1. Characteristics of the atmosphere lecture 22.1b

2. Composition Gases in air: Gases in air: N 78% O 2 21% Argon 0.93% CO 2.035% Thickness: 400 mi. from surface to space.

3. Troposphere Layer closest to ground. Layer closest to ground. O 2 and H 2 O are most dense. O 2 and H 2 O are most dense. All weather occurs in this layer. All weather occurs in this layer. With elevation, temperature and O 2 decrease. With elevation, temperature and O 2 decrease.

4. Temperature Inversions Happen when warm air sits above cold air. Happen when warm air sits above cold air. Pollutants are trapped near the ground. Pollutants are trapped near the ground. Ex: ‘spare the air’ days/nights, smog Ex: ‘spare the air’ days/nights, smog

5. Stratosphere Ozone layer in upper region. Ozone layer in upper region. O 3 molecules absorb UV radiation from sun, protecting life. O 3 molecules absorb UV radiation from sun, protecting life.

6. Ozone “hole” Use of CFCs has caused a thinning of the ozone layer. Use of CFCs has caused a thinning of the ozone layer. CFCs are in refrigerants, A/C and aerosols CFCs are in refrigerants, A/C and aerosols Result: more UV radiation hit earth. Result: more UV radiation hit earth.

7. Recovery Recovery Nations agreed to stop using CFCs in 1987. Nations agreed to stop using CFCs in 1987. The ozone layer appears to be getting thicker again. The ozone layer appears to be getting thicker again.

8. U pper atmosphere Ionosphere: Radio waves reflect off ions in this layer (farther @ night) Ionosphere: Radio waves reflect off ions in this layer (farther @ night) Thermosphere: 980 C Thermosphere: 980 C Satellites, International Space Station Satellites, International Space Station Sunrise from the Space Shuttle

9. Magnetosphere and plasmasphere protect earth from solar wind, radiation. Generated by earth’s magnetic field.

10. Aurora borealis Auroras circle the earth’s magnetic poles. Auroras circle the earth’s magnetic poles. Solar energy excites ions- photons of light are released as e- fall back to lower E levels. Solar energy excites ions- photons of light are released as e- fall back to lower E levels.

11. Changes over time Early earth’s atmosphere was toxic. Early earth’s atmosphere was toxic. Volcanoes out-gassed methane (CH 4 ) CO 2, H 2 O. Volcanoes out-gassed methane (CH 4 ) CO 2, H 2 O. Comets added organic molecules. Comets added organic molecules.

12. Photosynthesis Later, algae+ plants develop ability to use sunlight to store energy. Later, algae+ plants develop ability to use sunlight to store energy. Oxygen in atmosphere was created by this process: 20% of air today. Oxygen in atmosphere was created by this process: 20% of air today. CO 2 + H 2 O C 6 H 12 O 6 + O 2

13. Carbon/ Oxygen cycle Plants and the oceans absorb Carbon. Plants and the oceans absorb Carbon. Respiration and burning release Carbon as CO 2. Respiration and burning release Carbon as CO 2.

14. Greenhouse effect Greenhouses are warmer than their surroundings. Greenhouses are warmer than their surroundings. Their walls prevent heat from escaping, trapping it inside. Their walls prevent heat from escaping, trapping it inside.

15. Greenhouse gases CO 2, H 2 O gas in the atmosphere warms the earth. CO 2, H 2 O gas in the atmosphere warms the earth. Burning fossil fuels has greatly increased CO 2 levels. Burning fossil fuels has greatly increased CO 2 levels. Effect: our planet is warming at a rapid rate. Effect: our planet is warming at a rapid rate.