Sky view factor calculations and its application in urban heat island studies

• Published in: Urban climate 2019-12, Vol.30, p.100498, Article 100498
• Main Authors: Dirksen, M., Ronda, R.J., Theeuwes, N.E., Pagani, G.A.
• Format: Article
• Language: English
• Subjects: Netherlands; Sky view factor; UHI; Urban planning
• ISSN: 2212-0955; 2212-0955
• DOI: 10.1016/j.uclim.2019.100498

The sky view factor (SVF) is essential to describe the urban climatology at scales below 100m. This proxy for net radiation depends on the height of the obstacles in its surroundings. The SVF was calculated from a rasterized point cloud height dataset (with 6 − 10 points per m2). The resulting SVF depends on grid-resolution, search radius and number of directions. Previous research related the diurnal maximum urban heat island (UHI) of the canopy layer to the diurnal temperature range, solar irradiance, wind speed, vegetation fraction and SVF. The goal of this study is to determine the sensitivity of the SVF and the impact on the UHI. Within the Netherlands a test area of 70km2 was selected, including: urban areas, meadows and forests. There is a high sensitivity for grid-resolution. Therefore the impact of the SVFs grid resolution on the maximum UHI is explored. Results show that the fourth largest city within the Netherlands, Utrecht, has a mean diurnal maximum UHI of 3.1 °C using a 1m SVF resolution. But, with a 3m SVF resolution the UHI is on average 0.6 °C lower. This highlights the significance of a fine grid resolution which can capture houses, alleys and trees. •The urban heat island in the street canyon can be explained with a 1 m resolution sky view factor (SVF)•A coarser SVF resolution misses local spatial variations•For the SVF calculations a radius of 100 m and 16 search directions are recommended