Urban Heat island effect
Urban heat island effect (UHI)
- The Urban Heat Island effect refers to localized areas within cities or metropolitan areas that experience significantly higher temperatures when compared to surrounding regions.
- Urban heat island is basically induced due to trapped heat between establishments made up of concrete.
Causes for UHI
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- In urban regions, a large amount of natural vegetation is replaced by buildings and roads made using heat absorbing materials such as asphalt and concrete. Thus the natural cooling effects of shading and evapotranspiration offered by trees is minimized.
- Evapotranspiration refers to loss of water in the form of water vapor from aerial parts of plants such as leaves, stems, flowers, etc.
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- Roads and rooftops of buildings have dark coloured surfaces which leads to greater absorption of solar radiation and reduced albedo.
- Albedo refers to the ability of a surface to reflect light. In general dark coloured surfaces have lower albedo (less ability to reflect light) in comparison to light or pale coloured surfaces.
- Manufacturing processes, factories, and commercial establishments in cities contribute to localized heating.
- High population density in urban areas results in increased energy use and transportation, thereby adding to increasing heat in cities.
Measures to control UHI Effect
- A green roof, or rooftop garden, is a vegetative layer grown on a rooftop. Green roofs provide shade and remove heat from the air through evapotranspiration thereby lowering temperatures.
- Encouraging the use of energy-efficient building designs, such as those with solar power, rain water harvesting structures can help reduce urban heat island effect.
- Encouraging walking, cycling, and the use of public transportation reduces vehicular emissions.
- Developing pavements with materials that have a higher resistance to heat absorption can help reduce surface temperatures in urban areas.
Why in news ?
- A recent report of the World Meteorological Organisation regards 2023 as the hottest year ever recorded. Global average temperatures in 2023 reached 1.45° C higher than pre-industrial levels.
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