Basic Properties of the Atmosphere. Composition of the Atmosphere Nitrogen (78.08% ~ 78%) Oxygen...
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Transcript of Basic Properties of the Atmosphere. Composition of the Atmosphere Nitrogen (78.08% ~ 78%) Oxygen...
Basic Properties of the Atmosphere
Composition of the Atmosphere• Nitrogen (78.08% ~ 78%)
• Oxygen (20.95% ~ 21%)
• Argon 0.93% (9300 parts per million)
• Carbon Dioxide 0.035% (350 ppm)
• Neon 18 ppm
• Helium 5.2 ppm
• Methane 1.4 ppm
• Ozone 0.07 ppm
Other Components of the Atmosphere
• Water Droplets
• Ice Crystals
• Sulfuric Acid Aerosols
• Volcanic Ash
• Windblown Dust
• Sea Salt
• Human Pollutants
Structure of the AtmosphereThe atmosphere is thicker at the equator, thinner
at the poles• 4 Levels Defined by Temperature a. Troposphere (cools farther from surface)
– Where Weather (moisture) Happens
b. Stratosphere– Ozone Layer (O3), blocks ultraviolet radiation
c. Mesosphere- gets way coldd. Thermosphere- hot due to large amount of solar
radiation, but you freeze b/c low # of molecules!– Includes the Ionosphere (Northern Lights)
Troposphere (0 – 15km)• Temperature of 20C at surface to -60C at
15km
• Convection Currents: Heating rock and water at the Surface creates warm air at surface, Warm air rises, but air expands as it rises and cools as it expands, then it sinks again
• Two opposing action = constant turnover, keeps our atmosphere mixed.
Stratosphere
• Altitude 15-50 km
• Temperature increases with altitude
• -60 C at base to 0 C at top
• Reason: absorption of solar (ultraviolet) energy to make ozone at upper levels (ozone layer)
• Ozone (O3) is effective at absorbing solar ultraviolet radiation
Mesosphere
• 50 – 80 km altitude
• Temperature decreases with altitude
• 0 C at base, -95 C at top
• Top is coldest region of atmosphere
Thermosphere
• 80 km and above
• Temperature increases with altitude as atoms accelerated by solar radiation
• -95 C at 80km to +100 C at 120 km
• Cannot feel the heat.
• Traces of atmosphere to 1000 km
• Formerly called Ionosphere
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, nothing warms it up.
Composition and Altitude
• Up to about 80 km, atmospheric composition is uniform (troposphere, stratosphere, mesosphere)
• Above 80 km light atoms like hydrogen and helium rise above the other heavier molecules of nitrogen and oxygen..
What happens above 120 km
• Below 80 km, an atom accelerated by solar radiation will very soon hit another atom
• Energy gets evenly distributed in the atmosphere
• Above 80 km atoms rarely hit other atoms• Light atoms get accelerated and have
more movement and fly higher, but few atoms escape entirely
Atmospheric Layers
Energy Balance
From Cunningham & Cunningham, 2004, Fig. 9.2
Reflected = 25 + 5 = 30
Absorbed = 25 + 45 = 70