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Climate Systems > Circulation > Flashcards

Circulation Flashcards

1
Q

What is the Boundary Layer?

A

The layer most influenced by Friction

Atmospheric Ekman pumping, spirals and flow occurs here

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2
Q

What is an Ekman Spiral and what causes it?

A

Creation of a wind spiral with height.

CAUSE: Friction. Closer to surface = increased frictional drag and obliqueness of wind across isobars

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3
Q

What is the surface degree of obliqueness of an Ekman Spiral over sea? Is this greater than over land?

A

10-20 degrees - No (land is 25-35 degrees)

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4
Q

What happens with increased height?

A

Wind gets closer to geostrophic speed

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5
Q

What happens in an anti-cyclone and what sort of pressure system is it?

A

Air descends and diverges (moves outward) in the boundary layer - high pressure.

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6
Q

What is the process of air movement as a result of high and low pressure systems called?

A

Ekman Pumping

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7
Q

What is convergence and where does it occur at the surface?

A

The inward movement of air, occurs in low pressure systems.

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8
Q

What direction do anti-cyclones rotate in the Northern Hemisphere?

A

Clockwise

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9
Q

How many pressure belts is the Earth’s atmospheric circulation made up of?

A

4

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10
Q

Which cells are located over the tropics?

A

Hadley Cells

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11
Q

Which model of atmospheric circulation breaks down as a result of Conservation of Angular Momentum (increase in velocity as radius decreases)?

A

Hadley’s Uni-Cellular Model of General Circulation

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12
Q

What happens to air at 30 degrees latitude?

A

It cools and sinks, or gets caught in Jet Streams

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13
Q

What are Trade Winds?

A

A prevailing pattern of Easterly surface winds found in the tropics. They replace rising air at 30 degrees latitude.

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14
Q

Which circulation cells are directly thermally driven?

A

Polar Cells

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15
Q

What are horizontal winds travelling East -> West parallel to longitude referred to as?

A

Zonal Components

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16
Q

Give 3 features of the Topics

A

1) Weather/climate dominated by Hadley cells and the ITCZ
2) There is zonal pressure distribution and minor Coriolis Effect
3) Inversion Zones exist

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17
Q

What are Inversions?

A

Areas whereby there is a deviation in normal atmospheric property changes with height.

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18
Q

What causes movement to the Equator in the Subtropics?

A

Coriolis Effect

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19
Q

Where do you find the Sub-Tropics and what tends to occur at the surface?

A

30 degrees latitude North and South - divergence (sub-tropical highs)

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20
Q

Where is the influence of the Polar Jet Stream meeting warm Southern Air most significantly felt?

A

The Mid Latitudes (23-66 degrees latitude)

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21
Q

Give 3 features of the Mid-Latitudes

A

1) Baroclinic geostrophic current = not just pressure determines air density
2) Pressure changes = Temperature change
3) Strong prevailing winds

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22
Q

What are fast flowing, meandering air currents, caused by temperature differences between Tropical & Polar air masses called?

A

Jet Streams

23
Q

2 Types of Jet Stream:

A

1) Polar (strongest)

2) Subtropical (weaker)

24
Q

Which type of jet stream is the boundary between Mid-Latitude and Equatorial air?

A

Sub-Tropical

25
Q

Give 3 features of the Polar Regions

A

1) Very strong katabatic winds
2) Responsible for meridional (N->S) flow
3) Arid, thermally driven cells with descending air (divergence)

26
Q

What is the ITCZ?

A

A region of strong convective activity at the Equator - where NH and SH trade winds meet.

27
Q

What has greater seasonal temperature differences than ocean regions?

A

Continental regions

28
Q

What land masses have increased pressure in winter and decreased pressure in summer? Give examples.

A

Large, mid-latitude land masses - eg. North America and Eurasia)

29
Q

What does low pressure in summers over large, mid-latitude land masses cause?

A

A cyclonic system: strong inflow of air (convergence) in Summer blowing wind ocean-> land. Thus a warm and moist summer monsoon.

30
Q

What sort of air flow occurs in winter over large, mid-latitude land masses, and what does it cause?

A

Outflow - an anti-cyclone develops due to divergence. Wind blows land -> ocean, so winter monsoon is dry & cool

31
Q

What is Vorticity and what are the 3 elements of this concept?

A

The rotation/angular velocity of particles in a system.

1) Magnitude
2) Direction
3) Sense of Rotation (positive vorticity = anticlockwise)

32
Q

What does Vertical Positive Vorticity cause?

A

Upper level divergence in the Positive Vorticity Advection region - thus rising air (cyclone)

33
Q

What is the sum of a parcel about its own axis (SHEAR), rotation of a parcel about the axis of a pressure system (CURVATURE) and rotation due to atmospheric motion (CORIOLIS) referred to?

A

Absolute Vorticity

34
Q

At what temperature is pure water most dense?

A

4 degrees Celcius

35
Q

What is the salinity of standard ocean water?

A

35ppt - 3.5%

36
Q

Ocean Circulation is driven by what 2 ‘engines’?

A

1) Thermohaline Circulation

2) Wind-Driven Surface Circulation

37
Q

What happens if the wind blows in the same direction for a prolonged duration?

A

Local surface currents are created.

38
Q

What is Ekman Transport and what does it cause?

A

The net transport of water due to coupling between wind and surface waters - causes NET water movement at 90 degrees to wind direction

39
Q

At what point does influence of wind on ocean circulation cease?

A

100-150m

40
Q

As a result of the Coriolis Effect acting to the Right in the NH, at what angle does the surface water current move in relation to wind direction?

A

45 degrees - this increases with depth as Coriolis effect has longer to act

41
Q

How is Ekman Spiral different to Ekman Transport?

A

An Ekman Spiral is the result of the Coriolis effect acting upon the ocean surface in addition to Wind - Ekman Transport is purely the result of Wind Direction.

42
Q

What do variations in sea surface height (caused by Ekman Transport) cause?

A

Pressure gradients & Geostrophic Flow at Gyre centres

43
Q

What is Ekman Pumping?

A

Downwelling of water due to pressure/density gradients in the vertical water column

44
Q

What direction does Ekman Transport move water in relation to the coast and what process is associated with this?

A

Away - Upwelling

45
Q

Where is upwelling most common?

A

On the West coasts of continents

46
Q

Which is worse for biological productivity: Upwelling or Downwelling?

A

Downwelling

47
Q

What drives ocean gyres?

A

1) Balance between pressure gradients caused by elevations

2) depressions of sea surface caused by Ekman Transport and Coriolis Effect

48
Q

Where do Sub-Tropical gyres sit?

A

Below areas of high pressure

49
Q

What controls Thermohaline Circulation, and what drives it?

A

Temperature and Salinity - driven by high-latitude cooling

50
Q

What forms at 60 degrees latitude?

A

Deep Water

51
Q

What percentage of the Moon’s tide-generating force does the Sun have?

A

46%

52
Q

What is longer: Solar or Tidal day? What does this mean?

A

Tidal Day (24 hours and 50 minutes) - so times of high tide change by 50 mins from one day to the next.

53
Q

How long does it take for the Moon to orbit Earth?

A

29.5 days

54
Q

Where are most intense currents found?

A

Equatorial Zone, Eastern Japanese Coasts, North America and South Africa.

Climate Systems (3 decks)

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