Delhi’s AQI nears ‘severe’ yet again as smog thickens amid dip in wind speed

Safdarjung, the base station for Delhi’s weather, logged a minimum temperature of 10.2°C on Tuesday, two degrees below normal.

Delhi’s air quality edged dangerously close to the ‘severe’ category on Wednesday, as the city woke up to a dense blanket of smog with the 24-hour rolling average AQI reaching 391 (very poor) at 8am, a sharp rise from 374 (very poor) recorded at 4pm on Tuesday.

People stage a protest against rising air pollution in New Delhi. (ANI)

According to air quality analysts, a dip in wind speed has led to stagnation and accumulation of pollutants, worsening conditions across the capital. A thick haze of smoke stretched across the Indo-Gangetic Plain, enveloping Delhi and merging with early-morning moisture to create a persistent layer of smog.

The Central Pollution Control Board (CPCB) classifies air as ‘good’ when the AQI is 50 or lower, as ‘satisfactory’ when it is between 51 and 100, as ‘moderate’ when it is between 101 and 200, as ‘poor’ when it is between 201 and 300, as ‘very poor’ when it is between 301 and 400 and ‘severe’ when it is over 400.

Though Monday’s marginal improvement was down to winds picking up, touching 12 km/hr during the day, they dipped on Tuesday and remained below 5 km/hr. Forecasts show that while the impact of stubble burning is likely to reduce as the wind direction predominantly stays northeasterly, low wind speeds are likely to allow pollutants to accumulate in the city.

“Delhi’s air quality is likely to be in the ‘very poor’ category from November 19 till November 21. The outlook for the subsequent six days shows the air quality is likely to remain ‘very poor’,” the Centre’s air quality Early Warning System (EWS) for Delhi said on Tuesday.

Stage-3 of the Graded Response Action Plan (Grap) is already in place in Delhi, with non-essential construction and demolition, along with private four wheelers (BS3 petrol and BS4 diesel), banned. Stage 3 came into force on November 11 when Delhi’s AQI first touched ‘severe’ this year. If the AQI continues to deteriorate, Wednesday will become the fourth ‘severe’ air day this season.

Safdarjung, the base station for Delhi’s weather, logged a minimum temperature of 10.2°C on Tuesday, two degrees below normal. It was 9.6°C on Monday. The minimum is likely to oscillate between 9°C and 11°C till Thursday as a winter chill persists, the India Meteorological Department (IMD) has forecast.

A return of easterly to northeasterly winds is likely to raise the minimum above 11°C on November 21, it added.