Have you ever been on an airplane and witnessed a breathtaking spectacle in the sky? As the aircraft soars above the clouds, you may have noticed a mesmerizing display of colored rings radiating from a central point. This captivating optical phenomenon is known as a glory. While glories are often seen in close proximity to the antisolar point, they remain elusive to many. Today, we delve into the world of atmospheric optics and uncover the secrets behind the glory over Greenland.
Imagine yourself on a plane, gazing down at the billowing cloud deck beneath you. Suddenly, the sky comes alive with a kaleidoscope of colors. The rings of a glory shimmer and sparkle, marching across the clouds as if in sync with your aircraft's journey. These rings, accompanied by the ethereal tail of a contrail shadow, constantly transform in size as the cloud landscape shifts and evolves.
Glories, like many other atmospheric optical effects, occur at the antisolar point. This point lies directly opposite the sun and remains below the horizon during daylight hours. Shadows also converge at this point, creating a captivating interplay of light and darkness. If you were to observe your own shadow from a low-flying airplane, you would find it aligning perfectly with the center of the glory. However, at higher altitudes, like in the case of the photographed glory over Greenland, the shadow of the contrail takes center stage.
The intricate beauty of a glory arises from the interaction between sunlight and tiny water droplets within the clouds. These minuscule droplets scatter sunlight through a process called backscattering. As light waves pass through different paths within each droplet, they interfere with one another. This interference can either amplify or diminish the intensity of light, resulting in a circular diffraction pattern. The size of the pattern varies with the wavelength of light, giving rise to the complex hues observed in glories.
While rainbows and ice halos rely on refraction, the formation of glories follows a different path. Rainbows and ice halos are created by the refraction of light rays as they pass through raindrops or ice crystals. These phenomena occur when relatively large objects in the sky interact with light. In contrast, glories, coronae, and iridescent clouds emerge from interactions with incredibly small cloud droplets or ice crystals. Glories, in particular, owe their existence to the diffraction of light waves within these minute particles.
To truly appreciate the complexity of glories, we must consider the role of sunlight in producing their vibrant colors. Sunlight encompasses a wide range of wavelengths, each corresponding to a different color. When all the different colored glories overlap, the result is a mesmerizing display of hues. The interplay between interference and diffraction within the tiny water droplets contributes to the intricate patterns and shades that captivate our eyes.
Glories can be observed in various parts of the world, but capturing them requires a combination of favorable conditions and a keen eye. The glory over Greenland, as showcased in the photograph by Blair Brewin, exemplifies the delicate nature of this phenomenon. Its beauty lies not only in its existence but also in its fleeting nature. To witness a glory firsthand is to witness a dance between light and clouds that lasts only for a precious moment.
The glory over Greenland serves as a reminder of the wonders that await us in the realm of atmospheric optics. This captivating optical phenomenon, with its shimmering rings and ever-changing colors, continues to intrigue scientists and enthusiasts alike. By understanding the science behind glories, we gain a deeper appreciation for the interplay of light and matter within our atmosphere. So, the next time you find yourself on an airplane, keep your eyes peeled for the glory that may be hiding just beyond the clouds.
Imaged over Greenland by Blair Brewin of Calgary, Alberta. The delicacy of the glory is nicely captured. ©Blair Brewin, shown with permission.
The airplane thunders onwards and from the cloud deck far below it sparkle and shimmer the many coloured rings of a glory. The rings march across the clouds with the aircraft and accompanied by the comet-like tail of a contrail shadow. As the cloud landscape slowly shifts and changes the rings alternately shrink and swell.
A glory is one of several optical effects at the antisolar point, the point directly opposite the sun and therefore below the horizon in daylight.
Shadows also converge there and when an airplane is fairly low its shadow (or rather your shadow if you could see it) is at the glory's centre. Here the aircraft was at cruising altitude and too high for its shadow to show but you can see the long shadow of the contrail.
The tiny water drops of the clouds make the series of concentric rings by backscattering sunlight. The droplets are sufficiently small that light waves scattered via different paths - within the same droplet - interfere. The interference can be constructive (producing light) or destructive (darkness). The overall result is a circular diffraction pattern. Longer wavelengths have larger patterns and the overlap of all the different coloured glories from sunlight produce the complex hued rings that we see.
The glory colour production process is quite different from that forming rainbows or the colours of ice halos. In those refraction rather than diffraction causes light rays of different colours to take different paths through the raindrop or ice crystal. Rainbows and ice halos are made by comparatively large objects in the sky, large that is compared to the wavelength of light. Glories, coronae and iridescent clouds are made by very small cloud droplets and sometimes, excepting glories, ice crystals.
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"Glory over Greenland". Atmospheric Optics. Accessed on March 1, 2024. https://atoptics.co.uk/blog/glory-over-greenland/.
"Glory over Greenland". Atmospheric Optics, https://atoptics.co.uk/blog/glory-over-greenland/. Accessed 1 March, 2024
Glory over Greenland. Atmospheric Optics. Retrieved from https://atoptics.co.uk/blog/glory-over-greenland/.