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Atmosphere
&
Weather
Earth Science
2010-2011
Energy Transfer in the Atmosphere
Earth’s energy is provided by the
_______.
Energy is important to us because it…
1. Drives winds and ocean
currents.
2. Allows plants to grow to
produce food.
3. Provides nutrition for many
animals.
When Earth receives energy from the Sun…
What three things happen to that energy???
1. Reflected back into space.
2. Absorbed by the atmosphere.
3. Absorbed by the land and
water.
Does land or water absorb the Sun’s
energy faster???
Land…. Why?
•Because it takes more energy to
warm up a body of water than it
does to warm up an equal area of
land.
In what three ways is heat transferred
through the atmosphere???
What is radiation???
Radiation is energy that is transferred in the
form of rays or waves. Earth radiates some
of the energy it absorbs from the sun back
toward space.
How can you feel the Sun’s warmth on your
face even though you are not in direct
contact with the Sun?
What is conduction???
Conduction is the transfer of energy when molecules
bump into one another. Molecules are always in
motion. When warmer, faster moving objects touch
cooler , slow moving objects energy is transferred.
As air moves over warm land or water,
molecules in the air are heated by direct
contact with each other. A process
called???
What is convection???
Convection is the transfer of heat by the flow of
material. As air is warmed, the molecules move apart =
less dense air. Air pressures decreases because the air
is less dense. In cold air molecules move closer together
so the air is more dense and air pressure increases.
How do convection currents circulate heat
throughout the atmosphere???
Convection currents circulate heat
throughout the atmosphere by…
As air
temperature
increases, the air
molecules move
apart, and
become less
dense.
Air pressure
decreases in
warmer
temperatures,
because fewer
molecules are in
the same space.
Air Molecules
Cooler, more dense air sinks while warmer, less dense air
rises, forming a convection current!
Thinking question…
after discussing what happens on Earth
to the Sun’s radiation, and how heat can
be transferred…
What do you think helps control how
much of the Sun’s radiation is absorbed
here on Earth ???
Why can life exist here on Earth,
and not on other planets???
What is a hydrosphere???
A hydrosphere is the term that refers to all the water on Earth.
Air Movement
• Play BrainPOP
–“Wind”
Forming Wind
…Remember that the uneven heating of the
Earth’s surface by the Sun causes some areas
to be warmer than others…
…Remember that warmer air expands, becoming less
dense than cold air… causing air pressure to be
lowered where the air is heated.
So… what is wind???
Wind is
…the movement of air from an area of
_higher_ pressure to an area of
__lower___ pressure!
Yes or No…
Do different areas of Earth receive
different amounts of radiation from
the Sun because the Earth is curved?
Which portion of the Earth receives
the most radiation from the Sun?
Answer: The Equator receives more radiation than
areas to the North and South.
The heated air at the equator is less dense, so it is
displaced by denser, colder air, creating convection
currents.
The cold, denser air coming from the poles,
receives less radiation from the Sun, making
the air at the poles much cooler. This results
in the dense, high-pressure air sinking and
moving along Earth’s surface.
Note: Dense air sinking as less-dense air rises does not explain everything about
wind… it is only one factor in forming wind!
The Coriolis Effect…
What is it???
When the rotation of
the Earth causes
moving air and water to
appear to turn to the
right North of the
equator and to the left
South of the equator.
From what we have just discussed….
Can you describe to me what happens to the air
pressure and resulting weather near the
equator???
Global Winds
Surface Winds
What are the names of the three different surface winds
that descend onto the Earth’s surface?
1. Trade Winds
2. Prevailing Westerlies
3. Polar Easterlies
Trade Winds:
 Also called Tropical Winds
 Used by sailors to establish early trade routes
 Found at 30º North and South Latitude
Prevailing Westerlies:
 Blow in opposite direction from the trade winds
 Responsible for much of the movement of weather across North
America
 Found between 30° and 60 ° Latitudes
Polar Easterlies:
 Found near the poles
 Near N. Pole, they blow from Northeast to Southwest
 Near S. Pole, they blow from Southeast to Northwest
Winds in the Upper Troposphere
Narrow belts of strong winds, called _______
_____________, blow near the top of the
troposphere.
Polar jet streams form at the boundary of
cold, dry polar air to the north and warmer,
more moist tropical air to the south.
The Jet Stream…
 Moves faster in the winter because the difference between the cold
air and warm air is greater!
 Helps move storms across the country.
 Pilots when flying eastward take advantage and save time and fuel.
Local Wind Systems
Global wind systems determine the major
weather patterns for the entire planet. Smaller
wind systems affect local weather.
If you live near a large body of water… like an
ocean… you are familiar with two such wind
systems – sea breezes and land breezes!
Local Wind: Sea Breeze
 The movement of air toward the
land from the water (sea).
 Created during the day because
solar radiation warms the land more
than the water.
 Air over the land is heated by
conduction.
 This heated air is less dense and has
lower pressure.
 Cooler, denser air over the water has
higher pressure and flows toward
the warmer, less dense air.
 Resulting in a convection current
that blows wind from the sea
toward land.
Local Wind: Land Breeze
 The movement of air toward the
water from the land.
 Created at night because the land
cools much more rapidly than the
ocean water.
 Cooler, denser air above the land
moves over the water, as the warm
air over the water rises.

Resulting in a convection current
that blows wind from the sea
toward land.
Questions?????