A step forward in forecasting cold winters?

Thursday 11 October 2012, 16:16

Paul Hudson Paul Hudson

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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  • rate this

    Comment number 1.

    Well, well. About time they noticed that a warming stratosphere pushes the climate zones equatorward so that the polar air masses expand and spill out across the middle latitudes.

    When the sun was more active the stratosphere cooled and the climate zones shifted poleward.

    When the sun became less active following the peak of cycle 23 the stratosphere stopped warming and we have since seen more so called SSW events with a negative Arctic Oscillation and more surges of cold air equatorward.

    Full description of the processes involved and the implications here:


    "How The Sun Could Control Earth's Temperature"

    and more here:


    "CO2 or Sun?: Which one really controls Earth’s surface temperatures ?"

    As they admit:

    "the research highlights the deep solar minimum as a contributory factor to the observed severe weather conditions in 2009/2010"

    On that basis they must logically accept that the level of solar activity does indeed affect stratospheric temperatures and in turn the net position of the climate zones as I have been pointing out for several years.

    The trouble is that an active sun COOLS the stratosphere and an inactive sun WARMS the stratosphere which is the opposite of established climatology.

    That pretty much does for the CFC scare too in the process.

    I do believe they are getting there.

  • rate this

    Comment number 2.

    1. Stephen Wilde wrote:

    "The trouble is that an active sun COOLS the stratosphere and an inactive sun WARMS the stratosphere which is the opposite of established climatology."

    By what mechanism does increased solar output cool the stratosphere? Is this mechanism described in the peer reviewed literature?

  • rate this

    Comment number 3.

    #1. - Stephen Wilde wrote:
    "That pretty much does for the CFC scare too in the process."
    Does that mean that CFCs didn't cause the hole in the ozone layer?

  • rate this

    Comment number 4.

    Indeed, how does it happen?

  • rate this

    Comment number 5.

    uhh..I'm confused...surely you're not suggesting this isn't related to the extra amount of C02 humans are pumping into the atmosphere? The author of this piece should be dismissed summarily.Please get a competent global warming fanatic to analyse the weather in a rational and objective fashion.


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I worked as a forecaster with the Met Office for nearly 15 years locally and at the international unit, after graduating with first class honours in Geophysics and Planetary physics at the University of Newcastle upon Tyne in 1992. I then joined the BBC in October 2007, where I divide my time between forecasting and reporting on stories about climate change and its implications for people's everyday lives.

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