Why does Rain Fall in Drops
Rain falls from the clouds in fairly small drops, but could it fall in jets?
Two basic factors ensure that rain falls in drops rather than in jets. First, rain is generated within droplets in clouds, and second, air resistance rips large amounts of water apart as it falls toward the ground.
When warm, moist air moves upward, it gets cooled by the lower temperature of the atmosphere; the resulting vapor condenses into droplets, generating clouds.
The droplets are extremely tiny and are so light that they float. In order for the water to collect into a raindrop, a microscopic speck of dust or pollen must also be present in the cloud. Then, the many tiny droplets will settle on the speck and fall to the ground in the shape of a raindrop with a diameter of at least two-hundredths of an inch.
The size of a raindrop depends on many factors, but even if the rain is very heavy, no raindrop will ever have a diameter greater than two-tenths of an inch.
Surface tension, the force that holds a drop together, gets relatively smaller as the raindrop grows bigger. Large drops are thus exposed to greater air resistance, which rips them apart on their way toward the ground. Additionally, the drops often collide with each other, causing them to fall at different speeds, which also prevents them from heading toward the ground as jets.
Rain is often depicted as drops, but it is only drop-shaped when the water is suspended from something, such as a leaf. Small raindrops with diameters of less than four-hundredths of an inch are circular. The larger the drop, the less surface tension it has and the flatter it becomes, until air resistance causes it to inflate like a parachute before ripping it apart.