Urban heat island (UHI) phenomenon has been observed in many large cities located in cold regions (e.g. Montreal in Canada) during summer. One of the well-known strategies to mitigate the temperature rise of urban areas is increasing their albedo. Roofs cover about 25% of urban areas and increasing their reflectivity would have a significant effect on the total energy budget of a city. We have studied the effect of increasing the albedo of roofs on the air and skin temperature distributions of the Greater Montreal area. We performed simulations for one day summer episode (12 July 2005) using the Weather Research and Forecasting (WRF) mesoscale model. The WRF solver (version 3.4.1) is coupled with three different urban canopy models (UCMs): slab, single-layer, and multi-layer. We used all three UCMs by increasing the roof albedo from 0.2 to 0.8 and compared the results. All models simulated a well-defined UHI over areas with high concentration of roofs. They predicted a maximum air temperature decrease of about 1 K by implementing cool roofs. The difference between the skin (surface) temperature of urban area and its surrounding was about 9 K. The maximum air temperature difference between the urban and suburban areas was about 4 K.

Ali Gholizadeh Touchaei & Hashem Akbari (2013) The climate effects of
increasing the albedo of roofs in a cold region†, Advances in Building Energy Research, 7:2, 186-191,
DOI: 10.1080/17512549.2013.865558