Climatological analysis of the mitigating effect of vegetation on the urban heat island of Milan, Italy

The urban heat island (UHI) of Milan (Italy) was analyzed by means of an Energy Balance Model calibrated for four different sites representative of an urban park, the UHI plateau and the UHI peak of the selected town. The model was driven by weather stations data and parameterized as a function of land use, urban morphology, human activities and soil hydrology. A run of the model on the 1981–2014 period was carried out on four hourly datasets. Results provided useful statistics of energy balance termsand the climate risk of extreme thermal events (sensible heat fraction of the total turbulent flux H% exceeding specific thresholds). Results for summer (June– August trimester) show that the mitigation of climate risk of high values of H% given by the urban park is more effective for June than for July and August.We also discuss the relevance of enhanced soil water reservoirs in urban green areas to improve the mitigating effect of urban vegetation on UHI by both the substitution of sensible heat fluxes with latent heat ones and the increase of the shading effect of tree canopies.