General Circulation Flashcards
Explain what is meant by general circulation
Large-scale pattern of pressure systems and winds which endure throughout the year.
Factors that control transfer of heat around the world are constant angular momentum and vertical/horizontal circulations.
Explain why polar highs exist
Air cools down and contracts at the poles. Increases pressure at surface creating a polar high
Explain why polar easterlies exist
Coriolis force bends wind to the left in the Southern Hemisphere. Wind flowing out from a high is anticlockwise for this reason and creates the polar easterlies to the north of them.
Explain why polar lows exist
Air becomes warmer as it moves away from the poles and starts to rise.
Creates surface polar lows at 60ºN/S
Explain why polar fronts exist
Formed when colder polar air meets warmer sub-tropical air. Mixes around a low and creates warm and cold fronts.
Explain why mid-latitude westerlies exist
Coriolis force from the mid-latitude highs rotate anti-clockwise, causes winds to be westerlies to the south of them
Explain why mid-latitude anticyclones exist
Upper air flows outward from equator towards poles and temperate latitudes toward equator.
This creates excess of air at the tropopause in subtropical regions which is forced to descend.
Creating the subtropical high pressure systems which are permanent features over the subtropical oceans at 30ºN/S
Explain why sub-tropical trade winds exist
Caused by Coriolis effect deflecting air from high, north of the high becomes a SE in the Southern Hemisphere.
The reason its not a complete easterly wind is because coriolis effect reduces towards the equator.
Explain why equatorial troughs exist.
Air is very warm at equator surface and rises. Reduces pressure at the surface creating low pressure systems.
Trade winds converging from north and south of equator also force air to rise as it meets creating narrow band of intense convection
