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时间:2006-12-11 16:00:00

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SCIENCE IN THE NEWS - Storm Warnings: Trying to Understand the Causes of HurricanesBy Nancy Steinbach and Caty Weaver1 and produced by Brianna Blake

Broadcast: Tuesday, September 12, 2006

VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty2.

VOICE TWO:


Hurricane Florence is shown in the Atlantic at 20:45 UTC Monday. The hurricane at Category 1 strength cut electric power to thousands of homes and businesses as it passed Bermuda, east of the American state of South Carolina.

And I'm Faith Lapidus. Powerful storms are called hurricanes when they form over the Atlantic Ocean and the eastern Pacific. They are called typhoons in the northwestern Pacific, and cyclones3 when they develop over the Indian Ocean. Whatever we call them, these storms are the subject of our program this week.

(MUSIC)

VOICE ONE:

Severe ocean storms in the northern half of the world generally develop in late summer or early autumn near the equator4.

Storms can result when the air temperature in one area is different from that of another. Warmer air rises and cooler air falls. These movements create a difference in the pressure of the atmosphere.

If the pressure changes over a large area, winds start to blow in a huge circle. High-pressure air is pulled into a low-pressure center.

Severe ocean storms happen less often in the southern hemisphere5. There the season of greatest activity is between December and March.

South of the equator, the winds flow in the same direction as the hands on a clock. North of the equator, they flow counter-clockwise.

This is because as Earth turns, air is pulled to the right in the northern hemisphere. In the southern hemisphere, air is pulled to the left.

VOICE TWO:


Heavy winds in Puerto Vallarta, Mexico

Storms can get stronger and stronger as they move over warm ocean waters. The strongest, fastest winds of a hurricane are found in the eyewall. This is the area that surrounds the center, or eye, of the storm. The eye itself is calm by comparison, with light winds and clear skies.

Winds in severe ocean storms can reach speeds of more than two hundred fifty kilometers an hour. Up to fifty centimeters of rain can fall. Some storms have produced more than one hundred fifty centimeters of rain.

These storms also cause high waves and ocean surges7. A surge6 is a continuous movement of water that may reach six meters or more. The water smashes8 across low coastal9 areas. Surges are commonly responsible for about ninety percent of all deaths from ocean storms.

VOICE ONE:

Weather scientists use computers to create models that show where a storm might go. Models combine information such as temperatures, wind speed, atmospheric10 pressure and the amount of water in the atmosphere.

Scientists collect the information with satellites, weather balloons and devices floating in the world's oceans. They also collect information from ships and passenger flights and from planes that fly into and around storms. The crews drop instruments on parachutes to record temperature, pressure, wind speed and other conditions.

(MUSIC)

VOICE TWO:


Saffir-Simpson Hurricane Scale

The Saffir-Simpson Hurricane Scale is a way to rate storms based on wind speed. It provides an idea of the amount of coastal flooding and property damage that might be expected.

The scale is divided into five categories. A Category One storm has winds of about one hundred twenty to one hundred fifty kilometers an hour. It can damage trees and lightweight structures. It can also cause some flooding.

Wind speeds in a Category Two hurricane can reach close to one hundred eighty kilometers an hour. These storms are often powerful enough to break windows or blow the roof off a house.

Winds between about one hundred eighty and two hundred fifty kilometers an hour represent categories three and four. Anything even more powerful is a Category Five hurricane.

VOICE ONE:

An Australian weather scientist began to call storms by women's names before the end of the nineteenth century. During World War Two, weather scientists called storms by the names of their wives or girlfriends. The weather service in the United States officially started to use women's names for storms in nineteen fifty-three. In nineteen seventy-nine, it began to use men's names, too.

Scientists decide on lists of names years in advance. They agree on them at meetings of the World Meteorological Organization.

VOICE TWO:

Naming storms is part of the job of the National Hurricane Center near Miami, Florida. Storms get a name when they reach a wind speed of sixty-two kilometers an hour, even if they never develop into hurricanes.

The first name used in a storm season begins with the letter A, the second with B and so on. The same list of names is not used again for at least six years. And different lists are used for different parts of the world.

