Breathtaking photo shows an "ice halo" forming around the sun

While crossing a field of fresh snow earlier this month, Bastian Werner captured this stunning photo of an ice halo near Füssen, Bavaria, Germany after noticing that he had entered an ice fog.

Ice halos are breathtaking atmospheric phenomena produced by the refraction, reflection, and dispersion of light through ice crystals in the atmosphere.

These crystals, often found in high-level clouds, bend sunlight or moonlight, resulting in a variety of stunning optical effects, including rings, arcs, and spots in the sky.

Understanding ice halos not only enhances our appreciation of natural beauty but also contributes to meteorological knowledge.

Formation of ice halos

The formation of ice halos hinges on the presence of tiny, hexagonally-shaped ice crystals suspended in the atmosphere.

These crystals act like prisms and mirrors, bending and reflecting light. The specific shape and orientation of the crystals determine the type of halo observed.

When light passes through these ice crystals, it refracts or bends at specific angles. The most common angle is 22 degrees, which results in the well-known 22-degree halo.

However, other types of halos can form at different angles, depending on the ice crystal’s shape and orientation.

Types of ice halos

The 22-degree halo is a circular ring surrounding the sun or moon. It forms when light refracts through the hexagonal ice crystals in cirrostratus clouds.

Sundogs, or parahelia, are bright, colored spots on either side of the sun, often seen as part of the 22-degree halo. They occur when sunlight refracts through ice crystals with a vertical orientation.

Circumzenithal arcs are vividly colored, resembling an upside-down rainbow. They appear when sunlight refracts through horizontally oriented ice crystals high in the sky.

Light pillars appear as vertical columns of light extending above or below a light source, usually the sun or streetlights. They form in very cold conditions when flat ice crystals reflect light.

Observing this phenomenon

Ice halos are best observed when the sky is filled with cirrostratus clouds. These high-altitude clouds are thin and contain the ice crystals necessary for halo formation.

To safely observe ice halos, never look directly at the sun. Use polarized sunglasses to enhance the visibility of halos around the sun. For moonlit halos, a clear, crisp night is ideal.

Meteorologists often use the presence of ice halos as indicators of approaching weather fronts. The ice crystals in cirrostratus clouds can signify the advance of a warm front, potentially leading to precipitation.

Ice halos are not only a stunning natural spectacle but also a fascinating subject for scientific study. Their beauty and complexity remind us of the intricate interactions between light and the Earth’s atmosphere.

Whether you’re a casual observer or a meteorology enthusiast, understanding and appreciating ice halos can add a new dimension to your experience of the natural world.

Image credit: Bastian Werner

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