Current fog spell is longest ever, say experts, expect relief from tomorrow

Tribune Web Desk

Vibha Sharma

Chandigarh, January 30   

Compared to Monday, fog on Tuesday reduced over central parts of Uttar Pradesh and East Bihar, according to IMD.

However, it continued over Punjab, Haryana, Delhi, north Rajasthan, west UP, its eastern parts and adjoining parts of west Bihar, and in isolated packets of West Bengal and Odisha, it added.

“Dense to very dense fog was observed in pockets of Punjab, Haryana, northwest Rajasthan, East UP, Delhi, Bihar and Odisha. Palam and Safdarjung continue to report dense fog conditions with 50 m visibilities and 100 per cent humidity,” it said.

However, for the people braving the biting chill and fog, relief is due from Wednesday onwards as back-to-back western disturbances will be witnessed till February 4, according to Mahesh Palawat of private weather forecaster Skymet. 

Rain and snowfall are expected under their influence this week. Fog in some pockets can be expected around February 5, 6 and 7 but the “worse seems to be over”, he added.          

Longest fog spell

According to meteorologists, the current dense fog layer (as shown by satellite pictures) from Pakistan to India to Bangladesh for more than 35 days now is the longest spell since satellite data analysis started in 2014.

Palawat said the spell has been persisting since December 28 and the main reason is the feeble WDs, which brought in high humidity but no rains or snow.

Low temperatures and still wind conditions added to the factors conducive for the formation of fog. According to reports, the previous longest period of around three weeks was recorded in the winter of 2019-20.

This season, dense fog along with low cloud cover started appearing around Punjab and Haryana around December 24/25. It then spread downward and sideward, reaching Delhi and adjoining Rajasthan and UP, and subsequently Bihar, West Bengal and Northeast. Cities across the region—Amritsar, Chandigarh, Ambala, Delhi, Lucknow and Varanasi—experienced dense fog for days altogether.

 Cold days

The dense fog cover resulted in a sharp drop in maximum and minimum temperatures. One of the major factors contributing to colder than normal temperatures—‘cold and severe cold days’—was the large-scale fog cover lasting for long durations and preventing sunlight from reaching the surface of the Earth .

While there was no heating from the Sun in daytime, chilly winds from mountains added to cold. Usually foggy or cloudy nights are associated with warmer nights, however, if fog persists for longer periods there is also cooling in the night.

Feeble WDs

Normally, a prolonged ‘cold wave’ in plains of the Western Himalayan Region is due to a large gap between two Western Disturbances.

Western Disturbances are weather systems originating in the Mediterranean region, which travel from the western to the eastern direction, bringing rain and snowfall upon its arrival in the Western Himalayan Region. Good for wheat and other Rabi crop, rain also adds to soil moisture and replenishes groundwater and water bodies

When a WD, a weather system associated with warm moist winds arrives, wind direction changes and chilly northwesterly winds from mountains stop, leading to abatement of cold wave conditions. However, the long gap allows chilly northwesterly winds from mountains to affect plains for longer times, leading to fog, absence of Sun for longer duration and radiation imbalance. In the ongoing season, WDs have been few and feeble, a reason why hills and plains in northern India also remained dry.

Persistent fog

Fog basically is a cloud formed closer to the ground due to various meteorological reasons like presence of moisture in the air, low temperatures and still winds.

It is a common phenomenon in North India at this time of the year.

However, for meteorologists, fog also is one of the most mysterious weather phenomena, primarily due to physical processes involved in its formation. It normally after the Sun sets. However, there are times when it persists throughout the day, making it difficult for the Sun to pierce its layer.

Fog is formed when air at or near the Earth's surface becomes saturated by cooling, moisture or mixing with another air parcel. It normally forms in a stable air mass environment. Larger are the changes in temperature, denser is the fog. Places that are open and with lesser habitation are more fog-prone. This season, feeble WDs further added to moisture levels in the atmosphere, say experts.

About The Author

Tribune Web Desk

The Tribune Web Desk brings you the latest news, analysis and insights from the region, India and around the world. Follow the Tribune Wed Desk for not just breaking news stories but wide-ranging coverage of events.

Join Whatsapp Channel of The Tribune for latest updates.

#Bihar #Rajasthan #Uttar Pradesh