1. HIGHER GEOGRAPHY
PHYSICAL ENVIRONMENTS
ATMOSPHERE

2. Learning Intentions Atmosphere We will be learning about:
The characteristics of the atmosphere and how they vary spatially and provide climate and weather conditions which interlink with other systems.
Further development
Candidates should have a knowledge and understanding of:

3. 1 Global scale:
♦ effects of the atmosphere on the receipt of radiation at the Earth’s surface -causes of latitudinal variations of radiation receipt
♦ patterns of atmospheric and oceanic circulation and their influence on the redistribution of energy over the globe - principal circulation cells, pressure and wind belts, influence of ocean currents
♦ global climate change - physical and human causes of global warming
2 Regional scale - equatorial and savanna regions of Africa:
♦ nature, origin and movement of air masses, including convergence and divergence
♦ weather types associated with different air masses
role of continental tropical and maritime tropical air masses on West African climate - particularly rainfall amounts and distribution.

4. THE
ATMOSPHERE

5. Troposphere = main zone
of weather and climate.
lapse rate
= decrease in temperature
with altitude
= 6.4ºC for every
1000metres
= approximately 1ºC for
every 150 metres

6. Mt Everest (8800metres)
Calculate the difference in temperature between sea level
and the summit of the mountain.

7. ATMOSPHERIC GASES
Nitrogen - 78%
Oxygen - 21%
Carbon dioxide % …...and rising!!
Water vapour - variable - up to 4% over tropical oceans.
(as humidity increases the relative amounts of other
gases decrease).

8. Global extremes of Temperature In the absence of an atmosphere
San Luis
Potosi, Mexico
Al Aziziyah,
Libya
-88ºC
Vostok
Antarctica
In the absence of an atmosphere
the Earth would average about 30ºC
less than it does at present.
Life (as we now know it) could not exist.

9. SOLAR INSOLATION 100% 25% 23% 52% 6% 46% reflected by clouds
and dust, water vapour and other gases
in the atmosphere
100%
25%
absorbed by clouds
and dust, water vapour and other gases in the atmosphere
23%
52%
reflected by surface 6%
absorbed by surface
46%

10. reflected by atmosphere absorbed by atmosphere
SOLAR INSOLATION
100%
solar insolation
TOTAL ALBEDO =
= 31%
25%
reflected by atmosphere
23%
absorbed by atmosphere
TOTAL ABSORPTION =
= 69%
52%
reaches surface 6%
reflected by surface
46%
absorbed by surface

11. ENERGY SURPLUS and DEFICIT
The Earth's atmosphere is put into motion
because of the differential heating of the Earth’s
surface by solar insolation.
The Poles receive less heat than the Tropics because:
1. Insolation has to pass through more of the
Earth’s atmosphere
2. the angle of incidence of insolation
and
3. higher levels of surface albedo.

12. 3 2 1 1 2 3 Insolation has to pass through more of the
Earth’s atmosphere 1
The angle of incidence of insolation -
energy is spread out over a larger area because
the sun’s rays strike the surface at a lower angle. 2 3
Higher levels of surface albedo -
the ice-cap reflects more solar insolation

13. Angle of Incidence
Energy concentrated on a smaller surface area

14. Describe the energy surplus and deficit across the globe

15. There is a surplus of energy between 35N & 35S and incoming insolation exceeds outgoing radiation. Where outgoing radiation exceeds incoming insolation there is a deficit.
Insolation rises sharply from 50 joules at the poles to 275 joules at the equator. Terrestrial radiation varies less, from 120 joules at the poles to 200 joules at the equator. Energy is transferred by atmospheric circulation and ocean currents.

