Atmosphere

1. Atmosphere • Global heat budget • Redistribution of energy by atmospheric and oceanic circulation • Cause and impact of the Intertropical Convergence Zone (ITCZ) The atmosphere was formed as the Earth cooled and it now envelopes the Earth. It is made up of a mixture of gases and gives us life, making our planet unique and distinctive.

2. The Global Heat Budget The Global heat budget is the balance between the incoming and outgoing solar radiation. Incoming solar radiation is also called INSOLATION. It is received in the form of short-wave energy.

3. The Global Heat Budget

4. Short wave solar radiation (insolation) enters the Earth’s atmosphere. 24% of this energy is reflected by clouds and the Earth’s surface (ice and snow). 6% is scattered by gases in the atmosphere. In total 30% of radiation is reflected by albedo (the reflectiveness of a surface). 19% of radiation is absorbed by clouds, water vapour and dust. Only 51% of the radiation is absorbed by the Earth’s surface. This heat is then reflected as long wave (infra red) radiation. 6% of this energy goes out into space and 94% is absorbed by water vapour, CO2 and other greenhouse gases (methane, nitrous oxide). It is then re-radiated. Without these greenhouse gases Earth would be 30°C cooler.

5. The Global Heat Budget Latitudinal Variations in the Energy Balance

6. The Global Heat Budget Latitudinal Variations in the Energy Balance • Study the graph showing latitude and energy balance, note down the following • point and then answer the questions that follow: • Between approximately 35°N and 35°S there is a surplus of energy because • incoming solar insolation exceeds outgoing radiation. • Is there an energy deficit or surplus polewards from 35°N/S? • At what latitudes is there an energy balance? • What is the terrestrial radiation: • At the poles • At the equator • 4. What is the solar insolation: • At the poles • At the equator WHY?

7. The Global Heat Budget Latitudinal Variations in the Energy Balance Look at the diagram in pairs and discuss reasons why tropical areas receive more solar insolation than polar areas Use the following clues to help you: 1. Compare the dotted lines where Q and P strike the Earth 2. Compare the amount of atmosphere Q and P travel through 3. What other differences are there between the tropical areas and polar areas that might affect the amount of insolation they get (hint ALBEDO)? 4. Are there any seasonal effects?

8. The Global Heat Budget 1. The Sun’s rays are more concentrated at the equator and more spread out at the poles due to the strike angle so there is less insolation at the Poles. 2. In Polar regions, there is a greater amount of atmosphere to pass through, so more insolation is reflected or absorbed by clouds and dust. 3. Light coloured surfaces (snow) reflect heat back into the atmosphere (high albedo). Rainforests are dark and absorb heat (low albedo). 4. Due to the tilt of the earth the poles receive no solar insolation for several months whilst the sun is directly overhead all year round at the equator.

9. REDISTRIBUTION OF ENERGY BY ATMOSPHERIC AND OCEANIC CIRCULATION Energy is transferred from lower latitude energy surplus areas to higher latitude energy deficit areas by atmospheric circulation. If there was no atmospheric circulation, lower latitudes would get hotter and hotter and higher latitudes colder and colder.

10. Cold air descends giving areas of high pressure. activeboard Hot air rises creating areas of low pressure Air moves from areas of high to low pressure

11. ATMOSPHERE Polar Cell THE THREE CELLS TOGETHER Ferrel Cell Hadley Cell Hadley Cell Ferrel Cell Polar Cell

12. ATMOSPHERE SOLAR ENERY CELLS AND HEAT TRANSFER A single cell model like in diagram 9 is too simplistic- there are threeinterlinked cells! THE THREE CELL MODEL;-FORMATION OF THE HADLEY CELL (1) At the Equator warm air rises and travels to the poles. INSOLATION

13. ATMOSPHERE NORTHERN HADLEY CELL. SOUTHERN HADLEY CELL. FORMATION OF THE HADLEY CELL (2) The air cools and begins to fall 30ºN and S of the Equator. Cooled air returns to the Equator. This is the Hadley cell. SOLAR ENERGY

14. ATMOSPHERE FORMATION OF THE POLAR CELL (1) Cold, dense air sinks at the poles and moves towards the Equator.

15. ATMOSPHERE NORTHERN POLAR CELLS. SOUTHERNPOLAR CELLS. FORMATION OF THE POLAR CELL (2) At about 60ºN and 60 ºS, the cold polar air begins to warm. This warm air rises and returns to the pole, carrying heat energy. This is called the POLAR CELL.

