What is Urban heat island?
An '''urban heat island''', or UHI, is what happens when a city in [[urban area]] is warmer than the area around it. It happens because things in cities like [[concrete]] take longer to give off heat than things like trees, which are common outside of cities, because of [[urbanization]]. The urban heat island effect is stronger at night and when there is not much wind. Cities can be 3°C warmer than nearby countryside. <ref>{{cite web|url=http://www.epa.gov/heatisland/about/index.htm |title=Basic Information |publisher=EPA}}</ref> In country areas, a large part of the incoming [[solar energy]] goes to [[evaporation|evaporate]] [[water]] from [[vegetation]] and soil. But cities have less vegetation and soil. In cities, most of the sun’s energy is absorbed by urban building and asphalt paving. During warm daylight hours, there is less evaporative cooling in cities than in country areas. So, surface temperatures rise higher in cities than in country areas. Also, vehicles, factories, and industrial and domestic heating and cooling units give off more heat in cities. This problem is growing.<ref>Park, H.-S. (1987). Variations in the urban heat island intensity, affected by geographical environments. Environmental Research Center papers, no. 11. Ibaraki, Japan: Environmental Research Center, The University of Tsukuba.</ref> This effect causes the city to become 2 to 10<sup>o</sup> F (1 to 6<sup>o</sup> C) warmer than surrounding rural areas.<ref>{{cite web|url=http://www.epa.gov/heatisland |title=Heat Island Effect |publisher=U.S. Environmental Protection Agency|accessdate=2011-10-21}}</ref> ==Sources== {{reflist}} {{weather-stub}} [[Category:Urban and regional sciences]] [[Category:Heat]]