THE USE OF NOAA AVHRR DATA FOR ASSESSMENT OF THE URBAN HEAT-ISLAND EFFECT

A vegetation index and a radiative surface temperature were derived fr om satellite data acquired at approximately 1330 LST for each of 37 ci ties and for their respective nearby rural regions from 28 June throug h 8 August 1991. Urban-rural differences for the vegetation index and the surface temperatures were computed and then compared to observed u rban-rural differences in minimum air temperatures. The purpose of the se comparisons was to evaluate the use of satellite data to assess the influence of the urban environment on observed minimum air temperatur es (the urban heat island effect). The temporal consistency of the dat a, from daily data to weekly, biweekly, and monthly intervals, was als o evaluated. The satellite-derived normalized difference (ND) vegetati on-index data, sampled over urban and rural regions composed of a vari ety of land surface environments, were linearly related to the differe nce in observed urban and rural minimum temperatures. The relationship between the ND index and observed differences in minimum temperature was improved when analyses were restricted by elevation differences be tween the sample locations and when biweekly or monthly intervals were utilized. The difference in the ND index between urban and rural regi ons appears to be an indicator of the difference in surface properties (evaporation and heat storage capacity) between the two environments that are responsible for differences in urban and rural minimum temper atures. The urban and rural differences in the ND index explain a grea ter amount of the variation observed in minimum temperature difference s than past analyses that utilized urban population data. The use of s atellite data may contribute to a globally consistent method for analy sis of urban heat island bias.