AOSC Lesson 2

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AOSCLesson 2
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Temperature Scales

• Temperature scales are defined by upper and lower
  calibration points (fixed points)
• In the Fahrenheit temperature scale the lower
  fixed point of 0F is defined as the temperature
  of a mixture of salt and ice.
• Dr. Fahrenheit was a physician, and he defined
  the upper fixed point, 100F, as the average
  temperature of his (sick?) patients.
• In the Centigrade (Celsius) scale, the lower
  fixed point, 0C, is defined as the temperature
  of the melting point of ice, while the upper
  fixed point, 100C, is defined as the boiling
  point of water.
• The Kelvin scale is a scientific scale. Here the
  lowest fixed point 0K is defined as the
  theoretically lowest temperature that can be
  reached. On this scale the melting point of ice
  is about 273K. One degree K one degree C.

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Fig. 2-1, p. 29
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Specific Heat
Table 2-1, p. 30
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How is energy transferred in the atmosphere?

• Tornados, Hurricanes, Severe Storms all require a
  large energy source.
• All of this energy comes from the Sun.
• So, how is this energy transferred within the
  atmosphere?
• Five major processes,
• (1) conduction
• (2) convection
• (3) advection
• (4) transfer of radiation
• (5) latent heat of vaporization of water

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CONDUCTION
Fig. 2-2, p. 30
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CONVECTION
Fig. 2-3, p. 31
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ADVECTION
Fig. 2-4, p. 31
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Transfer of Energy in the Atmosphere

• CONDUCTION
• TRANSFER OF ENERGY THROUGH MATTER
• AIR IS A POOR CONDUCTOR
• ONLY IMPORTANT AT THE EARTH'S SURFACE
• CONVECTION
• TRANSFER OF ENERGY BY MOVEMENT OF MASS
• CAN ONLY TAKE PLACE IN LIQUIDS IN
  SCIENTIFIC TERMS AIR IS A LIQUID.
• ENERGY ACQUIRED AT SURFACE OF EARTH IS
  TRANSPORTED UPWARD BY CONVECTIVE FLOW
• CONVECTION ON A GLOBAL SCALE CREATES
  WORLDWIDE ATMOSPHERIC CIRCULATION
• ADVECTION
• HORIZONTAL MOVEMENT OF AIR

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PHASE CHANGES OF WATER
Fig. 2-5, p. 33
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Latent heat Changing the Phase of Water

• LATENT HEAT IS THE HEAT ABSORBED OR RELEASED BY
  UNIT MASS OF WATER WHEN IT CHANGES PHASE.
• LATENT HEAT OF MELTING / FUSION
• LATENT OF VAPORIZATION / CONDENSATION
• LATENT HEAT OF SUBLIMATION / DEPOSITION
• THIS GIVES US ANOTHER WAY OF TRANSFERRING ENERGY
  IN THE ATMOSPHERE
• THE OCEANS ABSORB SOLAR ENERGY TO EVAPORATE WATER
  VAPOR.
• THE WATER VAPOR IS TRANSPORTED BY WINDS ETC
• WHEN THE WATER VAPOR CONDENSES TO FORM CLOUDS THE
  LATENT HEAT IS RELEASED.
• THE LATENT HEAT RELEASED IS THE SOURCE OF ENERGY
  THAT DRIVES SEVERE WEATHER, E.G. HURRICANES.

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Radiation
Energy is transferred to the Earth from the sum
by electromagnetic waves. Other examples of
electromagnetic waves are microwave and radio
waves.
Each wave is characterized by a wavelength(the
distance between successive peaks) and a
frequency ( the number of peaks that pass by per
second)
Fig. 2-6, p. 34
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ELECTROMAGNETIC SPECTRUM
Fig. 2-7, p. 34
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Laws of Radiation
Wiens Displacement Law
Stephan-Boltzmann Law
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All things emit thermal radiation. This is a
picture of a person holding a match. It was taken
with a camera sensitive to infrared radiation.
Fig. 2.11
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Note that the peak of the Earths radiation
occurs at 10 ?m while that for then sun is at 0.5
?m, a ratio of 20. The ratio of the temperatures
is 1/20. (Wiens Displacement Law)
Fig. 2-8, p. 36
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• SEVERAL QUESTIONS
• WHY DOES THE EARTH HAVE SEASONS?
• WHY ARE THE POLES COLD YET THE EQUATOR IS HOT?
• WHY IS DAYLIGHT LONGER IN THE SUMMER THAN IN THE
  WINTER?

