Embedded Files
When air ascends, eventually it cools so much that water vapor starts condensing out into liquid form. It's difficult to form a water droplet out of a collection of water molecules in gas form. The water usually needs something to condense onto. The atmosphere has plenty of candidate particles, called condensation nuclei, which allow water to condense onto them in liquid form. As this takes place, you get many, many tiny water droplets, and a cloud is born.
By the way, the visible part of a cloud, and steam or fog for that matter, is all the little liquid water droplets; water vapor (the gas form of water) is transparent.
As the air continues to ascend and cool, and the cloud continues to grow, the existing cloud droplets get bigger and bigger. Well, "bigger" is relative; most cloud droplets are just a few microns in diameter. And such tiny droplets pretty much float in the air without falling.
Raindrops are much bigger than cloud droplets - usually a few millimeters in diameter, hundreds of times the diameter of a cloud droplet. So how do you make big raindrops out of little cloud droplets?
Report abuse