Visibility plummeted to zero in parts of the national Capital as a thick layer of ‘dense’ to ‘very dense’ fog engulfed the region — the first for this winter season — combining with already high pollution levels in the region to create a toxic layer of thick smog which impacted flights and rail traffic in the early hours.
Delhi’s air quality continued to remain at alarmingly high levels on Monday morning, with it firmly in the ‘severe plus’ category.
The 24-hour rolling average AQI stood at 452 at 9am — marginally lower than a reading of 461 at 4pm on Sunday, which was December’s second worst air day ever. It was 431 on Saturday, making this the third straight severe day.
The India Meteorological Department (IMD) said visibility touched zero at Safdarjung and around 50 metres at Palam on Monday morning, with a thick layer of fog visible on satellite imagery across the northern plains.
“Visibility began to dip rapidly on Sunday night itself. It was down to 150 metres at 11:30pm and by 12:30am on Monday, had already touched zero at Safdarjung. It remained zero till 2am, only improving marginally to 100 metres at 2:30am. At Palam, we saw the lowest visibility dip to 50 metres at around 4am,” said an IMD official, stating wind speed remains low, facilitating fog formation.
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The impact meant low visibility procedures were initiated at Delhi’s Indira Gandhi international (IGI) airport at 2:30am, with over 150 flights delayed so far. This included 43 arrivals and 139 departures, according to the flight tracking website Flightradar 24.
This figure is expected to go up further, with delays to have a cascading effect into the latter half of the day.
“Due to dense fog, flight operations may experience disruptions…” said the Delhi airport in a post on X at 6:12am. A second update issued at 8:22am said the airport was still under CAT-3 operations, with flights still likely to be delayed and disrupted.
Northern Railways CPRO Himanshu Shekhar Upadhyay meanwhile said around 50 trains were delayed so far in the Delhi division alone, due to dense fog.
The IMD classifies fog as shallow between 500-1000 metres, as ‘moderate’ when visibility is between 200-500 metres, as ‘dense’ when it is between 50 and 200 metres and as ‘very dense’ below 50 metres.
On Sunday, 38 out of Delhi’s 39 active ambient air quality stations were in the ‘severe’ category, with only Shadipur in ‘very poor. At least three stations ‘maxed out’ and touched a maximum value of 500, which included Rohini, Ashok Vihar and Wazirpur.
Others like Jahangirpuri (499) and west Delhi’s Mundka (499) were close. Experts say gradual dispersion is likely in the second half of Monday as wind speeds pick up.
“We have had an easterly wind direction on Saturday and Sunday, which has brought ample moisture. At the same time, surface wind speed is low. Not only is this trapping pollutants but also leading to dense fog formation,” said Mahesh Palawat, vice President at Skymet, adding the wind direction is expected to switch to northwesterly on Monday.
“We should also see winds pick up post noon, so some dispersion may commence,” he added.