Impact of urban albedo on microclimate: Computational investigation in London

Abstract

The urban albedo (UA), defined as the ratio of the reflected to the incoming shortwave radiation at the upper edge of urban canyons, quantifies their ability to reflect solar radiation towards the sky. This research investigates the impact of real-world urban geometries and optical properties of facades and roads materials on the UA and street level microclimate in London. The Indexed Sphere (IVS) algorithm of ENVI-met 4.4.4 is used to compute the UA of several canyon configurations. The accuracy of the IVS algorithm is evaluated against measurements on a 1:10 physical model reproducing the geometry and materials of the case study area. The simulation results show that reflective materials applied to the canyon surfaces are more effective in increasing the UA of canyons with low aspect ratios. The use of reflective materials in urban canyons always increases the amount of reflections at the street level, increasing the mean radiant temperature in most cases. Air temperature is not affected by the canyon’s façades reflectivity while it shows a significant daytime reduction for increased roads’ reflectivity. The results provide preliminary guidelines for the control of UA and the improvement of microclimate in London.