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Jul 22, 2014 11:17 AM by Stephen Bowers

Rare Noctilucent Clouds Spotted In Europe

We can only rarely see Noctilucent clouds in Colorado. We are simply not at a latitude high enough to make for favorable viewing of these rarely seen clouds that exist more than 50 miles above the ground.

Clouds typically form within 10 miles above the ground within the Earth's troposphere. Noctilucent clouds do not bring sensible weather and form where the Earth's atmosphere is fading to outer space, near the levels where colorful auroras occur.

What is strange about these clouds is necessary water vapor is not common so high in the atmosphere. That's where the season becomes important. During the summer, the ground is warm enough to loft small amounts of water vapor extremely high. The water vapor also needs something onto which it can condense water droplets or deposit ice crystals. As it turns out, the outer reaches of our atmosphere can brush by the trails of comets and asteroids. The dust left behind can act as those important cloud condensation nuclei, as meteorologists call the objects onto which water vapor can condense or deposit.

These Noctilucent clouds form in the high altitudes over high latitudes and are only visible at the perfect angle. The website Spaceweather.com says the rare clouds can best be viewed 30 to 60 minutes after sunset when the sun has dipped 6 degrees to 16 degrees below the horizon. Noctilucent clouds are high enough that the sun below the horizon can still reflect light off of the clouds, making them glow an electric blue.

Spaceweather.com says Noctilucent clouds can be seen (rarely) as far south as Utah and Colorado, though they are most common within the Arctic Circle. 

This picture from Spaceweather.com was taken in the country Estonia by Alex Lebedev, who said about the Noctilucent clouds, "they were stunning."

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