Weather

Sudden stratospheric warming (SSW) has been the 'in' topic in meteorological circles in the last couple of years, ever since the severe winter of 2009/2010 in which December was the coldest since the late 19th century.

SSW is linked to sudden large increases in temperature over a few days in the stratosphere over the Arctic.

This temperature change cause winds to reverse their normal direction.

For some time, forecasters have noted that a sudden weakening in high altitude winds in the stratosphere was often followed in winter by blocking surface weather systems.

These blocking weather systems tend to bring much colder conditions across Europe and the UK from the east, stopping milder air pushing in from the Atlantic.

There have been notable successes from observing this phenomenon on shorter time scales.

A week before the onset of severe cold that begun at the end of November 2010, stratospheric warming was observed, which led to a forecast which successfully included a risk of cold conditions developing across the UK.

The cold weather which occurred in 2006 and 2010 also coincided with sudden stratospheric warming.

But it would be much more helpful if the onset of such severe weather could be forecast further ahead, and that is what researchers at the Met Office have been working on, publishing research in Environmental Research Letters last month.

A breakthrough came last year when scientists at the Met Office demonstrated a clear link between stratospheric influence on climate during a sudden stratospheric warming, with easterly winds burrowing down through the atmosphere to affect the jet stream.

Following on from this, researchers at the Met Office have produced a model that is better at simulating stratospheric warming, which may give forecasters a better chance of signalling cold winters in future.

By using this new model with data available from autumn 2009, the Met Office showed that they could have seen the cold coming well in advance.

But blasts of cold weather are not always due to SSW.

There are several competing influences each winter, such as Atlantic sea surface temperatures, volcanic eruptions, snow cover and solar forcing.

For example, the research highlights the deep solar minimum as a contributory factor to the observed severe weather conditions in 2009/2010.

But separating their effects, and establishing which has the largest impact, remains a big headache for forecasters.

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Comments

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  • Comment number 102. Posted by newdwr54

    on 18 Oct 2012 18:32

    101. John Marshall wrote:

    "Another climate driver not considered but important and far more so than a trace gas in the atmosphere."

    Water vapour is a trace gas in the atmosphere.

    Is it also unimportant?

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  • Comment number 101. Posted by John Marshall

    on 18 Oct 2012 10:58

    Very interesting post especially given today's report in the Telegraph that the Met Office expect this winter to be cooler than average (whatever that is). the sun has been ignored for long enough, in favour of the quasi-religious quest to get rid of CO2. According to Bob Tisdale, writing on WUWT, all temperature anomalies, normally blamed on AGW, can be explained by the natural ENSO, PDO. ADO cycles. Perhaps these are affected by SSW as well.
    Another climate driver not considered but important and far more so than a trace gas in the atmosphere.

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  • Comment number 100. Posted by QuaesoVeritas

    on 17 Oct 2012 13:56

    lateintheday,

    While the quote from the article you posted does say 1.5 sq km, earlier in the article, it says:

    "The seven stations combined cover approximately 1.5 million sq km, or 1% of the Earth’s total land surface area."

    So he apparently is taking about a much larger area, although the phrase "area around Alice Springs" is strictly correct, I think it is a bit misleading.

    Also, in trying to find the total land are of the planet, I mis-read the figure for the total surface area as the total land area.
    The actual total land area is about 149 million square km, so the figures in the article are approximately correct, if you assume an area of 1.5 million square km is involved.

    So it seems the confusion is due to the fact that the area was given as only 1.5 square km, instead of 1.5 million square km, in the section you quoted.

    I haven't read all of the comments on the article, so someone may have pointed that out, but it obviously hasn't been corrected yet.

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  • Comment number 99. Posted by QuaesoVeritas

    on 17 Oct 2012 12:13

    #98. - lateintheday wrote:
    "Worth a read - even if to pull apart."

    I'll have a look at it.
    If I am correct, I can't believe that nobody else has spotted it, so there may be
    something in the full article which explains the apparent discrepancy.

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  • Comment number 98. Posted by lateintheday

    on 17 Oct 2012 11:03

    Well QV, even I know what you mean - it doesn't seem likely. However, Tallbloke does run through some of the numbers in the post and I'm sure you would spot a calc error on this scale.
    If you haven't read the post, then as I understand it, the data from nearby stations (which are actually not nearby because we're talking about Australia) don't appear to warrant a adjustment of any kind since they are mostly in agreement. A minority (couple of stations) which showed some warming have therefore had a massively disproportionate effect because the majority of stations were adjusted to match the minority.
    Worth a read - even if to pull apart.

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  • Comment number 97. Posted by QuaesoVeritas

    on 17 Oct 2012 10:06

    #95. - lateintheday wrote:
    "We are now in a position to conclude that the GHCN v3.2 warming adjustments applied to the GHCN v2 records in and around Alice Springs have manufactured approximately 2C of nonexistent warming since 1880. Spread over an area of 1.5 sq km this adds only about 0.02C of non-existent warming to the global land surface air temperature series, but it adds about 0.2C of nonexistent warming to the series in the Southern Hemisphere, where there’s a lot less land."

    Instinctively I feel that a false warming of 2c over an area of only 1.5 square km is unlikely to result in a warming of 0.2c over the whole S.H. or 0.02c over the entire planet.

    Would this not imply a land area in the S.H. of only 15 square km and for the globe of 150 square km?

    Since the actual land area of the S.H. is approximately 15 MILLION square km, the S.H. figure would be approximately correct if the area around Alice Springs were 1.5 MILLION square km, but the total area of Australia is about 7.7 million square km and that of the Northern Territories is about 1/6 of that, i.e. 1.35 million square km, so the figures would be approximately correct if the area involved were the whole of the Northern Territories, not just the "area around Alice Springs".

    There again, the land surface area of the globe is approximately 510 million square km, so the effect on the entire global temperature would only be approximately 0.005c, IF the area involved were the whole of the Northern Territories.

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  • Comment number 96. Posted by QuaesoVeritas

    on 17 Oct 2012 09:26

    JAXA ice extent up 295,781 square km, now 154,844 square km above the 2007 extent figure on the same date.
    Currently heading in the direction of the 2011 extent and may exceed that soon.
    The daily change on the 16th appears to be the largest recorded over the Sept. to Nov. period since 2002.
    http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

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  • Comment number 95. Posted by lateintheday

    on 17 Oct 2012 08:05

    further to my comment@48 I've found that link regarding temp adjustments in the Southern Hemisphere/Alice Springs etc.

    It was a recent (October) post at tallblokes talkshop titled 'chunder down under'. He reckons that . . .
    "We are now in a position to conclude that the GHCN v3.2 warming adjustments applied to the GHCN v2 records in and around Alice Springs have manufactured approximately 2C of nonexistent warming since 1880. Spread over an area of 1.5 sq km this adds only about 0.02C of non-existent warming to the global land surface air temperature series, but it adds about 0.2C of nonexistent warming to the series in the Southern Hemisphere, where there’s a lot less land."

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  • Comment number 94. Posted by QuaesoVeritas

    on 16 Oct 2012 11:38

    #93. - ukpahonta wrote:
    "As in the above post:"

    Sorry for missing the obvious!

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  • Comment number 93. Posted by ukpahonta

    on 16 Oct 2012 10:51

    #90 QV

    'Do you have a URL for the whole of the above quote?'

    As in the above post:

    http://www.cru.uea.ac.uk/cru/data/temperature/
    Answers to Frequently-asked Questions, bottom section of page.

    http://www.cru.uea.ac.uk/cru/info/warming/
    Footnote.

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