What is the theory of a raindrop?

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In summary, the theory of a raindrop suggests that its size is primarily influenced by surface tension and external stresses, but can also be affected by factors such as evaporation and air resistance. In humid air, a raindrop is able to collect more water than it evaporates, making evaporation a negligible factor. However, in low humidity areas, virga can occur where raindrops completely evaporate before hitting the ground. Temperature may also play a role in the size of a raindrop.
  • #1
mersecske
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What is the theory of a raindrop?

What kind of effects influence its size?
I think that the size is increasing due to the smaller drops (spray)
But what about evaporation, because the drop has large velocity
 
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  • #2


As to size, I'd think that the primary deciding factors are surface tension vs. external stresses such as g force and air resistance.
 
  • #3


I would have thought the maximum size was set by the time it had to form.
Bigger than a certain size it's going to fall, unless there is an up draught to hold it then it's going to fall as rain before it has time to grow
 
  • #4


If a raindrop falls through a uniform density fog, collecting the mist and increasing its size (collecting mass from the region it traverses and neglecting evaporation and air drag) from rest at zero radius as it falls, it will fall with a constant downward acceleration less than g. (Related to problem 8-22 in Becker "Introduction to Theoretical Mechanics."

Bob S
 
  • #5


Why can we neglect evaporation?
 
  • #7


mersecske said:
Why can we neglect evaporation?

Because in humid air, it collects much more water than it evaporates.

If there is more evaporation, then it's certainly not raining.
 
  • #8


Virga is a type of rain shower over very low humidity desert areas where the raindrops completely evaporate before hitting the ground.

Bob S
 
  • #9


Thanks, so both effects are important. Are there any other effects? For example temperature changing?
 
  • #10


Bob S said:
Virga is a type of rain shower over very low humidity desert areas where the raindrops completely evaporate before hitting the ground.

Bob S

Just to clarify, it doesn't have to be a desert. Such occurs here in Alberta on a regular basis.
 

FAQ: What is the theory of a raindrop?

1. What is the theory of a raindrop?

The theory of a raindrop is a scientific explanation for how and why raindrops form in the Earth's atmosphere. It involves understanding the processes of evaporation, condensation, and precipitation.

2. How do raindrops form?

Raindrops form when warm air rises and cools, causing water vapor to condense into liquid droplets. These droplets continue to grow as they collide with other droplets and eventually become heavy enough to fall as rain.

3. Why are raindrops different sizes?

The size of a raindrop can vary depending on the humidity, temperature, and atmospheric conditions where it forms. Smaller raindrops are more common in warmer climates, while larger raindrops tend to form in colder climates.

4. What is the shape of a raindrop?

Raindrops are not perfectly round, as commonly depicted in drawings. They are actually shaped more like a hamburger bun, with a flat bottom and a rounded top. This is due to the air resistance and pressure as the raindrop falls through the air.

5. How fast do raindrops fall?

The speed of a raindrop can vary depending on its size and the air resistance it encounters. On average, small raindrops fall at a rate of about 7 miles per hour, while larger raindrops can fall at speeds of up to 18 miles per hour.

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