Chennai experienced haze and smog in many parts till late in the afternoon on Monday, causing concern among residents.
As the debate about whether it was caused by pollution moving in from north India raged on social media, officials flat out dismissed the possibility but some of the city’s popular weather bloggers said it could not be ruled out. For most of the day, social media was abuzz with messages on polluted air from north India being pushed south. The Meteorological Department said the haze over the city was due to local pollution and had no connection with the pollution in Delhi.
N. Puviarasan, Director, Area Cyclone Warning Centre, Chennai, said polluted air travelling for such a long distance was not possible. Surface-level air could not travel such distances, he said, adding that it was purely a local phenomenon in Chennai as interior parts of the State had not experienced such haze.
High humidity
Chennai had high humidity levels on Monday — up to 95% — and the high moisture content in the air absorbed the carbon particles and caused the haze. Hazy skies were more prevalent near and over waterbodies and localities close to the sea, where moisture content is usually high. As there was not enough wind circulation on Monday, the moist air from the sea mixed with the automobile and industrial pollutants and led to smog.
The polluted air from Delhi moved into the Bay of Bengal and blew across Chennai as light, northeasterly winds, Mr. Puviarasan added. Tamil Nadu Pollution Control Board officials too took the line that the haze was a local phenomenon. “There was no sea breeze on Monday to disperse the PM2.5, which was the main pollutant. Similarly, wind speed was also very low,” an official said.
Former TNPCB member secretary K. Karthikeyan said pollution levels had come down before Deepavali since there was some rain. “There has been no rain for the past few days. That could have helped wash away the pollutants in the air. Every year, during the break in the monsoon and when there are no winds, pollution levels shoot up due to lack of dispersal,” he said. The city’s Air Quality Index at 4 p.m. stood at 262, which denotes poor air quality, causing breathing discomfort to most people on prolonged exposure.
The Central Pollution Control Board’s air quality monitoring stations at Manali recorded a maximum PM2.5 of 334 micrograms/cubic metre. Velachery recorded 321 micrograms/cubic metre and Alandur 317 micrograms/cubic metre. Levels of sulphur dioxide and nitrogen oxides too shot up. Weather bloggers noted that Chennai may continue to experience hazy skies for four or five days till rainfall resumes. Differing from IMD, they said, polluted air from north India drifted to the east coast.
K. Srikanth, blogger with Chennaiyil Oru Mazhaikalam, said usually, easterly and northeasterly winds prevailed during the monsoon. But now, it was unusual for northerly-northeasterly winds to prevail around this time of the year. The almost northerly winds brought dust particles from north India. The clockwise wind circulation pushed the polluted air from north to south India through Bihar and Odisha.
On the weather front, Chennai has to wait for three or four days for rains to resume. The depression that is likely to form in two days may not have much impact over the State except for isolated rains, particularly in south Tamil Nadu till Thursday. Such breaks during northeast monsoon are normal, according to officials of the Meteorological Department.
