Urban microclimate simulations based on GIS data to mitigate thermal hot-spots: Tree design scenarios in an industrial area of Florence

Surface thermal hot-spot areas, and especially industrial and commercial areas, mainly characterized by high artificial surfaces and low vegetation coverages, consistently affect the livability in urban areas. In this study, one of the warmest areas of Florence (Italy), the main agri-food market was selected to perform three tree design mitigation scenarios: a) mitigation intervention by using 5-m high trees (T5), b) intervention with 10-m high trees (T10) and c) intervention alternating 5- and 10-m high trees (T5-10). The methodology was based on the microclimate monitoring and simulation by urban characterization, involving open GIS data from different data sources by using spatial software tools (QGIS and the ENVI-met software). Thermal patterns (air Temperature, AT; Mean Radiant Temperature, MRT; Surface Temperature, ST; Universal Thermal Climate Index, UTCI) were simulated at 9 a.m. and 3 p.m. by the three scenarios and were then compared through a non-parametric statistical test with the ex-ante thermal situation. The results revealed that a 10% increase in the tree canopy on road surfaces had a significant impact on the thermal environment, showing the greatest effect at the surface level. The greatest cooling impact was observed during the afternoon (3 p.m.) considering the T10 three design scenario: MRT, ST and UTCI decreased by 6.0 °C, 4.1 °C and 1.7 °C respectively when compare to the ex-ante situation. These findings provide very useful information for urban planners and landscape architects to plan targeted interventions aimed at mitigating urban thermal anomalies in industrial areas.