Answer: 

Introduction:

The Urban Heat Island [UHI] effect refers to the observable occurrence of markedly higher temperatures in urban regions relative to adjacent rural areas, primarily as a result of human activities. Typically, the mean temperature in urban heat islands can be 8 to 10 degrees Celsius higher than in the surrounding rural zones.

Body:

Causes of Urban Heat Island effect:

• Heat-absorbing surfaces: Urban areas have a higher percentage of heat-absorbing surfaces, such as concrete and asphalt, which absorb and retain heat during the day and release it at night, leading to a warmer environment. E.g In downtown areas Phoenix, Arizona, and Las Vegas, Nevada, the prevalence of concrete and asphalt results in temperatures that can be up to 10 degrees Fahrenheit (5.6 degrees Celsius) warmer than surrounding rural areas.
• Reduced vegetation: Urban areas have fewer trees and vegetation compared to rural areas, which results in less shade and reduced cooling effects through evapotranspiration. E.g The lack of trees and green spaces in urban areas like New York City’s concrete jungle can result in temperatures up to 7 degrees Fahrenheit (3.9 degrees Celsius) warmer than surrounding suburban or rural areas.
• Human activities: The use of air conditioning, industrial activities, and transportation in urban areas, generates heat and contributes to the overall increase in temperature. E.g Los Angeles, California, the use of air conditioning, industrial activities, and transportation contributes to the urban heat island effect, with downtown areas reaching temperatures 5-10 degrees Fahrenheit (2.8-5.6 degrees Celsius) warmer than surrounding areas.
• Urban geometry: The compact, dense, and high-rise buildings in urban areas create an urban canyon effect that traps heat, reduces air circulation, and increases temperature. E.g Tokyo, Japan, the compact and high-rise buildings can create an urban canyon effect that traps heat and reduces air circulation, leading to temperatures up to 14 degrees Fahrenheit (7.8 degrees Celsius) warmer than surrounding rural areas.
• Climate change: Urban Heat Island effect is expected to worsen with climate change due to the rising global temperatures, which can further exacerbate the heat island effect. E.g Phoenix, Arizona, projected to see increases in the number of days with temperatures over 110 degrees Fahrenheit (43 degrees Celsius) due to rising global temperatures.

Conclusion:

UHI can cause various environmental and health issues and its causes include anthropogenic heat, changes in land use, and lack of vegetation. Mitigating UHI can be achieved through strategies such as green infrastructure and urban planning.

DOWNLOAD PDF