Asperitas, also known as Undulatus asperatus, is a unique cloud formation characterized by wave-like structures in the underside of the cloud. Gavin Pretor-Pinney, the founder of the Cloud Appreciation Society, popularized it as a new cloud type in 2009. In March 2017, the International Cloud Atlas added Asperitas as a supplementary feature, making it the first cloud formation to be included since Cirrus intortus in 1951. This article provides an overview of Asperitas, its definition, history of observations, and characteristics.
Definition of Asperitas Cloud
Asperitas is a cloud formation that appears as localized waves in the cloud base. It is characterized by its chaotic and less organized wave-like structures, which are smoother or dappled with smaller features. The cloud base can descend into sharp points, resembling a roughened sea surface viewed from below. Asperitas often occurs with Stratocumulus and Altocumulus, and varying levels of illumination and thickness of the cloud can create dramatic visual effects.
History of Observations
Asperitas was first observed on June 20, 2006, by Jane Wiggins in Cedar Rapids, Iowa, who sent her picture to the Cloud Appreciation Society’s image gallery. Since then, many similar cloud formations have been contributed to the gallery. In 2009, Gavin Pretor-Pinney worked with the Royal Meteorological Society to promote Asperitas as a new type of cloud. Margaret LeMone, a cloud expert with the American National Center for Atmospheric Research, had also taken photos of Asperitas clouds for 30 years, considering it a new cloud type. Asperitas clouds have been observed in many locations worldwide, including Canada, the United States, and New Zealand.
Characteristics of Asperitas Cloud
Although Asperitas clouds appear dark and storm-like, they usually dissipate without forming a storm. They are closely related to Undulatus clouds and have more chaotic and less organized wave-like structures. Asperitas clouds are commonly observed in the Plains states of the United States, often during the morning or midday hours following convective thunderstorm activity.