Urban heat island

Urban Heat Island

An urban heat island (UHI) is a metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually more pronounced at night than during the day, and is most apparent when winds are weak. The main cause of the urban heat island effect is the modification of land surfaces. Waste heat generated by energy usage is a secondary contributor.

Causes

The primary cause of urban heat islands is the replacement of natural land cover with dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat. These surfaces, such as asphalt and concrete, have a lower albedo and higher heat capacity than natural surfaces, leading to increased temperatures. Additionally, the lack of vegetation reduces the natural cooling effects of shading and evapotranspiration.

Effects

Urban heat islands can have several effects on the environment and human health. They can increase energy consumption, elevate emissions of air pollutants and greenhouse gases, and impair water quality. The increased temperatures can also exacerbate heat-related illnesses and mortality, particularly during heatwaves.

Mitigation

Several strategies can be employed to mitigate the effects of urban heat islands. These include increasing vegetation through green roofs and urban forestry, using reflective or "cool" roofing materials, and implementing cool pavements. Urban planning and design can also play a role in reducing heat islands by incorporating more green spaces and improving the layout of buildings to enhance airflow.

Related Pages

• Climate change
• Global warming
• Sustainable urban planning

References

• Oke, T. R. (1982). "The energetic basis of the urban heat island." Quarterly Journal of the Royal Meteorological Society, 108(455), 1-24.
• United States Environmental Protection Agency. "Heat Island Effect." Retrieved from [1]

Gallery

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  Aerial view of Milan, illustrating urban density.
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  Central Park in New York City, a green space mitigating UHI.
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  Diagram illustrating the urban heat island effect.
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  Heat island effect in the Kanto region.
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  Variation of urban heat island intensity.
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  Manhattan's skyline, a classic example of urban heat island.
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  Thermal image of New York City showing heat distribution.
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  Dubai skyline, another example of urban heat island.
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  Thermal image of Atlanta, Georgia.
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  NASA image showing urban heat island effect on roofs.
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  Green roof on Chicago City Hall.
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  Public transport in Budapest, reducing urban heat.

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