High and low aerial glories

Last updated on September 16, 2023

High and Low Aerial Glories: A Phenomenon of Atmospheric Optics

Aerial glories, a captivating atmospheric optical phenomenon, often leave us in awe as we gaze out of airplane windows. These ethereal rings of color surround the shadow of the aircraft, creating a surreal spectacle. But did you know that there are two distinct aspects of glories that can be observed during a single flight? In this article, we will explore the fascinating world of high and low aerial glories, shedding light on their formation, appearance, and the factors that influence their size and visibility.

The Dance of Shadows and Clouds

When an aircraft is flying at a short distance above the clouds, something remarkable occurs. The shadow of the plane looms large, casting its presence upon the cloud cover. At this height, if you happen to be seated in the right spot, you may witness the glory surrounding your own shadow. The interplay between the shadow and the cloud droplets creates a mesmerizing display of colors that seem to dance around you.

However, as the aircraft ascends and the clouds recede into the distance below, a different scenario unfolds. The shadow becomes faint and barely visible, and the glory appears to dissipate into the vast expanse of the sky. This variation in visibility is intriguing, but what exactly causes it?

The Influence of Distance on Glory Size

Contrary to what one might expect, the angular size of a glory remains unaffected by the distance between the observer and the clouds. Instead, it is solely determined by the diameters of the cloud droplets. This means that regardless of whether the aircraft is close to or far from the clouds, the glory will appear to be of similar size.

The explanation lies in the intricate physics behind glory formation. Glories arise when sunlight interacts with tiny water droplets suspended in the air. These droplets act as microscopic prisms, refracting and reflecting light. The size of the droplets determines the wavelengths of light that are scattered, giving rise to the characteristic rings of color. Thus, the glory's angular size is a direct consequence of the droplet sizes, while the distance merely influences its visibility.

Exploring the Intricacies of Glory Formation

To fully comprehend the formation of glories, we must delve into the fascinating interplay of light and water droplets. When sunlight encounters a droplet, it undergoes a process known as diffraction, where the light waves bend and spread out. This diffraction causes the light to interfere constructively and destructively, resulting in a series of concentric rings.

The size of these rings depends on the droplet's diameter, with smaller droplets producing larger rings. As the droplets grow larger, the rings shrink in size until they eventually vanish. This intricate relationship between droplet size and ring size contributes to the captivating array of colors seen in glories.

The Role of Airborne Particles

While cloud droplets are the primary contributors to glory formation, they are not the only players in this atmospheric spectacle. Airborne particles, such as dust or pollution, can also influence the appearance of glories. These particles can act as nuclei for water vapor to condense around, creating larger droplets. Consequently, this can alter the size and intensity of glories, adding an additional layer of complexity to their formation.

A Kaleidoscope of Colors

Glories are renowned for their vibrant colors that span the visible spectrum. The exact hues observed depend on several factors, including the size distribution of cloud droplets and the observer's position relative to the glory. Generally, the innermost ring appears bluish, followed by a series of alternating rings that transition from green to yellow to red.

Interestingly, glories often exhibit a color reversal compared to other atmospheric optical phenomena. In many cases, the red outer ring of a glory appears closer to the observer than the inner blue ring. This peculiar reversal is a consequence of the intricate interplay between light, droplet size, and diffraction.

The Illusive Brocken Spectre

One of the most captivating manifestations of glories can be observed under specific conditions on mountain peaks or cliffs. Known as the Brocken spectre, this phenomenon occurs when the observer's shadow is cast upon a layer of clouds or fog. The glory surrounding the shadow creates a magnified and distorted silhouette, often accompanied by a radiant halo.

The Brocken spectre adds an element of mystique to the already enchanting world of glories, captivating hikers and mountaineers fortunate enough to witness this ethereal display.

Unlocking the Secrets of Aerial Glories

Despite their captivating appearance, there is still much to uncover about the intricacies of aerial glories. Researchers continue to investigate various factors that influence glory formation, including droplet size distribution, atmospheric conditions, and the role of airborne particles. By unraveling these mysteries, we gain a deeper understanding of the physics behind this awe-inspiring phenomenon.

As we peer out of airplane windows and witness the dance of shadows and clouds, let us marvel at the beauty and complexity of high and low aerial glories. These fleeting moments remind us of the vast wonders that await exploration within our own atmosphere.

Two aspects of glories seen during the same flight by Nik Szymanek (astrophotography site book). When the aircraft is a short distance above the clouds its shadow looms large and the glory can be seen to surround the point where you are seated. When the clouds are far below the aircraft the shadow is hardly visible. However, the glory's angular size depends only on the diameters of the cloud droplets, the distance of the cloud has no effect on how large it looks. Images ©Nik Szymanek, shown with permission.

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