Abstract
Abstract. Along with urbanization, sealing of vegetated land and evaporation surfaces by impermeable materials, lead to changes in urban climate. This phenomenon is observed as temperatures several degrees higher in densely urbanized areas compared to the rural land at the urban fringe particularly at nights, so-called Urban Heat Island. Urban Heat Island (UHI) effect is related with urban form, pattern and building materials so far as it is associated with meteorological conditions, air pollution, excess heat from cooling. UHI effect has negative influences on human health, as well as other environmental problems such as higher energy demand, air pollution, and water shortage. Urban Heat Island (UHI) effect has long been studied by observations of air temperature from thermometers. However, with the advent and proliferation of remote sensing technology, synoptic coverage and better representations of spatial variation of surface temperature became possible. This has opened new avenues for the observation capabilities and research of UHIs. In this study, "UHI effect and its relation to factors that cause it" is explored for İzmit city which has been subject to excess urbanization and industrialization during the past decades. Spatial distribution and variation of UHI effect in İzmit is analysed using Landsat 8 and ASTER day & night images of 2015 summer. Surface temperature data derived from thermal bands of the images were analysed for UHI effect. Higher temperatures were classified into 4 grades of UHIs and mapped both for day and night. Inadequate urban form, pattern, density, high buildings and paved surfaces at the expanse of soil ground and vegetation cover are the main factors that cause microclimates giving rise to spatial variations in temperatures across cities. These factors quantified as land surface/cover parameters for the study include vegetation index (NDVI), imperviousness (NDISI), albedo, solar insolation, Sky View Factor (SVF), building envelope, distance to sea, and traffic space density. These parameters that cause variation in intra-city temperatures were evaluated for their relationship with different grades of UHIs. Zonal statistics of UHI classes and variations in average value of parameters were interpreted. The outcomes that highlight local temperature peaks are proposed to the attention of the decision makers for mitigation of Urban Heat Island effect in the city at local and neighbourhood scale.
Highlights
Urban growth and sprawl have drastically altered the biophysical environment with the most evident change occurring as the replacement of soil and vegetation cover with impervious urban materials, such as concrete, asphalt, and building materials, which affect the albedo, evapotranspiration and runoff characteristics of the land surface
Variation of Urban Heat Island (UHI) within the city as four grades of land surface temperatures and land surface/cover parameters that contribute to UHI effect is analyzed through (i) Zonal statistics of land surface/cover parameters per UHI grade
Parameters derived from the images; greenness and imperviousness compared with nighttime UHIs show a pattern similar to that in daytime UHIs
Summary
Urban growth and sprawl have drastically altered the biophysical environment with the most evident change occurring as the replacement of soil and vegetation cover with impervious urban materials, such as concrete, asphalt, and building materials, which affect the albedo, evapotranspiration and runoff characteristics of the land surface. There is still a strong trend of urbanization where the rate of increase in population is twice the Turkey‟s average Land surface temperatures were classified into four grades converging to equal count of pixels per class These classes were than evaluated for their relationship with factors that generate UHI effect, quantified as „land surface/cover parameters‟ to understand the relative impact of these factors to the intensity of the Urban Heat Island effect. To ensure an effective and coherent development of adaptation strategies aimed at improvement of the urban environment through mitigation of Urban Heat Island effect, a better understanding of the spatial and temporal intra-city variability of UHI and the influence of land surface parameters therein is needed. Knowledge of the LST is of fundamental importance in many applications including urban climate among others (Li et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
