WW2010
University of Illinois

WW2010
 
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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
 
  development
 
> cloud types
 
  precipitation

Cloud Types
 
  introduction
 
> high-level clouds
 
  mid-level clouds
 
  low-level clouds
 
  vertically developed
 
  other cloud types

High-Level Clouds
 
  cirrus
 
> cirrostratus

User Interface
 
  graphics
> text

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Cirrostratus Clouds
sheet-like and nearly transparent

Cirrostratus are sheet-like, high-level clouds composed of ice crystals. Though cirrostratus can cover the entire sky and be up to several thousand feet thick, they are relatively transparent, as the sun or the moon can easily be seen through them. These high-level clouds typically form when a broad layer of air is lifted by large-scale convergence.

[Image: halo through the cirrostratus clouds (58K)]
Photograph by: Rauber
Sometimes the only indication of their presence is given by an observed halo around the sun or moon. Halos result from the refraction of light by the cloud's ice crystals. Cirrostratus clouds, however, tend to thicken as a warm front approaches, signifying an increased production of ice crystals. As a result, the halo gradually disappears and the sun (or moon) becomes less visible.

When the sun is low on the horizon, cirrostratus clouds can appear in a magnificent array of colors as longer wavelengths of sunlight (red, yellow, and orange) are reflected off of the clouds.

[Image: thickening cirrus and cirrostratus at sunset (57K)]
Photograph by: Knupp
The cirrus streaks in this photograph are aligned in a southwest to northeast direction, indicative of warmer air advancing at higher levels. Lower on the horizon, thickening cirrostratus clouds effectively hide the sun, signifying changing weather ahead. As the warm front approaches, these clouds will thicken and be replaced lower and more dense cloud types.



cirrus
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.

Mid-Level Clouds