1. Chapter 11 Heating the Atmosphere

2. Earth’s Unique Atmosphere
No other planet in our solar system has an atmosphere with the exact mixture of gases or the heat and moisture conditions necessary to sustain life as we know it.

3. Introduction of Weather
Weather influences our everyday activities, our jobs, and our health and comfort.
Many of us pay little attention to the weather unless we are inconvenienced by it or when it adds to our enjoyment outdoors.

4. Weather Continued (Severe weather events)
United States has the greatest variety of weather of any country in the world.
Tornadoes
Flash Floods
Intense Thunderstorms
Hurricanes
Blizzards

5. Weather and Climate Weather Climate
Weather is over a short period of time
Constantly changing
Climate
Climate is over a long period of time
Generalized, composite of weather

6. Weather and Climate Elements of weather and climate
Properties that are measured regularly
Most important elements
Temperature
Humidity
Cloudiness
Precipitation
Air Pressure
Winds speed and direction

7. Composition of the Atmosphere
Air is a mixture of discrete gases
Major components of clean, dry air
Nitrogen (N)—78%
Oxygen (O2)—21%
Argon and other gases
Carbon dioxide (CO2)—0.036%—absorbs heat energy from Earth

8. Composition of Dry Air

9. Composition of the Atmosphere
Variable components of air
Water vapor
Up to about 4% of the air's volume
Forms clouds and precipitation
Absorbs heat energy from Earth
Aerosols
Tiny solid and liquid particles
Water vapor can condense on solids
Reflect sunlight
Help color sunrise and sunset

10. Composition of the Atmosphere
Variable components of air
Ozone
Three atoms of oxygen (O3)
Distribution not uniform
Concentrated between 10 to 50 kilometers above the surface
Absorbs harmful UV radiation
Human activity is depleting ozone by adding chlorofluorocarbons (CFCs)

11. Chlorofluorocarbons (CFCs)
Over the past half century, people have unintentionally placed the ozone layer in jeopardy by polluting the atmosphere.
Many uses developed for CFCs
Coolants for AC
Refrigeration equipment
Cleaning solvents for electronic components and comp. chips
Propellants for aerosol sprays

12. Characteristics of CFCs
Practically inert, not chemically active in the lower atmosphere
Gradually make their way to the ozone layer
Sunlight separates the chemicals into their constituent atoms
Chlorine atoms released, breaking up some of the ozone molecules

13. Importance of Ozone
Ozone filters out most of the UV radiation from the Sun
Decreased concentration allows more of these harmful wavelengths to reach Earth’s surface
Increase risks of skin cancer
Impair the human immune system
Promote cataracts, clouding of the eye lens that reduces vision. May cause blindness if not treated
Montreal Protocol was developed under the sponsorship of the UN to eliminate the production and use of CFCs

15. Structure of the Atmosphere
Pressure changes
Atmospheric Pressure is the weight of the air above
Average sea level pressure
Slightly more than 1000 millibars
About 14.7 pounds per square inch
Pressure decreases with altitude
One half of the atmosphere is below 3.5 miles (5.6 km)
Ninety percent of the atmosphere is below 10 miles (16 km)

16. Atmospheric Pressure Variation with Altitude
Figure 11.5

17. Structure of the Atmosphere
Atmospheric layers based on temperature
Troposphere
Bottom layer, where all weather phenomena occur
Temperature decreases with altitude—Called the environmental lapse rate
6.5˚C per kilometer (average)
3.5˚F per 1000 feet (average)
Thickness varies with latitude and season—Average height is about 12 km
Outer boundary is named the tropopause

19. Structure of the Atmosphere
Atmospheric layers based on temperature
Stratosphere
About 12 km to 50 km
Temperature increases at top due to ozone absorbing UV radiation from the sun
Outer boundary is named the stratopause
Mesosphere
About 50 km to 80 km
Temperature decreases
Outer boundary is named the mesopause

20. Structure of the Atmosphere
Atmospheric layers based on temperature
Thermosphere
No well-defined upper limit
Fraction of atmosphere's mass
Gases moving at high speeds

21. Temperatures in the Thermosphere
Increases with altitude, absorption of very shortwave high-energy solar radiation by atoms of oxygen and nitrogen
Rising to extreme values of more than 1000 degrees Celsius
Temperature is defined in term of average speed at which molecules move
Sparse amount of gases = insignificant quantity of heat

22. Thermal Structure of the Atmosphere
Figure 11.7

23. Earth–Sun Relations Earth’s two principal motions Seasons
Rotates on its axis, an imaginary line running through the poles
One rotation/24 Hrs.
Cycle of daylight and darkness
Revolves around the Sun
Hundred years ago, most people believed Earth was stationary, Sun/stars revolved around Earth
Fact: Traveling at more than 107,000 km/hr orbiting about the sun
Seasons
Result of
Changing Sun angle
Changing length of daylight

24. Seasons Result of Changing Sun angle Changing length of daylight
At around 90 degrees angle, the solar rays are more concentrated
At a lesser angle, the solar rays are more spread out, and therefore less intense solar radiation that reaches the surface
Thickness of atmosphere, lower the angle, the more distance the rays have to penetrate
The longer the path, the greater the chances that sunlight will be absorbed, reflected, or scattered by the atmosphere, reduce intensity at the surface
Changing length of daylight
Longer the day, the more solar radiation the Earth takes in

