Other special clouds - 3.2.2022 at 14.35 Espoo Observation number 104374

Visibility IV / V

Panu Lahtinen, Krista Wright, Pollux, Aalto-yliopisto

For a long time, a fairly clean hole cloud. In the rain streaks for a while, a piece of halo also stood out, with a hint of color in the picture.

Added a second image version with increased saturation and contrast. The residues of the halo stand out a little better.

This description has been automatically translated from Finnish. Click here to see the original text.

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Additional information

Havainto
- Other special clouds
Cloud coverage in the sky
- Covered 1/8 of the sky

Other special clouds
- Fallstreak hole
  
  Fallstreak hole (Hole punch cloud) is a rare phenomenon observed in cloud cover.
  
  Altocumulus clouds consist mainly of subcooled cloud droplets, which can be well below freezing, but which have not yet frozen in the absence of suitable freezing cores.
  
  When freezing nuclei, such as small ice crystals, come into contact with the cloud, the droplets of clouds may begin to freeze outward from this point so that an annular opening appears to form in the cloud. Such an opening is called a hole cloud.
  
  One source of freezing cores may be airplanes that create a cloud of holes as they pass through the altocumulus layer. Hole clouds can also be oblong in shape when the aircraft has flown a little longer at cloud height. In this case, ice crystals floating down from the opening remains in its path. In the middle of these openings or canals, a thin line of ice crystals, or Virga, visible below the cloud layer, can typically be seen. If the sun happens to be at a suitable distance from this rain line, a halo phenomenon, such as a side sun, can be detected in the wake.
  
  A hole cloud formed in the Altocumulus layer with a rain line of ice crystals, or Virga, in the middle. Image by Jari Luomanen.

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Other special clouds - 3.2.2022 at 14.35 Espoo Observation number 104374