A predictive analysis of thermal stress in a densifying urban business district under summer daytime conditions in a Mediterranean City

Abstract

A new urban master plan in the metropolitan area of Tel Aviv, Israel calls for the extreme densification of an already intensively-built business district. This study assesses the existing daytime thermal stress experienced by pedestrians under the Mediterranean climatic conditions of the region during the summer season, and predicts future changes under various development scenarios. Microclimatic measurements were used to calculate the Index of Thermal Stress (ITS) under present conditions, and possible future scenarios were modeled by hypothetically altering the urban geometry and subjecting the results to a series of sensitivity analyses. Findings reveal that the net impact of taller buildings is a reduction in pedestrian thermal stress on clear summer days, since the deep shading of narrow street canyons lowers the radiant heat exposure – outweighing the weaker convective cooling that is expected due to higher air temperature and lower wind speed. Nonetheless, outdoor summer conditions remain thermally stressful during daytime hours, and there is a need for appropriate urban design strategies to further mitigate urban warming. Additional shading improved thermal comfort at certain times and street orientations, but available space for street trees is limited. This emphasizes the need for creative solutions, such as building-integrated green infrastructure.