VOA慢速英语2011-SCIENCE IN THE NEWS - Let It Snow!

FAITH LAPIDUS: This is SCIENCE IN THE NEWS, in VOA Special English. I’m Faith Lapidus.

BOB DOUGHTY¹: And I’m Bob Doughty. Today, we will tell you everything you wanted to know about snow.

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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 estimating³ 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 frozen⁴ water. It contains groups of ice particles⁵ called snow crystals⁷. These crystals grow from water droplets⁸ 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.

Winter storms mean shoveling snow in Brunswick, Maine

Snow crystals grow in one of two designs – plate-like and columnar⁹. Plate-like crystals are flat. They form when the air temperature is about fifteen degrees below zero Celsius¹⁰. Columnar snow crystals look like sticks of ice. They form when the temperature is about five degrees below zero.

FAITH LAPIDUS: The shape of a snow crystal⁶ 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 sleet¹¹. Groups of frozen water-droplets are called snow pellets. Under some conditions, these particles may grow larger and form solid pieces of ice, or hail¹². Hail can be dangerous to people, animals and property.

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BOB DOUGHTY: When snow crystals stick together, they produce snowflakes. Snowflakes come in different sizes. As many as one hundred crystals may join to form a snowflake larger than two and one-half centimeters. 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.

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

FAITH LAPIDUS: Much of the water the world uses comes from snow. Melting snow provides water for rivers, electric power stations and agricultural crops. Mountain snow provides up to seventy-five percent of all surface water supplies in the western United States.

A snow covered forest

Snowfall helps to protect plants and some wild animals from winter weather. Fresh snow is made largely¹³ of air trapped among the snow crystals. Because the air has trouble moving, the movement of heat is limited.

Snow also influences 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 grows 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 may travel farther¹⁴.

BOB DOUGHTY: Generally, snow and ice appear 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 path through the snow or ice. Think of snow or ice as a filter¹⁵. A filter is designed to reject some substances, while permitting others to pass through. In the case of snow, 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.

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FAITH LAPIDUS: Snow falls in the Earth’s extreme North and South 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 coastal¹⁶ mountains of western Canada, and the Sierra Nevada and Rocky Mountains in the United States. Snow is even known to fall near the Equator¹⁷, but only on the highest mountains.

BOB DOUGHTY: Sometimes, snow comes earlier than normal. And sometimes it falls in areas that are not known for having snow. In early December, ice and heavy snow caused officials in Paris to close its main airport and the Eiffel Tower. It was the heaviest snowfall in the French capital has received in years.

Snow also fell in other parts of Europe. Scotland¹⁸ received its heaviest snowfall since nineteen sixty-three. A combination¹⁹ of snow, rain and freezing conditions caused traffic problems in Germany. There were hundreds of accidents nationwide. Hundreds of flights were cancelled, most of them at the Frankfurt airport.

FAITH LAPIDUS: Each year, the continental²⁰ United States has an average of one hundred five snowstorms²². An average storm produces snow for two to five days.

Almost every part of the United States has received snowfall at one time or another. Even parts of southern Florida, where many Americans go for warm-weather vacations, have reported a few snowflakes.

The national record for snowfall in a single season was set in the winter of nineteen ninety-eight to nineteen ninety-nine. Two thousand eight hundred ninety-five centimeters of snow fell at the Mount² Baker²³ Ski area in the northwestern state of Washington.

BOB DOUGHTY: People in many areas have little or no snowfall. In 1936, a physicist²⁴ from Japan produced the first man-made snow in a laboratory²⁵. Then, during the 1940s, 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, machines are used to produce limited amounts of snow for winter ski areas when not enough natural snow has fallen.

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FAITH LAPIDUS: Snow may be beautiful, but it can be deadly. It 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 too much physical activity.

You may not be able to avoid living in areas where it snows often. However, you can avoid becoming a victim of snowstorms. Most people are told to stay in their homes until the storm has passed. When removing large amounts of snow, they should stop and rest often. Difficult physical activity during snow removal²⁶ can cause a heart attack, especially among the elderly.

It is always a good idea to keep a lot of supplies in the home, even before winter begins. These supplies include food, medicine, clean water and extra power supplies.

