Interaction effects of blue-green spaces’ morphological indicators on thermal comfort during summer: evidence from urban parks in Chongqing, China

Blue-green space morphology may influence thermal comfort through both independent and interactive effects, yet interactions remain underexplored. To examine them, 120 buffer zones were established across six urban parks in Chongqing. Physiological Equivalent Temperature (PET) and six blue-green spaces’ morphological indicators were assessed for each buffer using field measurements, simulations, and ArcGIS. Three forms of interaction were introduced: synergy, acceleration, and compensation. Random Forest and SHapley Additive exPlanation models were used to identify direction and importance of indicator interactions in influencing PET, and revealed temporal variations. Acceleration had the strongest impact on reducing PET, followed by synergistic and compensatory effects. The green space ratio (GSR) quadratic term exhibited an acceleration effect and reduced PET. Indicators like water area ratio (WAR), total area ratio of blue-green space (TARBG), and shared shoreline length ratio (SSLR) acted synergistically. When the effect of green or blue spaces in reducing PET was weakened, SSLR moderately supplemented regulation. In the morning, GSR and WAR accelerated evapotranspiration; at noon, SSLR compensated limited water body cooling via ventilation and evaporation; in the evening, TARBG and other indicators reduced PET via synergy and compensation. These findings provide a theoretical foundation for optimizing the configuration of blue-green spaces.