How does friction control net flow of air around a cyclone and an anticylone?
1 Answer
It slows down the air and reduces the Coriolis effect on the air.
Explanation:
The gradient pressure force is the force that causes air to move from areas of high pressure to areas of low pressure. If this was the only effect the air pressure would quickly balance and we wouldn't have much circulation at all. However, the Earth is rotating.
If you try to draw a line on a piece of paper when someone is turning the paper while you draw, you are going to get a curved line not a straight one. This is the Coriolis effect. The result is the air motion is perpendicular to the pressure gradient force. This holds true in the upper atmosphere. However in the boundary layer (layer closest to the ground) we have an additional force acting. Friction.
Friction causes the air to slow down, and works against the Coriolis effect. The more friction (rougher surface, like hills versus the ocean) the greater the effect. To simplify it, imagine drawing the line on the piece of paper that someone is turning. If you slow down the speed you are moving the pen you can correct for the turning paper to an extent. In the atmosphere this results in the air spiraling into a low (cyclone) or spiraling out of a high (anticyclone).
