Week nine 1 May 2014 Urban Heat island

http://www.epa.gov/heatisland/

The term Urban Heat Island describes built up areas that are hotter than nearby rural areas.
In a city with more than one million people, the annual mean temprature can be 1-3 degrees celcius warmer than it's surroundings and in the evening, this can go up to 12 degrees celcius.
The heat islands cause people to use the airconditioning more often and may increse energy demand, air pollution, greenhouse gas emissions, illnesses and deaths bcause of heat and decreasing water quality.
The extreme tempratures also cause stress to the health of plants and animals.
City surfaces such as roads, paved foothpaths and buildings absorb and release energy from the sun, which leads to increasing tempratures around these surfaces. Also open land and vegetation vanishes and the permeable ground becomes impereable and dry.
The effect of urban heat islands becomes more tangible at night because urban infrastrucure will slowly relaese the heat stored at daytime and the temprature willtherefor still be high at night.
Parks, open land and bodies of water can have a cooling effect on urban heat islands.
Also, green roofs, reflective roofs and cool pavements can reduce the heat island effect.
Heat island mitigation is part of sustainability efforts and has benefits such as cleaner air, improved human health and comfort, reduced energy costs and lower greenhouse gas emissions.
http://www.epa.gov/heatisland/about/index.htm