Polar Vortex Event Explained.
The frigid temperatures are caused by a mass
of cold air that leaked from the polar vortex
in the Arctic Circle.
The polar vortex is an area of cold, low-pressure
air that swirls in the stratosphere above
Earth's North and South poles.
When it's strong, the polar vortex swirls
in a regular pattern above the Arctic Circle,
contained in part by a strong jet stream that
keeps the cold air up north and the warm air
down south.
But sometimes the winds that power the polar
vortex weaken, resulting in a destabilized
jet stream that shoots cold air to the south
� what's known as a polar vortex event.
Although the polar vortex isn't new, scientists
still aren't exactly sure what factors destabilize
it and cause these extreme weather events.
In recent years, however, some climate scientists
have suggested that global warming might be
causing disruptions above the Arctic.
Does global warming cause polar vortex events?.
Possibly.
Although it seems counter intuitive that global
warming might cause subzero temperatures,
it's known that warm air can weaken the polar
vortex.
So, considering that the Arctic is warming
at faster rates than the rest of the planet,
it's possible that global warming is disrupting
the polar vortex above the North Pole, resulting
in a weakened jet stream � the barrier that
keeps the frigid Arctic air contained in the
north.
To be sure, this theory is still being researched
by climate scientists, and what exactly causes
polar vortex events is still an open question,
as Dr. Michael Mann, the director of the Earth
System Science Center at Pennsylvania State
University, told CBS News.
These questions test the limits of both our
available data (the apparent increase in frequency
of these events is quite recent and so at
best only just starting to emerge from the
background noise) and the model simulations.
A huge mass of Arctic air is sweeping across
the U.S., bringing subzero temperatures that
have grounded flights, closed schools and
killed at least two so far.
Temperatures are lowest in the Midwest and
New England, where about 25 million people
are projected to face temperatures of minus
20 degrees Fahrenheit, with wind chills of
around minus 60 in parts of Minnesota and
North Dakota.
On Wednesday morning, Chicago was colder than
Antarctica by 10 degrees at minus 21.
"The heart of the Arctic cold has arrived,"
- the National Weather Service's Chicago office
said on Twitter.
"The combined effects of the cold & winds
are at their peak today with wind chills of
minus 45� to minus 60� continuing.
"You're talking about frostbite and hypothermia
issues very quickly, like in a matter of minutes,
may be seconds," Brian Hurley, a meteorologist
with the Weather Prediction Center, told the
Huffington Post.
What is a 'polar vortex' and why is it so
dangerous?.
The polar vortex is a large area of low pressure
and cold air surrounding both of the Earth�s
poles.
It ALWAYS exists near the poles, but weakens
in summer and strengthens in winter.
The term "vortex" refers to the counter-clockwise
flow of air that helps keep the colder air
near the Poles.
Many times during winter in the northern hemisphere,
the polar vortex will expand, sending cold
air southward with the jet stream.
This occurs fairly regularly during wintertime
and is often associated with large outbreaks
of Arctic air in the United States.
The one that occurred January 2014 is similar
to many other cold outbreaks that have occurred
in the past, including several notable colder
outbreaks in 1977, 1982, 1985 and 1989.
There are several things the polar vortex
is NOT.
Polar vortexes are not something new.
The term �polar vortex� has only recently
been popularized, bringing attention to a
weather feature that has always been present.
It is also not a feature that exists at the
Earth�s surface.
Weather forecasters examine the polar vortex
by looking at conditions tens of thousands
of feet up in the atmosphere; however, when
we feel extremely cold air from the Arctic
regions at Earth�s surface, it is sometimes
associated with the polar vortex.
This is not confined to the United States.
Portions of Europe and Asia also experience
cold surges connected to the polar vortex.
By itself, the only danger to humans is the
magnitude of how cold temperatures will get
when the polar vortex expands, sending Arctic
air southward into areas that are not typically
that cold.
In short, there is no cause to be alarmed
when you hear about the polar vortex, but
you should be prepared for colder temperatures.
Check the forecast for your area on weather.gov
to ensure you are dressed appropriately.
It is also a good idea to check the items
in your home and car emergency kits at the
beginning of each winter season to ensure
you are prepared for any type of hazardous
winter weather.
How Does Polar Vortex Works.
While we usually hear the term polar vortex
used in the singular, there actually are two
polar vortices on Earth - one in the Southern
Hemisphere over Antarctica, and one in the
Northern Hemisphere over the Arctic.
These vortices exist because in the wintertime,
the air that's high over the poles gets really,
really cold - we're talking on the order of
close to 110 degrees below zero on the Fahrenheit
scale or minus 79 degrees Celsius for the
Northern Hemisphere.
That drastic contrast with the temperatures
farther away from the pole, and the pressure
contrast that results, cause really fast winds
-- with speeds of between 120 and 250 miles
(193 and 402 kilometers) per hour - to swirl
around the big pocket of cold air.
The vortex in the Southern Hemisphere is even
colder than the one in the Northern Hemisphere.
It has faster winds and also much lower ozone
levels.
Either way, what results is a huge spinning
cyclone with cold air inside it, which hangs
high over the pole, almost like a halo.
If you were looking at it from the side, it
starts roughly around the border of the troposphere,
the lowest level of the Earth's atmosphere
and the region where our weather takes place
- and the stratosphere, the next atmospheric
layer that begins at about 12 miles (20 kilometers)
in altitude and contains the ozone that protects
Earth from too much solar radiation.
The vortex reaches all the way through the
stratosphere up to the mesosphere, the next
layer, where the air starts to get thin and
super-cold.
From a vantage point high above the North
Pole, for example, the polar vortex actually
would look like an ellipse, often swirling
around two centers - Canada's Baffin Island
and a spot in northeast Siberia, and enclosing
the icy edges of North America, Greenland,
Europe and Asia.
The polar vortex is weakest during the warmer
months of the year, when there's less of a
contrast between polar temperatures and those
in warmer regions, and it tends to become
the strongest in the winter months.
Usually, that barrier of winds keeps cold
air in the Arctic, which prevents rest of
the Northern Hemisphere from getting too chilly.
