Transcript Earth`s Atmosphere

Earth’s Atmosphere
Chapter 3, Section 2
•Describe the composition of the Earth’s
atmosphere
•Describe the layers of the Earth’s atmosphere
•Explain 3 mechanisms of heat transfer in
Earth’s atmosphere
•Explain the greenhouse effect
General Description of Atmosphere
• Mixture of gases
– Nitrogen
– Oxygen
– Carbon dioxide & others
• Addition/removal results in change
– Living organisms (plants & animals)
– Volcanic eruptions
– Vehicles/industries
• Insulates Earth’s surface
Composition of Earth’s Atmosphere
• Gases
– 78% Nitrogen
– 21% Oxygen
– 1% other (Ar, CO2, CH4, H2O)
• Atmospheric Dust
– Solid particles
• Soil, salt, ash fro fire & volcanic eruptions
• Particulate matter (combustion, skin, hair,
clothing bits, pollen bacteria & viruses
• Aerosols (tiny liquid droplets)
• Creates air pressure
– Due to gravitational pull
– Greatest near Earth’s surface
Earth’s Atmospheric Layers
(Ionosphere)
Earth’s Atmospheric Layers
• Divided into 4
layers based
on
– Temperature
changes
– Pressure
changes
Location of Atmospheric Layers above
Earth’s Surface
Troposphere
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•
•
•
Nearest Earth’s surface (up to 18 km)
Makes up 75% of Earth’s atmospheric mass
Densest layer
Temperature & pressure decrease with altitude
– Except tropopause – very top of layer
– Stable temperature – called “cold trap”
• Wider at equator than poles
• Location of weather occurrence
– Uneven heating due to convection current & winds
– Causes cloud formation (rising water vapor cooled)
• Related to Greenhouse effect
Stratosphere
• 2nd layer above Earth’s
surface (32 km thick, 1850 km above surface)
• Temperature increases
with altitude
• Contains ozone layer
– Reduces UV radiation
– Thinning in Europe, Asia,
North America &
Antarctica
Mesosphere
• 50-80 km above surface
• Coldest layer
– Temperature decreases with
increase in altitude
– -30°C (-130°F)
• Slows, prevents meteors
entering atmosphere
Thermosphere
• 80 – 1000 km above
surface
• Very hot temperatures
(200-2000°C or 3603600°F)
• Ionization of gases
– N2 & O2 absorb X-rays &
gamma rays
– Radiate light (auroras)
• Reflect radio waves
• Area where shuttles orbit
Energy Transfer in the Atmosphere
• Radiation
– Electromagnetic waves – absorbed & converted to
heat
– Visible light, X-rays, UV, Gamma (from sun)
• Conduction
– Transfer by contact between different matter
• Convection
– Caused by temperature differences & changes in
densities of materials
– Occurs only in fluids
– Creates currents
Energy Transfer Diagram
Atmospheric Energy
• Reaches Earth as electromagnetic radiation
– ½ entering atmosphere reaches surface
– ½ absorbed or reflected by gases, clouds, dust
• Oceans & land radiate energy back into atmosphere
– Prevents overheating of Earth’s surface
• Dark colors absorb more energy than lighter ones
– More energy released by darker colors
– Explains higher temperatures in cities than surrounding
country sides
Energy Movement in Atmosphere
• Result of convection currents
– Air heated by Earth’s surface & rises into
atmosphere
– Cools as it rises & becomes more dense & sinks
– Continual process results in circular movement of
air (currents)
– Occurs in troposphere, resulting in weather
occurrences (rain, wind, tornadoes, etc.)
Greenhouse Effect
• Warming of Earth’s surface & lower atmosphere
• Due to carbon dioxide, water vapor & other gases
(methane, nitrous oxide) absorbing & radiating
infrared waves
– Called “greenhouse gases”
– Maintain temperatures that support life
• Excess amounts of carbon dioxide & methane result
in increased heat retention
– Caused by natural & industrial events
– Cause abnormal increases in temperatures (heat)
– Result in shifts in climatic zones, melting of polar ice
caps, increased ocean levels around the world
How is Earth’s atmosphere like glass in
a car?
• Both allow
solar energy
to pass
through
• Both can
absorb and
stop heat
from
escaping