Atmosphere

Question 1

Energy distribution - tropical latitudes

Answer 1

• Due to the curve of the Earth the sun’s rays are concentrated on a much smaller surface area over the tropical latitudes, resulting in more energy.
• The intensity of insolation is greatest on the equator because the angle of the sun is higher, at close to 90o.
• The Sun’s rays are more concentrated, as the midday Sun is high in the sky throughout the year.
• Rays have less atmosphere to pass through at the Tropics so less energy is lost through absorption and reflection.
• The darker forested areas and dense vegetation in the Tropics absorb radiation so albedo is lower.

Question 2

Energy distribution - polar latitudes

Answer 2

• Due to the curve of the earth, the sun’s angle of insolation is lower at the poles so the rays of energy are spread out over a much larger area and are therefore less intense.
• The sunlight travels at an angle and so through more distance of atmosphere, which means less energy reaches the surface of polar regions.
• Lighter snow/ice covered areas at the poles reflect more radiation and so polar regions have a higher albedo.
• Due to the tilt of the Earth there is no insolation at the poles during the winter solstices.

Question 3

Patterns of ocean currents in the North Atlantic

Answer 3

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

Question 4

Explain how ocean currents redistribute energy across the globe

Answer 4

• Ocean currents are greatly influenced by the prevailing winds with energy being transferred by friction to the ocean currents.
• Land masses like North America divert ocean currents.
• 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.
• The Coriolis effect deflects currents to the right in the Northern Hemisphere.

Question 5

Explain atmospheric circulation

Answer 5

1. Warm air from the Equator is distributed to higher and cooler latitudes and cold air from the Poles distributed to lower and warmer latitudes.
2. The 3 circulating cells not only transfer heat from the equator to the polar regions, they result in areas of high and low pressure and create climatic zones.
3. Rising air creates areas of low pressure, resulting in higher rainfall – which is why areas of rainforest are found near the equator.
4. Descending air creates areas of high pressure, resulting in clear skies and lower rainfall – which leads to desert regions.
5. Due to the Coriolis effect winds are deflected to the right in the northern hemisphere.
6. A jet stream is a type of air current that forms high in the atmosphere, which can move storms and other weather systems from west to east.

Question 6

Describe the origin and characteristics of the ICTZ

Answer 6

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 7

Suggest reasons for differences in the ICTZ

Answer 7

• The ITCZ is an area of low pressure where the trade winds/air masses meet
• The maritime airmass is pushed up, cooling and codensing to form clouds
• 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.
• Coastal cities are influenced by the wet mT air for most of the year.
• Inland cities are under the influence of the dry cT air for most of the year.