Heat Island

“A heat island is a metropolitan area that is significantly warmer than its surrounding rural areas due to human activity. The main cause of heat islands is the replacement of natural land cover (such as trees and vegetation) with impermeable surfaces (such as concrete and asphalt), which absorb and reradiate more heat than vegetated surfaces. Heat islands can also be caused by the waste heat generated by power plants and other large industrial facilities. Heat islands are a major environmental concern because they can increase energy consumption, air pollution, and greenhouse gas emissions. Additionally, heat islands can adversely affect public health, causing heatrelated illnesses and deaths. There are several ways to mitigate the effects of heat islands, including planting trees and vegetation, installing reflective roofs and pavements, creating green space, increasing urban density, and using cool materials such as glass or metal in construction.” (TEWAI)
Akbari, H., Pomerantz, M., Taha, H. (2001). Cooling our communities: A strategy for heat island mitigation and smog reduction. Lawrence Berkeley National Laboratory, Berkeley, CA.
Energy Efficiency and Renewable Energy (EERE) (2012). Heat Island Effect. U.S. Department of Energy, Washington D.C..
Environmental Protection Agency (EPA) (2013). Heat Islands: Understanding and Reducing Urban Heat Islands. EPA 430R13-001
National Renewable Energy Laboratory (NREL) (2008). Heat Island Reduction. Golden, CO: NREL.
Rosenfeld, A.H. (1984). Urban heat islands and global warming. Science, 224(4649), 1568-1570.

“An urban heat island (UHI) is an urban or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually larger at night than during the day, and is most apparent when winds are weak. UHI is most noticeable during the summer and winter. The main cause of the UHI effect is from the modification of land surfaces. Waste heat generated by energy usage is a secondary contributor. As a population center grows, it tends to expand its area and increase its average temperature. The term heat island is also used; the term can be used to refer to any area that is relatively hotter than the surrounding, but generally refers to human-disturbed areas.

Monthly rainfall is greater downwind of cities, partially due to the UHI. Increases in heat within urban centers increases the length of growing seasons and decreases the occurrence of weak tornadoes. The UHI decreases air quality by increasing the production of pollutants such as ozone, and decreases water quality as warmer waters flow into area streams and put stress on their ecosystems.

Not all cities have a distinct urban heat island, and the heat island characteristics depend strongly on the background climate of the area in which the city is located. Mitigation of the urban heat island effect can be accomplished through the use of green roofs and the use of lighter-colored surfaces in urban areas, which reflect more sunlight and absorb less heat. Urbanization has made the effects of climate change worse in cities.” (Wikipedia)