The impact of the urban canyon geometry in the nocturnal heat island intensity: analysis by a simplified model adapted to a GIS

Abstract

Urban geometry is one of the main factors influencing the development of urban heat islands. The study of urban geometry requires a characterization of urban canyons, which can be usually measured by the H/W ratio (a relationship between the height and the width of a street), a concept applied in a numerical model by Oke in 1981. The aim of this paper is to verify the impact of the canyon geometry on the intensity of the nocturnal urban heat islands. For this purpose, measurements of climate data and urban geometry were conducted in two Brazilian cities. The values of heat island intensity were cross-examined to those generated with the application of the original Oke's model. Therefore, this latter was calibrated and adapted to run in a GIS platform, allowing the incorporation of a geometric parameter other than the H/W ratio - the roughness length. Then, this process produced a new calculation tool, which is called THIS (Tool for Heat Island Simulation). The new model was applied to simulate some hypothetical urban scenarios representing several urban canyons types. The results showed that the urban canyons with the largest roughness reduce the nocturnal heat island intensities in relation to an urban canyon of the same H/W value, but presenting lower roughness rates instead.

Keywords:
Urban geometry; Urban canyon; Nocturnal heat island; GIS