16. In theory an imbalance in energy receipt could result
in lower latitudes becoming warmer and higher
latitudes becoming even colder.
In reality energy is transferred from lower latitudes
(areas of surplus)
to higher latitudes
(areas of deficit) BY
1. ATMOSPHERIC CIRCULATION
and
2. OCEAN CURRENTS

17. 1. ATMOSPHERIC CIRCULATION
DEFICIT
0º Equator
90º Pole
1. ATMOSPHERIC CIRCULATION
2. OCEAN CURRENTS
SURPLUS

18. NO!
not directly
0º Equator
90º Pole
surplus
deficit

19. TRANSFER of ENERGY by ATMOSPHERIC CIRCULATION
0º Equator
90º Pole

20. TRANSFER of ENERGY by OCEAN CURRENTS
90º Pole
0º Equator

21. ATMOSPHERIC
CIRCULATION

22. SINGLE CELL MODEL 0º Equator 90º Pole LP HP
At the Equator the atmosphere is heated
Air becomes less dense and rises.
Rising air creates low pressure at the equator.
Air cools as it rises because of the lapse rate.
Air spreads.
As air mass cools it increases in density and descends.
Descending air creates high pressure at the Poles.
Surface winds blow from HP to LP.
0º Equator
90º Pole
LP HP

23.  warm air is less dense therefore lighter
 air rises in the Tropics
 this creates a zone of LOW PRESSURE
 air spreads N and S of the Equator
 air cools and sinks over the Poles
 this is a zone of HIGH PRESSURE
 air returns as surface WINDS to the Tropics

24. The single cell model of atmospheric circulation
was developed to explain the transfer of energy
from the Tropics to the Poles.
This was later improved and a three cell model
was developed.
Today the three cell model is also considered to be
an oversimplification of reality.

25. HADLEY CELL
ITCZ
ITCZ = Inter-tropical convergence Zone (Low Pressure)
STH = Sub-tropical High (High Pressure)

26. THREE CELL MODEL
Hadley
Cell
Polar
Cell
Ferrel
Cell
0º Equator
90º Pole
30º
60º
LP HP LP HP

27. Warm air rises at the Equator -
ENERGY TRANSFER
Warm air rises at the Equator -
Inter-Tropical Convergence Zone (ITCZ).
Equatorial air flows to ~30º N then sinks to the surface
and returns as a surface flow to the tropics.
This is the Hadley cell.
Cold air sinks at the North Pole. It flows S at the surface
and is warmed by contact with land/ocean,
by ~60º N it rises into the atmosphere.
This the Polar cell.
Between 60º N and 30º N there is another circulation cell.
This is the Ferrel cell.
The Hadley cell and the Polar cell are thermally direct cells.
The Ferrel cell is a thermally indirect cell.

28. ENERGY TRANSFER Polar Hadley Ferrel Cell
Heat energy is transferred from the Hadley Cell to the Ferrel Cell
and from the Ferrel Cell to the Polar Cell.
In this way heat is transferred from the Equator
where there is an energy surplus
to the Poles
where there is an energy deficit.

29. WINDS
convergence
divergence
convergence
divergence
0º Equator
90º Pole
30º
60º
LP HP LP HP
winds blow from high pressure zones to low pressure zones

30. WINDS
convergence
diverence
convergence
divergence
0º Equator
90º Pole
30º
60º
LP HP LP HP
Explain how circulation cells in the atmosphere assist in the
Transfer of energy from areas of surplus to areas of deficit

31. Warm air rises at the Equator 0˚ (LP) and travels into the upper atmosphere to around 30˚ N and S, cools and sinks (HP) – this means it is thermally direct. Air moves from the tropical high to the low pressure area at the equator creating the Hadley Cell Air rises at 60˚N and S (LP) into the upper atmosphere where it flows to the Poles and sinks at 90˚N and S (HP). The Polar cell is also thermally direct as warm air rises, cools and sinks. The Ferrel cell is placed between the Hadley cell and Polar cell. Unlike the other two types of cells, the Ferrel cells are known as thermally indirect cells because their motion is dependent upon the motion within the Hadley and Polar cells in between which they are found. In this way energy is transferred from the equator (area of surplus) to the poles (area of deficit)

32. CONVERGENCE and …………DIVERGENCE

34. PLANETARY
WIND SYSTEM

35. CORIOLIS Coriolis occurs because the Earth rotates.
Earth rotates about its axis every 24 hours.
Distance around the equator is ~25,000 miles
the earth is travelling east at ~ 1,000 miles per hour.
Distance around the Earth at 40ºN ~19,000 miles
the earth is travelling east at ~800mph.
The Coriolis effect results from this difference in velocity.
In the Northern hemisphere the Coriolis effect
deflects movement to the right.
In the Southern hemisphere the Coriolis effect
deflects movement to the left.
The combination of atmospheric cells
and Coriolis effect lead to the wind belts.
Wind belts drive surface ocean circulation
CORIOLIS

36. Winds are named by the direction they blow from.
PLANETARY WINDS
High Pressure
Coriolis effect
WIND
pressure gradient force
Low Pressure
Winds are named by the direction they blow from.

