Impact of boundary conditions in a microclimate model on mitigation strategies affecting temperature, relative humidity, and wind speed in a Mediterranean city

Abstract

This paper investigates several mitigation strategies to detect which has the biggest effect on thermal comfort parameters, namely temperature, relative humidity, and wind speed in a neighborhood in Beirut, the capital city of Lebanon. The strategies include changing the ground surface albedo, replacing old buildings with new ones, and adding vegetation. The simulations, conducted on ENVI-met V4 software, were run on the 20th of January and August representing the two major seasons in the country, winter and summer, respectively. The simulations were carried out on a 200 x 200 x 46-m domain at a resolution of 2 m, which permits the study of small-scale interfaces between buildings, surfaces, and vegetation. The paper then represents various types of lateral boundary conditions (LBC) and illustrates the effects of expanding the area of buildings surrounding the field of interest. The present study will allow urban planners to determine the policies required to ameliorate the urban living environment in cities like Beirut. The simulation exhibits that the greatest impact on thermal comfort parameters is vegetation. It was eminent that the occupancy of vegetation is the most effective mitigation strategy given its capability of enhancing the thermal comfort conditions at the pedestrian's pathway sidewalks. The maximum decrease in air temperature was 2.4 °C at 17:00 on August 20th, while the maximum decrease in the mean radiant temperature was 10.5 °C at 12 at noon on the 20th of August. © 2021 Elsevier Ltd