Estimating Transpiration and Cooling Effects of 19 Typical Tree Species in Urban Areas Using a Modified Priestley–Taylor Model

ABSTRACT Urban tree transpiration (T) can significantly lower urban temperatures and mitigate the urban heat island effect. The careful selection of suitable tree species for the urban landscape holds immense significance in enhancing the quality of the human living environment. However, there remains a deficit of effective models capable of accurately assessing urban T and its associated cooling effects. In this study, we have developed a modified Priestley–Taylor (P–T mc ) model to assess T. This P–T mc model calculates the vegetation P–T coefficient ( α v ) through a machine learning technique that incorporates soil, meteorological, and vegetation parameters. Moreover, the P–T mc model integrates CO 2 concentration and flux data to enhance the precision of T simulations. Upon validation using data from two eddy correlation (EC) sites and stable hydrogen and oxygen isotope observation sites, it was demonstrated that the P–T mc model exhibits enhanced simulation capabilities for T when contrasted with the original P–T model. The root‐mean‐square error (RMSE) for the P–T mc model was determined to be 0.025 mm/hf in T simulation. The transpiration and cooling effectiveness of 19 representative urban tree species were further assessed using the P–T mc model framework. Among the selected 19 urban tree species, Ficus virens demonstrated the most impressive cooling performance. For Ficus virens, the average vegetation latent heat flux ( λT ) was measured at 6.18 MJ m 2 /d, while the temperature reduction (Δ T ) reached 4.66°C m 2 /d. In contrast, Palmae exhibited the least effective cooling, with average λT and Δ T values of only 0.89 MJ m 2 /d and 0.67°C m 2 /d, respectively. Correlation analysis indicated that the cooling effects of various urban tree species were primarily influenced by tree morphology. Specifically, higher values of leaf area index (LAI) and crown area ( C a ) were associated with better cooling performance, while increased tree height led to reduced cooling effectiveness. This study conducted a comprehensive evaluation of the cooling effects exhibited by diverse urban tree species through the utilisation of the proposed P–T mc model. The outcomes of our investigation offer a more robust scientific foundation for urban landscape planning and the selection of tree species.