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Widespread Noctilucent Clouds over Europe – July 2/3, 2017

Noctilucent clouds were observed across large parts of the northern half of Europe!

Noctilucent clouds are very different from the ‘ordinary’ clouds we are most used to. While most clouds form in the lowermost 10 km of our atmosphere, the troposphere, noctilucent clouds do not. These wispy apparitions form much higher, at approximately 80 km altitude in the mesosphere. They are the highest known clouds in our atmosphere, and completely detached from tropospheric clouds. Until recently, sightings of noctilucent clouds were exceedingly rare, but they have become much more common in the past several years.

Brilliant display of noctilucent clouds over Nykøbing Mors, Denmark in the early morning of June 3, 2017. Photo: Ruslan Merzlyakov / RMS Photography.

They are much too thin and too faint to be visible in the daylight, only becoming visible at dusk and dawn. At these times, the sky is still dark as the Sun is well below the horizon. However, at the altitude of noctilucent clouds, the Sun had already risen and the clouds are illuminated. This viewing geometry produces an amazing sight, with the noctilucent clouds shining bright electric white and blue against a still-dark sky. Indeed, the word ‘noctilucent’ translates into ‘night shining’ in Latin. The best time to see these clouds is when the Sun is between 16 and 6° below the horizon, which is roughly from the start of dawn to the end of nautical twilight. Look towards the north to see them.

Beautiful view of noctilucent clouds over ‘Oisterwijkse Bossen & Vennen’ nature reserve in the south of the Netherlands in the early morning of June 3, 2017. Photo: Gijs de Reijke / Dynamic Landscapes Photography – Gijs de Reijke.

Noctilucent clouds are composed of very small water droplets, up to ~100 nm across. The water droplets condense around meteoric dust – meteors, too, form at generally the same altitude as noctilucent clouds.

Look for these clouds tonight too, you may well get lucky and spot them. If not, give it another try tomorrow and keep going: NLC season will be open for at least 3 more weeks!

Brilliant display of noctilucent clouds over Almere, Netherlands on July 3, 2017. Photo. Calvin Musch.

Noctilucent clouds over Mezőkövesd, Hungary in the early morning of June 3, 2017. Photo: Lázár Endre Photography.

Over Mitterlabill, Styria, Austria on July 3, 2017. Photo: Werner Schuster.

Noctilucent cloud display over Ireland in the evening of June 2, 2017. Photo: Keith Owens.

Noctilucent clouds as seen from G.V. Schiaparelli astronomical observatory, Varese, Italy in the morning of June 2, 2017. Photo: Andrea Aletti.

Noctilucent clouds over Kloster Lehnin/Germany on the evening of July 2. Photos: Wetterbeobachtung Brandenburg.