RAINDROP
雨滴
Q. What if a rainstorm dropped all of its water in a single giant drop?
Q．如果一场暴雨中所有的水分都汇聚成一颗巨大的水珠并从天上掉下来会发生什么？
——Michael McNeill
——迈克尔•麦克尼尔
A. IT'S MIDSUMMER IN KANSAS. The air is hot and heavy. Two old-timers sit on the porch in rocking chairs.
A．堪萨斯的某个盛夏，空气燥热而潮湿。门廊里两位老人坐在摇椅里。
On the horizon to the southwest, ominous-looking clouds begin to appear. The towers build as they draw closer, the tops spreading out into an anvil shape.
在西南边的天际，一股不祥的云涌现出来，并在逐渐接近的过程中形成云柱，顶部向外扩散形成铁毡样形状。
They hear the tinkling of wind chimes as a gentle breeze picks up. The sky begins to darken.
老人们听到了微风吹过风铃时发出的丁零声。天色渐渐暗了下来。
Moisture
湿气
Air holds water. If you walled off a column of air, from the ground up to the top of the atmosphere, and then cooled the column of air down, the moisture it contained would condense out as rain. If you collected the rain in the bottom of the column, it would fill it to a depth of anywhere between zero and a few dozen centimeters. That depth is what we call the air's total precipitable water (TPW).
空气中携带着水分。如果你从地面开始向上竖起一道墙直至大气层顶端，使包围在其中的空气柱降温，其中所含的水分就会凝结成雨。如果你在底部收集这些雨水，就会发现雨水的深度在零到几十厘米之间。这个深度就是我们所说的空气的总可降水量（TPW）。
Normally, the TPW is 1 or 2 centimeters.
通常来说，总可降水量为1～2厘米。
Satellites measure this water vapor content for every point on the globe, producing some truly beautiful maps.
卫星会测量地球上每一点的水蒸气含量，并得到一些非常漂亮的地图。
We'll imagine our storm measures 100 kilometers on each side and has a high TPW content of 6 centimeters. This means the water in our rainstorm would have a volume of:
不妨假设一个暴雨云团长宽各100千米，具有较高的总可降水量——6厘米。这意味着整个云团中含水：
That water would weigh 600 million tons (which happens to be about the current weight of our species). Normally, a portion of this water would fall, scattered, as rain-at most, 6 centimeters of it.
这些水的质量有6亿吨（恰好差不多是人类的总重量）。一般情况下，其中一部分水会分散地落下来形成雨，降水量最多也是6厘米。
In this storm, all that water instead condenses into one giant drop, a sphere of water over a kilometer in diameter. We'll assume it forms a couple of kilometers above the surface, since that's where most rain condenses.
而在这个云团中，所有的水都凝结成了一大滴水，一个直径超过1千米的水球。假设这个水球离地若干千米，绝大多数雨都在这里冷凝形成。
The drop begins to fall.
然后巨大的水滴开始下落。