Here's why:

* High pressure systems are areas where the air is denser and heavier than surrounding air.

* Air naturally wants to move from areas of high pressure to areas of low pressure.

* The Coriolis effect, caused by the Earth's rotation, deflects moving objects (like air) to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

These factors combined create the characteristic clockwise (Northern Hemisphere) and counterclockwise (Southern Hemisphere) rotation of air in high-pressure systems.