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‘Heat island effect’ leading to high temperatures in city
AJIT PATOWARY

 
 GUWAHATI, June 13 - Why do urban areas like Guwahati face high temperatures in summer? Noted climate expert Prof Bhupendra Nath Goswami attributes such situations to unplanned rapid urbanisation. The densely populated urban areas are facing the heat island effect, he said, advocating steps to plan urban development and preserve the available greenery.Elaborating, Prof Goswami, a former Director of the Indian Institute of Tropical Meteorology (IITM) and a recipient of one of the country’s highest science awards – the Shanti Swarup Bhatnagar Award for Science and Technology – for his contributions to earth, atmosphere, ocean and planetary sciences, said paved areas in the urban areas are increasing. The surrounding humid air of the concrete structures captures the long-wave heat radiations from theses structures. If humidity is higher in the atmosphere, this process gets enhanced.

There is no free space for circulation of air in cities like Guwahati. This shoots up the ambient air temperature. Rise in the ambient temperature is basically the heat island effect in densely populated urban areas.

In this respect, though global warming has a role, unplanned rapid urbanisation is playing the major role. This calls for strict measures for urban planning to ensure enough circulation of air, said the climate expert.

On the factor effecting rise in humidity, he said humidity is increasing because of higher temperature and in its turn too, humidity is leading to the rise in environmental temperature again.

The National Geographic Society has described urban heat island (UHI) as a metropolitan area that is a lot warmer than its surrounding rural areas. Heat is created by energy from all the people, cars, buses and trains in big cities like New York, Paris and London. Urban heat islands are created in areas that have lots of people and lots of activities.

There are many reasons for UHIs. When houses, shops and industrial buildings are constructed close together, it can create a UHI. Building materials are usually very good at insulating, or holding in heat. This insulation makes the areas around buildings warmer.

“Waste heat” also contributes to a UHI. People and their tools, such as cars and factories, are always burning off energy, whether they are jogging, driving, or just living their day-to-day lives. The energy people burn off usually escapes in the form of heat.

When there is no more room for an urban area to expand, engineers build upward, creating skyscrapers. All these constructions lead to waste heat – the heat that escapes insulation has nowhere to go.

Night time temperatures in UHIs remain high because buildings, sidewalks, and parking lots block heat coming from the ground from rising into the cold night sky, according to the National Geographic Society.

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