Earth like planet has 3 atm pressure at it sea level. How would it affect its rainfall system?

1) Using internet calculator I got a result that boiling point for water would be 131°C, while freezing point would remain very close to 0°C. Would it affect evaporation rate under more normal conditions, like for example near 10°C?

2) The absolute humidity is only temperature dependent, thus no change here. (source: https://en.wikipedia.org/wiki/Relative_humidity#Misconception) Right?

3) Further condensation is theoretically not air pressure related but temperature related, so no direct change here, right? (source: http://www.ems.psu.edu/~fraser/Bad/BadClouds.html). However I’m not sure, how air pressure would affect condensation by being able to hold in air for longer cloud condensation nuclei?


1 Answer 1


There are two concepts at play here: the partial pressure of a gas is the pressure if just that gas in a gas mixture occupied the full volume. Vapor pressure is the pressure that a vapor exerts on its condensed phase and is proportional to the evaporation rate.

If atmospheric pressure goes up, partial pressure of water as a component of atmosphere would go up, so vapor pressure of water would go up. That means evaporation rate would go up. That means, you would need higher temperatures on average to evaporate water, and to create rain.

That so far is science fact. Assuming that your temps stay the same, the planet-wide result should be that more water is stored in the air at any given temperature, and less is released as rain. So I think the planet would everywhere be dryer. This part is assumption, the relevant equations for this simple extrapolation are covered in the Wikipedia articles I linked.

As a more speculative though, because the air can store more water total, that means that certain effects that cause alot of rainfall might cause even more rainfall. If a cold and warm front meet in a thundercloud, there would eb more rain to release, so potentially more would be released. If the monsoon clouds that hit the Himalayas had more water in them, then the monsoon rains in India might increase.

I have no idea if that last paragraph is correct, so you can ignore it if you want a more science based answer.


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