WW2010
University of Illinois

WW2010
 
  welcome
 
> online guides
 
  archives
 
  educational cd-rom
 
  current weather
 
  about ww2010
 
  index

Online Guides
 
  introduction
 
> meteorology
 
  remote sensing
 
  reading maps
 
  projects, activities

Meteorology
 
  introduction
 
  air masses, fronts
 
> clouds, precipitation
 
  el nino
 
  forces, winds
 
  hurricanes
 
  hydrologic cycle
 
  light, optics
 
  midlatitude cyclones
 
  severe storms
 
  weather forecasting

Clouds, Precipitation
 
  introduction
 
  mechanisms
 
  precip processes
 
  high level clouds
 
  mid level clouds
 
  low level clouds
 
  vertically developed
 
> other cloud types

Other Cloud Types
 
  contrails
 
  billow clouds
 
  mammatus
 
  orographic
 
> pileus

User Interface
 
  graphics
> text

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Pileus Clouds
smooth capping clouds

Pileus (Latin for "skullcap") is a smooth cloud found either at the top of or attached to a mountain or a growing cumulus tower. Pileus clouds form when air at higher levels is forced to rise. In the photograph below, a pileus cloud is attached to the top of a cumuliform cloud.

[Image: pileus attached to cumuliform cloud top (88K)]


The air that is lifted to form the pileus clouds is drier and consequently has a much higher lifting condensation level than does the moist air from lower levels often responsible for cumulus clouds. Therefore, there is little tendency for any significant vertical growth in pileus clouds, which is why the cloud takes on a smoother horizontal shape.


Terms for using data resources. CD-ROM available.
Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.