Poor air quality and an overall change in weather patterns have made Delhi more prone to fog in the last five decades.
According to scientists, the increase in the particulate matter in Delhi’s air has been aiding the formation of fog and smog. According to a study conducted by IIT-Delhi in 2010, fog in the Capital has increased 10-fold in the last 50 years.
The foggiest years on record are 1997 and 1999. December 2014 has broken a 15-year record and was the foggiest December month since 1999.
The formation of fog and smog depends mostly on four factors — the presence of moisture in the air, low temperatures, wind and particulate matter. High moisture, low temperature, low wind speed and high amount of particulate matter aid the formation of fog.
According to Met officials, two places in the city are most prone to fog due to different reasons. One of these areas is Palam.
“The area near the airport is open and the formation of fog is very common there. This, along with areas adjoining the Yamuna, is most prone to fog during the winter months,” said an official.
This pattern, however, may change according to local variations in weather.
“There are times when the moisture level and the temperature in some part of north Delhi are more viable for fog. Generally, though, the area near the airport and around the Yamuna witness more fog,” the official added.
As per air quality indices, Anand Vihar is one area that regularly tops the charts in terms of pollution because of particulate matter.
“In Anand Vihar smog, which is not limited to winter months, is a more common phenomenon as it is generally because of the high levels (2.5 mm and 10 mm) particulate matter in the air. Anand Vihar, at times, is the most polluted area in entire Asia,” said the official.
The city witnessed another cold day on Thursday with the maximum temperature being recorded as 14.5 degrees Celsius, six degrees below normal.
The minimum temperature was recorded at 7.2 degrees Celsius, normal for this time of the year.
Dense fog for seven hours also affected flight operations at the airport.
According to RK Jenamani, director in charge, IGI Airport Met Centre, dense fog is expected on Friday and Saturday morning as well.