Hole in Cloud Deck

April 08, 2005

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Provided by: Mel Grunau
Summary authors & editors: Jim Foster; Mel Grunau

This eye-opening cloud photo was taken over Berea, Ohio on November 12, 2004. Shallow cloud decks can on occasion have "holes," which are essentially areas where localized precipitation has occurred. Water droplets or ice crystals (or a mixture of both) compose clouds, and while in most cases precipitation isn't released here and there, under certain circumstances rain or snow can be forced out of a particular part of a cloud deck. Cloud seeding by silver iodine or carbon dioxide could form a hole for example, or even ice falling off an aircraft can induce precipitation. The indistinct gray patch in the center of the hole of this altocumulus cloud bank is likely virga (precipitation that evaporates before reaching the surface). In essence, the cloud area that produced the virga has relinquished its liquid and is thus no longer visible as a cloud.

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