Atmosphere

Question 1

Energy distribution

Answer 1

1. Due to the curvature of the Earth, in the tropics the sun’s rays are concentrated on a much smaller area, resulting in more intense heating.
2. Rays have less atmosphere to pass through at the tropics, so less energy is lost through absorption and reflection.
3. Albedo is the reflectiveness of the land surface. Darker forest surfaces at the tropics, have a lower albedo so absorb more energy in contrast with lighter snow/ice covered areas at the poles.
4. Due to the tilt of the Earth, limited insolation is received at the Poles in winter, whereas tropical areas receive insolation all year round.

Question 2

Patterns of ocean currents in the North Atlantic

Answer 2

1. Currents follow loops or gyres
2. They move clockwise in the Northern Atlantic
3. Warm currents travel from the equator towards the Poles
4. Eg. The North Atlantic Drift
5. Cold currents return cool water from the poles
6. Eg. The Labrador.

Question 3

Explain how ocean currents redistribute energy across the globe

Answer 3

1. Ocean currents are greatly influenced by the prevailing winds with energy being transferred by friction to the ocean currents.
2. Land masses like North America divert ocean currents.
3. Due to differential heating and/or salinity, density differences occur in water which result in in chilled polar water sinking, spreading towards the Equator and displacing warm water pole wards.
4. The Coriolis effect deflects currents to the right in the Northern Hemisphere.

Question 4

Explain atmospheric circulation

Answer 4

1. Winds are deflected to the right due to the Coriolis Effect which is caused by the spinning of the Earth.
2. Warm air is distributed to higher / cooler latitudes and cold air is distributed to lower/warmer latitudes.
3. The Hadley/Polar Cells are thermally direct and the Ferrel Cell is thermally indirect.
   Hadley cell:
4. Warm air rises at the Equator creating low pressure.
5. The air splits in the atmosphere and moves towards the poles.
6. Air cools and sinks at the Tropics / 30o creating high pressure.
7. The North East Trade winds move air back to the Equator completing the Hadley cell.
   Polar cell:
8. Cold air sinking at the poles creates a high pressure area.
9. The Polar Easterlies transfer cold air from the poles to the Polar front/towards the Equator.
10. Here it meets warmer air from the tropics, causing air to rise.
11. Air moves back to the Poles in the upper atmosphere completing the Polar Cell.
    Ferrel cell:
12. The Ferrel cell is located between 30oN and 60oN.
13. The Ferrel cell transfers air between the Hadley and Polar cells forming the westerlies.

Question 5

Describe the origin and characteristics of the ICTZ

Answer 5

Maritime tropical (mT):
* Origin ― Atlantic Ocean/Gulf of Guinea
* Weather characteristics ― warm/hot, unstable air with high humidity, high precipitation.

Continental tropical (cT):
* Origin ― Sahara Desert
* Weather characteristics ― hotter/very hot, low precipitation, stable air with low humidity.
* Poor visibility caused by dust carried from the desert.

Question 6

Suggest reasons for differences in the ICTZ

Answer 6

1. The ITCZ is an area of low pressure where the trade winds/air masses meet
2. The maritime airmass is pushed up, cooling and codensing to form clouds
3. Twin precipitation peaks can be attributed to the ITCZ moving northwards in the early part of the year and then southwards later in the year in line with the thermal equator/overhead sun.
4. Coastal cities are influenced by the wet mT air for most of the year.
5. Inland cities are under the influence of the dry cT air for most of the year.