We find that ecological context significantly influences the amplitude of summer daytime UHI (urban–rural temperature difference) the largest (8 °C average) observed for cities built in biomes dominated by temperate broadleaf and mixed forest. For all cities combined, impervious surface area is the primary driver for increase in temperature explaining 70% of the total variance in land surface temperature. On a yearly average, urban areas are substantially warmer than the non-urban fringe by 2.9 °C, except for urban areas in biomes with arid and semiarid climates. The average amplitude of the UHI is remarkably asymmetric with a 4.3 °C temperature difference in summer and only 1.3 °C in winter.

Lahouri Bounoua (NASA Earth Resource Technology)

Imhoff M.L., Zhang P., Wolfe R.E., Bounoua L. Remote sensing of the urban heat island effect across biomes in the continental USA (2010) Remote Sensing of Environment, 114 (3), pp. 504-513.