Sunrise Green Flash, Taiwan - OPOD

Sunrise Green Flash: A Spectacular Phenomenon in Taiwan

Have you ever witnessed a sunrise green flash? This mesmerizing optical phenomenon occurs when the sun appears to briefly flash green just as it rises above the horizon. While green flashes are commonly associated with sunsets, capturing a sunrise green flash is much more challenging. However, Chih Hsiung Chen, a talented photographer from Taiwan, managed to capture a stunning sequence of a sunrise green flash over the ocean. In this article, we will delve deeper into the science behind this phenomenon and explore why it is so elusive.

The Challenge of Capturing a Sunrise Green Flash

Living in eastern Taiwan, Chih Hsiung Chen discovered that the only way to observe a green flash is at sunrise. However, capturing this fleeting moment presents its own set of challenges. Unlike sunsets, where the position of the sun is known, the precise timing and location of the sunrise green flash remain uncertain. Nevertheless, Chen devised a clever strategy to increase his chances of capturing this elusive phenomenon.

By observing solar (crepuscular) rays converging towards the hidden sun several minutes before sunrise, Chen was able to predict where a green flash might appear. He also relied on local sunrise and sunset predictions to determine the exact minute of sunrise. Armed with this knowledge, he utilized continuous shooting techniques to increase his chances of capturing the elusive green flash.

Understanding the Science Behind Green Flashes

Green flashes are a type of mirage that occurs when vertical magnification separates otherwise slightly dispersed colors. In a normal atmosphere, refraction merely produces a green rim on the horizon sun that is invisible to the naked eye. However, under certain atmospheric conditions, such as warm air beneath cooler air, a green flash can occur.

When rays pass through the boundary between cool and warm air, they are refracted back upwards. This results in an inverted solar image appearing beneath the "true" one. The "true" image is produced by rays passing only through cooler air. When these two images overlap just above the horizon, they are vertically magnified, creating the illusion of a green flash.

The Inferior Mirage Variety

The sunrise green flash captured by Chih Hsiung Chen belongs to the classical "inferior mirage" variety. This particular type of mirage is produced by warm air beneath cooler air. As the rays of the sun pass through the cool/warm air boundary, they are refracted, creating the inverted image phenomenon described earlier. The slivers of sun appearing above the horizon would actually show a bright blue color if not for the strong scattering of blue light by the atmosphere. Instead, we perceive the color as green.

Appreciating the Beauty of Sunrise Green Flashes

Chen's photographs beautifully capture the enchanting nature of sunrise green flashes. As the sun rises over the ocean, its light interacts with the atmosphere, creating a spectacle that is both awe-inspiring and ephemeral. The vivid green hue against the backdrop of the deep blue sky and shimmering water evokes a sense of tranquility and wonder.

Witnessing a sunrise green flash is a rare and remarkable experience. It serves as a reminder of the natural wonders that surround us and the intricate workings of our atmosphere. While challenging to capture, photographers like Chih Hsiung Chen continue to push the boundaries of their craft, enabling us to appreciate these fleeting moments of atmospheric beauty.

In conclusion, sunrise green flashes are a captivating atmospheric phenomenon that occurs as the sun rises above the horizon. While typically associated with sunsets, capturing a sunrise green flash is a unique challenge due to the unknown position and timing of the phenomenon. Through careful observation and strategic photography techniques, photographers like Chih Hsiung Chen have managed to document these mesmerizing moments. Understanding the science behind green flashes, particularly the inferior mirage variety, enhances our appreciation of their beauty. These fleeting bursts of green light serve as a reminder of the remarkable wonders that can be found in our natural world.

Sunrise Green Flash ~ Chih Hsiung Chen captured this dramatic green flash sequence looking eastwards over the ocean from Taiwan.

Sunrise flashes are hard to capture. This one also gives the lie to beliefs that a clear sky is needed.

All images ©Chih Hsiung Chen, shown with permission

“Almost all green flash photos are taken in sunset.

I live in eastern Taiwan in the western Pacific Ocean. The only way to observe a green flash is at sunrise. A sunrise green flash is more difficult due to the unknown position where the sun will first appear and its precise timing.

I used solar (crepuscular) rays converging towards the hidden sun several minutes before sunrise to predict where a flash might appear. Local sun rise/set predictions offered the sunrise time to minute level. I finally took the sunrise green flashes by continuous shooting.”

Green flashes are mirages where vertical magnification separates otherwise only slightly dispersed colours. The refraction by a normal atmosphere merely produces a green rim on the horizon sun that is invisible to the unaided eye.

This green flash is of the classical 'inferior mirage' variety and is produced by warm air beneath cooler air.

Rays passing through the cool/warm air boundary are refracted back upwards. The eye sees an inverted solar image beneath the 'true' one. The latter is produced by rays passing only through cooler air.

Each image is vertically magnified when they overlap just above the horizon. The two slivers of sun would show bright blue but for strong scattering of blue light by the air. We usually see green instead.

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  • "Sunrise Green Flash, Taiwan - OPOD". Atmospheric Optics. Accessed on March 1, 2024. https://atoptics.co.uk/blog/sunrise-green-flash-taiwan-opod/.

  • "Sunrise Green Flash, Taiwan - OPOD". Atmospheric Optics, https://atoptics.co.uk/blog/sunrise-green-flash-taiwan-opod/. Accessed 1 March, 2024

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