37. Be very, very careful what you put into that
head, because you will never, ever get it out.
Thomas Cardinal Wolsey ( )
CORIOLIS
The water in a sink rotates one way as it drains in the northern hemisphere
and the other way in the southern hemisphere. Called the Coriolis Effect,
it is caused by the rotation of the Earth.
This is NOT true!
The Coriolis force is so small, that it plays no role in determining
the direction of rotation of a draining sink anymore than it does
the direction of a spinning CD.

38. WIND BELTS 90ºN 60ºN Temperate Low LP 30ºN
Polar easterlies
60ºN
Temperate Low LP
South westerlies
30ºN
Sub-tropical High - Horse Latitudes HP
NE Trades 0º
Equatorial Low - Doldrums LP
SE Trades
30ºS
Sub-tropical High - Horse Latitudes HP
North westerlies
60ºS
Temperate Low LP
Polar easterlies
90ºS

39. WIND BELTS 60ºN 30ºN 0º 30ºS 60ºS 90ºS Polar easterlies convergence LP
South westerlies
30ºN
divergence Sub-tropical High HP
NE Trades 0º
convergence Inter-tropical convergence zone LP
SE Trades
30ºS
divergence Sub-tropical High HP
North westerlies
60ºS
convergence LP
Polar easterlies
90ºS

40. WIND BELTS

41. WIND BELTS Northern Hemisphere
Polar Easterlies Blowing from the Polar High Pressure zone to about 60ºN
Westerlies Blowing from Sub-Tropical High Pressure zone to about 60ºN
Northeast Trade Winds Blowing from Sub-Tropical High Pressure zone to
Equatorial Low Pressure zone.
Southern Hemisphere
Southeast Trade Winds Blowing from Sub-Tropical High Pressure zone to
Westerlies Blowing from Sub-Tropical High Pressure zone to about 60ºS
Polar Easterlies Blowing from the Polar High Pressure zone to about 60ºS

42. Series of High and Low pressure centres approx. every latitude
pressure zones associated with descending air ( )
Low pressure zones associated with air (convergence)
circulation cells in each hemisphere:
thermally direct
thermally indirect
Polar Cell thermally direct
Wind is the horizontal movement of air arising from differences in
Very little wind at the Equator ( ) because air is being convected
Little wind at 30ºN and S (Horse Latitudes) because direction of air movement is down.
Winds always blow from an area of Pressure to Pressure.
Winds are affected by the Effect.
This is a consequence of motion on a rotating sphere.
Acts to the of direction of motion in Northern Hemisphere
Acts to the of direction of motion in the Southern Hemisphere
Major wind belts of the Earth surface
0 to 30ºN
Southeast Trades
30 to 60ºN/S
60 to 90ºN/S Polar
SLIDE 37

43. Series of High and Low pressure centres approx. every 30º latitude
High pressure zones associated with descending air (divergence)
Low pressure zones associated with rising air (convergence)
Three circulation cells in each hemisphere:
Hadley Cell thermally direct
Ferrel Cell thermally indirect
Polar Cell thermally direct
Wind is the horizontal movement of air arising from differences in pressure.
Very little wind at the Equator (Doldrums) because air is being convected upward.
Little wind at 30ºN and S (Horse Latitudes) because direction of air movement is down.
Winds always blow from an area of High Pressure to Low Pressure.
Winds are affected by the Coriolis Effect.
This is a consequence of motion on a rotating sphere.
Acts to the Right of direction of motion in Northern Hemisphere
Acts to the Left of direction of motion in the Southern Hemisphere
Major wind belts of the Earth surface
0 to 30ºN Northeast Trades
0 to 30ºS Southeast Trades
30 to 60ºN/S Westerlies
60 to 90ºN/S Polar easterlies

