Optimizing the spatial arrangement of trees in residential neighborhoods for better cooling effects: Integrating modeling with in-situ measurements

Trees have long been recognized as effective for mitigating urban heat islands by reducing air temperature through evapotranspiration and intercepting shortwave radiation that heat up land surfaces. Many studies have shown that both the composition and configuration of vegetation can contribute to heat reduction at the city scale. Fewer studies, however, have focused on cooling mechanisms at the neighborhood scale. Here, we integrate modeling with in situ measurements to investigate how different spatial arrangements of trees in residential neighborhoods affect their cooling effects. We conducted the research in a residential neighborhood with high-rise apartment buildings in Beijing. We tested four scenarios with different spatial arrangements of trees, and quantified their effects on cooling. We used the high spatial and temporal resolution microclimate model ENVI-met and validated the model with in situ measurements. We found: (1) Different spatial arrangements had differentiated effects on intercepting shortwave radiation, which led to variations in air temperature. For example, new trees that were completely exposed to solar radiation had stronger cooling effects (air temperature was 0.22 degrees C lower) than new trees that were located in the shadow of surrounding buildings. (2) Different spatial arrangements led to obviously different effects of sensible heat reduction, with a maximum difference of 14.84 x 10(8) J/ha. Our results underscore the importance of the spatial arrangement of trees on cooling in residential neighborhoods. These results have important implications in urban planning and design at the neighborhood scale.