Quantifying Urban Park Cooling Effects and Tri-Factor Synergistic Mechanisms: A Case Study of Nanjing’s Central Districts

Urban parks play a vital role in mitigating the urban heat island effect and enhancing urban climate resilience. However, quantitative characterization of park cooling effects and the synergistic mechanisms among multiple factors remains limited. Focusing on the central urban area of Nanjing, a typical high-density subtropical city, this study analyzes Landsat 8/9 imagery from 2022 to 2025. The inflection point method was used to quantify three core indicators—cooling intensity, cooling distance, and cooling efficiency—while Pearson correlation analysis was applied to identify key drivers and examine synergistic relationships. The results show that (1) urban parks exhibit a “central aggregation–peripheral diffusion” pattern, which corresponds to pronounced spatial variability in the thermal environment; (2) park cooling effects display strong spatiotemporal heterogeneity, with notable interannual fluctuations in cooling intensity and a relatively stable cooling distance of approximately 400–500 m; and (3) cooling performance is primarily governed by tri-factor synergy among park size, vegetation characteristics, and surrounding urban environmental conditions. Park size largely determines the cooling extent, whereas underlying surface properties and building density regulate or constrain cooling. These findings clarify quantitative patterns and composite drivers of park cooling in high-density cities and provide evidence to support climate-adaptive green space planning and urban heat mitigation strategies.