Analysis of the Intra-City Variation of Urban Heat Island and Its Relation to Land Surface/Cover Parameters

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.

The Future of Climate-Resilient and Climate-Neutral City in the Temperate Climate Zone

“…Land cover with buildings [ 130 ], building density [ 130 , 131 ], building volume [ 130 ], aspect ratio [ 132 , 133 ], building symmetry [ 131 ], building element proportions [ 130 ], building orientation [ 134 ], building height [ 134 ], and the presence and size of trees [ 135 ] and other shading elements [ 136 ] are parameters that build up SFV. SVF is positively associated with land surface temperature (LST) [ 137 , 138 ], atmospheric temperature (AT) [ 139 , 140 , 141 , 142 , 143 , 144 , 145 ], and the UHI effect [ 146 , 147 , 148 , 149 ], both during the day [ 150 , 151 , 152 , 153 , 154 , 155 , 156 ] and at night [ 157 , 158 , 159 , 160 , 161 , 162 , 163 , 164 ] in all seasons [ 165 ]. Only after a deeper analysis, can the complicated pattern of dependencies governing SVF be seen.…”

“…Therefore, the influence of albedo can be considered only when the surface is exposed to high sunlight during the day [ 166 ]. Other essential elements, such as greenery, take control of the temperature in the case of sunlight absence [ 161 , 183 ]. The higher albedo leads to lower surface and air temperatures [ 132 , 161 , 214 ] and a shorter duration of high temperatures.…”

“…Other essential elements, such as greenery, take control of the temperature in the case of sunlight absence [ 161 , 183 ]. The higher albedo leads to lower surface and air temperatures [ 132 , 161 , 214 ] and a shorter duration of high temperatures. Similarly, materials with lower albedo, e.g., asphalt, increase the ambient temperature and hinder cooling [ 176 ].…”

“…The world of science is divided here. In some studies, albedo has a more significant impact on daytime temperatures [ 151 , 161 , 221 ]. Other studies indicate a more substantial albedo impact at night [ 188 , 212 ].…”

“…This situation may exacerbate thermal and optical discomfort and increase cooling energy consumption by reflecting the radiation inside the buildings in the canyon [ 166 , 227 ]. Thus, it may directly affect the UHI intensity increase [ 161 ]. The solution to this problem is either lowering the street albedo or using retroreflective (RR) materials in the canyon [ 228 ].…”