1. The Atmosphere

2. Atmospheric Composition
Grab a handful of air…
Earth’s atmosphere is mostly nitrogen and oxygen
N2 (78%) and O2 (21%) make up 99% of the atmosphere
Less than 1% is other gases (e.g., argon, carbon dioxide, methane, water vapor), dust

3. Earth’s Atmosphere

4. Key Atmospheric Gases (Small but Mighty)
Water (H2O)
Amount changes constantly, 0-4%
Source of clouds and precipitation
Absorbs heat from Earth and some solar energy
Ozone (O3)
Very small amount (>0.01%)
Absorbs harmful UV radiation
Protects our skin from sun damage
Carbon dioxide (CO2)
0.03%
Absorbs heat, contributes to global warming
Methane (CH4)
Extremely small amount (>0.001%)

5. Human Influences on Atmosphere (just a few examples)
Chloroflorocarbons (CFCs -- aerosols, refrigerants, some Styrofoam) destroy the ozone layer
CO2 emissions from cars contribute to global warming
Air pollution causes human health problems
asthma
lung cancer
respiratory illness
heart disease

6. Primary Pollutants

7. Atmospheric structure
The atmosphere is made up of 4 main layers, defined by temperature and composition:
Troposphere
Stratosphere
Mesosphere
Thermosphere

9. Troposphere Sphere of weather Thinnest layer of the atmosphere
Temperatures decrease with height
(Have you ever been to the top of a mountain?)
Greenhouse effect
Height: 0-12 km

10. Snowy Mountaintops Contrast with Warmer Snow-Free Lowlands

11. Stratosphere Temperatures increase Ozone layer
Long distance airplane flights (lower part)
Height: km

12. Mesosphere Temperatures decrease (as low as -90◦ C) Meteors burn up
Height: km

13. Thermosphere Temperatures increase (O2 and N2 absorb solar radiation)
Northern lights, satellites, space shuttle
80 km to…? (no defined upper limit)

15. Do you mean Temperature… or Heat?
Temperature: measurement of the kinetic energy (energy of motion) of atoms or molecules
Faster motion = higher temp.
Heat: transfer of energy from one object to another because of a difference in temperature
Heat flows from higher to lower temp.
Heat fuels the weather, and temperature measures it!

16. Pressure-Density-Temperature Relationship
Air pressure: weight of the air pressing on you
gases at the top press down on the ones below
Density: measure of particles in a given space
More particles = higher density
Temperature: proportional to pressure, inversely proportional to density
Atmospheric
Relationships
As T ↑ , P ↑
As T ↓ , P ↓
As T ↑ , D ↓
As T ↓ , D ↑
T = Temperature
P = Pressure
D = Density
↑ = Increases
↓ = Decreases

17. Air Pressure v. Altitude
Altitude: measure of distance “up” in the air
As altitude ↑, pressure ↓ (and therefore T ↓)
Why is it harder to breathe at the top of a mountain?
Components of
the atmosphere

18. Write your summary box!