Dense fog shrouds Delhi, hits transit modes

Airport authorities said that over 50 flights were delayed at Delhi’s Indira Gandhi International (IGI) airport

A dense fog shrouded Delhi in the early hours of Friday slashing visibility to zero — and remaining in this zone for nearly four hours from 5am to 9am — hobbling both air and rail transit operations, weather officials said.

The dense fog also brought back pollutants, trapping them to clock a 24-hour average air quality index reading of 217 (poor). (Vipin Kumar/HT Photo)

The dense fog also brought back pollutants, trapping them to clock a 24-hour average air quality index reading of 217 (poor) at 4pm, according to the Central Pollution Control Board’s national bulletin — a 39-point deterioration from Thursday’s “moderate” reading of 178 at the same time.

Airport authorities said that over 50 flights were delayed at Delhi’s Indira Gandhi International (IGI) airport, while rail authorities said at least 20 trains were delayed by over an hour. The dense fog was recorded only a day after incessant showers cascaded through the city, exceeding February’s rain quota for the month and recording the first “moderate” air day in over three months.

Read here: Visibility down to zero in several parts of Delhi as ‘very dense’ fog engulfs city

Meanwhile, Delhi recorded a maximum temperature of 18.5 degrees Celsius (°C) on Friday, which was four degrees below normal. It was 18.6°C a day earlier. The minimum saw a sharp drop in the last 24 hours and was recorded at 7°C — a degree below normal and a 5.3-degree dip from Thursday’s 12.3°C. The maximum is forecast to hover between 18-20°C over the weekend, while Delhi’s minimum could spike to 10°C by Sunday.

The India Meteorological Department (IMD) has said that dense fog is likely on Saturday morning, with the possibility of a drizzle towards the night. A “yellow alert” for light rain has been issued for Sunday, IMD said. IMD said “very dense” fog returned to the region due to moisture intrusion from the western disturbance which brought rain to large parts of the plains over the last two days.

Delhi’s air had turned “moderate” on Thursday for the first time since October 20, 2023, when it was 195. It was Delhi’s cleanest air quality since October 19, 2023 (121).

“There is plenty of moisture in the atmosphere due to the western disturbance that has just passed Delhi NCR. Winds becoming calm has allowed very dense fog to form again in the region,” said Kuldeep Srivastava, scientist at IMD, adding that a fresh western disturbance is likely to influence Delhi from Saturday night.

IMD said that isolated parts of Delhi also recorded “cold day” conditions. A “cold day” is when the maximum temperature is 4.5 degrees or more below normal. It was 16.1°C at Palam, which was six degrees below normal. At Ayanagar, it was 18°C, which was five degrees below normal.

“We may see some drizzle late towards Saturday, but the major rain activity is only expected on Sunday morning. Light rain is possible across most parts of the city,” he added.

IMD classifies it as “shallow” fog when visibility is between 500m and 1000m, “moderate” when the visibility is between 200m and 500m, “dense” when visibility is between 50m and 200m and “very dense” when the visibility drops below 50m.

Delhi is in the midst of its worst fog spell in recent years. Data shared by IMD earlier this week showed that December and January recorded a combined 128 hours of dense fog — visibility below 200 metres, making it the city’s worst spell since the winter of 2014-15, when 174 such hours were recorded. According to the data, there have been 14 days of dense fog in January 2024 alone, with about 88 hours of recorded fog. This was the highest since 2015 (98 hours), IMD said.

Across the National Capital Region, Gurugram recorded a maximum of just 15.9°C, while Noida was 19.2°C. The minimum at both locations was 7.1°C and 8.9°C, respectively.

Forecasts by the Early Warning System (EWS) for Delhi — a forecasting model under the ministry of earth sciences — said Delhi’s AQI should return to “moderate” over the weekend as more rain is expected in the region.