The document discusses the structure and composition of Earth's atmosphere. It describes how the atmosphere is divided into four main layers - the troposphere, stratosphere, mesosphere, and thermosphere - based on trends in average air temperature with altitude. The troposphere contains around 80% of the atmosphere's mass and is where weather occurs. The stratosphere contains the ozone layer which absorbs harmful ultraviolet radiation. Heat from the sun is transferred within the atmosphere and at Earth's surface through various processes including latent heat, sensible heat, and surface heat fluxes.

1. Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
The Atmosphere
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
• How big is the atmosphere?
• Why is it cold in Geneva?
• Why do mountaineers need oxygen on
Everest?
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
• A relatively thin layer of gas over
the Earths surface
• Earth’s radius ~ 6400km
• Atmospheric thickness ~ 100km
http://www.alpix.com/3d/worldwin/
WW_Atmosphere_1_m.jpg
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
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Air Pressure and Altitude
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• Pressure decreases as you
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go up in height.
Altitude (km)
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• The change in is pressure
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12
is not linear. Pressure 8
50% of air
below this
Height of
Mt Everest
decreases exponentially 4
altitude
with altitude.
0 200 400 600 800 1000
Pressure (mb)
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2. Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Air Density and Altitude
• Gravity pulls all particles
down
• More particles at the
bottom of the air column
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
500
400
•
Air Molecules
As gravity pulls gas molecules
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to the Earths surface an
pressure of 100Kpa is exerted
Altitude (km)
Air Density at sea level
200
• 1013.25mb
100 Air
Pressure
0 Low
6
High
Increasing
Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Layers and Temperature
• The atmosphere can be divided into layers based
on temperature characteristics
• The layering creates real physical barriers.
• Mixing occurs within layers but not between layers
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
120
Layers of the atmosphere
100 Thermosphere
• Troposphere
80
Mesopause
• Stratosphere
Altitude (km)
Mesophere
60
Stratopause
• Mesosphere
40
Stratosphere
20
• Thermosphere 0
Tropopause
Troposphere
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3. Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
120
Layers of the atmosphere
100 Thermosphere
0.001mb
Mesopause
80 0.01mb
• Four layers are
Altitude (km)
Mesophere
0.1mb
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defined by trends in Stratopause
1mb
average air 40
temperature
Stratosphere 10mb
20
100mb
Tropopause
Troposphere
1000mb
0
-100 -80 -60 -40 -20 0 20
Temperature oC
40 60
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Troposphere
•
The habitable layer of the atmosphere
• Contains 80% of the atmospheres mass
• Between 8-16 km deep
• Deeper at equator than at the poles
• The part of the atmosphere that contains weather 10
Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Stratosphere
• Contains the ozone layer
• Where ultra-violet radiation is absorbed
• Protects us from harmful high-energy radiation from
the sun
• The stratosphere is warmer than the top of the
troposphere because of the energy absorbed
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Topic 3: Global Cycles and
Physical Systems
100 Thermosphere
0.001mb
Mesopause
3.1: The Atmosphere
80 0.01mb
Altitude (km)
Mesophere
Stratosphere
60
0.1mb
Stratopause
1mb
40 Warming in the
Stratosphere 10mb Stratosphere
20
100mb
Tropopause
Troposphere
1000mb
0
-100 -80 -60 -40 -20 0 20 40 60
Temperature oC
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4. Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Ozone
• Highly reactive molecule oxygen O3
• Two types - Stratospheric and Surface ozone
O
O O
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Surface Ozone
• Result of chemical reactions between a variety of
polluting gases
• Mainly from vehicle emissions
• An irritant
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Stratospheric Ozone
• Beneficial - absorbs ultra-violet radiation
• Protects us from this harmful radiation
• Gets down by chemical reactions with chlorine
containing gases (chlorofluorocarbons – CFCs): Man-
made compounds used in aerosol sprays, refrigerators
and air-conditioners
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Mesosphere
• Between an altitude of 50 - 85 km
• Temperature drops with altitude to about -90oC
• Little or no gases, particles or water vapour to absorb
UV
• This results in no heating taking place
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5. Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Thermosphere
• Extends to the exosphere at about 110km
• The upper layer of the mesosphere and the
thermosphere are called the ionosphere
• Thin layer that contains many ions (charged)
• Responsible for the Northern and Southern Lights and
the reflection of radio waves 17
Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Lapse Rate
• In the troposphere temperature decreases with altitude
• This varies from place to place and season to season
• The amount of moisture in the air has a large effect on
the lapse rate
• Averaged as the Environmental Lapse Rate (ELR)
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Lapse Rate
• ELR is around 6.5oC / 1000m
• This works for about the first 11 km of atmosphere
• But the idea that temperature falls in the troposphere is
important
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6. Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Atmospheric Energy Budget
• Sunlight (short wave radiation)
• Controls weather and climate
• Drives photosynthesis
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
ENERGY IN THE ATMOSPHERE
Incoming solar
Radiation
Reflected
107 Solar
Radiation Outgoing
Longwave
Radiation
342
Reflected by Clouds
and
Atmosphere
Emitted by
77 Atmosphere 165 30
Atmospheric
window
Absorbed by
67 Atmosphere Greenhouse
40 Gases
78 Latent
Heat
24 350 Back
Radiation
Reflected by
Surfaces
30
390
168
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Thermals
Absorbed by surfaces Surface Radiation 324
Absorbed back
78
Evapotranspiration Radiation
Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Energy in the Atmosphere
• Solar radiation can take several paths within
the atmosphere
• 30% reflected by the atmosphere
• 19% absorbed by the atmosphere
• 51% absorbed by Earth’s surfaces
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
100% Solar Radiation
6% Reflected
by atmosphere
20% reflected 19% absorbed by
by the atmosphere
clouds and clouds
4% reflected
from
surfaces
51% absorbed
at the
surface
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7. Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Energy in the Atmosphere
• UV absorption by ozone, water vapour carbon dioxide
and dust and ice particles
• Reflection by clouds and surfaces
• The remainder heats up the Earth in the natural
greenhouse effect
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Differences in Solar energy across the Earths surface
• Because of the curve of the
Earth different values of
solar energy/unit area occur Solar Radiation
• Least solar energy / unit
area is at the poles
• Most solar energy / unit area
is at the equator
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Differences in Solar energy across the Earths surface
• Albedo effect is the Surface type Albedo (%)
balance between a Fresh snow 95
surfaces ability to Dark rock 10
absorb or reflect
Desert sand 35
Urban areas 12-18
Grassland and 10-25
forest
Dry ploughed fields 10-12
Water 8
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Latent and Sensible heat
• Heat is redistributed over the Earths surface by three main
processes
• Latent Heat Flux
• Sensible Heat Flux
• Surface Heat Flux
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8. Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Latent heat flux
• Conversion of solid and liquid water into vapour
• Needs a large amount of heat energy to break bonds in
water
• Circulation by the atmosphere
• Condensation to rain or snow release stored energy
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Sensible heat flux
• Transfer of energy from surface to atmosphere by
conduction and convection
• Energy moved by advection from tropics to poles
• Creates atmospheric circulation
• Moves warm air to poles and cool air to tropics
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
Surface heat flux
• Energy transfered into tropical oceans from sun
• Conversion of solar radiation to heat energy
• Conduction and convection transfer heat down water
column
• Horizontal transfer of warm water (heat) from equator to
poles and back again
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Topic 3: Global Cycles and
Physical Systems
3.1: The Atmosphere
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