Impact of spatiotemporal land use and land cover changes on surface urban heat islands in a semiarid environment

This study presents the results of research that was conducted in the city of Tehran, located in the subtropics (35 degrees N.) in a semi-desert climate in southwest Asia. The purpose was to analyze the relationship between land use/cover change (LULC) and the spatiotemporal dynamics of surface urban heat islands (SUHIs) and give results regarding the structure of the UHI in the city of Tehran. Using Landsat-5 TM data from 1986 to 2010, we quantified the spatiotemporal variability of the SUHI and LULC in the city of Tehran. The spatial distribution of land surface temperature (LST) showed the most extensive SUHI as spatially located in the western and southwestern areas of Tehran in 1986. In 2010, the spatial extent of SUHI had increased. The occurrence of LULC changes in the southern, southwestern, and especially the western parts of Tehran have played the most important role in expanding and intensifying the SUHI effect. These areas experienced two major alterations: (a) The area lost about 14 km(2) from green cover; and (b) the industrial and commercial land use, and transportation network extended significantly in these areas. Based on LULC and LST distribution patterns, barren lands, industrial and commercial land use, and transportation network have the major roles in the formation and expansion of the SUHI effect in Tehran. The SUHI of Tehran, like that of other arid or semi-arid cities, does not exhibit the classical pattern of SUHI: that is, the hot spots usually are not found in the downtown, as occurs in humid climates. Rather, the SUHI tends to situate over desert areas or barren lands that surround these cities. Therefore, an inversion of the standard SUHI phenomenon during daytime has been observed in Tehran. Research conducted in arid and semi-arid cities suggests that we should refine our point of view on the concept of the UHI in such cities and consider this issue in future studies.