TED - 龙卷风是怎么形成的 How do tornadoes form

They call me the tornado chaser.

他们称我是 “龙卷风追逐者”。

When the wind is up and conditions are right, I get in my car and follow violent storms.

当风来了，其他条件又刚好合适的时候，我就会钻进我的车里去追逐暴风。

"Crazy," you say? Perhaps, but really I chase these sky beasts to learn about them.

也许你会说：“疯了吧你？”但其实我追赶这些空中野兽是为了了解他们。

I want to share with you what I know.

在此，我想跟大家分享一下我所了解的。

Tornadoes are rapidly rotating columns of air that form inside storms that connect with the ground via a funnel of a cloud.

龙卷风是在大风内部形成的高速旋转的空气柱，通过一个漏斗形的云状物和地面连接起来。

When that happens, they tear across the Earth, posing a huge threat to life and property.

当龙卷风形成之后，它们就会快速席卷地面，对生命和财产造成巨大威胁。

Because of this, there's a great deal of research into these phenomena, but the truth is, there's still a lot we don't know about how tornadoes form.

正因如此，有大量针对这种天气现象的研究，但是事实是，我们还是对龙卷风的成因知之甚少。

The conditions that may give rise to one tornado won't necessarily cause another.

我们所了解的形成龙卷风的条件，即使都满足，也不一定会形成另一次龙卷风。

But we have learned a lot since people first started recording tornadoes, like how to recognize the signs when one is brewing in the sky.

但是从人们第一次记录龙卷风以来，我们已经学到了不少东西。比如，当它还在天上酝酿形成的时候，我们怎么识别龙卷风将要来临的信号。

Are you coming along for the ride?

你准备要参与其中了么？

Tornadoes begin with a thunderstorm but not just any thunderstorm.

龙卷风的开始是雷暴，但是却不止是普通的雷暴。

These are especially powerful, towering thunderstorms called supercells.

非常强大，非常激烈的雷暴，被称为超级雷暴云。

Reaching up to over 50,000 feet, they bring high force winds, giant hailstones, sometimes flooding, and great flashes of lightning, too.

超级雷暴云有五万多尺的厚度，它能带来强风，巨大的冰雹，有时会引起洪水和雷鸣。

These are the kinds of storms that breed tornadoes, but only if there are also very specific conditions in place, clues that we can measure and look out for when we're trying to forecast a storm.

这就是孕育着龙卷风的暴风雨，但是只有在一些特殊条件也到位的时候，龙卷风才会形成，当我们想要预测风暴时，还有一些我们可以用来衡量和寻找的线索。

Rising air is the first ingredient needed for a tornado to develop.

上升气流是形成龙卷风所需要的第一个要素。

Any storm is formed when condensation occurs, the byproducts of the clouds.

当凝结发生的时候，风暴就形成了，风暴是云的副产品。

Condensation releases heat, and heat becomes the energy that drives huge upward drafts of air.

凝结释放热量，热量成为驱动大量气流上升的能量。

The more condensation and the bigger the storm clouds grow, the more powerful those updrafts become.

凝结程度越大，并且形成风暴的云团越大时，那些上升气流也就越强。

In supercells, this rising air mass is particularly strong.

在超级雷暴云中，这些上升的气团格外的强大。

As the air climbs, it can change direction and start to move more quickly.

当气流上升的时候，它可以改变方向并且开始以更快的速度移动。

Finally, at the storm's base, if there is a lot of moisture, a huge cloud base develops, giving the tornado something to feed off later, if it gets that far.

最终，在风暴云团的底部，如果有很多的水分，就会形成一个巨大的云底，为之后的龙卷风提供能量，前提是如果真的到了这一步。

When all these things are in place, a vortex can develop enclosed by the storm, and forming a wide, tall tube of spinning air that then gets pulled upwards.

当所有这些东西都准备就绪的时候，一个涡旋会在风暴包围中形成，继而形成一个宽大高耸的高速旋转空气柱，之后被向上拉动。

We call this a mesocyclone.

我们称其为 “中气旋”。

Outside, cool, dry, sinking air starts to wrap around the back of this mesocyclone, forming what's known as a rear flank downdraft.

外部那些又干又冷的下沉气体开始在 “中气旋” 后侧环绕，形成一个 “后侧下环流”。

This unusual scenario creates a stark temperature difference between the air inside the mesocyclone, and the air outside, building up a level of instability that allows a tornado to thrive.

这种特殊的情景使 “中气旋” 内外部的气体间产生了非常明显的温差，由此造成的更高一级的不稳定性使龙卷风更加猖狂。

Then, the mesocyclone's lower part becomes tighter, increasing the speed of the wind.

接着，“中气旋” 靠下的部分会更紧绷，以此给风加速。

If, and that's a big if, this funnel of air moves down into that large, moist cloud base at the bottom of the parent storm, it sucks it in and turns it into a rotating wall of cloud, forming a link between the storm that created it and the Earth.

基于足够的假设，这个漏斗形的气团向下移动，到在母风暴底端的巨大又潮湿的云的下边界（云底），云底会将其吸入，并且把它变成一个旋转的云墙，这个云墙把产生它的母风暴和地面连接起来。

The second that tube of spinning cloud touches the ground, it becomes a tornado.

在这个旋转的中空的云与地面接触的一瞬间，就形成了龙卷风。

Most are small and short-lived, producing winds of 65-110 miles per hour, but others can last for over an hour, producing 200-mile per hour winds.

大部分的龙卷风都是小规模的而且短暂的，产生 65 到 110 英里每小时的风，但是有一些龙卷风能持续超过 1 小时，产生 200 英里每小时的风。

They are beautiful but terrifying, especially if you or your town is in its path.

龙卷风是美丽又令人生畏的，尤其是，如果你或者你的村子在它移动的路线上。

In that case, no one, not even tornado chasers like me, enjoy watching things unfold.

在这种情况下，没有人，甚至像我这种 “风暴追逐者” 也不会享受龙卷风一步步的发展。

Just like everything, however, tornadoes do come to an end.

但是和其他事物一样，龙卷风总是有结束的时候。

When the temperature difference disappears and conditions grow more stable, or the moisture in the air dries up, the once fierce parent storm loses momentum and draws its tornado back inside.

当温差消失并且其他条件都稳定下来的时候，抑或是气体中的水分干燥下来的时候，那个原本猛烈的母风暴就会失去它的动力，然后把它的龙卷风重新拉回去。

Even so, meteorologists and storm chasers like me will remain on the lookout, watching, always watching to see if the storm releases its long rope again.

即使这样，气象学家和那些像我一样的 “风暴追逐者” 也还是会继续守望，观察风暴是否会再次扬鞭。