Posts Tagged ‘sleet’
The Wonder of a Snowflake
Thursday, February 10th, 2011
Stellar snowflake by Kenneth Libbrecht; photo thanks to Smithsonian Photography Initiative
I have plenty of good company this winter when I say I have mountains of snow outside my house. Literally, mountains! It has been difficult to go or do anything without considering the snow. My love/hate relationship is determined on whether I’m going snowshoeing or driving. In any case, I sat down and got to know snow intimately.
Why are snowflakes all 6-sided?
The molecular structure of any mineral dictates its crystalline form. Snowflakes are made of water vapor, H2O, where two hydrogen atoms are bonded to an oxygen atom. Under the right conditions, these water vapor molecules bond together, aligning themselves into hexagonal groupings upon which more water vapor builds.
How are snowflakes formed?
“No two are exactly alike.” Have you heard that saying about snowflakes? Snowflakes form in a cloud, an environment of water vapor. There are varying conditions of humidity and temperatures and air currents and even dirt and dusts particles throughout the cloud. The hexagonal plate that every snowflake starts out as, tumbles through the cloud, attracting more water vapor that adds to each of the 6 arms or perhaps melting a bit before growing again. Since each snowflake encounters slightly different conditions in the cloud, vapor crystallization varies for each one, making it improbable that any two would be identical.
Why isn’t all snow in the form of flakes?
Temperature has everything to do with the form snow takes. Really cold temperatures produce intricately branched flakes, a condition found typically in very high clouds. Under warmer conditions, snowflakes grow more slowly and have a smoother, less branched look. Mid and low level clouds therefore produce 6-sided needles and flat hexagons and other shapes. Of course if snow melts and becomes rain as it descends to earth, we could have something completely different. Sleet is frozen rain that falls as icy pellets. Freezing rain is supercooled water droplets that forms ice upon impact. Graupel is light, fragile snowy pellets formed when supercooled water droplets condense onto snowflakes.
So, the next time it snows, don’t dismay. Take a minute to closely examine the intricately formed flake on the sleeve of your jacket. That snowflake has gone through a lot to get to you.