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TOPIC 6: Atmospheric Systems & Societies

6.1 Introduction to the Atmosphere

6.2 Stratospheric Ozone

6.3 Photochemical Smog

6.4 Acid Deposition

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6.1 SL/HL Knowledge & Understandings (1hr)

      • The atmosphere is a dynamic system (with inputs, outputs, flows, and storages) that has undergone changes throughout geological time.
      • The atmosphere is predominantly a mixture of nitrogen and oxygen, with smaller amounts of carbon dioxide, argon, water vapor, and other trace gases.
      • Human activities impact atmospheric composition through altering inputs and outputs of the system. Changes in the concentrations of atmospheric gases – such as ozone, carbon dioxide, and water vapor – have significant effects on ecosystems.
      • Most reactions connected to living systems occur in the inner layers of the atmosphere, which are the troposphere (0 – 10 km above sea level) and the stratosphere (10 – 50 km above sea level).
      • Most clouds form in the troposphere and play an important role in the albedo effect of the planet.
      • The greenhouse effect of the atmosphere is a natural and necessary phenomenon maintaining suitable temperatures for living systems.

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Vocabulary

  • outgassing
  • altitude
  • particulate
  • troposphere
  • stratosphere
  • mesosphere
  • thermosphere
  • ionosphere
  • magnetosphere
  • ​
  • offgassing
  • albedo
  • shortwave radiation
  • longwave radiation
  • greenhouse effect
  • transmission
  • absorption
  • reflection
  • reradiation
  • ​

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6.1.1(2.4.3, 4.1.1) The Sun’s (sol) Radiation

… emission of energy or particles through space or another medium - heliophysics

  • EM radiation (γ particles @ light speed, c ≈ 300 000 km.s-1)
    • UV
    • visible
    • IR
  • Solar wind ions (plasma from corona @ 250-750 km.s-1)
    • α particles → (He nuclei)
    • β particles → e-
    • p+
    • trace other nuclei
  • Magnetosphere - Aurora borealis & australis

The sun’s weather in storm cycles

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6.1.1 The Atmosphere

Envelope of gases surrounding planet

    • 78% N2
    • 21% O2
    • 0.93% Ar
    • trace gases
  • Average of 1% H2O(v)
  • Layers → → → → → → →
    • divided by T
    • we live in the troposphere
  • According to NASA, space begins at 160km (100 miles)
    • ISS at ~ 400km

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6.1.2 Atmospheric History

Evolution of the atmosphere divided into 4 stages:

  1. Origin
    1. similar to gas giants
  2. Chemical/Prebiological era
    • outgassing
  3. Microbial era
    • cyanobacteria
  4. Biological era
    • O2 increase

​

Outgassing evidenced in marine sedimentary rocks

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6.1.2 Microbial Era

Vapor is possible source of H2O along with Cl, CO2, N2, H2

CH4 & CO2 atmosphere

Blue-green algae → O2 (cyanobacteria) formed stromatolites

Oxidized by iron for 3 billion years (banded iron formation - BIF)

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6.1.2 O2

Once O2 in atmosphere, split by UV to create O3

Life left the oceans...

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6.1.2 Atmosphere Today

H2O(v) concentration varies by temp

Mixture constant up to altitude of ~10 000 m

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6.1.3 Human Inputs & Outputs

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6.1.3 Increased CO2, H2O(v), & O3 Effects

CO2: warming, photosynthesis

​

H2O(v): warming, cooling

​

O3: human health, photosynthesis

(click the picture for EPA’s BenMAP)

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6.1.3 Human CO2

Combustion:

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6.1.3 Human H2O(v)

In general:

... poorly understood...

“Five Reasons Why Water Vapor Feedback Might Not Be Positive”

  • Roy W. Spencer, Ph.D

Primarily radiosonde data

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6.1.3 Clouds = H2O(v)

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6.1.3 Human O3 (& nitrous oxide[s])

Ozone → good & bad

N2O = “laughing gas”

O3 sources are scarce (copiers & air purifiers), though a secondary pollutant - Air Quality Guide O3 (EPA)

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6.1.4 Atmospheric Layers

Divided roughly by temperature profile...

Can you explain why?

Mesosphere poorly understood

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6.1.5 Albedo

The fraction (often expressed as a %) of shortwave radiation reflected back to space

Thick clouds - high albedo

Thin clouds - low albedo

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6.1.5 Geoengineering

Technocentrics ask: can we reverse the global warming trend using cloud-brightening?

Let’s look @ the greenhouse effect...

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6.1.6 Greenhouse Effect

Transmission -

Reflection -

Absorption -

Reradiation -

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6.1.6 Greenhouse Effect Sankey Diagram

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Long wavelength (λ) → low frequency (f) → low energy (E)

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6.1.6 Why is the Sky Blue?

Transmission -

Reflection -

Absorption -

Reradiation -

Rayleigh scattering -

← Click on picture to read about The Scream’s blood-red sky seen from Oslo in 1893

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6.1.6 Four Greenhouse Gases

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6.1.6 Greenhouse Gases

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6.1.6 Runaway Greenhouse Effect

About the same size

  • 94.99% of Earth’s radius

Distance from sun

  • 0.723 AU (Earth = 1 AU)

Gravitational strength

  • 92.6% of Earth’s

Surface temperature

  • 462 oC
  • about 93 x Earth’s atm. pressure
    • 96.5% CO2, 3.5% N

​

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6.1.6 The Effect

Avg. temp of Earth ~15 oC

Without greenhouse effect, avg temp would be ~ -18 oC

Current data (NOAA)

More on this later...