Below Horizon Bow

Below Horizon Bow: An Enigmatic Atmospheric Phenomenon

The beauty and complexity of atmospheric optics never fail to astound us. Among the many fascinating optical phenomena that occur in our atmosphere, one particular phenomenon that captures the imagination is the "Below Horizon Bow." While most of us are familiar with the traditional rainbow that arcs across the sky, the below horizon bow adds a touch of mystery by appearing below the horizon line. In this article, we will delve into the intricacies of this enigmatic phenomenon and explore the science behind its occurrence.

Understanding the Below Horizon Bow

The below horizon bow is a rare and captivating optical phenomenon that occurs when sunlight interacts with water droplets in the atmosphere. Similar to its more commonly observed counterpart, the primary rainbow, the below horizon bow is created through a process known as refraction and reflection. When sunlight enters a water droplet, it bends or refracts, and then reflects off the inner surface of the droplet before exiting. This bending and reflection cause the light to disperse into its constituent colors, forming a circular arc of colors in the sky.

The Role of Sun Angle

What sets the below horizon bow apart from the primary rainbow is the position of the sun in relation to the observer. The sun must be at an angle higher than 42° above the horizon for a below horizon bow to occur. When the sun is at this specific angle, light rays refract and reflect within water droplets at such an angle that the resulting arc appears below the horizon line. It is important to note that this phenomenon is typically seen in mountainous regions or from elevated viewpoints where the observer's line of sight extends below the horizon.

A Delicate Balance of Geometry

The geometry of light rays and water droplets plays a crucial role in the formation of the below horizon bow. As sunlight enters a droplet, it undergoes multiple internal reflections before exiting. These internal reflections cause the light to deviate from its original path, resulting in the formation of the below horizon bow. The angles at which the light rays enter and exit the droplets determine the size and position of the bow.

Additional Factors Influencing the Below Horizon Bow

While the sun's angle and geometric considerations are primary factors in the formation of the below horizon bow, other atmospheric conditions can also influence its appearance. Here are a few additional factors that can enhance or alter the below horizon bow:

  • Atmospheric Moisture: The amount of moisture in the air affects the size and intensity of the bow. Higher moisture levels increase the likelihood of seeing a vivid below horizon bow.

  • Particle Size: The size of water droplets in the atmosphere can impact the visibility of the below horizon bow. Smaller droplets tend to create more defined and vibrant bows.

  • Air Pollution and Aerosols: Pollution and aerosol particles in the atmosphere can scatter and absorb light, potentially diminishing the visibility of the below horizon bow.

Capturing the Below Horizon Bow

Due to its unique positioning below the horizon, capturing a below horizon bow on camera can be challenging but immensely rewarding. To photograph this ethereal phenomenon, one must find an elevated vantage point that allows a clear view of the sky below the horizon line. Patience and careful observation are key, as below horizon bows are rare occurrences. When conditions align, a below horizon bow can create a mesmerizing image that leaves viewers in awe of nature's wonders.

Exploring the Magic of Atmospheric Optics

The below horizon bow is just one example of the captivating optical phenomena that occur in our atmosphere. From halos and sundogs to iridescent clouds and crepuscular rays, our sky is a canvas for nature's light show. Each of these phenomena provides an opportunity to marvel at the interplay between sunlight, atmospheric particles, and our perception of light. By delving into the science behind these phenomena, we gain a deeper appreciation for the wonders that surround us.

As we continue to explore and understand atmospheric optics, we unlock the secrets behind these captivating displays of light. The below horizon bow serves as a reminder that even in the realm of optics, nature has a way of surprising us with its intricate and beguiling creations. So, the next time you find yourself gazing at the sky, keep an eye out for the below horizon bow and let its ethereal beauty transport you to the realm of atmospheric wonders.

Rainbow from Mount Wendelstein, Germany imaged by Claudia Hinz (Atmospheric Optics Site). The bow is below the horizon because the sun is more than 42° (the radius of the primary) high. ©Claudia Hinz, shown with permission.

Note: this article has been automatically converted from the old site and may not appear as intended. You can find the original article here.

Reference Atmospheric Optics

If you use any of the definitions, information, or data presented on Atmospheric Optics, please copy the link or reference below to properly credit us as the reference source. Thank you!

  • "Below Horizon Bow". Atmospheric Optics. Accessed on March 29, 2024. https://atoptics.co.uk/blog/below-horizon-bow/.

  • "Below Horizon Bow". Atmospheric Optics, https://atoptics.co.uk/blog/below-horizon-bow/. Accessed 29 March, 2024

  • Below Horizon Bow. Atmospheric Optics. Retrieved from https://atoptics.co.uk/blog/below-horizon-bow/.