Airborne Observations of Thermal Anisotropy from Urban Residential Neighbourhoods in Salt Lake City, Utah

Samantha J. Claessens, The University of Western Ontario

Abstract

Urban surface temperatures are important variables in urban climatological processes. This thesis examines the directional variability of remotely sensed urban surface temperatures (thermal anisotropy or Λ) for three vegetated residential neighbourhoods in Salt Lake City, Utah, USA. Airborne thermal remote sensing using a thermal imager sampled the directional brightness temperature (DBT) at three times within a day for each site. Results indicate that temporal variability over a 20 – 30-minute flight was not negligible. Average DBT were then extracted from atmospherically corrected images and plotted on polar plots. For low density residential neighbourhoods Λ is increased with increasing tree-canopy coverage (λ_tree) due to the increased temperature contrast. The Λ_Max for the sites with large λ_tree were ~8°C compared to ~6°C for the site with sparse λ_tree. These results indicate Λ for low density residential neighbourhoods is significant and must be considered when discussing land surface temperatures for similar sites.