Thermal variations and urban compactness: developing UHI indices using remote sensing

Amid growing concerns about climate change, interactions between the urban thermal environment and urban structure have garnered significant attention from researchers and policymakers. Using Bialystok, a medium-sized European city with compact urban structures, as a case study for urban development challenges, the research aimed to show how compact forms affect the expansion, or spillover, of the surface urban heat island (SUHI) using Landsat datasets. The study explored the relationship between SUHI, land use/land cover (LULC), and impervious surface density. The findings revealed that urban expansion contributed to SUHI spillover between 1994 and 2022. It also highlighted the consequences of thermal changes across different LULC classes, indicating that a 10% increase in impervious surface density could raise the land surface temperature (LST) by more than 0.6 °C. However, a non-linear model revealed that specific areas show varying sensitivity to changes in LST. Overheating of artificial surfaces, including housing zones, was identified, consequently affecting 75.5% of the city’s population. The analysis further shows that the density of development contributes to disproportionate exposure to heat. Therefore, the city’s compactness may weaken its heat resilience and increase the likelihood of SUHI occurrence, underscoring the need for strategic cooling measures in urban planning.