New Delhi: The delayed withdrawal of monsoon is likely to aggravate air pollution in the National Capital Region (NCR), which is set to rise as dry weather conditions are expected over the next few days.

At present, Delhi’s overall air quality (including concentration of PM10) lies in the moderate category, primarily due to better wind speed, according to SAFAR or the System of Air Quality and Weather Forecasting and Research, a Ministry of Earth Sciences project which monitors the air quality in the metro cities in the country.

While no drastic deterioration of air quality is expected, atmospheric scientists predict that air quality would begin to deteriorate mid-week onwards.

“The monsoon should have retreated by now, but since it is delayed, it could now aggravate the air pollution," said Dr Gufran Beig, senior scientist at Indian Institute of Tropical Meteorology (IITM), Pune. “When monsoon begins to withdraw, an anti-cyclonic circulation gets formed nearly 4-5 kms above the surface of earth. This period is marked by dry weather, clear skies and very low speed of surface winds. So, whatever the particulate matter is in the air, it does not get dispersed and gets arrested in the atmosphere. The decreasing temperatures worsen it," added Beig.

Since, the monsoon’s withdrawal is expected around 10 October, dry weather would persist in northwest India leading to deterioration in air quality. The wind direction is northwesterly and will lead to transport of relatively dusty air into the region.

However, the contribution from incidents of stubble burning in Punjab and Haryana have so far been sporadic and SAFAR’s analysis shows they have not reached a magnitude where they could have any significant impact on Delhi’s air quality.

“A drastic deterioration is not expected until the middle of this week after which the temperatures are also likely to begin to go down," said Beig, “the situation could become worse with additional inputs from burning of firecrackers or stubble-burning over next few weeks."

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