Thermal effects of artificial heat sources and shaded ground areas in the urban canopy layer

The analytical cluster thermal time constant (CTTC) model, developed earlier by the authors, is used to simulate the effects of urban artificial heat release and increased shaded ground-layer areas on the urban canopy layer (UCL) climate. Hourly mean artificial heat addition of 55 W m−2, caused by transportation and electric use, is considered here as the anthropogenic energetic input to the urban atmosphere in summer. In an urban cluster composed of repeated similar street canyons oriented east-west with an aspect ratio (H/W, buildings' height to street width ratio) of 0.5, this heat addition rate causes a diurnal air temperature increase of 1–2.5 K peaking at 20:00. In summer, increasing the partially shaded ground area by adequate urban and building planning strategies can result in an appreciable temperature decrease at midday, provided that the mean sky view factor of the locality remains as high as possible.