As we begin a new year, it seems many of us are talking about snow here in the Northeast. Here in New Jersey, we have already had two large snow storms. The first one, which occurred just after the Christmas holiday, dumped more then 20 inches on our little town, forcing us to dig a path in the backyard for our poor dog! Last week’s storm was milder, with only 8-9 inches, but was enough to delight my daughter with a day off from school and an afternoon sledding with her friends. So, have you ever wondered what snow is and how it forms?
Snow is frozen precipitation that forms directly from water vapor into solid crystals. Temperatures need to be below freezing in all or most of the atmosphere from the surface to cloud level for snow to form. Snow falls to earth either as individual crystals or as snowflakes, which are large masses of crystals. Snow crystals usually form in hexagonal or six-sided shapes.
The shape of the crystals depends on the air temperature. In colder air, needle and rod shapes form, while more complicated shapes form in warmer air. Because of this, no two snow flakes are ever identical! You can check out a wonderful guide to snowflakes to see fantastic pictures and information about the diversity of snowflake shapes and sizes. If you want to get a closer look yourself, you can capture snowflakes on chilled glass microscope slide. You can preserve the snowflake sample using artist’s spray fixative (such as Krylon® “Crystal Clear”) before you try to view them under the microscope. Use a low-power binocular microscope to examine your preserved specimen.
Is all snowfall the same?
Anyone who has had to shovel snow, made a snowman, or even tried to sled on snow knows that all snow is not created equal. Once snow lands on the ground, it can be categorized as powdery and fluffy, or granular when it’s melting and refreezing. Eventually, snow can turn to ice after multiple melting and refreezing cycles, and finally into snow pack.
Try this at home
Next time it snows, take a core of the snow from your backyard or neighborhood. To do this, place a small piece of plywood in an open area of your backyard or an open lot. Use a ruler to measure how many inches of snow has fallen on the plywood. Collect a sample of the snow using your rain gauge and allow the snow in the cylinder to melt. How many inches of melted snow do you have in your sample?
What you will find: Snow that falls through very cold, dry air will not accumulate lots of crystals and will fall as dry snow. Dry snow has a very low water content. It can take as much as 10-15 inches of dry snow to melt to make an inch of water!
Snow that falls through moist atmospheric air that is not too cold will create larger crystals and fall as wet snow. In this case, 6-7 inches of wet snow can make an inch of water. Post a comment on our site about what you find when you do this experiment.
Estimate how fast it is snowing: Watch snowflakes as they fall past an object of known height, such as a building. We can calculate the speed by dividing the distance they travel over time (Speed = Distance/Time). So for example, if a building is made of 2.75″ thick bricks with 1/2″ of mortar between rows of bricks, then every 10 rows of bricks equals approximately three feet (32.5″ to be exact). On average, snowflakes fall at a speed of approximately 3 feet per second, or 10 rows of bricks every second. [Idea courtesy Marcia Politovich.]
When will it snow next?
Thanks to many major advances in technology, we are able to observe and forecast the weather better than ever before. Today’s weather models are fairly accurate at predicting conditions up to a week out, though forecasters still have trouble with large storms like blizzards and hurricanes after a couple days.
When it comes to predicting snowfall, the National Operational Hydrologic Remote Sensing Center, has some wonderful real-time datasets to play with.
National Snow Analyses website contains neat images on recent snowfall and ground snow cover. The animations are particularly interesting, because you can observe recent snow storms as they cross the US. At the bottom of the page is a written snowfall forecast which is updated daily. You can download snow pictures from around the country of snow and its impact on rivers and streams.
You can learn how to be a meteorologist, or someone who studies weather, and learn how to make a weather forecast. But don’t stop here – become a weather watcher and citizen scientist with the NJ Community Collaborative Rain Hail & Snow Network. But if you really want to know more about snow, you must check in with our State Climatologist, Dr. David Robinson. Dr. Robinson tells me that here in New Jersey our current snow total ranks as the 9th highest full seasonal total since observations commenced in the winter of 1893/94. We are only 8.5″ from assuming second place record but still well behind the record winter of 1995/96, when 76.5″ fell. But there is a lot of winter still to go! I hope I peaked your interest in the everyday science of snow. See you next month when we will talk about more science of everyday living.