What factors affect air movement?

1 Answer
Jul 26, 2015


Pressure gradient, Coriolis effect, and friction.


Air moves from areas of high pressure to areas of low pressure. If you inflate a balloon it becomes an area of high pressure, and if you puncture that balloon the air quickly moves from inside the balloon to outside the balloon where the air pressure is lower.

If that was the only factor that effected air movement then equilibrium would soon be achieved and there would be no more air movement. Since there is almost constant air movement of some kind or other we know this is not the case.

The Coriolis effect is the deflection of moving air caused by the rotation of the Earth. If you take a paper plate and a marker, put a big H in the middle and an L near the edge and draw a line from one to the other. This is how air moves without the Earth rotation being taken into consideration. Now put the L at the 12 o'clock position and draw the line again. Only this time rotate the plate, while you draw a line from the center to the 12 o'clock position. Now you have a curved line that doesn't actually connect the H to the L.

If the plate was a ball and the ball kept rotating and you kept trying to draw lines from the H to the L you would end up with lines that run parallel between the H and L. This is what happens in the atmosphere. In the Northern Hemisphere if you put your back to the wind, the low pressure is on your left side.

Finally there is friction. This only effects the air movement in contact with the Earth (known as the boundary layer). Friction slows down the air and if the air moves slower the Coriolis effect becomes less pronounced. In the atmosphere this means that the air near the surface of the Earth does not move directly parallel between areas of high pressure and low pressure, but gets slightly deflected inward toward a low pressure or outward from a high pressure. His is why low pressures eventually fill and high pressures subside.