Rare iridescent clouds have been captured over Scotland, northern England and the West Midlands. These are polar stratospheric clouds or Nacreous clouds.
Key points
- They’re sometimes called “mother of pearl” clouds due to their striking pearlescent appearance.
- They form only below -78C. Nacreous clouds form over polar regions in our lower stratosphere between 68,500 and 100,000 feet.
- Because of their high latitude and the curvature of Earth’s surface, nacreous clouds are illuminated by sunlight from below the horizon and reflect it toward the ground.
- Ice particles that form nacreous clouds are far smaller than those that form more common clouds.
- As sunlight passes through these tiny particles it diffracts and the colors are separated into different wavelengths creating the stunning ‘rainbow’ effect in the sky.
- Nacreous clouds are in indicator of especially cold air high in the atmosphere.
- Because of the very low temperatures required for their formation, the clouds are usually seen over Scandinavia, northern Canada and northern Russia.
