The impact of vegetation on urban microclimate to counterbalance built density in a subtropical changing climate

Abstract

The purpose of this research is to assess the microscale cooling effects of vegetation in urban environment, especially during daytime, to counterbalance urban warming effects resulting from an increase in built density in a subtropical climate. Considering that Brazil’s climate will be warmer in the coming decades, the paper presents a brief review of planning with high-density and urban greening, having in mind that even low-density land use can contribute to urban heating, depending on the urban occupation pattern. In high-density cities, the most important vegetation effect is to prevent heating in urban canyons, decreasing solar radiation absorption by shading and evapotranspiration. Parametric studies exploring different scenarios of high-density urban blocks and greening have been carried out to investigate different distributions of dense trees to ameliorate urban microclimate using ENVI-met V4 Preview I, previously calibrated with field measurements of local climate and vegetation data. Aiming to benefit urban activities, air, surface and mean radiant temperatures at the pedestrian level are compared among different greening strategies and built densities’ scenarios. Based on the results, two outdoor comfort indexes TEP –Temperature of Equivalent Perception and PET – Physiological Equivalent Temperature were applied to verify the contribution of vegetation to better comfort conditions.