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Atmosphere
the thin layer of gases that surrounds Earth
- -Absorbs radiation and moderates climate
- -Transports and recycles water and nutrients
- -78% nitrogen gas, 21% oxygen gas, 1% other gases
- -Its four layers differ in temperature, density and composition
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Troposphere
- bottommost layer
- Air for breathing, weather
- Temperature declines with altitude
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Tropopause
limits mixing between troposphere and the layer above it
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Stratosphere
- 11-50 km (7-31 mi) above sea level
- Drier and less dense, with little vertical mixing
- Colder in its lower regions
- Contains UV radiation-blocking ozone, 17-30 km (10-19 mi) above sea level
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Mesosphere
-Extremely low air pressure
-Temperatures decrease with altitude
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Thermosphere
- •atmosphere’s top layer
- -Extends upward to 500 m (300 mi)
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Atmospheric Pressure
•measures the force per unit area produced by a column of air
-Decreases with altitude
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Relative Humidity
the ratio of water vapor a given volume of air contains to the amount it could contain at a given temperature
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Convective Circulation
- less dense, warmer air rises and creates vertical currents
- -Rising air expands and cools
- -Cool air descends and becomes denser, replacing warm air
- -Influences both weather and climate
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Front
the boundary between air masses that differ in temperature, moisture, and density
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Cold/Warm Front
the boundary where colder, drier air displaces warmer, moister air
the boundary where warm moist air replaces colder, drier air
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High Pressure System
air that moves away from a center of high pressure as it descends
Brings fair weather
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Low Pressure System
air moves toward the low atmospheric pressure at the center of the system and spirals upward
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Thermal Inversion
a layer of cool air occurs beneath a layer of warmer air
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Inversion Layer
band of air in which temperature rises with altitude
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Hadley Cells
- near the equator, surface air warms, rises, and expands
- Releases moisture and heavy rainfall near the equator
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Ferrel Cells and Polar Cells
- •lift air
- -Creates precipitation at 60 degrees latitude north and south
- -Causes air to descend at 30 degrees latitude
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Corialis Effect
the north-south air currents of the convective cells appear to be deflected from a straight path
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Doldrums
- near the equator
- -Few winds
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Trade Winds
between the equator and 30 degrees latitude
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Westerlies
from 30 to 60 degrees latitude
Originate from the west and blow east
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Air Pollutants
gases and particulate material added to the atmosphere
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Air Pollution
the release of pollutants
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Aerosolis
reflect sunlight back into space and cool the atmosphere and surface
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Point Sources
specific spots where large quantities of pollutants are discharged (power plants and factories)
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Nonpoint Sources
more diffuse, consisting of many small sources (automobiles)
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Primary Pollutants
directly harmful and can react to form harmful substances (soot and carbon dioxide)
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Secondary Pollutants
- form when primary pollutants interact or react with constituents or components of the atmosphere
- (tropospheric ozone and sulfuric acid)
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Criteria Pollutants
pollutants judged to pose especially great threats to human health
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Carbon Monoxide
- -A colorless, odorless gas
- -Produced primarily by incomplete combustion of fuel
- -Poses risk to humans and animals, even in small concentrations
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