Climate Change Impact Assessment on Outdoor Thermal Comfort Changes Using Physiological Equivalent Temperature (PET) Index in Mashhad

Introduction and Background: In recent decades, increasing earth heat lead to the death of thosands of people in the world. This situation cause urban planning meet a major climate change challenges which needs to mitigate its effects. Increasing in population and various related activities in different fields has led to problems such as wave heat throughout the world. In addition, changing the pattern of these changes and their unpredictability has increased in cities, thus concern about reducing and adapting to these hazards in different dimensions lead to pay more attention to urban life and promoting human health. The aim of this paper is to investigate effect of climate change which is caused by heat wave on outdoor thermal comfort in Mashhad city. Data collection method was based on library studies and also data gathered from meteorological station of Mashhad in the period of 10 years (2017-2007). The analysis method was based on Rayman and Excell software in Mashhad and physiological equivalent temperature (PET) index was the most commonly used index for evaluating outdoor thermal comfort. Findings show that climate change and the effects of heat wave in Mashhad in July and August have affected the outdoor thermal comfort, which put human health at more risk in these months. Moreover, studies of outdoor thermal comfort changes in winter in this city shows that warming of these seasons experienced a rapid pace, so that over the past 10 years, outdoor thermal comfort has increased by +1.4°C in March, this number will each 1.1+ in summer and July. Studies show that the summer and spring seasons of Mashhad are entering to the thermal stress range, while its cold seasons are becoming warmer and entering to outdoor thermal comfort range.