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ivica

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Polar Jet Stream
« on: April 24, 2013, 10:54:03 AM »
Source: http://squall.sfsu.edu/crws/jetstream.html
What a jumbled jet stream, attached:

Jim Williams

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Re: Polar Jet Stream
« Reply #1 on: April 24, 2013, 01:55:15 PM »
Ah Spring!  When a young man's fancy turns to three hundred millibars.
« Last Edit: April 25, 2013, 01:05:48 PM by Jim Williams »

ritter

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Re: Polar Jet Stream
« Reply #2 on: April 24, 2013, 06:07:33 PM »
Translation/interpretation for us lay folks would be most appreciated!

ChrisReynolds

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Re: Polar Jet Stream
« Reply #3 on: April 24, 2013, 06:48:29 PM »
Ritter,

The plot shows the modelled jet stream on a particular say, grey are the jet streams with blue arrows showing direction. The scale of shade of grey is the speed of the jet. It's quite typical to see the jet broken and twisted as in that plot. Taking the average positions of the jet by season reveals the seasonal changes. Also some features do persist and reappear amidst the 'mess', for example the loop caused by Greenland in the summer.

theoldinsane

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Re: Polar Jet Stream
« Reply #4 on: April 24, 2013, 07:10:32 PM »

ritter

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Re: Polar Jet Stream
« Reply #5 on: April 24, 2013, 07:12:55 PM »
Thanks, Chris. Working towards a rudimentary understanding of something I know very little about....

TerryM

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Re: Polar Jet Stream
« Reply #6 on: April 24, 2013, 07:57:51 PM »
Are old (pre 2007) jet stream representations available for comparison? I'd think summer and fall when changes in ice cover are most extreme might be interesting.


Terry

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Re: Polar Jet Stream
« Reply #7 on: April 25, 2013, 05:23:59 AM »
Are old (pre 2007) jet stream representations available for comparison?
Hi Terry,

Browse the Northern Hemisphere Jet Stream Map Archive. It goes back to Apr 2009.

Cheers!
Lodger

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Re: Polar Jet Stream
« Reply #8 on: April 25, 2013, 05:28:31 AM »
Translation/interpretation for us lay folks would be most appreciated!

Hi ritter,

One of the most important features of the polar jet stream is it defines the storm track in the North. Warm air is kept to the South, cold air is sealed in to the North.

When the polar jet stream becomes too convoluted in Winter, the polar vortex breaks down and then cold air escapes South from the Arctic, resulting in WACCy weather (Warm Arctic Cold Continents).

This is a new area of research, and very important to current weather events.
Cheers!
Lodger

ivica

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Re: Polar Jet Stream
« Reply #9 on: April 25, 2013, 07:56:09 AM »
...One of the most important features of the polar jet stream is it defines the storm track in the North. Warm air is kept to the South, cold air is sealed in to the North...
I like to watch animation, during winter specially. That gives me quick&dirty way to make own short term weather forecast, based on relative position of my location wrt jet stream, that is.
« Last Edit: April 25, 2013, 08:04:44 AM by ivica »

TerryM

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Re: Polar Jet Stream
« Reply #10 on: April 25, 2013, 03:44:18 PM »
Are old (pre 2007) jet stream representations available for comparison?
Hi Terry,

Browse the Northern Hemisphere Jet Stream Map Archive. It goes back to Apr 2009.


Thanks Lodger!


Terry

ritter

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Re: Polar Jet Stream
« Reply #11 on: April 25, 2013, 05:31:19 PM »
Translation/interpretation for us lay folks would be most appreciated!

Hi ritter,

One of the most important features of the polar jet stream is it defines the storm track in the North. Warm air is kept to the South, cold air is sealed in to the North.

When the polar jet stream becomes too convoluted in Winter, the polar vortex breaks down and then cold air escapes South from the Arctic, resulting in WACCy weather (Warm Arctic Cold Continents).

This is a new area of research, and very important to current weather events.

Thanks, Lodger. Those Rossby waves Ms. Francis keeps talking about?

ChrisReynolds

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Re: Polar Jet Stream
« Reply #12 on: April 25, 2013, 06:49:21 PM »
Ritter,

The Jetstream has Rossby waves on it, whereas water waves travel across the water, and cause the surface to go up and down, Rossby waves travel around the Jetstream and cause the Jetstream to meander north to south. These meanders are what is being affected by Arctic Amplification (what Francis seems to be saying), Arctic Amplification is the term used to describe how the Arctic warms faster than the rest of the globe.

