Multitemporal assessment of Krakow’s urban microclimate (2002–2023) using satellite-derived land surface temperature, NDVI, and NDBI

Abstract

Rapid urbanization has the potential to significantly alter local microclimates through the urban heat islands (UHI) effect. This study examines the spatial and temporal changes in land surface temperature (LST) in Krakow, Poland, from 2002 to 2023 in relation to changes in urban land cover. Multispectral satellite imagery from the Landsat 7/8/9 and Sentinel‑2 missions (clear-sky August scenes at ~5-year intervals) was processed using Google Earth Engine to derive LST and spectral indices. The normalized difference vegetation index (NDVI) and normalized difference built-up index (NDBI) were computed to quantify vegetation loss and built-up area expansion, respectively. A supervised land cover classification (random forest) identified five classes – vegetation, water, built-up areas, roads, and bare soil – providing land cover maps for each analysis year. Satellite-derived LST was validated against in situ ground temperature measurements from 17 sensors deployed across the city in summer 2023. The results reveal pronounced surface warming in Krakow’s urban core and in newly urbanized districts, corresponding to areas of intensive development and vegetation decline. Statistically, LST was negatively correlated with NDVI and positively correlated with NDBI, confirming that reduced green cover and increased impervious surfaces exacerbate surface heating. The satellite LST showed strong agreement with ground measurements, supporting the reliability of the remote sensing approach. Our integrated methodology and findings underscore the impact of urbanization on the city’s microclimate and the critical role of green infrastructure in mitigating UHI effects. This approach provides a framework for evidence-based urban planning and climate adaptation strategies in other Central European cities.