MedCLIVAR: Mediterranean Climate Variability- Temperature data homogenization and its impact on heatwave changes in the Eastern Mediterranean

Extreme temperature events such as the 2003 European summer heat wave have a strong impact on the environment, society and economy (1,2). In order to perform reliable and detailed analysis of extreme temperature events it is important to use long daily, high quality and homogenized temperature series (3). The Mediterranean region is considered as a „Hot Spot “ of climate change which will suffer from even more severe and frequent heat waves in the future (4). However, most climate studies are based on non-homogenized data that are not necessarily appropriate for cli-mate analysis and could also lead to inaccurate or even wrong results. To address this problem we (i) developed and applied a new homogenization technique to daily temperature series in the eas-tern Mediterranean, (ii) proposed a new heat wave definition and (iii) estimated changes in heat waves number, length and intensity. Three independent break detection methods (5-7) to detect an unknown number of break points (BPs) are used in combination with a non linear model (8) to correct daily summer (JJAS) maximum (TX) and mini-mum temperature (TN) series of 246 stations across the eastern Mediterranean covering the period 1960-2006. Advantages of this method are (i) no metadata is needed for break detection (Fig. 2) and (ii) a correc