Title: Evaluation of surface urban heat island intensity in arid environments (case study: Isfahan metropolitan area)
Abstract: Abstract Heat island is formed due to the expansion of a city in a vast geographic area. The traditional index is used to describe the urban heat island based on the temperature difference between the urban and rural areas. Other indices have been suggested in the literature for this purpose. However, the heat island characteristics depend on the background climate of the place where the city is located. Therefore, an index was defined based on the background climate of the Isfahan metropolitan area in order to quantify the heat island intensity. This new index is based on the representative pixels of the urban and the non-urban areas. For this purpose, the MODIS land cover type product (MCD12Q1) data was used to distinguish between the urban and non-urban areas. Also, the data from the MODIS/Terra/Aqua land surface temperature product (MOD11A1/MYD11A1) from 2000 to 2016 was utilized for the day time and night time to study the heat island intensity. Then, the representative pixels of urban and the non-urban areas were identified using the spatial correlation method and the heat island index was calculated for the metropolitan area of Isfahan. The study showed that the frequency distribution for the nighttime heat island index in the metropolitan area of Isfahan follows a normal distribution and is often 3.5-4 K above the temperature of the surrounding areas at night. Investigating the temporal and spatial behavior of surface urban heat island in the metropolitan area of Isfahan showed that the intensity of the surface urban heat island is maximum in January and becomes weaker in summer. The 365-day floating mean of the surface urban heat island showed that this index has increased in recent years. The core of heat island in the metropolitan area of Isfahan is extended to downtown areas where the oldest part of the city is located.