Characterizing joint effects of spatial extent, temperature magnitude and duration of heat waves and cold spells over Central Europe

Heat waves and cold spells have pronounced impacts on the natural environment and society. The main aim of this study is to identify major Central European heat waves and cold spells since 1950 and assess their severity not only from the viewpoint of temperature and duration but also as to the affected area. The heat waves and cold spells are delimited from the E-OBS gridded data set. An extremity index is proposed that captures joint effects of spatial extent, temperature and duration of heat waves and cold spells. During the 1950–2012 period, we identified 18 major heat waves and 24 major cold spells over Central Europe. The most severe heat wave occurred in summer 1994, followed by the 2006 heat wave; both these events were far more extreme over Central Europe than heat waves in the well-known 2003 and 2010 summers. The most severe cold spells occurred in the winters of 1955/56 and 1962/63. The recent winter of 2011/12 was found to be the 6th coldest since 1950/51 according to the seasonal sum of the extremity index. The heat waves and cold spells were classified through a hierarchical cluster analysis of their characteristics (temperature amplitude, spatial extent of the core, and duration) into 4 basic types. The established list of major Central European heat waves and cold spells might be utilized in further analyses, and the extremity index may be applied over different areas to perform comparative studies and used also for evaluation of regional climate model simulations.