Cloud enthusiast, Cary Bahora, recently drew our attention to this video asking what the phenomenon shown was called.

Gavin Pretor-Pinney explained “The wave formations here are often described as gravity waves. The cloud type would best be described as stratocumulus undulatus. But there are also examples of the cloud ‘supplementary features’ called mamma and asperitas. Asperitas is a classification that came out of the Cloud Appreciation Society, this isn’t a classic asperitas but probably is an example of it”.