From cooling pathways to practical acclimating design: Urban park regulating potentials under Extreme Heat Events

Rapid urbanisation and global warming have intensified the frequency and severity of extreme heat events (EHEs), posing substantial challenges in urban areas. The urban park cool island effect (PCI) could aid in the mitigation of and adaptation to EHEs. However, its cooling intensity and underlying mechanisms in metropolitan regions under different heat extremes are unclear. To address this, we quantitatively assessed the PCI effect between EHEs and non-EHEs of two summer periods and identified universal PCI pathways. PCI effects were quantified across 109 urban parks within the Fifth Ring Road of Beijing using the equal radius and turning point methods. We then employed structural equation modelling (SEM) to elucidate the causal pathways among various factors during EHEs and non-EHEs. We found that: (1) the PCI of 109 urban parks was significantly stronger during EHEs than during non-EHEs, with PCI intensity varying from 0 to 10°C, and the PCI exhibiting spatial heterogeneity along the urban–rural gradient; (2) urban park cooling service followed universal pathways between different EHE periods (June 2021 and July 2022) and present different pattern from four non-EHE periods.; (3) the differences between the SEM models were primarily driven by external impervious surfaces, vegetation cover, and three-dimensional building height in the park surrounding areas. This study not only reveals the PCI potentials under different heat extremes, but also deepens our understanding of PCI pathways, providing methodological and theoretical references for urban park extremes-adaptation planning and construction.