Submitted by wjd03 t3_zihh24 in askscience
Indemnity4 t1_izvb6v4 wrote
> Do we know if raindrops are bigger or smaller nowadays? Or if they fall faster than they used to?
Really fun deep dive into atmospheric sciences.
The main effects on rain drop size are air temperature, water drop temperature, air density and atmospheric pressure. None of those are hugely variable due to climate change compared to natural cycles.
Air pollution has a much more dramatic effect on raindrops than does atmospheric CO2 levels. Atmospheric dust or diesel fuel emissions from cars have huge effects; atmospheric CO2 not so much.
At a simple level, there is no historical change. An individual rain drop is the same size and falls at the same rate it always has, which is the terminal velocity for that droplet. It fits into a distribution range of sizes called the Marshall–Palmer distribution.
Rain drop size (and subsequent speed) naturally vary with the seasons and where exactly it is raining. For instance, rain over the oceans is smaller droplets at slower speed, whereas rain over land is bigger droplets at faster speed.
Air pollution affect example: an area may have a lot of atmospheric dust/pollution that forces a lot of smaller droplets or drizzle (e.g. London fog from period dramas). Remove that air pollution and the rain drop size and speed will change to larger drops / faster speed (e.g. there is no more soupy London fog once the coal fired power stations closed/cleaned their emissions.)
Global changes to rainfall patterns due to climate change get too long for a simple post. But the actual rain drops themselves are relatively stable and predictable.
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