Thick fog in Northern india  Thick fog envelops Delhi on January o8, 2010, disrupts trains and flights. Before  one year on January 06, 2009 at least 82 flights, including 26 international carriers were delayed and 10 others cancelled, while 50 Delhi-bound trains ran late as the worst fog spell in the last two years hit the capital. Most of the morning flights could not take off from Delhi as general visibility fell below 50 metres at the Indira Gandhi International Airport. No international flights could take off.   In Indian cities across the plains, the blinding fog produces traffic snarls and, elsewhere, super fast trains slow down as the billowing fog hugs railway tracks. Dozens of flights and trains are either being delayed or cancelled due to low visibility. Air services to or from airports in Northern India are severely affected, and most flights have had to be rescheduled due to heavy fog early in the morning. Hundreds of passengers are stranded at both the domestic and international airports.

Thick fog hits Delhi    North India grappled with a thick fog.

Blame air pollution for  blanket of fog   The fog blanket that covers North India every winter is a result of  changes in atmospheric chemistry brought about by pollution from various sources and moisture from the network of canal irrigation in the region, studies have shown.In particular, urban areas such as Delhi are facing increasing fog frequencies resulting due to higher levels of air pollution from variety of sources, scientists at the Indian Institute of Technology Delhi ( IITD) have concluded. The occurrence of fog in Delhi has gone up tenfold in about half a century.  The higher levels of pollutants from transport and industrial sectors cause atmospheric reactions resulting in the formation of secondary pollutants that may lead to increased ' aerosol number concentrations' in  the atmosphere. This gives rise to fog, under favourable meteorological  conditions such as low temperature and high relative humidity. Daily average concentration of respirable suspended particulate matter or RSPM - a major urban pollutant - showed a direct correlation with the occurrences of thick fog, pointed out Dr Manju Mohan of the Centre for Atmospheric Sciences at IITD. The fog seen in Delhi is part of the larger phenomenon that affects the whole of Indo- Gangetic region, which is densely populated and has very fertile areas. The region has been found to be a significant source for various types of pollutants, especially those containing compounds of sulphur, nitrogen and carbon. These are mainly emitted by different manmade activities such as burning of biomass for residential cooking and agricultural purposes, fossil fuel burning for running vehicles and industrial pollutants.   Satellite observations reveal an extensive layer of aerosols covering the entire Indo- Gangetic plane and the Himalayan foothills region. Besides pollution, the vast network of canal irrigation is another factor leading to formation of fog. The moisture content in the atmosphere goes up due to moisture from the canal network as well as from the soil, causing fog in the Indo- Gangetic plain, said Dr Arun K Saraf of the department of earth sciences at IIT Roorkee.  Hardships and Economic loss  The fog might be delaying countless appointments, pushing up the nation’s fuel bills and denying vital sunlight to winter crops. But it has also emerged as the most significant perceived weather change during winters across northern India in recent times. With the fog persisting longer than before, scientists are scrambling to seek out clues to decipher this trend. But the answers that tumble out might be hard to digest. Weather scientists have been puzzled by the sharply growing number of days that dawn with dense fog during winter months in northern India in recent years.      While pollution has long been blamed for the fog, there are now concerns that other human activities may also have had a hand in northern India’s ongoing winter fog woes. Specifically, India’s insatiable hunger for rice, and intensive campaigns to ‘green’ pockets of northern India may also be key factors contributing to the growth and persistence of fog. Agricultural and meteorological scientists say that the decades-old changes in cultivation and irrigation patterns in northern India as well as efforts to plant trees and boost forest cover in the region may be hitherto unrecognized causes of the recent behavior of fog.     A sudden fog over Delhi and NCR on March 10, 2008 stumped most people, environmentalists and meteorological experts said this was possibly the outcome of extremely high levels of pollution. The fog, they explained, was formed when moisture in the air reacted with particulate matter, a problem that specially plagues the northern region.     Officials from Power Grid Corporation Ltd (PGCL)  who were caught unawares when the unprecedented fog over parts of North India sent transmission lines on a tripping spree blamed the high pollution levels in these areas. A major reason for concern are the large number of brick kilns that are operating in all of NCR. "Instead of using coal, several of the kiln owners are burning old  footware, tyres, plastic ware and oil for fuel since it is cheaper. The sticky deposits from this are collecting on the wires and causing the tripping," said R G Yadav, executive director (operation  services) PGCL.    Other than the deposits, the burning of plastic and rubber also adds in a big way to carcinogenic emissions. Diesel vehicles, diesel run generators and massive construction activity in Delhi, Gurgaon and parts of Uttar Pradesh have also added huge quantities of particulate matter and dust in the air. Even as the levels for PM10 and PM2.5 are highly lax compared to what they are in other countries, their levels are still about five times higher than what they should be.    Industrial and traffic emission containing tiny particles are one long-known factor. Water vapor in the atmosphere condenses on these tiny particles to produce fog. But extensive irrigation has pumped extra moisture into the atmosphere. Increasing vegetation and forest cover might also add moisture to the atmosphere that could end up as fog in the winter season. Because high moisture content and low temperatures are necessary for the formation of fog. Scientists say that the growth in relative humidity could mean that fogs would persist in the years to come.    Fog aggravates asthma:  Due to fog, asthma does aggravate to some extent induced by the cold. It mainly happens due to the particulate matter in smog which triggers asthma in individuals allergic to it. Doctors say that not all the asthmatics are aware that environment plays a big role in worsening the disease, and thus fog and mist becomes one of the reasons.     FOG FACTS    From 1985 to 2005, fog level has gone up by 60% According to experts, heavy fog at this time is due to a combination of humidity and various pollutants, mainly particulate matter Delhi and Gurgaon face a huge problem with their particulate matter count, that is way higher than the prescribed limits. This is due to large scale consumption of diesel by vehicles and generator sets Other areas have a problem due to industrialisation, construction and illegal burning of plastic and rubber.

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