A megacryometeor is a very large chunk of ice sometimes called huge hailstones, but do not need to form in thunderstorms.
A megacryometeor is a very large chunk of ice which, despite sharing many textural, hydro-chemical and isotopic features detected in large hailstones, is formed under unusual atmospheric conditions which clearly differ from those of the cumulonimbus cloud scenario (i.e. clear-sky conditions). They are sometimes called huge hailstones, but do not need to form in thunderstorms. Jesus Martinez-Frias, a planetary geologist at the Center for Astrobiology in Madrid, pioneered research into megacryometeors in January 2000 after ice chunks weighing up to 6.6 pounds (3.0 kg) rained on Spain out of cloudless skies for ten days.
Def. pieces of ice falling as precipitation are called hail.
Def. a single ball of hail is called a hailstone.
Def. water ice crystals falling as light white flakes are called snow.
Terminal velocity of hail, or the speed at which hail is falling when it strikes the ground, varies by the diameter of the hail stones. A hail stone of 1 cm (0.39 in) in diameter falls at a rate of 9 metres per second (20 mph), while stones the size of 8 centimetres (3.1 in) in diameter fall at a rate of 48 metres per second (110 mph). Hail stone velocity is dependent on the size of the stone, friction with air it is falling through, the motion of wind it is falling through, collisions with raindrops or other hail stones, and melting as the stones fall through a warmer atmosphere.
On the right is a radarsat image of ice streams flowing into the Filchner-Ronne ice shelf. Annotations outline the Rutford ice stream.
On the right is a radar image of Alfred Ernest Ice Shelf on Ellesmere Island, taken by the ERS-1 satellite.
"A small island obstructs the constant flow of the ice shelf on Queen Maud Land – it is the lighter area at the bottom left of the image [on the right]. From September 2010 until it broke off, Iceberg A 62 was connected to the Fimbul Ice Shelf by a mere 800-metre-wide bridge. Two fissures in the ice from different sides of the bridge approached one another until the break occurred. The images transmitted by the radar satellite TerraSAR-X over a long period of time should enable researchers to achieve a better understanding of how icebergs calve."
- National Severe Storms Laboratory (2006-11-15). Hail Basics. National Oceanic and Atmospheric Administration. Retrieved 2009-08-28.
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