Wind systems exist because differences in temperature and air pressure create moving air. With equal temperature and pressure all over the surface, there would be no global wind systems.
The air in the Earth’s atmosphere moves from high pressure to low pressure. On a rotating body such as the Earth, the air turns to the right—counterclockwise—in the Northern Hemisphere and to the left—clockwise—in the Southern Hemisphere.
Earth’s orbit around the sun and its rotation on a tilted axis causes some parts of Earth to receive more solar radiation than others. This uneven heating produces global circulation patterns.
For example, the abundance of energy reaching the equator produces hot humid air that rises high into the atmosphere. A low pressure area forms at the surface and a region of clouds forms at altitude. The air eventually stops rising and spreads north and south towards the Earth's poles. About 2000 miles from the equator, the air falls back to Earth's surface blowing towards the pole and back to the equator. Six of these large convection currents cover the Earth from pole to pole.
These global wind patterns drive large bodies of air called air masses. Air masses are thousands of feet thick and extend across large areas of the Earth. The location over which an air mass forms will determine its characteristics.
See links below to learn more about weather systems and patterns:
www.noaa.gov
enviroliteracy.org
earthguide.ucsd.edu