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Talking About the Polar Vortex...


stodge
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Posted
  • Location: East Ham, London
  • Location: East Ham, London

    There's a lot of talk over in the Model Discussion Forum about the strength of the Polar Vortex and the impact of the temperature of the Stratosphere.

     

    Let me start with a confession that I'm more of a historian than someone interested in the weather but the two are connected in any number of ways.

     

    My first thought is to ask if the PV is often situated around or over Greenland ? Given its influence on the weather systems, you'd be forgiven for thinking it's been there for hundreds, if not thousands of years, but is that true ? The British winter is prevailingly temperate and that could be explained by the position and strength of the PV but it also seems connected to the stratosphere and its temperature profile.

     

    Does the Stratosphere go through cycles of warming/cooling in winter ? Is it warmer some years than others and if so why ?

     

    Back to the history, then. During the LIA, would it be fair to say the PV was weaker or differentally positioned to today ? The accounts of the period talk more about the intensity of the cold then the snow which suggests to me long periods of anticyclonic conditions with E'ly or SE'ly flows off Europe rather than snowfall. That in turn would suggest a weaker or disrupted PV perhaps over Siberia but why did this happen ?

     

    Going forward, it seems to me that a stronger PV is a logical outcome of a more energetic atmosphere but is that valid and would not the stratossphere be warmer as a result of changes in the troposphere ?

     

    I'm sorry - plenty of questions I know but I'm trying to understand how the weather might have worked in the past and its influence on our cultural and historical development.

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    Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.

    Good question, Stodge; and one that I've been struggling with of late, too.

     

    I don't have much at all in the way of answers, but I'm erring toward the recent fluctuations in Solar output; its possible effects on the PFJ, stratospheric temperature profiles, Arctic sea-ice extent and HLBs...I could do with some expert import, I think...

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    Posted
  • Location: Knowle, Solihull - 400ft (122m) ASL
  • Location: Knowle, Solihull - 400ft (122m) ASL

    Stodge, it might be worth posting your questions within the Stratosphere Temperature Watch thread instead (http://forum.netweather.tv/topic/78161-stratosphere-temperature-watch-20132014/), bearing in mind how closely associated the PV is to all things Stratospheric Posted Image

     

    Bish

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    Posted
  • Location: The Netherlands
  • Location: The Netherlands

    Indeed a very interesting set of questions!

     

    I'll try to answer some of the questions, though I have to admit that I'm still a beginner concerning stratosphere meteorology.

     

    First, the polar vortex is, as far as I know, not often located over Greenland (at 100 mb level). Usually, its position oscillates between 80N and 90N, with locations possible at every western and eastern longitude. There could be some places where the PV prefers to be located, but I'm too unsure to point toward any location.

     

    Second, the Stratosphere does go through cycles of warming and cooling every year. It is the warmest in the summer and coolest in the winter, as seen in the figure below:

    Posted Image

    The image shows the yearly temperature variation in the stratosphere (10mb), with the mean in green. The warming during summer and cooling during winter can be clearly seen.

     

    Also note that there is indeed some yearly variation in extremes in the temperature of the stratosphere (larger during winter than during summer). The large variation in stratospheric temperatures during winter is linked to Sudden Stratospheric Warming events.

     

    About the PV strength, it seems to me that the PV more or less 'triggers' an energetic atmosphere (large temperature differences at a very short distance), though the link vice versa could also be present.

     

    Furthermore, changes in the troposphere can indeed cause the stratosphere to warm. Often, the main cause is a Sudden Stratospheric Warming (SSW). The source is, as from Wikipedia:

     

     

     

    One reason for major stratospheric warmings to occur in the Northern hemisphere is because orography and land-sea temperature contrasts are responsible for the generation of long (wavenumber 1 or 2) Rossby waves in the troposphere. These waves travel upward to the stratosphere and are dissipated there, producing the warming by decelerating the mean flow. 

