Then variation of Earth's surface also alters global and regional air circulation. This process is called convection . As the equatorial air rises, air at low latitudes and from higher latitudes in both hemispheres moves toward the equator to take its place. This flow is balanced by a flow way from the equator at higher altitudes. While flowing poleward, the upper air cools by radiation to space.
Convection is the process by which heat is carried upwards by a moving mass of air or liquids.
Convection is the main process responsible for upward movement of air in the troposphere. There are many familiar examples of convection. A radiator heats cool air. The air expands, becomes less dense and rises, displacing cooler air which sinks and enters the radiator at its base to complete the convection cycle. A pot of water placed on a stove is heated from below.