How is the atmosphere heated?

Earths atmosphere is heated up because of the following three important processes. They are

• Conduction: It is a process in which heat flows from objects with higher temperatures to objects with lower temperatures. The air in contact with the land gets heated gradually and the upper layers in touch with the lower layers also get heated. 
• Convection: Vertical heating of the atmosphere is known as convection. The air in contact with the earth upsurges vertically on heating in the form of currents and transfers the heat of the atmosphere.
• Advection: The transfer of heat through the horizontal movement of air is called advection. 

Further Reading:

• Heating And Cooling Of The Atmosphere
• Geography Notes