Effective albedo estimates for the Metropolitan Area of São Paulo using empirical sky-view factors

This paper presents a simple method to obtain urban effective albedo based on the sky-view factor (SVF) data. In the method described herein, a two-dimensional canyon is the prototype to model the urban geometry. To obtain the effective albedo for urban areas, surface albedo values of different facets (roof, wall and road) are assumed. The effective albedo changes with respect to the sky-view factor so that the starting point was to make use of a digital camera equipped with a fish-eye lens to obtain the sky-view factor for 36 sites located in the Metropolitan Area of São Paulo (MASP). To easily compute the effective canyon albedo from the local SVFs, it was assumed that the shortwave radiation in the interior of the canyon is reflected on walls and street infinitely-many times. The model was capable to reproduce the evolution of effective albedo for the center of MASP. The SVF decreases with increasing building coverage or increasing building height, enabling a higher values of the urban heat island intensity. Even not take into account the role of plan built area density or the facade density, this work could attribute a value of 0.5 based on the literature.