The influence of urban geometry and vegetation on summer thermal comfort: an integrated methodology to assess microclimate variations across Local Climate Zones

Urban areas are unprecedentedly under pressure due to global warming, heatwaves and the urban heat island effect. As thermal stress increases, the evaluation of thermal comfort across the city is crucial to design climate resilient spaces. However, few studies investigate microclimate variations across several areas in the city to understand the influence of geometry and vegetation. This study investigates the role of urban geometry and vegetation in improving pedestrian thermal comfort in Trento, an alpine city in north-eastern Italy. Four neighbourhoods identified by different Local Climate Zones are selected for the analysis. To determine summer outdoor thermal comfort, microclimate parameters and the physiologically equivalent temperature (PET) are calculated through a workflow combining the Urban Weather Generator (UWG) tool and ENVI-met considering the existing spatial configuration of the neighbourhoods in present and future projected climatic contexts. A 24-hour simulation is performed for a hot day and validated through micrometeorological measurements conducted in July 2024. The results show the variations in thermal stress between LCZs and within the areas. While compact areas show higher temperatures during the night, during daytime they have lower values of thermal stress due to shade. Shade provided by geometry seems to have more influence than the effect of vegetation in improving comfort. The proposed workflow starting from a single climate dataset processed with UWG to represent the study areas facilitates the assessment of multiple areas. The results contribute to a better understanding of microclimates in urban areas and of the impact of climate change, vegetation and geometry on heat stress.