Impact of urban surfaces’ solar reflectance on air temperature and radiation flux

This study evaluates the effect of urban surfaces’ solar reflectance on the microclimate of a Brazilian city, Balneário Camboriú. A case study of two different geometrical areas of the city's central region was conducted. The influence of solar reflectance was evaluated through computer simulations on the ENVI-met model, validated for a winter and a spring day, according to field measurements. The simulations were performed for twelve combinations of solar reflectance on the roofs, façades, and pavements. The results confirmed that surfaces of high solar reflectance generally contribute to an air-temperature decrease. However, the degree to which each surface's solar reflectance influences the air temperature depends on the solar access (urban geometry, time, and season). In denser areas, the solar reflectance of facades has a greater impact on temperature variation, whereas in open spaces, roofing and paving surfaces are more critical. Impacts on urban microclimate extend beyond air temperatures. The radiation fluxes on two urban canyons revealed that the solar radiation incidence on the paving of a high solar reflectance canyon could be up to three times greater than one with low reflectance.