Scientists begin to unravel summer jet stream mystery

Posted: August 25, 2016 by oldbrew in atmosphere, climate, Natural Variation, weather
Tags:

Forecaster highlights the jetstream over the UK [image credit: BBC]

Forecaster highlights the jetstream over the UK [image credit: BBC]


Why jetstream shifts might be linked to Arctic ice (among other factors) is not made clear, so we’re left wondering.

Scientists have discovered the cause of the recent run of miserable wet summers as they begin to unravel the mysteries of the Atlantic jet stream, reports Phys.org.

Researchers from the University of Sheffield and The Met Office have identified a number of possible factors that may influence the Atlantic jet stream and therefore help to predict summer climate from one year to the next.

The summer weather in the UK and northwest Europe is influenced by the position and strength of the Atlantic jet stream – a ribbon of very strong winds which are caused by the temperature difference between tropical and polar air masses.

A northward shift in the Atlantic jet stream tends to direct low-pressure systems northwards and away from the UK, leading to warm and dry weather during summer.

But, if the summer jet slips southwards it can lead to the jet shifting the low-pressure systems directly over the UK, causing miserable weather like we experienced in the first half of this summer. The big question is “why does the jet stream shift?”

The report, led by PhD student Richard Hall and Professor Edward Hanna from the University of Sheffield’s Department of Geography, discovered that up to 35 per cent of this variability may be predictable—a significant advance which may help in the development of seasonal forecasting models.

Lead author of the study, Richard Hall, said: “There is nothing people in the UK like to discuss more than the weather. This is because it can fluctuate so drastically—we can be basking in high temperatures and sunshine one week only to be struck by heavy downpours and strong winds the next.

“Our study will help forecasters to predict further into the future giving a clearer picture of the weather to come.”

The findings suggest the latitude of the Atlantic jet stream in summer is influenced by several factors including sea surface temperatures, solar variability, and the extent of Arctic sea-ice, indicating a potential long-term memory and predictability in the climate system.

Edward Hanna, Professor of Climate Change at the University of Sheffield, said: “Working with The Met Office we were able to look at the different factors which may influence the jet stream, which paves the way for improvements in long-term forecasting.”

Professor Adam Scaife, Head of long range forecasting at the Met Office, said: “We’ve made big inroads into long-range forecasts for winter, but we are still limited to shorter-range weather forecasts in summer. Studies like this help to identify ways to break into the long-range summer forecast problem.”

The study, published today (Wednesday Aug. 25, 2016) in the journal Climate Dynamics.

Source: Scientists begin to unravel summer jet stream mystery | Phys.org

Comments
  1. Stephen Richards says:

    Another load of crap. 30% chance of being right if the models are right and their physics are right.

  2. oldbrew says:

    Met Office man says: ‘We’ve made big inroads into long-range forecasts for winter’

    Let’s see how that works out.

  3. TinyCO2 says:

    Is the weather affected by the ice extent or is the ice extent affected by the weather? I’ve noticed that a lot of the time when we have a lot of low pressure systems the ice blows out of the Fram Strait. When we have high pressure, the ice tends to stay in the basin. This happens all year long and a great deal of ice can be lost in the autumn, early winter even as it’s growing in other areas. I doubt that this was much different in the 80s and 90s, it was just happening with a higher starting point so the effect wasn’t as obvious.

  4. BLACK PEARL says:

    “solar variability” they must have plagiarised Piers Corbyn’s findings
    ***************

    Met Office man says: ‘We’ve made big inroads into long-range forecasts for winter’

    Hah ! ……. legends in their own minds

    They should be paid like our ‘successful’ Team GB Athletes which returns positive results
    On the premise of i.e if you come up with the ‘goodies’ the funding continues
    If not…. it gets pulled ….

  5. erl happ says:

    There is no mention of the differences in air density and tropopause height that is due to the ozone content of the air in higher latitudes and how this affects the balance of surface pressure between high and mid latitudes. So, no mention of the Arctic Oscillation Index or the Northern Annular Mode. These guys are not getting to first base.

  6. Curious George says:

    Scientists begin to unravel mysteries of climate.

    Science settled. Case closed.

  7. Bitter& Twisted says:

    35% predictable?
    So still less practicable than tossing a coin (50%)
    And this is newsworthy?!

  8. oldbrew says:

    If ‘solar variability’ is admitted to be a factor in jetstream behaviour – possibly the main factor? – they need to find a way to quantify such variability.

    Then have another look at their temperature charts😎

  9. oldbrew says:

    On the subject of unravelling, it turns out that the nutty professor who keeps claiming the Arctic is about to become ‘ice free’, is promoting his book on the subject.
    http://www.thegwpf.com/climate-experts-at-war-over-prediction-of-ice-free-arctic/

    That seems to explain the publicity-chasing rants a lot better than the actual evidence does.

  10. Bryan says:

    BLACK PEARL says:

    “solar variability” they must have plagiarised Piers Corbyn’s findings”

    Yes and Jet Stream analysis has formed the basis of Piers Corbyn’s method.
    Perhaps they will also have to acknowledge PC’s other main conclusion that CO2 plays little or no part in the climate variation

  11. oldbrew says:

    erl happ says: ‘These guys are not getting to first base.’

    No change there then🙂

    But at least they are bringing ‘solar variability’ into the picture, instead of pretending it’s too trivial to matter. And by implication moving away from notions that trace gases could somehow determine jetstream patterns.

    Bombshell: New study confirms ‘solar activity has a direct impact on Earth’s cloud cover’ important to climate change
    http://hockeyschtick.blogspot.co.uk/2016/08/bombshell-new-study-confirms-solar.html

  12. Paul Maxit says:

    Really hilarious.

    They should have started by reading and understanding Marcel Leroux’s concept of Mobile Polar High.

    The Jet Stream is nothing but the consequence (and not the cause of anything) of the dynamic behaviour of of lower level polar air masses originating from the poles.

    The faster, colder (more dense), with more meridional trajectory those Mobile Polar Highs are, and the farther south you will find the jet stream.

    http://ddata.over-blog.com/xxxyyy/2/32/25/79/Leroux-Global-and-Planetary-Change-1993.pdf

  13. A C Osborn says:

    Some days they can’t even get the Weather right for Swansea on the SAME DAY, let alone 5, 4, 3, 2, or 1 day before.

  14. ren says:

    Why does water vapor rise?

  15. ulriclyons says:

    Hey they found out that the jet stream behaviour effects our summer weather!

  16. oldbrew says:

    ‘Why does water vapour rise?’

    This might have something to do with it…
    ‘Water vapor is lighter or less dense than dry air. At equivalent temperatures it is buoyant with respect to dry air’
    http://en.wikipedia.org/wiki/Water_vapor#Impact_on_air_density

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