There’s a fair amount of discussion about why Europe is (for its latitude) so much warmer than America, but I can’t seem to find any explanations about why Europe is so dry compared to America.
To explain what I’m talking about, I’ve been looking into the climate data on Wikipedia of European and American cities recently and have noticed a very sharp difference their average precipitation levels. Specifically, European cities consistently seem to receive around 20-30 inches (about 500-760 mm) of rain a year whereas American cities east of the 98th degree longitude (about in the middle of Texas) receive somewhere between 40-60 inches (around 1000-1500 mm). The only European exceptions seem to be western parts of Ireland, the UK, and mountainous areas like northern Spain.
Even American cities in the plains west of the 98 receive rain comparable to places like Volgograd (between 15-20 inches) and places like Phoenix receive rain about equal to Atyrau (a Kazakhstani city on the north coast of the Caspian).
What makes this especially odd to me is that Europe, as a geographic entity, seems like it should receive more rain than America, given that most land in Europe is substantially closer to water compared to most places in America.
In: Planetary Science
Answer: it’s because of the rotation of the earth and the oceans. Basically the sun heats the ocean which puts water in the air. Due to the rotation of the earth the air moves from east to west (kind of, it’s also not inaccurate to say that the land moves from west to east and the air stays put) in sort of a loop north of the equator that goes west near the equator, hooks north as it nears the Americas, goes east back out away from the Americas in colder more polar water and then loops back south along Europe and Africa.
Since air picks up moisture when it’s hot over water and loses moisture when it’s either dry or cold or both you have the most “wet” air on the leg of the loop where it hits the Americas.
The other place you see it even more extreme is the western coasts of Asia where there’s a similar phenomenon but because the pacific is so much bigger pacific storms are even more wet
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