Why can’t rain, or snow, fall in large units? It’s always small, single drops or flakes, and never one huge drop or snowball. The largest precipitation we see is normally hail, which can fall in single units the size of softballs or larger. Why can’t the other types fall in units that large?
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All precipitation starts in the clouds which are technically just giant piles of fog. It’s the only way water can stay up high because liquid water is too heavy and will fall immediately. If, for one reason or another, that fog starts to condense into drops, these drops just fall as soon as they become heavy enough, hail requires very specific conditions to become bigger. So, these units just can’t manage to grow big enough.
Think of clouds as a dense mist of water. When it condenses or gets too heavy, it drops and doesnt have time to gather more.
Think about the condensation on the outside of a cold water bottle. You see the individual droplets form, and as they fall they catch other droplets and get bigger as they fall. With rain in clouds, they just drop straight down and have a really small chance to catch another droplet and get bigger
Rain drops can only form around dust particles (there are physics/energy reasons why water cant condense into very small raindrops without something to form on) because of this, rain starts and small drops that get bigger, not the other way around.
Now as those drops get bigger by fusing with other drops their surface area increases and there is more area for “wind” to hit. At some point this will split the drop preventing a large layer of water from just falling to the ground.
Of course ice can get around this since it is a solid. Large hail usually forms when small hail is blown back up into clouds by an updraft to pick up more water. It might circulate a few times before it falls to the ground.
If you take a big bucket to the top of a building and turn it over you get raindrops, not abucket-sized blob after only 5-10 floors. Why?
The force of air resistance is a function of speed squared. The force of surface tension, which is what’s holding the drop together goes up as the drop gets smaller.
Lots of air resistance on the outside of the blob shears it into smaller blobs until the drops get enough surface tension to hold them together. This continues as the drops speed up until the air resistance equals their weight, their termanil velocity. That’s the size of raindrops.
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