Numerical Investigation Into the Influence of Geometry and Construction Materials on Urban Street Climate

A numerical model is developed for simulating the nocturnal cooling of the ground and walls in typical urban canyons. The model is capable of dealing with homogeneous as well as inhomogeneous (layered) soil and wall substrates. Experiments carried out with the model show that the difference in the thermal properties of urban asphalt and concrete pavements and the rural dry soil substrate could create urban/rural surface temperature differences of up to 4–5K. In narrow cross-section canyons, the influence of geometry on the street microclimate increases and becomes dominant for aspect ratios exceeding 2. The external surfaces of insulated canyon walls cool drastically overnight and therefore induce lower heat island intensities than conventional wall constructions. Some findings of the numerical investigations are corroborated with available nocturnal cooling field observations.