     

    More in-depth information about SSW's can be found here:

    http://www.met.reading.ac.uk/Data/CurrentWeather/wcd/blog/sudden-stratospheric-stirrings/

     

    Some information about history trends of the PV can be found here:

    http://www.arctic.noaa.gov/detect/climate-strat.shtml

     

    And for more (semi) in-depth information about the PV, check the link below:

    http://lasp.colorado.edu/home/education/k-12/space-weather-compendium/vortex-interactive/

     

    I hoped this helped a little. For me, there is also a lot to learn about the PV, and all the dynamics behind it. 

     

    Sources:

    http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/

    http://lasp.colorado.edu/home/education/k-12/space-weather-compendium/vortex-interactive/

    http://en.wikipedia.org/wiki/Sudden_stratospheric_warming

    Edited by Vorticity0123
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    Posted
  • Location: East Ham, London
  • Location: East Ham, London

    Thanks very much for the responses.

     

    You've answered some of my questions but I'm going to follow the Bish's advice and take this into the Strat thread.

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    Posted
  • Location: South Croydon
  • Location: South Croydon

    I'm trying to get my head around all this too.

     

    On a basic level the Stratosphere is where ozone can be found.  So heating of the Stratosphere is the result of absorption of of UV radiation from the zone by molecules of ozone.  This would explain the seasonal variation in Stratosphere linked to the amount and intensity of UV radiation coming from the sun.  This of course doesn't really help with the SSW or explain it.

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    Posted
  • Location: Braintree essex
  • Weather Preferences: Anything exciting.
  • Location: Braintree essex

    The polar vortex over the USA now what are the likely outcomes for weather in the uk in the coming days?

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    Posted
  • Location: The Netherlands
  • Location: The Netherlands

    It seems like huge amounts of confusion are being caused by the Polar Vortex, which seems to be getting a hot topic in the last few months. Not without reason, though. Lorenzo posted something about this confusion in the stratosphere thread, stating that: 

     

     

    Twitter is a hoot just now as US media coverage of the polar vortex goes into overdrive. Read a post yesterday where the news had run with a story - What to do if you are caught in one???

    Source: http://forum.netweather.tv/topic/78161-stratosphere-temperature-watch-20132014/page-47

     

    Things are really getting problematic, as far as I can see it...

    Edited by Vorticity0123
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    Posted
  • Location: Camborne
  • Location: Camborne

    Regarding the confusion over the Polar Vortex a simple explanation from the METO.

     

    The weather over North America has been hitting the headlines over the last few days with record breaking cold conditions spreading south from the Arctic. This has been linked to a ‘polar vortex’, but what is this and what could it mean for the UK?

     

    What is the Polar Vortex?

     

    The Polar Vortex is a term normally used to describe the persistent large-scale low pressure area situated around 50km above the poles in the stratosphere. When the vortex breaks down the eastern US is often cold, but this breakdown hasn’t happened yet. It is not clear to what extent the Polar Vortex is influencing surface weather at the moment.

     

    What is happening over the USA?

     

    The American use of the phrase ‘polar vortex’ referring to the extremely cold conditions over North America is slightly different to traditional definition above. It refers to features lower in the atmosphere – in the troposphere, where our weather happens.

    In the winter a deep reservoir of cold air becomes established through the atmosphere over the Arctic because of the lack of sunlight. This is usually held over high latitudes by the jet stream.

     

    What is happening over North America is that the jet stream has weakened and moved southwards in the wake of a low pressure system as it moved east over the Atlantic.  This allowed the reservoir of cold air to move southwards across the US, resulting in extremely low temperatures.

     

    What does it mean for the UK? Does it mean it will get cold here?

     

    Not at the moment. We get our coldest weather in the winter when the winds blow from the northeast or east – so from the continent.

    In fact the cold weather in the US can strengthen the jet stream and bring the UK milder and wetter weather, much as we have seen over the last few days.

     

    Currently our winds are blowing from the west and, while we will see the temperatures dropping from the mild conditions we have had during December, they will only be returning to something much closer to normal for the time of year.

