Hot spots and cold zones: how weather differs within Chennai

Rapid urbanisation, congestion, more buildings and increasing commercial activity in certain pockets of the city, has led to higher temperature levels.

September 12, 2012 03:19 am | Updated June 28, 2016 02:35 am IST - CHENNAI

Next time you complain about the heat, you may want to check which part of the city you are in. There is more to the soaring mercury levels than just meteorological factors.

Rapid urbanisation, congestion, more buildings and increasing commercial activity in certain pockets of the city, has led to higher temperature levels. People who live in parts of central and north Chennai experience the heat more than those residing in suburbs with green cover.

With mushrooming of high-rises in central and north Chennai, these parts are congested, and the temperature shoots up quickly here. The mercury level in these “urban heat islands” is at least three or four degrees above the city’s average day temperature.

These were the findings of a recent study on urban heat islands by the Centre for Climate Change and Adaptation Research Centre, Anna University, with support from former officials of the Regional Meteorological Centre (RMC), Chennai.

‘Heat pockets’ are those parts of the city that block surface heat from radiating to the sky. Aminjikarai, Medavakkam, Perungudi, T. Nagar and Ennore are some of the city’s heat pockets.

In Washermenpet and Anna Salai, increasing commercial activity and almost no open space has led to a rise in temperature levels in the range of 32.5 degree Celsius and 34.5 degree Celsius in the early morning hours. In other localities such as Ennore, George Town and Manali, waste energy generation from automobiles, air conditioning and industries have turned them into heat islands that are hotter than their surrounding areas.

J. Anushiya, who led the 12-member team in Anna University, said: “We chose to study six routes for three hours in the morning (from 4 a.m.) and in the afternoon (from 1 p.m.) for a week. We covered a distance of 60 km to 100 km in each route.” The teams observed 107 sites across the city.

The month of May was chosen as it was an apt period to study the prevalence of heat pockets. The average maximum temperature for the week was between 31.5 degree Celsius and 33 degree Celsius in the morning and between 36 degree Celsius and 44 degree Celsius in the afternoon.

The teams used a whirling thermometer calibrated with instruments at the RMC, Chennai.

People living in areas including Anna Nagar, Basin Bridge, Pulianthope, Chromepet, Velachery, Kodambakkam, Porur and Nungambakkam are better off — their areas fall in the category of those with moderate temperature level. The mercury level ranged from 31.5 degree Celsius to 32.5 degree Celsius here.

Other parts of the city where the weather is pleasant include Alamathi, Adyar, Tambaram, Vandalur, the Raj Bhavan area and Avadi, thanks to green cover — these are the city’s ‘cool islands’. Their temperature levels ranged from 29.5 degree Celsius to 31.5 degree Celsius. Areas with dense vegetation were found to be four degree Celsius cooler.

According to meteorological department officials and the Anna University’s survey team, heat generated by energy usage and poor land use distribution has led to the disparity in temperature levels.

More lung spaces in the city, stringent land use management and monitoring of green house gases emission could help mitigate the effects of climate change. Residents could use light-coloured roofs and surfaces in urban areas, which absorb less heat, they said.

The team now wants to carry out a survey during other seasons to study the changing weather patterns in the city.

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