atmospheric and oceanic circulation

Question 1

4 steps in the global transfer of energy

Answer 1

Energy is transferred vertically between the atmosphere and the Earth’s surface, and is also transferred between the equator and the poles

Areas north and south of latitude 38 degrees receive less solar energy than areas between latitudes 38 degrees N and 38 degrees S

In the polar latitudes, more energy is emitted from the surface than is absorbed. Near the tropics more energy is absorbed by the surface than is emitted by it, leading to the deficit in solar energy north and south of latitudes 38 degrees and a surplus of energy in areas between 38 degrees north and 38 degrees south

Atmospheric circulation prevents areas near the tropics from becoming hotter while those further north and south becoming colder through the transfer of energy from the surplus to areas of deficit.

Question 2

atmospheric circulation

Answer 2

Hadley cell:
Warm air rises at the equator and travels to around 30º North where it cools and sinks to the surface, before returning to the tropics.

There is an area of low pressure at the equator, due to the rising and expanding air. At around 30º North the sinking air creates an area of high pressure. This cell is thermally direct.

Ferrel cell:
Found between the Hadley and Polar cells and lies between 60º North and 30º North.

Thermally indirect cell as it is powered by the other two cells.

In reality the effect of depressions and jet streams disrupts the Ferrel cell.

Polar cell:
Much smaller and is thermally direct.

Cold air sinks at the North Pole, before flowing south at the surface.

Here it is warmed by contact with land/ocean around 60º North, where it rises.

Question 3

oceanic circulation

Answer 3

Currents do not flow directly in the direction of the density gradient, but rather flow in circular loops or gyres.

These are spiral oceanic surface currents and are found in both the Northern and Southern Hemispheres.

The main subtropical gyres flow clockwise in the Northern Hemisphere and anti-clockwise in the Southern Hemisphere which have strong, warm, polewards flows concentrated in the western edges of each ocean.

The coriolis effect prevents the flows going directly down the gradients that drive them.

It is strong in most areas, as oceans are very large and timescales of the currents are very long.

It acts equally whichever direction the current is moving in, but is weak near the equator where there is a shift from currents being deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.