Sundogs: Bright spots on either side of the sun.

With the Sun as its canvas, the sky weaves some of the most spectacular atmospheric tales. Sundogs, those elusive bright spots flanking our star, are a chapter in this narrative of sky optics. But what paints these twin strokes of light on either side of the sun? Have they signalled fortune since the times of Edward IV of England, or, as the ancients believed, do they portend weather changes?

These atmospheric optical phenomena, also known as mock suns or parhelia, aren’t as popular as their cousin the rainbow but are observed with more frequency. Subtly coloured, they are best seen when the Sun lounges near the horizon, appearing as a pair at approximately 22 degrees to the left and right. To the naked eye, sundogs may seem like celestial echoes of the solar body, red-tinted near the Sun fading to blues outwardly.

From Aristotle’s scripts to Stephen King’s fiction, sundogs have punctuated literature and history with their mystical presence. Under the guise of weather phenomenon, these sky optics hint at the atmospheric conditions favourable for their creation. And while the same ice crystals that cast sundogs also craft the circumzenithal arc, each display is a unique atmospheric story waiting to be read.

Stretching beyond Earth’s atmosphere, even the vistas of Mars may behold sundogs formed by alien crystals. With sky phenomena like halos, moon dogs, and sun pillars associated with the presence of sundogs, looking upwards has never been more enchanting. But beyond their beauty, these phenomena whisper upcoming weather patterns—often indicating rainfall within a day.

Steeped in myth and sprinkled with science, sundogs are a compelling weather phenomenon to observe and understand. As part of the halo family, they contribute to the grand tapestry that is our sky, setting the stage for an awe-inspiring experience that challenges the bounds of Earth and extends into the cosmos.

Understanding Sundogs: A Spectacular Sky Phenomenon

Sundogs, or parhelia, are intriguing visual spectacles in the sky, primarily caused by the refraction of light through hexagonal ice crystals found in cirrus clouds. These fascinating phenomena form bright spots that are approximately 22 degrees to the left or right of the sun, often manifesting vibrant colours remarkably akin to a distilled rainbow.

The Science Behind the Formation of Sundogs

The formation of sundogs involves a complex interplay of light and ice. Light rays enter the side face of hexagonal ice crystals and exit through another, bending or refracting in the process. This refraction results in sundogs appearing at about 22 degrees from the sun. Each colour within the sundog’s spectrum undergoes a slightly different degree of refraction, leading to their distinctive red and blue tinges.

Where and When to Witness Sundogs in the Sky

Sundogs are best observed when the sun is low on the horizon, typically at sunrise or sunset. This atmospheric condition maximises the meteorological potential for these ice crystals to catch the sunlight at the correct angle. Although prevalent in colder climates due to the abundance of ice crystals, sundogs can occur globally wherever cirrus cloud formations are present.

Common Myths and Misconceptions about Sundogs

One prevalent myth is the confusion between sundogs and other related phenomena such as halos. Unlike halos, which encircle the sun, sundogs appear as coloured patches on either side of the sun. Some folklore also romanticizes sundogs as weather predictors, although their appearance alone does not suffice for meteorological forecasts.

The phenomenology of sundogs, coupled with their rich tapestry in myths and scientific exploration, continues to fascinate both the scientific community and enthusiasts alike. By understanding the precise mechanisms such as refraction and the role of ice crystals, one not only appreciates these naturally occurring masterpieces but also gains insights into broader meteorological phenomena.

Sundogs vs. Solar Halos: Distinguishing Between Sky Optics

Understanding the difference between solar halo and ice halo scenarios, both spectacular instances of atmospheric optical phenomenon, begins with grasping how sunlight interacts with ice crystals in the atmosphere. While they share some common elements, each has distinct characteristics and implications for weather prediction and natural beauty.

Sundogs, or parhelia, form about 22 degrees to the left or right of the sun. These bright spots emerge due to sunlight bending, or refracting, as it passes through hexagonal ice crystals found in high cirrus clouds. The specific angle at which the light is refracted leads to the formation of colorful spots on either side of the sun, akin to a fragmented rainbow.

In contrast, a solar halo appears as a majestic circular ring around the sun, with a constant radius of approximately 22 degrees. This phenomenon also results from the refraction of light through ice crystals—similarly found in cirrus clouds—but differs in that the crystals’ orientation allows for a continuous, luminous ring instead of separated bright spots.

Both sundogs and solar halos signal the presence of ice crystals in the atmosphere, hinting at changing weather conditions, potentially signifying impending precipitation.

To aid in distinguishing these two phenomena visually, consider the following comparative insights:

Both sundogs and solar halos are profound reminders of the intricate interplay between light and the Earth’s atmosphere. While sundogs paint fleeting strokes of brilliance at dawn or dusk, solar halos encircle the sun with a ghostly glow, each an emblem of the ethereal beauty of atmospheric optics.

