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  • 雷暴

    A golf course under dark, stormy skies, highlighting lightning risk during thunderstorms.
     

    How do you get struck by lightning?
    ::你怎么被闪电击中的?

    An average of 55 people die from  lightning  strikes each  year  in the United States. Here's your best chance for being struck by lightning, according to NASA. Go golfing on a July Sunday at around 4 pm, especially in Florida. The golf club up in the air acts as a lightning rod. The late afternoon in July is a great time for thunderstorms. Florida is prone to thunderstorms, and Sunday is a  day  on which a lot of people like to golf. In other words, don't do these things!
    ::在美国,每年平均有55人死于闪电袭击。根据美国航天局,这是你被闪电击中的最佳机会。7月4日星期日下午4点左右去打高尔夫球,特别是在佛罗里达。空中的高尔夫俱乐部起到闪电棒的作用。7月的下午是雷暴的大好时机。佛罗里达容易发生雷暴,星期天是很多人喜欢打高尔夫的一天。换句话说,不要做这些事情!

    Thunderstorms
    ::雷暴暴

    Thunderstorms  are known for their heavy  rain  and lightning. In strong thunderstorms,  hail  and high  winds  are also likely. Thunderstorms are very common. Worldwide, there are about 14 million of them each year! In the U.S., they are most common—and strongest—in the Midwest.
    ::雷暴以大雨和闪电闻名。 在强暴暴中,冰雹和高风也有可能。雷暴非常常见。 全世界每年约有1400万暴风雨。 在美国中西部,暴风雨最为常见,而且最强。

    Thunderstorm Formation
    ::雷暴形成

    Thunderstorms form when the ground is really hot ( Figure   ). The air near the ground becomes very warm and humid. This is true in some locations in late afternoon or early evening in spring and summer. The warm air rises rapidly, which creates strong updrafts. When the rising air cools, its  water vapor  condenses. The updrafts create tall cumulonimbus  . Winds blow the cloud top sideways. This makes the well-known anvil shape of a cloud known as a thunderhead ( Figure   ).  Water  droplets and ice fly up through the cloud. When these droplets get heavy enough, they fall. This starts a downdraft. A  convection cell  develops within the cloud. A mature thunderstorm produces gusty winds, lightning, heavy rain, and hail.
    ::当地面非常热时,雷暴就会形成(图 ) 。 地面附近的空气会变得非常温暖和潮湿。 在下午晚或春夏初的某个地方, 确实如此。 温暖的空气会迅速上升, 形成强大的上升气流。 当上升的空气冷却时, 水蒸气会凝结。 上升的气流会形成高高的二次暴风雨。 风会吹向云顶端。 这让被称为雷头的云形( 图 ) 。 水滴和冰在云中飞过。 当这些水滴变得足够重时, 它们会坠落。 这开始下气流。 在云中形成一个对流细胞。 成熟的雷暴会产生大风、 闪电、 大雨和冰雹。

    Anvil-shaped thunderhead cloud forming during a thunderstorm in a clear sky.
     
    A thunderhead is a cumulonimbus cloud.
    Stages of thunderstorm development: towering cumulus, mature, and dissipating stages with airflow directions.
     
    Formation and disappearance of a thunderstorm.

    Lightning and Thunder
    ::闪电和雷雷

    During a thunderstorm, some parts of a thunderhead become negatively charged. Other parts become positively charged. The difference in charge creates lightning.  Lightning  ( Figure   ) is a huge release of electricity. Lightning can jump between oppositely charged parts of the same cloud, between one cloud and another, or between a cloud and the ground. Lightning blasts the air with  energy . The air heats and expands so quickly that it explodes. This creates the loud sound of  thunder .
    ::雷暴期间,雷电头的某些部分受到负电,其他部分则受到正电。电源差异产生闪电。闪电(图)是巨大的电力释放。闪电可以在同一云的相反充电部分之间、一个云与另一个云之间、一个云与另一个云之间、或一个云与地面之间跳动。用能量点亮空气。空气热和膨胀速度之快,爆炸速度之快。这产生了雷声的响亮。

    Do you know why you always hear the boom of thunder after you see the flash of lightning? It’s because light travels faster than sound. If you count the seconds between seeing lightning and hearing thunder, you can estimate how far away the lightning was. A lapse of five seconds is equal to about a mile.
    ::你知道为什么你总是在看到闪电闪电后听到雷声的响起吗?这是因为光速比声音快。如果你在看到闪电和听到雷声之间数秒,你就可以估计闪电的距离。 5秒钟的误差等于一英里左右。

    Lightning strikes during a thunderstorm illuminating the dark clouds and landscape.
     
    Lightning flashes during a thunderstorm

    The End
    ::结束

    The downdrafts cool the air at the base of the cloud. The air is no longer warm enough to rise.  Convection  shuts down and the thunderhead runs out of energy. A thunderstorm usually ends only 15 to 30 minutes after it begins. New thunderstorms may start in the same area.
    ::下风使云底的空气冷却, 空气不再温暖, 不再能升起。 对流关闭,雷头耗尽能量。 雷暴通常在开始后15至30分钟结束。 新的雷暴可能在同一地区开始。

    Many thunderstorms form individually. During some  , they form in  squall lines , long lines of thunderstorms, along a  cold front . Squall lines form in spring and early summer in the Midwestern United States. This is because the maritime tropical (mT)   from the Gulf of Mexico meets the continental polar (cP) air mass from Canada ( Figure   ).
    ::许多暴风雨是个别形成的。在有些暴风雨中,暴风雨在寒冷的战线上形成,暴风雨在寒冷的战线上形成。 暴风雨在春季和夏季初在美国中西部形成。 这是因为墨西哥湾的海洋热带(mT)与加拿大的大陆极地(cP)空气质量相撞(图 ) 。

    Weather radar mosaic showing thunderstorms and precipitation across the northeastern United States.
     
    Cold air from the Rockies collided with warm, moist air from the Gulf of Mexico to form this squall line.

    Summary
    ::摘要

    • Thunderstorms grow where ground temperatures are extremely high.
      ::雷暴在地面温度极高的地方生长。
    • Convection in the cloud causes raindrops or hailstones to grow. Downdrafts ultimately end convection.
      ::云层的对流导致雨滴或冰雹的生长。 下方的对流最终会结束对流。
    • Squall lines are long lines of thunderstorms that form along a cold front.
      ::暴风雪是沿寒冷前线形成的 长长的雷暴

    Review
    ::回顾

    1. Why are thunderstorms so common?
      ::为什么雷暴如此常见?
    1. What is the energy source that feeds a thunderstorm?
      ::是什么能量源能滋养雷暴?
    1. What two atmospheric processes lead to the formation of the anvil-shaped clouds?
      ::哪些两种大气过程导致圆形云的形成?
    1. What causes a thunderstorm to end?
      ::是什么导致了暴风雨的结束?

    Explore More
    ::探索更多

    Use the resource below to answer the questions that follow.
    ::利用以下资源回答以下问题。

     

     

    1. What causes thunderstorms to develop?
      ::是什么导致暴风雨的爆发?
    1. What determines the severity of the storm?
      ::什么决定风暴的严重性?
    1. What causes the air to rise?
      ::是什么导致空气上升?
    1. What causes the air mass to cool? What happens to this rising cooler air?
      ::是什么导致空气质量冷却?
    1. What causes lightning and thunder?
      ::是什么导致闪电和雷电?