Science & Environment

Met Office experts meet to analyse 'unusual' weather patterns

Wet weather
Image caption Scientists are meeting at the Met Office to try and understand the reasons behind last summer's washout

About 20 of the UK's leading scientists and meteorologists are due to meet at the Met Office to discuss Britain's "unusual" weather patterns.

They will try to identify the factors that caused the chilly winter of 2010-11 and the long, wet summer of 2012.

They will also try to work out why this spring was the coldest in 50 years - with a UK average of 6C (42.8F) between March and May.

The Met Office hopes the meeting will identify new priorities for research.

Over the past three years, British weather records have been under increasing pressure. The big freeze that gripped the UK in December 2010 saw the lowest temperature for the month in 100 years.

Even the buzz of the London Olympics could not disguise the washout that was last summer, the second wettest for the UK since records began.

Puzzled by these events, scientists from across the UK are meeting at the Met Office in Exeter to try to understand the reasons behind this run of what they term, "unusual seasons".

Much has been made of the jet stream and how changes in these strong winds affect our weather.

But the Met Office said that it was but one factor that the researchers would consider.

"The thing to remember with the jet stream is that, much like our weather, it is a symptom of other drivers rather than a cause," said the Met Office's Dan Williams.

The scientists will examine the reduction in Arctic sea ice and how it might be affecting Europe's weather.

The theory is that the loss of ice in the Arctic means there is a smaller temperature difference between the North Pole and the warmer, mid latitudes. This in turn could weaken the jet stream, which starts to move around more. When these winds move just south of the UK, colder air can come in from the north.

And as peaks and troughs form along the stream, they can act like a trap for wet weather.

"Low pressure systems run along there and drop into a trough and it's very hard to get them back out again, they get stuck like an eddy in a river," explained Dan Williams.

"They hit us and come back and we get rain for long periods of time."

Another factor that the scientists will be considering are changes in long term ocean cycles such as the Atlantic Meridional Overturning Circulation, a system of deep currents that transport heat around the world.

Image caption The Atlantic Meridional Overturning Circulation can impact weather by distributing heat throughout the world

Prof Stephen Belcher from the Met Office Hadley Centre, who will chair the meeting, said these cycles could be having an impact.

"The ocean circulation has been stuck in a rather strange pattern for the past 10 years or so, which in fact has given the unusual weather patterns in many parts of the world," he told BBC News.

Researchers will also look at other factors including solar variability and the effect of the El Nino/La Nina weather patterns.

However a discussion of man made climate change is unlikely to feature.

"This meeting isn't looking at climate change, it's looking at climate variability in recent seasons," said Dan Williams.

"The aim is to understand some of the causes behind that variability. A lot of those potential causes cannot easily be attributed to climate change. The more we can understand about these potential causes, the better advice we can give on near-term climate from a month out to about a year ahead."

The researchers say the meeting could redefine the priorities for weather related research into the future.

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