Urban Heat Island (UHI) Effect
Context:
Urban areas trap more heat due to altered thermodynamic and aerodynamic properties, resulting in significantly higher temperatures compared to rural areas.
Relevance:
GS-03 (Environmental pollution and degradation)
Highlights:
- Rising global temperatures and frequent heatwaves exacerbate the warming effects in cities, intensifying urban heat challenges.
- The expansion of concrete structures, roads, industries, and residential areas contributes to additional urban warming.
- Urbanisation alters local heat distribution patterns, affects rainfall distribution, and exacerbates air pollution, impacting public health.
- Increased urban temperatures lead to heat-related illnesses and higher mortality rates, stressing the need for effective heat management.
- Elevated temperatures put additional stress on urban infrastructure, particularly cooling and energy systems, and contribute to the degradation of green spaces and water bodies.
- Tier-II cities in eastern India experience more urbanisation-driven warming compared to larger metros, highlighting the uneven impact across different urban areas.
Urban Heat Island?
- Urban heat island refers to local and temporary phenomena where certain city areas experience higher heat loads than surrounding regions.
- Heat Trapping in Concrete Structures: The rise in heat is primarily due to buildings and houses made of concrete, which trap heat and prevent its easy dissipation.
- Temperature Variation: The temperature difference between urban heat islands and their surroundings can range from 3 to 5 degrees Celsius.
Causes:
- Construction Activities: Increased urban construction using heat-absorbing materials like asphalt and concrete raises mean surface temperatures in cities.
- Dark Surfaces: Urban buildings often have dark surfaces that lower albedo, leading to increased heat absorption.
- Air Conditioning: The use of air conditioning in buildings with dark surfaces requires more energy and causes further local heating, creating a cascade effect that expands urban heat islands.
Solutions
- Increase Green Cover: Planting trees and increasing green areas help reduce heat load within urban regions.
- Passive Cooling: Implementing passive cooling technologies, which naturally ventilate buildings, can mitigate the urban heat island effect.
- Heat Mitigation Materials: Using appropriate construction materials, painting roofs and terraces in white or light colors, and promoting terrace plantation and kitchen gardening can help reduce heat absorption and urban temperatures.
