Undulatus asperatus over Tallinn, Estonia.
|Genus||Unknown, but examples are likely to be classified as either altocumulus or stratocumulus depending on height as asperatus is thought to be a cumuliform structure |
|Species||Unknown, but likely to be classified as stratiformis for genera stratocumulus and altocumulus.|
|Variety||Unknown, but likely to be classified as undulatus or separately as asperatus.|
|Altitude||Below 2,000 (or higher with altocumulus) m
(Below 6,000 -or higher with altocumulus- ft)
|Precipitation cloud?||No, but may form near storm clouds.|
Undulatus asperatus (or alternately, asperatus) is a cloud formation, proposed in 2009 as a separate cloud classification by the founder of the Cloud Appreciation Society. If successful it will be the first cloud formation added since cirrus intortus in 1951 to the International Cloud Atlas of the World Meteorological Organization. The name translates approximately as "roughened or agitated waves".
The clouds are most closely related to undulatus clouds. Although they appear dark and storm-like, they tend to dissipate without a storm forming. The ominous-looking clouds have been particularly common in the Plains states of the United States, often during the morning or midday hours following convective thunderstorm activity. As of June 2009[update] the Royal Meteorological Society is gathering evidence of the type of weather patterns in which undulatus asperatus clouds appear, so as to study how they form and decide whether they are distinct from other undulatus clouds.
History of observations
On June 20, 2006 Jane Wiggins took a picture of asperatus clouds from the window of a downtown office building in Cedar Rapids, Iowa. In March 2009, Chad Hedstroom took a picture of asperatus clouds from his car near Greenville Ave in Dallas, Texas. Soon after taking it, Wiggins sent her Cedar Rapids image to the Cloud Appreciation Society, which displayed it on its image gallery. Wiggins' photograph was posted on the National Geographic website on June 4, 2009. On July 23, 2013, Janet Salsman photographed them along the South Shore of Nova Scotia, Canada. On October 28, 2013, an Undulatus asperatus cloud layer formed over Tuscaloosa, Alabama. 
Since 2006, many similar cloud formations have been contributed to the gallery, and in 2009 Gavin Pretor-Pinney, founder of The Cloud Appreciation Society, began working with the Royal Meteorological Society to promote the cloud type.
- "June 2009". The Cloud Appreciation Society. Retrieved 2012-12-20.
- "PICTURES: New Cloud Type Discovered?". National Geographic News. 2009-06-03.
- "Asperatus: gathering storm to force new cloud name". London: The Guardian. 2009-06-02. Retrieved 2010-03-28.
- Luke Salkeld (2009-06-02). "The cloud with no name: Meteorologists campaign to classify unique 'Asperatus' clouds seen across the world". Daily Mail.
- "New Cloud Type Discovered: ‘Undulus Asperatus’". Meteorology News. 2006-04-28. Retrieved 2012-12-20.
- MICHAEL J. CRUMB (2009-06-11). "Iowa Woman's Photo Sparks Push for New Cloud Type". Associated Press.
- "Cloud Photos". The Cloud Appreciation Society. Retrieved 2012-12-20.
- James Spann https://plus.google.com/108868884822043573742/posts/gBbvhByxGW8
Media related to Undulatus asperatus at Wikimedia Commons