1. Basic Properties of the Atmosphere

2. The Atmosphere: Structure and Temperature
Meteorology: the study of the physics, chemistry, and dynamics (movement) of the Earth’s atmosphere
Atmosphere: Envelope of gases bound to the Earth by gravity
Weather: State of the atmosphere at a given time and place; constantly changing
Weather is described by variables such as:
-- Temperature Wind Speed and Direction
-- Pressure -- Precipitation
-- Cloud Cover
Who is Stan Hatfield and Ken Pinzke

3. The Atmosphere: Structure and Temperature
Weather is constantly changing, and it refers to the state of the atmosphere at any given time and place.
Climate, however, is based on observations of weather that have been collected over many years. Climate helps describe a place or region.

4. Composition of the Atmosphere
Climatology: study of climate types and patterns and the causes of those patterns Climate: sum of all statistical weather info that helps describe a place or region Slowly - varying Averages (monthly, yearly) Ranges (largest value - smallest value) Extremes (maximum, minimum)

5. Weather or Climate???
The average high temperature for the month of July in Phoenix is 111oF.
Cumulus clouds presently cover the entire sky.
Snow is falling at a rate of 1 inch per hour.
The summers here are warm and humid.
At 3:00 p.m, winds were blowing from the NW at 10 mph.
Total precipitation at O’Hare Airport for was inches, which is 4.25 inches below normal.

6. Origin of the atmosphere
The original atmosphere
Probably made up of hydrogen and helium.
These are fairly common in the universe.
Original atmosphere stripped away by the solar wind
H and He are very light
Hydrogen and helium have the smallest atoms by mass.
The early earth was not protected by a magnetic field.
Thus the current atmosphere is considered a secondary atmosphere

7. The secondary atmosphere
Formed from degassing of volcanoes
Gasses emitted probably similar to the gasses emitted by volcanoes today.
H2O (water), 50-60%
CO2 (carbon dioxide), 24%
SO2 (sulfur dioxide), 13%
CO (carbon monoxide),
S2 (sulfur),
Cl2 (chlorine),
N2 (nitrogen),
H2 (hydrogen),
NH3 (ammonia) and
CH4 (methane)

8. Modern atmosphere Nitrogen (N2)- 78%, Oxygen (O2)- 21%,
Carbon Dioxide (CO2) %,
Where did all the oxygen come from?

9. Modern atmosphere Life changes the atmosphere
With the evolution of life the first cellular organisms began to use the gasses in the early atmosphere
NH3 – ammonia,
CH4 – methane,
H2O – water for energy.
Photosynthetic organisms evolve. (cyanobacteria)
These organisms use CO2 and produce oxygen (O2) as a waste product.

10. Modern atmosphere Where did the O2 come from? Where did the CO2 go?
Produced by photosynthetic life.
Where did the CO2 go?
Dissolves in water in the oceans
Used by life by photosynthesis and buried when plants and micro-organisms die.
The source of coal and oil

11. Atmosphere Characteristics
Permanent gases: Variable gases:
(together 99.96%)
(N) Nitrogen 78% (CO2) Carbon dioxide
(O) Oxygen 21% (O3) Ozone
(Ar) Argon ~ .9% (H2O) Water vapor -
Neon (Ne)( %)
Helium (He)( %)
Methane (CH4)( %)
Krypton (Kr)( %)
Hydrogen (H2)
varies from 4% to less than 1%
Green House Gases

12. Atmosphere Characteristics
 Variable Components
• Water vapor is the source of all clouds and precipitation. Like carbon dioxide, water vapor absorbs heat given off by Earth. It also absorbs some solar energy.
• Ozone is a form of oxygen that combines three oxygen atoms into each molecule (O3).
• If ozone did not filter most UV radiation and all of the sun’s UV rays reached the surface of Earth, our planet would be uninhabitable for many living organisms.

