Green Flashes & Tilted Air

Last updated on September 16, 2023

Green Flashes & Tilted Air: A Phenomenon of Atmospheric Optics

Atmospheric optics never fails to amaze with its captivating displays of natural phenomena. One such phenomenon is the occurrence of green flashes during sunset or sunrise. While green flashes may seem like a mythical occurrence, they can be explained through the interaction of light with the atmosphere. In this article, we will delve deeper into the science behind green flashes and explore the role of tilted air in their formation.

Understanding the Basics of Green Flashes

As the sun nears the horizon, its rays travel through a greater portion of the Earth's atmosphere. This causes the sunlight to undergo various interactions, including scattering and refraction. Refraction refers to the bending of light as it passes from one medium to another. The Earth's atmosphere is composed of layers of air with varying densities, which affects the way light bends.

When the sun is low on the horizon, its rays slant almost horizontally across the atmosphere. The denser air near the surface gradually transitions to less dense air at higher altitudes. This change in density causes the sun's rays to refract, making it appear higher than its actual position. Blue and green rays are deflected the most, resulting in an upper green rim and a lower blue rim. However, the green rim is usually too narrow to be seen by the naked eye or produce a distinct flash.

Mirages: The Key to Green Flashes

To witness a green flash, some form of vertical magnification is required to stretch the narrow green rim and create a visible separation of colors. Mirages, which occur when light rays are bent due to temperature variations in different layers of air, provide this magnification. Green flashes are closely associated with mirages, as they require the same conditions for their occurrence.

In the case of a green flash caused by a temperature inversion, where warmer air lies above cooler air, the necessary strong refraction occurs as the sun's rays pass between these layers. This temperature inversion creates an environment conducive to mirages, enabling the vertical magnification needed for a green flash to occur. The presence of multiple stacked inversions can be observed through the ripples and bumps along the sun's rim.

Tilted Air: Unveiling the Extraordinary

While a pure mock-mirage flash typically occurs near the horizon, where the observer must be positioned above the inversion layer, there are instances where the inversion layer is tilted or has a vertically wavy structure. This unique configuration allows for sections of the inversion to be visible when looking downwards. It is through this tilted or wavy structure of the inversion that Pete Lawrence captured his remarkable green flash.

By looking upwards to an inversion, even more extraordinary phenomena can unfold. The interplay between light and the tilted air can give rise to additional optical effects, further enhancing the visual spectacle. These captivating displays serve as a testament to the intricate nature of atmospheric optics and the wonders it can unveil.

Exploring Further Mysteries of Atmospheric Optics

The study of atmospheric optics continues to unravel the mysteries behind mesmerizing natural phenomena such as green flashes. Researchers and enthusiasts alike are driven by a sense of wonder and curiosity to comprehend the intricate workings of our atmosphere. By exploring further into atmospheric optics, we gain a deeper appreciation for the captivating displays that nature has to offer.

From iridescent clouds to halos, rainbows to sundogs, each phenomenon presents its own unique set of conditions and interactions. By understanding the science behind these optical marvels, we can better appreciate their beauty and unravel the secrets hidden within our atmosphere.

As technology advances and scientific knowledge expands, we continue to delve deeper into the realm of atmospheric optics. Sophisticated instruments and observation techniques enable us to capture and analyze these fleeting moments of natural beauty. Through our collective efforts, we gain a better understanding of the processes at play and the factors that contribute to the formation of green flashes and other atmospheric wonders.

In conclusion, green flashes and tilted air offer a captivating glimpse into the realm of atmospheric optics. These phenomena, driven by the interaction of light with the Earth's atmosphere, provide a visual spectacle that never fails to inspire awe. By delving deeper into the science behind green flashes and exploring the role of tilted air, we gain a greater appreciation for the intricacies of our natural world and the wonders it has to offer. So, the next time you find yourself witnessing a sunset or sunrise, keep an eye out for the elusive green flash and let yourself be enchanted by the magic of atmospheric optics.

Green Flashes and Tilted Air

The sun sits on the horizon like a huge Christmas pudding topped with a sprig of green

holly. Pictured in wintry central England by Peter Lawrence.

There are many types of green flash. This one of different temperature that in turn give strong

is a variant of a mock-mirage flash.

As the sun gets low, its rays slant almost horizontally across the atmosphere. The air is

denser near the surface and becomes increasing rarified with height. The different density layers refract the sun's rays making it set late and appear up to half a degree higher than its true position. Blue and green rays deflect the most, pushing up the 'green' and 'blue' suns to produce an upper green rim. A green rim because the blues scatter away.

This is the usual - and false - explanation of green flashes. The green rim is much too narrow to see by eye or make a flash. A flash needs some kind of vertical magnification to stretch the rim's colour separation. Mirages do it. Green flashes need mirages. Mirages need air layers light ray refraction.

Pete Lawrence's flash came from a temperature inversion, warmer air above cooler. The necessary strong refraction occurred as sun rays crossed between the layers. There were in fact several stacked inversions revealed by the ripples and bumps along the sun's rim.

There is a further twist - or rather wave - in the story. The pure mock-mirage flash occurs close to the horizon as the observer must be above the inversion layer. Not possible here. Pete's inversion(s) were tilted or, more likely, had a vertically wavy structure. That made it possible to look downwards on sections of the inversion.

Even stranger things can happen when looking upwards to an inversion.

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