Why is this newsworthy?

Several sections of India have recently experienced significant heat waves. The temperatures in urban areas and cities are higher than in rural areas. “Urban Heat Island” is the name given to this phenomena.

These temperature differences, according to experts, are produced by differences in heating across highly urbanised and semi-urbanized areas, as well as the relative availability of open and green spaces in the surrounding areas.

What is the definition of an urban heat island?

An urban heat island is a localised and transient phenomena in which particular areas of a city have higher heat loads than the surrounding area.

This spike in temperature is primarily caused by concrete buildings and dwellings in cities, where heat is trapped and cannot easily evaporate.

The urban heat island is caused by trapped heat between concrete structures.

Temperature changes of 3 to 5 degrees Celsius are possible.

Why do cities have higher temperatures than rural areas?

• Greener areas were shown to have lower temperatures than non-green areas.
• Green vegetation, such as plants, trees, and forests, have an important role in reducing the occurrence of urban heat islands.
• Plantations, farmlands, woods, and trees provide more green cover in rural areas than in urban ones.
• Transpiration is a process through which plants regulate their temperature.
• The primary cause of Metropolitan Heat Island in urban areas is pollution.
• Urban heat islands have become more common as a result of the frequent building of highrise structures, roads, parking spaces, pavements, and public transportation transit lines.
• It can be found in black or any other dark-colored material.

What Causes the Heat Island Effect in Cities?

Construction activity has increased dramatically: Carbon-absorbing materials such as asphalt and concrete are required for the evolution of cities, from small urban residences to complex infrastructures. They trap a lot of heat, which raises the average surface temperature of cities.

Dark surfaces: Many buildings in urban areas have dark surfaces, which reduce albedo and increase heat absorption.

Buildings with dark surfaces heat up more quickly and require more air conditioner chilling, which consumes more energy from power plants, resulting in more pollution. Furthermore, air conditioners exchange heat with ambient air, resulting in additional local heating. As a result, the spread of urban heat islands is aided by a cascading effect.

• Tall buildings, as well as the often associated small streets, obstruct air circulation, diminish wind speed, and thus reduce any natural cooling effects. The effect is known as the Urban Canyon Effect.
• A public transit system is required: Warmth is also added to metropolitan areas by transportation infrastructure and the unrestricted use of fossil fuels.
• A lack of trees and green areas obstructs evapotranspiration, shading, and carbon dioxide removal, all of which serve to chill the surrounding air.

What can be done to reduce urban heat islands?

Plantation and efforts to increase the area under green cover are the most important requirements for reducing heat load in metropolitan settings.

Passive Cooling to Reduce Heat Islands in Cities: Passive cooling, a widely utilised approach for creating naturally ventilated buildings, can be a vital alternative for residential and commercial buildings to alleviate the urban heat island.

In the context of global warming, the IPCC report highlights ancient Indian architectural designs that utilised this technology, which may be adapted to current facilities.

• Use of proper construction materials is another form of heat reduction.
• To reflect heat and prevent absorption, roofs and terraces should be painted white or light colours.
• Kitchen gardening and terrace vegetation should be encouraged.

What has NASA said about urban heat islands in India?

Heat islands are becoming more common in Delhi’s urban areas, according to NASA.

The temperature in the city of Delhi was substantially greater than in the surrounding farmlands.

NASA’s Ecosystem Spaceborne Thermal Radiometer Experiment (Ecostress) captured the image, which shows a large red area over Delhi and smaller red patches near neighbouring cities Sonipat, Panipat, Jind, and Bhiwani.

NASA launched Ecostress, a radiometer-equipped gadget, to the International Space Station in 2018.

Ecostress is in charge of determining the temperature of plants, as well as their water requirements and the impact of the climate on them.

These red regions in the Ecostress data exhibited higher temperatures, indicating urban heat islands, whereas rural areas around cities had lower temperatures.