Seasonal impacts of built environment and its interactions on urban park cooling effects in Nanjing, China

Urban parks offer a nature-based solution to mitigate urban heat islands (UHIs). Although the urban park cooling effect (UPCE) has been extensively investigated, the assessment of its seasonal variation remains uncertain, which hinders optimization. Taking 217 parks in Nanjing central districts as samples, this study calculated the urban park cooling magnitude (UPCM) of four seasons and used the turning point method (TPM) to characterize the multidimensional characteristics of the urban park seasonal cooling effect (UPSCE). Using models such as geographic detectors and multiple stepwise regression, we determined the impacts of built environment and its interactions on the UPSCE. According to the results, urban parks demonstrated the best cooling in summer, at 1.28 & DEG;C on average, which was higher than that in spring (1.07 & DEG;C) and autumn (1.01 & DEG;C) and almost four times that in winter (0.30 & DEG;C). The UPCE is greatly affected by factors such as the park area, park perimeter (PP), landscape shape index, normalized difference vegetation index (NDVI), normalized difference water index (NDWI), elevation, and surrounding building density, which vary with seasons. Among them, the NDVI, NDWI, and PP proved to be the dominant factors, explaining 55.7%, 53.3%, 62.0%, and 50.5%, respectively, of the variance of UPCM in the four seasons. In addition, the interactions of built environment will significantly enhance the UPCE, and the intensity differ with seasons. These findings will support the development of more sustainable urban microclimate policies and improve the surface thermal environment and thermal comfort of urban parks and their surroundings in different seasons.