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| Titel |
Selecting the optimal method to calculate daily global reference potential evaporation from CFSR reanalysis data for application in a hydrological model study |
| VerfasserIn |
F. C. Sperna Weiland, C. Tisseuil, H. H. Dürr, M. Vrac, L. P. H. Beek |
| 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. 3 ; Nr. 16, no. 3 (2012-03-27), S.983-1000 |
| Datensatznummer |
250013223
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| Publikation (Nr.) |
 copernicus.org/hess-16-983-2012.pdf |
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| Zusammenfassung |
Potential evaporation (PET) is one of the main inputs of hydrological
models. Yet, there is limited consensus on which PET equation is most
applicable in hydrological climate impact assessments. In this study six
different methods to derive global scale reference PET daily time series
from Climate Forecast System Reanalysis (CFSR) data are compared:
Penman-Monteith, Priestley-Taylor and original and re-calibrated versions of
the Hargreaves and Blaney-Criddle method. The calculated PET time series are
(1) evaluated against global monthly Penman-Monteith PET time series
calculated from CRU data and (2) tested on their usability for modeling of
global discharge cycles.
A major finding is that for part of the investigated basins the selection of
a PET method may have only a minor influence on the resulting river flow.
Within the hydrological model used in this study the bias related to the PET
method tends to decrease while going from PET, AET and runoff to discharge
calculations. However, the performance of individual PET methods appears to
be spatially variable, which stresses the necessity to select the most
accurate and spatially stable PET method. The lowest root mean squared
differences and the least significant deviations (95% significance level)
between monthly CFSR derived PET time series and CRU derived PET were
obtained for a cell-specific re-calibrated Blaney-Criddle equation. However,
results show that this re-calibrated form is likely to be unstable under
changing climate conditions and less reliable for the calculation of daily
time series. Although often recommended, the Penman-Monteith equation
applied to the CFSR data did not outperform the other methods in a
evaluation against PET derived with the Penman-Monteith equation from CRU
data. In arid regions (e.g. Sahara, central Australia, US deserts), the
equation resulted in relatively low PET values and, consequently, led to
relatively high discharge values for dry basins (e.g. Orange, Murray and
Zambezi). Furthermore, the Penman-Monteith equation has a high data demand
and the equation is sensitive to input data inaccuracy. Therefore, we
recommend the re-calibrated form of the Hargreaves equation which globally
gave reference PET values comparable to CRU derived values for multiple
climate conditions.
The resulting gridded daily PET time series provide a new reference dataset
that can be used for future hydrological impact assessments in further
research, or more specifically, for the statistical downscaling of daily PET
derived from raw GCM data. The dataset can be downloaded from http://opendap.deltares.nl/thredds/dodsC/opendap/deltares/FEWS-IPCC. |
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