Wising Up To Winter Water Types
Love it or hate it, water is going to be all over Lincoln, NE this winter in a form recognizable to all Midwesterners: snow! We’ve already had a couple of flurries this season, and if the Farmer’s Almanac is right (which it almost always is) there’s plenty more snow where those came from. Higher than normal precipitation levels and projected all over the country this winter, and more water means more snow. Whether you’re sledding, shoveling it off your driveway, making snow angels, or scraping it off your windshield, you’ve probably noticed that certain types of snow look and feel different than others. There are lots of factors which work together to determine how heavy snow will feel, how wet or “powdery” it is, and how well it sticks to surfaces. Strap on your snow boots, because this week we’re investigating the different types of snow, what they’re called, and how they’re formed. The following blog recognizes information from National Snow and Ice Data Center’s regarding snow types.
Snowflakes which morph into round, opaque pellets when water vapor in the air freezes to them are called graupel. Though the term comes from the German root work “graupeln” meaning “soft hail,” graupel and hail actually have distinct characteristics which separate them. To put it simply, if you were to pick up a piece of hail, it would feel like a round ice cube: solid and hard. Graupel, on the other hand, would fall to pieces if pinched between your fingers.
When you’ve been out scraping your windshield in the winter, have you noticed that your rear view mirrors often have small outlines made of ice crystals? It looks almost fuzzy, like if you were to take your hand out of your glove and touch it it would feel soft. Well, that can happen on fences, stop signs, trees, or anything else subject to withstanding wind and snow, and the result is called hoarfrost. Hoarfrost is formed when the surface temperature of an object is colder than the frost point of the air around it. Because if this, water skips the liquid phase and immediately becomes a solid upon contact with the object. The “outline” look happens because the water vapor in the warmer air will slowly build interlocking ice crystals building out from the surface of whatever object they are accumulating on.
One of the easiest types of snow to identify, polycrystals are just snowflakes which are comprised of multiple different ice crystals. Typically characterized by a more granular feeling, polycrystals are more rigid and give more of a “crunch” when walked on than their powdery, snowflake counterpart. This is the type of snow everyone complains about when scraping their windshields on a cold winter morning.
The most recognizable type of snow is the standard snowflake. They consist of one or more ice crystals made from supercooled cloud water which amalgamate around a dust particle and fall to Earth. Though it’s popular to say that each snowflake is uniquely different, that is not strictly true. While each is different, there are eight categories into which snowflakes can be sorted based on their shape. The eight types are: needle crystal, columnar crystal, plate crystal, combination of columnar and plate crystals, columnar crystal with extended side planes, rimed crystal, irregular snow crystal, and germ of snow crystal. All of these have base shapes which differ slightly based on the temperature and humidity conditions it undergoes before it reaches the ground.