Familiar winter fog evades Delhi, least since 2008

NEW DELHI: January is into its last week, and despite the biting chill that has enveloped the Capital, one of the staples of the month -the dense fog that reduces visibility, causes accidents on highways surrounding the city, and disrupts flights at the airport -- has largely eluded Delhi so far.

According to data from the India Meteorological Department (IMD), Delhi has so far seen only 175 hours of fog (where the visibility is below 1,000 metres) this month. The number is the lowest since 2008, when the Capital got 166 fog hours, and well below the January average of 290 fog hours.

Even in December 2021, Delhi recorded only 75 fog hours, as compared to a monthly average of 278 hours.

The number was last this low in December 1982, when the Capital also saw 75 hours of fog. Met officials attributed the scant fog last month to weak western disturbances that added little moisture to the air, while January this year saw more upper-level fog, instead of fog formation at the surface – leading to “cold day” conditions. IMD declares a “shallow fog” when the visibility is between 500 and 1,000 metres. A “moderate fog” is when visibility is between 200 and 500 metres, and a “dense fog” when the visibility is less than 200 metres.

While Delhi has seen a spate of extreme weather events every month for nearly a year-and-a-half now, which scientists have flagged as the effects of the climate crisis, experts said the lack of fog was likely an isolated weather phenomenon. IMD scientist RK Jenamani said Delhi sees an average of 570 fog hours over 52 foggy days between December and January, when fog formation in the city is at its peak. “In comparison, we have only seen 44 fog days and 250 fog hours in these two months combined this year. While there are five more days still to go in January, not much fog is expected in this period, because wind speeds will pick up once again this week,” said Jenamani.

“A western disturbance generally brings some rain. But even if it doesn’t bring any precipitation, a lot of moisture gets added to the air. This did not happen in December this time and we also had strong winds after the western disturbances departed,” explained Jenamani, adding that windy conditions are unfavourable for fog formation.