Modeling the Surface Urban Heat Island (SUHI) to study of its relationship with variations in the thermal field and with the indices of land use in the metropolitan area of Granada (Spain)

Abstract

• 1°) Increases in LST (2.2°C) and SUHI (0.6°C) between 1985 and 2020 are confirmed. • 2°) An increase in the UHS (20.4%) is situated in the areas having the highest SUHI. • 3°) There is an increase of 26.2% in class 6 and a reduction in class 1 of -25.5%. • 4°) Areas without vegetation, industrial and commercial are the great focuses of UHS. Understanding just how the increase in the Earth's Surface Temperature (LST) is related to alterations of the urban climate —Surface Urban Heat Island (SUHI) or Urban Hotspots (UHS)— and with the deterioration of cities´ environmental quality has become a great challenge. Societies worldwide seek actions that might break these trends and improve the quality of life of local inhabitants. In this research, with the help of Landsat 5, 7 and 8 satellite images, the evolution of land use/cover (LULC), LST and SUHI were studied over a long period, from 1985 to 2020, in the metropolitan area of the city of Granada (Spain). The aim was to evaluate how these variables, together with the Urban Index (UI), Normalized Difference Built-up Index (NDBI), Normalized Difference Vegetation Index (NDVI) and Proportion of Vegetation (PV), have influenced the variability of the UHS and the level of thermal comfort according to the Urban Thermal Field Variance Index (UTFVI). Reported as results, corroborated by statistical analysis, are mean increases in LST (2.2°C), SUHI (0.6°C), UHS (20.4%), and class 6 of the UTFV (26.2%). NDBI and UI are associated with high variations in LULCs. These have suffered increases in built-up and bare soil coverage, and decreases in water bodies, vegetation and farmland coverage.