Recently many parts of India are facing severe heat waves. Urban areas are places whose temperature is higher than the temperature of rural areas. This phenomenon is called “urban heat island”.
According to experts, these temperature anomalies are due to variation in temperature of highly urbanized and semi-urban areas as well as availability of open and green spaces in the surrounding areas.
Urban heat island – Today Current Affairs
Urban heat island can be defined as a local and temporary phenomenon in which some areas within a city experience higher temperatures than their surroundings.
The formation of urban heat islands is basically due to the buildings and houses of the cities made of concrete, due to which the emitted heat does not reach the atmosphere easily.
Urban heat islands are primarily driven by the accumulation of heat between installations made of concrete.
This variation in temperature can range from 3 to 5 °C.
Reasons for urban areas being hotter than rural areas : The Hindu Analysis
It has been observed that greener areas experience lower temperatures as compared to other regions.
Rural areas have relatively more green cover in the form of plantations, fields, forests and trees as compared to urban areas. This green cover plays a major role in controlling the heat in its surroundings.
Transpiration is the process that plants do to regulate temperature.
Following are the root causes of urban heat island in urban areas : The Hindu Analysis
The frequent construction of skyscrapers, roads, parking lots, sidewalks and public transport transit lines has accelerated the incidence of urban heat islands.
It is caused by black or any dark colored substance.
Cities typically have buildings constructed of glass, brick, and cement and concrete, all of which are dark materials, meaning that the material attracts and absorbs high heat.
Reason for Urban Heat Island : The Hindu Analysis
Multifold increase in construction activities: The construction and expansion of complex infrastructure of simple urban dwellings requires carbon absorbing materials like asphalt and concrete which absorb a large amount of temperature, hence increasing the surface area of urban areas. The average temperature increases.
Dark surface: The exterior surface of buildings built in urban areas is usually painted black or dark, due to which the albedo, that is, the reflection of the sun’s heat from the earth, is reduced and the absorption of heat increases. The Hindu Analysis
Air Conditioning: Air conditioning is used to control the temperature, which requires more energy for power plants, which causes more pollution. In addition air conditioners exchange heat with atmospheric air which generates heating locally. Thus it is a cascade effect that contributes to the expansion of urban heat islands.
Urban building style: High buildings and narrow roads obstruct air circulation thereby slowing the wind speed which reduces the natural cooling effect. This is called the Urban Canyon Effect.
Need for Mass Transportation System: Transportation system and large scale use of fossil fuels increase the temperature in urban areas.
Reduction of trees and green areas: Trees and green areas reduce the process of evaporation and carbon dioxide emissions and all these processes help in reducing the temperature of the surrounding air.
Measures to reduce urban heat islands : The Hindu Analysis
Increasing the area under green cover: Tree plantation and efforts to increase the area under green cover is the primary requirement for mitigating high heat conditions in urban areas.
‘Passive cooling’ to reduce urban heat islands: Passive cooling technology, a widely used strategy to create naturally ventilated buildings, could be an important alternative for residential and commercial buildings.
The IPCC report makes reference to ancient Indian building designs, which can be adapted to modern facilities in the context of global warming.
Other methods of heat quenching include using suitable building materials.
Roofs should be painted white or light colors to reflect heat and reduce absorption.
Terrace plantation and kitchen gardening should be promoted.
NASA’s analysis of India’s urban heat island : The Hindu Analysis
According to NASA, urban heat islands are happening more in urban parts of Delhi.
The temperature of urban areas is much higher than the agricultural areas around Delhi.
Images taken by NASA’s Ecosystem Spaceborne Thermal Radiometer Experiment (ECOSTRESS) have revealed massive red spots in the Delhi region, as well as smaller red spots around neighboring cities such as Sonepat, Panipat, Jind and Bhiwani.
Echostress is a radiometer-equipped instrument that was sent by NASA to the International Space Station in 2018.
Ecostress mainly works to assess the temperature of plants as well as to know their water requirements and the effect of climate on them.
These red spots in ECOSTRESS data indicate higher temperatures in urban heat islands, while lower temperatures in rural areas around cities.
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