Undulatus Asperatus: Close to official adoption

Wednesday 01st Oct 2014 by theWeather Club

Image by Ave Maria Mõistlik

A World Meteorological Organization (WMO) task team has recommended that ‘asperatus’ be included in the forthcoming edition of the International Cloud Atlas, the first new edition in four decades. However, the final decision lies in the hands of the WMO’s larger commission body.

Gavin Pretor-Pinney, founder of the Cloud Appreciation Society (http://cloudappreciationsociety.org/), presented evidence for this new cloud variety to Royal Meteorological Society in 2008 after receiving numerous images over the years (read the original story here: http://www.rmets.org/asperatus-new-cloud-variety). The Society advised Pretor-Pinney to gather scientific justification for the creation of a new cloud type and if there was enough evidence, they could develop a proposal to have the new cloud type considered for inclusion in the International Cloud Atlas.

After Graeme Anderson, a student at the University of Reading, wrote a dissertation on the proposed new cloud type in 2010, a WMO team tasked with identifying the needs of the new International Cloud Atlas assessed the legitimacy of asperatus for inclusion. In November 2013, they had formulated a definition of the cloud:

"A formation made up of well-defined, wavelike structures in the underside of the cloud, more chaotic and with less horizontal organization than undulatus. Asperatus is characterised by localized waves in the cloud base, either smooth or dappled with smaller features, sometimes descending into sharp points, as if viewing a roughened sea surface from below. Varying levels of illumination and thickness of cloud can lead to dramatic visual effects."

Dr Roger Atkinson of the WMO stated that the chances of asperatus being adopted is "very high, but we cannot be certain” and furthermore “whether it’s going to be called asperatus is another matter. We need to receive advice from a proper latin scholar."

The orginal RMetS news article and subsequent features can be found here >>



More news stories can be found here >>



A time-lapse of the cloud can be viewed here >>