Street canyon design and improvement potential for urban open spaces; the influence of canyon aspect ratio and orientation on microclimate and outdoor comfort

Urban morphology and material properties are critical parameters in the formation of outdoor microclimates and their effects on the thermal comfort of pedestrians. Despite considerable amounts of previous and ongoing research the scientific research results have not yet been fully adopted on urban projects. The present paper aims to contribute empirical and analytical results that highlight potential improvements that can be achieved through urban design. The paper draws upon environmental measurements, taken in both winter and summer periods, in 18 street canyons located in a dense central area of the city of Thessaloniki in northern Greece. The measurements are complemented by microclimate simulation studies involving modelling of the 18 street canyons as well as a number of generic cases. The results of these studies suggest the most favourable canyon geometries in terms of pedestrian thermal comfort and support the incorporation of basic climatic parameters into urban design.