BOB DOUGHTY: Drivers have become trapped in their vehicles during a snowstorm²¹. 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’s exhaust²⁷ pipe to prevent the possibility of carbon monoxide poisoning.

Drivers 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, but it can also be dangerous.

(MUSIC)

FAITH LAPIDUS: This SCIENCE IN THE NEWS was written by Christopher Cruise²⁸. June Simms was our producer. I’m Faith Lapidus.

BOB DOUGHTY: And I’m Bob Doughty. Read and listen to our programs at voaspecialenglish.com. Join us again next week for more news about science in Special English on the Voice of America.

1 doughty   

adj.勇猛的，坚强的

参考例句：

• Most of successful men have the characteristics of contumacy and doughty.绝大多数成功人士都有共同的特质：脾气倔强，性格刚强。
• The doughty old man battled his illness with fierce determination.坚强的老人用巨大毅力与疾病作斗争。

2 mount   

n.山峰，乘用马，框，衬纸；vi.增长，骑上（马）；vt.提升，爬上，装备

参考例句：

• Their debts continued to mount up.他们的债务不断增加。
• She is the first woman who steps on the top of Mount Jolmo Lungma.她是第一个登上珠穆朗玛峰的女人。

3 estimating   

n.估计v.估计，评价，评估( estimate的现在分词 )；（粗略）估计（…的距离、价值、数目、大小、重量、费用等），估量，预算

参考例句：

• We use nonparametric tests, we lose sharpness in estimating intervals. 使用非常数检验我们失掉了估计区间的灵敏性。 来自辞典例句
• CA986 from San Francisco is estimating in at 22:25. 从旧金山飞来的CA986航班估计22点25分到达。 来自辞典例句

4 frozen   

adj.冻结的，冰冻的

参考例句：

• He was frozen to death on a snowing night.在一个风雪的晚上，他被冻死了。
• The weather is cold and the ground is frozen.天寒地冻。

5 particles   

微粒( particle的名词复数 )； 颗粒； 极少量； 小品词

参考例句：

• These small particles agglomerate together to form larger clusters. 这些颗粒聚结形成较大的团。
• The nucleus of an atom consists of neutrons, protons and other particles. 原子核由中子、质子和其他粒子构成。

6 crystal   

n.水晶，水晶饰品，结晶体；最好的玻璃器皿

参考例句：

• It used to be a crystal stream.那曾是条清澈见底的小溪。
• Those fine wine glasses are made of crystal.那些漂亮的酒杯是用水晶做的。

7 crystals   

n.水晶( crystal的名词复数 )；结晶（体）

参考例句：

• It is snow and ice crystals. 这是雪和冰的结晶体。 来自《简明英汉词典》
• Snowflakes are loose aggregates of ice crystals. 雪花是冰晶的松散凝结。 来自《简明英汉词典》

8 droplets   

n.小滴( droplet的名词复数 )

参考例句：

• Droplets of sweat were welling up on his forehead. 他额头上冒出了滴滴汗珠。 来自辞典例句
• In constrast, exhaled smoke contains relatively large water droplets and appears white. 相反，从人嘴里呼出的烟则包含相当大的水滴，所以呈白色。 来自辞典例句

9 columnar   

adj.柱形的，筒形的，分纵栏印刷或书写的

参考例句：

• Snow crystals grow in one of two designs—platelike and columnar. 雪晶是按照两种形状中的一种——板状和圆柱形形成的。 来自辞典例句
• Simple columnar epithelium consists of tall, narrow cells having considerably greater height than width. 单层柱状上皮由高桂状上皮细胞组成，细胞的高度显著大于细胞的宽度。 来自辞典例句

10 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

11 sleet   

n.雨雪；v.下雨雪，下冰雹

参考例句：

• There was a great deal of sleet last night.昨夜雨夹雪下得真大。
• When winter comes,we get sleet and frost.冬天来到时我们这儿会有雨夹雪和霜冻。

