How to quantify the cooling effect of urban parks? Linking maximum and accumulation perspectives

Urban parks can significantly alleviate the urban heat island, an ecological issue caused by urbanization. Clarifying urban park cooling effect can improve climate change adaptability and urban sustainability. However, park cooling effects were mainly explored in maximum perspective in previous studies, without considering the cumulative impact resulting from spatial continuity. Therefore, focusing on 24 urban parks in the main city zone of Shenzhen, China, such cumulative indexes as park cooling intensity and park cooling gradient, were proposed in this study and integrated with maximum indexes of park cooling area and park cooling efficiency, so as to explore park cooling effects comprehensively. The results showed that the park areas and cold spot areas of land surface temperature overlapped spatially by 64.40%. The partial correlation analysis showed that, park perimeter, area and shape index were significantly and positively correlated with park cooling area, with significantly negative correlation for park cooling efficiency. The vegetation index was significantly and positively correlated with park cooling intensity and park cooling gradient, and the impact of water body area ratio to all the four park cooling indexes was not significant. Then cooling effects of 24 urban parks were classified into four cooling capacity bundles, which showed that parks designed to serve different social functions behaved different cooling effects. The cooling effect of comprehensive parks was more efficient, with the same low value of all four cooling indexes for theme parks, high cooling intensity and cooling gradient for small ecological parks, and the highest cooling area for large ecological parks. This study proposed a comprehensive approach to measuring park cooling effects with both maximum and accumulation perspectives, which can guide urban park planning and design to maximize the ecological benefits.