OPOD - Dawn Sun Pillar

Last updated on September 16, 2023

OPOD - Dawn Sun Pillar: A Captivating Atmospheric Phenomenon

Sun pillars are a mesmerizing atmospheric optical phenomenon that can be observed during the dawn hours. These pillars create an illusion of a towering beam of light stretching vertically into the sky. However, upon closer examination, it becomes clear that this phenomenon is not caused by an actual sun ray shooting upwards. Instead, it is a result of the reflection of sunlight off countless tiny ice crystals suspended in the air.

The Illusion of a Sun Pillar

Sun pillars can reach incredible heights, sometimes extending more than 20 degrees vertically. This extraordinary height makes it easy to mistake them for rays of sunlight piercing through the atmosphere. But in reality, they are composed of millions of almost horizontal glints of light produced by minuscule ice crystals.

The Role of Ice Crystals

Both plate-shaped and column-shaped ice crystals can contribute to the formation of sun pillars. However, it is predominantly the large, irregularly shaped plate crystals that generate these captivating optical displays. As the low-angle sunlight interacts with these crystals, it glances obliquely from their undersides or reflects internally off their upper faces. The degree to which the crystals deviate from a horizontal orientation determines the height of the pillar.

The Science Behind Sun Pillars

Sun pillars are a manifestation of the interaction between sunlight and ice crystals in the Earth's atmosphere. When the sun is low on the horizon, its light passes through a greater thickness of the atmosphere, resulting in increased scattering. This scattering causes the light to disperse into various directions, including upwards. When this dispersed light encounters ice crystals, it reflects off them, creating the illusion of a vertical pillar.

Atmospheric Conditions and Sun Pillar Formation

Several factors influence the formation and appearance of sun pillars. These include:

• Temperature: Sun pillars are more likely to form in cold weather conditions when ice crystals are present in the atmosphere.
• Crystal Shape: The irregularly shaped plate crystals are particularly effective at producing sun pillars due to their wobbling motion.
• Crystal Orientation: The angle at which the ice crystals are suspended in the air determines the direction and height of the pillar.
• Sun Angle: Sun pillars are most commonly observed during sunrise or sunset when the sun is close to the horizon.

Capturing the Beauty of Sun Pillars

Photographers and sky enthusiasts often find sun pillars to be a captivating subject to capture. The vertical nature of these optical phenomena adds a dramatic element to sunrise or sunset photographs. To photograph a sun pillar, it is best to use a camera with manual settings to ensure proper exposure. Additionally, capturing the pillar against a contrasting sky can enhance its visibility and impact.

Appreciating Nature's Wonders

Sun pillars serve as a reminder of the intricate beauty and complexity of our atmosphere. These optical illusions, created by the interplay of sunlight and ice crystals, offer a glimpse into the fascinating phenomena that occur above us. By observing and understanding these natural wonders, we gain a deeper appreciation for the world around us and the marvels that nature has to offer.

Conclusion

Sun pillars are an awe-inspiring atmospheric optical phenomenon that can be observed during dawn hours. While they may appear as upward rays of sunlight, they are actually composed of countless horizontal glints of light reflected by ice crystals in the atmosphere. The height of the pillar is determined by the orientation and shape of these crystals. By delving into the science behind sun pillars and appreciating their beauty, we gain a greater understanding of the remarkable interplay between light and ice in our atmosphere.

Sunrise Pillar

A unusually tall pillar imaged by Leslie Ginn at Stockton, California. ©Leslie Ginn, shown with permission

Stretching vertically an incredible 20° plus it is hard to accept that this is not some bright upwards going sun ray.

That is an illusion. Sun pillars are actually composed of untold millions of nearly horizontal going glints from tiny ice crystals.

Both plate and column aspect ice crystals can produce pillars but most are from large, wobbly and imperfect plate shapes. The low sun glints very obliquely from their undersides or from an internal reflection off their upper faces. The greater the crystal wobble from horizontal the taller is the pillar.

The pillar illusion. There is no upward light. Instead the sun is glancingly reflected by myriad crystals.

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Reference Atmospheric Optics

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