Learn about the composition and structure of Earth's atmosphere. Discover the different layers, gases, and their importance in sustaining life.

Atmosphere — compositions and structure; elements of weather and climate

• Air and Its Importance
  • Air is essential for survival; humans cannot survive more than a few minutes without it.
  • Breathing occurs every few seconds, unlike eating or drinking, which are less frequent.
  • The atmosphere contains life-supporting gases:
    • Oxygen: For humans and animals.
    • Carbon Dioxide: For plants.



• The Atmosphere
  • The atmosphere is a mixture of gases, water vapor, and dust particles enveloping the Earth.
  • Key Features:
    • Extends 32 km from Earth’s surface (99% of its mass).
    • Colorless, odorless, and tangible only when it moves as wind.
• Composition of the Atmosphere
  • Gases:
    • Nitrogen (78%): The largest component.
    • Oxygen (21%): Supports life.
    • Argon (0.93%) and trace gases like Carbon Dioxide (0.03%).
    • Carbon Dioxide:
      • Transparent to solar radiation, opaque to terrestrial radiation.
      • Contributes to the greenhouse effect and global warming (due to fossil fuel burning).

    

    • Ozone:
      • Found between 10-50 km.
      • Absorbs harmful UV radiation.
  • Water Vapor:
    • Varies by region and altitude:
      • Up to 4% in warm, wet tropics.
      • Less than 1% in dry, cold deserts and polar regions.
    • Regulates Earth’s temperature, preventing extreme heat or cold.
  • Dust Particles:
    • Origin: Sea salts, soil, smoke, ash, pollen, and meteoric debris.
    • Found in lower layers but transported to great heights by air currents.
    • Act as condensation nuclei for cloud formation.



• Structure of the Atmosphere
  • The atmosphere is divided into five layers based on temperature and density:
  • Troposphere (0–13 km):
    • Closest to Earth; contains 75% of the atmospheric mass.
    • Most weather phenomena occur here.
    • Temperature decreases by 1°C every 165 m.
    • Ends at the tropopause, where temperature stabilizes (-80°C at the equator, -45°C at poles).
  • Stratosphere (13–50 km):
    • Contains the ozone layer for UV protection.

  

  • Mesosphere (50–80 km):
    • Temperatures drop to -100°C.
    • Ends at the mesopause.
  • Thermosphere (80–400 km):
    • Contains ions; reflects radio waves.
    • Temperature increases with altitude.
  • Exosphere (>400 km):
    • The outermost layer, transitioning into space.
• Role of the Atmosphere
  • Protects life from harmful UV radiation (ozone layer).
  • Maintains Earth's temperature balance (greenhouse effect).
  • Enables weather, climate, and life processes.
• Elements of Weather and Climate
  • Temperature: Affects air density and circulation.
  • Pressure: Varies with altitude, influencing wind patterns.
  • Winds: Movement of air.
  • Humidity: Amount of water vapor in the air.
  • Clouds and Precipitation: Result from condensation.



• Summary of Questions
  • Multiple Choice:
    • Major atmospheric gas: Nitrogen.
    • Most critical layer for humans: Troposphere.
    • Dust particle association: Dust particles.
    • Negligible oxygen at: 120 km.
    • Gas transparent to solar and opaque to terrestrial radiation: Carbon Dioxide.
  • Short Questions:
    • What is the atmosphere?
    • Elements of weather and climate?
    • Composition of the atmosphere?
    • Why is the troposphere the most important layer?
  • Detailed Questions:
    • Describe the atmosphere’s composition.
    • Diagram and label the atmospheric structure.