Chennai is becoming warmer during summer with the average maximum temperature rising by one degree Celsius, according to data spanning 30 years that the Meteorological Department analysed recently.

Y.E.A. Raj, Deputy Director-General of Meteorology, Regional Meteorological Centre, Chennai, said, “The increase by one degree Celsius may seem less but is quite significant as there has been an overall rise over a period of 30 years between 1961 and 1990. This is more, compared to the previous decades.”

Rise in vehicles

Various reasons, including global warming and local heat effect in urban areas where heat retention is more are said to be contributing factors to the increase, officials of the department said. The increase in the number of vehicles in the city and air pollution has also led to local heat effect, they observed.

At present, the department is using 30 years' weather data from 1951 to 1980 to analyse weather patterns. According to this data, the average maximum temperature for April is 34 degree Celsius at Nungambakkam.

Mr. Raj said the decision to analyse the data from 1961, instead of 1951, was taken in view of the changes that the city had witnessed and the possible impact they could have on weather.

The data has been obtained from the National Data Centre, Pune.

The Regional Meteorological Centre would soon be able to use the new data to arrive at an average temperature that would be more representative of the monthly temperature.

Awaiting more details

“We are waiting for details [from the Centre in Pune] of five more weather stations in the State. We are analysing the weather data to arrive at normal temperature and rainfall for rest of the year,” Mr. Raj said.

Officials said the summer this year is also relatively hot as there has been no rainfall since last month. The maximum temperature since March has been at least two or three degree Celsius more than the monthly average.

The early onset of sea breeze tends to bring down the day temperature considerably.

According to Mr. Raj, however, rainfall in summer may not be uniform.

The season's rainfall could be realised even in one week. The month of May usually witnesses maximum rainfall of the season.

The average rainfall during May in Nungambakkam is 41 mm.

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