Dense fog spell delays early flights

Delhi recorded its second “dense fog” spell of the season on Tuesday, with visibility dropping down to about 50 metres at Delhi’s Indira Gandhi International (IGI) 5am onwards, delaying over 50 flights until 9am but not resulting in any cancellations.

The India Meteorological Department (IMD) said rain over the weekend brought sufficient moisture to Delhi, which may lead to spells of moderate to dense fog in the coming days as well.

RK Jenamani, scientist at IMD, said the Palam observatory recorded a visibility of 50 metres between 5am and 7am; it improved marginally to around 100 metres at 8.30am before getting better 9,30am onwards. “This is the first time this winter season that CAT-III procedures for low visibility were initiated at the Delhi airport, for which readings at Palam observatory are considered. In comparison, Safdarjung station reported moderate fog,” he said.

Delhi last reported about one hour of dense fog on December 29.

IMD classifies fog to be “dense” when visibility drops below 200 metres, while it is classified as “very dense” when it drops below 50 metres. A visibility between 200 and 500 metres is “moderate” while between 500 and 1000 metres is classified as “shallow” fog. Jenamani said there was high probability of Delhi recording dense fog in the next two days.

“The entire northern plains are now seeing moderate to dense fog. This is the first prolonged spell for Delhi,” Jenamani said.

An airport official said while no cancellations or diversions were reported on account of fog, several flights were delayed in the morning. “Despite low visibility procedures being initiated, operations were still smooth at the airport,” h he said.

Delhi has also seen a sharp drop in the minimum temperature over the last 48 hours, with colder winds now blowing towards the Capital from snow-clad mountains, where fresh snowfall was reported over the weekend. On Tuesday, Delhi’s minimum temperature was recorded at 6.5 degrees Celsius – one degree below normal and a drop of nearly 3 degrees from Monday’s minimum of 9.6 degrees.

An IMD forecast said the minimum to remain between 6-8 degrees Celsius till the end of this week, while Delhi’s maximum, which was recorded at 18.3 degrees on Tuesday, could hover between 18-20 degrees.

Delhi’s air quality index (AQI) spiked in the last 24 hours, deteriorating to the “poor” category with a reading of 224, according to the Central Pollution Control Board’s 4pm bulletin. It was 151 (moderate) on Monday.

Agencies have forecast that the air quality may worsen in the next three days, on account of low wind speed. “Delhi’s air quality will remain ‘poor’ for the next three days, but from January 15, an improvement is expected due to wind speeds picking up, leading to strong ventilation near the surface,” said the System of Air Quality and Weather Forecasting And Research (Safar).