Abstract

The Urban Heat Island (UHI) effect, the characteristic warmth of a settlement compared with its surroundings, is the best-known climatic response to disruptions caused by urban development. Istanbul has experienced a highspeed urban growth in the last century. While the population of the city was under one million in 1900, it reached to 14 million in 2015. Almost 14 times growth in one century has made Istanbul the largest city in Turkey. High-speed urbanization and transformation of the natural environment and forests into built-up area has a critical impact on the metropolitan’s climate. Due to the alteration of heat energy balance and as a megacity, Istanbul has been affected by increasing severe heat waves in summer. This study focuses on two of the effective urban design factors upon the urban heat islands (UHIs) in Istanbul such as vegetation cover and characteristic of surface materials. The spatial pattern of land surface temperature (LST), surface albedo, the normalized difference vegetation index (NDVI) and land cover-land use (LCLU) are analyzed to explore the cooling or heating impacts of the green areas and the build-up areas on the UHI. The methodology is based on using Landsat 8 OLI (Operational Land Imager) satellite image that captured on 6 September 2015, and available meteorological data include two stations, one in city center (Kandilli Station) and the other one in rural area (Sile Station) that revealed average annual temperature differences 8.3°C in the last decade. The results of the analysis show that artificial surfaces with low albedo and low vegetation cover have the most positive exponential relationship with land surface temperature (LST) and increasing effect on UHI formation. The results of the analysis highlight that high albedo material (HAM), greenery on the surface and on the roofs (VEG), and a combination of them can be used as the UHI mitigation strategies.

Keywords: Urban Heat Island (UHI); Albedo; Land Surface Temperature; Land Use and Land Cover; Mitigation