Assessing causes in spatial variability in urban heat island magnitude

The urban thermal environment varies not only from its rural surrounds but also within the urban area due to intra-urban differences in land-use and surface characteristics. Vehicle based temperature traverses were used to determine spatial differences in summertime ~2m air temperature across the Portland, Oregon metropolitan area. Traverses were undertaken on seven hot days during summer 2006, with more planned for summer 2007. GIS resources were used to identify land-use and surface characteristics surrounding each of the traverse temperature measurements. A tree structured regression model was used to quantify the land-use and surface characteristics that have the greatest influence on UHI magnitude. Summer 2006 results indicate that the most important urban characteristic separating cooler from warmer regions of the metropolitan area was canopy cover. Warmer regions of the city were associated with industrial and commercial land-use and along roadways. Summer 2007 traverses will extend the current results by investigating the spatial variability of UHI under different weather conditions.