Urban heat island effect across biomes in the continental USA

Impervious surface area (ISA) from National Land Cover Database 2001 and land surface temperature (LST) from MODIS averaged over three annual cycles (2003-2005) are used in a spatial analysis to assess the urban heat island (UHI) signature on LST amplitude and its relationship to development intensity, size, and ecological setting for 323 urban settlements over continental USA. Development intensity zones based on fractional ISA are defined for each urban area emanating outward from the urban core to the nearby non-urban rural areas and used to stratify sampling for LST. We find that the ecological context and settlement size significantly influence the amplitude of summer daytime UHI. In desert environments, the LST´s response to ISA presents an uncharacteristic “U-shaped” horizontal gradient and points to a possible heat sink effect. For all cities combined, ISA is the primary driver for increase in temperature explaining 72% of the total variance in LST.