Measuring Snow

Have you ever read a weather report telling how much snow has fallen in a winter storm? Have you ever seen the amount of snow given in two different numbers, one much larger than the other? What is going on here?

One measure of snow is snow depth. This is found by picking a spot a little away from a warm house or any large object which could block falling snow. Snow depth is measured with a ruler to find out how many inches (or in many parts of the world, how many centimeters) fell. One good way to do this is to put a white painted board on the ground and measure the depth of snow on the board. You can measure the depth of snow on the board every day and then clean it off. Some people just use the top of their picnic table or wooden deck. This number is pretty easy to understand. It shows how many inches or centimeters of snow fell since the last time the spot was brushed clear of snow.

If you are going skiing or sledding, you may also want to know the total depth of snow on the ground. You can do this by taking a yard stick or meter stick outside and measuring the snow in several different places. Then find the average depth of snow. Add up the depth of snow from all the spots and then divide the total by the number of spots you measured. This will be the average snow depth.

Visit FactMonster for some information about record snowfalls.

To understand the other number given in weather reports, you need to find out a little more about snow. Go outside and fill a container with snow. Don't pack the container, fill it gently. Put the container in a warm spot so that the snow melts. Is the water left after the snow melts as deep as the snow was? Do you think there is a lot of air space in snow? Do you think snow always has the same amount of water and air in it? How could you find out?

So, the other number given in some weather reports is the depth of the melted snow. This is the amount of rain that would have fallen if the temperature had been higher. Rain is measured in inches or centimeters instead of gallons or liters because a volume measurement like a gallon has no meaning without more information. You would need to measure gallons per acre or gallons per square yard. It is much easier to find out a simple depth of rain inside a container. We measure rain, and snow moisture, in inches or centimeters.

One way to explore the water content of snow is to place a rain gauge outside and let snow fall into it. Next, measure the depth of snow in the gauge. Then measure the depth of water left in it when the snow has melted. A coffee can can be used as a simple rain gauge. Place the can outside during a snow fall, then go out and measure the depth of snow in the can after the snow has stopped. Bring it inside long enough to melt the snow and then measure the depth of water.

If it is windy while snow is falling, your rain gauge might not catch much snow. You might try "cutting a biscuit" of snow from your snow board to get a better measure of the snow fall. Turn your rain gauge upside down and push it into the snow on the snow board. Take this inside to melt.

Try collecting and measuring snow and the water it contains on different days. Is there a difference? Does it matter what temperature it was outside while the snow was falling? Is there more water in snow which fell on a cold day or a warm day? Can you think of other things which might cause some snow to have more water than other snow?

Go to the National Oceanic and Atmospheric Administration website for the official National Weather Service procedure for measuring snow.

You might want to order the Snow Booklet if you really get interested in this weather topic.
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