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| Titel |
Large-basin hydrological response to climate model outputs: uncertainty caused by internal atmospheric variability |
| VerfasserIn |
A. Gelfan, V. A. Semenov, E. Gusev, Y. Motovilov, O. Nasonova, I. Krylenko, E. Kovalev |
| 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 ; 19, no. 6 ; Nr. 19, no. 6 (2015-06-15), S.2737-2754 |
| Datensatznummer |
250120739
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| Publikation (Nr.) |
 copernicus.org/hess-19-2737-2015.pdf |
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| Zusammenfassung |
| An approach is proposed to assess hydrological simulation uncertainty
originating from internal atmospheric variability. The latter is one of three
major factors contributing to uncertainty of simulated climate change
projections (along with so-called "forcing" and "climate model"
uncertainties). Importantly, the role of internal atmospheric variability is
most visible over spatio-temporal scales of water management in large river
basins. Internal atmospheric variability is represented by large ensemble
simulations (45 members) with the ECHAM5 atmospheric general circulation
model. Ensemble simulations are performed using identical prescribed lower
boundary conditions (observed sea surface temperature, SST, and sea ice
concentration, SIC, for 1979–2012) and constant external forcing parameters
but different initial conditions of the atmosphere. The ensemble of
bias-corrected ECHAM5 outputs and ensemble averaged ECHAM5 output are used as
a distributed input for the ECOMAG and SWAP hydrological models. The
corresponding ensembles of runoff hydrographs are calculated for two large
rivers of the Arctic basin: the Lena and Northern Dvina rivers. A number of
runoff statistics including the mean and the standard deviation of annual,
monthly and daily runoff, as well as annual runoff trend, are assessed.
Uncertainties of runoff statistics caused by internal atmospheric variability
are estimated. It is found that uncertainty of the mean and the standard
deviation of runoff has a significant seasonal dependence on the maximum
during the periods of spring–summer snowmelt and summer–autumn rainfall
floods. Noticeable nonlinearity of the hydrological models' results in the
ensemble ECHAM5 output is found most strongly expressed for the Northern
Dvina River basin. It is shown that the averaging over ensemble members
effectively filters the stochastic term related to internal atmospheric
variability. Simulated discharge trends are close to normally distributed
around the ensemble mean value, which fits well to empirical estimates and,
for the Lena River, indicates that a considerable portion of the observed
trend can be externally driven. |
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