Snow: The Fun, The Dread, The Science

I was able to go snowshoeing after a two-year hiatus.   It was glorious!  Almost, two winters with no snow was getting really old.  Two minor snowstorms with some cold weather in between resulted in six inches of snow on the ground.  I wandered around the woods on snowshoes for nearly 3 hours while it was snowing.   The wind was light, and the snow was drifting down in large flakes.  When the snow became too heavy on the pine branches, the branch would flex, and the snow came down in a powdery cascade.  The woods were silent except for the scrunching sound my snowshoes made as I glided down a trail.  The snow was piling up on the branches, and fallen trees, creating an infinite variety of snow sculptures.  The untrod upon snow stretched in every direction.  Winter can be beautiful.  

The temperature was in the teens, fortunately I was dressed in light wool clothing as snowshoeing is hard, hot work.  I was quickly sweating and short of breath.  Since, I had not been snowshoeing in a long time, my snowshoe muscles were a bit out of shape.  Frequent rest stops were needed to complete the hike I had envisioned when I left home.  I had a water bottle and a bit of a snack to head off dehydration and hunger. As I was walking, I spotted a few juncos flitting through the woods.  It's amazing that these tiny birds can find enough food to thrive in seemingly barren winter woods.  

I emerged from the woods with tired legs, covered in snow, and a frosty mustache and beard.  It was a perfect snowshoe outing.  Getting up close and personal with the snow is inevitable during Wisconsin winters.  

We Wisconsinites have a love-hate relationship with snow.   We love to drive snowmobiles and 4-wheelers and ride fat tire bikes in the snow but dread commuting on snow-covered and slippery roads.  Breaking a sweat while shoveling snow is, at best, considered a necessary evil.  However, sweating profusely while cross-country skiing or snowshoeing is grand recreation.  Sledding, building snowmen, and making snow angels is great fun for some, while others look at the snow and say, “Oh, it's COLD outside,“  cover up with a blanket, and read while sipping hot chocolate.  

What is snow?

What is the mysterious and magical substance that we love and loathe?  The National Weather Service defines snow as precipitation in the form of ice crystals, mainly of intricately branched, hexagonal form and often agglomerated into snowflakes, formed directly from the freezing [deposition] of the water vapor in the air.  That’s a lot for a semi-frosted brain to digest right after a fun snowshoeing hike.  The key term in that sentence is “ice crystals.”  Hence, snow is frozen water in crystal form.  So how does a bunch of water vapor floating around high in the atmosphere end up as something as intricate and delicate as an ice crystal?  The National Oceanic and Atmospheric Administration (NOAA) describes the process on their SCIJinks website:

Snow is not simply a frozen droplet of water falling from a cloud. What makes a snowflake different is that it forms slowly, and that it grows in the cloud.
A snowflake is born when water vapor travels through the air and condenses (changes from a gas to a solid) on a particle. There, it forms a slowly growing crystal. There are two basic ways that the vapor can condense. Each way plays a big role in the shape that the snowflake will eventually take. 
The first way is to form what are called ‘facets.' A facet is essentially a flat face on a 3D shape, like a prism. They form naturally when a crystal grows. In ice crystals, the shape they take mirrors the shape of the molecules forming the crystal. The crystal structure of frozen ice is a six-sided shape. Therefore an icy facet is six-sided as well. That is where the symmetry in a snowflake comes from. The second way to grow a snowflake is to form branches. Not surprisingly, this is what creates those beautiful tree-like structures. Branches form because water vapor will condense on the first thing it touches. If there is a small bump on a flake’s surface, the vapor will condense there instead of traveling any further. Now the bump is bigger and even more likely to ‘catch’ water vapor at that point. The process repeats itself, and a branch is formed!
While the snowflake generally starts as a prism with six facets, its growth can switch back and forth between creating facets and forming branches. And both processes can occur at the same time. Nearly imperceptible changes in temperature and the amount of water in the air change how the molecules act and how they condense.
Imagine a growing snowflake in a cloud. As it blows back and forth, it experiences all sorts of changing conditions. There are different temperatures and moisture levels in different parts of the cloud. There are also different conditions at the microscopic level. The order in which it experiences those changes and how long each set of conditions lasts determines the shape it makes.
How likely would it be for two snowflakes to experience the same exact same conditions all the way down to the microscopic level? Astronomically unlikely! That’s why you will never find two truly identical flakes!

Snowflake Shapes

Scientists have developed multiple systems for classifying the various shapes of snowflakes.  
One system has 16 different categories of snowflake types. Another system has 39 different types of snowflakes with 121 sub-types.  Dang, if I was trying to divide the snowflakes caught in my beard after a snowshoe hike into 121 sub-types, I would need more than one hot spiced apple cider to accomplish that task.  Overall, the various types of snowflakes can be lumped into eight categories :

   • Plane crystals 
   • Combination of column & plane crystals 
   • Aggregation of snow crystals 
   • Rimed snow crystals 
   • Germs of ice crystals 
   • Irregular snow particles 
   • Other solid precipitation. 
   • Column crystals
I would really like to see the setup scientists use to capture and photograph individual snowflakes.  

Some interesting Tidbits About Snow.  

When snow falls in quantities, it creates that “Blanket of White” we are so fond of in December but despise by the end of January.  The white color of snow is the result of the ice crystals reflecting the full spectrum of light back at us.  If one literally digs a little deeper into the snow, the reflected sunlight will take on a blueish hue.  The ice crystals absorb red light a little bit per crystal, so as the light penetrates deeper into the snow, blue is the main light spectrum being reflected.  
One of the main ingredients of snow on the ground is air.  When you are smooshing snow into a snowball, you are mainly smooshing the air out of the snow before flinging it at your best friend.  
Snow on the ground is not static.  It compacts as it sits on the ground.  I am a volunteer CoCoRaHS data collector so I measure snow depth nearly every day there is snow on the ground, and the depth of new fallen snow can decrease as much as an inch in 24 hours even in very cold temperatures.  The compaction of the snow is due to the ice crystals breaking down and the amount of air in the snow lessening.  
A crust forms when thawing snow refreezes or strong winds break down the ice crystals and compacts the snow.

The sound snow makes when it is walked or driven on can help indicate the air temperature.  The colder the snow is the more friction there is between the snow particles, hence the familiar snow crunch sound.   When you walk outside to partake in your favorite winter sport, and the snow is crunchy and your nose hairs are frozen, it is time to do a quick reevaluation of the number of layers of clothing you are wearing before venturing into the frozen tundra.
Twelve to eighteen inches of snow is a highly effective insulation from the cold.   So, if you are stuck in the middle of nowhere during a blizzard, dig a snow cave into a tall drift, and you’ll be warm and toasty. 
Since we live in a place where snow and the accompanying cold is still a fact of life, the best way to deal with snow is to understand the science, appreciate the beauty, and get out and play in the snow.