A day after strong surface winds improved Delhi’s air quality by more than 100 points, prompting revocation of impositions under Stage-3 of the Graded Response Action Plan (Grap) to curb pollution, the city’s air quality index (AQI) once again started slipping towards the “very poor” category. Shallow to moderate fog was also a contributing factor, which led to more than 60 flight cancellations at the Delhi airport.
The India Meteorological Department (IMD) has also issued a yellow alert for Sunday, warning people of a possible moderate to dense fog in multiple parts of the city. (RAJ K RAJ /HT PHOTO)
The India Meteorological Department (IMD) has also issued a yellow alert for Sunday, warning people of a possible moderate to dense fog in multiple parts of the city.
“A yellow alert has been issued for Sunday. Moderate fog is likely to be observed in many places of the city, with dense fog in some isolated places in the early hours of Sunday,” said an IMD official.
According to the Central Pollution Control Board’s (CPCB’s) daily bulletin, Delhi recorded an AQI of 236 at 4pm on Friday, as favourable meteorological conditions—strong surface winds of 15-20 kmph—helped clean up the air. However, an AQI of 228 at 7am on Saturday deteriorated to 235 at 8am and 244 at 11am. The 24-hour average AQI, as per the CPCB bulletin, was clocked at 267 (poor) at 4pm. By 7pm, it deteriorated to 273 and by 10pm, it was 277.
Mahesh Palawat, vice president at Skymet, said, “The wind speed was around 7-8 kmph throughout the day on Saturday, with wind conditions expected to remain the same over the next two days.”
According to forecasts by the Air Quality Early Warning System (AQEWS) for Delhi, the air quality is likely to be back in the very poor category by Sunday.
“The air quality is likely to be in the very poor category from Sunday to Tuesday. The outlook for the subsequent six days is that the air quality is likely to be in the very poor category,” said the AQEWS bulletin on Saturday evening.
The CPCB 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”.
Flights hit, fog alert issued
Officials from the Met department said that only shallow fog was seen in the morning hours of Saturday. According to airport officials, 34 arrivals and 38 departures were cancelled at the Delhi airport. The flight tracking website FlightRadar24 showed that over 500 flights were delayed.
Airport officials said the cancellations and delays were predominantly due to the impact at other airports, including several in northern India, where visibility was severely affected.
An airport official said, “Most of the cancelled flights are planned cancellations, based on weather forecasts by the IMD. While considering a flight, the weather of both the source city and destination are checked, which is why despite visibility in Delhi remaining good on Saturday, there were still a significant number of cancellations.”
Along the same lines, airlines have been posting on their social media handles, requesting passengers to check for updates.
Air India wrote on their social media account on X late on Friday night, “Poor visibility due to fog, forecast in parts of northern and southern India, including Delhi and Hyderabad, may impact flight operations across the network…..If you are flying with us tomorrow, we recommend that you check your flight status before heading to the airport and allow extra time for your commute to the airport….”
Mercury to dip
The minimum temperature on Saturday was recorded at 8 degrees Celsius (°C) , which was 1.2°C above normal and a degree lower than the day before. The Met department has forecast the minimum temperature to dip further, to around 6-8°C on Sunday.
“This is predominantly because of the cold northwesterly winds impacting the region, which are expected to continue for the next few days,” Palawat added.
The maximum on the day was logged at 17.3°C, two degrees below normal. Forecasts suggest that the maximum temperature is expected to be around 17-19°C on Sunday.
IMD officials said that clear skies are expected to persist for the next few days, under the influence of which the maximum temperature would increase and the minimum would dip further, as more heat is absorbed by the earth’s surface during the day and an adequate amount of heat is released just as easily at night.
Meanwhile, the Met department has forecast dense to very dense fog conditions to continue over north India for the next seven days, with cold day conditions likely in pockets of Uttarakhand, Uttar Pradesh, Madhya Pradesh and Rajasthan. Cold wave conditions might be observed in Punjab and Haryana in the next two days, it said.
IMD defines a “cold day” when the maximum is at least 4.5°C below normal, even as the minimum is below 10°C. This classification is upgraded to “severe” when the maximum drops 6.5°C below normal.
IMD defines a “cold wave” in a region where the minimum temperature is 4.5°C or more below the normal mark, or when it drops to 4°C or lower. Unlike typical cold waves that affect nighttime temperatures, cold day conditions pose unique public health risks by limiting solar radiation during daytime hours when people are typically outside their homes.