Spokane Circumhorizon Arc II

Last updated on September 16, 2023

Spokane Circumhorizon Arc II: A Spectacular Atmospheric Phenomenon

Have you ever witnessed a mesmerizing display of colors in the sky that seemed to stretch endlessly? One such breathtaking phenomenon is the Spokane Circumhorizon Arc II. This captivating optical display occurs when sunlight interacts with ice crystals in the atmosphere, resulting in a vibrant and expansive halo that appears parallel to the horizon. While the original article showcased an image of the Spokane display on June 3, 2006, let's delve deeper into this extraordinary atmospheric event.

Understanding the Circumhorizon Arc

The Circumhorizon Arc, also known as the circumhorizontal arc or the fire rainbow, is a rare optical phenomenon that occurs in cirrus clouds. These clouds are composed of ice crystals, which act as prisms that refract sunlight. When the sun is high in the sky, its light enters these ice crystals at a specific angle, causing the light to disperse into its constituent colors. The result is a brilliant arc of colors, resembling a rainbow, that appears parallel to the horizon.

The Unique Characteristics of the Spokane Circumhorizon Arc II

The Spokane Circumhorizon Arc II is particularly notable due to its enormous extent and vivid colors. The arc spans a significant portion of the sky, creating a breathtaking spectacle for those fortunate enough to witness it. The colors are incredibly vibrant, ranging from deep reds and oranges to intense blues and purples. This combination of size and color intensity makes the Spokane display a remarkable example of this atmospheric phenomenon.

Factors Influencing the Appearance of the Spokane Circumhorizon Arc II

Several factors contribute to the occurrence and appearance of the Spokane Circumhorizon Arc II:

1. Latitude: The arc is more commonly observed at higher latitudes, where the sun's angle in the sky allows for optimal refraction through ice crystals.
2. Time of Year: The best chances of witnessing the arc are during the summer months when the sun is higher in the sky.
3. Time of Day: The arc is most visible during the midday hours when the sun's angle is optimal for creating the necessary refraction.
4. Cloud Type: Cirrus clouds, which are thin and wispy, provide the ideal conditions for the formation of the arc.
5. Ice Crystal Shape and Orientation: The shape and orientation of the ice crystals within the cirrus clouds play a crucial role in determining the size and appearance of the arc.

Similar Atmospheric Optical Phenomena

While the Spokane Circumhorizon Arc II is undoubtedly a stunning sight to behold, it is not the only atmospheric optical phenomenon that can leave us in awe. Here are a few other fascinating phenomena that share similarities with the Circumhorizon Arc:

1. Circumzenithal Arc: This arc appears as an upside-down rainbow, forming a halo directly above the sun. It occurs when sunlight interacts with plate-shaped ice crystals in cirrus clouds.
2. Supralateral Arc: This arc appears above or below the sun and is caused by sunlight refracting through horizontally-oriented ice crystals.
3. Parhelic Circle: This circular halo surrounds the sun and is formed by sunlight reflecting off hexagonal ice crystals.
4. Sun Dogs: These bright spots appear on either side of the sun and are caused by the refraction of sunlight through ice crystals in cirrus clouds.

Capturing the Magic: Photographing the Spokane Circumhorizon Arc II

Photographing atmospheric optical phenomena like the Spokane Circumhorizon Arc II can be a challenging yet rewarding endeavor. To capture this extraordinary event in all its glory, consider these tips:

• Use a wide-angle lens to capture the expansive nature of the arc.
• Position yourself in an open area with an unobstructed view of the sky.
• Pay attention to the sun's position and the angle of the arc to compose your shot effectively.
• Experiment with different camera settings, such as exposure and white balance, to achieve the desired effect.
• Be patient and observant, as atmospheric phenomena can be elusive and fleeting.

Conclusion

The Spokane Circumhorizon Arc II is a captivating atmospheric optical phenomenon that showcases the beauty and complexity of our natural world. Its immense size and vibrant colors make it a sight to behold, leaving onlookers in awe of nature's artistic prowess. By understanding the factors influencing its appearance and learning how to capture it through photography, we can fully appreciate the wonder and magic of this remarkable event. So, keep your eyes on the sky, for you never know when the next display of the Spokane Circumhorizon Arc II might grace us with its presence.

Another image of the Spokane display of June 3, 2006.

This one in Spokane Valley is by James and Dominick Giguere.

It illustrates well the halo's enormous extent and bright colours.

Image ©James and Dominick Giguere.

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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