12.1 Modes of Heat Transfer

To understand the surface energy balance, we need to understand the three fundamental modes of heat transfer:

• radiation,
• conduction, and
• convection.

Radiation is the emission or transfer of energy in the form of electromagnetic waves or particles. Conduction is heat transfer due to the random thermal motion of the molecules and particles within a system. Convection is heat transfer due to bulk fluid motion. Each of these modes plays an important role in the energy balance of the land surface. In the surface energy balance, the energy flux via radiation is often the largest single term, so we will consider this mode of heat transfer first.