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Fig. 2-14, p. 43
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Fig. 2-11, p. 41
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HEATING OF THE EARTHS SURFACE DEPENDS ON THE
AMOUNT OF SOLAR RADIATION PER UNIT AREA. SAME
AMOUNT OF RADIATION IS DISTRIBUTED OVER A LARGER
AREA IN A THAN IN B. RADIATION PER UNIT AREA IS
LESS IN A THAN IN B. LESS HEATING IN A THAN IN B.
Fig. 2-12, p. 42
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Fig. 2.15
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• Fig. 2-15, p. 43

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• Fig. 2-16, p. 44

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• Table 2-2, p. 44

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• Fig. 2-17, p. 45

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http//www.youtube.com/watch?vDuiQvPLWziQ http//
www.youtube.com/watch?vDuiQvPLWziQ
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The Earths Orientation

• EARTH'S AXIS IS NOT PERPENDICULAR TO THE PLANE OF
  ITS ORBIT AROUND THE SUN.
• IT IS TILTED 23.5 DEGREES FROM THE PERPENDICULAR
• INCLINATION OF THE AXIS.
• WITHOUT THIS INCLINATION WE WOULD HAVE NO
  SEASONS.
• THIS CHANGES THE SOLAR ZENITH ANGLE OF THE SUN,
  AND THE AREA COVERED BY A BEAM OF SUNLIGHT
• AREA COVERED BY BEAM IS PROPORTIONAL TO 1/COS OF
  THE SOLAR ZENITH ANGLE
• IN COLLEGE PARK, SOLAR ZENITH ANGLE OF THE SUN IS
  67 DEGREES ON DEC 22, AND 19 DEGREES ON JUNE 22.
  THE RATIO OF 1/COS OF THE ANGLES IS ABOUT 2.
  TWICE AS MUCH ENERGY FALLS ON UNIT AREA AT THE
  GROUND IN SUMMER THAN IN WINTER.
• THE LENGTH OF THE DAY ALSO VARIES WITH SEASON
  ALSO A RESULT OF THE INCLINATION OF THE EARTH.

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• Fig. 2-19, p. 49

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Incoming Solar Radiation

• 25 PENETRATES DIRECTLY TO EARTH'S SURFACE.
• 26 SCATTERED BY ATMOSPHERE BUT THEN REACHES THE
  SURFACE.
• TOTAL OF 51 REACHES SURFACE.
• 31 REFLECTED BACK TO SPACE BY CLOUDS,
  ATMOSPHERIC SCATTERING, AND REFLECTIVE SURFACES,
  E.G. SNOW AND ICE.
• 19 ABSORBED BY CLOUDS AND ATMOSPHERIC GASES

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Absorption

• GASES ARE EXCELLENT ABSORBERS.
• WHEN RADIATION IS ABSORBED, ENERGY IS CONVERTED
  INTO INTERNAL MOLECULAR MOTION - RISE OF
  TEMPERATURE.
• SIGNIFICANT ABSORBERS ARE
• OXYGEN AND OZONE
• WATER VAPOR

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Reflection

• THE FRACTION OF ENERGY THAT IS REFLECTED BY A
  SURFACE IS CALLED ITS ALBEDO.
• ALBEDO OF THE EARTH AS A WHOLE IS 30.
• ALBEDO OF FRESH SNOW IS 80-85
• THICK CLOUD - 70 TO 80
• WATER - DEPENDS ON ELEVATION OF THE SUN, FROM 50
  TO 80 NEAR HORIZON, 3-5 AT 90 DEGREES.
• SOIL- 10

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Scattering

• PRODUCES DIFFUSE LIGHT
• SHORTER WAVELENGTHS (BLUE AND VIOLET) ARE
  SCATTERED MORE EFFECTIVELY THAN LONGER
  WAVELENGTHS (RED AND ORANGE).
• HENCE SKY APPEARS BLUE WHEN VIEWED AT NOON.
• AT SUNSET PREFERENTIALLY SCATTERING DEPLETES
  AMOUNT OF BLUE LIGHT IN DIRECT BEAM - BEAM
  APPEARS REDDISH.
• SCATTERING MORE EFFICIENT AS PARTICLE GETS LARGER
  - AEROSOLS OR DUST.

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• Fig. 2-20, p. 50

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Latitudinal Heat Balance

• FOR THE GLOBE AS A WHOLE, THE AMOUNT OF INCOMING
  SOLAR RADIATION IS EQUAL TO THE OUTGOING
  TERRESTRIAL RADIATION.
• HOWEVER THIS STATEMENT DOES NOT HOLD TRUE AT ANY
  GIVEN LATITUDE
• IN GENERAL THERE IS A SURPLUS OF ENERGY AT THE
  EQUATOR - MORE RADIATION COMES IN THAN GOES OUT
• THERE IS ALSO A DEFICIT OF ENERGY AT THE POLES
  MORE RADIATION GOES OUT THAN COMES IN.
• WHY THEN DO THE POLES NOT GET COLDER AND THE
  EQUATOR HOTTER?
• BECAUSE HEAT IS TRANSPORTED FROM THE EQUATOR TO
  THE POLES BY OCEAN CURRENTS (E.G. THE GULF
  STREAM) AND BY THE ATMOSPHERE.

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• http//www.youtube.com/watch?vCxUK2TizQ4g
• http//www.youtube.com/watch?vCxUK2TizQ4g

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Simple Greenhouse Model
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• Fig. 3-2, p. 55

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Greenhouse Effect
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Greenhouse Effect
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Greenhouse Effect
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• The Blue Marble