I’ve always wondered what the difference was between each of these things that fell from the sky. After learning about them, there are so many differences between them! Do you know the difference between Graupel, Hail, or Sleet?
Graupel is a snow particle (or snow pellet) that is irregularly-shaped. Graupel is formed when the snow pelts collect snow crystals, rian, or partially melted snow stick, like glue, to the snow pellet – which adds an icy layer on the outside. Graupel is usually no bigger than 5mm wide, and typically resembles a “chunkier” snowflake. Below is a picture of graupel.
Hail forms in convective processes, like severe thunderstorms or cumuliform clouds. It can either be white or more of an opaque color and is considered to be bigger than 5mm in diameter (which is already bigger than any types of graupel). In order to be considered hail, it must form within a convective process which allows the growth of the ice. A good example of where hail growth occurs is within thunderstorm clouds. Within the upper region of the cloud, water droplets freeze together. When they start to fall from the cloud, the hailstones get pushed back up by the updraft of the storm. When the hailstone is pushed back up into the cloud, it comes in contact with more water droplets, which adds another layer to the hailstone. Eventually, when the hailstone becomes too heavy for the cloud to hold, it falls to the ground. Below is a picture of hailstones.
Sleet is different from hail because its translucent and is usually a ball less than 5mm in diameter. Sleet is formed by the refreezing of liquid raindrops or the partial melting of a snowflake. The best example of this is in the winter. When the precipitation from a storm falls as a snowflake, it will enter a warm pocket and completely melt until it hits a colder pocket of air near the surface and freezes as a ball of ice. When it hits the ground it will be a clear ball of ice, which is considered sleet. The main difference between sleet and graupel is that sleet is the re-freezing of liquid raindrops or partial melting of a snowflake, while graupel doesn’t re-freeze, but rather collects melted snow. Below is a photo of sleet.
Now that you know the difference, I hope you’ll be able to recognize these when they fall from the sky.
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Credits: National Geographic, National Weather Service
@2019 Weather Forecaster Allison Finch