VOA慢速英语2012 SCIENCE IN THE NEWS - Tornado Season Returns

SCIENCE IN THE NEWS - Tornado¹ Season Returns

 

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

BOB DOUGHTY²: And I'm Bob Doughty. This week, we explore the science of tornadoes³. These violent storms strike in many parts of the world but happen most commonly in the United States.

(MUSIC)

BARBARA KLEIN: Tornado season has begun in the United States.

Last Tuesday a series of storms tore across the Dallas-Fort Worth area in Texas. The tornadoes damaged or destroyed hundreds of homes. Yet no deaths were reported.

On March second, more than forty tornadoes moved through the Ohio and Tennessee Valleys, and the South. Reports say the storms killed at least thirty-nine people in five states.

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.

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 toward¹⁰ the ground. Because of their circular¹¹ 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.

BOB DOUGHTY: With a tornado, bigger does not necessarily¹² 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 trees, cars or homes 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, more than one thousand are reported nationwide each year.

The National Oceanic and Atmospheric¹³ Administration¹⁴ keeps records of tornado sightings. It says tornadoes kill seventy people and injure one thousand five hundred others nationwide in an average year.

(MUSIC)

BARBARA KLEIN: Tornadoes are observed most often in the middle of the United States, where the land is mostly flat. The area where the most violent tornadoes usually happen is known as “Tornado Alley⁵.” 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.

BOB DOUGHTY: 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 just have minutes to make life-or-death decisions.

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

Between March and May of last year, there were one thousand one hundred fifty-nine confirmed tornadoes across the United States. Scientists say that is the most on record for any three-month period. The most active month was last April, when seven hundred fifty-eight tornadoes were confirmed. That is the most ever for any month.

Last April, the country also broke a thirty-seven year old record for the largest tornado outbreak. A "tornado outbreak" is often defined¹⁵ as six or more tornadoes produced by the same weather system within a day.

Scientists say the one hundred ninety-nine tornadoes on April twenty-seventh were the most for any single day. They say the storms killed three hundred sixteen people – the most ever in modern records for a twenty-four hour period.

(MUSIC)

BOB DOUGHTY: No two tornadoes look exactly the same. And no two tornadoes act the same way.

Even a weak tornado requires the right combination¹⁶ of wind, temperature, pressure and humidity¹⁷. 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.

BARBARA KLEIN: 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 radar¹⁸ 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.

BOB DOUGHTY: In the United States, the force of a tornado is judged by the damage to structures. Scientists inspect the damage before they estimate¹⁹ the severity of a tornado. They measure tornadoes on the Enhanced²⁰ Fujita scale or the EF scale.

Ted⁴ Fujita was a weather expert who developed a system to rate tornados²¹ in the nineteen seventies. The EF scale is a set, or collection, of wind estimates²². They are based on levels of damage to twenty-eight different kinds of structures and other objects. Tornadoes that cause only light damage are called an EF-zero. Those with the highest winds that destroy well-built homes and throw vehicles great distances are called an EF-five.

(MUSIC)

BARBARA KLEIN: 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 increasingly²³ 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.

Two years ago, an international team of scientists completed a tornado research project called VORTEX2. More than one hundred researchers traveled throughout America’s Great Plains in two thousand nine and two thousand ten. They used weather measurement²⁴ instruments to collect scientific information about the life of a tornado. The goal of the project was to examine in detail how tornadoes are formed and the kinds of damage they cause.

Last year, a film about the VORTEX2 project was released²⁵. The film includes never before seen images of tornadoes. To safely capture²⁶ up-close film footage of tornadoes, some project participants traveled in a seven-ton, armored tornado intercept²⁷ vehicle directly into tornadoes as they formed.

BOB DOUGHTY: 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 relatively²⁸ calm. The East Coast is along the Atlantic Ocean, which is known for its hurricanes. These strike mainly the southeastern states.

(MUSIC)

BARBARA KLEIN: This SCIENCE IN THE NEWS was written by Brianna Blake and George Grow. June Simms was our producer. I'm Barbara Klein.

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

1 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。

2 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。

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 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。

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 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。

11 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。

12 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。

13 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。

14 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。

15 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。

16 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。

17 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。

18 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。

19 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。

20 enhanced   

a.加强的

参考例句：

• Peak updraft strength is slightly enhanced with hodograph curvature. 山顶上升气流强度随速矢端迹曲率加大而稍有加强。
• The black wimple enhanced the whiteness of her skin. 黑色的包头巾使她的皮肤显得更加白皙。

21 tornados   

n.龙卷风，旋风( tornado的名词复数 )

参考例句：

• And the national weather service reports several tornados touch down. 国家气象中心报告预测龙卷风将来袭。 来自互联网
• They had stock footage of lightning, tornados, and hurricanes. 他们存有关于闪电、龙卷风和飓风的电影胶片。 来自互联网

22 estimates   

估计

参考例句：

• Unofficial estimates put the figure at over two million. 非官方的估计数字为200万以上。
• We got estimates from three different contractors before accepting the lowest. 我们得到3个承包商的报价后，接受了最低的报价。 来自《简明英汉词典》

23 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。

24 measurement   

n.测量，衡量；(量得的)尺寸，大小

参考例句：

• I can find the size of something by means of measurement.我可以用测量法求得某物的体积。
• He has made an accurate measurement of my garden.他准确地丈量了我的花园。

25 released   

v.释放( release的过去式和过去分词 )；放开；发布；发行

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• With hindsight it is easy to say they should not have released him. 事后才说他们本不应该释放他，这倒容易。

26 capture   

vt.捕获，俘获；占领，夺得；n.抓住，捕获

参考例句：

• The company is out to capture the European market.这家公司希望占据欧洲市场。
• With the capture of the escaped tiger,everyone felt relieved.逃出来的老虎被捕获后，大家都松了一口气。

27 intercept   

vt.拦截，截住，截击

参考例句：

• His letter was intercepted by the Secret Service.他的信被特工处截获了。
• Gunmen intercepted him on his way to the airport.持枪歹徒在他去机场的路上截击了他。

28 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。