The dense fog in the Delhi NCR and North Indian region specially during the winter season depends upon the various factors:
Geographical factors:
1.Indo Gangetic Plains- During winter season, hot air goes upward and cold air remains beneath it, so cold air gets trap in between. so the moisture present in the air get condensed by the cold layer.
2.Himalayan region- Mountains in the Himalaya prevents the cold air to escape from the plain region present in the North Indian region, which further increases the fog intensity.
Weather patterns:
1.Temperature- As the winter comes, the temperature suddenly decreases, which makes the ground colder and also cools the air present above the ground. This condenses the moisture present in the air and thus increases the fog
2.Humidity- Irrigation in the North Indian region specially the Punjab and Haryana region and also other agricultural activities contributes to moisture increment and thus increases the fog intensity and when combined with the cold temperature this fog gets further denser.
3.Low winds- Wind helps the fog to get vanish, as high winds take the fog along with them, hence decreases the fog density. But in the North Indian region, there is low wind in the winter season, which makes the fog even more denser and more persistent.
4.Lack of rain- Lack of rain during the winter season limits the removal of moisture from the air, hence ultimately contributes to fog accumulation.
Other major factor which is causing unusual fog production is the pollution.
Two major reasons for pollution are-
1.Automobile emission- Vehicle emission releases the fine particulate matter in the air, which condenses the water vapor, this becoming a major factor in the fog accumulation
2.Agricultural stubble burn- The harvesting remains in the agricultural areas are often burnt, which releases large amount of pollutants in the air, making the situation more worse.
These all factors contributes to the frequent and dense fog in the Delhi NCR and North Indian states.
These fog conditions disrupts the transportation and also affects the daily life of native people.