Altocumulus clouds form above 18,000 feet (5500 meters). The mackerel sky appearance reveals the rising and falling of many air parcels across a small distance.
Altocumulus cloud (DI00872), Photo by Caspar Ammann
Caspar Amman
University Corporation for Atmospheric Research (UCAR)
image
Clouds
NCAR/UCAR Image and Multimedia Gallery
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DI00872
http://n2t.net/ark:/85065/d7g15xv3
