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Daily Weather Information
Date
Current
Temperature
Wind
Speed
Wind
Direction
Dew
Point
Relative
Humidity
Barometric
Pressure
Earth’s Atmosphere
1
Lower Layers of the Atmosphere
• You study, eat, sleep,
and play in the
troposphere, which is
the lowest of Earth’s
atmospheric layers.
• Earth’s weather
occurs in the
troposphere.
Energy Transfer in the Atmosphere
2
Energy from the Sun
• The Sun provides most of Earth's energy.
• When Earth receives energy from the
Sun, three different things can happen to
that energy.
Energy Transfer in the Atmosphere
2
Energy from the Sun
• Some energy is
reflected back into
space.
• Some is absorbed
by the
atmosphere.
• Some is absorbed
by land and water
on Earth's surface.
Energy Transfer in the Atmosphere
2
Heat
• Heat is energy that flows from an object with
a higher temperature to an object with a lower
temperature.
• Energy from the Sun reaches Earth's
surface and heats it.
• Heat is eventually redistributed by air and
water currents.
Energy Transfer in the Atmosphere
2
Heat is transferred through the atmosphere in
three ways—radiation, conduction, and
convection.
Energy Transfer in the Atmosphere
2
Radiation
• Radiation is energy that is transferred in
the form of rays or waves.
• Heat from the Sun
reaches Earth in the form
of radiation.
• Heat is transferred from
the Sun to the surface of
Earth, which warms the
surface of Earth.
Energy Transfer in the Atmosphere
2
Conduction
• Conduction is the
transfer of energy that
occurs when
molecules bump into
one another. This
occurs when two
objects are touching.
• Heat from the surface of Earth is transferred to the air
directly above the surface by conduction, causing the
air directly above the surface to become warmer.
Energy Transfer in the Atmosphere
2
Convection
• Convection is
the transfer of
heat by the flow
of material.
• Convection
currents
circulate heat
throughout
Earth’s
atmosphere.
Energy Transfer in the Atmosphere
2
Convection
• When air is warmed, the molecules in it
move apart and the air becomes less dense.
• Air pressure decreases because fewer
molecules are in the same space.
• Warm air has low air pressure.
Energy Transfer in the Atmosphere
2
Convection
• In cold air, the molecules move closer together.
• The air becomes denser and air pressure
increases.
• Cold air has high air pressure.
Energy Transfer in the Atmosphere
2
Heat is
transferred
through the
atmosphere
in 3 ways:
radiation,
conduction,
and
convection.
Air Movement
3
Forming Wind
Because Earth
is curved,
areas of Earth
receive
different
amounts of
radiation from
the Sun.
Air Movement
3
Forming Wind
• The air at the equator is warmer, less
dense, and has lower pressure.
• The air at the poles is colder, denser, and
has higher pressure.
• Wind is the movement of air from an
area of high pressure to an area of low
pressure.
• Differences in air pressure is what
causes wind to blow.
Air Movement
3
Forming Wind
The Sun’s
uneven heating
of Earth’s
surface forms
giant
convection
currents of
wind.
Air Movement
3
The Coriolis Effect
• The rotation of Earth causes moving air and
water to turn to the right north of
the equator and
to the left south
of the equator.
• This is called
the Coriolis
effect.
Air Movement
3
Global Winds
• Global winds are wind patterns caused by the
giant convection currents combined with the
Coriolis Effect.
Air Movement
3
Global Winds
• Early sailors discovered that the wind
patterns on Earth helped them navigate
the oceans.
• Near the equator, sailors sometimes found
little or no wind to move their ships, and it
rained nearly every afternoon.
• The area near the equator where very little
wind occurs and daily rain falls is called the
doldrums.
Air Movement
3
Global Winds - Surface Winds
• Air moving along Earth’s surface
between the equator and 30º latitude
(north and south) creates steady trade
winds that blow to the west.
• These are called trade winds because early
sailors used their dependability to establish
trade routes.
Air Movement
3
Global Winds - Surface Winds
• Between 30º and 60º latitude (north and
south), winds called the prevailing
westerlies blow to the east, in the opposite
direction from trade winds.
• Prevailing westerlies are responsible for
much of the movement of weather across
North America.
Air Movement
3
Global Winds - Surface Winds
• Polar easterlies are found near the poles.
• Near the north pole, easterlies blow from
northeast to southwest.
• Near the south pole, polar easterlies blow
from the southeast to the northwest.
Air Movement
3
Global Winds - Surface Winds
Air Movement
3
Global Winds - Surface Winds
Air Movement
3
Global Winds - Jet Stream
• Narrow belts
of strong
winds, called
jet streams,
blow near the
top of the
troposphere.
• The jet streams move storm systems across
North America from west to east.
Air Movement
3
Local Winds
• 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,
you’re familiar with two such wind
systems—sea breezes and land breezes.
Air Movement
3
Local Winds - Sea and Land Breezes
A sea breeze is a
convection current
that blows wind
from the cooler sea
(high pressure)
toward the warmer
land (low pressure)
during the day.
Air Movement
3
Local Winds - Sea and Land Breezes
At night, the
reverse occurs.
Air moves off
the land toward
the water as the
land cools more
quickly than the
water. This is
called a land
breeze.