44. INTER-TROPICAL
CONVERGENCE ZONE
(ITCZ)

45. These two dates are the solstices.
23º
The most intense heating of the sun, occurring at the so-called thermal equator, annually moves between the tropics.
On or around June 20th each year the sun is overhead at 23½ºN, the Tropic of Cancer.
On or around December 20th the the sun is at overhead at 23½ºS, the Tropic of Capricorn.
These two dates are the solstices.
Twice a year, at the equinoxes, on or around March 20th and September 20th the overhead sun crosses the equator.
This annual north to south and back again "shift" of the thermal equator shifts the belts of planetary winds and pressure systems to the north and to the south as the year turns.

46. 23½ºN 0º 23½ºS June Summer Solstice TROPIC of CANCER
September Autumn Equinox
March Spring Equinox 0º
EQUATOR
December Winter Solstice
23½ºS
TROPIC of CAPRICORN

47. ITCZ

48. ITCZ
JULY
ITCZ
JANUARY

49. The location of the ITCZ varies throughout the year
The ITCZ over land moves farther north or south than the ITCZ over the oceans
due to the variation in land temperatures.
ITCZ JANUARY
ITCZ JULY

50.
The blue shading on the map shows the areas of highest cloud reflectivity,
which correspond to the average monthly position of the ITCZ.

51. The migration of the inter-tropical convergence zone (ITCZ) in Africa affects seasonal precipitation patterns across that continent.

52. ITCZ moves north in summer
DESERT
dry all year
SAVANNA
dry ‘winter’
wet ‘summer’
RAINFOREST
wet all year
ITCZ moves north in summer

53. Tropical rainforest
savanna

54. The further North
of the Equator in tropical Africa:-
the lower the annual rainfall
the more the rainfall is concentrated in the summer months
the more variable the rainfall.

55. seasonality increases variability increases
GUINEA
SAVANNA
SAHEL
SAVANNA
DESERT
RAINFOREST 0º
20ºN
10ºN
rainfall decreases
seasonality increases
variability increases

56. TRANSECT ACROSS WEST AFRICA

57. LAGOS
SOKOTO
TIMBUKTU

58. savanna
climate
tropical summer rain

59. savanna
vegetation

60. savanna ‘parkland’

61. savanna ‘parkland’

62. savanna ‘parkland’

63. savanna ‘parkland’

64. baobab tree

65. acacia tree

66. acacia thorns

67. desertification

68. OCEAN
CURRENTS

69. This circulation is known as a
4 forces:
solar heating
gravity
Coriolis effect
and surface winds
result in a clockwise circulation of
water in the Northern hemisphere.
This circulation is known as a
GYRE.

70. OCEAN CURRENTS IN THE NORTH ATLANTIC1
NORTH EQUATORIAL CURRENT
90º Pole 2 4
GULF STREAM 5 3
NORTH ATLANTIC DRIFT 3 4
NORTH ATLANTIC DRIFT 6 2 5
LABRADOR CURRENT 1 6
CANARIES CURRENT
0º Equator

71. EQUATOR
Atlantic Currents

74. GLOBAL
WARMING

75. The greenhouse effect is the name applied to the process
which causes the surface of the Earth to be warmer than it would have been in the absence of an atmosphere.
Global warming
or the enhanced greenhouse effect
is the name given to an expected increase in the magnitude of the greenhouse effect, whereby the surface of the Earth will amost inevitably become hotter than it is now.

77. About 70% of the sun's energy is radiated back into space.
But some of the infrared radiation is trapped by greenhouse gases
and warms the atmosphere,

79. Water vapour accounts for 98% of the natural Greenhouse effect.
Water vapour has lower ‘radiative forcing’ properties than
some other atmospheric gases such as
carbon dioxide, methane and nitrous oxide
which are naturally present in the atmosphere
in small quantities.
Since the Industrial Revolution the proportion
of these gases has increased significantly.

