Glory, aircraft shadow and cloudbow

Last updated on September 16, 2023

Glory, Aircraft Shadow, and Cloudbow: A Spectacular Atmospheric Display

Have you ever looked up at the sky and witnessed mesmerizing optical phenomena that left you in awe? From vibrant rainbows to shimmering halos, our atmosphere is filled with captivating displays of light. In this article, we will explore three fascinating atmospheric optics phenomena: glory, aircraft shadow, and cloudbow.

Glory: Rings of Color in the Clouds

One of the most captivating optical phenomena in the sky is the glory. Often observed from an aircraft or on top of a mountain, a glory appears as a set of concentric rings of colors surrounding the shadow of the observer. The rings are usually colored red on the outside and blue on the inside, with green and yellow in between. The colors are caused by diffraction, where light waves bend as they pass around tiny water droplets or ice crystals in the clouds.

Glories are formed when sunlight is scattered backwards by these small particles, creating interference patterns that result in the rings of color. The size of the droplets or crystals determines the size of the glory, with larger particles producing larger rings. Interestingly, glories can only be seen when the observer is situated between the cloud and the sun, allowing the backscattered light to reach their eyes.

Aircraft Shadow: A Spectral Companion

As you gaze out of an aircraft window, you may notice a dark shadow cast on the clouds below. This shadow, known as an aircraft shadow, follows the plane's trajectory and appears elongated due to the perspective from above. While it may seem like a simple shadow, the aircraft shadow can exhibit intriguing optical effects.

The aircraft's engine and nose shadows extend back to the plane but are typically only noticeable for short distances. This is because the shadow's visibility depends on factors such as the angle of sunlight, cloud density, and distance from the observer. At times, the shadow may appear distorted or fragmented, adding to the spectacle of the overall atmospheric display.

Cloudbow: A Delicate Arch in the Sky

Similar to a rainbow, a cloudbow is a circular arc of colors formed in the sky. However, unlike rainbows that are formed by sunlight refracting and reflecting within raindrops, cloudbows are created by diffraction within water droplets or ice crystals in clouds. Cloudbows are often seen when the sun is low on the horizon, casting its rays through thin clouds.

The colors of a cloudbow are usually fainter and less distinct compared to a rainbow. They tend to be pastel-like, with pale shades of red, orange, yellow, green, and blue. The size of the droplets or crystals influences the size and visibility of the cloudbow.

The Interplay of Light and Atmospheric Particles

Glories, aircraft shadows, and cloudbows all rely on the interaction between sunlight and atmospheric particles. These particles can be tiny water droplets or ice crystals suspended in the air. When sunlight encounters these particles, it undergoes various optical phenomena, resulting in the mesmerizing displays we observe.

The science behind these phenomena lies in the principles of diffraction and scattering. Diffraction occurs when light waves bend around obstacles or pass through narrow openings, causing interference patterns. Scattering refers to the redirection of light in different directions due to interactions with particles. Both processes play crucial roles in creating the intricate patterns of colors and shadows we see in the sky.

Exploring Beyond the Visible Spectrum

While glories, aircraft shadows, and cloudbows are primarily observed in the visible spectrum, there is much more to atmospheric optics beyond what our eyes can perceive. Infrared and ultraviolet radiation also interact with atmospheric particles, leading to additional phenomena such as infrared glories and ultraviolet corona.

Infrared glories, invisible to the naked eye, can be captured using specialized equipment that detects infrared radiation. These glories appear as rings of warmth surrounding the shadow of the observer. On the other hand, ultraviolet corona manifests as a set of concentric rings in the ultraviolet spectrum. Observing these phenomena requires ultraviolet-sensitive cameras or filters.

Embracing the Beauty of Atmospheric Optics

The study of atmospheric optics not only provides us with a deeper understanding of the science behind these captivating phenomena but also allows us to appreciate the beauty and complexity of our atmosphere. By unraveling the intricate interplay between sunlight and atmospheric particles, scientists and enthusiasts continue to uncover new insights and expand our knowledge of these fascinating optical displays.

So, next time you find yourself gazing up at the sky, take a moment to marvel at the glory, aircraft shadow, or cloudbow that graces the heavens above. Let yourself be captivated by the interplay of light and particles, and embrace the wonder of atmospheric optics.

Glory, aircraft shadow and cloudbow imaged by Leigh Hilbert as his aircraft from the Pacific Northwest descended into Waikiki, Oahu, Hawaii. The aircraft engine and nose shadows are extended, theoretically they extend all the way back to the aircraft but are only noticeable for short distances. Another image at a higher altitude is here. Image ©Leigh Hilbert , shown with permission.

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Reference Atmospheric Optics

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