Dr. Moran says, "‘No two snowflakes are alike' is a widely held assumption. Although all snowflakes are composed of ice crystals having six-sided ... symmetry, they may occur in billions of different forms." Even so, a researcher discovered two identical snowflakes while sampling clouds over Wisconsin in 1988.
"Yes," says Dr. Moran. He explains, "Snow is an agglomeration of ice crystals in the form of flakes that develop in clouds and fall to the Earth's surface. Snowflakes vary in shape and size depending on air temperature and humidity. With decreasing cloud temperature, snowflake crystals occur as needles, dendrites, plates, and columns."
A dendrite snowflake below; a plate snowflake on the right. Both of these images were taken by Wilson "Snowflake" Bentley. For more information, SnowCrystals.com has nice descriptions of different types of snowflakes.
"Snowflake size depends in part on how humid (moist) the air is. At very low temperatures, the humidity is relatively low, and snowflakes tend to be small. Snowflake size also depends on the efficiency with which they collide with one another as they fall through the atmosphere to the ground. At air temperatures near freezing, snowflakes more readily stick together after colliding, and their diameters sometimes reach 2 to 4 inches (5 to 10 centimeters). Snow pellets and snow grains are similar to snowflakes but much smaller. Snow pellets are soft conical or spherical white particles of ice with diameters of 2 to 5 millimeters. Snow grains are flat or elongated opaque white particles of ice, usually less than 1 millimeter in diameter."
Meteorologists measure three things, says Dr. Moran: "The depth of snow that falls between successive observations, the meltwater equivalent of that snowfall, and the depth of snow on the ground at observation time."
Dr. Moran tells us how to measure a storm's snowfall like the experts. "Prior to an anticipated snowfall, place a simple wooden board on the ground ... New snowfall accumulates on the board, and at observation time a ruler is used to measure the snow depth to the board. Record the snowfall ... and sweep the snowboard clean so that it is ready to receive new snowfall. Repeat this process throughout the snow event, and then compare your total snowfall with that reported by the local television or broadcast meteorologist. Note that snowfall is notoriously variable from one place to another ..." depending upon things like temperature, the distance you are from the ocean, and the track of the storm.
"Even though freshly fallen snow appears bright white and clean, it is not," says Dr. Joseph M. Moran of the American Meteorological Society. Dr. Moran is the author of a brand new textbook, Climate Studies: Introduction to Climate Science.
"One of my favorite activities goes a long way to convincing children not to eat snow. You will need a 1- or 2-gallon pail, large paper coffee filter, paper towels, and a magnifying glass … Scoop up a large pail of freshly fallen snow and bring it indoors to a warm room. Set the pail down undisturbed until all the snow melts. Then, over a sink, slowly and carefully pour the meltwater through a paper coffee filter. Set the coffee filter aside on some paper towels until it dries. Next, examine the surface of the dry coffee filter … What do you see? Where did that material come from?"
He adds, "As snowflakes fall through the atmosphere, they intercept and capture a variety of tiny particles that are suspended in the atmosphere and carried by the wind. Most of these particles originated at the Earth's surface. [You can] speculate on what these particles might be."
Dr. Moran says, "This activity requires a sheet of black construction paper or a dark cloth, a magnifying glass, a journal and a pencil. During a snowfall, go outdoors and hold the construction paper or cloth horizontally to catch some snowflakes. Take care that the heat from your breath or fingers does not melt the snowflakes. Using the magnifying glass, examine the individual snowflakes. Describe what [shapes] you see, and draw some of them in your journal. Are any of the snowflakes identical in appearance?"
He notes, "Recording data in a journal is a good introduction to scientific observation and the scientific method."
Little Brother made his own snowflakes this year!
My boys and I are wishing it would snow in our little corner of the world, but no such luck. While the rest of the U.S. has been blanketed in white, we are soggy instead of icy. So, we decided to make some paper snowflakes this week-end.
In my part of the world, the weather is finally starting to look like winter. My boys and I have been anxiously watching The Weather Channel, hoping for a snowy forecast.
So, this week’s tip of the hat goes to Snow
A nod also goes to the American Library Association, for pointing me to this great website through their aptly named listing of Great Websites for Kids.
