Ski Slope Halos, France - OPOD

Last updated on September 16, 2023

Ski Slope Halos: A Dazzling Display of Atmospheric Optics in France

Have you ever witnessed a breathtaking display of ice halos while skiing? One such spectacle occurred at Saint Jean D'Aulps, France, on December 31st, '14. The images captured by Saskia Koper-Groenevelt showcase the mesmerizing beauty of ski slope halos. These halos, formed by almost optically perfect hexagonal prism ice crystals, are a splendid by-product of snow cannons used to promote snow formation.

The process of halo formation begins with the emission of tiny seed nuclei by snow cannons. As these nuclei drift downwind, they serve as the foundation for the growth of hexagonal prism ice crystals. These crystals possess near-perfect optical properties, giving rise to the dazzling display of halos. The abundance of Parry oriented crystals in this particular display adds to its uniqueness.

The image captured by Saskia Koper-Groenevelt reveals several fascinating features of ski slope halos. Among them is a rare occurrence known as a suncave Parry, which adds a touch of rarity to the already captivating display. Additionally, the image showcases even rarer phenomena such as helic arcs and Parry supralaterals. These intricate formations demonstrate the intricate nature of atmospheric optics and the astonishing variety of halos that can be observed.

Intriguingly, there may also be a trace of upper and reflected Lowitz arcs present in the image. These arcs, if confirmed, would further enhance the complexity and beauty of the halo display. To better understand the formation and characteristics of ski slope halos, HaloSim ray tracing has been employed. This simulation accurately reproduces the observed halos, allowing for a detailed analysis and labeling of the different halo types present in Saskia's image.

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In conclusion, the ski slope halos observed at Saint Jean D'Aulps, France, offer a captivating glimpse into the world of atmospheric optics. The almost optically perfect hexagonal prism ice crystals formed downwind of snow cannons create a dazzling display of halos. From the rare suncave Parry to the elusive helic arcs and Parry supralaterals, these halos showcase the immense beauty and complexity of nature's optical phenomena. Whether you're an avid skier or simply a lover of natural wonders, witnessing ski slope halos is an experience that will leave you in awe of the wonders of our atmosphere.

Ski Slope Halos ~ Dazzlingly bright ice halos at Saint Jean D'Aulps, France. Imaged by Saskia Koper-Groenevelt on 31st December, '14.

©Saskia Koper-Groenevelt, shown with permission

The halos are from almost optically perfect hexagonal prism ice crystals that slowly form downwind of snow cannons. The crystals grow on tiny seed nuclei emitted by the cannons. They are there to promote snow formation - Halo forming crystals are a splendid by-product.

This display - like others - is rich in Parry oriented crystals. We see a rare suncave Parry, even rarer helic arcs and Parry supralaterals.

There 'might' be a trace of upper and reflected Lowitz arcs.

The HaloSim ray tracing at left reproduces the halos. Those in Saskia's image are labelled in blue.

Note: this article has been automatically converted from the old site and may not appear as intended. You can find the original article here.

Reference Atmospheric Optics

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