Abstract
With the growth of cities, the ambient air temperatures (Ta) inside the urban areas are expected to be higher compared to the surrounding rural areas, creating urban heat island (UHI) phenomenon. The city of Baghdad is an example of a hot dry climate cities and during summer, the UHI intensity is significantly affected by the extreme direct solar radiation and leads to outdoor thermal discomfort. Also it causes an increase in energy consumption and air pollution. This research work focuses on the effect of urban geometry and green area in the formation of heat island through a study of two different fabrics of residential neighbourhoods. The height to width ratio (H/W) and vegetation are adopted while the materials of buildings were unified in all study cases. Three-dimensional numerical software Envi-met 4.1 was utilized to analyze and assess the studied parameters including: ambient air temperature (Ta), street surface temperature (Ts) and mean radiant temperature (Tmrt). This study has given a better understanding of the role of urban geometry and green area on forming the UHI that influence on the microclimatic conditions in hot dry climate of the city of Baghdad. So that helped to generate guidelines of urban design and planning practices for a better thermal performance in hot and dry cities.
Highlights
Day after day the cities growth and became bigger and bigger and the ambient air temperatures (Ta) inside the urban cores are expected to be higher than that in their surrounding countryside, creating urban heat island (UHI) phenomenon[1,2,3,4]
The bad effect of the urban heat island (UHI) phenomenon, on energy use, human health and air quality as well as its significant effect on human comfort, many researchers are focusing on the possible strategies for mitigating UHI and many of them are interested to investigate at the scale of neighbours [4,5,6,7]
This helped to understand many of the current environmental problems where it let to quantify the influences of zone changes on microclimate conditions and human thermal comfort, through microclimate models such as Envi-met [5], [16]
Summary
Day after day the cities growth and became bigger and bigger and the ambient air temperatures (Ta) inside the urban cores are expected to be higher than that in their surrounding countryside, creating urban heat island (UHI) phenomenon[1,2,3,4]. Investigation that studies the impact of urban configurations variables in hot dry climate (density, urban canyons, and orientation) in forming the UHI effect in cities is still required [2], [17]–[20]. The geometry of urban canyons can influence the speed of airflow for natural ventilation system (NVS) and can shape shaded paths for pedestrians. This geometry is expressed by the ratio of building height (H) and street width (H/W), or the aspect ratio [16], [20]. The current study focuses on the city of Baghdad, the largest urban area in Iraq [21]. A comparison have been made to find out the impact of these UHI mitigation strategies on thermal comfort in the selected area
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