For example, names for storms in the Atlantic this year include Alberto, Debby, Florence, Joyce and Oscar. Storm names for the central North Pacific include Akoni, Hana, Lala and Oka.

VOICE ONE:

Letters of the Greek alphabet had to be used for the first time last year to name storms in the Atlantic. That was the plan -- to call storms Alpha, Beta, Gamma and so on -- if there were ever more than twenty-one named storms in a season. In fact, there were twenty-eight.

The two thousand five Atlantic hurricane season was the first on record with fifteen hurricanes. Four reached Category Five strength, also a first. And the National Oceanic and Atmospheric Administration says it was the first season with four major hurricanes to hit the United States.


Hurricane Katrina

The most destructive11 was Katrina. More than one thousand eight hundred people were killed along the Gulf12 of Mexico coast, most of them in Louisiana.

(MUSIC)

VOICE TWO:

There is debate about the influence of global warming on hurricanes. Scientists have found no simple answers.

A new study has just been published online in the Proceedings13 of the National Academy of Sciences, in the United States. Scientists examined rising ocean temperatures in areas of the Atlantic and Pacific where hurricanes form. They found an eighty-four percent chance that humans have caused most of the observed rise over the last one hundred years. They say warming sea surface temperatures are mainly the result of an increase in greenhouse gases released into the atmosphere.

Earlier research examined temperature changes over very large ocean areas, such as all of the Atlantic or Pacific. The new study involved much smaller hurricane formation areas. The researchers say they used most of the world's computer climate models to study the causes of the temperature changes.

The study involved scientists from ten research centers. These included Lawrence Livermore National Laboratory in California and the National Center for Atmospheric Research in Colorado. Tom Wigley from the Colorado team says: The best explanation for these changes has to include a large human influence.

Hurricanes are highly complex. The researchers say increasing ocean temperatures are not the only cause of hurricane intensity14, but are likely to be one of the major influences.

VOICE ONE:

A year ago, Kerry Emanuel of the Massachusetts Institute of Technology reported an increase in the intensity of hurricanes since the nineteen seventies. He linked it to tropical sea-surface temperatures rising as a result of normal long-term changes and global warming. He said his results suggested that future warming may lead to storms of increasingly destructive power.

But other experts say not all storms get stronger as waters get warmer. Some do, others do not. They say major storms may develop when bodies of water reach about twenty-eight degrees Celsius15. Other conditions, however, must also be present. These include a large amount of water in the air and low wind speed in the upper atmosphere.

VOICE ONE:

Studies have also looked at changes in the number of the most powerful hurricanes each year. Peter Webster and others at the Georgia Institute of Technology reported that the number of intense storms almost doubled in the past thirty-five years.

But some other scientists found different results when they looked at different periods.

One of them was Patrick Michaels of the University of Virginia and the Cato Institute, and currently16 a visiting professor at Virginia Tech. He says the rate of category four and five hurricanes in the Atlantic is the same now as it was in the nineteen forties and fifties. He says this shows that natural forces are at work, not global warming caused by humans.

Frank Lepore is the public affairs officer at the National Hurricane Center. He says disagreements like these show the great difficulty involved in trying to understand what causes hurricanes.

VOICE TWO:

In July, ten scientists released a statement about what they called the main hurricane problem facing the United States. They warned that the problem is development in coastal areas at risk from hurricanes.

They called on government leaders not to support policies that have increased the density17 of population and wealth in these areas. Their message was that building in risky18 coastal areas only increases the amount of destruction when a hurricane strikes.

(MUSIC)

VOICE ONE:

SCIENCE IN THE NEWS was written by Nancy Steinbach and Caty Weaver and produced by Brianna Blake. I'm Bob Doughty.

VOICE TWO:

And I'm Faith Lapidus. A link to the National Hurricane Center, along with transcripts19 and audio files of our programs, can be found at www.unsv.com. Listen again next week for more news about science in Special English on the Voice of America.


