Why is it unusually foggy over north India this winter?

  Mar 01, 2021

Why is it unusually foggy over north India this winter?

Q. What is the news?

What is behind this intense fog which has stayed on for several days this season?

Q. What is fog?.

Q. What factors led to dense fog over north India this winter?

In the absence of an active western disturbance, an anticyclone formed and stayed put over the extreme north of the plains. This coincided with the dominant easterly waves pumping in moisture into the region, favouring the fog formation. 

Q. Why is the fog unusual this year?

Even though fog over the plains of north India is common during December to February months, fog along the Indo-Gangetic plains this season has been unique in more than one way.

It is mainly due to these three reasons:

1. The prolonged persistence of foggy conditions recorded continuously between 7pm to 10.30am, especially at Amritsar airport, Punjab.

2. The growing geographical expanse of zero visibility with very dense fog conditions engulfing Punjab-Haryana-Delhi belt.

3. The timing of very dense fog for 9 to 10 days, as such conditions occur limited to 2 or 3 days within the first week of February.

Q. For how many days in February has fog been reported so far?

The airport data on fog shows that very dense fog was reported for 12 nights and days over Amritsar airport which accounted for a total of 156 hours in February (till February 19) alone. This was record sort, as, on average, Amritsar airport experiences fog for four nights and days equivalent to 15 hours, that too during the entire month. A similar trend was noticed over Amritsar in January with 16 nights/days equal to 110 hours and in December with the fog affecting 17 nights/days totalling 161 hours.

Whereas, over New Delhi, the total number of fog days has surpassed the February average, noted the Met experts. As opposed to an average three nights/days equal to 12 hours in all of February, the Indira Gandhi International (IGI) airport till February 19 has experienced fog for four nights/days measuring 13 hours.