Evaluating Urban Heat Islands Using the Urban Viability Index (Case Study: Karaj Metropolis)

As one of the most significant aspects of rapid growth without urban planning, reduction in vegetation is often replaced by unauthorized surfaces such as buildings and other impervious surfaces. Karaj metropolis is one of the significant urban areas located 20 km west of Tehran with such rapid growth. The present study evaluates the temporal-spatial variations of Land Surface Temperature (LST) and the Urban Liveability Index (ULI). It also seeks to examine the Urban Heat Islands (UHIs) using the data of the Landsat 5 Thematic Mapper (TM) and Landsat 8 Operational Land Imager (OLI) over 32 years (1987-2019). The Fractal Net Evolution Approach (FNEA) was employed to calculate UHIs, and the deductive Environmental Critical Condition (ECI) method based on LST and NDVI was used for probing the urban environmental situation. The results indicated that the average LST in Karaj metropolis is between 22 and 35 degrees C. Furthermore, in 1990, the standard deviation of the LST was increased so that more than seven degrees C was observed for LST. Analysis of temperature zones and their effective parameters such as construction, transportation, and road construction in Karaj metropolis shows a significant negative correlation between LST and NDVI and a positive one between LST and constructed urban areas.