High WinterEditor Raymond Carlson writes about the birth of a snowflake (an excerpt from our December 1962 issue)
Photograph by David Muench
Moving air, or the atmosphere in motion, a simple description of wind, is made up of invisible water vapor, oxygen, nitrogen and other elements. When water vapor of sufficient strength concentrates in the atmosphere, the relative humidities rise to eighty or ninety percent, and the vapor will condense on any handy particle in the atmosphere. To get really professional, we would like to point out that these particles are called nuclei, as they form the loci on which water vapor may condense. Sea salts from the Pacific, formed from evaporation of sea wave and ocean bubble spray, are the most important nuclei in the atmosphere; so the little snowflake we hope eventually to welcome this winter in the high country of Arizona, nine times out of ten, will have as its inner core a molecule of salt from the Pacific. At least we hope so because other nuclei in the atmosphere are formed by industrial pollution, smoke from forest and grass fires, volcanic dust, just plain dust kicked up by the wind from city street or from an acre of farmland, and other impurities man and Nature can create from the land that supports them. Fresh air, did someone say? It is surprising how un-fresh fresh air can be. If we were a snowflake we think it much more romantic to have as our nucleus a particle of sea salt carried by the wind from the distant ocean.
The sky darkens over the Pacific Coast, to our west, and the wind pushes in a storm, boiling dark clouds of water vapor and all the other ingredients to be found in the atmosphere.
In winter, over the high coastal ranges, when temperatures fall below freezing, water vapor in the atmosphere condenses on the nucleus in the form of a single white or translucent ice crystal. Weather forecast for tomorrow: snow!
Nature has come up with many strange and wonderful things but perhaps nothing as delicate and wonderful as the ice crystal formed by water vapor in the atmosphere condensing around a nucleus (sea salt particle, etc.) and then freezing. A snowflake has been created by Divine sculpture usually in a complex branched hexagonal (six-sided) form. In single crystals we find beautiful, infinite variety of form, although normal snowflakes are composed of broken single crystals, fragments or clusters of such crystals, no less beautiful.
One man with an inquisitive mind and a microphotographic camera photographed thousands of snowflakes and published the results in a book. (William A. Bentley, Snow Crystals.) He found no two snowflakes alike. Snowflakes come in hexagonal columns and plates, simple or with a variety of extensions at corners, smaller hexagonal plates with long rays or plume-like extensions and also three and twelve-sided forms. An artist would have to be very talented, indeed, to create a form as delicately beautiful as that of a snowflake!
Snowflakes, then, come in all sizes and forms. A snowflake may grow as large as three to four inches in diameter, and it has been reported that in extremely still air (a snowflake falling through turbulent air naturally gets battered about a bit) snowflakes up to ten inches in diameter have been measured. (Imagine being slapped in the face with a ten-inch snowflake!)
The snows we receive during our high winter have a personality of their own. Snow densities vary tremendously, dependent as they are on the temperature of the air for their moisture content. When it is real, real cold, -20 to -40 degrees, four or five inches of snow will result in only a few hundredths of an inch of water when melted. When the temperature is from around -20 to around zero, snowflakes tend to be light and dry, squeaky underfoot. This type will take about fifteen to twenty inches to make one inch of water when melted. Then we have the "wet" type of snow when snowflakes become fat, moist and large as temperatures approach 32 degrees. This type of snow, perfect for a snowball fight, may result in an inch of water from four to seven inches of snow depth.
In Arizona, elevation is very important in the accumulation of snow. Snow in the desert is so rare as almost to be a phenomenon. You have to climb high for snow in our state. Here are some figures, annual average snowfall: Bright Angel on the North Rim of Grand Canyon (elevation 8,400 feet) 133 inches; Maverick (7,800 feet) 88 inches; McNary (7,320 feet) 94 inches; Alpine (8,000 feet) 65 inches; Flagstaff (6,993 feet) 69 inches; South Rim, Grand Canyon (6,965 feet) 62 inches; Williams (6,750 feet) 67 inches.
We in Arizona welcome high winter. It means winter sports and recreation, beautiful vistas of snow-clad forests, and most of all when the thaw comes in Spring it means water, from one to two million acre feet, filling our reservoirs to be used judiciously for the benefit of all of us.
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