What is the Urban Heat Island Effect An Urban Heat Island (UHI) is an Urban area that is significantly warmer than the area surrounding it. “According to the EPA “The annual mean air temperature of a city with 1 million people or more can be 1.8–5.4°F (1–3°C) warmer than its surroundings. In the evening, the difference can be as high as 22°F (12°C)” (6) What causes an Urban Heat Island? Building a city requires the development of buildings, roads and other structures where there once was fields, grass and woody plants. The reflection from the sun’s heat on these surfaces raises the air temperature. Heat can also get trapped between buildings and waste heat from air conditioners and vehicles increase the problem. The warmer temperatures will lower the relative humidity. Tall buildings will also change the wind pattern, often acting as obstacles and slowing the wind down. Haze caused by greenhouse gas emissions (CO2, CH4, NO) can hover over a city establishing a miniature greenhouse and preventing radiation from escaping into the atmosphere. In some areas it may also cause ground level ozone. Often there is little difference between day and night temperatures because of the insulating environment created by the buildings and the lack of wind. Water runoff from impermeable surfaces decreases the evaporation rate and increases temperature. Soil evaporation and transpiration from trees both create a natural cooling effect. The less trees and soil there is the less cooling there is. What are the effects of an Urban Heat Island ? Water sitting on warm surfaces and then draining into storm drains will increase the temperature of the rivers and streams affecting the aquatic species that live there. This may cause an increase in some species and a decrease in others creating an imbalance in the natural selection. The extra heat in the city can reduce the availability of water, food and shelter for some animals. Other animals may be attracted to the extra heat of the city. Insects that rely on heat to control their body temperature may be more prevalent in the cities than surrounding areas. Heat related human illnesses and mortality and even general discomfort increase as the temperature in a city increases The cost of energy due to the increase in the use of air conditioners increases as temperature rises. Surface temperature inversions acts as a lid trapping smog from vehicles, and other pollutants from being released into the upper atmosphere. How can we reduce the heat island effects? Planting more trees and vegetation can reduce energy costs by 10-20% (4) The use of light coloured surfaces like roads and roofs help to reflect heat rather than absorb it like the typical black surfaces. Green roofs help to cool buildings resulting in more comfortable conditions for employees The use of permeable pavers results in water infiltrating through the hard scape surface rather than running off into the storm drains. This infiltration helps increases ground water supply. Green Parking Lots is a term used for Parking Lots that use permeable pavement. To sum it all up : To combat the effects of the Heat Island Effect create “Cool streets, cool roofs, and a robust urban tree canopy” (7) fastcompany.com Interesting Fact: The City of Melbourne Australia plans to plant 3 million trees by 2040 (8) https://docs.google.com/document/d/1RCE-zwn-cTbk9uGQtH4yWx5S7V77X-YsiLaytUSlV8o/edit May 23, 2019 2. https://scied.ucar.edu/longcontent/urban-heat-islands May 27,2019 3. https://www.thoughtco.com/urban-heat-island-1435804 May 27, 2019 4. https://climatekids.nasa.gov/heat-islands/ retrieved May 27,2019 5. https://www.conserve-energy-future.com/effects-solutions-urban-heat-island.php May 27,2019 6. www.epa.gov/heat-islands 7..https://www.fastcompany.com/90379081/cities-are-getting-hotter-but-we-can-redesign-them-to-keep-us-cool Sept 18,2019 8. https://www.greenroofs.com/2019/07/23/cities-are-getting-hotter-but-we-can-redesign-them-to-keep-us-cool/