The chemistry of a resource that provides much of the water we use

VOICE ONE:

声音1：

This is SCIENCE IN THE NEWS in VOA Special English. I'm Steve Ember.

这是voa英语的科技新闻专刊。我是Steve Ember。

VOICE TWO:

声音2：

And I'm Barbara Klein. Today, we tell you everything you ever wanted to know about snow.

我是Barbara Klein。今天，我们来讲一些关于雪的事情。

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VOICE ONE: 

声音1：

		Digging out from a blizzard

Winter weather has returned to northern areas of the world.

北方的冬天又到来了。

In much of the United States, winter means the return of snow.

在美国的许多地方，冬天就意味这下雪。

Snow is a subject of great interest to weather experts.

下雪是一个气象专家很感兴趣的话题。

 Experts sometimes have difficulty estimating where,

专家有时候很难估计，在哪里，什么时候会下多少雪。

when or how much snow will fall.

One reason is that heavy amounts of snow fall in surprisingly small areas.

原因就是下雪的总量的大部分总是出人意料的集中在某个小的地区。

Another reason is that a small change in temperature can mean the difference between snow and rain.

另一个重要的原因就是一个很小的温度变化就会导致下雪变成下雨。

VOICE TWO:

声音2：

Snow is a form of frozen water. It contains many groups of tiny ice particles （颗粒）called snow crystals.

雪就是冻结了的水。它包含了许多微小的冰颗粒，这些冰颗粒叫做雪晶。

These crystals grow from water particles in cold clouds. They usually grow around a piece of dust.

温度很低的云中的水形成了这些晶体。他们逐渐会因为覆盖一层层的尘埃长大。

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.

所有的雪晶都有六个边，但是他们会长成不同的形状。形状主要是由温度和空气中的水量决定的。

Snow crystals grow in one of two designs -- platelike and columnar.

雪晶会成长为片状或是圆柱状的一种。

 

Platelike crystals are flat. They form when the air temperature is about fifteen degrees below zero Celsius（摄氏的）.

片状的雪晶是扁平的。当温度低于零下15摄氏度。

Columnar snow crystals look like sticks of ice. They form when the temperature is about five degrees below zero.

柱状的雪晶看起来就像是一个小冰棒。当气温在零下5度他们会形成。

VOICE ONE:

声音1：

The shape of a snow crystal may change from one form to another as the crystal passes through levels of air with different temperatures.

当他们通过不同温度的大气时，雪晶的形状会从一种形状变为另一种形状。

When melting snow crystals or raindrops fall through very cold air, they freeze to form small particles of ice, called sleet.

当融化的雪晶或雨滴穿过非常冷的空气时，他们会结晶成很小的冰颗粒，叫做雨凇。

 

Groups of frozen water droplets（小滴） are called snow pellets（圆球,小子弹,小药丸）. Under some conditions, these particles may grow larger and form solid pieces of ice, or hail.

大量冻结的小水滴叫做雪球丸。在某些情况下，这些微粒会长大成固体冰片或冰雹。

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VOICE TWO:

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When snow crystals stick together, they produce snowflakes. Snowflakes come in different sizes.

当雪晶粘在一起时，他们会形成雪花。雪花会有不同的大小。

 As many as one hundred crystals may join together to form a snowflake larger than two and one-half centimeters.

一百个雪晶结合在一起形成的雪花会有2.5厘米那么大。

Under some conditions, snowflakes can form that are five centimeters long. Usually, this requires near freezing temperatures, light winds and changing conditions in Earth's atmosphere.

在某些条件下，雪花会形成5厘米长。通常，这需要大气层有极冷的温度，微风和变化的条件。

 

Snow contains much less water than rain. About fifteen centimeters of wet snow has as much water as two and one-half centimeters of rain.

下雪所含的水远远少于下雨。15厘米的降雪量就相当于2.5厘米的降雨量。

About seventy-six centimeters of dry snow equals the water in two and one-half centimeters of rain.

76厘米的干雪就相当于2.5厘米的雨水。

 

VOICE ONE:

声音1：

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.

我们用的许多水都来自雪。融化的雪给河流、发电站、和农业提供了水。在美国西部地区，冰山融雪给提供了百分之七十五的水资源。

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

降雪有助于保护植物和野生动物抵御冬天的冷。新鲜的雪是由空气中的大量雪晶构成的。因为空气的运动，若运动被大量的减少。

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 farther.

雪化对传播中的声音也有影响。当有一片雪花落到地面时，雪的表面就会发出声音，或绝对的说是声波。然而，下雪会带来一些不便尤其是在化雪的时候，或者还有大风。雪花的表面会加强声波的反射。在这些情况下，声音会听的更清，传的更远。

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 filter. 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.

有时候，

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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 coastal 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 continental United States has an average of one hundred snowstorms. 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 ninety-eight and nineteen ninety-nine. Two thousand eight hundred ninety-five centimeters of snow fell at the Mount Baker Ski area in the northwestern state of Washington.

VOICE ONE:

People in many other areas have little or no snowfall. In nineteen thirty-six, a physicist from Japan produced the first man-made snow in a laboratory. 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.

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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.

Several 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 additional 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 snowstorms.

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 removal 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 snowstorm. 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.

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VOICE ONE:

This SCIENCE IN THE NEWS program was written by George Grow. Our producer was Brianna Blake. I'm Steve Ember.

科技之音节目由George Grow编写。制作人Brianna Blake。我是Steve Ember。

VOICE TWO:

And I'm Barbara Klein. Join us again next week for more news about science in Special English on the Voice of America.

 我是Barbara Klein。下星期加入我们特别英语美国之音会有更多的科技新闻。