An
Arctic air mass known as a "polar vortex" has descended
over much of Canada and the eastern and mid-west U.S., causing
temperatures to plunge, nearing -50 C with the wind chill in some
regions.
But
what exactly is a polar vortex and how does it work? Here are four
polar vortex questions answered:
1)
What is a polar vortex?
A
polar vortex is a large, frigid air mass located near the Earth's
geographical poles. The vortex is continually circulating a pool of
cold air in a counter-clockwise direction. As the air is being
circulated in place, it grows colder and denser.
2)
Where is the polar vortex?
On
Earth, the vortex hovers around the Arctic, with two centres: one
near Canada's Baffin Island and the other near Siberia.
3)
Why is the polar vortex making this winter in particular so cold?
While
it's normal for the some of the vortex's frigid air to leach
southward during the winter, this year has proved to be exceptional.
Dan
Riddle, senior meteorologist with the U.S. National Weather Service,
told CTV News Channel that the vortex is normally present over Baffin
Island and north-central Canada for the winter, with the cold air
building up over time.
But
this year the jet stream has dipped far south, dragging a "piece"
of the vortex with it through the U.S. prairies and beyond, he said.
Riddle
said the effects of the vortex are being felt as far south as New
Orleans, La. and Tallahassee, Fla., where temperatures are dropping
to levels not seen in 30 years.
4)
How common is it to have a polar vortex descend south like this year?
Riddle
said historical records indicate that outbreaks of unusually cold
weather have occurred in U.S. in the past, with a frequency of about
one every 20 years.
Some
scientists have begun to study whether there is a link between the
effects of climate change -- including the melting of the polar ice
caps -- and extreme weather events.
"There
is a lot of thought about the changes that have been going on in the
Arctic and if that has caused colder weather to be displaced further
south," Riddle told CTV News Channel.
Source:
ctvnews
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