Original URL: http://www.theregister.co.uk/2009/01/22/underground_boffins_monitor_strato_warming/

Boffins monitor strato-weather from half-mile underground

Met boys no longer have heads in clouds

By Lewis Page

Posted in Science, 22nd January 2009 10:48 GMT

Ever since there have been weather people, aviators and sailors have taunted them for failing to simply step outside - or go to the window - and look at the sky. But now meteorology boffins have struck back, saying that actually one of the best places to monitor weather conditions is a disused mine tunnel half a mile underground.

The revelations come from the UK's National Centre for Atmospheric Science, where top atmo-boffins have been doing research into the stratosphere. Occasionally, strange abrupt warming will occur in the thin upper air, with temperatures jumping by as much as 40 degrees C. These "Sudden Stratospheric Warming events" occur every couple of years and are "notoriously unpredictable", according to the NCAS weather brains.

But it would be good if you could tell they were happening straight away, as they can have a major impact on things such as the coldness of the northern hemisphere winter and the amount of ozone that will be present above the polar regions.

According to the NCAS research, carried out in conjunction with a big US particle physics push, there is a "strikingly close relationship" between cosmic rays detected on Earth and the temperature in the stratosphere above that point.

This isn't because the cosmic rays are affecting the atmosphere, but rather the other way round. If the stratosphere heats up, its density is reduced and fewer inbound cosmic particles collide with air molecules. In particular, incoming mesons are destroyed when they hit air - but if they don't, they decay into muons.

Muons can be detected, provided the detector apparatus is well shielded from extraneous interference - in this case, by putting it in a disused iron mine half a mile underground in Minnesota. The NCAS boffins, analysing four years of records, found that an increased rainfall of ex-meson muons could be correlated in retrospect with sudden strato-heatwaves and their associated effects.

"Now we can potentially use records of cosmic-ray data dating back 50 years to give us a pretty accurate idea of what was happening to the temperature in the stratosphere over this time," says Dr Scott Osprey of NCAS.

"Looking forward, data being collected by other large underground detectors around the world can also be used to study this phenomenon."

"It's fun sitting half a mile underground," added Dr Giles Barr of Oxford Uni. "It's even better to know that from down there, we can also monitor a part of the atmosphere that is otherwise quite tricky to measure."

The research is published in the Geophysical Research Letters: Sudden stratospheric warmings seen in MINOS deep underground muon data. Osprey, S M et al, doi:10.1029/2008GL036359, in press. Or it can be seen online (by registered subscribers only) here (pdf). ®