General Circulation

Primary Role of General Circulation

To transport excess heat from the equator to the poles

Hadley Cell

Circulation occurring at low latitudes from the Equator to 30 degrees

Ferrel Cell

Atmospheric circulation cell occurring at mid-latitudes

Polar Cell

Atmospheric circulation cell occurring at high latitudes

Hadley Cell Mechanism

Equatorial heating causes expansion

upper level flow away from equator

sinking in subtropics

Jet Streams

Narrow bands of fast winds in the upper troposphere at roughly 10km altitude

Polar Front Jet (PFJ)

Forms at the boundary of cold polar air and warm subtropical air; influences mid-latitude weather

Subtropical Jet STJ

Forms where Hadley and Ferrel cells meet; driven by conservation of angular momentum

Thermal Wind Balance

Explains why winds increase with height where there are strong temperature gradients

Vorticity

A measure of spinniness about an axis

Rossby Waves

Planetary waves influenced by conservation of absolute vorticity and orographic barriers

Internal Sensible Energy

Energy stored within atoms or molecules; makes up about 70 percent of atmospheric energy

Potential Energy

Energy of position based on altitude and gravity; makes up about 27 percent of atmospheric energy

Kinetic Energy

Energy of motion; makes up only about 0.05 percent of total atmospheric energy

Angular Momentum Conservation

Easterly trades gain momentum in tropics; Westerlies transfer it back to Earth

North Atlantic Oscillation (NAO)

A seesaw in atmospheric pressure between the Azores High and Icelandic Low

NAO Positive Phase

Stronger pressure gradient; strong westerlies; warm and wet Northern Europe

NAO Negative Phase

Weaker pressure gradient; meridional flow; cold and dry UK winters

Southern Annular Mode (SAM)

Involves north-south movements of the westerlies and storm tracks in the Southern Hemisphere

SAM Positive Phase

Westerlies strengthen and pull tighter around Antarctica