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  • 龙卷风

    Destruction from a tornado, showing debris scattered around damaged houses and vegetation.
     

    Where do you go to see a tornado? Tornado Alley!
    ::你去哪里看龙卷风?

    Tornadoes are deadly serious. The deadliest in recent years killed 158 people in Joplin, Missouri in 2011. More than 550 people died in the United States from tornadoes that  year . The deadliest tornado on record killed 629 people in 1926. This "tri-state" tornado raced across Missouri, Illinois, and Indiana.
    ::龙卷风是致命的。 近些年来最致命的龙卷风2011年在密苏里州约普林(Joplin)杀死了158人。 美国当年有550多人死于龙卷风。 1926年,史上最致命的龙卷风杀死了629人。 这一“三州”龙卷风横跨密苏里州、伊利诺伊州和印第安纳州。

    Tornadoes
    ::龙卷风

    Severe   have a lot of  energy  and strong  winds . This allows them to produce tornadoes. A  tornado  ( Figure   ) is a funnel-shaped   of whirling high winds. The funnel moves along the ground, destroying everything in its path. As it moves, it loses energy. Before this happens, it may have gone up to 25 kilometers (16 miles). Fortunately, tornadoes are narrow. They may be only 150 meters (500 feet) wide. Tornadoes are also called twisters.
    ::严重性强的能量和强风很大, 使得它们能够生产龙卷风。 龙卷风( 数字) 是高风的漏斗形。 漏斗沿着地面移动, 摧毁了它道路上的一切。 随着它移动, 它会失去能量。 在此之前, 它可能已经达到25公里( 16英里 ) 。 幸运的是, 龙卷风是狭窄的, 它们可能只有150米( 500英尺)宽。 龙卷风也被称为“ 扭动器 ” 。

    A funnel-shaped tornado touching down on a flat landscape under dark storm clouds.
     
    Tornadoes are small but mighty storms.

    Classifying Tornadoes
    ::分类 " 旋风 "

    The winds of a tornado can reach very high speeds. The faster the winds blow, the greater the damage they cause. Wind speed and damage are used to classify tornadoes.  Tornado intensity is measured on the Fujita scale, or F-scale ( Table   ). Since 2007, some meteorologists have also adopted the Enhanced Fujita Scale (EF-scale), which uses a more detailed list of damage indicators.
    ::龙卷风的风能达到非常高的速度。风吹得越快,所造成的损害就越大。风速和损害被用来对龙卷风进行分类。龙卷风强度是用藤田尺度或F尺度(表 ) 测量的。自2007年以来,一些气象学家还采用了“增强藤田尺度(EF尺度) ” , 使用更详尽的损害指标清单。

    F-Scale Rating Wind Speed (kilometers per hour) Wind Speed (miles per hour) Damage
    F0 64-116 40-72 Light - tree branches fall and chimneys may collapse
    F1 117-180 73-112 Moderate - mobile homes, autos pushed aside
    F2 181-253 113-157 Considerable - roofs torn off houses, large trees uprooted
    F3 254-332 158-206 Severe - houses torn apart, trees uprooted, cars lifted
    F4 333-419 207-260 Devastating - houses leveled, cars thrown
    F5 420-512 261-318 Incredible - structures fly, cars become missiles
    F6 >512 >318 Maximum tornado wind speed

    Tornado Alley
    ::龙卷风平面

    Tornadoes can form anywhere in the world, but they are the most common in “Tornado Alley” in the central  United States ( Figure   ).  Why do so many tornadoes occur here? This is where warm, humid   from the south run into cold, dry air masses from the north.
    ::龙卷风可以在世界任何地方形成,但它们在美国中部的“龙卷风平面”中最为常见。 为什么这里会发生如此多龙卷风? 南方的温暖潮湿的潮湿天气从这里进入北方冷干燥的空气中。

    Map showing Tornado Alley and the interaction of air masses in the central United States.
     
    Tornadoes are most common in the central part of the U.S.

    Damage
    ::损坏 损坏

    A tornado only strikes a small area. But it can destroy everything in its path. Most injuries and deaths from tornadoes are caused by flying debris ( Figure   ). In the United States, an average of 90 people are killed by tornadoes each year. The most violent two percent of tornadoes account for 70% of the deaths by tornadoes.
    ::龙卷风只袭击了小片地区,但它可以摧毁其道路上的一切。 龙卷风造成的伤亡大多是由飞尘造成的(图 ) 。 在美国,每年平均有90人死于龙卷风。 最暴力的2%的龙卷风占龙卷风死亡人数的70%。

    Aerial view of tornado damage in Murfreesboro, TN, showing destroyed homes and trees.
     
    Tornado damage that occurred in the City of Murfreesboro, TN when it was struck by an F-4 tornado.

    April 2011
    ::2011年4月

    Late April 2011 saw the deadliest set of tornadoes in more than 25 years. There were more than 150 tornadoes reported throughout one day! Severe thunderstorms came about when two very different air masses met. A warm moist air mass blew north from the Atlantic Ocean and Gulf of Mexico (mT). It rammed into a cold polar air mass (cP) that the was sitting over the region. In addition, the  jet stream  was blowing strongly in from the west ( Figure   ).
    ::2011年4月下旬,25年多以来,龙卷风袭击了最致命的龙卷风。一天中报道了150多起龙卷风!两个截然不同的气团相遇时,发生了严重的雷暴。从大西洋和墨西哥湾向北吹来温暖的潮湿空气。它撞向一个冰冷的极地空气质量,当时该地区上空就座落在其中。此外,喷气流从西部强烈吹入(Figure ) 。

    Satellite view showing air masses and thunderstorms during the April 2011 tornado outbreak.
     
    April 27-28, 2011. The cold air mass is shown by the mostly continuous clouds. The warm air mass is indicated by small low clouds. Thunderstorms are indicated by bright white patches.

    Everyone in the region was told that tornadoes were possible. But it's impossible to know exactly where and when a tornado will touch down. The path it will take is unknown, because tornado movement is not very predictable.
    ::该地区每个人都被告知龙卷风是可能的。但不可能确切知道龙卷风将在何时何地坠落。它所走的道路未知,因为龙卷风运动不太可预测。

     

     

     

    Summary
    ::摘要

    • A tornado is a whirling funnel of air extending down from a cumulonimbus cloud.
      ::龙卷风是一条从云层云层中延伸下来的流星空流。
    • The Fujita scale measures tornado intensity based on wind speed and damage.
      ::根据风速和破坏情况,藤田级规模测量龙卷风强度。
    • Tornadoes can only be predicted over a wide region.
      ::唯有在广大地区才能预测到龙卷风。

    Review
    ::回顾

    1. What causes the tornadoes of Tornado Alley?
      ::是什么导致了龙卷风巷的龙卷风?
    1. Draw a diagram showing why tornadoes strike the middle of the U.S.
      ::绘制一张图表,显示为何龙卷风袭击美国中部。
    1. What circumstances led to all the tornadoes in April 2011?
      ::2011年4月,什么情况导致了所有龙卷风?