12 hail   

n.雹，一阵；vi.下雹；vt.高呼，为...喝彩

参考例句：

• Hail fell with such violence that it broke windows.冰雹猛落，把玻璃窗也砸破了。
• The people lined the streets to hail the returning heroes.人们夹道欢迎凯旋的英雄们。

13 largely   

adv.大部分，主要地

参考例句：

• It is largely dependent on the weather.这多半取决于天气情况。
• Their conclusions were largely founded on guesswork.他们的结论大部份基于猜测。

14 farther   

adj.更远的，进一步的；adv.更远的，此外；far的比较级

参考例句：

• I can throw the ball farther than you can.这个球我能比你扔得远。
• The farther hill is five kilometres away.那座更远的小山在五公里以外。

15 filter   

n.滤器，过滤嘴；v.过滤，透过

参考例句：

• Foreign influence began to filter into the country.外国势力开始渗透进这个国家。
• Charcoal is used to filter water.木炭是用来过滤水的。

16 coastal   

adj.海岸的，沿海的，沿岸的

参考例句：

• The ocean waves are slowly eating away the coastal rocks.大海的波浪慢慢地侵蚀着岸边的岩石。
• This country will fortify the coastal areas.该国将加强沿海地区的防御。

17 equator   

n.赤道，（平分球形物体的面的）圆

参考例句：

• Singapore is near the equator.新加坡位于赤道附近。
• The United States is north of the equator.美国位于赤道以北。

18 Scotland   

n.苏格兰

参考例句：

• He has been hiking round Scotland for a month.他围着苏格兰徒步旅行了一个月。
• Scotland is to the north of England.苏格兰在英格兰之北。

19 combination   

n.组合，合并，联合；

参考例句：

• He carried on the business in combination with his friends.他与朋友们合伙做生意。
• The materials can be used singly or in combination.这些材料可以单独使用也可以混合用。

20 continental   

adj.大陆的，大陆性的，欧洲大陆的

参考例句：

• A continental climate is different from an insular one.大陆性气候不同于岛屿气候。
• The most ancient parts of the continental crust are 4000 million years old.大陆地壳最古老的部分有40亿年历史。

21 snowstorm   

n.雪暴，暴风雪

参考例句：

• After several weeks of travel,snowstorm hit us first.我们旅行了几个星期，初次碰上了暴风雪。
• A severe snowstorm blocked up railroads.一场暴风雪使铁路中断。

22 snowstorms   

n.暴风雪，雪崩( snowstorm的名词复数 )

参考例句：

• However, they can avoid becoming victims of winter snowstorms. 但是，他们有能力避免成为冬季暴风雪的牺牲品。 来自互联网
• Snowstorms played hell with the flow of city traffic. 暴风雪严重地影响了市内交通。 来自互联网

23 baker   

n.面包师

参考例句：

• The baker bakes his bread in the bakery.面包师在面包房内烤面包。
• The baker frosted the cake with a mixture of sugar and whites of eggs.面包师在蛋糕上撒了一层白糖和蛋清的混合料。

24 physicist   

n.物理学家，研究物理学的人

参考例句：

• He is a physicist of the first rank.他是一流的物理学家。
• The successful physicist never puts on airs.这位卓有成就的物理学家从不摆架子。

25 laboratory   

n.实验室，化验室

参考例句：

• She has donated money to establish a laboratory.她捐款成立了一个实验室。
• Our laboratory equipment isn't perfect,but we must make do.实验室设备是不够理想，但我们只好因陋就简。

26 removal   

n.去除，消除；挪走，移走，搬迁

参考例句：

• After the removal of the soup,fish was served.汤撤去后，鱼就上来了。
• The factory announced its removal to another town.这家工厂宣布迁往另一座城镇。

27 exhaust   

vt.使衰竭，使筋疲力尽；用尽，耗尽，用完

参考例句：

• The climb will exhaust the boys.爬山会使那些男孩们疲惫不堪的。
• It will exhaust the nation's oil reserves.它会耗尽国家的石油储备。

28 cruise   

v.巡航，航游，缓慢巡行；n.海上航游

参考例句：

• They went on a cruise to Tenerife.他们乘船去特纳利夫岛。
• She wants to cruise the canals of France in a barge.她想乘驳船游览法国的运河。