Quantification of urban heat intensity with land use/land cover changes using Landsat satellite data over urban landscapes

Urban heat island (UHI) is a phenomenon which may have adverse effects on our environment and is stimulated as a result of urbanization or land cover changes. Thermal remote sensing has been found beneficial to study the effect of urbanization on UHI intensity. This paper analyses the variation in land surface temperature (LST) with land cover changes in Varanasi city of India from 1989 to 2018 using Landsat satellite images. A new index named Urban Heat Intensity Ratio Index (UHIRI) was proposed to quantify the urban heat intensity from 1989 to 2018 which was found to increase from 0.36 in year 1989 to 0.87 in year 2018. Further, contribution of each land cover towards UHI was determined using land cover contribution index (LCCI). The negative value of LCCI for water and vegetation indicates its negative contribution towards UHI, whereas positive value of LCCI for bare soil and built-ups depicted its positive contribution towards UHI. The LCCI value for urban land cover shows significant increase in 29 years, i.e. 0.49, 1.43, 3.40 and 4.37 for years 1989, 1997, 2008 and 2018, respectively. The changes in normalized LST from years 1989 to 2018 for the conversion of bare land to built-ups and vegetation to built-ups were found to be as −0.11 and 0.42, respectively. This led to conclusion that the replacement of vegetation with urban land cover has severe impact on increasing UHI intensity.