ORIGINAL PAPER Human-biometeorological assessment of heat waves in Athens Andreas Matzarakis & Panagiotis T. Nastos Received: 19 April 2010 / Accepted: 1 December 2010 / Published online: 15 December 2010 # Springer-Verlag 2010 Abstract The goal of this study is the analysis of heat waves and their impact on humans, using human biomete- orological indices, which are based on the energy balance of the human body. The implications for humans are not only described through the intensity of the heat waves, but also through their duration over consecutive days. Both intensity and duration were analyzed for the Greater Athens Area during the period 1955 to 2001. The analysis was carried out using the daily physiologically equivalent temperature and the daily minimum air temperature. Based on these two parameters, the results showed an increase in the average duration of heat waves. Furthermore, the use of the Gaussian filter revealed the intra-annual variation of heat stress conditions and their relevance to humans. The results could be used for the management of the negative consequences of heat waves in cities suffering from environmental pollution and also for climate impact studies. 1 Introduction Heat waves, a phenomenon that is not only of interest for the scientific community, occur regularly in Greece and also in the Mediterranean and Western Europe (i.e., Baldi et al. 2006; Conte ad Colacino 1995; Thirion et al. 2005). In the last three decades, the study of heat waves in Greece using different methods of analysis has been very popular. Synoptical, climatological, and human-biometeorological methods were applied (Giles et al. 1990; Giles and Balafoutis 1990; Matzarakis and Mayer 1991; Prezerakos, 1989; Brikas et al. 2006; Fouillet et al. 2006; Katsouyanni et al. 1988; Nastos and Matzarakis 2008, Philandras et al. 2008; Founda and Giannakopoulos 2009). However, the question on how a heat wave could be defined and what meteorological parameters or information on the impacts should be used to quantify them has not yet been addressed (Thirion et al. 2005; Fouillet et al. 2006; Koppe et al. 2004). Thus far the World Meteorological Organization has not put forward a universally agreed upon definition of heat waves (Koppe et al. 2004). Heat wave is commonly defined as a period of abnormally and uncomfortably hot weather with high air humidity. Typically, a heat wave lasts for at least 2 days (Koppe et al. 2004). Robinson (2001) describes a heat wave as an extended period of uncommonly high atmosphere-related heat stress, which causes temporary modifications in lifestyle habits and adverse health-related problems affecting communities. Thus, although a heat wave is a meteorological event, it cannot be assessed without reference to its impacts on humans. An analysis of weather elements should always include the assessment of the human sensation of heat. Appropriate thresholds must be established for this com- bined analysis, considering both daytime high and over- night low air temperature values. The thresholds should also relate to the normal climatic variability of the area, as well as the duration of the heat wave and its consequences on humans. A variety of heat stress indices that relate atmospheric conditions to human heat sensations have already been developed (Fanger 1972; Koppe et al. 2004). Driscoll A. Matzarakis Meteorological Institute, Albert-Ludwigs-University of Freiburg, Freiburg, Germany P. T. Nastos (*) Laboratory of Climatology and Atmospheric Environment, Faculty of Geology and Geoenvironment, University of Athens, Panepistimiopolis, GR 157 84, Athens, Greece e-mail: nastos@geol.uoa.gr Theor Appl Climatol (2011) 105:99–106 DOI 10.1007/s00704-010-0379-3