Global Atmospheric Circulation

• The global atmospheric circulation can be described as a worldwide system of winds moving solar heat energy FROM the equator TO the poles to reach a balance in temperature

Wind formation

• Air always moves from high pressure to lower pressure, and this movement of air generates wind

• Winds are large scale movements of air due to differences in air pressure

• This pressure difference is because the Sun heats the Earth's surface unevenly

• Insolation that reaches the Earth's surface is greater at the equator than at the poles due to the Earth's curvature and angle of the Earth's tilt

Diagram showing how angle of insolation spreads solar radiation over a wider area at the poles than the equator

• Hot air rises and cooler air sinks through the process of convection

• This irregular heating of the Earth’s surface creates pressure cells

• Each cell generates different weather patterns

A typical wind pressure cell system showing distribution of pressure at Earth's surface and upper atmosphere

• Air movement within the cell is roughly circular and moves surplus heat from equatorial regions to other parts of the Earth

• In both hemispheres, heat energy transfer occurs where 3 atmospheric circulation cells meet

• These are the Hadley, Ferrel and Polar cells and are shown via the tri-cellular model:

Heat energy flow and surface winds in the tri-cellular model