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Dense fog in Delhi brings travel chaos

A dense fog has enveloped the Indian capital, Delhi, leading to major disruptions in air and rail traffic.

At least 60 flights have been delayed or cancelled and more than 50 trains delayed, with visibility reduced to less than 100m (330ft) in many places.

Thousands of passengers are stranded at the airport and railway stations. The meteorological department said the fog was unlikely to lift before noon.

Severely cold weather has swept through northern India in the past month.

Reports say more than 400 people have died, with most deaths reported from the northern Uttar Pradesh state.

The fog, which descended on Tuesday night, became very dense at around 2230 (1700GMT) when general visibility dropped to zero…
(10 Jan 2010)
Apparently the fog has also caused several deaths through train crashes. -KS

Blame air pollution for Capital’s blanket of fog

Dinesh C Sharma, India Today
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…
(8 Jan 2010)

Airport fog on track

Hindustan Times
Brace yourself for another season of fog, which is expected to set in at the Delhi airport by the second week of December.

“All conditions and trends, like cold weather, are in place for a normal fog season this winter,” said R.K. Jenamani, director of the Meteorological Department, IGI Airport.

On an average, the IGI airport witnesses 87 hours of dense fog (visibility below 200 metre) spread over 11 days every year.

The exact figures can wildly vary from year to year.

…Delhi getting worse
According to the data of last 28 years available with the met department, the IGI airport now witnesses more dense fog than it saw in the 1980s.
The airport witnessed between 20 to 40 hours of dense fog (visibility below 200 metre) every January between 1982 and 1997, but the figure has been roughly between 60 and 100 hours in the last decade…
(13 Nov 2009)

Fog in Lahore — causes and impact

Dr Badar Ghauri, The News Lahore, the city of glorious gardens, and adjoining areas are experiencing high air pollution in the shape of haze, smog and fog.

One of major cross-border air pollutant sources is Indian coal-based thermal power plants which consume thousands of tons of coal daily and emit tons of sulfur dioxide, black carbon etc which plays a key role in climate change. Sulfur dioxide is converted into sulfate and change the nature of regional aerosol to acidic. Sulfate, as hygroscopic species, strengthens the fog formation process during high humidity and calm wind days, which increase the density and span of winter fog besides health hazards.

Another trans-border massive source of air pollutants is extensive agriculture waste burning, especially rice straw in northwestern parts of India near the Pakistani border in October to November each year. This releases a huge amount of a wide range of air pollutants, including black carbon. Vast visible smoke sustains for many days and also forms haze over the region. Then Lahore and adjoining areas also experience dense haze for many days which continues for months due to seasonal meteorological changes, regional built up sulfate, BC, particulate matter level and local air pollutants concentration, especially nitrogen oxides and surface ozone. Sulfate and black carbon particles also play a major role in changing atmospheric and cloud chemistry in addition to direct health concerns. They affect cloud nature, rain patterns, severity of rain which drastically affect human health and crop yield of the region.

…In addition, night temperatures during winters in Lahore average between 2 and 10C, so there is considerably more heating required during winter. Also coal and wood are commonly used for residential heating in this region therefore higher overnight black carbon values in Lahore are expected. Global dimming (low visibility) is another effect of aerosols on the earth’s climate. Dimming is, in effect, a combination of the direct negative radiative forcing resulting from aerosols and the indirect effect of these aerosols on cloud formation, both increase albedo. Some pollutants such as sulfate increase the span and extent of winter fog…
(5 Jan 2010)
Some context for global dimming here. -KS