Why snow turns into gas

12:16 AM, Dec 13, 2013   |    comments
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A News10 viewer was commenting how his snow seemed to be disappearing even though temperatures were still freezing and there wasn't much wind.

When temperatures are cold enough, the snow can go directly from a solid to a gas. This is called sublimation. Usually this process takes a long time, but sunlight can speed the necessary energy needed for solid ice molecules to escape.

The sun will have the most influence on sublimation when it is higher in the sky. At lower angles, the sun's rays have to travel through more of Earth's atmosphere, which minimizes its intensity. During the early part of the winter, the sun's influence on sublimation isn't as strong as later in the season.

Freeze-drying food also uses the process of sublimation. First, the food is frozen. Then the item is placed under reduced pressure or vacuum, which will allow the water to sublimate.


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