VOA慢速英语2010年-SCIENCE IN THE NEWS - 'Tornado Season'

BARBARA KLEIN: This is SCIENCE IN THE NEWS in VOA Special English. I'm Barbara Klein.

BOB DOUGHTY¹: And I'm Bob Doughty. This week, we will tell about the science of tornadoes³. Tornadoes have been observed in many parts of the world. But the storms are most often found in the United States.

(MUSIC)

BARBARA KLEIN: Tornado² season has begun in the United States. More than sixty tornadoes were reported in the country's southeast during the last weekend in April. One tornado measuring more than a kilometer wide struck the state of Mississippi. It destroyed homes, blocked roads and cut off electricity.

The storms were blamed for ten deaths in Mississippi, and two others in nearby Alabama. Weather experts believe it was the most intense⁵ tornado event since two thousand eight.

BOB DOUGHTY: A tornado is a violently turning tube of air suspended⁶ from a thick cloud. It extends⁸ from a thunderstorm in the sky down to the ground. The shape is like a funnel⁹: wide at the top, narrower at the bottom.

Ronnie Lindsey sits where his house once stood in Scotland¹⁰, Arkansas. A tornado destroyed his home on May 1.

Tornadoes form when winds blowing in different directions meet in the clouds and begin to turn in circles. Warm air rising from below causes the wind tube to reach toward¹¹ the ground. Because of their circular¹² movement, these windstorms are also known as twisters.

The most severe tornadoes can reach wind speeds of three hundred twenty kilometers an hour or more. In some cases, the resulting paths of damage can stretch more than a kilometer wide and eighty kilometers long.

BARBARA KLEIN: With a tornado, bigger does not necessarily¹³ mean stronger. Large tornadoes can be weak. And some of the smallest tornadoes can be the most damaging. But no matter what the size, tornado winds are the strongest on Earth. Tornadoes have been known to carry homes, cars and trees from one place to another. They can also destroy anything in their path.

Tornadoes have been observed on every continent except Antarctica. But experts say they are most commonly seen in the United States. On average, eight hundred tornadoes are reported nationwide each year.

The National Oceanic and Atmospheric¹⁴ Administration¹⁵ keeps records of tornado sightings. It says tornadoes kill eighty people and injure one thousand five hundred others nationwide in an average year.

(MUSIC)

BOB DOUGHTY: Tornadoes are observed most often in the central part of the United States, where the land is mostly flat. The area where the most violent tornadoes usually happen is known as “Tornado Alley¹⁶.” This area is considered to extend⁷ from north-central Texas to North Dakota.

Tornadoes can happen any time of the year. But most happen from late winter to the middle of summer. In some areas, there is a second high season in autumn.

BARBARA KLEIN: Tornado seasons are the result of wind and weather patterns. During spring, warm air moves north and mixes with cold air remaining from winter. In autumn, the opposite happens. Cold weather moves south and combines with the last of the warm air from summer.

Tornadoes can strike with little or no warning. Most injuries happen when flying objects hit people. Experts say the best place to be is in an underground shelter, or a small, windowless room in the lowest part of a building.

People driving during a tornado are told to find low ground and lay flat, facedown, with their hands covering their head. People in the path of a tornado often have just minutes to make life-or-death decisions.

BOB DOUGHTY: The deadliest American tornado on record is the Tri-State Tornado of March eighteenth, nineteen twenty-five. It tore across Missouri, Illinois and Indiana. About seven hundred people were killed.

A "tornado outbreak" is often defined¹⁷ as six or more tornadoes produced by the same weather system within a day. But the outbreak of April third and fourth, nineteen seventy-four, set a national record. It is remembered as the "Super Outbreak." One hundred forty-eight tornadoes struck during a twenty-four-hour period. More than three hundred people were killed and nearly six thousand others injured.

One tornado that was especially destructive¹⁸ hit Xenia, Ohio. The sound you are about to hear comes from the Web site www.xeniatornado.com. It is one man's recording¹⁹ of the tornado moving closer.

(SOUND)

BARBARA KLEIN: No two tornadoes look exactly the same. And no two tornadoes act the same way.

It takes the right combination²⁰ of wind, temperature, pressure and humidity²¹ to create even a weak tornado. Weather experts can identify these conditions. And, when they observe them, they can advise people that tornadoes might develop. But they are not able to tell exactly where or when a tornado will hit. Tornado warnings still depend in large part on human observations.

