Pileus Clouds
smooth capping clouds

Pileus (Latin for "skullcap") is a smooth cloud found attached to either a mountain top or growing cumulus tower.

Photograph by: Manikin

The lifted air that produces pileus clouds is typically drier than the moist air from lower levels often responsible for cumulus clouds. There is little tendency for any significant vertical growth in pileus clouds, which is why they take on a smoother, horizontal shape.

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Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.