From December to March, throughout the United States, sizable snow falls are no surprise. Some are delighted by snow. Others dread it. Neither speeds up or prevents a snow fall. Except through hard work on streets, sidewalks, and such, snow only goes go away by natural means.
Natural Snow RemovalOne natural factor that removes snow is an increase in outdoor temperature. The greater the temperature, the faster snow melts. Of course it melts from the top down or the outside in. But temperature is not the only factor involved in natural snow removal.
SunlightThe sun can shine brightly. Snow disappears more quickly in sunny than in shady places, even at very cold temperatures. Radiant energy from the sun battles with cold temperatures in a kind of push-pull fashion. It puts a glaze on the surface of the snow due to a slight melting-freezing action. With an assist from a property called vapor pressure, the snow eventually evaporates, disappears.
Vapor PressureFor many low melting solids vapor pressure plays an important part in their behavior. Notice how the purple solid iodine behaves in the video below.
Although heat speeds up the process, sublimation (the conversion of a solid directly to a vapor) occurs even at room temperature. For iodine, this is visible due to its purple vapors. It is similar with snow, though it goes unseen.
The following video discusses vapor pressure in a more general sense.
Wind and Atmospheric PressureWind blows snow. Yet it also assists in its sublimation, that is in the vapor pressure mechanism. A lowering in atmospheric pressure does similarly, though to a lesser degree. And did I fail to mention that wind blowing across snow’s surface generates friction and so heat? Of course, that wind can also take heat away…
Below the SurfaceThe bottom layer of snow in close contact with soil and rocks can be likened to the snow on highways previously treated with a salt or calcium chloride coating. These chemicals lower the freezing point of water.
Soluble substances in soil and rocks do similarly. So snow, even at the normal freezing temperature, that is in touch with the ground slowly enters the soil. Add to that the fact that the ground is ordinarily warmer than the snow, and it takes little time for a typical snow to melt and disappear.
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