100 flights delayed as season’s thickest smog envelops Delhi

The fog led to visibility dipping to 50 metres at Delhi’s Indira Gandhi International Airport from 10pm on Monday till 4am Tuesday, delaying around 100 flights. Five other flights were diverted to Jaipur between 11pm and midnight on Monday, officials said.

Delhi on Tuesday witnessed this season’s most intense fog between Monday night and Tuesday morning, as parts of the haze spread from Punjab all the way across the Indo-Gangetic plain.

The first flight diversion at Delhi airport was reported at around 11.25pm on Monday.

The fog led to visibility dipping to 50 metres at Delhi’s Indira Gandhi International Airport from 10pm on Monday till 4am Tuesday, delaying around 100 flights. Five other flights were diverted to Jaipur between 11pm and midnight on Monday, officials said.

Photos: Dense fog engulfs Northwest India; Delhi also struggles with poor AQI

RK Jenamani, scientist at the India Meteorological Department (IMD), said visibility stayed low at most airports across northern India, with operations impacted at some places between 6pm on Monday to 1pm on Tuesday.

“The fog covered nearly 1 million sq km in area, covering north, central, and eastern India. As compared to the previous such spell of fog this winter, which occurred on December 27, the fog covered nearly three times more area on Monday night and Tuesday morning,” he said, adding that visibility stayed between 50 to 100 metres between 10pm on January 2 and 4am on January 3.

The first flight diversion at Delhi airport was reported at around 11.25pm on Monday, with a SpiceJet flight from Jabalpur to Delhi being diverted to Jaipur. This was followed by a flight from Dubai (P4999) being diverted around 11.35pm, A GoFirst Mumbai to Delhi flight (G8 341) was diverted at 11.36pm and two more flights – a Dubai-Delhi flight (VTVRV) and an Ahmedabad-Delhi Air India flight (AI 816) -- were diverted at around 11.45pm.

At 10.10pm, the Delhi airport tweeted that low visibility procedures were in place, and while no flights were impacted till then, asked passengers to check with the airlines for the latest flight information.

“Low visibility procedures are in progress at Delhi Airport. All flight operations are presently normal. Passengers are requested to contact the airline concerned for updated flight information,” it tweeted.

The airport initiates low visibility procedures -- aimed at making landing for flights easier-- when visibility dips below 800m. During this period, CAT-I procedures, the first level of precautions, are in place to guide pilots. Only flights and pilots that are CAT-II compliant are allowed to land when visibility is less than 550 metres, while CAT-III A pilots can land when visibility is between 175 and 300 metres. CAT-III B are the most stringent qualifications for a pilot to land a flight, allowing them to make an approach even when visibility is 50 metres.

An airport official said only CAT-III B-compliant pilots or airlines were allowed to land between 10.30pm and 4am.

While flights can still land at the airport when visibility is 50 metres, no flights are allowed to depart unless runway visibility range (RVR) is 125 metres. “This led to some arrivals and departures being delayed during this window as well,” an airport official said.

IMD classifies a fog as “shallow” when visibility dips below 1,000 metres, as “moderate” when visibility is between 200 and 500 metres and as “dense” when it is below 200 metres. It is “very dense” when visibility is below 50 metres.

The fog and cloudy skies also led to a dip in the Capital’s maximum temperature from 17.3 degrees Celsius (°C) recorded on Monday to 16.1°C -- three below the normal for this time of the year -- on Tuesday. This is the second-lowest maximum temperature recorded in Delhi during the current winter season after December 26, when Safdarjung, the city’s representative weather station, recorded 15.6°C.

The lowest maximum temperature recorded in the city was 14.7°C at southwest Delhi’s Jafarpur, and isolated parts of the Capital recorded “cold day” conditions, IMD officials said.

IMD declares a “cold wave” in a region when the minimum temperature is 4.5 degrees or more below the normal mark, or when it drops to 4°C or lower. According to the department, a “cold day” is when the maximum temperature is 4.5 degrees or more below normal, while the minimum is below 10°C.

Delhi recorded a low of 8.5°C -- one above normal and nearly a degree above Monday’s 7.6°C.

IMD forecasts Delhi’s maximum to hover around 17-18°C over the next four days, while minimum temperature is forecast to gradually dip from Wednesday, and is projected to reach 4°C by Friday.

The meteorological conditions also led to a deterioration in the city’s pollution levels, with the Capital logging an Air Quality Index (AQI) reading of 385 (very poor) as per the daily Central Pollution Control Board (CPCB) bulletin released at 4pm.

In comparison, Delhi’s average AQI reading on Monday was 357 (very poor). “The AQI is dipping due to this fog, which is originating from Punjab and Uttar Pradesh and then spreading to Delhi and across the Indo-Gangetic Plains. Moisture in the air can trap pollutants and this same fog is leading to a dip in temperature, particularly during the day,” said Gufran Beig, founder project director at Safar, a government body.