Atmospheric Circulation And Weather Systems. Atmospheric pressure, vertical variation pressure, horizontal distribution of pressure, world distribution of sea level pressure, factors affecting the velocity and direction of wind( pressure gradient force, frictional force, carioles force, pressure and wind, ) general circulation of the atmosphere, ENSO seasonal wind, local winds land and sea breezes mountain and valley winds, air masses , fronts, exratropical cyclone tropical cyclones, thunderstorms, tornadoes.