Modeling Tree Shade Effect on Urban Ground Surface Temperature

TLDR

Urban forests are increasingly recognized as microclimate modifiers, with tree shade and evapotranspiration influencing energy fluxes and improving human health and outdoor comfort. This study aims to assess how surface temperature varies under the shade of different tree species and to evaluate a proposed heat‑transfer model’s predictive capability. Surface temperature data from asphalt and grass in Florence’s Cascine park were collected under various shading conditions and used to test a one‑dimensional heat‑transfer model that incorporates plant canopy effects via infrared radiation and leaf area index of ten common Italian tree species. The model shows that asphalt temperatures decrease by 13.8–22.8 °C with increasing canopy LAI, grass temperatures decline 6.9–9.4 °C, and soil moisture also influences grass cooling, confirming the model’s usefulness for estimating pavement temperatures and urban microclimate.

Abstract

There is growing interest in the role that urban forests can play as urban microclimate modifiers. Tree shade and evapotranspiration affect energy fluxes and mitigate microclimate conditions, with beneficial effects on human health and outdoor comfort. The aim of this study was to investigate surface temperature () variability under the shade of different tree species and to test the capability in predicting of a proposed heat transfer model. Surface temperature data on asphalt and grass under different shading conditions were collected in the Cascine park, Florence, Italy, and were used to test the performance of a one-dimensional heat transfer model integrated with a routine for estimating the effect of plant canopies on surface heat transfer. Shading effects of 10 tree species commonly used in Italian urban settings were determined by considering the infrared radiation and the tree canopy leaf area index (LAI). The results indicate that, on asphalt, was negatively related to the LAI of trees ( reduction ranging from 13.8 to 22.8°C). On grass, this relationship was weaker probably because of the combined effect of shade and grass evapotranspiration on ( reduction ranged from 6.9 to 9.4°C). A sensitivity analysis confirmed that other factors linked to soil water content play an important role in reduction of grassed areas. Our findings suggest that the energy balance model can be effectively used to estimate of the urban pavement under different shading conditions and can be applied to the analysis of microclimate conditions of urban green spaces.