13. Atmospheric Structure
 The atmosphere rapidly thins as you travel away from Earth until there are too few gas molecules to detect.
Pressure Changes
• Atmospheric pressure is simply the weight of the air above.

14.  Pressure Changes

15.  Pressure Changes

16. Observing the Atmosphere
Air Pressure: force per area exerted by the mass of air above a point
Measured in:
Inches of mercury (in. Hg)
Millibars (mb)
Average sea-level pressure = mb or in. Hg
Air pressure is Measured using a barometer

17. Mercury Barometer Aneroid Barometers: (without liquid)
Barometer - apparatus used to measure pressure;  is derived from the Greek "baros" meaning "weight" 
Aneroid Barometers: (without liquid)

18. Air Pressure
By lucky coincidence, earth’s atmospheric pressure is approximately neat round numbers in metric terms
14.7 pounds per square inch (1 kg/cm2)
Pressure of ten meters of water
Approximately one bar or 100 kPa
Weather reports use millibars (mb)
One mb = pressure of one cm water

19. Atmospheric Pressure vs. Altitude
120
110
100 80 70 60 50 40 30 20 10 90
-120
-100
-80
-60
-40
-20
THERMOSPHERE
Mesopause
MESOPHERE
Stratopause
STRATOSPHERE
Tropopause
TROPOSPHERE
Height above ground (kilometers)
COLDER
WARMER
The atmosphere is divided into layers based on temperature.
Makes no sense without caption in book

20. Structure of the Atmosphere
Defined by Temperature Profiles
Troposphere
Where Weather Happens
Stratosphere
Ozone Layer
Mesosphere
Thermosphere
Ionosphere

21. Atmosphere Characteristics
 Temperature Changes
• The atmosphere can be divided vertically into four layers based on temperature.
• The troposphere is the bottom layer of the atmosphere where temperature decreases with an increase in altitude.
• The stratosphere is the layer of the atmosphere where temperature remains constant to a height of about 20 kilometers. It then begins a gradual increase until the stratopause.

22. Atmosphere Characteristics
 Temperature Changes
• The mesosphere is the layer of the atmosphere immediately above the stratosphere and is characterized by decreasing temperatures with height.
• The thermosphere is the region of the atmosphere immediately above the mesosphere and is characterized by increasing temperatures due to the absorption of very short-wave solar energy by oxygen.

23. Thermal Structure of the Atmosphere
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24. Heating the Atmosphere
Heat is the energy transferred from one object to another because of a difference in the objects’ temperature.
 Temperature is a measure of the average kinetic energy of the individual atoms or molecules in a substance.

25. Observing the Atmosphere
Temperature: measure of the motion of the molecules in a substance
Hot air: molecules moving more quickly
Cold air: molecules moving less quickly
Measured using a thermometer
Always measured in shady conditions
Units: oC, oF

26. Heat and Temperature
Temperature: Average energy of molecules or atoms in a material
Heat: Total energy of molecules or atoms in a material
Can have large amount of heat but low temperatures
Can have high temperatures but little heat

27. Heat and Temperature
The Arctic Ocean has a large amount of heat (because of large mass) even though the temperature is low.
Air in an oven at 500 F has high temperature but little heat.
However, touch anything solid in the oven, and you’ll get burned. Same temperature, much larger amount of heat.

28. Heat = total kinetic energy of atoms & molecules
HEAT & TEMPERATURE
Heat is a measure of energy.
Matter is composed of atoms & molecules that are constantly vibrating and
Heat = total kinetic energy of atoms & molecules
By contrast, Temperature is a measure of intensity.
Temperature = average kinetic energy of individual atoms and molecules. 
Heat and Temperature are of course closely related:
Add heat -> molecules move faster -> temperature rises
Remove heat -> molecules move slower -> temperature falls.

