12.2 NOTES: Weather Systems

Convection, driven by uneven heating & the diurnal cycle, assures that equilibrium will never be reached, thus weather will always change!

Main Idea 1

Temperature: Cold

Pressure: High

Air flowAir sinks, creating a high-pressure zone below that moves toward the equator in an attempt to reach equilibrium.

Pole Surface Air

Temperature: warm

Pressure: low

Air flow:Air rises, creating a high-pressure zone above that moves toward the poles in an attempt to reach equilibrium.

Equator Surface Air

Earth’s rotation “drags” the atmosphere; results in the Coriolis effect. The Coriolis Effect causes massive variation in global airflow patterns.

Main idea 2

Describe:Earth’s rotation causes N. Hemisphere winds to diverge to the right of original path. In the S. Hemisphere, winds bend to the left. Creates convection cells.

Coriolis Effect results in convection cells

Each hemisphere has 3 cells in which air circulates through the entire depth of the troposphere: -Polar Cells-Ferrel Cells -Hadley Cells

Describe:Air rises & travels towards Poles (due to

CE). Once over Poles, air cools more & sinks, forming the polar highs. At the surface, air diverges outward from the polar highs. Surface winds in the polar cell are called Polar Easterlies.

Polar cells form a band around the planet near the N & S Poles.

Polar Cells

Describe:A mid-latitude cell where the air flows towards poles & eastward near the surface & towards equator & westward at higher levels.The Ferrel Cells form a band around the planet between Poles & Horse Latitudes.

Ferrel Cells

(FYI: Horse latitudes (30o N & S of Equator) are generally areas of high pressure marked by calm, subsiding air that gets heated during descent. It is said that Spanish sailors ferrying horses to the West Indies were usually stuck for months in these calm waters and had to throw their horses into the water to conserve drinking water for themselves. This led to the term 'horse latitudes'.)

Describe:As warm air moves towards poles, it bends b/c of Coriolis Effect. It cools, loses its push, & heads back towards Equator. The Hadley Cells form a band around the planet b/w Equator& Horse Lats.

Hadley Cells

Defined by:Wind is always defined based on the direction from which it is coming.

Major Wind Systems

Skip main idea #3

Describe:The ground winds of the Polar Cell that blow from Polar regions to Subpolar Lows. They are deflected by Coriolis Effect towards the west.

Polar Easterlies

Describe:The ground winds of Ferrel Cells that blow from the horse latitudes to the sub polar lows. They are deflected by Coriolis Effect, but bend toward the east b/c they start blowing in the opposite direction.

Westerlies

Describe:Ground winds of Hadley Cells that blow from horse latitudes towards Equator & are deflected by Coriolis Effect toward the west.

Trade Winds (named for trade shipping)

(intertropical convergence zone)Describe:The quiet, still region near Equator where the trade winds converge & air is rising.

Doldrums (“Dull”-don’t get stuck here!)

Effects:Powerful air movements can be created!!! WAAA HAAA HAAAA

When wind systems collide

Describe:A river of fast moving W to E air, high above the surface of Earth (along the polar front).

Temperature Change effects:Jet stream moves faster in the winter b/c temperature differences are much greater b/w the warm Westerlies & Polar Air.

Polar Jet stream

(intertropical convergence zone)Describe:Weaker than Polar Jet Stream & roughly follows the horse latitudes (30 degrees N & 30 degrees S)

Subtropical Jet Stream