Enhancing Urban Microclimates: Potential Benefits of Greenery Strategies in a Semi-Arid Environment

Abstract

The emergence of sustainable development gives greenery an important role in urban planning, namely, by recognizing its environmental potential. However, the rapid urbanization that most cities have experienced in the absence of a sustainable urban policy has led to the establishment of urban realms dominated by manmade constructions. This research aims to evaluate the greening’s effect on the urban climate within the semi-arid city of Djelfa (Algeria) during summertime by assigning the most appropriate greenery strategy to ensure optimal thermal conditions. Using a numerical model built with the ENVI-met tool and validated through measurements in situ, four different scenarios are simulated, starting with the existing area and then changing the greenery strategies. The outputs include meteorological parameters and thermal comfort indices (PET and UTCI). The results show that the green area generates a cool island within the urban fabric, with the peak daytime air temperature being reduced by about 4.75 °C. Vegetation densification in the urban space has a higher cooling performance than greening buildings during the daytime. In the evening, the canopy effect of trees is lower and the wind velocity is reduced, which is the main driver in cooling the city at nighttime.