Cryospheric Sciences

Did you know about… nature’s street lights for Santa Claus?

Fig. 1: Light pillars over Fairbanks, Alaska [Credit: Daniel Neal]

Only a couple of days left until Santa Claus’ big night! Once again the beardy guy in the red and white suit will fly around the world with his sledge pulled by his strong reindeers to make young and old children happy! But how does he navigate in the dark? Luckily, nature provides some solutions, for example light pillars…

Light pillars form when ice particles are suspended in the air. These particles can be found at high altitudes in the form of cirrus clouds as well as near the surface in the form of blowing snow, ice fog or diamond dust.

The ice crystals of interest for the formation of light pillars usually have a flat and hexagonal shape, so that they tend to fall rather horizontally through the air. Each crystal is like a small mirror and reflects light sources positioned below (see Fig. 2). As the crystals are distributed throughout the vertical atmospheric column, the reflection appears like a pillar.

Fig. 2: Light pillar schematic [Credit: V1adis1av via Wikimedia Commons]

Light pillars therefore form when two conditions are met:

  • there is a low light source: the setting or rising Sun, the Moon, artificial light
  • the flat and hexagonal ice crystals are present in the air

As can be seen in our Fig. 1 and Fig. 2, the strength and colors of artificial light sources, such as street lamps, lead to very impressive light pillars! Good for Santa! It must feel like street lights in the sky! 🙂

Fig. 3: Light pillars at Cambridge Bay Airport. [Credit: E. van Lochem via Wikimedia Commons]

The EGU Cryosphere Blog Team wishes you a merry Christmas and happy New Year!

See you in January!

Further reading

Edited by Violaine Coulon

Clara Burgard is a postdoctoral researcher at the Institut des Géosciences et de l'Environnement (IGE) in Grenoble. She currently investigates melt parametrizations at the base of Antarctic ice shelves as part of the H2020 PROTECT project. Before that, she did her PhD on investigating sea ice in climate simulations and comparing it to sea ice observed by satellites. She tweets as @climate_clara.

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