ENVI-Met Simulation on Cooling and Humidifying Effects of Plant Communities in Urban Parks: A Case Study of Tianjin Water Park

Under global climate change and rapid urbanization, urban heat island and dry island effects threaten residents’ thermal comfort and public health, making microclimate regulation by urban green spaces a core issue. However, the interaction between vertical structure and horizontal spatial type of plant communities remains unclear. This study selected Tianjin Water Park as the study area. Based on field temperature and humidity observations during the high-temperature period in summer 2024, ENVI-met was locally validated and used for multi-scenario numerical simulations of typical plant communities. Results showed that all vegetation structure types had cooling and humidifying effects. Tree–shrub–herb communities showed the strongest cooling and humidifying performance, while shrub–herb communities showed the weakest performance (p < 0.05). A higher degree of horizontal enclosure was associated with more stable temperature and humidity conditions. For cooling, an interaction-dependent effect was found between vertical structure and horizontal spatial type: the cooling benefit of greater vertical structural complexity increased with the degree of enclosure. These findings clarify the independent and interactive mechanisms by which plant community structure regulates microclimate. They also provide a scientific basis and quantitative reference for optimizing plant arrangement in urban parks.