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Validation of RCM simulations using a conceptual runoff model
Claudia Teutschbein, Jan Seibert
Department of Physical Geography and Quaternary Geology, Stockholm University, 106 91 Stockholm, Sweden,
claudia.teutschbein@natgeo.su.se
1. Introduction
Hydrological modeling for climate change impact
assessment implies simulations using temperature and
precipitation series generated by climate models, e.g.
regional climate models (RCMs). The ability to correctly
reproduce current conditions provides confidence in the
simulation of future scenarios. While simulated temperature
and precipitation series can be compared directly to
observations, we were in this study also interested in the
combined effect on runoff simulations. In this study we,
therefore, investigated how well current conditions were
reproduced for both temperature, precipitation and runoff for
5 Swedish catchments.
A comparison of RCM control-run data with observations
was performed for precipitation and temperature. Moreover,
the runoff simulated with these time series has been
compared with measured values. Reanalysis data was also
included in the investigation for comparison.
2. Methods
The analysis has been performed for 5 Swedish catchments
with areas of 150 to 300 km 2 . These catchments, namely
Ostträsket (OST), Tännån (TAN), Fyrisån (FYR), Emån
(EMA) and Rönne Å (RON), represent different typical
climatic conditions and land-use types in Sweden (Fig. 1).
RCM precipitation and temperature data from 16 different
RCMs – all driven by ERA40 reanalysis data - were
obtained from the ENSEMBLES EU project.
After comparing the results of each RCM with observed data
in terms of accuracy and frequency of extreme events (Fig.
2), spatial and temporal differences were analyzed as well.
For comparison, reanalysis data (ERA-MESAN, ERA-
INTERIM) were also included.
In a second step, the best performing RCMs were picked for
further hydrological investigations. The runoff in the study
catchments was simulated with the conceptual runoff model
HBV, forced by the RCM data as well as reanalysis time
series. This approach is advantageous because hydrological
effects of inaccuracies of simulated precipitation and
temperature from the RCMs can be assessed. Furthermore,
the catchment runoff integrates over a larger area which
corresponds better to the RCM grid data than meteorological
point measurements.
Figure 1. Catchment areas in Sweden.
Figure 2. Ability of several RCMs to simulate
monthly climate parameters for Ostträsket. (a) max
precipitation, (b) max temperature, (c) sum
precipitation, (d) min temperature.