A hydrological-energy balance model to assess land surface temperature at the urban scale. The case study of Milano, Italy.

Abstract

We develop, and test an energy/water balance model, Poli-HE, to compute surface energy, and mass fluxes between soil surfaces, and shallow atmospheric layers. The case study is the city of Milano, Italy, where we assess Urban Heat Island (UHI). We calculate land surface temperature (LST) under given climate conditions, including different UHI in paved, and green areas. Spatially distributed LST is assessed, and pixel displaying mixed paved/green areas are dealt with using Vegetation Fraction FV from satellite images. Joint energy and water balance share soil water content, and latent heat flux, as a function of LST. Nine meteorological stations distributed in Milano were used to gather model’s input of global radiation, air temperature, precipitation, wind velocity, and air humidity, during January 1^st, 2010 to December 31^st, 2022. Satellite images provided Land Surface Temperature for model tuning. Poli-HE well mimics spatial distribution of urban LST. During summer, when LST is higher, paved, and green surfaces differ by about + 3.7 °C, reaching up to +4.5°C at times. We offer a quantitative approach for urban authorities and professionals, usable for current and future planning, and projects within the context of national, and international adaptation and mitigation measures.