Composition of Air and Layers of Atmosphere

Composition of Air

• Air is a mixture of gases, primarily nitrogen (78%) and oxygen (21%).
• Argon and trace amounts of other gases make up the remaining percentage.
• Early Earth lacked oxygen, but photosynthesis produced it.

Layers of the Atmosphere

• Troposphere:
  • Contains most of the atmosphere's mass.
  • Weather occurs here.
  • Temperature decreases with altitude.
  • Extends 9-16 km (5-8 mi) above Earth's surface.
• Stratosphere:
  • Chemical reactions absorb ultraviolet light.
  • Contains most of the Earth's ozone.
  • Temperature increases with altitude due to ozone absorption.
  • Extends 50 km (30 mi) above Earth's surface.
• Mesosphere:
  • Very thin, absorbs little sunlight.
  • Temperature decreases with altitude.
  • Meteors burn up here.
  • Extends 85 km (52 mi) above Earth's surface.
• Thermosphere:
  • Hottest layer.
  • Extends 600 km (375 mi) above Earth's surface.
  • Satellites and the ISS orbit here.
  • Aurora Borealis (Northern Lights) occur.
• Exosphere:
  • Outermost layer, gradually fades into space.
  • No clear upper boundary.

Energy in the Atmosphere

• Temperature vs. Heat:
  • Temperature measures the average speed of particles.
  • Heat is the transfer of thermal energy from hotter to colder.
• Heat Transfer:
  • Sunlight transfers thermal energy through space.
  • Darker surfaces absorb sunlight, lighter surfaces reflect it.
  • Albedo is the ability to reflect light; fresh snow has the highest.
  • Conduction transfers heat when surfaces touch; atmosphere touches Earth.
  • Convection involves rising (hot, less dense) and falling (cold, more dense) air. Creates convection cells.
• Greenhouse Effect:
  • The atmosphere traps heat, maintaining temperatures suitable for life.

Temperature & Humidity

• Temperature:
  • Measured in Celsius (°C).
  • Water freezes at 0°C and boils at 100°C.
• Humidity:
  • Amount of water vapor in the air.
  • Warmer air holds more water vapor than colder air.
  • When air is "full" (saturated), it cannot hold more water vapor.
  • Relative humidity measures how close the air is to saturation.
  • Dew point is the temperature at which water vapor condenses.
  • Frost forms if dew point is below freezing.

Air Pressure

• Air pressure is the force exerted by air on a surface.
• Higher altitudes have lower pressure.

Density

• Density is mass per unit volume.
• Warm air is less dense; Cold air is more dense.
• Pressure affects air density.

Wind and Precipitation

• Wind:
  • Movement of air caused by pressure differences
  • Blows from high to low pressure
  • Speed affected by pressure difference, obstacles (hills, buildings).
• Precipitation:
  • Water falling from the atmosphere (rain, hail, sleet, snow).
  • Forms when water vapor condenses into liquid or solid water.
    • Hail: raindrops frozen repeatedly during their ascent and descent, causing them to increase in size.
    • Sleet: rain that freezes on its way to the ground.
    • Snow: water vapor converting directly to ice crystals.
    • Coalescence: raindrops growing larger as they collide

Water Cycle (Simple)

• Evaporation (A): Liquid water turns into vapor.
• Condensation (B): Water vapor turns back into liquid water.
• Precipitation (C): Liquid or solid water falls from the clouds.
• Runoff (D): Water flows over the ground.

Explore the essential components of air and the distinct layers of the atmosphere in this quiz. Understand the role of each gas in the air and the characteristics of the troposphere, stratosphere, mesosphere, and thermosphere. Test your knowledge on how these layers affect weather and climate.