Circulation Flashcards
What is the Boundary Layer?
The layer most influenced by Friction
Atmospheric Ekman pumping, spirals and flow occurs here
What is an Ekman Spiral and what causes it?
Creation of a wind spiral with height.
CAUSE: Friction. Closer to surface = increased frictional drag and obliqueness of wind across isobars
What is the surface degree of obliqueness of an Ekman Spiral over sea? Is this greater than over land?
10-20 degrees - No (land is 25-35 degrees)
What happens with increased height?
Wind gets closer to geostrophic speed
What happens in an anti-cyclone and what sort of pressure system is it?
Air descends and diverges (moves outward) in the boundary layer - high pressure.
What is the process of air movement as a result of high and low pressure systems called?
Ekman Pumping
What is convergence and where does it occur at the surface?
The inward movement of air, occurs in low pressure systems.
What direction do anti-cyclones rotate in the Northern Hemisphere?
Clockwise
How many pressure belts is the Earth’s atmospheric circulation made up of?
4
Which cells are located over the tropics?
Hadley Cells
Which model of atmospheric circulation breaks down as a result of Conservation of Angular Momentum (increase in velocity as radius decreases)?
Hadley’s Uni-Cellular Model of General Circulation
What happens to air at 30 degrees latitude?
It cools and sinks, or gets caught in Jet Streams
What are Trade Winds?
A prevailing pattern of Easterly surface winds found in the tropics. They replace rising air at 30 degrees latitude.
Which circulation cells are directly thermally driven?
Polar Cells
What are horizontal winds travelling East -> West parallel to longitude referred to as?
Zonal Components
Give 3 features of the Topics
1) Weather/climate dominated by Hadley cells and the ITCZ
2) There is zonal pressure distribution and minor Coriolis Effect
3) Inversion Zones exist
What are Inversions?
Areas whereby there is a deviation in normal atmospheric property changes with height.
What causes movement to the Equator in the Subtropics?
Coriolis Effect
Where do you find the Sub-Tropics and what tends to occur at the surface?
30 degrees latitude North and South - divergence (sub-tropical highs)
Where is the influence of the Polar Jet Stream meeting warm Southern Air most significantly felt?
The Mid Latitudes (23-66 degrees latitude)
Give 3 features of the Mid-Latitudes
1) Baroclinic geostrophic current = not just pressure determines air density
2) Pressure changes = Temperature change
3) Strong prevailing winds