The Role of Ice Crystals in Creating Sundogs

Sundogs, an enchanting sky optics spectacle, owe their existence to the fascinating interplay of ice crystals and refraction. These ethereal light displays are not only a visual treat but also significant in the field of meteorology. Let’s delve into the science that shapes these stunning optical phenomena.

Hexagonal Ice Crystals: The Natural Prisms

At the heart of sundog formation are hexagonal ice crystals, typically found in high-altitude cirrus clouds or as ground-level diamond dust in colder climates. These plate-shaped crystals act as natural prisms, bending or refracting sunlight that passes through them. The specific angle of deviation, about 22°, is crucial for creating the vivid and colourful arcs often seen flanking the sun.

Sundogs are enhanced by the particular orientation and rotational positions of these ice crystals. As light passes through these hexagonal plates, it splits into its spectral components, similar to a rainbow. The colors range from deep reds at the side nearest to the sun, transitioning to blues and pastel greens further out. This color separation is primarily due to each wavelength of light being refracted slightly differently.

Here’s another intriguing aspect―the size and the wobble of ice crystals impact the visibility and vividness of sundogs. Larger crystals wobble more as they fall through the atmosphere, spreading the light over a larger area and making the sundog appear taller and more pronounced.

Atmospheric Conditions Favourable for Ice Crystal Formation

The formation of these magical ice crystals necessitates specific meteorological conditions. These conditions are predominantly found in colder regions and during the winter months when moisture high in the atmosphere freezes into tiny ice crystals. For sundogs to form, it is essential that these crystals are suspended in the atmosphere, aligning horizontally. The alignment and even distribution of these crystals are paramount for the clear visibility of sundogs.

Additionally, atmospheric phenomena like contrails, the clouds formed by the exhaust of aircraft engines, can also become the breeding grounds for sundogs. If these contrails contain a high concentration of ice crystals or supercooled water droplets, they can display vivid halos remarkably similar to those produced by natural cirrus clouds.

To learn more about rare and mesmerizing cloud formations that contribute to sky optics, consider exploring this detailed guide on the rarest clouds.

In essence, the interplay between cold, moisture, and light within our atmosphere creates an array of stunning visual phenomena. Sundogs are a brilliant example of how the natural world can illuminate our skies under the right conditions, providing not only a visual feast but also insights into the workings of our atmosphere.

Predicting Weather with Sundogs: Meteorological Implications

For those with an eye on the sky, sundogs are more than just a brilliant weather phenomenon; they serve as a natural indicator of impending meteorological changes. Casting a keen glance towards these luminous companions of the sun, you can discern vital clues about future weather patterns. In the diverse climatic canvas of Australia, seeing sundogs might suggest that moisture-laden systems are on the horizon, hinting at potential rain or snow within the next 24 hours. As such, these atmospheric spectacles, formed through the intricate dance of sunlight and ice crystals in the sky, have earned their place as a trusted, short-term forecast tool.

Historically, sundogs have painted the skies around 3-8 times a year, especially where the cirrus or cirrostratus clouds form a diaphanous veil. The hexagonal ice crystals, acting as natural prisms suspended high above the ground, bend the sunlight by approximately 22 degrees, giving rise to these ethereal arcs. While their ephemeral rainbow colours evoke awe, the orientation of these plate-shaped ice crystals also tells a tale of the weather narrative set to unfold. Fascinations with these sky paintings are not relegated to recent times, as even Shakespeare referenced the arresting beauty of sundogs, a testament to their enduring captivation.

In the context of the severe weather that thunderstorms bring, understanding the implications of sundogs becomes even more critical. As researchers delve into the nuances of Arctic climates and the larger global climate mechanisms, the insights gleaned from observations of sundogs enrich the collective knowledge on energy balance, air pressure variations, and wind patterns, which altogether shape the planet’s weather dynamics. Embracing the knowledge that these dazzling skyward signals can impart not only connects us to the mythos of ancient cultures but also enhances our ability to anticipate and prepare for the meteorological certainties and surprises of tomorrow.

Source Links

• Sun dog
• What Causes Halos, Sundogs and Sun Pillars?
• What Are Sundogs? Rainbows Beside the Sun!
• What Is a Sun Dog?
• Sundogs & Sun Altitude
• Secrets of the Sun Dog: halos, parhelion and sky phenomena
• Halos, Sundogs, and Light Pillars
• Have You Seen It? The Astonishing Sun Halo Phenomenon Explained – Consett Magazine – Positive Local News for Consett, County Durham
• Sundog Formation
• Image of the Week – Who let the (sun)dogs out?
• OPOD – Icy Contrails
• Sundog!
• The Science of Arctic Weather and Climate