Earth’s Atmosphere - EES199 Lecture Notes

Readings

• Chapter 16, all pages
• Chapter 17, pages 518-523
• Chapter 18, pages 552-563
• Chapter 19, pages 578-587
• Chapter 20, pages 621-630

Weather vs Climate

• Weather: Day-to-day state of the atmosphere, short-term variations (minutes to weeks).
• Climate: Weather averaged over a period, often 30 years.
  • Analogy: Weather is your mood; Climate is your personality.

Factors Influencing Weather

• Air temperature
• Humidity
• Air pressure
• Wind speed and direction
• Type and amount of cloud cover
• Type and amount of precipitation

Climate

• Sum/average of weather information describing a place or region.
• Example: Murray, KY has a humid midlatitude climate with warm summers and mild winters.
• Contributing factors are the same as weather.

Unequal Heating by the Sun

• Primary factor influencing weather and climate.

Definition of Atmosphere

• Gaseous part of the earth, interchangeable with air.
• Composed of various gases and particles, held by gravity.
  • Nitrogen (N): 78%
  • Oxygen (O): 21%
  • Argon (Ar): 1%
  • Carbon Dioxide (CO2): 0.04%
• Importance: Nitrogen and Oxygen are crucial for life, but CO2 significantly impacts weather and climate.

Variable Components

• Water Vapor: 0.04-4.0% (volume), source of clouds and precipitation.
• Aerosols: Affect cloud and fog formation.
• Ozone (O3): Affects atmospheric heating and human health.

Greenhouse Effect

• Process trapping the Sun’s heat, contributing to global warming.
• Without greenhouse gases, Earth's average temperature would be near 0°F (-18°C).
• Greenhouse Gases:
  • Water Vapor: 0.4%
  • CO2: 0.03%
  • Methane (CH4): 0.002%
  • Ozone (O3): <0.001%
• Impact: Human activities increase greenhouse gases, affecting climate.

Global Warming Effects

• Increases in sea surface temperature, CO2 in air and ocean, ocean evaporation, and precipitation.
• Potential for drought and increased ocean volume.

Air Pressure

• Weight of air pressing down; varies vertically and horizontally.
• Measured using a barometer.
• Standard sea level pressure: 1 atm = 1.01325 bar, 29.92 inches or 760 mm of mercury.

Structure of the Atmosphere

• Troposphere: 0-12 km, temperature decreases with altitude.
• Stratosphere: 12-50 km, contains the ozone layer, temperature rises with altitude.
• Mesosphere: 50-80 km, temperature decreases with altitude.
• Thermosphere: 80-130 km, temperature rises with altitude.
• Total thickness: 130 km (roughly 100 miles).

Ozone

• Formation: Solar UV radiation breaks O2, forming O3.
• Critical in stratosphere, shields Earth from UV radiation and warms stratosphere.
• Ozone in lower atmosphere considered pollutant (smog).

Ozone Hole

• Depletion caused by human-made chemicals like CFCs, leading to increased UV radiation exposure and environmental impacts.
• Particularly affects Antarctica, leading to ice melting and sea level rise.

Questions (Review)

1. Climate is about the long-term state of the atmosphere.
2. Major elements of weather: air temperature, humidity, etc.
3. Most abundant atmospheric gas: Nitrogen.
4. Variable component: Water vapor.
5. Greenhouse Effect involves trapping heat by greenhouse gases.
6. Air pressure represents the weight of air.
7. The troposphere is where most weather occurs.
8. Ozone layer is in the stratosphere.
9. CFCs break down ozone.
10. Ground level ozone pollution is known as smog.

END