Estimating the cooling effect magnitude of urban vegetation in different climate zones using multi-source remote sensing

Vegetation is effective in mitigating the urban heat island effect by canopy shade and evapotranspiration. Acquiring the vegetation cooling effect magnitude (Delta T) quickly and accurately has been the focus of thermal mitigation in urban areas. Traditional field observations are usually restricted to one or few cities, while large-scale assessment models mostly focus on inconsistent parameters, leading to contradictory results. In this study, we collected 3970 samples of observed vegetation-induced Delta T worldwide to assess their relationship with leaf area index (LAI) and evapotranspiration (ET) for different vegetation types within various climate zones (arid, semi-arid/humid, humid, and extreme humid zones). Results showed that urban vegetation ET and LAI have diverse correlations (i.e., linear/nonlinear) with Delta T, and the ET-cooling and LAI-shading effect dominate differently in each climate zone. In addition, urban vegetation cooling effect empirical models were established based on a multivariate regression analysis using the above two parameters. Application of global seasonal urban vegetation cooling effect analysis based on these empirical models enable us to readily achieve Delta T on various scales around the world. The finding of this study can be used as guidance to select the appropriate vegetation types for urban green space design and construction to cool the thermal environments in urban areas.