29. Temperature Scales Fahrenheit Centigrade or Celsius
Water Freezes at 32 F
Water Boils at 212 F
Centigrade or Celsius
Water Freezes at 0 C
Water Boils at 100 C
Two scales exactly equal at -40

30. Converting C to F – In Your Head
Double the Centigrade
Subtract the first Digit
Add 32
°C = (°F – 32) / 1.8

31. Converting F to C – In Your Head
Subtract 32
Add the first Digit
Divide by two
°F = 1.8 (°C) + 32

32. Absolute Temperature
Once atoms stop moving, that’s as cold as it can get
Absolute Zero = -273 C = -459 F
Kelvin scale uses Celsius degrees and starts at absolute zero
Most formulas involving temperature use the Kelvin Scale

33. Heating the Atmosphere
 Three mechanisms of energy transfer as heat are conduction, convection, and radiation.
 Conduction
• Conduction is the transfer of heat through matter by molecular activity.
 Convection
• Convection is the transfer of heat by mass movement or circulation within a substance.

34. Heating the Atmosphere
 Electromagnetic Waves
• The sun emits light and heat as well as the ultraviolet rays that cause a suntan. These forms of energy are only part of a large array of energy emitted by the sun, called the electromagnetic spectrum.

35. Visible Light Consists of an Array of Colors
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36. Heating the Atmosphere
 Radiation
• Radiation is the transfer of energy (heat) through space by electromagnetic waves that travel out in all directions.
• Unlike conduction and convection, which need material to travel through, radiant energy can travel through the vacuum of space.

37. Energy Transfer as Heat
VOCABULARY
radiation
conduction
convection
temperature
heat
troposphere
stratosphere
ozone
Makes no sense without caption in book
mesosphere
thermosphere
ionosphere
insolation

38. Heating the Atmosphere
 Radiation
• All objects, at any temperature, emit radiant energy.
• Hotter objects radiate more total energy per unit area than colder objects do.
• The hottest radiating bodies produce the shortest wavelengths of maximum radiation.
• Objects that are good absorbers of radiation are good emitters as well.

39. Heating the Atmosphere
 When radiation strikes an object, there usually are three different results.
1. Some energy is absorbed by the object.
2. Substances such as water and air are transparent to certain wavelengths of radiation.
3. Some radiation may bounce off the object without being absorbed or transmitted.

40. Heating the Atmosphere
 Reflection and Scattering
• Reflection occurs when light bounces off an object. Reflection radiation has the same intensity as incident radiation.
• Scattering produces a larger number of weaker rays that travel in different directions.

41. Heating the Atmosphere
 Absorption
• About 50 percent of the solar energy that strikes the top of the atmosphere reaches Earth’s surface and is absorbed.
• The greenhouse effect is the heating of Earth’s surface and atmosphere from solar radiation being absorbed and emitted by the atmosphere, mainly by water vapor and carbon dioxide.

42. changes Earth’s mean temperature.
SOLAR RADIATION
A total of 64 units radiated back into space via the atmosphere
6 units radiate to space from Earth’s surface
15 units radiate from surface to atmosphere
Conduction and convection
transfer 7 units to atmosphere
Evaporation
transfers
23 units to
atmosphere
100 units of Insolation
30 units reflected or scattered back to space
Atmosphere absorbs 19 units
Earth’s surface
absorbs 51 units
Earth’s heat budget represents the flow of energy into and out of Earth’s atmosphere.
An imbalance in
Earth’s heat budget
changes Earth’s mean temperature.

43. SOLAR RADIATION
About 50% of the incoming solar radiation is absorbed by the Earth’s surface. Most of the molecules in the Earth’s atmosphere do not absorb visible or shortwave radiation.
The Earth’s surface warms, and emits energy in the form of infrared or longwave radiation, which is invisible to the human eye.
Certain molecules in the atmosphere, called greenhouse gases, do absorb the Earth’s infrared radiation. This absorption warms the atmosphere.
Also, the greenhouse gas molecules emit their own infrared radiation, which is absorbed by other molecules, and the atmosphere warms even more!

