Linking urban park cool island effects to the landscape patterns inside and outside the park: A simultaneous equation modeling approach

Abstract

Urban parks have significant cooling effects that alleviate the urban heat island (UHI). The park cool island intensity (PCII), the temperature difference between outside and inside a park, is a widely used indicator of a park’s cooling ability. Understanding the driving factors of the PCII is crucial for better urban park planning and management. Taking the subtropical city of Changsha, China, as a case study, factors such as the landscape patterns inside and outside a park and the geometric morphology of a park were investigated, based on 153 urban parks. A novel simultaneous equation modeling (SEM) approach was used to account for the mutual interactions between the temperatures of a park and its buffer. The results show that: (1) Park geometric morphology and landscape patterns inside and outside the park all significantly impact the PCII. Specifically, doubling the park size can increase the PCII by 0.8 K. Increasing by ten percent the tree cover and water cover in the park can enhance the PCII by 0.12 K and 0.41 K, respectively. Increasing the mean tree patch size by 1 ha can increase the PCII by 0.43 K. Decreasing by one unit the mean tree patch shape index can increase the PCII by 0.31 K. (2) An elasticity analysis, which measures the PCII percent change resulting from one percent change in a driving factor, indicates the relative importance ranking of these driving factors: percent cover of impervious surface outside the park (0.77), park size (0.72), percent cover of tree within the park (0.51), percent cover of water within the park (0.12), and mean patch size of tree cover within the park (0.086). To enhance the PCII, we recommend building parks in the hot areas of the city, increasing their size, increasing the percentages of tree cover and water cover in the park, and optimizing the spatial configuration of the tree cover in the park (i.e., aggregating trees in a smaller number of large patches and reducing the irregularity of tree patches).