Brume, Roke, and Other Vapourous Delights

There is something magical about mist creeping up the dales of the North York Moors, at least if you’re being sentimental. Behind me, the mist—sorry, ‘brume’—was crawling up the Vale of Mowbray, but that was less of a spectacle than this show over Raisdale and Bilsdale.

Speaking of brume, it is the ideal word for this frosty vapour, with roots in the Roman word brumalis, meaning ‘belonging to winter.’ If you find that too pretentious, there is always the local term ‘roke.’

For the pedantic among us, and I may be sticking my neck out here, the technical term is “advection fog.” This happens when warm, moist air passes over a colder surface and cools, typically when a warm front moves over frost or snow. This is, naturally, different from “valley fog,” which forms when cold air sulks at the bottom of a valley, leading to condensation and fog. Valley fog, it seems, is typically the product of temperature inversions. Thrilling stuff.

As for the atmospheric folklore, it is said that under certain conditions, these mists can glow at dusk, terrifying Roman soldiers during their escapades in Scotland. This so-called “foolish fire” supposedly put the fear of the gods into Caesar’s legions¹An Eerie Encounter In The Gloamin! Sunday Post – 08 August 1971. Not that Caesar himself would have seen it, as his British sightseeing stopped just north of the Thames. Agricola might have been more geographically adventurous, but the whole story seems a bit foggy—pun absolutely intended.

Back to Bilsdale, whose south-facing aspect apparently makes it a hotspot for such misty theatrics. The fog often spills dramatically over the Cleveland Hills into the Vale of Cleveland. I would show you a photograph of this phenomenon, but my hard drive has swallowed it whole, as hard drives tend to do. Alas.

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  An Eerie Encounter In The Gloamin! Sunday Post – 08 August 1971