The White Rainbows or Fogbows

Understanding Their Formation and Rarity

White rainbows, also known as fogbows, are rare atmospheric phenomena that appear as pale, ghostly arcs in the sky when sunlight interacts with tiny water droplets in fog rather than raindrops. Unlike the vivid colors of traditional rainbows, fogbows are mostly white or faintly colored due to the much smaller droplet size scattering the light differently.

These striking arcs can be seen in areas where sunlight meets thin fog, such as coastlines, mountain valleys, or fields in the early morning. The subtle beauty and rarity of fogbows have fascinated both scientists and casual observers, making their appearances a memorable event for those lucky enough to witness them.

What Are White Rainbows or Fogbows?

White rainbows, also known as fogbows, are optical phenomena that look like rainbows but display little or no color. These arcs can appear large, pale, and almost ghost-like, often forming under specific atmospheric conditions involving fog or very fine water droplets.

Definition and Distinctive Characteristics

A fogbow is a type of rainbow that forms when sunlight interacts with tiny water droplets in fog, rather than larger raindrops. Unlike typical rainbows, the droplets in fog are much smaller—often less than 0.05 millimeters in diameter.

This difference in droplet size affects the way light is diffracted, resulting in an arc that is almost entirely white, with just the faintest hints of red or blue at the edges. Most observers see it as a white or pale bow, leading to names like “white rainbow” or “ghost rainbow.”

Key features:

• Appears primarily white due to the small droplets.

• Often visible when the sun is low and fog is present.

• Can arch across a wide portion of the sky, sometimes as large as a regular rainbow.

Key Differences Between Fogbows and Rainbows

The most noticeable difference between a fogbow and a traditional rainbow is its lack of vibrant color. A rainbow occurs when sunlight refracts, reflects, and disperses through larger raindrops, producing a spectrum of colors in the familiar order.

In contrast, a fogbow’s much smaller droplet size causes extensive diffraction of light, which blurs and blends the colors together. This process results in a predominantly white appearance, with only a suggestion of muted colors at the outer margins.

Feature Rainbow Fogbow (White Rainbow) Droplet Source Rain (larger droplets) Fog/mist (tiny droplets) Appearance Bright, colored arc Pale, mostly white arc Color Visibility Distinct spectrum Faint or absent Light Interaction Refraction & reflection Diffraction dominates

Common Names and Terminology

The terms used to describe this phenomenon highlight its unusual appearance and origin. Fogbow is the most technical term, directly referencing its formation in fog.

Other common names include white rainbow and ghost rainbow, both pointing to its pale, translucent look compared to regular rainbows. In scientific contexts, “fog bow” may also appear, emphasizing the optical nature of the feature.

Regardless of the name, all refer to the same optical effect created by the interaction of sunlight and tiny fog droplets. The use of different terms often depends on local tradition, cultural references, or the specific atmospheric scenario in which the arc is observed.

The Science Behind Fogbows

Fogbows form under specific conditions involving sunlight and tiny water droplets. Their physical process, the interaction of sunlight with the droplets, and the resulting faint or white appearance set fogbows apart from brighter, colorful rainbows.

Physical Formation Process

Fogbows develop when sunlight encounters a cloud or bank of fog made up of minute water droplets. Unlike standard rainbows, which form with raindrops roughly 0.5 mm in diameter, fogbows use droplets typically less than 0.05 mm in size.

The small size of these droplets is key. Instead of bright refracted colors, the sunlight is primarily scattered through diffraction and a weaker version of reflection. This scattering blurs and spreads out any potential color, creating a broad and pale bow. The process can occur in any location with the right fog and sun conditions, including over land, water, or even from aircraft above cloud banks.

Role of Sunlight and Water Droplets

Sunlight must strike the fog at a low angle, typically when the sun is behind the observer. Without direct sunlight, a fogbow will not form. The sunlight passes through the mass of suspended water droplets in the fog.

Water droplets in fog are much smaller than those in rain, usually around 10–15 micrometers. Because of their size, these droplets bend the light in a way that intensifies diffraction while reducing the effects of regular refraction and reflection. The uniformity of droplet size in fog enhances the phenomenon, increasing the chances for a fogbow to develop over a wide area.

