Fog Bows, Glories, and Brocken Spectres: Beauty in the Fog

The Scottish Highlands are renowned for their dramatic landscapes and unique atmospheric conditions, which create the perfect environment for observing rare optical phenomena. Among the most intriguing are fog bows, glories, and Brocken spectres—natural displays that combine light, mist, and perspective to produce striking visual effects.

Fog Bows: Like Rainbows But Different

Fog bows are a less vivid counterpart to rainbows, forming in mist or fog rather than rain. They appear as pale arcs, typically white with faint hints of red and blue at their edges. This subdued coloration occurs because the water droplets in fog are much smaller than raindrops, measuring only a few micrometers in diameter. These smaller droplets cause light to scatter through a process known as diffraction, where the bending of light around the droplets results in the soft and pale appearance of the fog bow.

Glories: Rings of Light

Glories manifest as concentric, multicolored rings surrounding the shadow of an observer cast onto a cloud or mist below. They result from the diffraction of sunlight by tiny water droplets. Interestingly, glories can also appear at the center of fog bows (you can just make one out in the picture above).

In the Scottish Highlands, glories are often seen during temperature inversions, where clouds or mist settle below the summits. Observing one requires specific conditions, including clear skies above and mist below, making them a rare but rewarding experience for those exploring elevated terrains.

Brocken Spectres: Shadows in the Mist

Brocken spectres occur when an observer’s shadow is cast onto a cloud or mist, creating an elongated and magnified silhouette. This phenomenon is often accompanied by a glory, adding colorful rings around the shadow. The name originates from the Brocken, a mountain in Germany, but these striking optical effects are also common in the Scottish Highlands.

Brocken spectres can feel uniquely personal, as they are centered on the observer’s own shadow. Ideal conditions for spotting them include misty weather, a low sun, and a vantage point above the mist layer, making them a frequent reward for early-morning hillwalkers.

Maximizing Your Chances

Although these phenomena are rare, specific strategies can increase your likelihood of encountering them. Timing is crucial; aim for early morning or late afternoon when the sun’s angle is low. High-altitude locations are ideal (fortunately we have many of these locations in Scotland!).

We’ve become a big fan of using sounding charts to predict optimal conditions for these phenomenon (get custom soundings charts for various areas of the UK at rasp.stratus.org.uk). Much like inversions, you can use sounding charts to identify atmospheric conditions such as temperature, humidity, and dew point that favour the formation of mist or cloud layers where these optical phenomena are most likely to occur. Learn more in this post.