Thursday 18 January 2018

Urban Heat Island



  causes , solutions ,pdf , mitigation ,ppt ,case study , upsc , urban heatland wikipedia

What is Urban Heat Island ?
                
The Urban Heat Island is an urban area that is significantly warmer than its surroundings rural area due ti its Human activities. This effect is known as urban heat island effect.




Reasons for the Formation of Urban Heat Island 

  1. Concentration of heavy vehicular and industrial pollution in urban Areas.

  2. Discharge of greenhouse gases (CHG.) in substantial amounts, which trap the outgoing infrared radiations. 

  3. Tall buildings and other Infrastructure which obstruct the flow of wind is, consequently obstructing the transfer of Heat. 

  4. Lack of vegetation in urban areas which acts as heat and carbon sink. 

  5.  Majority of urban surfaces are composed of metals, glass, concrete or asphalt. These materials have high heat-retaining capacity during the day and emit this heat out during the night. 

  6. The inability of water to penetrate the above materials makes the urban landscape behave as desert landscape. 
Effects of UHIs 

  1. UHI have the potential to directly affect the health of urban  residents. UHI witness prolonged heat waves which result in  higher fatalities due to heat stroke,exhaustion heatcramps, etc. 

  2. UHI have varied effects on biodiversity. The variation In temperatures adversely affect local species and promote the invasion of alien species.

  3.  The raised temperature may elevate the temperature of local water bodies causing the aquatic animals to undergo thermal stress and shock. 

  4. The increased temperatures provide fertile breeding ground for insects, which bring a host of diseases along with them. 

  5. UHI create a spike in energy consumption duo to higher use of refrigerated air  conditionals. 

  6. UHI can alter load weather conditions arch as wind, Humidity,  and rainfall
Mitigation Strategies 

  1. The effects of UHI can he diluted to some Extend  by applying  techniques to maintain a large albedo. Larger albedo means higher  ability to reflect radiations. The buildings and ether dark Surfaces (asphalt) could be painted with a light colour or with a high reflective coating. 

  2. Green roofs (roofs with plants and vegetation) on top of buildings help lower down the temperature and compensate to some extent for the loss of vegetation. Beside green roof, roof sprinklers in reducing temperature of evaporation. 

  3. Increasing area wider natural vegetation and reclaiming waste lands to develop green belts may also help in reducing the effects of UHl.

  4. While deciding urban architecture, wind flow should be given priority. Urban architecture should be least detrimental to natural Wind flow. 


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