Halos

Auroras may grace the polar skies at night, but the day sometimes brings phenomenal halos and sundogs. It’s hard to describe the intangible beauty of these phenomena – vibrant spots of rainbow on either side of the sun, glowing pillars of light from the sun, a brilliant stream of light encircling the sky parallel to the horizon…a good display is simply awe-inspiring.

In general atmospheric optical phenomenon (sundogs, halos, rainbows) are not uncommon. Frequent halos and sundogs can be seen around the world when ice crystals in the atmosphere reflect and refract light. Infrequent halos are more often seen in polar regions or at high elevations with colder temperatures and more ice in the atmosphere. A common occurrence with halos is “Diamond Dust” which is essentially a ground level ice cloud filling the air with glittering ice crystals.

All photos below were taken by me, click on any of the images to open the full photo with caption.


The different crystal shapes generate different optics, however ice crystals form in hexagonal symmetry, thus while the crystal might be long or short (columnar or plate-like) the internal angles are always the same. Here at Summit the ICECAPS project, housed primarily in the MSF, is researching these crystals and cloud formations to better understand the complex processes involved in these systems.

The following website is a brilliant source of information regarding atmospheric optics and identifying features: www.atoptics.co.uk. An impressive full list of optical phenomenon can be found here: https://wikipedia.org/Atmospheric_optical_phenomena. For more Summit specific photos and information check out the Polar Field Services blog, Field Notes.

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Photograph of a good halo display – 22° halo, upper tangent arc, 46° halo, and parhelic circle at Summit Station, Greenland

 

Below are some of my favorite photos of optics that I have witnessed in the Arctic and Antarctic. If only I’d had my wide angle lens in past seasons! Click on images to bring up caption and full picture.

 

According to atoptics.co.uk, 120° parhelia are infrequent, but not super rare. They are often faint and short lived however, I have only ever seen them twice. Below is a panorama at Summit showing bright 120° parhelia.

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Bright sundogs, 22° halo, and definite rare 120° parhelia! (Summit)

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Looking opposite the previous photo – the 120° parhelia can be seen along the parhelic circle (Summit)

Moon halos are not uncommon either, but require a nearly full moon and darkness as well as halo forming conditions.

 

Other interesting optical phenomena include the green flash and fogbows. The green flash lasted a few hours at the South Pole Station in 2013 (check out my post from that sunset with more green flash photos here). This photo was taken through a telescope. It’s a bit blurry due to heat waves and light distortion near the horizon, the same process which causes the green flash to be visible. Fog and fogbows are a frequent occurrence at Summit, Greenland.

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 Happy belated equinox and sunrise at Pole!

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