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Study Guide for Atmosphere Test
Atmosphere- a thin layer of air that surrounds planet Earth.
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Maintains a balanced temperature on Earth.
Contains a mixture of gases needed by organisms to survive.
78% nitrogen, 21% oxygen, 1% hydrogen, helium, methane, ozone and other gases.
Atmospheric Pressure- the downward force (weight) of the air in the atmosphere.
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14.7 psi at sea level
Air has mass and takes up space.
Pressure is greatest at the surface and decreases with altitude.
There are fewer molecules of air above you on a mountaintop than at sea level.
Layers of the Atmosphere
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The ozone layer blocks some ultraviolet radiation. UV rays can cause skin damage and cancer.
80% of the mass is in the troposphere
Energy in the Atmosphere
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The Sun is the source of energy in the atmosphere
Energy is transferred by radiation, convection, and conduction
Convection is the transfer of heat by the flow of heated material such as air or water.
Conduction is the transfer of heat energy that occurs when materials touch each other.
Radiation is the transfer of energy in the form of rays or waves.
The equator receives more direct sunlight energy than the mid-latitudes or the poles because
Earth is curved. Seasons occur because of differences in sunlight energy received.
Water Cycle: evaporation (heat energy added), condensation (heat energy lost), precipitation
(water condenses enough to fall), runoff (gravity causes water to collect in low areas).
Global Winds
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Convection Currents: less dense warm air rises as cool dense air sinks. This produces much of
our weather.
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Coriolis Effect: occurs when the rotation of Earth causes moving air to deflect right or left. This
causes weather systems and storms to circulate. This produces global wind patterns.
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Doldrums- along the equator, heating causes air to expand and rise creating a zone of low
pressure and little wind. Rainy weather develops here almost every day.
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Trade Winds- As equatorial air cools and sinks it flows back toward the low pressure at the
equator. Coriolis effects deflect these winds to the west, creating a consistent pattern that
sailors have relied on for centuries.
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Westerlies: Near 30 degrees north and south latitude air is deflected so that weather systems
move from west to east. This is the pattern we experience in the USA.
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Sea Breeze: in coastal areas winds blow from sea to land during the daytime.
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Land Breeze: in coastal areas winds tend to blow from land to sea during the night.
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Sea and land breezes occur because water heats and cools more slowly than land. These
differences in temperature create convection currents.
Jet Streams- narrow belts of strong winds near the top of the troposphere that help move
weather systems (and airplanes flying west to east).