Modelling reduction of urban heat load in Vienna by modifying surface properties of roofs

• Published in: Theoretical and applied climatology 2018-02, Vol.131 (3-4), p.1005-1018
• Main Authors: Žuvela-Aloise, Maja, Andre, Konrad, Schwaiger, Hannes, Bird, David Neil, Gallaun, Heinz
• Format: Article
• Language: English
• Subjects: Albedo; Albedo (solar); Analysis; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Climate science; Climatology; Computer simulation; Cooling; Cooling effects; Earth and Environmental Science; Earth Sciences; Green buildings; Green roofs; Greening; Heat; Imagery; Industrial areas; Land use; Modelling; Original Paper; Orography; Reduction; Reflectance; Remote sensing; Roofing; Roofs; Satellite imagery; Satellite observation; Satellites; Spaceborne remote sensing; Summer temperatures; Surface properties; Sustainable design; Urban climatology; Urban heat islands; Waste Water Technology; Water Management; Water Pollution Control; Yields
• ISSN: 0177-798X; 1434-4483
• DOI: 10.1007/s00704-016-2024-2

The study examines the potential of urban roofs to reduce the urban heat island (UHI) effect by changing their reflectivity and implementing vegetation (green roofs) using the example of the City of Vienna. The urban modelling simulations are performed based on high-resolution orography and land use data, climatological observations, surface albedo values from satellite imagery and registry of the green roof potential in Vienna. The modelling results show that a moderate increase in reflectivity of roofs (up to 0.45) reduces the mean summer temperatures in the densely built-up environment by approximately 0.25 °C. Applying high reflectivity materials (roof albedo up to 0.7) leads to average cooling in densely built-up area of approximately 0.5 °C. The green roofs yield a heat load reduction in similar order of magnitude as the high reflectivity materials. However, only 45 % of roof area in Vienna is suitable for greening and the green roof potential mostly applies to industrial areas in city outskirts and is therefore not sufficient for substantial reduction of the UHI effect, particularly in the city centre which has the highest heat load. The strongest cooling effect can be achieved by combining the green roofs with high reflectivity materials. In this case, using 50 or 100 % of the green roof potential and applying high reflectivity materials on the remaining surfaces have a similar cooling effect.