1. The Atmosphere

2. I. Atmosphere Basics
Atmosphere = the thin layer of gases that surrounds Earth
B. Atmosphere Basics
1) Absorbs radiation and moderates climate
2) Transports and recycles water and nutrients
3) 78% nitrogen gas, 21% oxygen gas, 1% other gases
4) Four layers that differ in temperature, density and composition

3. I. Atmosphere Basics
C. Very small concentrations of permanent (remain at stable concentrations) and variable gases (varying concentrations)
D. Permanent gases include neon, helium, hydrogen and xenon
E. Variable gases include water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3) and chlororfluorocarbons (CFCs)
F. Human activity is changing the amounts of variable gases in the atmosphere.

4. The atmosphere’s composition

5. II. Layers of the Atmosphere
A. Starting from earth and working out into space, the layers of the atmosphere are the troposphere, stratosphere, mesophere, thermosphere, and exosphere

6. II. Layers of the Atmosphere
B. Troposphere = bottommost layer
1) Air for breathing, weather
2. The densest layer – contains the highest concentrations of all atmospheric gasses.
3) Temperature declines with altitude
4) Tropopause = limits mixing between troposphere and the layer above it

7. II. Layers of the Atmosphere
C. Stratosphere = km (7-31 mi) above sea level
1) Drier and less dense, with little vertical mixing
2) Colder in its lower regions
3) Contains UV radiation-blocking ozone, km (10-19 mi) above sea level

8. II. Layers of the Atmosphere
D. Mesosphere = km (31-56 mi) above sea level
Extremely low air pressure
Temperatures decrease with altitude
E. Thermosphere = atmosphere’s second to the top layer
X-rays from the sun
- “Northern lights” formed when sun’s energy hits charged gas molecules in this layer
Extends upward to 500 m (300 mi)
II. Layers of the Atmosphere

9. II. Layers of the Atmosphere
F. Exosphere – Outermost layer - Extremely low in density

10. The atmosphere’s four layers

11. III. Atmospheric properties
A. Atmospheric pressure = measures the force per unit area produced by a column of air
Decreases with altitude
B. Relative humidity = the ratio of water vapor a given volume of air contains to the amount it could contain at a given temperature
C. Temperature = varies with location and time

12. III. Atmospheric properties
D. The spatial relationship between the Earth and sun determines the amount of solar energy striking the Earth
E. Energy from the sun
1) Heats air
2) Moves air
3) Creates seasons
4) Influences weather and climate
F. Solar radiation is highest near the equator

13. III. Atmospheric properties
G. Pressure and density of air in the atmosphere leads to weather systems
1) High-pressure system = air that moves away from a center of high pressure as it descends
Brings fair weather
2) Low-pressure system = air moves toward the low atmospheric pressure at the center of the system and spirals upward
Clouds and precipitation

14. III. Atmospheric properties
H. Air Masses Produce Weather
1) Front = the boundary between air masses that differ in temperature, moisture, and density. Usually produces precipitation or storms.
2) Warm Front = the boundary where warm moist air replaces colder, drier air
3) Cold Front = the boundary where colder, drier air displaces warmer, moister air

15. III. Atmospheric properties
I. Usually, tropospheric air temperature decreases as altitude increases
Warm air rises, causing vertical mixing
J. Thermal inversion = a layer of cool air occurs beneath a layer of warmer air
K. Denser, cooler air at the bottom of the layer resists mixing, trapping pollutants in the troposphere

17. IV. The Greenhouse Effect
As Earth’s surface absorbs solar radiation, it increases in temperature and emits infrared radiation (heat).
When this infrared radiation bounces back to space, it interacts with the gases in the atmosphere (causes the molecules to vibrate), which in turn reflects a lower-energy infrared radiation (heat) back to the lower atmosphere and earth.

19. C. The greenhouse effect is the ability of our atmosphere to trap heat and release some of this heat energy back to the lower atmosphere and earth. D. The natural greenhouse effect is critical to life on earth – without it temperatures would be over 60 F cooler on earth.

20. E. Thinking another way…
Without the greenhouse effect:
Sun’s radiation → absorbed by Earth → Re-radiated to space as heat
2. With the greenhouse effect:
Sun’s Radiation → absorbed by Earth
→ some re-radiated to space as heat
→ some trapped by the atmosphere

21. F. As we increase the concentrations of heat-trapping greenhouse gases in the atmosphere, more heat from the sun is kept in the earth’s lower atmosphere, the crust, and the oceans. G. The percentage of incoming sunlight that is reflected from a surface is called its albedo. The higher the albedo of a surface, the more solar energy it reflects, and the less it absorbs.

22. H. A white surface has a higher albedo than a black surface, so it tends to stay cooler. I. Earth has an average albedo of 30%, but tropical regions with dense forests have albedo values of 10-20%, and snow covered polar regions have albedo values of 80-95%.

23. V. El Nino
El Nino Southern Oscillation (ENSO) is a systematic shift in atmospheric pressure, sea surface temperature, and ocean circulation in the tropical Pacific Ocean.
El Nino conditions are triggered when air pressure increases in the western Pacific and decreases in the eastern Pacific, causing the equatorial winds to weaken.

24. IV. El Nino
C. The normal build up of warm water in the western Pacific is reversed, which stops the normal cold-water upwelling in the Eastern Pacific. Not only is this a problem for the marine life that depend on the nutrient-rich cold water, but it dramatically shifts normal precipitation patterns around the world.

25. IV. El Nino
D. ENSO cycles are periodic but irregular, occurring every 2 to 8 years.

26. V. El Nino Video Why is the fishing so good in Peru and Ecuador?
What is El Nino?
Besides causing fishing problems, name three other problems caused by El Nino.

27. V. El Nino Video
4) Why is the western Pacific 10 C warmer than water at the same latitude in the Eastern Pacific? 5) What happens every 4 to 7 years? 6) What are some of the specific damages that happened in the 1982 El Nino? 7) What did Ethiopia do to prepare for ENSO?