The General Atmospheric Circulation

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  • Created by: OctaviaL
  • Created on: 29-05-16 13:01
What is general atmospheric circulation?
The pattern of wind and pressure belts within the atmosphere. The circulation is complex but certain movements occur regularly enough for us to recognise pattens of air pressure, distribution and winds.
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What does the Tri-cellular model show?
How energy is redistrubuted across the globe.
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What are the three cells?
Hadley, Ferrel, Polar
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Where are each of the cells found?
Hadley: 0-30 N/S. Ferrel: 30-60 N/S. Polar: 60-90 N/S.
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Where are the westerlies found?
Ferrel cell.
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Where are trade winds found?
Hadley cell.
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What are the Hadley Cells responisble for?
Seasonal changes in climate of tropical regions that experience a wet and dry climate.
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What is the ITCZ?
Inter-tropical convergence zone = an area of low pressure in equatorial latitudes.
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What happens at the ITCZ?
The ground heats rapidly by day and there is much surface evaporation. As the hot air rises in convection currents, an area of low pressure develops. The rising air cools and water vapour condenses leading to heavy rainfall.
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What is the Coriolis effect?
The deflection of winds due to the rotation of the Earth.
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Where and why are sub-tropical anticylones formed?
At 30 N/S where colder air sinks and warms so residual moisture evaporates to create an area of high pressure at the surface.
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What are trade winds?
Air returning towards the equatorial regions, subject to the coriolis effect.
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What are the Ferrel cells responsible for?
Climate types in the mid-latitudes.
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What happens at 60 N/S?
The westerlies that have been pulled across the surface, picking up moisture from oceans meet cold air from the poles. The warmer tropical air is lighter than the cold, dense polar air so rises.
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Why are there unstable conditions at 60 N/S?
Uplift from the rising tropical air creates low pressure. The unstable condition are characteristically experienced in the cold temperate western maritime climate.
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What occurs in the Polar Cells?
Winds are pulled from the poles to low pressure at 60. The coriolis effect means winds are deflected right in the Northern hemisphere and left in the Southern. So cold air is transported away from the poles and warm air brought in by the Polar cells.
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What did Rossby do?
Refined the tricellular model in 1941 to take into account the influence of depressions/anticyclones and high level jet streams in the redistribution of energy.
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What are Rossby waves?
A series of large waves that occur in the westerlies in the mid-latitudes in both the northern and southern hemispheres. They occur 4-6 times in each hemisphere and stretch from the poles to the tropics.
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Why do Rossby waves exist?
Unknown but some believe they are caused by air flow being forced to divert around N-S mountain ranges of Rockies and Andes.
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What is a jet stream?
A narrow belt of fast moving air at an average altitude of 10km. They can be hundreds of kms wide but just 1-2km vertically.
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What are jet streams a product of?
A large temperature gradient.
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Where is the Polar Front Jet Stream?
40-60 N/S between the Polar and Ferrel cells. It helps to explain the formation of depressions.
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Where is the Subtropical Jet Stream found?
25 N, 35 S.
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What happens to the Subtropical Jet Stream in summer?
Over West Africa and Southern India may become easterly due to higher temperatures over land than sea.
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Card 2

Front

What does the Tri-cellular model show?

Back

How energy is redistrubuted across the globe.

Card 3

Front

What are the three cells?

Back

Preview of the front of card 3

Card 4

Front

Where are each of the cells found?

Back

Preview of the front of card 4

Card 5

Front

Where are the westerlies found?

Back

Preview of the front of card 5
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