Review Question 1

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Review Question 1

• When is the subsolar point directly over 20N
  latitude?
• A) Never
• B) Between the summer solstice and the fall
  equinox
• C) Between the spring equinox and the summer
  solstice
• D) B and C

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Review Question 2

• Why is Pluto no longer considered a planet?
• A) Because it is square
• B) Because it is a thermonuclear reactor
• C) Because it shares its orbit with another
  planet
• D) Because it is 3 billion light years from the
  sun

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Chapter 3Earths Modern Atmosphere

• Geosystems 6e
• An Introduction to Physical Geography

Robert W. Christopherson Charles E. Thomsen
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The Atmosphere

• Atmosphere an envelop of gaseous mixture (also
  containing suspended solid and liquid particles
  and clouds) that encircles a planet

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Earths Modern Atmosphere

• The atmosphere is absolutely essential for life
  on Earth
• Earths atmosphere exists in a series of spheres
  or layers that grade into one another  
• Composition, temperature, and function  

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Atmospheric Profile  

• Our atmosphere extends to roughly 32,000 km
  (20,000 mi) from surface
• The top of the atmosphere has no clear boundary
• Gravity holds our atmosphere in place
• Top of Thermosphere is at 480 km (300 mi) top
  of the principle atmosphere
• Exosphere

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Atmospheric Composition

• Two broad regions
• Heterosphere outer atmosphere
• 80 km (50 mi) outwards, to top of thermosphere
• Layers of gases sorted by gravity
• Homosphere inner atmosphere
• Surface to 80 km (50 mi)
• Gases evenly blended
• Ozone layer

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Atmospheric Pressure
Figure 3.3
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Atmospheric Temperature
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Atmospheric Temperature

• Troposphere
• Surface to 18 km (11 mi)
• 90 mass of atmosphere
• Normal lapse rate average cooling at rate of
  6.4 C / km (3.5 F/1000 ft)
• Tropopause

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Temperature Profile
Figure 3.5
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Atmospheric Temperature

• Stratosphere
• 18 to 50 km (11 to 31 mi)
• Temperatures increase with altitude
• Ozone layer
• Stratopause

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Atmospheric Temperature

• Mesosphere
• Temperatures decrease with altitude
• Mesopause

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Atmospheric Temperature

• Thermosphere
• Roughly same as heterosphere
• 80 km (50 mi) outwards
• Altitude of thermopause varies
• Temperatures increase with altitude, but little
  actual heat

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Atmospheric Function

• Ionosphere
• Absorbs cosmic rays, gamma rays, X-rays, some UV
  rays
• Ozonosphere
• Part of stratosphere
• Ozone (O3) absorbs UV energy and converts it to
  heat energy

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Protective Atmosphere
Figure 3.6
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Four Principal Components of Atmosphere

• Nitrogen from volcanic sources
• Oxygen from photosynthesis
• Argon through radioactive decay of isotopes
• Carbon dioxide byproduct of life processes

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Composition of the Atmosphere
Atmospheric gases
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Water Vapor

• The most abundant variable gas (0.25 of total
  atmospheric mass).

• Added and removed from the atmosphere through the
  hydrologic cycle.

• A major contributor to Earths energy balance and
  many important atmospheric processes.

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Carbon Dioxide

• A trace gas accounting for only 0.037 of the
  atmosphere.

• Added to the atmosphere through biologic
  respiration and decay, volcanic eruptions, and
  natural and human-related combustion.

• Removed from the atmosphere by photosynthesis (go
  to biosphere).

• Anthropogenically related increases in recent
  decades have led to great concern with regard to
  global greenhouse warming.

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Carbon Dioxide
Question the seasonal variation?
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Methane

• 1.7 ppm increase 0.01 ppm/yr.

• Released to the atmosphere through fossil fuel
  activities, livestock digestion, and agriculture
  cultivation (especially rice).

• An extremely effective absorber of thermal
  radiation emitted by Earths surface hence
  related in the warming of the atmosphere.

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Carbon

• Carbon Sequestration removing carbon in the
  form of carbon dioxide from the atmosphere and
  storing it in the terrestrial biosphere
• Carbon stored in biomass of plants
• Soil organic carbon is carbon retained by the
  soil in humus form

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The Carbon Cycle- source of atmospheric carbon
dioxide

• Human acitivities release 7.1 GtC/yr (gigatons of
  Carbon per year).
• 2 GtC/yr absorbed by oceans.
• 1.9 GtC unaccounted for.
• 3.2 GtC remain in atmosphere.

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Carbon Banks

• Carbon bank program that enables organizations
  to keep track of a stock or supply of greenhouse
  gases in secure fashion for future use in the
  trading market
• www.icbe.com