书城教材教辅智慧教育活动用书-星宇迷尘
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第5章 Flocks of “Elephants” Made in the Sky

Do you wonder how much a cloud weighs? What about a hurricane? A meteorologist① has done some estimates② and the results might surprise you.

Let’s start with a very simple white puffy③ cloud—a cumulus④ cloud. How much does the water in a cumulus cloud weigh? A senior scientist at the National Center for Atmospheric Research in Boulder, Colorado did the numbers.

“The water in the little cloud weighs about 550 tons,” she calculates. “If you want to convert it to something that might be a little more meaningful, think of elephants.”

Assume an elephant weighs about six tons, so that it would mean that water inside a typical cumulous cloud would weigh about one hundred elephants, says she.

Water suspended⑤ in the sky is as weigh as a hundred elephants. This would beg another question—what keeps it up there?

“First of all, particles forming water are not as big as elephants,oppositely,they are very tiny and tiny. ”Explains she.

And those particles floating on the warmer air rising below. But still, the concept of so much water float in the sky was surprising, even to a meteorologist.

“I really had no idea how much a cloud would weigh when I started the calculations,” she says.

So how many elephant units of water are inside a big storm cloud—10 times bigger all the way around than the “puffy” cumulus cloud? Again, she did the number: about 200,000 elephants.

Now, ratchet up the calculations for a hurricane like Missouri about the sum of water inside it, massive figures will be there.

“What we’re doing is weighing the water in one cubic meter of cloud theoretically and then multiplying by the volume of a whole hurricane,” she explains.

Do you wonder the result? Forty million elephants! That means that the water in one hurricane weighs more than all the elephants on the planet. Perhaps even more than all the elephants that have ever lived on the planet.

① meteorologistn. 气象学者

② estimaten. 估计,估价,估计数

③ puffyadj. 胀大的,肥满的

④ cumulusn. 积云,堆积

⑤ suspendv. 使飘浮,使悬浮

空中有群水做的“象”

想知道一朵云有多重吗?还有飓风?一位气象学家做了大概的估算,结果可能会让你大吃一惊。

先从一团很普通的蓬松的白色积雨云算起。一朵积雨云所含的水有多重呢?一位科罗拉多州玻尔得国家大气研究中心的资深科学家算出了一组数据。

她推算:“一小片云大约含有550吨水。如果你想把它转换成更加实际一点的东西,那就想想大象吧。”

她说,假设一头大象有6吨重,那么一朵普通的积雨云所含的水就相当于大约100头大象那么重。

100头大象那么重的水悬在空中,于是另一个问题不得不考虑——是什么让它牢牢的挂在天空中的呢?

“首先,构成水的粒子并没有大象那么大,而是非常非常地小。”她解释说。

而且那些微粒漂浮在正在上升的暖空气上面。但是尽管如此,想到有这么多水漂浮在空中,哪怕气象学家也会觉得不可思议的。

“刚开始计算的时候,我也真的不知道一朵云有多重。”她说。

那么一块儿比“蓬松的”积雨云大10倍的暴风云中含有的水相当于多少只大象呢?这有她再一次得出的数据:大约是20万只。

现在,逐步计算像密苏里飓风那样的热带风暴的含水量,数据真是大的惊人。

“我们正在做的是从理论上测量一立方米的云所含的水的重量,然后再乘以整个飓风的体积。”她解释说。

想知道结果吗?相当于4,000万头大象!这就意味着飓风中所含的水比地球上所有的大象加到一起还要重,也许会超过地球上曾经有过的所有大象体重的总和。