What happens during Warm Arctic Cold Continents (WACC) pattern events is that the polar vortex breaks down or reverses (as it did in 2009/10's winter). Normally the polar vortex keeps cold Arctic air in the Arctic, when it breaks down it allows that air out, but also allows warmer air in from lower latitudes, so some lower latitude areas get cold outbreaks (e.g. Northern Europe), other regions further north experience unusually warm weather. If you left the freezer door open the kitchen would get colder than usual, but the Freezer would be warmer than usual.

ritter

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Re: Polar Jet Stream
« Reply #13 on: April 26, 2013, 05:42:49 PM »
Ritter,

The Jetstream has Rossby waves on it, whereas water waves travel across the water, and cause the surface to go up and down, Rossby waves travel around the Jetstream and cause the Jetstream to meander north to south. These meanders are what is being affected by Arctic Amplification (what Francis seems to be saying), Arctic Amplification is the term used to describe how the Arctic warms faster than the rest of the globe.

What happens during Warm Arctic Cold Continents (WACC) pattern events is that the polar vortex breaks down or reverses (as it did in 2009/10's winter). Normally the polar vortex keeps cold Arctic air in the Arctic, when it breaks down it allows that air out, but also allows warmer air in from lower latitudes, so some lower latitude areas get cold outbreaks (e.g. Northern Europe), other regions further north experience unusually warm weather. If you left the freezer door open the kitchen would get colder than usual, but the Freezer would be warmer than usual.

So the breakdown of the Rossby waves is a result of and reinforces arctic amplification. Yeah feedbacks.

ChrisReynolds

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Re: Polar Jet Stream
« Reply #14 on: April 26, 2013, 07:04:20 PM »
Well, the major driver of Arctic Amplification (AA) is sea ice loss, with warming above the surface being wholly due to influx of warmer air. Coincidentally I blogged on this recently.
http://dosbat.blogspot.co.uk/2013/04/the-causes-of-arctic-amplification.html

The WACC pattern only plays a small role in AA.

SteveMDFP

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Re: Polar Jet Stream
« Reply #15 on: April 26, 2013, 08:25:55 PM »
Well, the major driver of Arctic Amplification (AA) is sea ice loss, with warming above the surface being wholly due to influx of warmer air. Coincidentally I blogged on this recently.
http://dosbat.blogspot.co.uk/2013/04/the-causes-of-arctic-amplification.html

The WACC pattern only plays a small role in AA.

You've lost me.  Warm air entering the arctic must be balanced by cold air exiting.  This gives the WACC pattern.  Isn't the warming due to influx of warmer air (which you say drives Arctic Amplification) inseparably manifested by WACC?

crandles

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Re: Polar Jet Stream
« Reply #16 on: April 26, 2013, 09:36:35 PM »
Well, the major driver of Arctic Amplification (AA) is sea ice loss, with warming above the surface being wholly due to influx of warmer air. Coincidentally I blogged on this recently.
http://dosbat.blogspot.co.uk/2013/04/the-causes-of-arctic-amplification.html

The WACC pattern only plays a small role in AA.

Well I agree that WACC only plays a small role in AA.

Also that meandering rossby waves causes WACC pattern.

AA is driven by a couple of factors:
1. Loss of sea ice changes albedo.

2. Warm the tropics and that heat spreads to whole world, but if you warm the arctic that heats stays there. So given this, when you heat whole world, the effect is to warm the arctic more than lower latitudes.


AA drives meandering rossby waves, which drives WACC which is a further amplification of AA so this appears to be a feedback as ritter said.

What I don't get is "with warming above the surface being wholly due to influx of warmer air". Surely it is due to all three effects, albedo, spreading effects of GHG warming as well as WACC pattern. Perhaps a 'not' before the wholly was omitted?

ivica

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Re: Polar Jet Stream
« Reply #17 on: May 24, 2013, 05:30:46 PM »
Neven's new blog: Everything you want to know about the jet stream ...but are afraid to ask.
Quote
Skeptical Science contributor John Mason has outdone himself this time - which says a lot after his great pieces on Arctic methane and other subjects - by writing a comprehensive article about the jet stream, what it is, what it does and why that is important. Here's the introduction and table of contents, but I'd advise everyone to go read the whole thing over at Skeptical Science.
We need the link here too and here it is:
A Rough Guide to the Jet Stream: what it is, how it works and how it is responding to enhanced Arctic warming

ChrisReynolds

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Re: Polar Jet Stream
« Reply #18 on: May 24, 2013, 06:39:42 PM »
Crandles,

Sorry missed your reply. The link to the scientific paper is on the blog post, there was no 'not' missed out. The study concerned shows that warming aloft is due to remote SST changes (i.e. AGW) not due to processes within the Arctic. The surface based warming in autumn and winter due to ice loss is limited to the lower troposphere with radiation dissipating most of the heat through the atmosphere and into space.

ivica

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Re: Polar Jet Stream
« Reply #19 on: June 23, 2013, 11:51:37 PM »
Featuring Jet Stream at Climate Desk event:

Arctic Amplification (Extreme Weather): Jennifer Francis June 6, 2013


This belong also to Weird Weather thread.