     

    http://metofficenews.wordpress.com/

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    Posted
  • Location: North Bristol
  • Weather Preferences: Thunderstorms / Sunshine / Snow
  • Location: North Bristol

    In addition to the info above I was reading this from http://www.decodedscience.com/polar-vortex-friend-foe/41233

     

    ---------------------------------------------------------------------------------------

     

    The polar vortex is always in existence, customarily causing seasonally cold weather in Canada and Russia, and regularly bringing a modest chill farther south. Sometimes, however, the polar vortex gets frisky.

     

    What Exactly is the Polar Vortex?

    The polar vortex is simply a low pressure center  in the middle of the atmosphere, located near the pole. The circulation around the polar vortex is commonly known as the jet stream.

    In the southern hemisphere, the polar vortex is fairly uniform. In the northern hemisphere, the irregularity of the land masses leads to a circulation with a split personality — a bi-polar vortex as it were.

     

    What Causes the Polar Vortex?

    All weather on Earth owes its existence to the fact that the Earth is round and the poles receive less sunlight, and therefore less heat, than the equator. Cold air is denser than hot air, so if one goes up to a given height at the pole, there is more air below, and thus less air above, than at the equator. At a given altitude, the pressure is lower above the cold air of the poles than above the warm air of the tropics.

    Air would like to flow from higher pressure to lower pressure, but there is the complication of the earth’s rotation. This introduces a ‘force’ (the Coriolis force) which turns the wind 90 degrees to the right. So air flows with low pressure on its left and high pressure on its right. Everyone is familiar with cyclonic (clockwise) and anticyclonic (counterclockwise) flow around low and high pressure systems. And that’s all the polar vortex is: A low pressure center in the mid-levels of the atmosphere, located near the pole.

     

    The Position of the Polar Vortex in the Northern Hemisphere

    The area around the north pole comprises water, ice, and land masses of various sizes. As a result, the polar vortex tends to have two centers; one over northern Canada and another over Siberia. Occasionally one of the vortices wanders to a location that proves inconvenient to those not used to frigid temperatures. That is what happened in the extreme arctic outbreak over the United States in January, 2014. The vortex over Canada became displaced to the south, and arctic air spilled into the central and eastern U.S.

    Edited by Chris K
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    Posted
  • Location: Eastbourne, East Sussex (work in Mid Sussex)
  • Location: Eastbourne, East Sussex (work in Mid Sussex)
    Polar vortex over US brings abnormally mild weather to Scandinavia
     
    Weather system disrupts flora and fauna in Nordic countries, with bears reportedly emerging from hibernation
     
    The freezing polar vortex that has gripped the US has extended an abnormally mild winter in Scandinavia and disrupted the seasonal patterns of flora and fauna. The weather system that brought snow, ice and record low temperatures to many parts of the United States this week left Iceland, Greenland and Scandinavia much warmer than normal.
     
    On the back of a generally mild winter, there have been reports of bears emerging early from hibernation in Finland, changes in the behaviour of migratory birds off the coast of Sweden and plants appearing earlier than normal in Norway.Scandinavia and Russia's cold weather during the winter comes from a high-pressure system that keeps warmer, more humid air and low-pressure systems with wind and rain from coming up from the Atlantic Ocean.The weakening of the jetstream that holds this in place has allowed cold air to spill further south into much of the United States and Canada, while bringing above-average temperatures to parts of Europe.
     
    The knock-on effects of the vortex follow one of the mildest Decembers in a century in Nordic countries. Ketil Isaksen, a scientist at the Norwegian Meteorological Institute, said the country had been 4.2C above the mean temperature for December with parts of Oslo and south-eastern Norway experiencing the third warmest December on record. "It was very unusual to see no snow in large areas where it is normal in December. Only in the mountains and certain parts of Norway could you find snow." Much of the precipitation in lowland and populated areas had fallen as rain instead of snow, he said. "In general it was a very wet December. Large parts of Norway had up to three times as much rain as normal and the country as a whole had 180% more than average."
     
