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Chapter 3: Introduction to the Atmosphere. Image courtesy of cimss.ssec.wisc.edu. Importance of Earth’s Atmosphere. Provides oxygen Weather (short-term) & Climate (long-term) Protection from UV radiation & meteors Temperature Control Water (hydrologic cycle). - PowerPoint PPT Presentation
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Chapter 3: Introduction to the Atmosphere
Image courtesy of cimss.ssec.wisc.edu
Importance of Earth’s Atmosphere
• Provides oxygen• Weather (short-term) & Climate (long-term)• Protection from
UV radiation & meteors
• Temperature Control
• Water (hydrologic cycle)
Size of Earth’s Atmosphere
• Atmosphere uniformly surrounds Earth
• Held down by Earth’s gravity
• Extends up to 10,000 km from the surface
• More than 50% of the total mass is below 6 km
Figure 3-2
Composition of the Atmosphere
• Two primary gas types– Permanent
• Oxygen & Nitrogen• Neither plays a major role in
atmospheric processes– Variable
• Water Vapor• Carbon Dioxide• Ozone• Play significant role in weather &
climate
• Permanent gases make up over 95% of total atmosphere
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• Amount of water vapor in the atmosphere varies from 0-4%
• Water vapor transports heat & regulates temperature
-180 -120 -60 0 60 120 180
-90
-60
-30
0
30
60
90
0 10 20 30 40 50Precipitable Water (kg/m2)
Water Vapor in the Atmosphere
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• Carbon dioxide also regulates temperature
• Amount of atmospheric CO2 is about 0.039%, but it’s rising– Greenhouse Effect
Carbon Dioxide in the Atmosphere
Composition of the Atmosphere
• Particulates– Non-gaseous particles which exist in the atmosphere– Human-induced & natural types– Some are hygroscopic– Some reflect
or absorb sunlight
Figure 3-4
Vertical Structure of the Atmosphere
• Thermal Layers (temp. alternates from one layer to the next)
• “Sphere” = entire layer• “Pause” = upper boundary of a layer
– Troposphere—lowest layer; weather occurs here; tropopause
• Thickest at Equator & thinnest at Poles due to the Earth’s rotation & convection
– Stratosphere—stagnant air; ozone layer; stratopause
– Mesosphere—middle of atmosphere; meteors burn up; mesopause
– Thermosphere—“heat”– Exosphere—transitions into space
Figure 3-5
Vertical Structure of
the Atmosphere
• Air Pressure– “Weight” of the air– Decreases with height
at non-constant rate– Low-levels compressed
by air above, so surface pressure is higher
– 90% of atmosphere is in lowest 16 km
Figures 3-7 & 3-8
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Measuring Atmospheric Pressure
Vertical Structure of the Atmosphere
• Composition– Homosphere—
uniformly mixed– Heterosphere—
layered– Ozonophere—AKA
ozone layer; high concentration of O3
– Ionsophere—electrically charged ions; source of auroras
Figure 3-9
• Natural Ozone (O3)– Naturally produced by UV radiation to shield us from UV radiation
• Introduction of impurities into the atmosphere at rapid pace• Received international attention in recent years
Figure 3-11
Depletion of the Ozone Layer
Depletion of the Ozone Layer
• Chemistry of Ozone Layer depletion– Reduction/destruction of ozone
by CFCs• The “Hole” in the Ozone layer• Mainly affects polar regions
Figure 3-12Figure 3-13
Human-Induced Atmospheric Change
• Primary vs. secondary pollutants
• Primary pollutants– Particulates– Carbon monoxide– Nitrogen compounds– Sulfur compounds
• Secondary pollutants– Photochemical smog– Ozone
Figure 3-15: Santiago, Chile Smog
Los Angeles, CA Smog
Weather and Climate
• Weather—short-term atmospheric conditions for a specific area– Meteorology
• Climate—aggregate long-term weather conditions– Climatology
• Weather vs. climate
• Latitude is the most important/significant control of weather and climate– Heat received across Earth’s surface from sunlight is a
function of latitude
Weather & Climate: Latitude
Figure 3-16
Weather & Climate: Distribution of Land & Water
• Distinction between maritime & continental climates– Dallas, TX, & San Diego, CA,
have very different climates– Maritime climates = humid
Continental climates = dry• N. (Land) Hemisphere vs. S.
(Water) Hemisphere
Figure 4-24
Weather & Climate: General Circulation of the Atmopshere &
Oceans• General circulation of
the atmosphere– Semipermanent wind
pattern on Earth– Varies with latitude
• General circulation of the oceans– Oceanic broad-scale
semi-permanent motions
– Help transfer heat Figure 3-17
Weather & Climate: Altitude & Topography
• Altitude– All 4 controls of
weather and climate affected by altitude
• Topographic barriers– Can drastically alter
climate due to orographic change in wind patterns
– Windward side vs. Leeward side
Figure 3-20
Weather & Climate: Storms
• Storms– Control weather & climate through atmospheric modification – Some storms are prominent enough to affect climate
Figure 3-21
Weather and Climate
• Coriolis effect– Rotation of Earth modifies path of forward motion of free-
moving objects over great distances– Curves to the right in the N Hemisphere– Curves to the left in the S Hemisphere– Deflection greatest at the poles; zero at the equator– Proportional to
speed of the object– Only influences
direction of an object; no influence on speed of an object
Weather and Climate
• Coriolis effectFigure 3-22
Summary
• Earth’s atmosphere is a shallow “ocean” of air that uniformly surrounds the Earth• The atmosphere consists of many permanent and variable gases• The gas with the highest concentration in Earth’s atmosphere is nitrogen (78%)• The atmosphere has various vertical structures that describe it• Five main spheres make up the thermal atmosphere• The homosphere and heterosphere describe the gas composition of the
atmosphere at different heights• Most auroral activity occurs in the ionosphere• Human activity has modified the atmospheric composition through pollution and
ozone depletion• Weather and climate, while related, involve atmospheric conditions on different
time scales• Many controls exist that modify the four primary weather elements• The Coriolis effect is an apparent force that exists due to the rotation of Earth