Asperatus

Last week we had some really interesting clouds here over Gothenburg. The light they give feels rather ominous and they have a very characteristic wavy underside. In the Cloud Appreciation Society these types of clouds are referred to as Asperatus and considered to be a class of its own different from the standard and well established types of clouds. This name and classification has not yet gotten widespread use outside of the society.

I didn't take any pictures of the clouds when they appeared but there are plenty of nice pictures in the Cloud Appreciation Society Gallery along with a little bit of discussion about this type of cloud.