Let It Snow!
10 January 2011
Winter storms mean shoveling snow in Brunswick, Maine
FAITH LAPIDUS: This is SCIENCE IN THE NEWS, in VOA Special English. I’m Faith Lapidus.
BOB DOUGHTY: And I’m Bob Doughty. Today, we will tell you everything you wanted to know about snow.
(MUSIC)
FAITH LAPIDUS: Winter has returned to northern parts of the world. In the northern United States, winter can mean the return of snow. Large amounts of snow fell in some American cities last month. One storm hit the East Coast, causing flight cancellations and temporarily stopping traffic in some areas.
Snow is a subject of great interest to weather experts. They sometimes have difficulty estimating where, when or how much snow will fall. One reason is that heavy amounts of snow fall in surprisingly small areas. Another reason is that a small change in temperature can mean the difference between snow and rain.
BOB DOUGHTY: Just what is snow, anyway? Snow is a form of frozen water. It contains groups of ice particles called snow crystals. These crystals grow from water droplets in cold clouds. They usually grow around dust particles.
All snow crystals have six sides, but they grow in different shapes. The shape depends mainly on the temperature and water levels in the air.
Snow crystals grow in one of two designs – plate-like and columnar. Plate-like crystals are flat. They form when the air temperature is about fifteen degrees below zero Celsius. Columnar snow crystals look like sticks of ice. They form when the temperature is about five degrees below zero.
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