Assessment of Urban Outdoor Comfort Variation in a Northwestern Moroccan City – Toward the Implementation of Effective Mitigation Strategies

Abstract

Studying urban outdoor comfort has become a necessary approach to achieving sustainability at multiple levels. Today, many urban projects incorporate new mitigation strategies such as green and blue patterns when it is difficult to modify urban configuration and density. This study aims to investigate urban outdoor comfort variation in a northwestern Moroccan city, where urban planning is rapidly evolving due to local socio-economic dynamics. Various urban areas were analyzed during summer conditions from two perspectives. The first one focused on studying the air quality and involved the use of Google Earth Engine platform to extract data on air pollutants (NO2, CO, formaldehyde and aerosols). Second, in-situ monitoring was carried out using four main parameters (temperature, humidity, solar illuminance and sound levels). Other factors such as urban density, urban greening and water components were also assessed. Air quality findings revealed that the main sources of air pollution were concentrated in the industrial zone and the backwater. This led to a significant impact on the air quality of the city center. The results also indicated minor effect of vegetation on the density of the pollutants studied. Based on the in-situ monitoring, results highlighted variations between different sites, which can be attributed to differences in urban morphology and the use of various plant species for urban vegetation and the water proximity. We have identified four main species on the site: Populus nigra and Platanus orientalis are deciduous trees that provide significant shade and contribute to outdoor urban comfort, resulting in a decrease of temperature by 0.8 degrees Celsius compared to open bare lands where palm trees provide minimal shading. Furthermore, areas with deciduous trees experience a noise reduction of 4.6 decibels compared to open bare lands. Grass and linear bushes only produce evapotranspiration benefits. In addition, we have found that proximity to water sources can reduce outdoor temperature. Green and blue strategies play an essential role in optimizing urban comfort. However, their urban implementation is not entirely effective, focusing more on aesthetic aspects than functional factors to optimize outdoor comfort. Results from the present study can be used to better influence future mitigation strategies and implement new sustainable tools.