The influence of the built environment on the climate in different Swedish urban fabrics

Abstract: The urban heat island effect is usually disregarded when considering energy-efficient measures for the built environment. This study aims to present and analyze the effect of the urban built environment on the Swedish urban climate. This analysis is done in terms of assessing the mean urban heat island and monthly average air temperature. Different urban fabrics were studied from Goteborg and Stockholm using Goteborg weather as reference weather data. The geographical information system (QGIS) is used to generate the morphological and land coverdata of the study areas. The UWG model is used to estimate the air temperature difference between the reference data and the study areas. This difference is referred to as the UHI intensity. It is also used to perform a sensitivity analysis considering 6 urban parameters namely: site coverage ratio, average building height, façade-to-site ratio, tree coverage, grass coverage,and surface albedo. The results showed that areas with a high site coverage ratio experienced higher monthly mean UHI intensity in summer and winter. The night-time monthly mean urban heat island for sites with the highest site coverage ratio was 2.0 O C in summer and 0.35 O C in winter. The vegetation cover (trees and grass) —although it is likely due to the limitation of the representation of the shadowing effect of trees in the model —and surface albedo have the least effect on the monthly mean UHI. The influence of the average building height and façade to site ratio is moderate and depends on the shape of the urban canyon which is highly simplified in the UWG model. The future prediction of the monthly mean air temperature showed an increase of 1.1 O C forcompact sites in summer and 0.9 to 1.0 O C in open sites. In winter the average monthly airt emperature will increase by 1.8 to 2.0 O C in different urban textures. There will be an increase of 0.3 O C in mean urban heat island in summer and a 0.2 increase in winter by 2070.