west band.
Results also appear generally robust with respect to the archive length
considered for the analogue method, except for zones with high interannual
variability like in the Cévennes area. This study paves the way for
defining regions with homogeneous geopotential predictor domains for
precipitation downscaling over France, and therefore de facto ensuring the
spatial coherence required for hydrological applications. |
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