    Finland too has seen heavy rain, with flooding in western coastal areas and the majority of Finland's lakes containing record volumes of water. Temperatures exceeded their normal seasonal average by 4-5C nationwide, with Helsinki and southern Finland recording the mildest second half of December in 30 years. Temperatures in parts of Sweden have fluctuated greatly, at Nikkaluokta falling from 4.7C on 3 December to -40.8C on 9 December, then rising two days later to 7.7C. Many locations measured their warmest December temperatures on record. "In the north, winter has arrived, but in the south it's autumn according to the meteorological definition," the Swedish Meteorological and Hydrological Institute said.
     
    The rainy weather in Finland has reportedly disrupted the winter slumbers of many bears, bringing them out of hibernation early. Heavy rains and high waters may have invaded some dens, forcing the animals to seek new shelter. Prof Jon Swenson of the Norwegian University of Life Sciences, leader of the Scandinavian bear project, said he was worried about the indirect effects of the warmer weather. "If you go down into southern Europe, it's warmer, and there are some bears that don't hibernate. "It doesn't seem to be harmful not to hibernate," he said. "What we are afraid of is that it means there will be more thawing periods … this really stresses the berry-producing plants. This can cause some mortality, and can have a very adverse effect on berry production. And that's what the bears survive on in the autumn, and what they use to get them through the winter. So the results of this mild weather won't be seen for some time."
     
    Last week, the local Norwegian newspaper Sunnmørsposten published reader photographs of daffodils emerging as early as 14 December as well as crocuses, daisies, dandelions and honeysuckle. The World Wide Fund for Nature (WWF) Norway chief executive, Nina Jensen, said she was "cautious about drawing conclusions from one mild winter into specific changes in nature", but there were signals that changes were happening. "We are definitely seeing plants like bluebells flowering that wouldn't come out until spring, and birds singing that wouldn't normally be at this time of year. There are quite obvious changes in the growth season, plant growth and migratory bird routes and timing. The flip side of this warmer winter is that we will also have an increasing threat of harmful introduced organisms, such as the wild boar or ticks that thrive in warmer temperatures."
     
    PÃ¥l Hermansen, a wildlife photographer based in Oslo, said: "It's the smaller things where you see it most, especially butterflies and other insects. The combination of 'proper winters' with lots of snow, alternating with winters like this one, makes everything very unstable. In the 30 years I've been working we've seen butterfly populations reduce by 80-90%. We're now seeing mosquitos and ticks during the winter, which is unheard of. Ticks are spreading much further north than they ever were before."
     
    Stephen Menzie, an ornithologist working at Falsterbo Bird Observatory – a migration point in south-west Sweden – said it was "certainly true" that milder weather this year had played a part in delaying the southbound migration of many species. "We had one day in November when we ringed over 800 birds, compared to the same period last year when we struggled to catch double figures on most days."

     

     

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    In addition to the info above I was reading this from http://www.decodedscience.com/polar-vortex-friend-foe/41233

     

    ---------------------------------------------------------------------------------------

     

    The polar vortex is always in existence, customarily causing seasonally cold weather in Canada and Russia, and regularly bringing a modest chill farther south. Sometimes, however, the polar vortex gets frisky.

     

    What Exactly is the Polar Vortex?

    The polar vortex is simply a low pressure center  in the middle of the atmosphere, located near the pole. The circulation around the polar vortex is commonly known as the jet stream.

    In the southern hemisphere, the polar vortex is fairly uniform. In the northern hemisphere, the irregularity of the land masses leads to a circulation with a split personality — a bi-polar vortex as it were.

     

    What Causes the Polar Vortex?

    All weather on Earth owes its existence to the fact that the Earth is round and the poles receive less sunlight, and therefore less heat, than the equator. Cold air is denser than hot air, so if one goes up to a given height at the pole, there is more air below, and thus less air above, than at the equator. At a given altitude, the pressure is lower above the cold air of the poles than above the warm air of the tropics.

