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Snow
Snow, transparent ice crystals formed around dust or other small
particulates in the atmosphere when water vapor condenses at temperatures
below the freezing point. Partly melted crystals usually cling together to
form snowflakes, which may in rare cases grow in size up to 7 to 10 cm (3
to 4 in) in diameter.
Structurally, elemental crystals of snow occur in any of various
hexagonal forms, depending upon exact atmospheric temperatures during
formation. Among these six-sided, basically symmetrical shapes are needle,
columnar or stud, platelike, and star-shaped crystalline types. Because of
the infinite variability of weather conditions, every snow crystal is
unique in its precise configuration, and it is the large number of
reflecting surfaces of the crystal that make snow appear white. The longer
rays that constitute the arms of the six-rayed stars are generally hollow
tubes; they are evidently built up by additions to the edge of an original
crystal.
Snowfall measurement is usually stated as depth in centimeters, or other
unit, of newly fallen snow; it is also measured in terms of the depth of
the layer of water that would result if the snow were melted in place; 25-
30 cm (10-12 in) of snow melts to 2.5 cm (1 in) of water.
Tararache Nicola
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