Research on the cool island effect of green spaces in megacity cores: A case study of the main urban area of Xi'an, China

Optimizing urban green spaces (UGS) cool island effects is crucial for urban climate resilience. In the main urban region of Xi'an, the UGS cool island effect was thoroughly investigated in this study, which covered pattern detection, characteristic analysis, scale consideration, mechanism discovery, and layout optimization. Among the primary research instruments were the Generalized Additive Model (GAM), the urban cooling model, and optimal parameter geographic identification technology. According to the study, within a 200-meter radius, UGS can considerably lower land surface temperature (LST). The cool island effect is mostly caused by wetlands and woods, and it is most noticeable around parks, water systems, and lakes in the Baqiao District. When exploring the factors influencing HMI, we found that two-dimensional UGS landscape indicators dominate, followed closely by socio-economic factors, with three-dimensional building indicators ranking third. Notably, the interactions between different pairs of factors were all more pronounced than the effects of individual factors. The Sky View Factor (SVF), a crucial three-dimensional indicator, has a significant impact that cannot be disregarded. Complex nonlinear interactions between these major components and HMI are evident, and certain elements may have threshold effects. Consideration of multi-factor interactions and geographical variations is necessary for efficient UGS layout optimization.