Usually a community will receive a warning at least a few minutes before a tornado strikes. But each year there are some surprises where tornadoes develop when they are least expected.

BOB DOUGHTY: The tornado reporting system involves watches and warnings. A tornado watch means tornadoes are possible in the area. A tornado warning means that a tornado has been seen. People are told to take shelter immediately.

Yet tornadoes can be difficult to see. Sometimes only the objects they are carrying through the air can be seen. Some night-time tornadoes have been observed because of lightning strikes nearby. But tornadoes at night are usually impossible to see.

Tornadoes that form over water are called waterspouts. But tornadoes cover a much smaller area than hurricanes, which form over oceans.

Tornadoes can be measured using wind speed information from Doppler radar²² systems. Tornadoes usually travel in a northeasterly direction with a speed of thirty-two to sixty-four kilometers an hour. But they have been reported to move in other directions and as fast as one hundred seventeen kilometers an hour.

BARBARA KLEIN: In the United States, the force of a tornado is judged by the damage to structures. Scientists inspect the damage before they estimate²³ the severity of a tornado. They measure tornadoes on the Fujita scale. Ted⁴ Fujita was a weather expert who developed this system in the nineteen seventies.

There are six levels on the Fujita scale. Tornadoes that cause only light damage are called an F-zero. Those with the highest winds that destroy well-built homes and throw vehicles more than one hundred meters are called an F-five.

(MUSIC)

BOB DOUGHTY: Some people make a sport out of watching and following tornadoes. They are called tornado chasers or storm chasers. Their work can be seen in the extreme weather videos that are increasingly²⁴ popular on television and on the Internet.

Some chasers do it just because it is their idea of fun. Others do it to help document storms and warn the public. Still others are part of weather research teams.

This month, more than one hundred researchers began deploying²⁵ radar and other scientific instruments across America’s Great Plains. They are hoping to surround tornadoes in the second and final year of an international project known as VORTEX2. The goal of the project is to examine in detail how tornadoes are formed and the kinds of damage they cause.

Last year, the project collected information about a tornado in southeastern Wyoming. Researchers also observed several other powerful storms that were not tornadoes.

BARBARA KLEIN: The National Weather Service says the United States gets more severe weather than any other country. For one thing, it is also bigger than most other countries. And it has many different conditions that create many different kinds of weather.

There are seacoasts and deserts, flatlands and mountains. The West Coast is along the Pacific Ocean, which is relatively²⁶ calm. The East Coast is along the Atlantic Ocean, which is known for its hurricanes. These strike mainly the southeastern states.

(MUSIC)

BOB DOUGHTY: This SCIENCE IN THE NEWS was written by Brianna Blake, who was also our producer. I'm Bob Doughty.

BARBARA KLEIN: And I'm Barbara Klein. Read and listen to our programs at voaspecialenglish.com. And if you have a science question, send it to [email protected]. We might answer it on our program. 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 tornado   

n.飓风，龙卷风

参考例句：

• A tornado whirled into the town last week.龙卷风上周袭击了这座城市。
• The approaching tornado struck awe in our hearts.正在逼近的龙卷风使我们惊恐万分。

3 tornadoes   

n.龙卷风，旋风( tornado的名词复数 )

参考例句：

• Tornadoes, severe earthquakes, and plagues create wide spread havoc. 龙卷风、大地震和瘟疫成普遍的毁坏。 来自互联网
• Meteorologists are at odds over the working of tornadoes. 气象学者对龙卷风的运动方式看法不一。 来自互联网

4 ted   

vt.翻晒，撒，撒开

参考例句：

• The invaders gut ted the village.侵略者把村中财物洗劫一空。
• She often teds the corn when it's sunny.天好的时候她就翻晒玉米。

5 intense   

adj.认真的，专注的；强烈的；紧张的；热情的

参考例句：

• Susan was an intense young lady.苏珊是一个热情的年轻姑娘。
• The quarrel caused her intense unhappiness.争吵令她极其不快。

6 suspended   

a.被暂时搁置的

参考例句：

• A lamp was suspended from the ceiling. 一盏吊灯悬在天花板上。
• The British government has now suspended humanitarian aid to the area. 英国政府现已暂停对这一地区的人道主义援助。

