Transcript Atmosphere Test Review

Atmosphere Test Review
Atmosphere Composition
• Composition of
Earth’s Atmosphere:
– 78% Nitrogen
– 21% Oxygen
– 1% Other
Air Pressure and Altitude
• Gas molecules in the atmosphere are
pulled to the Earth’s surface by gravity,
making the troposphere the most dense
layer of the atmosphere.
• For each layer of the atmosphere:
– As altitude increases, density decreases
– As altitude increases, air pressure decreases
Layers of the Atmosphere
• Troposphere
– Lowest layer of the
atmosphere
– Most dense layer of
atmosphere
– Where weather
happens
– Temperature
decreases as altitude
increases
Layers of the Atmosphere
• Stratosphere:
– Layer above the
troposphere
– Temperature increases as
altitude increases. This
occurs because the ozone
layer, found at the top of
the stratosphere, absorbs
ultraviolet radiation from
the sun, which warms the
air.
Layers of the Atmosphere
• Mesosphere:
– The layer between the
stratosphere and the
thermosphere.
– Temperature
decreases as altitude
increases.
– The Mesosphere is the
coldest layer of the
atmosphere.
Layers of the Atmosphere
• Thermosphere:
– The uppermost layer
of the atmosphere.
– Temperature increases
as altitude increases.
Atoms of nitrogen and
oxygen absorb highenergy solar radiation
and release thermal
energy.
Radiation
• Radiation is the
transfer of thermal
energy (heat) by
electromagnetic
waves.
– The sun heats the
Earth by radiation
(visible and ultraviolet
light)
Conduction
• Conduction occurs
when thermal energy
(heat) is transferred
through a material.
– Conduction occurs
when the surface of
the Earth transfers
heat to the
atmosphere directly
above it.
Convection
• Convection is the
transfer of energy by
the circulation of
gases or liquids.
– Convection occurs in
the atmosphere when
warm, less dense air
rises and cool, more
dense air sinks.
Sun’s Heat
• 25% of the Sun’s radiation that reaches Earth is
reflected back into space by the atmosphere
• 5% of the Sun’s radiation that reaches Earth is
reflected by the Earth’s surface
• 20% of the Sun’s radiation that reaches Earth is
absorbed by the Earth’s atmosphere
• 50% of the Sun’s radiation that reaches Earth is
absorbed by the Earth’s surface
Greenhouse Effect
• The greenhouse effect occurs when gases
in the Earth’s atmosphere absorb heat
energy and radiate it back to Earth.
– Examples of greenhouse gases are: carbon
dioxide and water vapor
– Humans emit carbon dioxide into the air by
burning fossil fuels. This occurs in factories,
transportation, the production of electricity,
and when heating homes and businesses.
Global Warming
• When the Earth’s
atmosphere is polluted
with too many
greenhouse gases such
as carbon dioxide, the
atmosphere begins to
absorb more heat than is
natural and radiate it to
Earth. This can lead to a
rise in average global
temperatures.
Air Pressure
• Temperature has an effect on air pressure
– When air molecules are heated they speed up and
spread out, making the air less dense. There are
fewer air molecules pushing on a surface, creating a
lower pressure.
– When air molecules are cooled, they slow down and
move closer together, making the air more dense.
There are more air molecules pushing on a surface,
creating a larger pressure.
• Warm air=less dense=lower pressure
• Cool air=more dense=higher pressure
Wind
• Wind occurs when
there is a difference in
air pressure.
• Air molecules will
move from a high
pressure area to a
low pressure area.
Convection Cells
• Warm air rises at the equator and travels toward
the poles. At about 30o N and S latitude, the air
has cooled and become dense enough to sink to
Earth’s surface. The air then travels back
toward the equator, warming as it moves. This
creates a circular pattern of air called a
convection cell.
• Convection cells form about every 30o in
latitude.
Pressure Belts
• Pressure belts are bands of high and low
pressure that occur at every 30o of
latutide, where convection cells meet.
Coriolis Effect
• Global winds travel on a curved path
because of the rotation of the Earth. This
is called the Coriolis Effect.
– Winds traveling northward curve to the east
– Winds traveling southward curve to the west
Winds
Global Winds
• Trade winds: Winds that occur on either
side of the equator to 30o N and S latitude.
• Westerlies: Winds that occur from 30o to
60o N and S latitude. Westerlies travel
from west to east.
• Polar Easterlies. Winds that occur from
60o N and S latitude to the poles. Winds
travel from east to west.
Local Winds
• Local winds only occur near specific
geographic features.
– Example: Sea and Land Breezes: During
daytime, the surface of the Earth heats more
quickly than water. Warm (less dense) air
over the surface of the Earth rises, and cooler
(more dense) air comes from the lake/ocean
to the land to replace it. During nighttime, the
surface of the Earth cools faster than the
water. Warm air over the water rises, and
cooler air from the land comes in to replace it.