Andrew Chick Ecology

A Brocken spectre is a striking optical phenomenon sometimes seen from mountains, ridges or aircraft when your enlarged shadow is projected onto cloud or mist below you.

It occurs when the Sun is behind you and you are looking towards a bank of cloud or mist. Your shadow is cast onto the tiny water droplets in the cloud. Because the cloud may be some distance away and there are few visual clues to scale, the shadow can appear enormous, giving the impression of a huge human figure standing within the mist.

Often the shadow’s head is surrounded by one or more coloured rings of light, known as a glory. These rainbow-like rings are produced by sunlight interacting with the tiny droplets of water in the cloud.

The name comes from the Brocken, the highest peak in Germany’s Harz Mountains, where the phenomenon was famously observed and described. It has acquired a rather supernatural reputation because, before the science was understood, suddenly seeing a gigantic human-shaped figure apparently moving within the clouds could understandably be rather alarming!

In the Lake District, conditions associated with cloud inversions can provide excellent opportunities to see one. If you were standing high on Skiddaw, for example, with the summit above an inversion, the Sun behind you and cloud immediately below, your shadow could be projected onto the cloud.

One particularly fascinating feature is that each observer sees their own Brocken spectre centred on themselves. The glory is produced by light travelling along the particular line between the Sun, observer and cloud droplets, so the person standing beside you sees their own version rather than exactly the same one.

Coming across a Brocken spectre while standing above a Lake District cloud inversion is therefore rather special: a sea of cloud beneath you, blue sky overhead, distant summits emerging like islands – and your own shadow surrounded by a rainbow halo on the clouds below.