7 extend   

v.伸开；展开，伸展；扩大；加大

参考例句：

• Can you extend your visit for a few days more?你能把你的访问再延长几天吗？
• The examinations extend over two weeks.考试持续两个星期。

8 extends   

v.（空间、时间等）延伸，延续( extend的第三人称单数 )；伸展；给予；延长

参考例句：

• This country extends its power and influence into neighbouring countries. 这个国家将其势力与影响扩大至邻国。 来自《简明英汉词典》
• His domain extends for 20 miles in every direction. 方圆20英里之内都是他的地产。 来自《简明英汉词典》

9 funnel   

n.漏斗；烟囱；v.汇集

参考例句：

• He poured the petrol into the car through a funnel.他用一个漏斗把汽油灌入汽车。
• I like the ship with a yellow funnel.我喜欢那条有黄烟囱的船。

10 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。

11 toward   

prep.对于，关于，接近，将近，向，朝

参考例句：

• Suddenly I saw a tall figure approaching toward the policeman.突然间我看到一个高大的身影朝警察靠近。
• Upon seeing her,I smiled and ran toward her. 看到她我笑了，并跑了过去。

12 circular   

adj.圆(形)的，环形的；循环的；n.传单，通报

参考例句：

• The bright boy altered it to a circular form.这个聪明的男孩把它改成了圆形。
• The lamp stands on a circular base.这盏台灯是装在圆形底座上的。

13 necessarily   

adv.必要地，必需地；必定地，必然地

参考例句：

• More work does not necessarily call for more men.增加工作量不一定就要增添人员。
• A voter must necessarily be no younger than eighteen.选民必须在18岁以上。

14 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。

15 administration   

n.经营，管理；行政，行政机关，管理部门

参考例句：

• Who is in charge of the administration of your company?你们公司的行政工作由谁负责？
• The teachers are responsible to the school administration.教师向学校行政负责。

16 alley   

n.小巷，胡同；小径，小路

参考例句：

• We live in the same alley.我们住在同一条小巷里。
• The blind alley ended in a brick wall.这条死胡同的尽头是砖墙。

17 defined   

adj 定义的; 清晰的

参考例句：

• These categories are not well defined. 这些类别划分得不太明确。
• The powers of a judge are defined by law. 法官的权限是由法律规定的。

18 destructive   

adj.破坏（性）的，毁灭（性）的

参考例句：

• In the end,it will be destructive of our whole society.它最终会毁灭我们整个社会。
• It is the most destructive storm in 20 years.这是20年来破坏性最大的一次风暴。

19 recording   

n.录音，记录

参考例句：

• How long will the recording of the song take?录下这首歌得花多少时间？
• I want to play you a recording of the rehearsal.我想给你放一下彩排的录像。

20 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。

21 humidity   

n.湿度，潮湿，湿气

参考例句：

• The house is not comfortable tonight ,because of the high humidity.由于湿度高，今晚屋子里不舒服。
• It's difficult to work because of the humidity.由于空气潮湿，工作很困难。

22 radar   

n.雷达，无线电探测器

参考例句：

• They are following the flight of an aircraft by radar.他们正在用雷达追踪一架飞机的飞行。
• Enemy ships were detected on the radar.敌舰的影像已显现在雷达上。

23 estimate   

n.估计，估量；评价，看法；vt.估计，估量

参考例句：

• We estimate the cost to be five thousand dollars.我们估计费用为5000美元。
• The lowest estimate would put the worth of the jewel at ＄200.按最低的评估这块宝石也值200美元。

24 increasingly   

adv.逐渐地，日益地，逐渐增加地

参考例句：

• Rivers are being increasingly made use of by man. 河流正在日益为人类所利用。
• I find it increasingly difficult to live within my income.我发现靠收入过日子越来越难了。

25 deploying   

（尤指军事行动）使展开( deploy的现在分词 )； 施展； 部署； 有效地利用

参考例句：

• Provides support for developing and deploying distributed, component-based applications. 为开发和部署基于组件的分布式应用程序提供支持。
• Advertisement, publishing, repair, and install-on-demand are all available when deploying your application. 在部署应用程序时提供公布、发布、修复和即需即装功能。

26 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。