URBAN HEAT-ISLAND

The phenomenon of an urban heat island was investigated by the use of Landsat/Thematic Mapper data sets collected over the metropolitan area of Washington, DC. By combining the derived spectral albedos and temperatures, surface energy composites of five surface categories were analysed. The results indicate that urban heating is attributable to a large excess in heat from the rapidly heating urban surfaces consisting of buildings, asphalt, bare-soil and short grasses. In summer, the symptoms of diurnal heating begin to appear by mid-morning and can be about 10-degrees-C warmer than nearby woodlands.