    Air would like to flow from higher pressure to lower pressure, but there is the complication of the earth’s rotation. This introduces a ‘force’ (the Coriolis force) which turns the wind 90 degrees to the right. So air flows with low pressure on its left and high pressure on its right. Everyone is familiar with cyclonic (clockwise) and anticyclonic (counterclockwise) flow around low and high pressure systems. And that’s all the polar vortex is: A low pressure center in the mid-levels of the atmosphere, located near the pole.

     

    The Position of the Polar Vortex in the Northern Hemisphere

    The area around the north pole comprises water, ice, and land masses of various sizes. As a result, the polar vortex tends to have two centers; one over northern Canada and another over Siberia. Occasionally one of the vortices wanders to a location that proves inconvenient to those not used to frigid temperatures. That is what happened in the extreme arctic outbreak over the United States in January, 2014. The vortex over Canada became displaced to the south, and arctic air spilled into the central and eastern U.S.

     

    I would urge that folk find a different source as this one has some serious flaws in it. Air, in the northern hemisphere, does not flow the way it is described above, it flows clockwise round high pressure. There are other dubious comments as well.

    Edited by johnholmes
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    Posted
  • Location: Eastbourne, East Sussex (work in Mid Sussex)
  • Location: Eastbourne, East Sussex (work in Mid Sussex)

    Posted Image

     

    These stunning images capture what the sub-zero polar vortex sweeping across the US looks like from space. The first image shows a blanket of snow stretching from the midwestern region of the US across to New England as the massive winter storm moved over the region.
     
    Posted Image
     
    Forecasters believe America’s ‘deep freeze’ is coming to an end after more than a week of disruption across the northern and mid-western states. These milder conditions are likely to cause disruption in some places, as snow and ice melt away, resulting in a lot of surface run-off in a short amount of time and a significant rise in river levels.
     
    Posted Image
     
    The cold outbreak has yielded some startling images in the past week or so, including pictures of a frozen Lake Michigan, Niagara Falls and frozen fire-hoses. At least 21 people in the US have died as a result of the extreme weather conditions.

     

     
     
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    Posted
  • Location: East Ham, London
  • Location: East Ham, London

    Morning all :)

     

    Well, I've been trying to get my head round this topic and found this interesting paper from 2009:

     

    http://www.acd.ucar.edu/Research/Highlight/stratosphere.shtml

     

    This and other papers seem to set out what could be the basic theory - the stratosphere has been cooling (though not as a uniform process) since the late 1970s which would coincide with the end of the cooling period from the 1940s which some ascribe to the influence of sulphur dioxide. A cooling stratosphere would be caused by rising levels of carbon dioxide and falling levels of stratospheric ozone. That would suggest that as the world warms (if that's what is happening) one of the consequences of increased CO2 would be to cool the stratosphere. 

     

    We can therefore posit that at times of very low CO2 (ice ages) the stratosphere was much warmer and therefore northern European winters were much colder and more blocked. Conversely at times of higher CO2 (dinosaurs), the stratosphere must have been much cooler and winters so much milder. Indeed, I believe having two polar ice caps is a rarity in Earth's climatic history.

     

    I would love to be able to prove this correlation conclusively and suspect there are other factors at work. CO2 levels are rising but we've also had cold winters with a warm stratosphere so there must be other things going on. Some cite solar activity which must play a part - I believe the LIA coincided with a period of very low solar activity - could that in turn have helped maintain stratospheric ozone levels and maintained a warmer stratosphere ?

     

    I don't know and all I have are a series of contradictory ideas.

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    • 2 weeks later...

    Hello,

    I am very much a beginner to all of this...not a lot of weather knowledge other than watching forecasting on tv and reading long range weather forecasting on the net.

    What I am puzzled about though is that can the polar vortex bring extreme cold temps to uk later on in feb / march or will it leave us with a mild winter full stop without any freezing temps at all.

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