Flight, rail operations hit as dense fog blankets Delhi

Over 50 flights were delayed and 12 were diverted at Delhi's IGI airport while 20 trains were delayed. The situation is expected to continue on Wednesday.

A dense fog enveloped Delhi for a second straight morning on Tuesday, capping the visibility at just 50 metres from 5.30am to 10.30am and hampering the city’s rail and flight operations.

Fog envelops Yamuna Bank in Delhi on Tuesday morning. (Raj K Raj/HT Photo)

Weather authorities issued an “orange alert”, predicting another spell of “dense” to “very dense” fog for Wednesday, with the transit chaos that has affected Delhi every morning for two days now likely to continue.

Local pollutants mingled with the thick fog, essentially draping the city in a suit of smog, with the air quality index (AQI) in the upper-end of the “very poor” zone again.

At the Indira Gandhi International (IGI) airport on Tuesday, over 50 flights between 6am and noon were delayed, with 12 aircraft also being diverted during this period. “Eleven flights had to be diverted to Jaipur and one flight was sent to Lucknow. No diversions were reported after noon,” said an airport official.

IMD classifies a fog as “shallow” when the visibility is between 500 and 1000 metres, “moderate” when it is between 200 and 500 metres, “dense” when it is between 50 and 200 metres, and “very dense” when it is 50 metres or lower.

The situation on Tuesday was only marginally better than on Monday, when the season’s first dense fog brought visibility at IGI to zero between 5.30am and 9.30am. However, only eight flights were diverted that day.

READ | Thick fog envelopes Delhi; some flights likely to be affected

“Dense fog prevailed for around five hours, between 5.30am and 10.30am, before improving to over 200 metres by 11am, as the sun came out,” said Kuldeep Srivastava, scientist at India Meteorological Department (IMD). “We expect similar conditions on Wednesday too.”

The Northern Railways said that over 20 trains were delayed by more than one hour on Tuesday morning due to the weather. “These included the Puri-New Delhi Purushottam Express, the Gaya-New Delhi Magadh Express, the Howrah-New Delhi Poorvah Express and the Chennai-New Delhi GT Express,” said a Northern Railways official.

The effect of the fog was worsened by the pollution. Delhi clocked a 24-hour average AQI of 377, according to the Central Pollution Control Board’s (CPCB) national bulletin at 4pm. This was just a shade better than 383 at the same time on Monday.

READ | ‘Very dense’ fog blankets Delhi for 2nd day; air and rail operations disrupted

Forecasts show that the air quality is likely to return to the “severe” zone on Wednesday. The AQI was consistently “severe” between December 22 and 24.

Temperatures, however, remained largely unchanged thanks to clear skies during the day and the fog at night.

Meanwhile, the city recorded a minimum temperature of 7°C on Tuesday, which was a degree below normal. It was 7.8°C a day earlier. The maximum was recorded at 23.8°C — three notches above normal.

“We are seeing clear skies after noon, making for a warm day. At night, there is fog formation and that does not let the temperature dip sharply. In the absence of fog, temperatures dip more as heat is lost easily in the atmosphere,” Srivastava said.