2. Focus on the Atmosphere
Weather
Occurs over a short period of time
Constantly changing
Climate
Averaged over a long period of time
Generalized, composite of weather

3. Weather and Climate Elements of weather and climate
Properties that are measured regularly:
Air temperature
Humidity
Type and amount of cloudiness
Type and amount of precipitation
Air pressure
Wind speed and direction

4. Weather and Climate

5. Composition of the Atmosphere
Air is a mixture of discrete gases
Major components of clean, dry air
78% Nitrogen (N)
21% Oxygen (O2)
Argon and other gases
0.04% Carbon dioxide (CO2)

6. Major Components

7. Variable Components Water vapor Aerosols Up to 4% of air’s volume
Forms clouds and precipitation
Greenhouse gas
Aerosols
Tiny solid and liquid particles
Water vapor can condense on solids
Reflect sunlight
Color sunrise and sunset

8. Variable Components

9. Variable Components Ozone Three atoms of oxygen (O3)
Distribution not uniform
Concentrated between 10 and 50 km above the surface
Absorbs harmful UV radiation

10. Pressure Changes Atmospheric pressure is the weight of the air above.
Average sea level pressure is 1000 millibars or 14.7 psi
Pressure decreases with altitude
Half of atmosphere is below 3.5 mi (5.6 km)
90% of atmosphere is below 10 mi (16 km)

11. Pressure Changes

12. Temperature Changes Four atmospheric layers based on temperature
Troposphere
Lowermost layer
Temperature decreases with increasing altitude
Environmental lapse rate
Average 6.5C per km or 3.5F per 1000 feet
Thickness varies
Average height is about 12 km
Outer boundary is the tropopause

13. Temperature Changes

14. Temperature Changes The environmental lapse rate is variable
Actual environmental lapse rate for any particular time and place
Measured with a radiosonde
Attached to a balloon and transmits data by radio

15. Temperature Changes

16. Temperature Changes Stratosphere Mesosphere Thermosphere 12 to 50 km
Temperature increases at top
Outer boundary is the stratopause
Mesosphere
50 to 80 km
Temperature decreases
Outer boundary is the mesopause
Thermosphere
No well-defined upper limit
Fraction of atmosphere’s mass
Gases moving at high speeds

17. Temperature Changes

18. Earth–Sun Relationships
Earth’s motions
Rotation on its axis
Once every 24 hours
Circle of illumination is the line separating Earth’s lighted half from dark half
Orbital motion around the Sun
Seasons
Result of:
Changing Sun angle
Changing length of daylight

19. Earth–Sun Relationships

20. Earth–Sun Relationships
Seasons
Caused by Earth’s changing orientation to the Sun
Axis is inclined 23.5º
Axis is always pointed in the same direction

21. Earth–Sun Relationships
Special days (Northern Hemisphere)
Summer solstice: June 21–22
Sun’s vertical rays located at Tropic of Cancer
23.5º N latitude
Winter solstice: December 21–22
Sun’s vertical rays located at Tropic of Capricorn
23.5º S latitude
Autumnal equinox: September 22–23
Sun’s vertical rays located at equator (0º latitude)
Spring equinox: March 21–22

22. Earth–Sun Relationships
[insert Figure and Table 11.1 here]

23. Earth–Sun Relationships

24. Energy, Heat, and Temperature
Heat is synonymous with thermal energy
Temperature refers to the intensity, or degree of "hotness"
Heat is always transferred from warmer to cooler objects

25. Energy, Heat, and Temperature
Mechanisms of heat transfer
Conduction
Molecular activity
Convection
Mass movement within a substance
Radiation (electromagnetic radiation)
Gamma waves, X-rays
Ultraviolet,visible, infrared
Microwaves and radio waves

26. Energy, Heat, and Temperature

27. Energy, Heat, and Temperature
Laws of Radiation
All objects emit radiant energy
Hotter objects radiate more total energy per unit area than colder objects
Hotter objects radiate more short-wavelength radiation than cooler objects
Good absorbers of radiation are good emitters as well

28. Energy, Heat, and Temperature

29. Heating the Atmosphere
Incoming solar radiation
Atmosphere is largely transparent to incoming solar radiation
Atmospheric effects
Reflection
Albedo (percent reflected)
Scattering
Absorption
Most visible radiation reaches the surface
About 50% absorbed at Earth’s surface

30. Heating the Atmosphere

31. Heating the Atmosphere

32. Heating the Atmosphere

33. Heating the Atmosphere
Radiation from Earth’s surface
Earth re-radiates longer wavelengths
Terrestrial radiation
Terrestrial radiation is absorbed by
Carbon dioxide and water vapor
Lower atmosphere is heated from Earth’s surface
Heating of the atmosphere is termed the greenhouse effect

34. Heating the Atmosphere

35. Human Impact on Global Climate
CO2 levels are rising
Industrialization of the past 200 years
Burning fossil fuels
coal, natural gas, and petroleum
Deforestation
Present CO2 level is 30% higher than its highest level over at least the past 800,000 years

36. Human Impact on Global Climate

37. Human Impact on Global Climate

38. Human Impact on Global Climate
Important impacts of human-induced global warming:
Rise in sea level
Shift in large-storm paths
Changes in precipitation distribution
Changes in occurrence of severe weather
Stronger tropical storms
Increasing frequency and intensity of heat waves and droughts
Gradual environmental shifts

39. Human Impact on Global Climate

40. For the Record: Air Temperature Data
Temperature measurement
Daily maximum and minimum
Other measurements
Daily mean temperature
Daily range
Monthly mean
Annual mean
Annual temperature range

41. For the Record: Air Temperature Data
Isotherms used to examine distribution of air temperatures over large areas
Line that connects points of the same temperature
iso = equal, therm = temperature
Easy to visualize temperature gradient

42. For the Record: Air Temperature Data

43. Why Temperatures Vary: The Controls of Temperature
Temperature control – any factor that causes temperature to vary from place to place and from time to time
Receipt of solar radiation
Differential heating of land and water
Land heats more rapidly than water
Land gets hotter than water
Land cools faster than water
Land gets cooler than water

44. Why Temperatures Vary: The Controls of Temperature
Specific heat is the amount of energy needed to raise the temperature of 1 gram of a substance 1 degree Celsius

45. Why Temperatures Vary: The Controls of Temperature

46. Why Temperatures Vary: The Controls of Temperature
Other important controls
Altitude
Geographic position
Cloud cover
Albedo

47. Why Temperatures Vary: The Controls of Temperature

48. World Distribution of Temperature
Temperature maps
Temperatures are adjusted to sea level
January and July used for analysis
Represent temperature extremes

49. World Distribution of Temperature
Global temperature patterns
Temperature decreases poleward from tropics
Isotherms exhibit latitudinal shift with seasons
Warmest and coldest over land

50. World Distribution of Temperature

51. World Distribution of Temperature

52. World Distribution of Temperature
Global temperature patterns
Southern Hemisphere
Isotherms are straighter
Isotherms are more stable
Isotherms show ocean currents
Annual temperature range
Small near equator
Increases with an increase in latitude
Greatest over continental locations