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1 weaver LgWwd     
n.织布工;编织者
参考例句:
  • She was a fast weaver and the cloth was very good.她织布织得很快,而且布的质量很好。
  • The eager weaver did not notice my confusion.热心的纺织工人没有注意到我的狼狈相。
2 doughty Jk5zg     
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 cyclones 17cc49112c36617738bb1601499ae56d     
n.气旋( cyclone的名词复数 );旋风;飓风;暴风
参考例句:
  • The pricipal objective in designing cyclones is to create a vortex. 设计旋风除尘器的主要目的在于造成涡旋运动。 来自辞典例句
  • Middle-latitude cyclones originate at the popar front. 中纬度地区的气旋发源于极锋。 来自辞典例句
4 equator piJzt     
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。
5 hemisphere xy4yd     
n.半球,半球地图
参考例句:
  • This animal is to be found only in the Southern Hemisphere.这种动物只有在南半球才能找到。
  • In most people,the left hemisphere is bigger than the right.多数人的左脑比右脑大。
6 surge Mrlwi     
n.汹涌,澎湃;vi.汹涌,强烈感到,飞涨;vt.放开,松手
参考例句:
  • The surge travelled southwards along the coast.浪涛沿着海岸向南涌去。
  • It failed to stimulate a surge of investment in industry.这没有能刺激工业投资的激增。
7 surges 48aaefca298cc52a954e31429e6637ac     
n.奔涌向前( surge的名词复数 );(数量的)急剧上升;(感情等)洋溢;浪涛般汹涌奔腾v.(波涛等)汹涌( surge的第三人称单数 );(人群等)蜂拥而出;使强烈地感到
参考例句:
  • The Yellow River surges onward like ten thousand horses galloping. 黄河以万马奔腾之势滚滚向前。 来自《现代汉英综合大词典》
  • The raging tide of revolution surges forward. 革命怒潮汹涌澎湃。 来自《现代汉英综合大词典》
8 smashes 2dd6dbd036993d6ab220498a791e5f3d     
v.打碎,捣烂( smash的第三人称单数 );捣毁;重击;撞毁(车辆)
参考例句:
  • It's the lunatic fringe of the Animal Liberation Front which smashes the windows of butchers' shops, not ordinary members like us. 是“动物解放阵线”的极端分子打碎了肉店的玻璃窗,可不是我们这样的普通成员。 来自《简明英汉词典》
  • He smashes the watch in frustrrustration. 将军此刻的心情是得意与失意参半。 来自辞典例句
9 coastal WWiyh     
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。
10 atmospheric 6eayR     
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。
11 destructive cvaxr     
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。
12 gulf 1e0xp     
n.海湾;深渊,鸿沟;分歧,隔阂
参考例句:
  • The gulf between the two leaders cannot be bridged.两位领导人之间的鸿沟难以跨越。
  • There is a gulf between the two cities.这两座城市间有个海湾。
13 proceedings Wk2zvX     
n.进程,过程,议程;诉讼(程序);公报
参考例句:
  • He was released on bail pending committal proceedings. 他交保获释正在候审。
  • to initiate legal proceedings against sb 对某人提起诉讼
14 intensity 45Ixd     
n.强烈,剧烈;强度;烈度
参考例句:
  • I didn't realize the intensity of people's feelings on this issue.我没有意识到这一问题能引起群情激奋。
  • The strike is growing in intensity.罢工日益加剧。
15 Celsius AXRzl     
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。
16 currently SvMzI2     
adv.通常地,普遍地,当前
参考例句:
  • Currently it is not possible to reconcile this conflicting evidence.当前还未有可能去解释这一矛盾的例证。
  • Our contracts are currently under review.我们的合同正在复查。
17 density rOdzZ     
n.密集,密度,浓度
参考例句:
  • The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
  • The region has a very high population density.该地区的人口密度很高。
18 risky IXVxe     
adj.有风险的,冒险的
参考例句:
  • It may be risky but we will chance it anyhow.这可能有危险,但我们无论如何要冒一冒险。
  • He is well aware how risky this investment is.他心里对这项投资的风险十分清楚。
19 transcripts 525c0b10bb61e5ddfdd47d7faa92db26     
n.抄本( transcript的名词复数 );转写本;文字本;副本
参考例句:
  • Like mRNA, both tRNA and rRNA are transcripts of chromosomal DNA. tRNA及rRNA同mRNA一样,都是染色体DNA的转录产物。 来自辞典例句
  • You can't take the transfer students'exam without your transcripts. 没有成绩证明书,你就不能参加转学考试。 来自辞典例句

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