Source : INDIA TODAY NEWS
Delhi’s air quality follows a worrying daily pattern: pollution builds through the night, peaks in the early morning and begins easing as the day progresses.
Data from October 18-20, 2026, shows how changing atmospheric conditions can turn the same city’s air significantly dirtier within hours.
Historical air-quality graphs for New Delhi show the US AQI rising from around 125-130 during the afternoon of October 18 to a peak of 191 at 7:31 am on October 19. The following morning, readings again climbed above 200, reaching approximately 210-215 in the displayed hourly data before falling later in the day.
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The pattern highlights a key factor behind Delhi-NCR’s seasonal pollution crisis: it is not just how much pollution the region produces, but how efficiently the atmosphere can disperse it.
COOLER NIGHTS TRAP POLLUTANTS NEAR THE GROUND
One major reason for the early-morning deterioration is temperature inversion. Under normal conditions, warmer air near the ground can rise and mix with the air above, helping disperse pollutants.
During an inversion, a layer of warmer air sits above cooler air near the surface, restricting this vertical movement.
As nights become cooler in October, the atmosphere can become more stable, particularly during calm conditions. Pollutants released by vehicles, industries, waste burning and other sources then accumulate closer to the ground, where people breathe.
WEAK WINDS WORSEN THE POLLUTION BUILD-UP
Low wind speeds compound the problem. When winds are weak, pollutants cannot disperse efficiently, allowing concentrations to rise overnight.
Delhi’s Air Quality Early Warning System identifies wind speeds below 10 kmph, alongside a low ventilation index, as unfavourable for pollution dispersion.
As sunlight heats the ground after sunrise, atmospheric mixing can gradually strengthen, allowing pollutants to spread through a deeper layer of air. This can bring surface pollution levels down, although the improvement depends on wind, sunlight and fresh emissions.
POLLUTION DOES NOT DISAPPEAR DURING THE DAY
Traffic, road dust, construction, industrial activity and regional emissions continue to feed the pollution load.
Smoke from agricultural residue burning can also contribute when winds transport it towards Delhi-NCR. Research published in npj Clean Air in April 2026 found that regional, multi-sector emission controls are more effective than measures restricted to Delhi-NCR alone.
The 30-day PM2.5 graph adds another warning: concentrations remained above the World Health Organisation’s recommended daily guideline of 15 micrograms per cubic metre on all 30 days shown.
The takeaway is clear: the morning pollution spike is not necessarily evidence of a sudden surge in emissions. It can reflect pollution accumulating overnight under unfavourable weather conditions.
Reducing emissions across Delhi-NCR and its surrounding airshed remains essential to prevent that daily build-up.
– Ends
SOURCE :- TIMES OF INDIA
