Characterization and modeling of large-scale drought in Europe

There is currently considerable uncertainty as to how the global water cycle will respond to future environmental changes, particularly at the regional scale. This includes variability in the prediction of future climate between models and between different ensemble members of the same climate model (GCM). Superimposed on these uncertainties are the errors resulting from the use of GCM data (e.g. different bias correction and downscaling techniques) to force imperfect land-surface and hydrological models, and the inherently unknown future changes in climate, land cover and other human impacts. The most significant impacts are likely associated with changes in the water cycle, and there is a general agreement that climate will become more variable and hence extreme events, such as floods and droughts, will become more frequent. The EU-funded WATCH (WATer and global CHange) project (http://www.eu-watch.org) brings together the hydrology and climate community to provide a comprehensive assessment of the components of the current and future global water cycles, including hydrological extremes. The overall objective of the extremes work block is to advance our knowledge on the impact of global environmental change on the spatial and temporal scale of droughts and large-scale floods. Here, an overview of drought studies undertaken in WATCH is provided, with special focus on the characterisation and modelling of large-scale drought at the pan-European scale. This includes a comparison of RCM simulated and observed hydrological drought, where the results indicate that despite good overall agreement, some properties, in particular the persistence of hydrological drought, are not well reflected. The simulations are evaluated against a consolidated data set of about 450 streamflow records across Europe.