6.1 Introduction to the Atmosphere

Question 1

Atmosphere definition

Answer 1

a dynamic system (with inputs, outputs, flows and storages) that has undergone changes throughout geological time.

Question 2

Atmosphere Inputs

Answer 2

• Water (evaporation and transpiration)
• CO2, SO4 and NO2 from combustion
• Volcanic ash
• Solar radiation
• oxygen through photosynthesis
• aerosols

Question 3

Atmosphere outputs

Answer 3

• precipitation
• solar radiation
• oxygen for respiration
• CO2 for photosynthesis

Question 4

Amount nitrogen

Answer 4

78%
- dilutes oxygen
- prevents rapid burning at the earth’s surface
- living things need it to make proteins

Question 5

Amount oxygen

Answer 5

21%
- passive importance to weather and climate
- produced by photosynthesis
- reduced by deforestation
- needed for animal life

Question 6

Amount argon

Answer 6

0.9% - Used in light bulbs.

Question 7

Amount carbon dioxide

Answer 7

0.04%
- absorbs long wave radiation from earth and therefore contributes to natural greenhouse effect
- increases due to human activity is a major cause of global warming
- used by plants for photosynthesis
- increased by burning fossil fuels and deforestation

Question 8

Amount water vapour

Answer 8

0.2 - 4.0%
- source of cloud formation and percipitation
- reflects/absorbs incoming radiation
- keeps global temp. constant
- provides majority of natural greenhouse effect
- essential for life

Question 9

Atmosphere levels

Answer 9

1. troposphere
2. stratosphere
3. mesosphere
4. thermosphere

Question 10

Troposphere

Answer 10

• fall in temp with height as atmosphere thins
• Most of the atmospheric mass is found.
• Most of our weather occurs here.
• Humans and other organisms have most interaction e.g. through exchange of gases or through introduction of pollutants.
• Greenhouse gases (GHG) help to regulate the temperature of the earth.

Question 11

Mesosphere

Answer 11

• Temperature declines with height
• Coldest part of the atmosphere.
• density prevents absorption of energy

Question 12

Stratosphere

Answer 12

• Temperature is constant at about -60°C in the lower part of the stratosphere, which is shielded by the ozone layer but then increases with altitude.
• The air is dry.
• stable
• thin
• increase in temp with height is due to absorption of solar radiation
• Ozone layer at the top of the stratosphere. Stratospheric ozone absorbs ultra violet radiation from the sun

Question 13

Thermosphere

Answer 13

• Temperatures climb sharply in the lower thermosphere (below 200 to 300 km altitude), then level off and hold fairly steady with increasing altitude above that height.
• virtual vacuum
• rise in absorbed energy due to energised short wave radiation

Question 14

Albedo definition

Answer 14

a measure of the reflectivity of a surface.

Question 15

Albedo effect

Answer 15

when applied to the Earth is a measure of how much of the Sun’s energy is reflected back into space

Question 16

Albedo effect on clouds

Answer 16

More water vapour in the atmosphere means more cloud formation. More clouds lead to increased albedo of the earth.
- Different parts of the Earth have different albedos.

Question 17

About how much of incoming solar radition is reflected back into space?

Answer 17

about 30% (shortwave radiation)

Question 17

What is the greenhouse effect

Answer 17

a natural and necessary process in which greenhouse gases allow short wave radiation (visible light and UV) to pass through the atmosphere but trap a percentage of the outgoing long wave radiation (infrared radiation).
increases global temps. by about 30C → allowing life on earth

Question 18

Discuss the role of the albedo effect from clouds in regulating global average temperature.

Answer 18

• The proportion of incident radiation reflected by a substance is called albedo.
• Low thick clouds, like stratus, have high albedos around 90%.
• High thin clouds, such as cirrus, have lower albedos, approximately 10%.
• Cloud albedo remains consistent across different wavelengths of visible light, indicating their white appearance under white light.
• During sunrise and sunset, clouds reflect the red, orange, or yellow light without modification, showing wavelength independence.
• The albedo of clouds for infrared radiation is likely similar to that for visible light.
• Clouds have two reflective surfaces: the top and bottom, which both play roles in radiation reflection.
• A higher albedo means more solar radiation is reflected back into space, potentially cooling the planet.
• Conversely, a lower albedo results in more solar radiation being absorbed, which can increase Earth’s temperatures.

Question 19

Outline the role of the greenhouse effect in regulating temperature on Earth

Answer 19

• An atmospheric heating phenomenon where the Earth experiences a rise in temperature.
• Certain gases such as water vapor, carbon dioxide, nitrous oxide, and methane allow incoming sunlight to pass through but trap heat radiated from the Earth’s surface.
• If these gases did not trap heat, the Earth’s average temperature would be about 33 degrees centigrade colder.
• These gases are termed greenhouse gases due to their role in warming the planet, creating the greenhouse effect.
• Incoming solar thermal radiation, or heat, is partially reflected by the ozone layer, which blocks the most harmful solar radiation.
  The heat that reaches the - Earth is then re-radiated upwards but is mostly trapped by greenhouse gases, causing it to remain within the Earth’s atmosphere.

Question 20

how do humans impact the atmospheric composition?

Answer 20

through altering inputs and outputs of the system

Question 21

what is the enhanced greenhouse effect?

Answer 21

the anthropocentric/human induced global warming as a result of increased use of greenhouse gases

Question 22

main human activities releasing greenhouse gases/enhancing greenhouse effect

Answer 22

• burning fossil fuels (coal, oil gas) → releasing co2
• deforistation → takes away co2 store → releases more co2 into atmosphere
• fertiliser in agricultural systems → higher nitrous oxide concentration when fertilisers break down

Question 23

GHG in the atmosphere

Answer 23

water vapour, co2, methane, nitrous oxide, CFCs and HCFC

Question 24

Atmosphere processes

Answer 24

• respiration
• photosynthesis
• percipitation
• dry deposition