Lecture Notes: Introduction to the Atmosphere (IB ESS 6.1)

Overview

• This lecture covers the subtopic about the atmosphere and its significance to life on Earth under the main IB ESS topic 6: Atmospheric Systems and Society.

Significant Idea 1: The Dynamic Atmosphere

• The atmosphere is a dynamic system crucial for life on Earth.
• Historical Development of Earth's Atmosphere:
  • First Atmosphere: Composed mostly of hydrogen and helium, blown away by solar wind.
  • Second Atmosphere: Formed 4.5 million years ago by volcanic outgassing, releasing gases like water vapor, carbon dioxide, and methane.
  • Third Atmosphere: Oxygen levels rose due to photosynthetic organisms.
  • Present atmosphere primarily contains nitrogen and oxygen with trace amounts of gases like carbon dioxide and argon.

Dynamic System of the Atmosphere

• Inputs and Outputs:
  • Energy and matter inputs include solar radiation and gases.
  • Outputs involve reflected solar radiation by Earth's surface or clouds.
• Heat Balance:
  • Incoming solar radiation is absorbed or reflected.
  • Long wave radiation involved in the greenhouse effect, crucial for maintaining suitable temperatures.

Significant Idea 2: Atmosphere's Influence on Ecosystems

• Layers of the Atmosphere:
  • Troposphere: 0-10 km - weather phenomena, water vapor.
  • Stratosphere: 10-50 km - contains the ozone layer absorbing UV light.
  • Mesosphere: Burns up meteors, difficult to study.
  • Thermosphere: Northern Lights occur here.
• Temperature Variation:
  • Temperature decreases with altitude in the troposphere and mesosphere, increases in stratosphere and thermosphere.
• Pressure Variation:
  • Decreases with altitude.
  • Similar to ocean pressure; less air pressure at higher altitudes.

Atmospheric Circulation and Heat Budget

• Energy Balance:
  • Tropical latitudes have a positive heat balance; poles have a negative balance.
  • Atmospheric circulation helps balance energy.

Greenhouse Effect

• Natural and Essential:
  • Greenhouse gases trap heat, maintaining Earth's average temperature of 15°C.
  • Essential gases: carbon dioxide, water vapor, methane, nitrous oxide.
• Role of Clouds:
  • Reflect sunlight (cooling) and trap heat (warming).

Human Impact on Atmospheric Composition

• Enhanced Greenhouse Effect:
  • Increased levels of greenhouse gases due to fossil fuels, deforestation, agriculture, etc.
  • Enhanced gases trap more heat, leading to global warming.
• Pollutants and Greenhouse Gases:
  • Human activities contribute to air pollution and affect greenhouse gas levels.
  • CFCs and smog discussed in further IB ESS topics.

Conclusion

• A summary of atmospheric introduction, highlighting human influence and the significance of atmospheric layers and processes.
• Recommended resources include the IB ESS textbook.

This concludes the lecture on IB ESS Topic 6.1 Introduction to the Atmosphere.