80. CO2
CFCs
N2O
CH4
1 Carbon Dioxide > fossil fuels, vehicle emissions, forest clearance
2 Methane > rice cultivation, biomass burning, digestive fermentation,
termites, sewage, landfill, natural gas production
3 CFCs > aerosol propellants, refrigerants, foaming agents
4 Nitrous oxide > nitrogen fertilisers, industrial pollution

81. CONCENTRATION CHANGES SINCE 1750
Carbon Dioxide: 280 ppm ppm (+30%)
Methane: 0.70 ppm ppm (+145%)
Methane c25 x effect of CO2
CFCS (chlorofluorocarbons)
recent significant decrease due to concern about OZONE LAYER
BUT
CFCs c10,000 x effect of CO2

84. Global temperature change

85. Global temperature change
°C Temperature anomalies from the period

87. Politics of global warming

90. Climate change
Great film...
...rubbish Geography!

91. RESOURCES Core Higher Geography The Atmosphere pages 4-35
How to Pass Higher Geography
Physical Environment
Atmosphere Core
Pages 6-21

92. KEY POINT 1 You should be able to explain, using an appropriate diagram, why tropical latitudes receive more solar energy than polar regions.
KEY POINT 2 You should be able to explain why there is a net gain of solar energy in the Tropical latitudes and a net loss towards the Poles.
KEY POINT 3 You should be able to describe the distribution of the amount of solar energy which is absorbed by the earth. This is known as the earth’s heat budget
KEY POINT 4
You should be able to describe the factors which affect the amount of sunlight reflected from the earth’s surface.
KEY POINT 5
You must be able to describe the role of atmospheric circulation in the redistribution of energy over the globe. This is called ‘Global Transfer of Energy’.
KEY POINT 6
You should be able to describe and explain how this happens using an appropriate diagram.

93. KEY POINT 7 You should be able to describe the pattern of atmospheric circulation and global winds.
KEY POINT 8 You should be able to explain the pattern of atmospheric circulation and global winds.
KEY POINT 9 You should be able to describe the main wind patterns throughout the earth
KEY POINT 10 You should be able to describe the general pattern of ocean currents on a world map
KEY POINT 11
You should be able to explain the general pattern of ocean currents.
KEY POINT 12
You should be able to describe variations in global temperatures for the last 100 years as shown on a graph.
KEY POINT 13
You should be able to suggest both physical and human reasons for variations in global temperatures for the last years.

94. KEY POINT 14 You should be able to describe the origin, nature and weather characteristics of Tropical Maritime and Tropical Continental air masses which affect west Africa.
KEY POINT 15 You should know about inter-tropical convergence zones and Convergence and Divergence in relation to West Africa.
KEY POINT 16 You should know the main features of the equatorial climate.
KEY POINT 17 You should know the main features of a savanna climate.
KEY POINT 18
You should know the effects of air masses and inter-tropical fronts on the equatorial and savanna climates.
KEY POINT 19
You should be able to describe and account for variations in West African rainfall with reference to the ITCZ.
KEY POINT 20
You should know the following geographical techniques:
How to construct climate graphs

95. Describe and explain the pattern of energy surplus and deficit and explain how energy is transferred from surplus to deficit.
Answer
See slide 14!

99. Higher Geography 2005

103. By the end of this topic you should be able to:Ø
explain with the aid of an annotated diagram, why Tropical latitudes receive more of the
sun’s energy than Polar regions
explain why there is a net gain of solar region in the Tropical latitudes and a net loss
towards the poles
describe the role of atmospheric circulation in the redistribution of energy over the globe
describe and explain the earth’s energy exchanges shown on a diagram
describe the factors which affect the amount of sunlight reflected from the earth’s surface
describe and account for the pattern of atmospheric circulation and global winds, or
ocean currents shown on a world map
describe the variations in world temperature for the last 100 years (shown
eg. on a graph)
and suggest both physical and human reasons for these variations
describe and explain the origin, nature and weather characteristics of Tropical Maritime (
mT)
and Tropical Continental (
cT) air masses which affect West Africa
with reference to the Inter-Tropical Convergence Zone and the movement of air masses,
describe and account for the variations in West African rainfall distribution.