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| Titel |
Potential evaporation estimation through an unstressed surface-energy balance and its sensitivity to climate change |
| VerfasserIn |
A. Barella-Ortiz, J. Polcher, A. Tuzet, K. Laval |
| 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. 11 ; Nr. 17, no. 11 (2013-11-22), S.4625-4639 |
| Datensatznummer |
250086002
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| Publikation (Nr.) |
 copernicus.org/hess-17-4625-2013.pdf |
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| Zusammenfassung |
Potential evaporation (ETP) is a basic input for many
hydrological and agronomic models, as well as a key variable in most actual
evaporation estimations. It has been approached through several diffusive and
energy balance methods, out of which the Penman–Monteith equation is
recommended as the standard one. In order to deal with the diffusive
approach, ETP must be estimated at a sub-diurnal frequency, as
currently done in land surface models (LSMs). This study presents an improved
method, developed in the ORCHIDEE LSM, which consists of estimating
ETP through an unstressed surface-energy balance (USEB method).
The results confirm the quality of the estimation which is currently
implemented in the model (Milly, 1992). The ETP underlying the
reference evaporation proposed by the Food and Agriculture Organization, FAO,
(computed at a daily time step) has also been analysed and compared.
First, a comparison for a reference period under current climate conditions
shows that USEB and FAO's ETP estimations differ, especially in
arid areas. However, they produce similar values when the FAO's assumption of
neutral stability conditions is relaxed, by replacing FAO's aerodynamic
resistance by that of the model's. Furthermore, if the vapour pressure
deficit (VPD) estimated for the FAO's equation, is substituted by ORCHIDEE's
VPD or its humidity gradient, the agreement between the daily mean estimates
of ETP is further improved.
In a second step, ETP's sensitivity to climate change is
assessed by comparing trends in these formulations for the 21st century. It
is found that the USEB method shows a higher sensitivity than the FAO's. Both
VPD and the model's humidity gradient, as well as the aerodynamic resistance
have been identified as key parameters in governing ETP trends.
Finally, the sensitivity study is extended to two empirical approximations
based on net radiation and mass transfer (Priestley–Taylor and Rohwer,
respectively). The sensitivity of these ETP estimates is
compared to the one provided by USEB to test if simplified equations are able
to reproduce the impact of climate change on ETP. |
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