Tiny ‘ice-lollies’ may pull water from the atmosphere
\AIS LOL-ee\ n.
A small ice particle made of a needle-shaped ice crystal and a single drizzle-sized water droplet
Right now, somewhere in the world, it could be raining lollies. A 2009 research flight through clouds above the British Isles gathered ice particles with an unusually sweet look. Each millimeter-sized particle consisted of a stick-shaped piece of ice with a single water droplet frozen on the end, giving it the appearance of a lollipop. Atmospheric scientist Stavros Keppas of the University of Manchester in England and colleagues report the discovery of the atmospheric confections in a paper to be published in Geophysical Research Letters.
The ice-lollies, as Keppas dubs them, start as pristine, six-sided ice crystals formed in the tops of clouds. A stream of relatively warm air cut through the clouds, creating a zone of water droplets on the verge of freezing, the scientists found during the research flight. As the crystals fell through the warmer layer, droplets grabbed on, froze in place and then exploded, forming ice needles. When other droplets froze onto those needles, ice-lollies formed. Like real lollipops in a kindergarten class, the little lollies may not last long, probably melting or deforming before hitting the ground. But on their way, they may drain moisture from clouds, Keppas says.
A newly discovered ice particle shape is made of a needle-shaped “stick” with a frozen water droplet attached, making it a lollipop doppelgänger. Observed variations of the shape at different temperatures and altitudes are shown.
Editor's Note: This story was updated on May 11, 2017, to correct when the ice needles formed, which occurred after the ice crystals picked up a near-freezing water droplets, then exploded.
S.C.H. Keppas et al. Ice-Lollies: An ice particle generated in supercooled conveyor belts. Geophysical Research Letters, in press, 2017. doi: 10.1002/2017GL073441.
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