Large-basin hydrological response to climate model outputs: uncertainty caused by internal atmospheric variabilityстатья
Статья опубликована в высокорейтинговом журнале
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Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 20 июня 2016 г.
Аннотация: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