Delhi air quality back to ‘severe’ today

Air quality is expected to plunge to ‘severe’ category Friday, with calm surface level winds and low temperature being ineffective in dispersal of pollutants, air and weather monitoring agencies said.

The 24-hour average air quality index (AQI) of Delhi Thursday remained in the ‘very poor’ category, but jumped by 65 points from Wednesday to reach 366 Thursday, as per the Central Pollution Control Board (CPCB).

In NCR, Ghaziabad and Noida had already touched ‘severe’ with an AQI of 416 and 402, while Gurgaon was in ‘poor’ range with 280.

As of 10 pm Thursday, five out of 35 monitoring stations in Delhi had recorded ‘severe’ air quality — meaning the air in these areas would “affect healthy people and seriously impact those with existing diseases” — while all others remained in the ‘very poor’ range.

The central government’s air quality monitoring agency SAFAR released a map of air pollution hot spots in Delhi and nearby NCR areas. These are the locations that would be impacted by higher PM2.5 concentration this week as compared to other areas.

The hotspots include areas around Shalimar Bagh, Azadpur and Jasola Vihar in Delhi, and Sahibabad, parts of Ghaziabad and Noida in Uttar Pradesh.

A report by SAFAR Thursday said, “(AQI) may touch lower end of ‘severe’ category by Friday. The main factors working towards the deterioration are the extremely low wind speed and strong near-surface inversion during the stable night time.”

An inversion is when temperature near the surface is lower than the temperature at a higher altitude.

An inversion happens due to multiple factors including windspeed and cloud cover over a region. It puts a cap on the upward movement of air. This hinders the diffusion of pollutants trapped near the surface.

An official from the IMD said surface level windspeed as calm as 5 km/h were recorded Thursday and is likely to remain the same till Friday afternoon, after which it will pick up pace and reach 15km/h by Saturday.

Light rainfall with good wind speed is also forecast on November 26.

SAFAR has also said an improvement in air quality is likely by Saturday, owing to a passing Western disturbance which would increase wind speed.

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