FUNCTION OF SNOW

Otago Daily Times, Issue 23500, 14 May 1938, Page 28

FUNCTION OF SNOW

FORMS A BLANKET Did you ever wonder if a snow blanket keeps the ground warm? A thick covering of snow on the ground performs two offices quite effectively: It keeps the surface air cold, and at the same time it keeps the ground warm. Glistening white snow reflects, or sends back, nearly three-fourths of the sunlight, instead of absorbing it. as bare earth would. This greatly reduces the amount of heat received from Old Sol, and the snow surface becomes very cold through the loss of heal by radiation and evaporation. On the other hand, a snow blanket is a reliable insulator against heat. "Dead air" —that is. air not free to move about —is a good heat insulator. Freshly-fallen snow is made up of air and ice crystals, with 10 or more times as much air as ice. This imprisoned air. plus the fact that ice is itself a non-conductor of heat, makes snow a very effective blanket for preserving the earth’s warmth. Temperatures taken during an extremely cold spell when there was over a fool of snow' on the ground are illuminating: The thermometer at eye-level read eight degrees below' zero, Fahrenheit; but at the surface of the snow the temperature dropped to 16 below! Another reading taken halfway through the snow blanket showed a temperature of 10 degrees above zero—while the temperature at the ground's surface was nearly up to the melting point.