Waaaay back when I started out on the capital “I” Internet with an online publication called the Northern Michigan Journal. For over five years I edited NMJ, producing around 4 issues a year that featured some interesting work from a wide range of writers & artists.
Two of these were my friends Jerry Dennis and Glenn Wolff, a writer/artist duo who collaborated on several books. Their first was called It’s Raining Frogs & Fishes: Four Seasons of Natural Phenomena and Oddities of the Sky, a fascinating romp through the oddities and beauties of the natural world through Jerry’s captivating prose and Glenn’s engaging drawings. You can click that link to learn more about the book from Jerry’s website. Trust me, it’s the perfect gift for the nature lover or scientist in your life!
There is more to the birth of a snowflake than Aristotle’s assertion that “when a cloud freezes there is snow.” Snow is not merely frozen rain. Rain occasionally freezes, falling to the ground as sleet or freezing rain, but snow originates independent of atmospheric drops of water. Individual ice crystals for high in the atmosphere when water vapor freezes around dust or other particulates. Without particles to serve as condensation nuclei, water vapor can be cooled to -40 degrees Fahrenheit before freezing occurs. A supercooled cloud of this sort seeded with a few particles often escalates into a snowstorm. The individual crystals collect additional molecules of water vapor one at a time, building on one another symmetrically in a rapidly growing, widening circle. Temperature, wind, humidity, and even barometric pressure will determine the growth and ultimate form of the crystal. Large and elaborate crystals for at higher temperatures and humidity while, while the small, basic crystals such as those common in polar regions form when temperature and humidity are very low. As the crystals fall they bump against each other, breaking off pieces of ice that in turn serve as nuclei for new crystals. As they pass through warmer layers of air they adhere to one another, congregating into snowflakes that may contain a thousand or more crystals.
Snowflakes, then, are aggregates of snow crystals. When the temperature is near or slightly above freezing, snowflakes become wet, adhere to other flakes, and grow to two or three inches in diameter. On very rare occasions, they can grow larger yet. According to a report in a 1915 issue of Monthly Weather Review, a snowfall on January 28, 1887 dropped flakes “larger than milk pans,” measuring fifteen inches in diameter by eight inches thick across several square miles near Fort Keogh, Montana.
Only when the temperature remains consistently below freezing will complete, individual crystals fall to the ground. If the temperature of the cloud they form in and the air they descend through is warmer than 27 degrees Fahrenheit, the crystals tend to be flat and hexagonal. Between 27 and 23 degrees, they tend to be needle-shaped. Between 23 and 18 they are likely to be hollow and columnar, with prismatic sides. At temperatures below 18 they can be columnar, hexagonal, or fernlike. Virtually all have six sides. That hexagonal tendency is something of a mystery, although some scientists suggest it is produced by electrical charges in the crystals, while others say it is basic to the molecular structure of water molecules. The atoms in a molecule of H20 are arranged, in physicist Hans C. von Baeyer’s graphic description, “with two little hydrogens stuck onto a big oxygen like ears on a Mickey Mouse’s head.” Scientists like von Baeyer believe that the angle at which the hydrogen molecules protrude from the oxygen atom–about 120 degrees–causes snow crystals to grow to a six-pointed symmetry that repeats the molecular structure of water.
Read on for much more including whether or not two snow crystals are alike, heavy snowfalls and snow words & myths.