Investigation of the Surface Urban Heat Island (SUHI) by two remote sensing-based approaches in Italian regional capitals

This study investigates the Surface Urban Heat Island (SUHI) phenomenon in the twenty Italian regional capitals for the 2013–2023 period by analyzing summer surface temperatures and urban features. Using open data from remote sensing products (such as Landsat-8 and 9 and Sentinel-1 and 2) as well as the Italian Revenue Agency database, this research examines surface temperature differences between central and peripheral urban areas. Two methodological approaches were employed: 1) the Real Estate Market Observatory classification provided by the Italian Revenue Agency (OMI approach) and 2) urbanization levels as defined by the Italian Institute for Environmental Protection and Research (urbanization level approach). High SUHI values were observed in cities with different geographical characteristics, including mountainous areas, with the highest values in L'Aquila, as well as both coastal and inland cities across plain and hilly altitudes. The highest SUHI intensities ranged from 5 °C to nearly 8 °C, with the urbanization level approach highlighting the most pronounced differences. Additionally, central urban areas in most regional capitals were characterized by over 60 % impervious surface coverage and minimal vegetation. Differences in tree cover percentages between urban belts showed significant positive relationships with SUHI intensity in both plain and hilly/mountainous cities. In particular, a highly significant (p < 0.001) positive linear relationship was found in plain cities: for every 10 % increase in tree cover differences between outer and central belts, SUHI intensity increased by about 1.0 °C. These findings provide valuable insights for public administrations planning urban development and reforestation aimed at mitigating extreme thermal conditions. • SUHI intensity in Italian regional capitals was assessed using remote sensing data. •Data sources included Landsat-8/9 (NASA) and Sentinel-1/2 (Copernicus Programme). •High SUHI values were observed in cities with various geographical characteristics. •Several southern coastal cities revealed a reverse SUHI effect. •Tree cover variation between urban belts correlated positively with SUHI intensity.