By Maddy Morgan
Any skier or snowboarder knows that snow does not come in just one form. Snowpacks are as variable as the snowflakes that form them. We have all heard the claim that Eskimos have dozens of words for snow (actually, I discovered, just more flexibility in how root words are modified), but what about our terms for snow? Skiers talk about corduroy and corn snow, but the variation in snow types extends beyond the ski slopes.
Snow forms when the atmospheric temperature is at or below freezing. In certain conditions, it is even possible for snow to reach the ground when the ground temperature is 41 degrees Fahrenheit. Freezing atmospheric temperatures, combined with moisture in the air, forms snow crystals. Snow crystals exist in four forms: snowflakes, hoarfrost, graupel, and polycrystals.
- Snowflakes, which we are all familiar with, are clusters of ice crystals that fall from clouds. Their shape is dependent on the conditions in which they are formed and through which they fall.
- Hoarfrost is our name for ice crystals that form on small surfaces that are open to the air. When a surface’s temperature is lower than the frost point of the surrounding air, moisture transforms directly from vapor to solid, forming delicate laces of surficial ice.
- Graupel is the round, pellet-like snow that resembles a softer hail. When ice crystals fall through super-cooled cloud droplets (which remain liquid although they are below freezing temperatures), the droplets freeze to the crystals, forming a clump.
- Polycrystals are flakes made up of many individual crystals.