Journal of Atmospheric and Solar–Terrestrial Physics 207 (2020) 105374 Available online 23 June 2020 1364-6826/© 2020 Elsevier Ltd. All rights reserved. Research Paper The effect of urbanization on the intensifcation of SUHIs: Analysis by LULC on Karachi Shahnillah Haider Rizvi a, * , Hira Fatima b , Muhammad Jawed Iqbal b , Khan Alam c a Department of Mathematics, University of Karachi, Karachi, 75270, Pakistan b Institute of Space Science and Technology, University of Karachi, Karachi, 75270, Pakistan c Department of Physics, University of Peshawar, Peshawar, 25120, Pakistan A R T I C L E INFO Keywords: Surface Urban Heat Island Impervious areas Land Surface Temperature Land Use Land Cover ABSTRACT This study aims to assess Urban Heat Island (UHI) as Surface Urban Heat Island (SUHI) of Karachi which ensures the existence of UHI effect on sustainability, based on the analysis of rapid urbanization and Land Use Land Cover (LULC) changes on the average temperature warming in Karachi. Satellite images are employed to extract statistics regarding land-use in Karachi city and to obtain land surface temperature (LST) maps for the year 2009 and 2017. LULC map is obtained by applying a supervised classifcation technique to detect the changes in impervious areas. Maps of daytime surface temperature are retrieved from the thermal band of Landsat images and nighttime LST is extracted from the MODIS. The Urban Heat Island Intensity (UHII) is analyzed to indicate persistent zones. It is found that built-up areas are increased by 40% and the vacant areas are decreased at a huge rate within study period of 8 years, whereas the intensity of UHI is increased by 0.04 � C . The LULC changes play vital role in the variation of surface temperature along with a spatial distribution pattern of UHI. Regression analysis is also carried out to examine the relationship of LST with impervious areas. 1. Introduction Urbanization is the most visible aspect of human impact on the earth’s system (DeFries, 2008). It is caused by the economic develop- ment and rapid growth of population (Deep and Saklani, 2014) and urban expansion is the rapid increase of geographic extent of urban areas by means of new developments on isolated regions that are far from other urban areas (Nechyba and Walsh, 2004). When urban lo- calities are built, abrupt changes are observed in the prevailing envi- ronment. The strong infuence of these changes is observed on energy balance of the existing environment which gives rise to the effect of Urban Heat Island (UHI). The effect of Surface Urban Heat Island (SUHI) is described as high surface temperature in cities rather than cooler surrounding areas (Oke, 1982; Clinton and Gong, 2013; Sobrino et al., 2013). Most of the urban localities, roads, buildings, and other in- frastructures are covered by concrete and asphalt paving material. These surfaces are waterproof with higher heat absorption capacities and have less albedo that absorbs more radiations as compared to the surrounding countryside (Chudnovsky et al., 2004). These types of changes in urban surfaces lead to the increase in air and surface temperature of built-up areas as compared to their surrounding areas. Most of the cities in the world are highly affected by climate change and the UHI effect. (Hoffmann et al., 2011; Radhi et al., 2013; Chun and Guldmann, 2014; Coseo and Larsen, 2014; Kourtidis et al., 2015; Tzavali et al., 2015). Temperature of urban localities can be raised up to 2–6 � C in the summer season and can be 13 � C higher in the winter season as compared to the temperature observed in surrounding rural areas (Alam and Rabbani, 2007). The phenomena of UHI is observed in over several Asian countries (Hung et al., 2006; Choi et al., 2014). Lee et al. (2019) performed a time series analysis to examine the seasonal UHII in eight megacities of Asia including Karachi over the period of 1992–2012. The results indicate that the variation of UHI pattern differs for each indi- vidual city and season. UHII is found to be increased as the size of the urban area increases. The intensity of the phenomenon is also affected by the population that causes an anthropogenic heat, though, as an in- dividual factor, its effect seemed to have insignifcant. Another study confrmed the changes in UHI effects w.r.t the urbanization rate and found a positive correlation among the population size and UHII during the seasonal time series analysis from 1961 to 2000 in China (Hua et al., 2008). Yin et al. (2007) also highlighted that the effect of UHI is increased by 0.072 � C in annual air temperature, during the years 1961–2005, whereas 0.047 � C is observed particularly during * Corresponding author. E-mail address: rshahnilla@hotmail.com (S.H. Rizvi). Contents lists available at ScienceDirect Journal of Atmospheric and Solar-Terrestrial Physics journal homepage: www.elsevier.com/locate/jastp https://doi.org/10.1016/j.jastp.2020.105374 Received 24 September 2019; Received in revised form 16 June 2020; Accepted 18 June 2020