atmosphere and ocean circulation

Question 1

waht is frequency?

Answer 1

Frequency= 2 w sin latitude parameter w is the angular velocity of the earths rotation V is speed , m is mass of current or object

Question 2

what is vorticity?

Answer 2

Vorticity: the “spin” or rotation of a parcel of water or air. Like the Coriolis force the vorticity is zero at the equator and maximum at the poles.

Question 3

what are the types of vorticity?

Answer 3

Planetary vorticity- vector that is parallel to axis of earth’s rotation magnitude. Everything on earth, including the ocean and atmosphere rotate with it, so are subjective to planetary vorticity. Use the Coriolis parameter

Question 4

what is relative vorticity?

Answer 4

Stirring a barrel or bear will impart an additional rotation in the beer relative to the earth. This is known a relative vorticity. Spin on a spin, additional spin. This additional spin is called the relative vorticity.

Question 5

what is absolute vorticity?

Answer 5

Absolute vorticity: sum of relative and planetary

Question 6

what is potential vorticity?

Answer 6

Potential vorticity: rate of rotation of a fluid column will change as the height of the column changes.

Question 7

how does the fliud affect the rotating earth?

Answer 7

Fluid flow on a rotating earth: increased spin. If thinner, increase the spin, like a iceskater.
Rate of rotation of a fluid column will change as the height of the column changes.

Question 8

what is the conservation of potential vorticity?

Answer 8

Conservation of potential vorticity: this covers change in depth and height, in relative vorticity and in latitude. Parcel retains rotation it has near the pole, so appears to rotate counter-clockwise. If a column of air or water moves equatorward, frequency decreases, so the spin must increase.

Question 9

what is the rossby radius?

Answer 9

the critical length at which the Coriois force becomes important.

Question 10

what is the Rossby?

Answer 10

ratio of the inertial force to the Coriolis force.
Ratio of the inertial force to the Coriolis force. A measure of the relative importance of these forces.
Ro= U/Lf
Velocity/ length scale x Coriolis parameter
For high rossby numbers, the effects of planetary rotation can be ignored. For small numbers, the effects of the planetary rotations dominate.

Question 11

what dominates wind driven circulation?

Answer 11

trade winds and the westerlies

Question 12

what is the Ekman spiral and Ekman layer?

Answer 12

• The Ekman spiral and Ekman layer processes- divergence and convergence, upwelling zones, geostrophic currents and ocean gyres.

Question 13

what are the 3 categories of sea water motion?

Answer 13

waves, tides, ocean circulation

Question 14

what is water mass?

Answer 14

Volumes of water that have the same properties (salinity, temperature etc) are called WATER MASS
Water masses are transported via ocean currents

Question 15

how are water masses separated?

Answer 15

Distinct water masses are usually separated by different densities, so flow over each other in layer along density interface
As water masses flow past each other, slow mixing occur by diffusion (as its not very good), may be enhanced by turbulence and activity of eddies, this mixing increases as relative speed between layers increase
Vertical motions of water masses take place by convection as densities change

Question 16

what are surface currents and baroclinic?

Answer 16

ften called “wind-driven currents”
Winds are the primary direct energy source for currents that flow horizontally in the ocean surface layers.
When lower levels move in different directions the situation is said to be “baroclinic”. This is if it only affects the waters and surface waters

Question 17

what is barotropic?

Answer 17

Western boundary currents, and the Antarctic circumpolar current, may affect flow from the surface to the sea floor, moving in the same direction, this situation is said to be “barotropic”. When the surface current goes right down t the sea bed. Eg gulf streams.

Question 18

what are the wind driven circulation inclusions?

Answer 18

1. The frictional wind-drive currents of the thin surface layers (50-100 meters) - the frictional Ekman layer. The surface part of the ocean which is directly affected by the wind. Direct
   
   2. The part of the geostrophic flow from the surface to the ocean bottom which is driven, indirectly, by the wind stress. Indirect

Question 19

what is deep water circulation (thermohaline circulation)?

Answer 19

Movement of water masse sin the deep layers of the oceans are caused by differences in the density of the water masses controlled by temperature and salinity variation.

Question 20

what is pycnocline?

Answer 20

Gradients in properties. Creates interface pycnocline. At low and mid latitudes get permanent pycnocline. At mid and temperate latitudes, strong summer heating creates a seasonal thermocline, that separates a mixed later from a deep layer.

Question 21

what is langmuir circulation?

Answer 21

as the rings get stronger, the wind gets stronger. Streaks near a oil thing in the sea, are because of the bubbles causing lines in the water.

Question 22

what is the generation of currents?

Answer 22

When the wind blows across the ocean surface, energy is transferred from the wind to the surface water
The surface layer of the water is set in motion, the surface layer transfers its kinetic energy downwards progressively from layer to layer by friction.

Question 23

why do currents continue?

Answer 23

Once current motion has been started, it will continue after the wind stops blowing because the water has momentum. Currents created by winds can flow from long after the winds stop because:

Question 24

why does the sea surface slope when the wind stops?

Answer 24

The frictional forces between moving layers of water is small and while they blow, wind causes the sea surface to be sloped and the slope remains when the wind stops blowing.

Question 25

how does a horizontal pressure gradient form?

Answer 25

Under the sloped sea surface, a horizontal pressure gradient forms
The pressure gradient causes the water to flow from high to low pressure to restore the surface to a flat horizontal plane. These flows are detected by the Coriolis effect

Question 26

Once set in motion, the direction and speed of any current are modified by friction and what three other factors?

