Atmosphere

Question 1

Global Heat Budget

Answer 1

Sun
v100%
5% scattered by gas/ dust < 20% absorbed (17% dust/gas/water & 3% dark clouds) > 20% reflected by white clouds.
v55%
50% absorbed by earth’s dark surfaces > 5% reflected by earths white surfaces.

Question 2

Global Insolation

Answer 2

1. The sun’s energy has more atmosphere to travel through to reach the poles. This means there is more chance of reflection and absorption by dust, gases, cloud etc to less heat/radiation reaches the surface at the poles.
2. Because of the earth’s curvature, the sun is more concentrated at the equator but the same amount of energy is spread over a wider surface area at the poles so its cooler.
3. The angle of incidence (angle at which the sun hits the earth’s surface) is greater at the poles (120°) than at the surface (90°) so the energy is more spread out.
4. Due to the earth’s orbit around the sun, both the N and S poles spend part of the year tilted away from the sun and so receive less energy overall. The sun is always overhead and high in the sky between the tropics so this region receives the sun’s energy all year round.
5. At the equator, we have green vegetation which absorbs energy (low albedo) while snow and ice at the poles reflect it (high albedo). This means the poles are cooler.

Question 3

Ferrel’s 3 Cell Model of Atmospheric Circulation

Answer 3

Heat is redistributed around the world due to the 3 cell model and associated surface winds.
Winds in the Northern Hemisphere are deflected to the right (left in southern hemisphere) due to corriolis force. Warm air is distributed polewards (higher latitude) and cooler air moves towards the equator for warming via surface winds. At the equator warm air rises creating an area of low pressure. This then splits in the atmosphere, travelling polewards. At around 30° N, this air coolsand sinks creating high pressure at the surface. Air moves from high to low pressure returning this air to the equator eg. North East Trade wind, completing the Hadley cell. Cold air sinks at the poles and creates high pressure and transfers towards the equator for warming. It meets warm air at 60°N causing it to rise, and the air moves back towards the poles, completing the polar cell.
The ferrel cell is formed between 30°N and 60°N. It is thermally indirect and transfers air between the polar and hadley cell.

Question 4

Characteristics of the ITCZ

Answer 4

Tropical Continental
-Low Humidity.
- Stable air mass.
- Origin is Sahara Desert - creates Harmattan winds.
- Hot and dry.
- Hot because it is area of greatest insolation.
- Dry because it has come over land so no oppurtunity to pick up moisture.
Tropical Maritime
- Hot and wet.
- Area of greatest insolation.
- Wet as it originates over ocean so picks up lots of moisture.
- Unstable air mass.
- High humidity.
- Origin travels from gulf of guinea or Atlantic ocean.

Question 5

Impact of Inter Tropical Convergence Zone

Answer 5

Seasonal Rainfall
- Provides water for agriculture. This not only provides people with food but income if they sell their crops.
- May cause river flooding allowing alluvium to be deposited on flood plains. This adds fertility so improves crop growth.
- Water can be stored for farming, drinking etc throughout the dry season.
- In rural areas and shanty towns, open sewers can flood bringing disease.
- Tracks can become muddy making them impassable making communication, trade difficult.
- Heavy rain on dry soils can lead to soil erosion/topsoil being washed away - this is the part that is best for crop growth so can have an impact on food supply.
- Heavy rain can leach nutrients out of soils which impacts crop growth.
- Rain allows plants, bushes etc to flourish which can provide feed for animals as well as fruit etc for locals to eat.
No seasonal rainfall
- Farming systems cannot operate as nothing will grow without rain - no crops to trade.
- Famine/starvation/lack of water weakens people who also become more susceptible to other diseases.
- These in turn may encourage rural to urban migration putting pressure on these areas.
- Refugees.
- Desertification

Question 6

Ocean Circulation

Answer 6

a) With reference to the Atlantic Ocean, currents will flow in loops or gyres. In the Northern Hemisphere these currents move in a clockwise direction (anticlockwise in southern hemisphere). Warm currents travel polewards from the equator. eg.North Atlantic Drift (hot). Once cooled, they return as cold currents from the poles to the equator for warming. An example of a cold water current is the Labrador Current (cold).
b) Ocean currents are affected by prevailing wind. Energy is transferred by friction known as fictional drag. The currents are further deflected by land masses/continents which direct the current eg North America. As the currents move polewards, they experience a change in temperature and salinity, becoming more dense. This causes the cold polar water to sink as it returns to the equator. This displaces the warm water at the equator sending it polewards. The corriolis force (spin of the earth) deflects currents to the right in the northern hemisphere and left in the southern.