Residents of India's capital finally breathed a sigh of relief as a late-night wind intervention on Saturday helped clear the persistent fog and slightly improved the toxic air that had engulfed the city. The change in weather conditions prevented the air quality from remaining in the 'severe' category as initially feared.
Wind Provides Much-Needed Relief
The shift began around 11:30 pm on Saturday when easterly winds, blowing at speeds of 6 to 10 kilometres per hour, started sweeping across Delhi. These winds continued until 6:30 am on Sunday, with daytime speeds ranging between 4 and 8 kmph. This marked a significant change from the calm and stagnant conditions that had prevailed for most of Saturday, allowing pollutants and fog to accumulate.
An official explained that the increased wind speed played a dual role: it stopped the air quality from deteriorating further into the severe range and also helped disperse the thick layer of fog that had reduced visibility across the National Capital Region.
Air Quality and Visibility Trends
The impact was reflected in the air quality index (AQI) readings. After entering the severe category at 409 by 8 pm on Saturday, the city's overall AQI showed improvement, settling at 377 (very poor) by 4 pm on Sunday. Data from the Central Pollution Control Board revealed that out of 39 active monitoring stations, 13 still recorded AQI levels above 400. Ayanagar was the only station to report a 'poor' reading of 293.
Despite the improvement, flight operations at Indira Gandhi International (IGI) Airport faced major disruptions. A total of 107 flights were cancelled and 500 were delayed, primarily due to low visibility conditions at several airports across North India.
The India Meteorological Department (IMD) provided detailed visibility reports. At Palam, the lowest visibility was 300 metres between 10 pm Saturday and 12:30 am Sunday, later improving to 600 metres. Safdarjung, the city's base weather station, recorded visibility as low as 200 metres from 1:30 am to 2:30 am, which improved to 500 metres by 5:30 am. Senior IMD scientist R K Jenamani noted that visibility at IGI Airport was above 1,000 metres from 12:30 pm to 7 pm on Sunday.
Forecast and Temperature Update
The Centre's Air Quality Early Warning System for Delhi now predicts that the air quality is likely to remain in the 'very poor' band until Wednesday, a revision from earlier forecasts that anticipated 'severe' conditions on Sunday and Monday.
The IMD has issued a yellow alert (be aware) for moderate fog at most places, with dense fog likely in isolated areas during the early morning hours of Monday. From Tuesday to Thursday, the city is likely to experience moderate to shallow fog.
On the temperature front, Sunday saw a slight rise. The maximum temperature was recorded at 18.1 degrees Celsius, which is four notches below normal but higher than Saturday's 16.9 degrees. The minimum temperature was 9.4 degrees Celsius, one notch above normal. The Met department forecasts the day temperature to rise further to around 20-22 degrees Celsius on Monday, with the minimum likely to hover around 9 degrees Celsius.
Notably, the 'cold day' conditions that were forecast for isolated pockets in Delhi did not materialise on Sunday. A 'cold day' is declared when the minimum temperature is below 10 degrees Celsius and the maximum temperature departure from normal is 4.5 degrees or more.
