Physics of Air

Convection is the transfer of heat from a warmer area to a cooler area by the movement of a fluid (liquid or gas) from the warmer area to the cooler one. An example of convection is steam from a cup of hot coffee sitting in a room. The air near the coffee is heated by the coffee; the steam rises from the coffee into the cooler air farther away from the coffee. (The coffee making the air directly above it hot is an example of conduction; the loss of heat through the cup is an example of radiation.) Another example of convection is a boiling pot of water. The heat under the pan causes the water at the bottom to become hot; this water rises toward the top which is cooler, causing bubbles. When thinking about the convection in the atmosphere, it's important to understand two things: hot air rises, and air moves from areas of lower pressure to areas of higher pressure. These things are connected: when hot air rises, it leaves an area of lower pressure; higher pressure air will fill the area of lower pressure. Therefore, if one region of air is warmed (for instance, by warm ocean water), the air will rise, air around that region will fill the low-pressure region, causing wind.