25. Daily Paths of the Sun at 40° N latitude—June
Figure 11.9 A

26. Daily paths of the Sun at 40° N latitude—December
Figure 11.9 B

27. Relationship of Sun Angle and Intensity of Solar Radiation
Figure 11.10

28. Earth–Sun Relations Seasons
Caused by Earth's changing orientation to the Sun
Axis is inclined 23½°
Axis is always pointed in the same direction
Special days (Northern Hemisphere)
Summer solstice
June 21–22
Sun's vertical rays are located at the tropic of Cancer (23½° N latitude)

29. Earth–Sun relations Seasons Special days (Northern Hemisphere)
Winter solstice
December 21–22
Sun's vertical rays are located at the tropic of Capricorn (23½° S latitude)
Autumnal equinox
September 22–23
Sun's vertical rays are located at the equator (0° latitude)

30. Earth–Sun relations Seasons Special days (Northern Hemisphere)
Spring equinox
March 21–22
Sun's vertical rays are located at the equator (0° latitude)

31. Earth–Sun Relationships

32. Characteristics of the Solstices and Equinoxes

33. Atmospheric Heating
Heat is always transferred from warmer to cooler objects
Mechanisms of heat transfer
Conduction through molecular activity
Convection
Mass movement within a substance
Radiation (electromagnetic radiation)
Velocity: 300,000 kilometers (186,000 miles) per second in a vacuum

34. Conduction Transfer of heat through matter by molecular activity
Energy of molecules is transferred through collisions from one molecule to another, heat flowing from high to low temp.
Metals are good conductors
Air is a very poor conductor of heat
Conduction is the least significant of the three as a means of heat transfer for the atmosphere

35. Convection
Most of the heat transport that occurs in the atmosphere is carried on by convection.
Def: The transfer of heat by mass movement or circulation within a substance
Takes place in fluids (oceans, air) where atoms and molecules are free to move about
Pan example:
Warmer water rises, cooler water sinks
Uneven heating of water, from the bottom up
Water will continue to “turn over”, producing a convective circulation

36. Radiation Travels in all directions from its source
Travels through the vacuum of space, does not need medium like the other two
Radiation is the heat-transfer mechanism by which solar energy reaches our planet

37. Mechanisms of Heat Transfer
Figure 11.14

38. Atmospheric Heating Mechanisms of heat transfer
Radiation (electromagnetic radiation)
Consists of different wavelengths (distance from one crest to the next)
Gamma (very short waves)
X-rays
Ultraviolet (UV)
Visible
The only portion of the spectrum we can see
White Light as a mixture of colors, each corresponding to a particular wavelength seen through a prism
Infrared (detected as heat)
Microwaves and radio waves (longest)

39. The Electromagnetic Spectrum
Figure 11.15

40. Atmospheric Heating Mechanisms of heat transfer
Radiation (electromagnetic radiation)
Governed by basic laws
Hotter objects radiate more total energy per unit area than do cooler objects
The hotter the radiating body, the shorter the wavelength of maximum radiation
Objects that are good absorbers of radiation are good emitters as well

41. Atmospheric Heating 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

43. Average Distribution of Incoming Solar Radiation
Figure 11.17

44. Atmospheric Heating Radiation from Earth's surface
Earth re-radiates radiation (terrestrial radiation) at the longer wavelengths
Longer wavelength 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

45. Greenhouse effect
Approx. 50% of the solar energy that strikes the top of the atmosphere reaches Earth’s surface and is absorbed
Most of this energy is then reradiated skyward
The radiation that it emits has longer wavelengths than solar radiation (terrestrial radiation)
The atmosphere is an efficient absorber of this type of radiation (85% absorbed)
Water vapor and CO2 are the principal absorbing gases
The absorbed terrestrial radiation is then reradiated back to Earth
Atmosphere acts like a real Greenhouse (with windows open)

46. Heating of the Atmosphere
Figure 11.19

47. Global Warming
Carbon dioxide in the atmosphere absorbs some of the radiation emitted by Earth and thus contributes to the greenhouse effect
Changes in content of CO2 could influence air temperature
Rapid growth of industrialization, burning of fossil fuels has added vast quantities of CO2 to the atmosphere
The clearing of forests also contributes substantially. Carbon dioxide is released as vegetation is burned or decays

50. Consequences of Global Warming?
Probable rise in sea level?
Shifts in the paths of large-scale storms, affecting the distribution of precipitation and the occurrence of severe weather
Stronger tropical storms
Increases in the frequency and intensity of heat waves and droughts
Gradual environmental shift, imperceptible to public. Nevertheless will have a strong impact on future economics and thus leading to social and political consequences.

52. Temperature Measurement
Daily maximum and minimum
Other measurements
Daily mean temperature
Daily range
Monthly mean
Annual mean
Annual temperature range

53. Controls of Temperature
Temperature variations
Receipt of solar radiation is the most important control
Other important controls
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

54. Maritime Influence on Temperature
Figure 11.23

55. Controls of Temperature
Other important controls
Altitude
Geographic position
Cloud cover
Albedo

56. Clouds Reduce the Daily Temperature Range
Figure 11.27

57. World Distribution of Temperature
Temperature maps
Isotherm—A line connecting places of equal temperature
Temperatures are adjusted to sea level
January and July are used for analysis because they represent the temperature extremes

58. World Distribution of Temperature
Global temperature patterns
Temperature decreases poleward from the tropics
Isotherms exhibit a latitudinal shift with the seasons
Warmest and coldest temperatures occur over land

59. World Distribution of Temperature
Global temperature patterns
In the 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

60. World Mean Sea-Level Temperatures in January
Figure 11.28

61. World Mean Sea-Level Temperatures in July
Figure 11.29

62. End of Chapter 11