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Multi-Instrument Measurements of Noctilucent Clouds in Coordination with the AIM Satellite

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Notilucent clouds (NLC) are beautiful high-latitude summer time phenomena that were first reported over 100 years ago. They are visible to the naked eye only during twilight when the sun in between 6-16° below the horizon. NLC are very tenuous, consisting of microscopic ice particles (typically 40 nm) that nucleate and grow in the dynamically driven, extremely cold (<150 K) summer mesopause region. NLC appear silver blue or white in color and are often characterized by gravity waves and instabilities. Satellite observations (termed Polar Mesospheric Clouds, PMC's) have extended these clouds measurements into the northern and southern polar cap regions (where they are most frequently observed). Over the past 3 decades, satellite measurements of PMCs have revealed significant increase in their frequency of occurrence and brightness (e. g. Deland et al, 2007) raising speculation concerning possible links with climate change in the upper atmosphere.


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