1. McKnight's Physical Geography 11e Introduction to the Atmosphere
Lectures
Chapter 3
Introduction to the Atmosphere
Andrew Mercer
Mississippi State University
© 2014 Pearson Education, Inc.

2. Learning Goals of This Chapter
Identify the three major gases found in the atmosphere by percentage.
Identify the four most important variable gases found in the atmosphere.
Describe the role of atmospheric water vapor on weather and climate.
Describe the role of small concentrations of carbon dioxide on weather and climate.
Describe the role of small concentrations of ozone on weather and climate.
Describe the role of atmospheric particulates (aerosols) on weather and climate.

3. Learning Goals of This Chapter
Describe the role of other atmospheric impurities on weather and climate.
Describe the characteristics of the troposphere.
Describe the characteristics of the stratosphere.
Describe the characteristics of the upper thermal layers.
Describe the characteristics of atmospheric pressure with increased altitude.
Describe the characteristics of the atmospheric layers by composition.
Describe the characteristics of the ionosphere.

4. Learning Goals of This Chapter
Explain the impact of the release of chemicals by humans on the ozone composition of the atmosphere.
Explain how humans have altered the composition of the atmosphere with primary pollutants.
Explain how humans have altered the composition of the atmosphere causing secondary pollutants.
Explain how humans have altered the composition of the atmosphere with particulates.
Differentiate between weather and climate.
List the four ingredients of weather and climate.
Summarize the seven most important “controls” of weather and climate.

5. Introduction to the Atmosphere
Size and Composition of the Atmosphere
Composition of the Modern Atmosphere
Vertical Structure of the Atmosphere
Human-Induced Atmospheric Change
Weather and Climate

6. Size and Composition of the Atmosphere
Atmosphere uniformly surrounds Earth
Held down by Earth’s gravity
Extends up to 10,000 km from the surface
More than 50% of the total mass is below 6 km
Development of the atmosphere

7. Composition of the Atmosphere
Two primary gas types
Permanent
Oxygen and nitrogen
Variable
Water vapor
Carbon dioxide
Ozone
Other variable gases
Permanent gases make up over 95% of total atmosphere

8. Composition of the Atmosphere
Particulates
Non-gaseous particles that exist in the atmosphere
Many human-induced and natural types
Many are hygroscopic
Some reflect or absorb sunlight

9. Vertical Structure of the Atmosphere
Thermal layers
Troposphere – lowest 10–15 km of atmosphere; most weather occurs here
Stratosphere – stagnant air
Mesosphere – middle of atmosphere
Thermosphere – “heat”
Exosphere – transitions into interplanetary space

10. Vertical Structure of the Atmosphere
Air pressure
Analogous to the “weight” of the air
Decreases with height at nonconstant rate
Low levels compressed by air above, so surface pressure is higher
90% of atmosphere is in lowest 16 km

11. Vertical Structure of the Atmosphere
Composition
Homosphere – lowest 80 km
Heterosphere – above heterosphere
Ozone layer – between 15 and 48 km; ozonosphere
Ionsophere – between 60 and 400 km; source of auroras

12. Human-Induced Atmospheric Change
Introduction of impurities into the atmosphere at rapid pace
Received international attention in recent years
Example is the reduction of ozone by CFCs (Chlorofluorocarbons)

13. Human-Induced Atmospheric Change
The ozone hole
Release of CFCs (Chlorofluorocarbons) resulted in a significant loss of stratospheric ozone, depicted as a “hole”
Ozone loss tends to group near the Antarctic Polar vortex, so hole is most pronounced there
Resultant UV intensity increased in affected regions
Montreal Protocol

14. Human-Induced Atmospheric Change
Definition of Pollution
Primary versus secondary pollutants
Primary pollutants
Particulates
Carbon monoxide
Nitrogen compounds
Sulfur compounds
Secondary pollutants
Photochemical smog
Ozone
Indoor pollutants

15. Human-Induced Atmospheric Change
Consequences of anthropogenic pollution
Relationship of energy production to anthropogenic pollution

16. Weather and Climate
Weather – short-term atmospheric conditions for a specific area
Meteorology
Climate – aggregate long-term weather conditions
Climatology
Weather versus climate

17. Weather and Climate Latitude
Regions nearer poles receive less solar radiation, which affects local climate.
Distinction between continental and maritime climates
Seattle, WA, and Fargo, ND, have vastly different climates.
Maritime climates are typically much more humid.

18. Weather and Climate General circulation of the atmosphere
Semipermanent wind pattern on Earth
General circulation of the oceans
Oceanic broad-scale semipermanent motions

19. Weather and Climate Altitude Topographic barriers
Four controls of weather and climate affected by altitude
Topographic barriers
Can drastically alter climate due to orographic change in wind patterns

20. Weather and Climate Storms
Control weather and climate through atmospheric modification
Some storms prominent enough to affect climate

21. Weather and Climate Coriolis effect
Rotation of Earth modifies path of forward motion over great distances
Discovered by Gaspard Coriolis
Causes a rightward turn to motion in the Northern Hemisphere
Causes a leftward turn in the Southern Hemisphere
Deflection greatest at the poles; zero at the equator
Proportional to the speed of the object
Has no influence on speed
Influences wind patterns within storms and hurricanes and can contribute to upwelling of cold ocean water near coasts

22. Weather and Climate
The Coriolis effect

23. Summary
Earth’s atmosphere is a shallow “ocean” of air that uniformly surrounds Earth.
The atmosphere consists of many permanent and variable gases.
The gas with the highest concentration in Earth’s atmosphere is nitrogen (78%).
The atmosphere has various vertical structures that describe it.
Five main spheres make up the thermal atmosphere.

24. Summary
The homosphere and heterosphere describe the gas composition of the atmosphere at different heights.
Most auroral activity occurs in the ionosphere.
Human activity has modified the atmospheric composition through pollution and ozone depletion.
Weather and climate, while related, are discussing atmospheric conditions on different time scales.
Many controls exist that modify the four primary weather elements.
The Coriolis force is an apparent force that exists due to the rotation of Earth.

25. Summary
Equinoxes and solstices help identify when a seasonal transition occurs.
Time zones were established to have a uniform global time system.
Daylight-savings time was devised to conserve energy by adding an hour of daylight.