Earth and Sky:Raindrops 雨滴

Raindrops 雨滴

From a light rain to a heavy downpour, raindrops fall to Earth's surface. And if you watch over time, you'll see that some raindrops are small and some much larger. Find out why -- on today's Earth and Sky.

DB: This is Earth and Sky, with a question from a listener: "What determines the size of raindrops? Sometimes it's a real fine mist, and other times it's big drops."

JB: A mist isn't technically¹ rain, although many people use the word to indicate a light rain. A mist or fog is a cloud on the ground -- and clouds are made up of very tiny water droplets². These droplets are smaller than the radius³ of a human hair -- too small to fall through the atmosphere as rain.

DB: It takes about a million tiny droplets of mist to make one average-sized raindrop. The drops become raindrops by colliding and coalescing⁴ with each other in the cloud. If the drops get large enough, they fall as rain. The longer the drops stay in the clouds, the larger they're able to grow.

JB: And that's where the type of cloud that produces the raindrop comes in. Inside of high puffy cumulus clouds, winds are strong. Drops are buffeted⁵ by the winds and suspended in the cloud long enough to grow very large.

DB: Then there are stratus clouds -- the relatively⁶ low, often uniformly gray clouds. Winds inside these clouds are relatively weak. Raindrops that fall from these clouds may be very small -- because they fall before they've have a chance to grow.

JB: That's today's show, made possible by the National Science Foundation. And, by the way, to ask your Earth or sky question come see us at earthsky.org. I'm Joel Block, with Deborah Byrd, for Earth and Sky.

1 technically   

adv.专门地，技术上地

参考例句：

• Technically it is the most advanced equipment ever.从技术上说，这是最先进的设备。
• The tomato is technically a fruit,although it is eaten as a vegetable.严格地说，西红柿是一种水果，尽管它是当作蔬菜吃的。

2 droplets   

n.小滴( droplet的名词复数 )

参考例句：

• Droplets of sweat were welling up on his forehead. 他额头上冒出了滴滴汗珠。 来自辞典例句
• In constrast, exhaled smoke contains relatively large water droplets and appears white. 相反，从人嘴里呼出的烟则包含相当大的水滴，所以呈白色。 来自辞典例句

3 radius   

n.半径，半径范围；有效航程，范围，界限

参考例句：

• He has visited every shop within a radius of two miles.周围两英里以内的店铺他都去过。
• We are measuring the radius of the circle.我们正在测量圆的半径。

4 coalescing   

v.联合，合并( coalesce的现在分词 )

参考例句：

• A mental model begins coalescing in their minds. 一个意识模型开始结合到他们的脑子里。 来自互联网
• On the basis of coalescing this kind of element can separate oil from compressed air. 采用凝聚原理，分离压缩空气中的油份。 来自互联网

5 buffeted   

反复敲打( buffet的过去式和过去分词 )； 连续猛击； 打来打去； 推来搡去

参考例句：

• to be buffeted by the wind 被风吹得左右摇摆
• We were buffeted by the wind and the rain. 我们遭到风雨的袭击。

6 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。