44. Local Temperature Variations
Atmosphere
VOCABULARY
The intensity of insolation depends upon the angle at which sunlight strikes Earth’s surface. The intensity is greatest at low latitudes, during the summer, and around noon.
isotherm
A line drawn on a weather map through places having the same atmospheric temperature at a given time.
Equator
The angle of sunlight varies with latitude.

45. Tilt of Earth’s Axis Insolation:
The solar (energy) radiation that reaches Earth.
reaches Earth.
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**The Axial Tilt of the Earth is the cause of the seasons.

46. Tilt of Earth’s Axis
Altitude of sun affects amount of energy received at surface because
lower angle -> more spread out and less intense radiation
(as for flashlight beam).
lower angle -> more of atmosphere to pass through, and hence more chance to be absorbed or reflected
(can look at sun at sunset).

47. SUN’S
RAYS
New
Orleans
Equator
June 21
Dec. 21
During the summer, the Northern Hemisphere is tilted towards the Sun. Here, locations receive the Sun’s most direct rays, and have longer periods of daylight hours.
During the winter, the Northern Hemisphere is tilted away from the Sun. Periods of daylight are shorter, and the Sun’s rays are less direct.

48. Solstices and Equinoxes
During the vernal (spring) and autumnal (fall) equinoxes, neither hemisphere is tilted towards or away from the Sun. On these dates, every location on Earth receives 12 hours of daylight and 12 hours of darkness.
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49. Atmosphere Characteristics
 Solstices and Equinoxes
• The summer solstice is the solstice that occurs on June 21 or 22 in the Northern Hemisphere and is the “official” first day of summer.
• The winter solstice is the solstice that occurs on December 21 or 22 in the Northern Hemisphere and is the “official” first day of winter.

50. Atmosphere Characteristics
 Solstices and Equinoxes
• The autumnal equinox is the equinox that occurs on September 22 or 23 in the Northern Hemisphere.
• The spring equinox is the equinox that occurs on March 21 or 22 in the Northern Hemisphere.

51. Temperature Controls  Earth’s Motions  Earth’s Orientation
• Earth has two principal motions—rotation and revolution.
Rotation = 24 hours
Revolution = 365 days
 Earth’s Orientation
• Seasonal changes occur because Earth’s position relative to the sun continually changes as it travels along its orbit.

52. Temperature Controls Geographic Position Land and Water
 Factors other than latitude that exert a strong influence on temperature include heating of land and water, altitude, geographic position, cloud cover, and ocean currents.
Geographic Position
• The geographic setting can greatly influence temperatures experienced at a specific location.
Land and Water
• Land heats more rapidly and to higher temperatures than water. Land also cools more rapidly and to lower temperatures than water.

53. Temperature Controls What determines temperature?
Latitude: locations at lower latitudes typically experience higher temps year-round than higher latitude locations, because the lower latitudes receive more solar energy
Proximity to water: locations near water, especially a cool ocean current, have smaller annual temp ranges than landlocked locations
Elevation: locations at higher elevations (altitude) usually have cooler conditions than locations at lower elevations

54. The Effect of the Ocean on Annual Temperature

55. 17.3 Temperature Controls Why Temperatures Vary
 Cloud Cover and Albedo
• Albedo is the fraction of total radiation that is reflected by any surface.
• Many clouds have a high albedo and therefore reflect back to space a significant portion of the sunlight that strikes them.

56. Clouds Reflect and Absorb Radiation
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57. Clouds Reflect and Absorb Radiation
On Earth, water naturally occurs in all 3 phases or states of matter (gas, liquid, solid)
Clouds are composed of tiny liquid water droplets or tiny ice crystals.
Clouds are not made of water vapor (Otherwise, we wouldn’t be able to see them!)
In nature, clouds form when the temperature of air is lowered to its dewpoint temperature.

