Hey Ray: How 'Graupel' forms
PITTSBURGH (KDKA) - When we get to the wintry months, you may hear a particular word... "Graupel"!
Graupel is soft, small pellets of snow. They sort of look like little, Styrofoam balls. They are quite fragile and easily disintegrate when you try to pick up the little pellets.
These little snow pellets are certainly not your typical snowflake. Graupel is formed when a snowflake is formed, then falls through water droplets that are supercooled. That means that the liquid droplets drop to temperatures below freezing, without initially turning to ice.
You may remember the experiment we did an experiment about that before. That was our instantly freezing water experiment, and we were using supercooled water.
The water droplets stay in liquid form until they have something to freeze to...that's the snowflake! So, those droplets crystalize when they come into contact with that snowflake. This is a process known as riming.
The more riming that occurs, the bigger the graupel pellet will become! As it falls, the graupel will become more of a tiny, soft snowball.
Graupel is also related to hail because of that riming process. Some people even refer to it as "Soft hail". Graupel is typically white and opaque. Unlike hail though, graupel is soft and falls apart quite easily. Graupel is also usually smaller than hail, too.
Why does it have such a weird name?
According to the Merriam-Webster Dictionary, the word graupel is rooted in German and means "Pearl Barley". They also note that its first use in a weather report was in an 1889 weather report. From there, the name "graupel" has stuck!