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| Photo courtesy Colleen Hart, The Weather Channel Facebook Page |
Sometime this winter, you may be fortunate enough to see hoarfrost in your landscape. But look quickly, because it will disappear with sunlight.
According to the Old English dictionary (c. 1290), hoarfrost is defined as "expressing the resemblance of white feathers of frost to an old man's beard." No, this isn’t frost on performance-enhancing drugs, but it can be quite different from your normal frost! Colleen Hart of The Weather Channel provides the following facts about hoarfrost.
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| Photo by Donna Duffy |
To produce any frost, you need water vapor (gaseous form of water) in the air over cold ground with a surface dew point at least as cold as 32 degrees. When these water vapor molecules contact a subfreezing surface, such as a blade of grass, they jump directly from the gas state to solid state, a process known as "deposition", leading to a coating of tiny ice crystals.
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| Photo by Donna Duffy |
So what provides the boost for frost to grow into hoarfrost like this? Generally speaking, you want a much more moist air mass in place. In late fall, winter or early spring, one or more days in a row of freezing fog (fog with air temperatures of 32 degrees or colder) is a perfect scenario. With more moisture in the air, the interlocking crystal patterns of frost become more intricate and much larger, building up to a greater depth on tree branches, signs, fences, anything. This is hoarfrost.
For more information about hoarfrost, check out the Weather Channel’s Hoarfrost: The Science Behind Frost on Steroids.
