Quantifying the cooling intensity of urban green spaces (UGSs) on land surface temperature (LST) in Hanoi metropolitan Area, Vietnam

The urban heat island (UHI) effect poses growing environmental and public health challenges in rapidly urbanizing regions. This study quantifies the cooling intensity of Urban Green Spaces (UGS) on Land Surface Temperature (LST) in Hanoi Metropolitan Area, Vietnam. A five-year composite (2020–2024) of Landsat 8 Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) data, supplemented by a Digital Elevation Model (DEM), was processed using the Google Earth Engine (GEE). The LST was retrieved via a validated split-window algorithm and examined alongside key satellite indices, including the Normalized Difference Vegetation Index (NDVI), Relative Surface Evapotranspiration Index (RSETI), and Normalized Difference Built-up Index (NDBI). The cooling capacity of UGS was quantified through the decay analysis across buffer zones, revealing a summer LST reduction of up to 2.14 °C within a 100 m radius, with the effect tapering beyond 800 m. To further explore LST responses under land use/land cover (LULC) change and climate warming scenarios, the Random Forest model was applied. Simulation results indicated that a 10 % increase in vegetation cover reduced LST by 0.56 °C in summer and 0.30 °C in winter, whereas a 10 % decrease led to increases of 0.58 °C and 0.36 °C, respectively. Under a projected + 1.5 °C climate warming scenario, these cooling gains were fully offset, resulting in net LST increases of 0.94 °C in summer and 1.2 °C in winter. Moreover, thermal stress conditions were evaluated utilizing the Urban Thermal Field Variance Index (UTFVI). Vegetation expansion increased thermally comfortable zones (UTFVI < 0) from a baseline of 50–55 % to 60–65 % of urban area, while vegetation loss intensified thermal hotspots (UTFVI ≥ 0), expanding stressed zones to 55–60 %. In conclusion, these findings offer critical, data-driven insights for urban planners, emphasizing the strategic role of green infrastructure in mitigating urban heat and enhancing climate resilience in densely populated environments.