Cooling Effects of Urban Park Green Spaces in Downtown Qingdao

Global climate warming and rapid urbanization have intensified the urban heat island effect (UHI). Previous studies indicated that urban parks could effectively mitigate the UHI and improve urban thermal environments. This study aimed to quantify the cooling effect of 64 urban park green spaces in downtown Qingdao. Park cooling intensity (PCI), park cooling gradient (PCG), park cooling area (PCA), and park cooling efficiency (PCE) were selected as indicators to quantify the cooling effect of park green space. These four indicators comprehensively assessed park cooling effects in terms of the maximum value and cumulative value, respectively. Key factors influencing cooling factors and their relative importance were analyzed. The results showed that the mean PCI, PCG, PCA, and PCE were, respectively, 0.02 °C, 0.71, 63.72 ha, and 10.71 °C for the 64 park green spaces. The average temperature reduction and cooling distance were, respectively, 3.35 °C and 211.53 m. Correlation analysis revealed that park area, park perimeter, and NDVI (Normalized Difference Vegetation Index) were significantly positively correlated with PCA, PCI, and PCG. Conversely, these factors presented a significant negative correlation with PCE. Additionally, water body ratio and green space ratio were positively correlated with PCA, while green space ratio was also positively correlated with PCI. The threshold value of efficiency (TVoE), which was calculated based on PCA, was 30.24 ha. TVoE represented the minimum area of urban park green space required to maximize cooling benefits. By means of Ward’s hierarchical clustering method, the 64 park green spaces were classified into four cooling clusters, which were dominated by differentiated cooling metrics and characterized by distinct internal landscapes and surrounding environments. Cluster 1 accounted for 43.75% of the 64 park green spaces, and it was dominated by PCI and PCG. These findings would provide crucial insights for optimizing urban thermal environments, enhancing livability, and promoting sustainable urban planning.