Coriolis effect

Notice in the diagram below winds are deflected in a clockwise direction in the northern hemisphere, and anticlockwise in the southern hemisphere. This is due to the fact that the Earth is spinning and will, through angular momentum, deflect winds travelling from north to south or vice versa. These deflections, establish the global wind patterns at various latitudes. Between the Equator and 30° N and S, global winds are to the east. These are known as the North and South Trade Winds. Between latitudes 30° and 60°, global winds are to the west and are known as the Westerlies. Finally at the polar latitudes, winds again blow to the east and are called the Polar Easterlies.