Proposition of a "vegetation fraction" index and its relationship with air temperature and thermal comfort changes during daytime in summer in Curitiba

Abstract This paper analyses the impact of the introduction of green areas on the reduction of pedestrian heat stress in days with heat discomfort. The paper focuses on two relevant urban mobility initiatives that use greenery enhancement as a strategy for the requalification of urban environments in Curitiba: (1) the proposal of the first underground railway system in the state and (2) the transformation of an interstate highway into an urban avenue. Segments of such projects are evaluated as study areas (Sete de Setembro and Linha Verde) with the aim of proposing an index that estimates the vegetation cover needed to promote air temperature drops at the pedestrian scale during daytime in summer. Additionally, the study analyses the impact on thermal comfort through the universal thermal climate index (UTCI). For that purpose, we carried out a field study where we monitored relevant meteorological data, as well as computer simulations using the ENVI-met model. Results suggest that an increase of 70% in vegetated fraction would be needed to offset 1°C in mean ambient temperature in the area analysed, which represents the cooling potential of vegetation fractions in urban conditions.