1. Atmosphere Chapter 11 Notes

2. Composition of the Atmosphere Currently: – Nitrogen (N 2 ): 78% – Oxygen (O 2 ): 21% – Argon (Ar) – Carbon dioxide (CO 2 ) – Water vapor (H 2 O) 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. 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