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3 Jun 2015

Rare noctilucent clouds spotted over UK

During the summer months each year, cloud spotters eagerly stare up at the skies, hoping to catch a glimpse of rare noctilucent clouds.

They are the highest clouds in the earth’s atmosphere, found in the mesosphere – around 50 miles above the ground.

The first sightings of the year often happen in June, with a number of people tweeting pictures of them in the sky last night.

Photographs of noctilucent clouds appearing in the night sky over Britain on July, 2009.

Why are noctilucent clouds so rare?

Formed from tiny ice crystals, they are characterised by their thin, streaky cirrus-like appearance, and are usually bluish or silvery in colour.

The reason that they are so rare is because they form in a part of the atmosphere that is extremely dry and has very little moisture present.

Also, there are very few cloud condensation nuclei, such as volcanic dust or debris from meteors, for water vapour to stick to – making their presence an even greater rarity.

In addition, they are only found at latitudes of around 50 to 70 degrees north or south of the equator and require the sun to be below the horizon.

Pictures of noctilucent clouds

A number of people on Twitter have captured noctilucent clouds on camera, with a selection of the best pictures below.

If you manage to photograph any of these rare clouds, you can send pictures to me on Twitter – @liamdutton

Tweets by @liamdutton