Urban heat islands in India "EMPOWER IAS"

In news:

• There was a study that was conducted by IIT Kharagpur called “Anthropogenic forcing exacerbating the urban heat islands in India”. According to the study, the urban areas are comparatively warmer than the suburbs.

 

Key highlights of the study:

• The research was a detailed and careful analysis of urban heat islands in India.
• It studied the difference between urban and surrounding rural land surface temperatures, across all seasons in 44 major cities from 2001 to 2017.
• The study found evidence of mean daytime temperature of surface Urban Heat Island (UHI Intensity) going up to 2 degrees C for most cities, as analyzed from satellite temperature measurements in monsoon and post-monsoon periods.
• Researchers also noticed a similar rise in daytime temperatures in Delhi, Mumbai, Bengaluru, Hyderabad and Chennai.

 

Urban Heat Island effect :

• Urban Heat Island (UHI) refers to the phenomenon which causes an increase in air and surface temperature of the urban areas in comparison to their rural  counterparts
• Usually urban heat islands have a mean temperature 8 to 10 degrees more than the surrounding rural area.
• These can affect communities by increasing summertime peak energy demand, air conditioning costs, air pollution and greenhouse gas emissions, heat-related illness and mortality.

 

Causes of Urban Heat Island effect

• Natural vegetation replaced by impervious surfaces like concrete, asphalt, roof tops and building walls.
• Certain weather conditions such as clear skies and calm winds can foster urban heat island formation
• Use of construction materials like Asphalt and concrete: Asphalt and concrete, needed for the expansion of cities, absorb huge amounts of heat, increasing the mean surface temperatures of urban areas.
• Dark surfaces: Many buildings found in urban areas have dark surfaces, thereby decreasing albedo and increased absorption of heat.
• Air conditioning: Buildings with dark surfaces heat up more rapidly and require more cooling from air conditioning, which requires more energy from power plants, which causes more pollution. Also air conditioners exchange heat with atmospheric air, causing further local heating. Thus there is a cascade effect that contributes to the expansion of urban heat islands.
• Urban Architecture: Tall buildings, and often, accompanying narrow streets, hinder the circulation of air, reduce the wind speed, and thus reduce any natural cooling effects. This is called the Urban Canyon Effect.
• Need for mass transportation system: Transportation systems and the unimpeded use of fossil fuels also add warmth to urban areas.
• Lack of Trees and green areas: which impedes evapotranspiration, shade and removal of carbon dioxide, all the processes that help to cool the surrounding air.

 

Strategies that can be adopted to reduce the same are:

• Growing trees and vegetation in urban areas
• Modern green roofs and walls
• Use of solar reflective “cool” pavements for roads
• Replacing the diesel vehicles with electric or hybrid vehicles
• Using energy-efficient appliances
• Cool roofing to control temperature of building
• Conservation of water bodies in and around cities could be an effective strategy.
• The construction of buildings and infrastructure with eco-friendly materials could also prove to be crucial to mitigating the effects of heat islands.