Answer 26

1. Deflection by the Coriolis effect
   
   2. Blocking and deflection of current flow by coasts
   3. The presence of horizontal pressure gradient.

Question 27

what did Nansen find on his exhibition in 1890s?

Answer 27

Fridtjof Nansen, on his artic expedition in the 1890s, noticed that drifting ice did not move in the direction of the wind. Instead, it moved in a direction of about 20 degrees to 40, to right of the wind.

Question 28

why doesnt the surface current differ from the direction of the wind?

Answer 28

The surface current that carried drifting ice does not flow in the direction of the wind because it is deflected by the Coriolis effect. Icebergs don’t move in the same direction to the wind.

Question 29

how does each layer of water drive the layer below?

Answer 29

The surface water set in motion, the water below it, and each layer sets the layer below in motion. Each layer of water is driven by the layer above. The speed decreases with depth, and the direction of flow of each layer is deflected by the Coriolis effect.
Fully formed only under ideal conditions (wind must blow at constant speed for a day or 2 and water depth must not be shallow).

Question 30

what is the speed of the Ekman layer?

Answer 30

At the base of Ekman layer, the current speed is about 4% of the surface current speed.

Question 31

what does Ekamans theory predict about the surface laters?

Answer 31

Ekman’s theory predicts the surface layer will flow at 45 degrees to the wind. Under normal conditions, deflection less and the spiral not fully developed.

Question 32

what is a permanent pycnocline?

Answer 32

Permanent pycnocline- in low and mid-latitudes in the open ocean a permanent pycnocline is present with upper boundaries usually at depths of 100-150 m.

Question 33

what is divergence?

Answer 33

Divergence: upwelling- convergence: downwelling. Northern hemisphere- variations in an eastward wind. Ekman transport is southward, to the right of the wind. When wind is blowing, its strongest in the middle and weakest at the side. The deflection increases. Water has to come in to fill the gap. This is divergence.

Question 34

what is equatorial upwelling?

Answer 34

Equatorial upwelling: trade winds cause flow to north in N hem, and flow to the south in a S. Hem. This results in divergence and upwelling. If they crash into each other, it causes convergence.

Question 35

what does equatorial upwelling generate?

Answer 35

Equatorial upwelling: generates equatorial cold tongue. Trade winds coming down, they result in divergence, deflection to the right etc. Along the equator, there will be upwelling.

Question 36

what is coastal upwelling?

Answer 36

Coastal upwelling is if the wind is away from the coast. If wind is near coast, downwelling causes Ekman to go away from the shore.
Coastal upwelling of nutrients generated high productivity.

Question 37

what is geostrophic flow?

Answer 37

Geostrophic flow: works for ocean currents and wind flow. When flow is initiated on a horizontal pressure gradient, flow is deflected by the Coriolis effect. The flow is progressively deflected by Coriolis effect until the flow is aligned across the gradient, with the pressure gradient force balanced by the Coriolis effect.

Question 38

what are geostrophic currents?

Answer 38

Geostrophic currents- the larger the slope, the stronger the current. When these forces balance each other, we say we have a geostrophic balance. Currents on a “aqua planet”: circum-global geostrophic current would flow. From eat to west under the Hadley cells on each side of the equator, from the west to east at mid latitudes.

Question 39

where are geostropic gyres?

Answer 39

On present earth, continents block the E-W and W-E currents, (except around Antarctica), so they are deflected to form geostrophic gyres.

Question 40

Indian monsoon

Answer 40

SW monsoon winds drive coastal upwelling off Somalia and Oman. Upwelling of nutrients generates high productivity as seem in SeaWifs chlorophyll a.
The african monsoon:
Max rainfall coincides with lowest outgoing longwave radiation OLR due to convection and clouds.

Question 41

what are ocean eddies?

Answer 41

• Small whirlpools.
  
  • Form due to instabilities, eg a shear between different water masses
  • Spin off strong currents eg gulf stream
  • Ocean eddies with radius 10-500 km are called mesoscale eddies
  • Persist on timescale of says to moths, rotate every 10-30 days

Question 42

what are ocean eddies associated with?

Answer 42

• May be associated with upwelling or downwelling

Question 43

what does ocean eddies transport?

Answer 43

• Transport properties, heat, salt, pollutants, debris

Question 44

what is the Agulhas retroflection?

Answer 44

The Agulhas current is forced back or “retroflected” due to shear with the powerful Antartic Circumpolar Current ACC.
Suppresses important return of salt water to the Atlantic. But some do get through- as eddies.
Detached like an abandoned meander.

Question 45

what is the role of eddies?

Answer 45

Agulhas leakage adverts warm, saline waters into Atlantic, mainly though Agulhas rings. This is important for deep thermohaline circulation.
Eddies are so tightly surrounded by water paths that nothing can escape.

Question 46

what have scientists found about eddies?

Answer 46

Scientist have found taht they are mathematically equivalent to black holes. The findings may help explain the spread of pollution in the worlds oceans. It could also help better determine how eddies effect ocean temperatures.

Question 47

what is Ekman transport?

Answer 47

Ekman transport- mean movement of water over all depths within the wind-driven layer is 90 degrees to the wind under ideal conditions.

Question 48

where is coastal upwelling and downwelling?

Answer 48

Coastal upwelling and downwelling- northern hemisphere. Along shore winds drive offshore flow, causes upwelling along coat, and upwelling speeds of 5-10 m per day. Sources of U.W eater, nutrient rich so fuels production.