Outbreak of noctilucent clouds over Northern Europe For the past week, areas in the northern hemisphere, particularly the northern parts of Europe, have gotten views of some fairly spectacular noctilucent or “night-shining” clouds. As illustrated here,these clouds appear on the distant horizon and have an ethereal, glowing, almost iridescent quality to them. Noctilucent clouds only form during the summer at latitudes north of 50 degrees, so this is the perfect time of year and area. These clouds are some of the highest clouds produced in the atmosphere. They can be seen just after sunset; the sun can illuminate clouds high above the surface after the surface itself moves into shadow and night. They are caused by ice crystals forming at extremely high elevations in the mesosphere, 50 to 85 kilometers above the Earth’s surface; normal clouds occur in the troposphere at elevations less than 15 kilometers. Normally this region of the atmosphere is dry, but during the peak of the summer months, rising air currents can bring enough moisture upwards to allow the nucleation of ice crystals in this far-up layer. Those ice crystals then reflect sunlight from the distant horizon, down towards viewers on Earth, making them visible. The colors could be produced by a combination of how the sunlight interacts with the light crystals and how the reflected light interacts with the different layers of Earths’ atmosphere as it travels back down. -JBB Image credits (creative commons licences): Mike O’Brien https://flickr/photos/oblique-images/14591869625/ Photos by Zoe https://flickr/photos/photosbyzoe/14591288522 Read more: https://facebook/photo.php?fbid=387230288004688 science.nasa.gov/science-news/science-at-nasa/2003/19feb_nlc/ earthsky.org/earth/july-3-4-2014-fabulous-display-of-noctilucent-clouds-over-europe nightskyhunter/Noctilucent%20Clouds.html Dear Readers, Most of our posts are not reaching you in your news feed due to fbs filtering system. If you wish to enjoy our posts more often, use the following for information on how to go about it: tinyurl/qgwac8k.
Posted on: Tue, 08 Jul 2014 15:35:02 +0000
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