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Observational evidence for soil-moisture impact on hot extremes in southeastern Europe



Climate change is expected to affect not only the means of climatic variables, but also their variabilities1,2 and extremes such as heat waves2,3,4,5,6. In particular, modelling studies have postulated a possible impact of soil-moisture deficit and drought on hot extremes7,8,9,10,11. Such effects could be responsible for impending changes in the occurrence of heat waves in Europe7. Here we analyse observational indices based on measurements at 275 meteorological stations in central and southeastern Europe, and on publicly available gridded observations12. We find a relationship between soil-moisture deficit, as expressed by the standardized precipitation index13, and summer hot extremes in southeastern Europe. This relationship is stronger for the high end of the distribution of temperature extremes. We compare our results with simulations of current climate models and find that the models correctly represent the soil-moisture impacts on temperature extremes in southeastern Europe, but overestimate them in central Europe. Given the memory associated with soil moisture storage, our findings may help with climate-change-adaptation measures, such as early-warning and prediction tools for extreme heat waves.

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Figure 1: Station observations and analysis domains.
Figure 2: Hot extremes versus SPI.
Figure 3: Quantile regression analysis.


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We acknowledge the E-Obs dataset from the EU-FP6 project ENSEMBLES ( and the data providers in the ECA &D project ( Station observations for Austria were kindly provided by the Central Institute for Meteorology and Geodynamics (ZAMG). Moreover, we would like to thank the ENSEMBLES community for providing model data. This study was conducted in the framework of the European Commission FP6 STREP project CECILIA (contract GOCE 037005; We further acknowledge support from the Swiss National Science Foundation (NCCR Climate, NRP DROUGHT-CH), the EC FP7 Project CARBO-Extreme (FP7-ENV-2008-1-226701), and the CCES MAIOLICA project.

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Authors and Affiliations



M.H. and S.I.S. designed the study and wrote the manuscript. M.H. carried out the analyses. B.O. helped with the statistical analyses. F.B., M.H., P.S., O.B.C. and S.I.S. developed the CECILIA climate and extreme database and the software code for the index calculation. V.A., C.B., H.F. and P.S. provided the observational indices. F.B. helped with the computation of the indices for the ENSEMBLES models.

Corresponding authors

Correspondence to Martin Hirschi or Sonia I. Seneviratne.

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The authors declare no competing financial interests.

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Hirschi, M., Seneviratne, S., Alexandrov, V. et al. Observational evidence for soil-moisture impact on hot extremes in southeastern Europe. Nature Geosci 4, 17–21 (2011).

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