Download Wind - Northside Middle School

Wind
What is Wind?
• Wind is the movement of air from a region of high
pressure to a region of lower pressure. These
areas of high and low pressure are created from
temperature differences caused by the sun
heating the earth, which in turn heats the
atmosphere.
• Air moves from high to low pressure area
-soThe lower the pressure area the stronger the wind.
Local winds are. . .
• Winds that blow over short distances
• Caused by unequal heating of the earth’s
surface within a small area
• Form only when no winds are blowing from far
away
Sea (large open water) Breeze
onto Land:
• Land heats more quickly during day than the adjacent
water. A sea-breeze is formed by increasing temperature
differences between the land and water which create a pressure
low over the land due to its relative warmth and forces higher
pressure, cooler air from the sea to blow onto the land..
Land Breeze from sea or a
Lake
• At night, the land cools off quicker than the open
water. If the land cools below that of the adjacent
open water, the pressure over the water will be lower
than that of the land. This creates a land breeze
flowing back out towards the open water.
Valley Breeze: (occurs mainly
in afternoons)
• During the day, sunlight
warms valley walls,
which warm the air in
contact with them. The
heated air rises and
forms the valley breeze
• As the warm air rises
and cools over the
mountains, clouds may
form from the warm
moist air condensing..
Mountain Breeze: (occurs
evenings and night)
• This wind is formed at night by the cooling along
mountainsides. As the slopes become colder than the
surrounding atmosphere, the air closest to the
mountainside cools and drains down into the valley.
The cool air sinks and forms mountain breeze.
Global Winds
• Global winds blow steadily from a specific
direction over long distances
• The movement air makes between the
equator and the poles produces global
winds.
Air Movement (AKA wind) on planet
Earth:
Here are the global winds in
motion…
• Notice that air rises and sinks as it
heats and cools in three separate
systems.
– The prevailing westerlies rise in a
different direction than the trade
winds and polar easterlies!
• The earth also spins, creating the
direction the winds move on the surface
of the earth. In simple terms, as air
begins flowing from high to low pressure,
the Earth rotates under it, making the
wind follow a curved path. That is why on
a 1 dimensional map, the arrows of the
global winds are curved.
• Global wind patterns
What are the trade
winds?
The trade winds are
air movements
toward the equator
moving from east to
west. They are warm,
steady breezes that
blow almost
continuously. For
hundreds of years
sailors (and
pirates…arg!) used
them to sail their
ships from Europe to
South America and
the West Indies.
What are the prevailing
westerlies?
Between thirty and sixty
degrees latitude, the
winds that move toward
the poles appear to curve
to the east. Because
winds are named from the
direction in which they
originate, these winds are
called prevailing
westerlies. Prevailing
westerlies in the Northern
Hemisphere are
responsible for many of
the weather movements
across the United States
and Canada. That is why
we look at the weather
happening in California to
help predict our weather
What are the polar
easterlies?
Cold air near the
poles sinks and flows
back toward lower
latitudes. The polar
easterlies meet the
prevailing westerlies
at about 60° north at
south latitudes, along
a region called the
polar front. The
mixing of warm and
cold air along the
polar front has a
major effect on
weather changes in
the United States.
Again, because these
winds begin in the
east, they are called
easterlies.
What are the
doldrums?
The doldrums is an
area of calm weather.
The trade winds
coming from the
south and the north
meet near the
equator. These
converging trade
winds produce
general upward
winds as they are
heated, so there are
no steady surface
winds.
What are the horse
latitudes?
The horse latitudes is
another belt of calm air.
Warm air that rises at the
equator and moves
toward the poles stops
moving and sinks in this
area. Hundreds of years
ago, sailors stuck in this
area where wind doesn’t
blow ran out of food and
water for their horses and
had to throw the horses
overboard. That is how
the area got the name
“horse latitude”.
The Jet Stream
• Jet streams are relatively
narrow bands of strong wind
in the upper levels of the
atmosphere. The winds
blows from west to east in jet
streams but the flow often
shifts to the north and south.
Jet streams follow the
boundaries between hot and
cold air. Since these hot and
cold air boundaries are most
pronounced in winter, jet
streams are the strongest for
both the northern and
southern hemisphere winters
Measuring Wind
• Wind is measured
with a tool called the
Anemometer.
• Beaufort Wind Scalethis scale is used as
an indication of how
strong winds are.
Take a look at how
winds are rated.
Now let’s measure our own wind…
• Take your homemade ghetto fab
anemometer outside and measure the
wind in a few places.
• I want you to investigate how buildings
and the surrounding landscape affect how
much wind you get.