Tempo-Spatial Behavior of Surface Urban Heat Island of Isfahan Metropolitan Area

The population of Isfahan City has been increased by ten times during the last six decades. This increase has had extensive environmental consequences. In this period, drying up of Zayandehrood River, increase in temperature and variability of precipitation has exacerbated the environmental conditions. Formation of the heat island is only one of the consequences of environmental changes in the last decades. The heat island also has many consequences in terms of health and water and energy consumptions. In this research, the land surface temperature (LST) data corresponding to daytime and nighttime using MODIS Aqua/LST from 2000 to 2016 are utilized. Using these data, the background climate of Isfahan metropolis was detected by the distance-azimuth diagram method. Then, the representative pixel within the city and the representative pixel of the background climate were identified. Based on time series of LST over these two pixels, SUHI index of Isfahan metropolis was calculated. Investigations showed that Isfahan metropolis area is colder than suburbs during the day but at night is about 2 K warmer than its surroundings. The intensity of the SUHI is maximal in January and turns weaker in summer. Regarding the temporal and spatial behavior of Isfahan metropolis SUHI, it seems that changes created by the urban concerning the moisture, albedo and composition of the atmosphere have a great role in the formation of the SUHI. Zayandehrood River has a major role in mitigation of temperature at the land surface, and its drying up has environmental consequences.