Detection of urban heat islands from landsat imageries: A case study of West Mediterranean Region

The world has entered into a rapid urbanization process in the past 60 years. In 1950, more than 70% of the world population lived in rural areas and less than 30% in urban areas. This ratio shifted in favor of the urban and population living in urban areas was more than the rural in 2007. Technological developments have accelerated with the rapid increase in world population and urbanization. This situation negatively affects the global climate. The global average surface temperature has increased continuously since the 19th century. Urbanization and climate change on a global scale affects the urban climate and this leads to warmer urban areas than surrounding rural areas. This change in the urban climate has negatively affects the human population living in urban areas in many aspects. Therefore, studies of urban climate have become more important nowadays. Population has been increasing rapidly in Turkey too. The West Mediterranean Region (TR61) constitutes approximately 4% of Turkey's surface area and the urban population increases rapidly. Antalya, which is located in this region, is the Turkey's 5th largest city and it has the highest population growth rate in 2015. Antalya province is one of the most famous tourism cities of Turkey and a large number of tourists visit this city every year. Besides, greenhouse and agriculture activities are the other mainstay of the Antalya providing fruits and vegetables to other regions of Turkey. In addition, Antalya has a Mediterranean climate and the summers are very hot in this city. The increase in the air temperature that is already hot due to the Urban Heat Island (UHI) effect is not desirable. Therefore, it is important to investigate the UHI effect that has impact on the city. Isparta and Burdurthat are developing cities are also located in the same region and they have similar and different climatic and terrain features with Antalya. The analyzing of this area allows the comparison of the provinces that have different sizes and different characteristics and therefore these regions are selected as study areas. The objectives of this study are to examine land use/cover (LU/LC) classes, to analyze changes of Land Surface Temperatures (LST) and UHI effects and to determine the relationship between LST and LU/LC in the central districts of Antalya, Isparta and Burdur cities that are located in the West Mediterranean Region from 2001 to 2014. For this purpose, primarily LST values were calculated using thermal band of Landsat imagery. On the other hand, land use/cover classes are defined using Random Forest (RF) classification technique from Landsat imagery, NDVI, DMSP_OLS nighttime lights data and ASTER GDEM. Finally, LST and LU/LC classes are analyzed together and UHI effects are determined. In addition, analyzing the seasonal variation of the UHI effect is important in this region when the seasonal characteristics of the Mediterranean region and the population differences between the summer and winter were considered. For this purpose, urban and vegetation areas are identified using the DMSP_OLS nighttime lights data, emissivity image, and ASTER GDEM and UHI effects are investigated by using Landsat 8 OLI/TIRS satellite imagery that belongs to different seasons (December, March, June and October). The obtained results indicate that the LU/LC maps were generated successfully using RF classification technique, using additional bands during the classification had been shown to improve RF classification accuracy up to 11%. When the relationship between the LST values and LU/LC classes were observed, it can be stated that the lowest LST values are analyzed in water and vegetation areas, the highest LST values are observed in bare-land, urban, industry and dry agriculture areas. When the UHI effect between the years 2001 and 2014 is examined, it was detected that in Antalya the UHI effect was increased about1.2°C and it was most effective in summer and least effective in winter seasons. In the same period, the UHI effect decreased 0.6°C in Isparta and it was not changed in Burdur. According to seasonally examination, the UHI effect was most effective in summer season while it was negative in winter season in the selected study areas of Isparta and Burdur. This situation shows the positive impact of the vegetation areas on the urban climate clearly. Vegetation areas slow the growth temperature during the summer months and it helps prevent the severe temperature decline during the winter months. In general, when the relationship between the determined UHI effects and urban size were analyzed, it can be stated that the UHI effect increases with urban growth. The results obtained in this study can be used when planning the West Mediterranean Region development particularly the city of Antalya, which is one of the most rapidly urbanized cities of Turkey and this study, can make a contribution to generate most proper conditions for three urban areas.