雙語(yǔ)閱讀：揭秘“暴風(fēng)雨前的寧?kù)o”

　　導(dǎo)語(yǔ)：當(dāng)我們描述在某個(gè)危險(xiǎn)來(lái)臨或大事件爆發(fā)的前夕所出現(xiàn)的那種異樣的寧?kù)o時(shí)，我們總會(huì)說(shuō)“暴風(fēng)雨前的寧?kù)o”，不過(guò)這個(gè)說(shuō)法有沒(méi)有什么科學(xué)依據(jù)呢?讓本文為你揭曉答案吧!

　　你可曾有過(guò)這樣的經(jīng)歷：某天下午正在后院燒烤或者打籃球的時(shí)候，突然發(fā)現(xiàn)一切瞬間變得安靜下來(lái)，空氣似乎凝結(jié)了，連鳥(niǎo)兒也不再歌唱而轉(zhuǎn)身躲回窩里去了?

　　Have you ever spent an afternoon in the backyard, maybe grilling or enjoying a basketball game, when suddenly you notice that everything goes quiet? The air seems still and calm—even the birds stop singing and quickly return to their nests.

　　幾分鐘后，你感覺(jué)到空氣中有所變化，忽然之間一排烏云出現(xiàn)在地平線上，讓人有種不祥的預(yù)感——烏云的樣子好像是在告訴你它們可不只是做做樣子而已。你急沖進(jìn)屋里，險(xiǎn)些被瓢潑大雨前掉下的大雨點(diǎn)砸個(gè)正著。此時(shí)，你也許會(huì)停下來(lái)問(wèn)自己：“為什么暴風(fēng)雨來(lái)臨前是那么寧?kù)o安詳呢?”

　　After a few minutes, you feel a change in the air, and suddenly a line of clouds ominously appears on the horizon—clouds with a look that tells you they aren’t fooling around. You quickly dash in the house and narrowly miss the first fat raindrops that fall right before the downpour. At this moment, you might stop and ask yourself, “Why was it so calm and peaceful right before the storm hit?”

　　人們?cè)趲讉€(gè)世紀(jì)前就已經(jīng)發(fā)現(xiàn)這個(gè)神秘的現(xiàn)象了，但究竟是什么原因造成暴風(fēng)雨前的這番寧?kù)o呢?古諺有云“暴風(fēng)雨前的寧?kù)o”，這通常用在比喻的修辭中，描述熱鬧的活動(dòng)以及情緒亢奮前的一段安靜時(shí)間。根據(jù)自身的經(jīng)驗(yàn)，我們也知道事實(shí)上暴風(fēng)雨來(lái)臨前也確實(shí)是寧?kù)o的。但這是什么原因造成的呢?暴風(fēng)雨前總是平靜么?讓我們來(lái)聽(tīng)聽(tīng)科學(xué)家們的解釋。

　　It’s an intriguing phenomenon that people have recognized for centuries, but what on earth causes this calm? And there is an old phrase “calm before the storm”, often used in its figurative meaning—a quiet period just before a great activity or excitement. According to our own experience, we know there is literally calm before the storm. But what causes this calm? And is it always calm before the storm? Let’s hear what scientists have to say.

　　答案是：有時(shí)如此，有時(shí)則不然。在特定的情況下，暴風(fēng)雨來(lái)臨前會(huì)出現(xiàn)令人恐懼的或是祥和的寂靜，降臨在你野餐的時(shí)候。其他種類的暴風(fēng)雨則直接跳過(guò)寂靜的步驟，猶如在驕傲地宣布自己的存在一般，瞬間風(fēng)雨大作。

　　The answer is sometimes there is; sometimes there isn’t. Under the right conditions, an eerie or peaceful calm will befall your picnic before a storm moves in. Other storms skip the calm and proudly announce their presence by instantly unleashing bad weather.

