Dear Cecil: Here’s a poser...what device or instrument does the Weather Service (it used to be “bureau” but they changed it for show business reasons) use to measure the exact depth of a snowfall? A cup and rule? A graduated window ledge? A demarcated fireplug? E.W., Baltimore
Snowfall is measured with a hand-held linear device that provides a visual readout comparing the depth of snow to a universally understood unit of measure. This device is called a ruler.
What the meteorologist does is, he takes his ruler out to a pile of snow and sticks it in. Generally the snow is piled on what is called a "snow board" (ain’t science complex?), which is wiped clean after every measurement.
In high wind conditions the meteorologist may decide to abandon his snow board and stick his ruler instead into many piles of snow at various spots on what is known as "the ground" to get a reliable figure. If things are really bad he may also opt to stay inside and calculate the snowfall from a graph hooked up to this precipitation gauge, which melts the snow (with anti-freeze), weighs it, and reads out in inches of water.
The density of snow varies, but in general an inch of water is equal to about 10 inches of snow. In the Southern Hemisphere, 10 inches of snow are equal to about an inch of water.
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