Color Appearance and Weak Colors

A fogbow usually looks white or very pale. This whiteness is the direct result of the weak colors produced by tiny water droplets. In larger raindrops, light separates into visible bands, but small droplets spread colors through diffraction until they overlap and nearly cancel out.

Some observers may note faint hints of color—most often a subtle red outer edge and a bluish or grayish inner edge—but these are hard to spot. The lack of strong colors is a defining feature. The table below summarizes the main differences in appearance:

Feature Rainbows Fogbows Droplet size Large Tiny Colors Vivid, distinct Weak, nearly white Outer edge Red Often faint red Visibility High Low, ghostly

This ghostly appearance gives fogbows their common names of "white rainbows" or "ghost rainbows."

Environmental Conditions for Fogbow Formation

Fogbows depend on very specific environmental conditions involving the presence of fog or mist composed of tiny water droplets. These requirements set fogbows apart from typical rainbows and make them relatively uncommon compared to their colorful counterparts.

Fog and Mist Requirements

Fogbows form when sunlight interacts with fog or mist consisting of extremely small water droplets, usually less than 0.05 mm in diameter. This tiny droplet size is essential, as it scatters light differently than the larger droplets found in rain. The small droplets cause the colors in the bow to overlap, producing the characteristic white or faintly colored appearance.

The presence of dense fog or mist increases the chances of a visible fogbow because more light can scatter from multiple tiny droplets. Both early morning fog and marine mist are effective at creating the right conditions. Direct sunlight is necessary; the Sun should be low in the sky, behind the observer, so its rays pass through the fog at the correct angle. Without these elements, a fogbow will not appear.

Ideal Locations and Timing

Fogbows most commonly appear in areas with frequent and dense fog, such as coastal regions, open fields, and mountainous landscapes. The UK is one notable place where fogbows are regularly observed due to its frequent foggy weather. Other reliable spots include riverbanks, marshes, and sea cliffs.

Optimal times to see fogbows are in the early morning or just before sunset, when fog or mist is more likely, and the Sun is low. They can also appear after rain showers when lingering fog remains. Patience and the right weather conditions are crucial, as even a small change in sunlight or fog density can cause the phenomenon to vanish. For the best view, observers should stand with the Sun directly behind them and look toward the fog.

Notable Sightings and Locations

Fogbows, sometimes called “white rainbows,” have made appearances in various parts of the world and often attract attention from both photographers and atmospheric scientists. Documented sightings in regions with moist, foggy conditions highlight their rarity and the specific weather settings that make them possible.

Famous Observations: Melvin Nicholson in Scotland

One of the most widely recognized fogbow photographs was captured by Melvin Nicholson, a landscape photographer, in November 2016. He observed and documented the phenomenon while in Rannoch Moor, a remote area in the Scottish Highlands.

Nicholson described the sight as a complete arc of white stretching above the misty landscape. His image gained significant media coverage, bringing public awareness to fogbows. The conditions that day included thick fog with sunlight breaking through, which are ideal for fogbow formation.

His photograph stands out due to the clarity and full arc of the fogbow, making it an exemplary instance of this atmospheric phenomenon. Nicholson’s sighting is frequently cited in discussions about fogbows due to its visual impact and detailed documentation. Rannoch Moor's typical weather—frequent fog and open spaces—makes it a notable site for such occurrences.

Other Documented Locations

Fogbows have been reported in scattered locations from Australia to Canada and the United Kingdom. For example, one notable sighting took place in Maralinga, South Australia, where the phenomenon was observed in early morning fog.

In Canada, fogbows have been recorded near Thompson, Manitoba, where cold weather and fog are common. The United Kingdom has also seen confirmed sightings, with several reported across Kent. The Met Office has verified these events, noting fogbows appear most often when sunlight interacts with tiny water droplets in fog.

In folklore, these events are sometimes called “ghost rainbows” or “white rainbows,” and often evoke curiosity due to their unusual appearance. Scientists monitor such locations to study how local weather patterns contribute to fogbow formation, maintaining records that help inform both research and public interests.

Visual Appearance and Variations

Fogbows, also known as white rainbows, display distinct visual traits compared to typical rainbows. Their muted colors or even colorless arcs can surprise observers expecting vivid bands of light.

