NEW DELHI, Jan 8: A severe cold wave is sweeping Delhi and other parts of northern
India for the past few days, worse than what was experienced at the year-end.
Temperature has gone down below 2 deg C in Delhi. A dense smog is disrupting
air, rail and road traffic. On Sunday, 20 flights were delayed at Delhi airport
and Northern Railway's 42 trains were running late.
The Delhi airport had on Thursday issued a fog alert for passengers and began
low visibility procedures. The passengers were requested to contact their airlines
concerned for updated flight information.
The delayed trains included Purushottam Express, Mahabodhi Express, Farakka
Express, Sampark Kranti Express, Gorakhdham Superfast Express and Padmavat Express.
The Indian Meteorological Department (IMD) issued an orange alert for Sunday
in Delhi. Visibility was below 50 metres at the Palam observatory near the airport.
Safdarjung recorded a minimum temperature of 1.9°C, Aya Nagar 2.6°C, Lodhi Road
2.8°C and Palam recorded 5.2°C, according to the IMD.
The IMD has forecast that Punjab, Haryana, Delhi and Uttar Pradesh are likely
to witness “dense to very dense fog” on Sunday and Monday also during night
and morning hours. Uttar Pradesh and Rajasthan recorded a temperature of five
and seven deg Cs on Sunday morning.
“No significant change in minimum temperatures likely over east India during
next 3 days and rise about 2-3 degree Celsius thereafter. Fall by 2-3 degree
Celsius in minimum temperatures very likely over Madhya Pradesh during next
2 days and no significant change during subsequent 3 days,” the IMD said.
There will be dense fog in isolated pockets over Uttarakhand, Rajasthan, Bihar,
West Bengal, Sikkim, Assam and Tripura during the next three days and over Madhya
Pradesh during the next two days, it said.
What is smog: A portmanteau of the words smoke and fog, smog is polluted
fog. It is a mainly a mix of smoke and fog. It reduces visibility. The smoke
comes from burning coal, photochemicals and other fuels. It is seen in cities
everywhere, but is more common in industrial areas. Photochemical smog is produced
when sunlight reacts with nitrogen oxides from car exhaust, coal power plants
and factory emissions in fog. Apart from blocking visibility, smog is also harmful
for the lungs. Over 4,000 people died in London in the Great Smog of 1952. Smog
is also used to refer to a thick blanket or pall of the pollutants formed in
humid atmospheric conditions.
What is fog: Fog, the other common constituent of smog, is a cloud of
small water droplets suspended near the ground, formed when the wind/atmosphere
is cooling as the ground is snowy or cool. A dense fog can alone reduce visibility
to less than 1,000 metres. It can also be clouds of smoke particles or ice particles.
Especially it occurs nearby water bodies, and is influenced by topography and
wind conditions. When there is no wind, fog lingers and the trapped pollutants
can be harmful as we inhale them.
Haze: Haze is formed by dust, smoke and other dry particulates suspended
in the air. It obscures visibility.
Snow: Snow is precipitation of small white ice crystals from the water
vapor of the air or clouds. The crystals stay together to form snowflakes -
crystals stick together when the edges melt in the atmospheric temperature and
become heavy and descend to the ground. As they descend, they become bigger
too by the same process.
