Question: how does gravity affect the coriolis effect?

Alexander Allen answered on 12 Mar 2019:

Gravity doesn’t really affect the coriolis force directly. It does allow it to exist, though, with the air on the planet being force to move in a similar direction of the rotating earth.

All fluids when they spin on the earth want to spin “in sympathy” with the earths rotation and this leads to things wanting to turn anti-clockwise in the Northern Hemisphere and clockwise in the Southern.

There is a myth that this is the way water will flow down a drain (like in the bath) but water is too dense and thick to really be affected by such forces and you can get water to go whichever way you like.

HOWEVER tornadoes and hurricanes do obey the rule… spinning anticlockwise in the North and clockwise in the South.