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Noctilucent Clouds Likely Caused By Shuttle Launches
icebike writes "In our recent discussion of the phenomenon of noctilucent clouds, there was some suggestions that these might be the product of global warming due to moisture being lofted high into the atmosphere. It now appears that these clouds are simply the product of Shuttle launches. In a story about the Tunguska blast, Science News says: 'Each launch of a space shuttle, which burns a combination of liquid hydrogen and liquid oxygen as fuel, pumps about 300 metric tons of water vapor into the atmosphere at altitudes between 100 and 115 kilometers. Soon after the January 16, 2003, launch of the shuttle Columbia, a liftoff that took place just after the height of summer in the Southern Hemisphere, noctilucent clouds appeared over Antarctica. Similarly, a widespread display of the night-shining clouds showed up over Alaska two days after the shuttle Endeavour blasted off on August 8, 2007. Previous studies show that in both instances those clouds included material from the shuttle plumes.' So, man-made after all?"
The previous Slashdot thread included the tidbit that the first noctilucent clouds mentioned in recorded history were in 1887 (also noted here). So unless someone was using hydrogen-oxygen rocketry almost a full century before the first shuttle launch, it would seem that they are not purely anthropogenic.
Cheers,
"What in the name of Fats Waller is that?"
"A four-foot prune."
From June, 2003: .... note the last sentence.
http://apod.nasa.gov/apod/ap030615.html
6 years.
Sometimes it takes main stream media a while to catch on.
Note that this APOD entry has further links to US Navy research on the topic.
Noctilucent clouds occur over a very small altitude range (about 82-84 km) Observations of the same cloud from different locations can be used to find the height by triangulation. ISTR that the 1887 observation did this and that it is therefore a genuine observation of NLC.
The question of whether there were no NLC before this date was a contentious one last time I asked. Some make the argument that NLC are very distinctive and that if they were there we would have records going back to the Viking era, as we do with the Aurora Borealis. Others, however, argue that NLC look sufficiently like other clouds and are sufficiently unremarkable to the casual observer that it is not surprising that there are no descriptions prior to 1887. (Remember that the idea that it is worth naming and describing clouds only really goes back to Luke Howard in the early 1800s.)