1. Introduction to Atmospheric Science
Unit 1
Introduction to Atmospheric Science

2. 1.1 Composition Our atmosphere Composition
Mix of gases surrounding entire planet
Held in place by gravity
Filters out energy and materials from space
Regulates temperature, allows for water in all 3 states
Composition
Nitrogen – 78%
Oxygen – 21%
Argon – .9%
All other gases and particulants – .1%

3. 1.1 Composition

4. 1.1 Composition Nitrogen and oxygen
Percentages are consistent to elevation of 50 miles (80 km)
Balance of destruction and production
Nitrogen removed mostly by soil bacteria, plankton
Returned by decay of plant and animal materials
Oxygen removed through chemical reaction (oxidation), organic decay, respiration
Returned through photosynthesis

5. 1.1 Composition Water vapor Invisible gas made of water molecules
Substance follows the water cycle
Varies greatly by location
Tropical air may be up to 4% water, arctic air may barely have any
Acts as a “greenhouse” gas, trapping Earth’s radiant energy
Latent heat
Energy stored in water molecules, gained through evaporation
Released when water condenses to liquid

6. 1.1 Composition Carbon dioxide Occupies .038%, but varies by location
Enters air through decay, volcanism, exhalation of animals, burning of fossil fuels
Removed through photosynthesis, dissolving into oceans, absorption by phytoplankton
Oceans may hold over 50X more CO2 than air
Past CO2 concentrations measured through Arctic and Antarctic ice cores
Evidence shows concentrations have increased 37% since the early 1800s.
Important greenhouse gas, contributes to climate change.

7. Stepped Art
Fig. 1-4, p. 7

8. FIGURE 1.5
Measurements of CO2
in parts per million
(ppm) at Mauna Loa
Observatory, Hawaii.
Higher readings
occur in winter when
plants die and release
CO2 to the atmosphere.
Lower readings
occur in summer
when more abundant
vegetation absorbs
CO2 from the atmosphere.
The solid line
is the average yearly
value. Notice that the
concentration of CO2
has increased by more
than 20 percent since
1958.

10. 1.1 Composition Ozone (O3) Most forms naturally in stratosphere
Provides protection from UV rays
Can be formed at surface
Chemical reactions between pollutants and sunlight create ozone
Called photochemical smog
Irritates eyes, lungs, damages plants
Common near large cities

11. 1.1 The Early Atmosphere
The Earth’s first atmosphere was composed mostly of hydrogen and helium
Evolved due to outgassing of CO2, NH3, and H2O from the cooling center of the Earth
Caused heavy rain that would form an early ocean
Lakes and oceans acted as a sink, absorbing CO2 from atmosphere
Reactions with oxygen broke down ammonia, plus volcanic eruptions produced most N2
O2 was created almost completely through photosynthesis, first by cyanobacteria
Later, aquatic plants and algae, then terrestrial plants added O2 to today’s levels

12. 1.2 Vertical Structure of the Atmosphere
Air Pressure and Air Density
Weight = mass x gravity
Density = mass/volume
Pressure = force/area
At the Earth’s surface the pressure of the atmosphere is 14.7 lbs/in2 .
Standard sea level pressure is millibars (mb) = 101,325 Pascals (Pa) = in Hg
Atmospheric pressure decreases with height.

13. FIGURE 1.9 Both air pressure and air density decrease with
increasing altitude. The weight of all the air molecules above the earth’s
surface produces an average pressure near 14.7 lbs/in.2

14. FIGURE 1.10 Atmospheric pressure decreases rapidly with
height. Climbing to an altitude of only 5.5 km, where the pressure is
500 mb, would put you above one-half of the atmosphere’s molecules.

15. 1.2 Vertical Structure of the Atmosphere
Layers of the Atmosphere
Lapse rate
Change in temperature with a change in height
Typically inverse relationship, decrease in temp with increase in height
Isothermal environment
No change in temperature with height
Inversion layer
Reversal of standard lapse rate
Temps increase with height

16. 1.2 Vertical Structure of the Atmosphere
Layers of the Atmosphere
Troposphere
Decrease in temperature with height
Daily weather occurs here.
Extends up about 12 miles
Stratosphere
Ozone layer located here.
Increase in temperature caused by absorption of UV by O3
12 miles up to 50 miles

17. 1.2 Vertical Structure of the Atmosphere
Mesosphere
Decrease in temperature
Most meteors burn up here
50 to 85 miles
Thermosphere
Increase in temperature
Suns strongest radiation impact.
Dramatic temperature swings day to night
85 miles, up to the point where no gas exists

18. Stepped Art
Fig. 1-11, p. 13

19. 1.2 Vertical Structure of the Atmosphere
Ionosphere
Not a true layer but an electrified region
Created when solar energy rips electrons from gas atoms
Creates ionized layers
Exists at the top of the atmosphere in the thermosphere
F,E,D layer
Sun light creates layers, D disappears at night and less interference with AM radio transmissions.

21. 1.3 Weather & Climate Weather
Short term air temperature, air pressure, humidity, clouds, precipitation, visibility, and wind
Climate
Long term patterns and average weather; not just magnitude but also frequency

22. 1.3 Weather & Climate Meteorology
Study of the atmosphere and its phenomena
Aristotle 340 B.C. Meterologica, meteoros: high in air
1843 telegraph
1920s air masses
1940s upper air
1950s radar and computers
1960s satellite

24. 1.3 Weather & Climate Satellite’s View Geostationary satellite
Meridians measure longitude (W-E)
Parallels measure latitude (N-S)
Weather maps: pressure cells, fronts, surface stations

26. 1.3 Weather & Climate Weather and Climate in Our Lives
Two general reasons for studying how weather and climate impacts our lives: economic efficiency and public safety.
Clothing
Crops
Utilities
Extreme cold and heat
Tornados and hurricanes

27. 1.3 Weather & Climate Meteorologist
Any person with a college degree in meteorology or atmospheric science; not just the TV weather person
Half of 9000 meteorologists employed by the US National Weather Service
Researchers and operational meteorologists