Composition and Layers of the Atmosphere: Gases, Particles, and Energy Transfer

1. Atmosphere Chapter 11 Notes

2. Composition of the Atmosphere • Currently: • Nitrogen (N2): 78% • Oxygen (O2): 21% • Argon (Ar) • Carbon dioxide (CO2) • Water vapor (H2O) • In the past : • Helium, hydrogen, methane, ammonia

3. Variable Atmospheric Components • The following gases change over time: • Water vapor • Carbon dioxide: increase from 0.028% to 0.039% • Ozone • Upper atmosphere: protection from ultraviolet radiation • Lower atmosphere: pollutant • Particles: • Dust • Salt • Ice • Fungi • Bacteria

4. Atmospheric Layers • Troposphere • Weather • Stratosphere • Ozone layer • Mesosphere • Thermosphere • Exosphere • Transition between atmosphere and space

5. Thermal Energy Transfer (Heat) • Radiation: transfer of heat by electromagnetic waves (example: heat lamp) • Visible and infrared EMR is absorbed and reflected by clouds, atmosphere, and Earth’s surface • Rate of absorption varies from place to place, and seasonally • Conduction: heat transferred through direct contact • Convection: movement of heat through currents in a liquid or gas

6. Radiation of Thermal Energy

7. Temperature and air pressure in the atmosphere • Temperature = average kinetic energy of particles in a material, measured in ⁰C, ⁰F, or K • Temperature increases if pressure is increased • Pressure increases if density is increased • Density decreases if temperature increases • Hot air rises • Adiabatic heating and cooling: Air changing temperature without being heated or cooled—by changing pressure

8. Temperature Inversion • Rapid cooling of land on a cold, clear night can cause a temperature inversion • Temperature inversions can cause fog, haze, and smog • Air pollution is trapped under the inversion layer

9. Wind • Air moves from high pressure to low pressure: wind • Pressure differences are caused by unequal heating and cooling of different regions • Friction causes wind to slow down near Earth’s surface • Wind speeds increase at higher altitudes

10. Humidity • Amount of water vapor relative to the amount needed to reach saturation • The dew point is the temperature to which air must be cooled to reach saturation

11. Cloud Formation • Rising air cools, causing water vapor to condense • Condensation nuclei (dust, ice, salt, or other solid particles) must be present for water droplets to stick to • Rising air is unstable • Sinking air is stable (fair weather)

12. Clouds form from rising air

13. Types of Clouds

14. Types of Clouds • High clouds (ice crystals): • Cirrus: wispy horse tails • Cirrostratus: fish scales • Middle clouds: • Altocumulus: wavy rows or masses • Altostratus: thin layered sheets • Low clouds: • Cumulus: puffy • Stratus: layers

15. Types of Precipitation • Rain, snow, sleet, and hail are four main types of precipitation. • Droplets in clouds grow through the process of coalescence when droplet collide and stick together, forming rain drops • Hail forms when droplets move up and down through freezing and non-freezing air