Weather records from 1875 could help predict snowfall

20 years ago residents of Dumfries and Galloway were surprised by the heaviest snowfall on record. Image copyright Dumfries and Galloway libraries
Image caption People living in Dumfries and Galloway were surprised by heavy snow 20 years ago

Weather records dating back 140 years could now help predict snowfall in Scotland, according to scientists at the University of Edinburgh.

A new study shows the data, dating from 1875, links large air pressure changes in the North Atlantic ocean to winter weather in Scotland.

The findings could lead to a better understanding of where and when snow is likely to fall.

The changes had already been linked to weather conditions in northern Europe.

Michael Spencer, of the University of Edinburgh's School of GeoSciences, who led the study, said: "For the first time, we have quantified the relationship between snow cover in Scotland and changing air pressure.

"Easterly air flows are known to bring cold weather from the Arctic, causing severe winters like those seen in 2009 and 2010.

"As seasonal forecasts of the North Atlantic Oscillation continue to improve, earlier and more informed predictions of snowfall will be possible."

Image copyright Dumfries and Galloway libraries

The changes in pressure were logged using the North Atlantic Oscillation index, or NAO, between 1875 and 2013.

Researchers compared historic snow cover records with NAO readings over the same time period.

It was already known that in northern Europe, high pressure NAO readings tend to indicate mild weather caused by warm, westerly winds.

Low pressure readings suggest cold air is more likely to blow in from the east, bringing wintry conditions.

But until now, the link between the two was poorly understood.

Air pressure

The study found that if the NAO index was low, areas of Scotland below 750m were more likely to have snow cover.

When the index was high, the same areas were largely unaffected.

The link was strongest in south west Scotland and eastern areas, which are low-lying and the most exposed to easterly air flows, the team said.

In inland areas, where the land was higher, it was less evident, as low temperatures mean snow can fall regardless of North Atlantic air pressure changes.

The findings showed that changes in the NAO index impact where, and for how long, there is likely to be snow in Scotland.

The study was funded by the Natural Environment Research Council, and was published in the journal Hydrology Research.

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