16. ATMOSPHERE FORMATION OF THE FERREL CELL The Ferrel Cell is caused by friction between the other two cells. The Hadley Cell draws cool air down at 30ºN and S and the Polar Cell sends warm air up at 60ºN and S.

17. ATMOSPHERE Polar Cell THE THREE CELLS TOGETHER Ferrel Cell Hadley Cell Hadley Cell Ferrel Cell Polar Cell

18. ATMOSPHERE Polar Cell The climatic zones associated with the cells Ferrel Cell Hadley Cell Hadley Cell Ferrel Cell Polar Cell

19. SOLAR ENERGY THE TRANSFER OF HEAT ENERGY FROM EQUATORIAL TO POLAR AREAS Where air carrying energy from the Equator in the Hadley Cell comes into contact with air in the Ferrel Cell, there is a transfer of heat energy into the Ferrel Cell. There is a similar transfer of heat energy from the Ferrel Cell to the Polar Cell. In this way, heat energy is transferred from the Equator, where there is a surplus of energy, to the poles where there is a deficit.

20. THE CORRESPONDING MOVEMENT OF COLDER AIR In the Polar cell cold air from polar regions flows to mid-latitudes as polar easterly winds In the Ferrel Cell there is a movement of cold air at high altitude. In the Hadley Cell, cooler air moves from the sub-tropics to the Equator. Q

21. Ocean Currents and Heat Transfer

22. AIM: To be able to DESCRIBE and EXPLAIN the pattern of the earth’s major ocean currents. The oceans receive about 70% of the sun’s insolation and the ocean currents play an important part in redistributing this energy. 1. Shade in the arrows RED and BLUE to show the warm and cold currents. 2. Label the currents A to F next to the map.

23. DESCRIBING ocean currents: Look at the currents in the Atlantic Ocean…….. Describe the movement of ocean currents in the North Atlantic gyre.

24. EXPLAINING what influences the ocean currents…….. 1. Prevailing winds…. Surface ocean currents directly respond to prevailing winds e.g. the westerlies in the Atlantic help direct the Gulf Stream and North Atlantic Drift. 2. Coriolis force….. This deflects the currents RIGHT in the northern hemisphere and LEFT in the southern hemisphere. 3. Land masses…. Currents are blocked and deflected by continental landmasses setting up roughly circular loops or GYRES – clockwise in the northern hemisphere and anticlockwise in the southern hemisphere. The exception is the Antarctic circumpolar (west wind drift) – WHY? 4. Temperature difference….. Cold water is denser and therefore sinks and travels towards equator. Warm water less dense so rises to surface and flows away from the equator. A convection cell is created.

25. The Intertropical Convergence Zone (ITCZ)

26. ITCZ CASE STUDY: WEST AFRICA Label the following countries on your maps: NIGERIA, BENIN, TOGO, GHANA, COTE D’IVOIRE, BURKINA FASO, MALI, NIGER

27. Shade in the rainfall amounts and include a key for your map. RAINFALL

28. Shade in the vegetation types for the case study area and include a key. VEGETATION

29. High annual temperatures with little variation throughout the year. Rainfall throughout the year can often exceed 2000mm often with two maxima. High temperatures with a bigger temperature range giving a cool, dry season; a hot dry season and a hot wet season. Sometimes called savanna. Areas receive less than 250mm rainfall a year. Temperatures range from 15 - 35°C. EQUATORIAL DESERT TROPICAL

30. ITCZ – the two main air masses. AIR MASSES An air mass is an extensive body of air that is influenced by the earth’s surface. Those developing over oceans generally hold more water vapour. North east trade winds South east trade winds Add the two arrows to your 2nd map

31. 1. The ITCZ is the meeting point of a hot, wet and unstable tropical maritime air mass (mT) from the Gulf of Guinea (south east trade winds) and a hot, dry and stable tropical continental (cT) air mass from the Sahara desert (north east trade winds) also know as the Harmattan winds. Where the air masses meet warm air rises, condenses and causes heavy rain.

