Stories tagged noctilucent clouds

Sep
22
2007

Blue cloud skies: This noctilucent cloud was photographed last summer over the United Kingdom. The bluish-glowing clouds are showing up the sky much more often, possibly due to global warming. (Photo by Alex Lloyd-Ribeiro)
Blue cloud skies: This noctilucent cloud was photographed last summer over the United Kingdom. The bluish-glowing clouds are showing up the sky much more often, possibly due to global warming. (Photo by Alex Lloyd-Ribeiro)
The reports are coming in more frequently of weird sights in the evening sky. And we’re not talking about people seeing UFOs.

What they’re seeing are noctilucent clouds. The clouds look like your regular cirrus cloud but as the sun has set, they shimmer with a blue, electric glow that can be seen from people on the ground. According to researchers, they form in the summer about 50 miles high in the sky. They’ve been seen as far back in time as the 1800s, but their reports are becoming more frequent, possibly because of global climate change thanks to increasing amounts of greenhouse gases in the atmosphere.

Want to see a variety of photos of noctilucent clouds? Check out this website of such clouds seen in Europe.

In fact, you can’t see the clouds during the daytime. They only begin to appear at dusk when most sunlight is gone, but some sun rays can still illuminate that high clouds that are floating along the edge of space.

A theory for why noctilucent clouds are more regularly appearing is that greenhouse gases are deflecting heat from the highest levels of the atmosphere. That allows more ice crystals to thrive at that level and form into these special clouds. That same principle also may be deflecting more moisture into the upper atmosphere, providing more material for the clouds to form with.

This past spring NASA launched a special satellite to watch and gather data about these growing cloud formations. The project is called AIM – Aeronomy of Ice in the Mesosphere.