As a first hint to this page's topic, read the Research results of the Fenizic Royal Meteorological Institute.
Explanation: The bigger land masses of the "summer" hemisphere are extremely heated up by the sun, resulting in low-pressure systems (marked by "L") as warm air is lighter than cold air, tends to lift itself up and reduces air pressure on the ground. The bigger water bodies of the "winter" hemisphere store the heat more than the land masses, making them relatively warmer than the land, also resulting in low-pressure systems, while the land masses cool the air down which produces high-pressure systems ("H"). - The polar regions are permanent low-pressure systems. In high-pressure systems, the winds are circling clockwise on the northern hemisphere, counter-clockwise on the southern hemisphere. The same, but in opposite direction, applies to low-pressure systems.