Testing the i-Tree Cool Air spatial model to evaluate the contribution of urban green spaces to air temperature mitigation

Cities host more than half of the world's population and this trend is expected to increase in the coming years. Due to global warming, events such as heat waves are increasingly frequent and the effects on human health are very worrying. High temperatures are more prevalent in urban areas where the large percentage of impermeable surfaces contribute to the so-called 'heat island' effect. In this context, urban trees and forests play an important role in air temperature mitigation through evapotranspiration and shading. However, the assessment of their contribution to urban microclimate regulation is often difficult to quantify through direct observations. The use of models allows to evaluate the spatial distribution of air temperature and humidity, based on the presence of tree cover, impervious surface, topography, land use, and weather data. In this study, we applied for the first time on Naples the i-Tree Cool Air model, a spatially explicit air temperature model simulating the effects of land cover changes using the water and energy budget that explicitly accounts for vegetation processes. We modeled air temperature at different times, during summer heat waves, of areas with an increasing tree cover and compared results with direct measurements. The prolonged summer drought in the Mediterranean area significantly reduces the evapotranspiration of trees and thus their contribution to air cooling. A proper planning of green areas in the city, using decision-support tools as the presented model, could increase the human thermal comfort.