Why does wind inside a stadium blow opposite the wind above the stadium?

Question

In a (American football) bowl stadium, the flags on top of the goalposts typically fly in the opposite direction of the flags above the stadium, particularly when the wind is blowing heavily. Why is that?

In: 0

Answer 1

Picture a giant waterwheel. Water going over the top of the wheel falls down one way, but the opposite side of the wheel goes the other way because that’s how spinning things work. The exact same thing is happening here, except the air itself is both the water and the wheel. Wind flowing over the top of the stadium pushes the wind just below it inside the stadium along in the same direction, but then that air hits the wall of the stadium. Some of it goes up, some goes down, and the air which goes down becomes the wind flowing across field height in the stadium as it turns back around to continue spinning the wheel.