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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2017-602
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
03 Nov 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).
Impacts of climate change on extreme floods in Finland – studies using bias corrected Regional Climate Model data
Noora Veijalainen1, Juho Jakkila1, Taru Olsson2, Leif Backman2, Bertel Vehviläinen1, and Jussi Kaurola2 1Freshwater Centre, Finnish Environment Institute, Mechelininkatu 34a, P.O. Box 140, FI-00251, Helsinki, Finland
2Finnish Meteorological Institute, Erik Palménin aukio 1, P.O. Box 503, FI-00101, Helsinki, Finland
Abstract. Bias correction of precipitation and temperature of five Regional Climate Models (RCMs) was carried out using Distribution Based Scaling (DBS) method with two versions for precipitation adjustment: single gamma and double gamma. This data were then used as input for a hydrological model to simulate changes in floods by the end of this century, and the results were compared to corresponding changes simulated using delta change approach. The results show that while the DBS adjustment significantly improves the RCM precipitations and temperatures compared to observations, especially the double gamma distribution does not always preserve trends of the uncorrected RCM data. The simulation of floods in the control period is improved by the DBS adjustment with no significant differences between single and double gamma. However, some scenarios are still unable to match the observed hydrology adequately due to remaining biases especially in near zero winter temperatures. These scenarios may produce an unrealistic climate change signal and should therefore be discarded from further use. A simple criterion for evaluating the adequate performance of the RCMs and hydrological models compared to observed floods is presented. The results of climate change simulations show that extreme summer precipitations increase more than average values in Finland. The changes in floods by 2070–2099 vary in different regions depending on season and the main flood producing mechanism (snowmelt or heavy rain). The changes in floods simulated with the DBS adjusted RCM data are mostly similar as with delta change approach, but the DBS method produces larger range of changes.

Citation: Veijalainen, N., Jakkila, J., Olsson, T., Backman, L., Vehviläinen, B., and Kaurola, J.: Impacts of climate change on extreme floods in Finland – studies using bias corrected Regional Climate Model data, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2017-602, in review, 2017.
Noora Veijalainen et al.
Noora Veijalainen et al.
Noora Veijalainen et al.

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Short summary
Climate change impacts on floods in Finland were estimated on several locations. Regional climate model data was bias corrected and then used as input of a hydrological model and the function of the bias correction was evaluated. The bias correction improved the simulation of floods, but some scenarios are still unable to match the observed hydrology adequately. The changes in floods by 2070–2099 vary in different regions in Finland depending on season and the main flood producing mechanism.
Climate change impacts on floods in Finland were estimated on several locations. Regional...
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