Summer thermal comfort of pedestrians in diverse urban settings: A mobile study

Urban planning must consider the outdoor thermal comfort of city dwellers, particularly in cities where climate and the effects of climate change may severely influence human health and wellbeing in increasingly hot summers. The role of the urban forest in ameliorating this problem is decisive. The present study is based on a campaign of meteorological measurements in a large number of sites using a mobile data collection system to allow a human-centred approach. The aim is to quantify the different microclimates and thermal comfort conditions in six classes of urban morphology, discriminating landtypes with or without trees. In the case study of Florence, local physical characteristics of the sites; Sky View Factor (SVF), tree shade, ground surface cover, and canyon effect, can moderate human exposure to potentially uncomfortable thermal conditions during a typical Mediterranean summer. Significant differences in Universal Thermal Comfort Index (UTCI) were observed between treeless piazzas and streets and landtypes with trees or high height to width ratio (narrow alleys). Varying levels of SVF and tree cover in the sites allowed the construction of multivariate models, which revealed that, during common summer afternoon conditions, decreases of SVF by 12.5% or increases of tree cover by 25% can reduce the UTCI by 1°. Additionally, the total site factor, by incorporating temporally integrated sun exposure with the sky view factor, revealed itself a promising variable for future studies to use.