Climate sensitivity and area efficiency threshold of urban park cooling effects: a cross-climate zone comparative analysis

Urban parks play a critical role in alleviating urban heat island effects, affecting human development directly and background climatic conditions greatly influence the intensity of their cooling effects. Here, focusing on 108 urban parks in four major cities across different climate zones—temperate subhumid continental climate (Shenyang city), north temperate continental monsoon climate (Zhengzhou city), subtropical monsoon humid climate (Wuhan city), and subtropical monsoon climate (Nanning city) in China, we explored the optimal area threshold for cooling effectiveness in urban parks under different background climatic conditions. Using land surface temperature (LST) inversion data, the cooling intensity and cooling distance of each park were analyzed by temperature classification, buffer analysis and segmentation function, and the influence of 11 landscape elements on the cooling effect characteristics of parks and regional differences were explored. The results indicate: (1) Surface temperature inversion aligns with actual conditions during summer noon, with all four cities experiencing a heat island effect. (2) The average park cooling effect distance (PCEd) across all parks in the four cities is 161 m, the average park cooling effect intensity (PCEi) was 2.73 °C, the maximum PCEd was 437.35 m, and the maximum PCEi reached 6.9 °C. (3) The perimeter-to-area ratio (PARA) is the most influential parameter negatively correlated with park cooling effect, while the most influential positively correlated factor is park area (AREA). Interestingly, the number of factors that enhance the park cooling effect decreased from north to south. (4) The park area thresholds for optimal cooling effect in Shenyang, Zhengzhou, Wuhan, and Nanning was 7.27 ha, 8.08 ha, 9.69 ha, and 44.42 ha, respectively. All four cities in the study area experience urban heat island effects. Overall, the most influential positive landscape element correlating with the park cooling effect was park area. Therefore, planning parks according to optimal cooling effect area thresholds can maximize land use efficiency, enhance cooling value, and promote urban and human development.