 EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes
and phenomena which shape our planet and our lives. EPOD will collect and
archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


 Fall-streak and Circumzenithal Arc

   June 14, 2021

    Arco-Circumzenitale

   Photographer:  Marco Meniero

   Summary Author:  Marco Meniero

   Featured above is a colorful  circumzenithal arc and a
    fall-streak observed from Civitavecchia (Rome), Italy, below the
   approach path of the Fiumicino Airport. Fall-streak holes occur in
   cloud decks ( altostratus clouds, for example) where the droplets of
   liquid water that compose them are in a  supercooled state; that is
   they remain in liquid even if the air temperature is well below the
   freezing point of water (0 ° C). However, an aircraft passing through
   the cloud layer can cause the supercooled droplets to suddenly freeze,
   resulting in a cascade of  ice crystals. When these crystals become
   sufficiently heavy, they’ll detach from the cloud and fall, leaving a
   void in the cloud layer –  a hole in the sky. In this case, the
   falling crystals were oriented so that sunlight entered their uppermost
   horizontal faces and exited through one of their vertical side faces,
   forming this charming circumzenithal arc. Note also the  cloud
   iridescence near the bottom of the photo.

   Both climbing and descending aircraft will trigger fall-streaks in
   shallow cloud decks, which explains why such voids are often seen in
   the vicinity of busy airport runways. Photo taken on April 12, 2021.
     * Fiumicino Airport, Italy Coordinates:  41.7999,12.2462

Related EPODs

    Fall-streak and Circumzenithal Arc  Archive - Red Rose and
   Morning Dew  Northern Lights Above the Lofoten Islands of Norway
    Sunrise and Sunset Skies  Strong Storms Over the Olympic
   Mountains  Surprise on the Tyrrhenian Sea
    More...

Atmospheric Effects Links

     *  Atmospheric Optics
     *  Color and Light in Nature
     *  The Colors of Twillight and Sunset
     *  Refraction Index
     *  Image Gallery: Atmospheric Effects
     *  What is a Rainbow?

-
   Earth Science Picture of the Day is a service of the  Universities
   Space Research Association.

https://epod.usra.edu
 