　　平靜時(shí)期出現(xiàn)在一種特定的暴風(fēng)雨中，即最簡(jiǎn)單的暴風(fēng)雨——單細(xì)胞雷暴。在這種類型的雷暴中，通常只有一種主要的上升氣流，即暖濕氣流從地面升起。溫暖濕潤(rùn)的空氣是暴風(fēng)雨形成的必要條件，所以通常會(huì)把它們從周圍的環(huán)境中吸進(jìn)來(lái)。雷暴能夠從周圍任何一個(gè)方向吸進(jìn)自己所需的暖濕空氣——甚至是處在雷暴運(yùn)動(dòng)方向上的空氣也被吸了進(jìn)來(lái)。

　　A period of calm happens in a particular kind of storm, the simplest kind of storm—a single-cell thunderstorm . In this type of thunderstorm, there is usually only one main updraft, which is warm, humid air and drawn from places near the ground. Storms need warm and moist air as fuel, so they typically draw that air in from surrounding environment. Storms can draw in the air that fit their need from all directions—even from the direction in which the storm is traveling.

　　由于暖濕空氣被吸進(jìn)雷暴中，雷暴經(jīng)過(guò)之處就形成了低氣壓真空帶。正在上升的暖濕氣流遇到雷暴云層中原本就存在的干燥冷空氣，此時(shí)熱空氣的溫度下降，里面的水分凝結(jié)成小的水滴——這是形成雨水的前提。這些水滴不斷聚集，包裹住一些大的顆粒(如灰塵)，當(dāng)水滴凝聚到足夠大時(shí)就會(huì)形成降雨。

　　As the warm, moist air is pulled into a storm system, it leaves a low-pressure vacuum in its wake. The rising air meets the cold dry air that has already existed in the storm clouds, thus the temperature of the warm air drops, and the water vapor in it condenses into tiny droplets that are a precondition of rain. These droplets clump up and build on larger particles like dust, until they grow large enough to form raindrops.

　　暖濕氣流持續(xù)上升，但當(dāng)穿越云層時(shí)經(jīng)歷氣溫下降水汽凝結(jié)的過(guò)程，暖濕氣流開(kāi)始冷卻并變得干燥。當(dāng)暖濕氣流達(dá)到云層頂部時(shí)，會(huì)被擠出云層，這股氣流會(huì)翻過(guò)巨大的鐵砧形雷雨云。此時(shí)，氣流開(kāi)始下沉——被其自身上升時(shí)所形成的真空帶吸回低處。干熱的氣流相對(duì)穩(wěn)定，一旦它覆蓋了某一個(gè)地區(qū)，就會(huì)使該區(qū)域的氣流穩(wěn)定下來(lái)，這就造成了暴風(fēng)雨前的平靜。

　　This warm, moist air keeps moving upwards, but it becomes colder and drier during its trip through cloud which involves cooling and condensation. When it reaches the top of the cloud mass, the air gets spit out at the top. This air is sent rolling out over the big, anvil -shaped head of the thunderclouds. From there, the air descends—drawn back toward lower altitudes by the very vacuum its departure created in the first place. Warm and dry air is relatively stable, and once it blankets a region, it stabilizes that air in turn. This causes the calm before a storm.

　　盡管如此，大多數(shù)的雷暴來(lái)臨前并不是一片寧?kù)o。這是因?yàn)樗鼈兇蠖嗍秋L(fēng)向復(fù)雜的暴風(fēng)雨團(tuán)。在暴風(fēng)雨團(tuán)的周圍，有很多氣流頻繁上下流動(dòng)，這就使得這種類型的暴風(fēng)雨來(lái)臨前毫無(wú)平靜可言。相反，這種類型的暴風(fēng)雨來(lái)臨前往往會(huì)狂風(fēng)大作

　　Most thunderstorms, though, don’t start with a calm. That’s because most are actually clusters of storms with complex wind patterns. There’s so much air moving up and down in the vicinity of these storm clusters that the calm before the storm never happens. And instead, before the storm, it might be really windy!