58. Electromagnetic Radiation
Radio: cm to km wavelength
Microwaves: 0.1 mm to cm
Infrared: to 0.1 mm
Visible light – mm
Ultraviolet 10-9 – 4 x 10-7 m
X-rays – 10-9 m
Gamma Rays –10-11 m

59. Troposphere Heating of the Surface creates warm air at surface
Warm air rises, but air expands as it rises and cools as it expands (Adiabatic cooling)
Heating + Adiabatic Cooling = Warm air at surface, cooler air above
Buoyancy = Cool air at surface, warmer air above
Two opposing tendencies = constant turnover

60. Stratosphere Altitude 11-50 km Temperature increases with altitude
-60 C at base to 0 C at top
Reason: absorption of solar energy to make ozone at upper levels (ozone layer)
Ozone (O3) is effective at absorbing solar ultraviolet radiation

61. Mesosphere 50 – 80 km altitude Temperature decreases with altitude
0 C at base, -95 C at top
Top is coldest region of atmosphere

62. Thermosphere 80 km and above
Temperature increases with altitude as atoms accelerated by solar radiation
-95 C at base to 100 C at 120 km
Heat content negligible
Traces of atmosphere to 1000 km
Formerly called Ionosphere

63. Why is the Mesosphere so Cold?
Stratosphere warmed because of ozone layer
Thermosphere warmed by atoms being accelerated by sunlight
Mesosphere is sandwiched between two warmer layers

64. Composition and Altitude
Up to about 80 km, atmospheric composition is uniform (troposphere, stratosphere, mesosphere)
This zone is called the homosphere
Above 80 km light atoms rise
This zone is sometimes called the heterosphere

65. Mean Free Path
Below 80 km, an atom accelerated by solar radiation will very soon hit another atom
Energy gets evenly distributed
Above 80 km atoms rarely hit other atoms
Light atoms get accelerated more and fly higher
Few atoms escape entirely

66. Planets and Atmospheres
At top of atmosphere, an atom behaves like any ballistic object
Velocity increases with temperature
If velocity exceeds escape velocity, atom or molecule escapes
Earth escape velocity 11 km/sec.
Moon escape velocity 2.4 km/sec

67. Atmospheric Measurements
Temperature
Pressure
Humidity
Wind Velocity and Direction

68. Weather Instruments Temperature: Thermometer Pressure: Barometer
Humidity: Hygrometer
Wind Velocity and Direction:
Anemometer and Wind Vane

69. Thermometers Fluid Bimetallic Electronic Mercury Alcohol
Use expansion of fluid
Bimetallic
Differential expansion of different metals
Electronic
Electrical resistance change with temperature

70. Barometers Mercury Aneroid
Air pressure will support 10 meters of water
Mercury is 13 times denser
Air pressure will support 76 cm of mercury
Aneroid
Air pressure deforms an evacuated chamber

71. Hygrometers Filament Sling Psychrometer Electrical
Hair expands and contracts with humidity
Sling Psychrometer
Measures cooling by evaporation
Two thermometers
Wet bulb and Dry bulb
Electrical
Chemicals change resistance as they absorb moisture

72. Sounding Balloons carry radiosondes
Thermometer
Barometer
Hygrometer
Transmitter
Typically reach 30 km before balloon breaks

73. Radar Detect precipitation types and amounts
Doppler radar measures velocity of winds

74. Satellite Studies
Visual imagery
Infrared imagery
Laser spectroscopy

75. Earth’s Radiation Budget
What comes in must go out
Direct Reflectance (Short Wave)
31%
Infrared Re-emission (Long Wave)
69%

76. How Heat Moves
Radiation
Conduction
Convection

77. Albedo Albedo = % incident energy reflected by a body
Fresh snow: 75 – 95%
Old snow: 40 – 60%
Desert: 25 – 30%
Deciduous forest, grassland: 15 – 20%
Conifer forest: 5 – 15%
Camera light meters set to 18%

78. Global Albedo