Multi-scaled mechanisms and planning solutions for urban park-based microclimate resilience – A case from Xi'an, China

Urban parks are important nature-based solutions for mitigating urban heat island impacts. Although previous studies have examined park cooling effects and the role of surrounding built environments, limited attention has been given to how park-scale characteristics and point-scale urban morphology jointly regulate seasonal variations in the spatial extent and attenuation of both cooling and humidifying effects. This study conducted continuous summer and winter microclimate monitoring at 142 points inside and around eight representative urban parks in Xi'an, China. Air temperature (AT) and relative humidity (RH) were analyzed together with multi-scale morphological indicators using partial least squares regression, random forest modeling, and Shapley additive explanations. Results showed that park interiors were 0.06–1.05 °C cooler than surrounding built-up areas in summer and 0.07–0.72 °C cooler in winter, while interior-surrounding RH differences ranged from −0.02% to 4.22% in summer and from 0.09% to 2.67% in winter. Cooling and humidifying benefits typically extended 0.5–1 park width beyond park boundaries. Within this effective influence range, point-scale urban morphology strongly influenced microclimate regulation: building sky view factor (BSVF) > 79.74% and green coverage ratio (GCR) > 31.87% were associated with a broader spatial influence of summer nighttime cooling, while floor area ratio (FAR) <1.17 was associated with enhanced summer daytime humidification. These findings indicate that urban parks and adjacent built-up areas function as a coupled green-built system. The proposed relative distance-based threshold framework translates cross-scale microclimate mechanisms into planning parameters for climate-adaptive park-neighborhood design.