Noctilucent clouds

If you're a skywatcher in the U.S., you have something new to look for in this new century. A rare and mysterious cloud type has been sighted for the first time in the heart of the nation. It's called a noctilucent cloud . . .

Nearly all clouds form in the troposphere, the lowest 10 miles of our atmosphere. But noctilucent clouds develop in the mesosphere, about 50 miles up. Noctilucent means "glowing at night", and these clouds DO glow with a distinctive white or pearly-blue cast. They look a bit like streaks of cirrostratus or "mare's tails."

Read more here and here. There are also numerous links (including pictures and video) at Wikipedia.

Posted by David on September 12, 2008 8:10 AM