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-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of brian
whatcott
Sent: Tuesday, January 07, 2014 2:29 PM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] Polar Vortex
On 1/7/2014 10:20 AM, LaMontagne, Bob wrote:
The current buzzword used by the media is "polar vortex". It appears to bea rather recent term, as no meteorology texts refer to it.
of low pressure, found typically over both North and South poles."
NASA explains that the polar vortex is a "whirling and persistent large area
di
A quick perusal of introductory meteorology texts finds reference
instead to the Polar High. This refers to the fact that the coldness
of the air over the poles, combined with the earth's general
atmospheric circulation (rising air over the equator and descending
air over the poles) gives rise to a generally high pressure region at
the poles - not low pressure. The descending air over the poles flows
southward at lower altitudes and turns somewhat to the west due to the
Coriolis effect (momentum conservation basically). Eventually this air
reaches warmer air to the south (Ferrell cell) and air rises where the
air flow in the two air masses converge - giving a ring of generally
low surface pressure at the latitude of the northern United States and
Southern Canada - well south of the pole. At high altitudes (upper
troposphere to stratosphere), the temperature difference between the
two air masses produces a large density difference between the two air
masses and a strong pressure gra
ent directed from the warm air mass to the colder polar one. Thisare present all the time around the jet stream - which is well south of the
strong gradient, in conjunction with the Coriolis effect, produces the
jet stream - flowing generally from west to east. The polar air is
unusually cold this year so the jet stream is very fast (180 knots in
places right now). It also is dynamically unstable and wanders
northward and southward along the boundary of the two air masses. As
it changes direction from meandering toward the southeast to a flow to
the northeast, there will be a low pressure to the north of the jet
stream - associated with its turn to the left. This is quite visible
in the upper air charts at the moment:
http://weather.noaa.gov/pub/fax/QHUA15.TIF
There is nothing unusual or novel about these low pressure regions. They
poles.
physics that is being bantered about in the media and - wait for it - how it is
The reason I bring all this up is because of all the incorrect meteorology and
supposedly connected to global warming. I have now twice seen graphics of
a huge supposed "polar vortex" of low pressure that supposedly resides over
the poles (remember the Polar High), followed by an explanation of how
global warming has split the main vortex into two vortices that have
wandered south over Southern Canada and the old Soviet Union, causing the
extremely cold weather there.
often there- winter and summer. In colder winters than usual, the
This is just silliness. The low pressure flow we are seeing over Canada is
temperature gradient just intensifies these large scale lows producing what
we all know in the US as "Alberta Clippers" or the "Montreal Express" - cold
air coming in from over the Canadian plains. The media has simply
repackaged these as the "Polar Vortex". As many have pointed out on this
list, there is a difference between weather and climate. While global
temperatures have risen over the past century, that has nothing to do with
the weather we are currently experiencing.
It appears that what Bob believes NASA defines as the locality of the polar
Bob at PC
vortices and what NASA defines as the locality of those vortices differ.
This Wiki seems to do a reasonable job of discussing the Polar High and the
Polar Vortex (low).
http://en.wikipedia.org/wiki/Polar_vortex
It has a reasonable number of supporting references which do not seem to
originate with sources of a particular political orientation.
Brian Whatcott Altus OK
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