Cartographic and geostatistical characterization of the surface urban heat island: driving forces and cooling sources in a Mediterranean foothill city

Global warming is amplifying surface urban heat islands (SUHI) in Mediterranean cities, whereas interactions between expanding urban areas and adjacent mountain forests remain underexplored, particularly in foothill cities where forest cover and elevation jointly shape the urban thermal regime. Chréa National Park, a large forested massif directly adjoining the city of Blida (Algeria) and reaching 1629 m in elevation, offers a case, rarely documented at this scale, in which orographic and vegetative cooling act jointly on a city. This study analyzes the SUHI dynamics of Blida from 2004 to 2024 and quantifies the cooling effect exerted by the park. Using 75 Landsat images, Random Forest land-cover classification, and a 300 m analysis grid whose resolution was formally justified through semivariogram analysis, land surface temperature (LST) was related to NDVI, NDBI, and topography through both global correlation and geographically weighted regression (GWR), the latter capturing the spatial non-stationarity of these relationships across the urban–mountain gradient. The results show rapid urban expansion at the expense of forests, accompanied by marked surface warming. Multi-ring buffer analysis reveals that Chréa Park provides a strong cooling intensity extending more than 2.5 km into the urban area, exceeding typical urban park effects. These findings highlight the need to protect a wide buffer zone at the mountain foot and promote inner-city renaturation, thereby offering operational indicators for climate adaptation in Mediterranean mountain cities.