SCIENCE IN THE NEWS - Snow

（单词翻译）

SCIENCE IN THE NEWS - December 10, 2002: Snow

By George Grow

VOICE ONE:
This is Steve Ember.
VOICE TWO:

And this is Bob Doughty¹ with SCIENCE IN THE NEWS, a VOA Special English
program about recent developments in science. Today, we tell you everything you
ever wanted to know about snow.

(THEME)

VOICE ONE: United States

Winter weather is returning to northern areas of the world. In much of the United States, winter means the return
of snow. Snow is a subject of great interest to weather experts. Experts sometimes have difficulty estimating²
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.

VOICE TWO:

Snow is a form of frozen³ water. It contains many groups of tiny ice particles⁴ called
snow crystals⁶. These crystals grow from water particles in cold clouds. They usually
grow around a piece of dust. 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 --platelike and columnar⁷. Platelike
crystals are flat. They form when the air temperature is about fifteen degrees below
zero Celsius⁸. Columnar snow crystals look like sticks of ice. They form when the

temperature is about five degrees below zero Celsius.

VOICE ONE:

The shape of a snow crystal⁵ may change from one form to another as the crystal passes through levels of air with
different temperatures. When melting snow crystals or raindrops fall through very cold air, they freeze to form
small particles of ice, called sleet⁹.

Groups of frozen water droplets¹⁰ are called snow pellets. Under some conditions, these particles may grow larger
and form solid pieces of ice, or hail¹¹.

South Africa
(MUSIC BRIDGE)

VOICE TWO:

When snow crystals stick together, they produce snowflakes. Snowflakes come in
different sizes. As many as one-hundred crystals may join together to form a
snowflake larger than two-and-one-half centimeters. Under some conditions, Russia
snowflakes can form that are five centimeters long. Usually, this requires near (Photo - E. Conan)
freezing temperatures, light winds and changing conditions in Earth’s atmosphere.

Snow contains much less water than rain. About fifteen centimeters of wet snow has as much water as two-andone-half centimeters of rain. About seventy-six centimeters of dry snow equals the water in two-and-one-half


centimeters of rain.

VOICE ONE:

Much of the water we use comes from snow. Melting snow provides water for rivers, electric power centers and
agricultural crops. In the western United States, mountain snow provides up to seventy-five percent of all surface
water supplies.

Snowfall helps to protect plants and some wild animals from cold, winter weather. Fresh snow is made largely¹² of
air trapped among the snow crystals. Because the air has trouble moving, the movement of heat is greatly
reduced.

Snow also is known to influence the movement of sound waves. When there is fresh snow on the ground, the
surface of the snow takes in, or absorbs, sound waves. However, snow can become hard and flat as it becomes
older or if there have been strong winds. Then the snow’s surface will help to send back sound waves. Under
these conditions, sounds may seem clearer and travel farther¹³.

VOICE TWO:

Generally, the color of snow and ice appears white. This is because the light we see from the sun is white. Most
natural materials take in some sunlight. This gives them their color. However, when light travels from air to
snow, some light is sent back, or reflected. Snow crystals have many surfaces to reflect sunlight. Yet the snow
does take in a little sunlight. It is this light that gives snow its white appearance.

Sometimes, snow or ice may appear to be blue. The blue light is the product of a long travel path through the
snow or ice. In simple terms, think of snow or ice as a filter¹⁴. A filter is designed to reject some substances, while
permitting others to pass through. In the case of snow, all the light makes it through if the snow is only a
centimeter thick. If it is a meter or more thick, however, blue light often can be seen.

(MUSIC BRIDGE)

VOICE ONE:

Snow falls in extreme northern and southern areas of the world throughout the year.
However, the heaviest snowfalls have been reported in the mountains of other areas
during winter. These areas include the Alps in Italy and Switzerland, the coastal¹⁵
mountains of western Canada, and the Sierra Nevada and Rocky mountains in the
United States. In warmer climates, snow is known to fall in areas over four-
thousand-nine-hundred meters above sea level.

VOICE TWO:

Each year, the continental¹⁶ United States has an average of one-hundred snow
storms. An average storm produces snow for two to five days. Almost every part of
the country has received snowfall at one time or another. Even parts of southern
Florida have reported a few snowflakes.

The national record for snowfall in a single season was set in nineteen-seventy-one and nineteen-seventy-two.
Two-thousand-eight-hundred-fifty centimeters of snow fell at Ranier Paradise¹⁷ Ranger¹⁸ Station in the northwestern
state of Washington.

VOICE ONE:

People in many other areas have little or no snowfall. In nineteen-thirty-six, a physicist¹⁹ from Japan produced the
first man-made snow in a laboratory²⁰. During the nineteen-forties, several American scientists developed methods
for making snow in other areas. Clouds with extremely cool water are mixed with man-made ice crystals, such as
silver iodide and metaldehyde crystals. Sometimes, dry ice particles or liquid propane are used. Today, special
machines are used to produce limited amounts of snow for winter holiday ski areas.

(MUSIC BRIDGE)

Alps
(Photo - Steve Ember)

VOICE TWO:

Snow is responsible for the deaths of hundreds of people in the United States every year. Many people die in
traffic accidents on roads that are covered with snow or ice. Others die from being out in the cold or from heart
attacks caused by extreme physical activity.

A few years ago, a major storm caused serious problems in the eastern United States. It struck the Southeast in
January, ninety-ninety-six, before moving up the East Coast. The storm was blamed for more than one-hundred
deaths. It forced nine states to declare emergency measures.

Virginia and West Virginia were hit hardest. In some areas there, snowfall amounts were more than one-meter
high. Several states limited driving to emergency vehicles. Most major airports were closed for at least a day or
two.

A week later, two other storms brought additional²¹ snow to the East Coast. In the New York City area, the added
weight of the snow forced the tops of some buildings to break down. Many travelers were forced to walk long
distances through deep snow to get to train stations.

VOICE ONE:

People may not be able to avoid living in areas where it snows often. However, they can avoid becoming victims
of winter snowstorms²³.

People should stay in their homes until the storm has passed. While removing large amounts of snow, they should
stop and rest often. Difficult physical activity during snow removal²⁴ can cause a heart attack. It is always a good
idea to keep a lot of necessary supplies in the home even before winter begins. These supplies include food,
medicine, clean water, and extra power supplies.

VOICE TWO:

Some drivers have become trapped in their vehicles during a snowstorm²². If this happens, people should remain in
or near their car unless they see some kind of help. They should get out and clear space around the vehicle to
prevent the possibility of carbon monoxide gas poisoning.

People should tie a bright-colored object to the top of their car to increase the chance of rescue. Inside the car,
they should open a window a little for fresh air and turn on the engine for ten or fifteen minutes every hour for
heat.

People living in areas where winter storms are likely should carry emergency supplies in their vehicle. These
include food, emergency medical supplies, and extra clothing to stay warm and dry. People in these areas should
always be prepared for winter emergencies. Snow can be beautiful to look at, but it can also be dangerous.

(THEME)

VOICE ONE:

This SCIENCE IN THE NEWS program was written and produced by Cynthia Kirk. This is Steve Ember.

VOICE TWO:

And this is Bob Doughty. Join us again next week for more news about science in Special English on the Voice
of America.

Email this article to a friend
Printer Friendly Version