Trends in extreme daily temperature using climate change indices in Iran

Global temperature has increased about 0. 74°C over the last century (IPCC، 2007، 30). In recent studies، the potential of increase in heat waves، heavy precipitation، cold winter، summer storms and drought event due to climate change noticed (Zhang،2005،11). On the other hand، it is believed that climate change will affect most aspects of weather and climate، especially precipitation and temperature extreme events (Radinovi and Curi، 2009، 200; Lehner et al.، 2006، 293). Therefore، the socio-economic effects of extremes (Ryoo et al.، 2004، 145)، require more attention to such studies. Assessment of the temperature extremes changes is done in many region of the world in the last century (Mudelsee et al. 2003; New et al. 2001; Moberg and Jones 2005; Klein Tank and K¨onnen 2003; Alexander et al. 2006). The socio - economic effects of extremes in arid and semi arid regions like Iran due to very vulnerable and fragile climates are more and their sudden changes may be followed by the devastating events. Spatial and temporal variability of climate in Iran is one of its inherent characteristics and devastative socio-economic effects of climatic disasters such as floods and droughts have been high in recent years (Nazemosadat and Cordery 2000، 59; Barlow et al. 2002، 697; Nazemosadat and Ghasemi 2004، 4016). Studies such as Rasouli (2004)، about spatial analysis of cold winds in the Southwestern of Iran and Kaviani and his colleagues (2004)، the effective temperatures in the country، show the variability and instability of climate in Iran. Consequences of global warming in Iran include increased frequency of extreme events، especially in cold and heat waves، long time severe droughts and torrential rain (Rahimzadeh et al. 2009، 342). Numerous studies in recent years، has been investigated the average temperature and precipitation variability in Iran (Alijani 1997; Jahadi Toroghi 2000; Rasooli 2002; Rahimzadeh and Asgari 2003; Rahimzadeh and Asgari 2005; Pedram et al. 2005; Asadi and Heydari 2011). Furthermore، Rahimzadeh and her colleagues (2009) were considered the temperature and precipitation extreme variability in Iran and Taghavi، and Mohammadi (2007)، stated that the frequency of warm and cold events، respectively، has been associated with decreases and increases. Moreover، kari (2010)، has confirmed significant changes in heat waves and cold periods in Tehran. The purpose of this study provides a more detailed analysis about the spatial and temporal distribution of the temperature extremes in Iran.