rare halos over Switzerland

Last updated on September 16, 2023

Rare Halos Over Switzerland: A Spectacular Atmospheric Phenomenon

Switzerland, known for its breathtaking landscapes and natural wonders, has recently witnessed a mesmerizing display of rare halos in its skies. These captivating optical phenomena, captured by photographer Ken Jay near Zermatt, have left viewers in awe. The images showcase a combination of unique halos, including the elusive diamond dust halo and a rarely seen 46° halo. Let's delve deeper into the enchanting world of these rare halos and explore the scientific explanations behind their occurrence.

The Diamond Dust Halo: A Spectacular Rarity

One of the highlights of the captured images is the presence of a diamond dust halo. This ethereal halo forms when tiny ice crystals, known as diamond dust, float in the air. These crystals act as prisms, bending and refracting sunlight to create a stunning display of colors. The diamond dust halo observed in Switzerland is particularly rare, as it appears at a solar altitude of approximately 7°. Its circular shape distinguishes it from other halos and adds to its allure.

The Elusive 46° Halo: A Circular Marvel

Among the array of halos captured in Switzerland, the 46° halo stands out as an exceptional rarity. This perfectly circular halo is situated far from the uppermost circumzenithal arc, which makes it even more captivating. Often mistaken for the supralateral arc, the 46° halo is formed by horizontally aligned ice crystals known as Parry crystals. These crystals create a "V" shaped arc that curves towards the sun, accompanied by a faint suncave Parry arc above it. The position and shape of these rare halos change dynamically as the sun's altitude fluctuates.

Parry Supralaterals: A Delicate Emanation

The montage of images reveals another astonishing phenomenon known as Parry supralaterals or Tape arcs. Named after halo expert Walter Tape, these halos manifest as brighter smudges on the 46° halo. Parry crystals, responsible for their formation, produce delicate arcs that add an element of mystique to the overall display. More images featuring these mesmerizing Tape arcs will be showcased in an upcoming OPOD (Optical Phenomena of the Day) feature.

Helic Arcs: Sunlit Glints of Wonder

The rare halos observed in Switzerland also include helic arcs, which are glimmers of sunlight externally reflected from the side faces of ice crystals. These captivating arcs contribute to the overall enchantment of the atmospheric display. The interplay of light and crystal orientation produces these delicate glints that embellish the sky with their ephemeral beauty.

The Role of Snow Cannons: Unveiling the Elusive Halos

An intriguing factor that likely contributes to the visibility of these rare halos in Switzerland is the presence of snow cannons. The photographs were taken in close proximity to a site where snow cannons were operating throughout the day, creating artificial snow. The ice crystals nucleated by these snow machines, combined with the natural growth downwind, provide ideal conditions for the formation of these extraordinary halos. Prior to the regular use of snow guns, such halos were primarily observed in Antarctica, making their appearance in Switzerland all the more extraordinary.

In conclusion, the rare halos observed over Switzerland offer a captivating glimpse into the wonders of atmospheric optics. From the elusive diamond dust halo to the perfectly circular 46° halo and the delicate Tape arcs, each phenomenon adds its own touch of magic to the sky. These optical marvels, created by ice crystals and sunlight, remind us of the intricate beauty that lies within our natural world. The presence of snow cannons in Switzerland has unveiled these rare halos, allowing us to witness their splendor firsthand. Let us continue to marvel at the awe-inspiring phenomena that grace our skies and inspire us to explore the mysteries of our atmosphere.

Rare Diamond Dust Halos, Switzerland

Ken Jay took the images and made a montage. The display was at Tuftern, close to Zermatt. The Matterhorn juts upwards between the sun and the right hand sundog. December 18, '08 with a sun ~7� high. Images ©Ken Jay, shown with permission.

The outer halo is a rare 46� halo, truly circular and at this solar altitude far from the uppermost circumzenithal arc. The more common supralateral arc, oft mistaken for a 46� is weak as is the upper tangent arc from the same horizontal column crystals.

Parry oriented crystals produced a �V� shaped arc convex to the sun and above it a faint suncave Parry arc. The shape and position of these two rarities change quickly as the sun�s altitude alters.

Parry crystals produced two even more rare halos. One is just visible in the montage as brighter smudges on the 46� halo. These are Parry supralaterals or Tape arcs named after halo expert Walter Tape. More images in a forthcoming OPOD feature.

The other Parry generated rarity are helic arcs � glints of sunlight externally reflected from crystal side face.

"Snow cannons were operating all day less than 1 kilometre from the site of photograph."

That's probably the key to the visibility of these rare halos. Before snow guns were regularly used they were seen only in Antarctica. Ice crystals nucleated by snow machines and growing downwind of them produce some wonderful halos.

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