NASA spaceweather Update SERPENTINE NOCTILUCENT CLOUDS: After weeks of sightings over Europe, noctilucent clouds (NLCs) are spreading to North America. A spectacular display emerged over the Edmonton area on July 8/9, reports Canadian photographer Mark Zalcik. For awhile there were multiple zones of billow-type NLC, including the snake-like one in this photo. NLCs are Earths highest clouds. Seeded by meteor smoke, they form at the edge of space 83 km above Earths surface. When sunlight hits the tiny ice crystals that make up these clouds, they glow electric blue. In the northern hemisphere, July is the best month to see them. NLCs appear during summer because that is when water molecules are wafted up from the lower atmosphere to mix with the meteor smoke. That is also, ironically, when the upper atmosphere is coldest, allowing the ice crystals of NLCs to form. The natural habitat of noctilucent clouds is the Arctic Circle. In recent years, however, they have spread to lower latitudes with sightings as far south as Utah and Colorado. This will likely happen in 2014 as well. Observing tips: Look west 30 to 60 minutes after sunset when the Sun has dipped 6o to 16o below the horizon. spaceweather/
Posted on: Thu, 10 Jul 2014 09:57:12 +0000
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