Shape and Size Differences

Fogbows share the same arc shape as traditional rainbows. Both display a circular or semicircular arc opposite the sun when viewed at the right angle.

Fogbows are usually broader and fainter than rainbows. Their width can exceed that of a typical rainbow, and the bow’s colorless appearance makes it harder to spot at first glance.

Colors in fogbows are minimal or absent. Sometimes a pale red or blue edge can be seen, but most of the bow appears white due to the small size of fog droplets, which scatter all wavelengths evenly. Because of this, color separation is much less pronounced than in rainbows formed from larger raindrops.

Cloud Bows and Related Phenomena

Cloud bows, also called cloudbows or mistbows, are related phenomena formed in clouds, mist, or even spray. They occur under similar optical conditions as fogbows.

Just like fogbows, cloud bows have a white or pale appearance. The difference is the medium—cloud bows form in clouds or fog at elevation, while fogbows are seen near the ground.

Other related phenomena include Bouguer’s halo and Ulloa’s ring. These optical arches are variations produced by tiny water droplets in haze or cloud, creating white or faintly colored arcs similar to fogbows. They are all categorized by their broad, whitish arcs and lack of strong color, distinguishing them from classic rainbows.

Photographing White Rainbows

Photographing a fogbow, or white rainbow, requires careful planning and the right techniques due to its faint appearance. The low contrast and subtle color make capturing these phenomena more challenging than photographing standard rainbows.

Techniques for Capturing Fogbows

The best chance to see and photograph a fogbow is in the early morning, when sunlight intersects with lingering fog or mist. Positioning is crucial—stand with the sun directly behind, facing toward the fog. Strong backlighting helps illuminate the delicate arc of the fogbow.

Using manual focus is recommended. Autofocus can struggle with the low contrast of a white rainbow. To help define the fogbow, adjusting the angle and slightly moving up or down may make the arch more visible.

A polarizing filter can sometimes enhance contrast, but results may vary due to the diffuse nature of light in fog. Extending the exposure time can help reveal detail in the faint rainbow but avoid overexposing the surrounding fog and sky.

Best Equipment and Settings

A DSLR or mirrorless camera with a wide-angle lens (preferably 16–35mm) works well for capturing the entire fogbow. Tripods are recommended for stability during longer exposures.

Suggested camera settings include a low ISO (100–400) to minimize noise, an aperture around f/8–f/11 for good depth of field, and a slow shutter speed to allow more light for faint arcs. Bracket exposures if possible, as fogbows can vary widely in brightness.

Shoot in RAW format to allow maximum post-processing flexibility. Adjust contrast, clarity, and whites during editing to help bring out the subtle features of the fogbow without making the image look unnatural.

Privacy and Cookie Use for Fogbow Imagery

When sharing or viewing fogbow photos online, users often encounter issues about personal information and website tracking. Both how personal data is handled in image galleries and the details of website privacy policies influence user experience and data security.

Handling Personal Data in Online Galleries

Online galleries that showcase fogbow imagery sometimes collect personal data when users upload or comment on photos. This can include names, email addresses, location data, and even metadata attached to uploaded images.

Photographers sharing fogbow images should be aware that photo metadata (like GPS coordinates and camera details) may be accessible to others if not removed before uploading. Viewers who comment or interact may also be required to submit contact details, which should be handled securely by the gallery.

Many reputable galleries use measures such as user consent forms and data anonymization to reduce risks. Users should look for clear options to adjust or delete their own data. A table summarizing common data collected by galleries:

Data Type Example Purpose Personal info Email address Account management Image metadata GPS location Display, sorting images Usage data Viewing history User experience improvement

Understanding Website Privacy Policies

Most fogbow imaging galleries and related sites use cookies. Cookies help retain user preferences, analyze traffic, or enable features like favorites and image uploads. Some cookies are strictly necessary for the website to function, while others track browsing for analytics or advertising.

A privacy policy explains how a site collects, uses, and stores personal data—including data collected through cookies. Users should review privacy policies to understand the types of cookies used and the reasons for data collection. Key privacy policy points often include:

• The kinds of cookies set and their use.

• How personal data from profiles or uploads is processed.

• Rights users have to access, correct, or delete their information.

• Contact information for data inquiries.

Knowing these policy details allows users to make informed choices about sharing and viewing fogbow imagery online.