THE USE OF A VEGETATION INDEX FOR ASSESSMENT OF THE URBAN HEAT-ISLANDEFFECT

A vegetation index and radiative surface temperature were derived from NOAA-11 Advanced Very High Resolution Radiometer (AVHRR) data for the Seattle, WA region from 28 June through 4 July 1991. The vegetation i ndex and surface temperature values were computed for locations of wea ther observation stations within the region and compared to observed m inimum air temperatures. These comparisons were used to evaluate the u se of AVHRR data to assess the influence of the urban environment on o bserved minimum air temperatures (the urban heat island effect). AVHRR derived normalized difference vegetation index (NDVI) and radiant sur face temperature data from a one week composite product were both rela ted significantly to observed minimum temperatures, however, the veget ation index accounted for a greater amount of the spatial variation ob served in mean minimum temperatures. The difference in the NDVI betwee n urban and rural regions appears to be an indicator of the difference in surface properties (i.e., evaporation and heat storage capacity) b etween the two environments that are responsible for differences in ur ban and rural minimum temperatures.