Transcript Atmosphere

Atmosphere
Space Ice
• The original stellar nebula included water.
– Icy grains in protoplanets
• Half of Earth’s water from came from before the Sun.
Bill Saxton/NSF/AUI/NRAO
Oceans
• Oceans formed from
gasses trapped in rocks
and collisions from
protoplanets.
• Surface water covers 75%
of Earth.
– Hydrosphere
Layers of Air
• The ionosphere includes
gases broken into ions: 80150 km.
• The mesosphere has falling
temperatures with height:
50-80 km.
• The stratosphere is a stable
layer of gas: 15-50 km.
• The troposphere is a dense,
turbulent layer: up to 15 km
high.
Blue Sky
• Air scatters high
frequency light more than
low frequency light.
– Blue light higher
frequency than red
– Black when no scattered
light at night
• Dust and water increase
the scattering – less blue.
 Composition of Earth’s
atmosphere:
 78.08% Nitrogen (N2)
 20.95% Oxygen (O2)
 0-4% Water (H2O)
 0.93% Argon (Ar)
 0.04% Carbon Dioxide
(CO2)
Greenhouse Effect
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The atmosphere only permits visible light and radio waves.
Visible light warms the surface.
The surface absorbs visible light and radiates infrared.
The infrared is trapped and warms the air.
visible
light
atmosphere
infrared
light
earth
Weather
• Planetary motion drives
the weather.
– Seasons from orbit
– Day-night temperature
– Wind circulation
• Weather is confined to the
troposphere.
NOAA – January, 2014
Ozone
• High frequency UV light
forms ozone from oxygen.
– Stratosphere, mesophere
• Ozone concentrates in a
layer in the stratosphere.
– Opaque to UV-B
– Dissolved by CFCs
NASA
Magnetic Field
• The moving iron in the core creates a magnetic field.
• The magnetic field extends hundreds of kilometers above
the surface.
• Particles from the sun are deflected by the field.
solar wind
earth
Aurora
• Charged particles from the sun can be trapped in the
magnetic field.
– Concentrated at the poles
– Air glows as an aurora
NASA, S. Vetter; aurora over Iceland