Dense smog leaves Delhi choking as AQI in ‘severe plus’ category, visibility down to 100m
The average AQI stood at 485 (severe), further deteriorating from Sunday’s 4 pm reading of 441, meaning the air quality had crossed the 450 threshold and touched ‘severe plus’.
Delhi’s air quality was deep in the ‘severe’ zone on Monday morning as a thick layer of smog blanketed the capital in a haze of toxic pollutants, even as Stage 4 of the Graded Response Action Plan (GRAP) came into force from 8am today.
The average air quality index (AQI) stood at 485 (severe), further deteriorating from Sunday’s 4 pm reading of 441, meaning the air quality had crossed the 450 threshold and touched ‘severe plus’. This is Delhi’s highest AQI since November 3, 2019, when the AQI reached 494, according to official data.
The average AQI was calculated on the basis of 37, all of whom were in the severe range, the Central Pollution Control Board (CPCB) data showed. While Dwarka Sector-8 Metro station had a value of 500 (the maximum CPCB’s index goes), other locations were on the brink of maxing out, including Najafgarh (499), Pusa and Major Dhyanchand stadium (497) and Ashok Vihar (495).
The CPCB classifies AQI between 0-50 as “good”, between 51 and 100 as “satisfactory”, between 101 and 200 as “moderate”, between 201 and 300 as “poor”, between 301 and 400 as “very poor”, and over 400 as “severe”.
The highest ever average AQI for the capital was 497 on November 6, 2016. However, Delhi had only 9 stations back then, as compared to 40 now.
With Delhi’s AQI rapidly deteriorating, the Commission for Air Quality Management (CAQM) invoked Stage 4 of GRAP on Sunday evening.
Stage 4 of GRAP has extreme measures to curb the rising AQI in the region, including a complete ban on construction and demolition activities, linear projects such as roads, highways, flyovers, overbridges and pipelines; a complete ban on entry of trucks into Delhi (CNG, BS VI, electric and essential allowed); ban on entry of light commercial vehicles registered outside Delhi into the capital (CNG, BS VI, electric and essential allowed). BS IV or lower medium goods and heavy goods vehicles are also not allowed in Delhi, unless they are involved in essential or emergency services.
The Delhi government also halted physical sessions for classes except 10 and 12 in all schools, and shifted them online. NCR state governments can take a similar call under Stage 4, while also exploring other measures such as making 50% government employees work from home and implementing the odd-even road rationing scheme, if required.
The lowest visibility of 100 metres was recorded in the early hours of the day, with the IMD calling it ‘dense fog’. Fog is called as ‘moderate’ when the visibility is between 200 and 500 metres. It is ‘dense’ when the visibility is between 50 and 200 and below 50 is ‘very dense’. Generally, fog is called as smog when visibility is less than 1,000 metres and humidity is less than 75%.
The IMD has been calling it fog in the early hours of the day when humidity is high, followed by smog in the second half of the day.
On Sunday, Delhi witnessed an intense smog which meant visibility did not go higher than 900 metres, thus not even allowing sunlight to penetrate through. Experts said no significant change is likely today. “Unless wind speeds pick up sufficiently, we will see a similar smog during the day, with little sunlight reaching the surface,” said Mahesh Palawat, vice president, Skymet.
Delhi’s minimum temperature was recorded at 16.1°C on Monday morning, two degrees above normal. It was 15.9°C a day earlier. The maximum on Sunday was the lowest this season at 27.2°C with a similar high expected on Monday as well.