Download Wind 6.2

What is wind?
Air moves from areas of high
pressure to areas of low
pressure. This movement of
air is the wind.
Trade Winds
 Winds that blow between
about 30 N latitude and
about 30 S latitude are
know as trade winds. They
became known as trade
winds over hundreds of
years ago when sailing
ships carried trade goods
around the world.
Global Winds
 Trade winds are part of a system of winds called
global winds. A global wind blows steadily over long
distances in a predictable direction.
 Global winds blow because sunlight heats areas near
Earth’s equator more than it heats areas near Earth’s
poles.
 As Earth rotates, places near the poles travel a
shorter distance than places near the equator. This
causes winds away from the equator to curve.
Global Winds
Winds curve to the right in the
Northern
Hemisphere…Clockwise.
Winds curve to the left in the
Southern
Hemisphere…Counterclockwise
.
Coriolis Effect
 The coriolis effect describes the change in
the direction of something on or above
Earth’s surface due to the Earth’s rotation.
 This causes the winds to curve.
 Air warms and cools in 3 different bands as it
moves north from the equator. Since warm air is
less dense than cold air, the direction the winds
blow changes. In the middle band, the direction
of the cooling air is reversed and the winds blow
in the opposite direction.
Local Winds
What usually causes local winds?
Different parts of Earth’s surface are heated by the Sun
at different rates.
Which heats up faster, land or water?
Land
Which type of air, warm or cool, has lower air pressure?
Warm air has lower air pressure.
In what direction does wind blow?
It blows from an area of higher pressure to an area of
lower pressure.
A visit to the Beach!
If you have ever visited the beach, you probably
noticed a breeze.
During the day, you feel the wind blowing from the
ocean onto the land. This movement of air from
water to the land is called a sea breeze.
A visit to the Beach
continued…
As the day turns to night at the beach, you may
notice the wind blowing from the land toward the
ocean. This movement of air from the land to the
water is called a land breeze.
Sea breeze and Land
breeze
Remembering what a sea breeze and a
land breeze are is easy. Just remember
that the breezes are named for where
they come from. A land breeze comes
from land and a sea breeze comes from
the sea.
In both types of breezes, cool air is the
air that is moving.
Valley breeze
In the morning, as cool air moves up out of the
valley towards the top of a mountain it replaces
the warm rising air. This is a valley breeze.
Mountain breeze
As warm air rises in the evening over the valley,
cool air from the mountains flows down into the
valley and this forms a mountain breeze.
Measuring Wind
What instruments are used to measure wind
direction?
Windsocks and weather vanes
What instruments measure wind speed?
Anemometers
Let’s
Review!!!
In which direction do winds in the
Northern and Southern Hemispheres
curve?
Winds that blow to the south
from the North Pole curve to the
right. Winds that blow to the
north from the South Pole curve
to the left.
What would happen to the global
winds if no more heat energy
reached Earth?
The global winds would stop
blowing.
Describe the movement of air
during a sea breeze and a
land breeze.
In a sea breeze, the cooler, higherpressure air over the ocean moves
toward the warmer, lower-pressure air
over the land. In a land breeze, the cooler,
higher-pressure air over the land moves
toward the warmer, lower-pressure air
over the ocean.
How does the Sun’s energy
cause local winds?
The Sun’s energy heats one
area more than another area,
decreasing the air pressure in
the warmed area and causing
cold air to flow toward the area
with the lowered air pressure.
Describe three devices that
are used to measure wind.
A weather vane and a windsock are
two devices that can show which way
the wind is blowing.
An anemometer is a device that
measures wind speed using three or
four cups that rotate when the wind
blows.
Why might you see devices such
as anemometers and windsocks
at airports?
Pilots need to know important
weather variables such as wind
directions and wind speed. For
example, if it is too windy, pilots will
not be allowed to fly.
Wind that blows from the sea
to the land is called a______?
Sea breeze
How does heat energy from
the Sun cause winds?
Heat energy from the Sun causes
changes in air pressure. Highpressure air moves towards lowpressure air. Moving air is wind.
How is a global wind different
from a local wind, such as a
sea breeze?
Sunlight heats areas near the
equator more than it heats areas
near the poles, causing global
winds. Sunlight changes
temperature in a particular area
more than a nearby area, causing
local winds.
How does wind affect
weather?
Wind is the movement of air
particles. Wind can move over
long distances (global winds) or
within small areas (local winds).