Name: 【TED-Ed】龍捲風是如何形成的？ How do tornadoes form? - James Spann (How do tornadoes form? - James Spann)
Uploaded: 2020-10-20T21:01:10.000Z
Duration: 4 min 12 s

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

當起風、和其他條件成立時，我就會跳上車跟著那些猛烈的暴風跑。

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

你們覺得我瘋了嗎？也許吧！但我追逐這些空中的野獸只是想多了解它們一點。

我想跟你們分享一下我的發現。

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

龍捲風是高速旋轉的空氣柱，在風暴的內部形成，並通過漏斗雲與地面連接。

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

當它發生時，它們橫掃經過的地方會造成生命財產的重大損傷。

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.

為此有很多針對這個天然災害的研究，但對它形成的原因， 仍有許多未解之謎。

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

一個龍捲風成形的條件，未必能讓另一個龍捲風也成形。

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.

但自人們開始記錄龍捲風以來，我們已經學到了很多，比如說怎麼辨識龍捲風在空中醞釀的徵兆。

Tornadoes begin with a thunderstorm but not just any thunderstorm.

龍捲風的前兆是雷雨， 但不是普通的雷雨。

These are especially powerful, towering thunderstorms called supercells.

這些特別強大，高聳的雷雨被稱為「超級雷雨胞」。

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

它們高五萬英呎以上，會帶來強風、大冰雹，有時甚至會淹水、大閃電等。

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.

這些是孕育龍捲風的風暴，但還要再滿足一些特定條件，那些我們可以測量、察覺到， 幫助我們預測龍捲風的指標。

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

「上升氣流」是龍捲風形成所需的首要條件。

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

當水氣凝結時風暴就會形成，而這是製造雲時的產物。

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

凝結時會釋放出熱量，而熱量會變成推動龐大上升氣流的能量。

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

水氣凝結越多且暴風雲越大，這些上升氣流就會變得越強大。

In supercells, this rising air mass is particularly strong.

在超級雷雨胞中， 這種上升的氣團特別強大。

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

當空氣上升後，它會改變方向並開始更快速移動。

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.

最後，如果水氣夠的話，在風暴的基底，會發展成巨大的「雲底」，如果龍捲風形成， 就能在之後為其提供所需的能量。

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.

當一切就緒， 雲團中心會形成渦流，再發展成向上吸引的巨大管狀旋風。

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

外面的乾冷下沉空氣開始從中氣旋的後方捲入，形成所謂的「後側下沉氣流」。

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.

這樣特殊的現象會造成中氣旋裡外強烈的溫差，從而形成一定程度的不穩定性， 進一步助長龍捲風壯大。

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

之後中氣旋底部會收緊，風速因此增加。

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,

如果，我是說假如， 這個漏斗狀的氣旋往下移，接觸到雷雨胞下層潮濕豐沛的雲底，

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.

就會吸收雲底變成快速旋轉的雲牆， 最後再向下觸及地面。

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

一旦這道快速旋轉的雲柱碰觸到地面就成了「龍捲風」。

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.

龍捲風大多小又短命， 風速約每小時 65 到 110 英里，但有些風速可達每小時 200 英里， 而且維持一個小時左右。

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

雖然很美但很恐怖，尤其是當你本人或你家在它的行進路線時。

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

這時候沒有人，包括我這樣的追風少年在內，會想看接下來的結果。

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

就跟萬物一樣， 龍捲風也有走到盡頭的時候。

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.

當溫差消失、各項條件趨於穩定，或是空氣中的溼度降低、雷雨胞能量耗盡，龍捲風就會慢慢消散。

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.

儘管到了這個階段， 氣象學家或追風少年如我仍在密切關注，一直在觀察暴風雨什麼時候再次放下它的長繩。