Convection, from the Latin /con/ meaning against or away, and /vect/ meaning "move," is when heat is transferred away from a mass (liquid or gas). For instance, the sunlight heats the Earth's surface, some of the heat is transferred to the air by conduction, and the heated air becomes less dense and therefore rises, carrying heat away with it. Rising heated pockets of air are called "thermals." As a thermal rises, denser cooler air sinks down and moves into the heater region. this leads to the formation of a "cell," or a region of convective circulation. The horizontally moving part of the circulation, called "wind," carries air properties with it, and the transfer of these properties is called advection. For instance, if the wind blows over a body of water it may pick up water vapor and transport it. If the air then cools the vapor may condense and advective fog may occur.
Concept Mapping Toolkit
Insitute for Human and Machine Cognition
The University of West Florida