32. 1. Where this happens warm air rises, condenses and heavy rain falls.

33. 2. The meeting point of these two air masses moves north when the sun moves north of the equator (June) and it moves south when the sun is overhead south of equator (December) because of the tilt in the earth’s axis. It is known as the thermal equator.

34. ATMOSPHERE IN JUNE S N Compare the January and July diagrams. Hot dry cT air Wet warm mT air Moves this way ‘Harmattan’ wind HEAVY RAINS LIGHT RAINS Gulf of Guinea Coastal areas- equatorial climate Inland areas- savanna climate type Sahara- Desert climate type

35. ATMOSPHERE Hot wet mT air HEAVY RAINS IN DECEMBER N S Hot dry cT air Moves this way ‘Harmattan’ wind Gulf of Guinea Coastal areas- equatorial climate Inland areas- savanna climate type Sahara- Desert climate type

36. Animation

37. Explanation of ITCZ • The ITCZ is the meeting point of a hot, wet and unstable tropical maritime air mass (mT) from the Gulf of Guinea (south east trade winds) and a hot, dry and stable tropical continental (cT) air mass from the Sahara desert (north east trade winds) also known as the Harmattan winds. Where the air masses meet warm air rises, condenses and causes heavy rain. • The meeting point of these two air masses moves north when the sun moves north of the equator (June) and it moves south when the sun is overhead south of the equator (December) because of the tilt in the earth’s axis. It is known as the thermal equator. • In June the hot, moist mT air mass pushes north against the hot, dry cT air mass. The rain reaches its furthest point north and the south has a dry season. • In December the cT air mass pushes south and the north has a very dry season.

38. Describe the rainfall graph for Gao which is in the south of the Sahara desert. • When is the maximum rainfall – amount and month? • When is there least rainfall – amount and month? • Write a sentence for the trend in rainfall. Is there a lot, does it fall at a certain time of year?

39. Describe the rainfall graph for Bobo-Dioulasso which is in the Savanna region. • When is the maximum rainfall – amount and month? • When is there least rainfall – amount and month? • Write a sentence for the trend in rainfall. Is there a lot, does it fall at a certain time of year?

40. Describe the rainfall graph for Abidjan which is on the Gulf of Guinea. • When is the maximum rainfall – amount and month? Is there just one peak? • When is there least rainfall – amount and month? • Write a sentence for the trend in rainfall. Is there a lot, does it fall at a certain time of year?

41. Past Paper Question “Tropical latitudes receive more solar energy than polar latitudes. The atmosphere and oceans help to redistribute this energy to maintain a global energy balance.” Explain fully the ways in which the circulation cells in the atmosphere help to redistribute energy (4 marks)

42. At the Equator warm air rises and travels to the poles. The air cools and begins to fall 30ºN and S of the Equator. Cooled air returns to the Equator. This is the Hadley cell. • Cold, dense air sinks at the poles and moves towards the Equator. At about 60ºN and 60 ºS, the cold polar air begins to warm. This warm air rises and returns to the pole, carrying heat energy. This is called the Polar cell. • The Ferrel Cell is caused by friction between the other two cells. The Hadley Cell draws cool air down at 30ºN and S and the Polar Cell sends warm air up at 60ºN and S. • The three cells transfer heat energy from the Equator towards the Poles. Assess out of 4. A maximum of 1 mark should be awarded for correctly located or drawn Cells – with a maximum of 2 for the explanation of any one cell. A fully annotated diagram could score full marks. 4 marks

43. Attempt the 2011 Higher atmosphere question. Remember it is a 6 mark answer not 12 marks.