Wow! Polar stratospheric clouds spotted across the UK

People spotted loads of beautiful nacreous clouds from all over the UK yesterday! These rare, very high clouds are also known as mother of pearl clouds. They’re a type of polar stratospheric cloud, known to reflect colored light after sunset and before sunrise. Earth’s stratosphere is normally cloud-free, but these clouds do sometimes appear some 9-16 miles (15-25 km) high in Earth’s atmosphere. They’re said to have more rainbow-like colors than the iridescent clouds seen around the world fairly commonly, at lower latitudes.

We've been getting some amazing pictures of these 'mother of pearl' nacreous clouds spotted across the region today. pic.twitter.com/rxEfYIYzBz

— ITV News Tyne Tees (@itvtynetees) December 21, 2023

A lone Eurasian Curlew against the 'mother of pearl' nacreous clouds this evening at Holkham, Norfolk. pic.twitter.com/oXJfyaviW5

— Wild Beijing ???? (@BirdingBeijing) December 21, 2023

Why do they occur?

Les Cowley of the website Atmospheric Optics posted a beautiful explanation for these clouds after another outbreak over the UK back in February 2016, saying:

Nacreous clouds, sometimes called mother-of-pearl clouds, are rare but once seen are never forgotten. They are mostly visible within two hours after sunset or before dawn when they blaze unbelievably bright with vivid and slowly shifting iridescent colours. They are filmy sheets slowly curling and uncurling, stretching and contracting in the semi-dark sky. Compared with dark scudding low altitude clouds that might be present, nacreous clouds stand majestically in almost the same place – an indicator of their great height.

They need the very frigid regions of the lower stratosphere some 15 – 25 km (9 -16 mile) high and well above tropospheric clouds. They are so bright after sunset and before dawn because at those heights they are still sunlit.

They are seen mostly during winter at high latitudes like Scandinavia, Iceland, Alaska and Northern Canada. Sometimes, however, they occur as far south as the UK.

We couldn’t believe our eyes ??#NacreousClouds are an extremely rare sight in Britain – they occur at about 70,000 to 100,000 feet above the earth’s surface in the stratosphere.

Tiny ice crystals act like prisms refracting & reflecting the light to produce cloud iridescence. pic.twitter.com/seZoqufhSD

— Doddington Hall (@DoddingtonHall) December 21, 2023

Are polar stratospheric clouds a cause for concern?

Spaceweather.com added that – although they once were thought to be “mere curiosities,” some polar stratospheric clouds (PSCs) are now known to be associated with the destruction of ozone:

Indeed, an ozone hole formed over the UK in February 2016 following an outbreak of ozone-destroying Type 1 PSCs.

If you spotted nacreous clouds this week, be sure to share your photos with us!

it's still going on. Ive only seen nacreous clouds once before, and that time it was pretty transient. but this has been performing all day here pic.twitter.com/bA0an4SGrg

— linden hawthorne (@Haggewoods) December 21, 2023

For winter solstice, #Nacreousclouds over Whitby this afternoon. Strange they should appear when the weather is so mild. pic.twitter.com/hwvGjIrQej

— Whitby Naturalists (@WhitbyNats) December 21, 2023

Nacreous clouds dissipating at the end of the day – they've been displaying all afternoon back in the midlands! #nacreousclouds pic.twitter.com/y6ymYBmciE

— St Martin’s Ecologist (@GranthamEcology) December 21, 2023

Bottom line: Polar stratospheric clouds – also called nacreous clouds or mother-of-pearl clouds – have been putting on a show this week.