Clouds from Space: Noctilucent AKA Polar Mesospheric Clouds

Astronomy, Meteorology
[caption id="attachment_24116" align="alignright" width="480"] An International Space Station image of noctilucent clouds. Image by ISS/NASA[/caption] A cloud is a visible collection of condensed water vapor or ice crystals located within the atmosphere. Clouds form only when there is sufficient humidity to form droplets or crystals upon a suitable quantity of microscopic particles (called an aerosol). Particle types include sand, pollen, spores, smoke, exhaust pollutants, and sea salt. But the formation of so-called “night shining” or ‘noctilucent’ clouds (NLCs) requires something special. Noctilucent clouds are sometimes (especially in scientific circles) called polar mesospheric clouds (PMCs) – their appearance is striking. Their altitude is remarkable. They reside an amazing 50 miles above Earth’s surface. By comparison, cumulonimbus (storm) clouds reach elevations of only approximately 15 miles, and cumulus (fair weather) clouds are…
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