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Delhi-NCR pollution is even worse today: Reasons why AQI is ‘severe’, and when relief is likely
Central board said Delhi's overall AQI stood at 460 at 8 am on Dec 14; this air quality is primarily attributed to weather patterns, “very low wind speed”
Delhi and the National Capital Region (NCR) are seeing another day under a severe blanket of hazardous air quality on Sunday, December 14, following a dramatic spike in pollution levels throughout Saturday.
The morning readings on Sunday said several areas across Delhi were in ‘severe’ Air Quality Index (AQI) bracket with readings well over 400. According to the Central Pollution Control Board's data, Delhi's overall AQI, as of 7 am on December 14, stood at 461, thus close to the ceiling of the ‘severe’ category (up to 500). This was worse than Saturday. The reading improved by one point to 460 by 8 am.
Forecasts had indicated the AQI may stay firmly in the "severe" category, with only slight relief anticipated from Monday onwards.
Conditions remained unfavourable for the dispersion of pollutants, with calm winds and moderate fog persisting. The India Meteorological Department (IMD) had issued an alert for dense fog in the city on Sunday morning. The lowest visibility was recorded at 350 metres at Palam airport and 200 metres at Safdarjung, the IMD said.
The pollution board classifies air quality as “moderate” when the AQI is between 101 and 200, “poor” between 201 and 300, and “very poor” between 301 and 400. Beyond 400, air quality is termed “severe”. For the purpose of mitigation measures, 450 and above is termed “severe plus”, with CPCB values not going beyond 500 — a threshold already considered seriously dangerous by the agency.
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Why is Delhi-NCR witnessing such pollution?
The persistent "severe" air quality is primarily attributed to weather patterns, specifically a Western Disturbance that has caused “very low wind speed” since Friday, HT has reported.
According to Mahesh Palawat, vice president at Skymet, this low wind speed has led to a major spike in pollution levels, and due to the western disturbance, "the AQI might remain in this range on Sunday as well".
Also read | Delhi schools to move to hybrid mode for students up to Classes 9, 11 as GRAP 4 kicks in
Experts blame the city's basin-like topography, combined with the winter setting in, for the worsening situation. Such a topography means a the city is located in a depression or dip, with higher elevations along its perimeter and lower at the centre. Such a shape means cold air is trapped beneath warm air, holding on to pollutants. Pollutants thus stay much closer to the ground in colder months, which is made worse by a lack of rain and slow wind.
The pollutants are produced by local emissions, such as construction dust and vehicles; and winter's meteorological factors multiply the impact, says research.
“The crop burning season is now nearly over. Official data shows crop burning incidence has reduced substantially in Punjab and Haryana this year,” noted research by the Centre for Science and Environment.
“What’s more worrying is the daily synchronised rise of PM2.5 and other toxic gases such as nitrogen dioxide (NO2) and carbon monoxide (CO), largely from vehicles and combustion sources, creating a toxic cocktail," Anumita Roychowdhury, executive director, research and advocacy, CSE, elaborated.
"This signals urgent need for deep rooted shifts in infrastructure and systems to upscale action to cut emissions from vehicles, industry, power plants, waste, construction and household energy,” she added.
Deterioration prompts immediate curbs
The air quality deterioration on Saturday was swift, marking the fourth "severe" day of the year for the national capital.
The 24-hour average AQI at 4 pm on Friday was 349 ("very poor"); this figure worsened by over 80 points in 24 hours to settle at 431 at 4 pm on Saturday, according to Central Pollution Control Board (CPCB) data. Readings throughout Saturday confirmed the alarming trend — the AQI was recorded at 401 at 11 am, worsening to 416 by 2 pm, and hitting 457 ("severe"-plus) by 10 pm.
Also read | Noida AQI ‘severe'-plus as air quality plummets in Delhi-NCR
In response to this sharp decline, and unlike previous episodes, mitigative measures were announced with a sense of urgency. The Commission for Air Quality Management (CAQM) invoked Stage 3 curbs under the Graded Response Action Plan, which meant more emergency measures came in on Saturday morning after the AQI neared the 400-mark. This was quickly upgraded to Stage 4 by the evening after the CPCB released its 4 pm bulletin showing the average AQI at 431.
This marks the first time this season that Stage 4 curbs, which represent the "severe plus" air quality category, have been implemented this season in Delhi-NCR.
Forecast for pollution in Delhi, surroundings
The Air Quality Early Warning System for Delhi (AQEWS) had suggested the AQI was expected to remain "severe" on Sunday.
Weather experts, however, foresee a slight improvement in air quality from December 15 onwards, as wind speeds are expected to increase.
However, that does not mean a major change.
The AQEWS bulletin confirmed that the air quality is "likely to be in the very poor category from Monday to Tuesday".
Further, there might be a slight increase in temperatures. On Sunday, the minimum and maximum temperatures are expected to be around 9–11°C and 23–25°C, respectively. The Capital is also expected to see partly cloudy skies and moderate fog in most places. Shallow fog on Saturday morning already reduced visibility to around 500 meters to 700 meters between 7:30 am and 8 am.
What Stage 4 GRAP restrictions mean
The escalation to GRAP Stage 4 has imposed significant restrictions across the NCR to prevent further deterioration of air quality.
The Delhi government issued orders requiring all government and private offices within the city to allow 50% of staff to work from home.All schools have been directed to conduct classes for grades up to 9, along with grade 11, in hybrid mode — physical and virtual — with immediate effect.
Transport restrictions under Stage 4 include the restriction of Delhi-registered heavy diesel vehicles that are BS-IV and below.
This action was taken quickly, contrasting with the previous "severe" spell in November where Grap 4 was not imposed, even though the AQI remained above 400 for several days.
NCR hotspots for pollution: Noida worst in India
The entire NCR is grappling with the severe pollution. On Saturday, 22 of Delhi's 39 active monitoring stations recorded an AQI above 400. In the wider NCR, Noida recorded the worst AQI reading in the country at 455 ("severe+"), closely followed by Greater Noida at 442.
The CAQM held an emergency meeting and highlighted areas needing improvement. It directed the Delhi government to better manage traffic congestion at various hotspots, control road dust, and ensure proper disposal of municipal solid waste (MSW).
The monitoring body also noted that Haryana’s districts within the NCR showed "poor performance in traffic de-congestion, road dust control, and municipal solid waste (MSW) management, particularly in Gurugram".
CAQM directed that intensified night patrolling be carried out to curb waste and biomass burning, and that enforcement be intensified through cameras at fuel stations.
The current restrictions are apparently a direct result of pressure from increased public criticism, protests, and judicial scrutiny over the previous two weeks.
