Page last updated at 16:34 GMT, Tuesday, 2 June 2009 17:34 UK

Bid to classify cloud formation

Hammer Springs, South Island,  New Zealand - image copyright  Merrick Davies
The name asperatus comes from the Latin verb aspero

A cloudspotter from Somerset believes he has identified a new type of cloud.

Gavin Pretor-Pinney, from Somerton, who also founded the Cloud Appreciation Society, wants recognition for what he has named the asperatus cloud.

He said: "It looks quite violent - as if you are looking up from underneath the turbulent surface of the sea."

Weather forecaster Michael Fish told BBC Radio 4's Today programme he thinks it is caused by a mixing of two air masses or the bottom of a storm cloud.

Pictures 'amazing'

Mr Pretor-Pinney, who wrote the Cloudspotter's Guide which featured in the Sunday Times non-fiction bestseller list, asked his cousin - who is a Latin teacher - for a word that means choppy or turbulent that is used to describe the sea to name the cloud after.

"Asperatus comes from the Latin verb aspero meaning 'to roughen up' or 'agitate'," he said.

"It was used by the poet Virgil to describe the surface of a choppy sea."

Mr Fish said he was "quite amazed" by pictures showing clouds fitting Mr Pretor-Pinney's asperatus description.

There has been no change to the classifications of clouds since 1953 and maybe this should be considered now

Gavin Pretor-Pinney

He said: "I can offer two explanations - they are either the mixing of two air masses - very warm humid air and and very cold dry air and it is like oil and water - it doesn't mix.

"These clouds could be formed at the boundary of these two air masses.

"Or, I have just spent several weeks chasing tornado-type storms in the Mid West they could be the turbulent underbelly of one of the huge thunder clouds.

"The only way to find out for sure is to look at the meteorological observations in the area at the time," Mr Fish added.

Mr Pretor-Pinney said the pictures were sent in by cloud society members from all over the world and some of them said there was no storm activity or heavy precipitation in the area at the time.

Expert committee

He said: "We need to look into this some more and I am speaking with the Royal Meteorological Society to do that.

"There has been no change to the classifications of clouds since 1953 and maybe this should be considered now."

Clouds are classified by a committee of experts from the World Meteorological Organization (WMO) based in Switzerland.

For them to consider Mr Pretor-Pinney's suggestion the WMO would have to be lobbied by a professional body such as the Royal Meteorological Society or the Meteorological Office.

Any decision on whether it is a new classification, or regarded as a sub-classification, is likely to be a two to three-year process.

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