Download Global Winds

EQ: How is heat transferred
through the layers of the Earth’s
atmosphere?
WIND
Whooosh!!!!!
 When you open the valve
on a bicycle tube, the air
rushes out.
 Why?
 The air inside the tube is
at a higher pressure than
the air outside the tube.
 This is similar to how
winds are formed!
Unequal Heating
 The movement of air
caused by differences in
air pressure is called wind
 The greater the pressure
difference, the faster the
wind moves.
 Wind is the result of a
convection current
Unequal Heating
 Differences in air pressure
are generally due to the
unequal heating of the
earth.
 Remember, warm air is
less dense and will rise.
 Cool air is more dense
and sinks
Unequal Heating
 The equator receives more
direct solar energy (radiant
heating) than other latitudes,
so air at the equator is warmer
and less dense than the
surrounding air.
 Lighter, one blanket
 Warm, less dense air rises and
creates an area of low
pressure.
 This warm, rising air flows
toward the poles.
Unequal Heating
 However, at the poles, the
air is colder and denser than
the surrounding air, so it
sinks.
 Heavier, many blankets
 This sinking air creates an
area of high pressure
around the poles
 This cold polar air then
flows toward the equator
Air blows from high to low!!
Low Pressure
High Pressure
 Rising, warmer air
 Sinking, colder air
 Moist: Clouds, rain, snow,
strong winds, warmer air
 Dry: Clear skies, sunshine,
cool air, little wind
 Snow means low!
 High and Dry!
Pressure Belts
 You may imagine that wind moves in one huge,
circular pattern from the poles to the equator.
 In fact, air travels in many large circular patterns
called convection cells
 Convection = circulation (moving air)
 These convection cells are separated by pressure
belts, which are bands of high or low pressure.
 These belts are found about every 30* latitude
Pressure Belts
Pressure Belts
 As warm air rises over the
equator and moves
toward the poles, the air
begins to cool.
 At about 30* North and
30*South latitude, some
of this cool air begins to
sink
Pressure Belts
 This cool sinking air,
causes high pressure
around 30* N and S
latitude.
 This cooled air flows back
to the equator, where it
warms again, and rises.
And the same thing is happening at the poles,
just in reverse!
https://www.youtube.com/watch?v=FicN1PCGFp0
 At the poles, the cold air
sinks, and moves toward
the equator.
 The air warms as it moves
toward the equator.
 Around 60* N and S
latitude, the warmer air
rises, which creates a low
pressure belt.
 This air then flows back to
the poles
The Coriolis Effect
 Pressure differences cause
the air to move between the
equator and the poles.
 But due to the earth’s
rotation, the air does not
move in straight lines!
 This apparent curving of the
path of winds is called the
Coriolis Effect.
Coriolis Effect
 Because of the Coriolis
Effect, winds traveling north
in the Northern Hemisphere
appear to curve to the east,
and winds traveling south
curve to the west.
 How would the Southern
Hemisphere compare?
 http://www.phschool.com/a
tschool/phsciexp/active_art/
global_winds/index.html
 https://www.schooltube.com/video/374fb8d368df43f
faae2/Bill%20Nye%20Wind
Global Winds
EQ: How is heat transferred through the layers of the
Earth’s atm0shere?
Global Winds
 The combination of convection cells found at every
30* latitude and the Coriolis Effect produces patterns
of air circulation called Global Winds.
 The major global wind systems are the Polar
Easterlies, Westerlies, and Trade Winds.
 Winds such as the Easterlies and Westerlies are
named for the direction from which they blow
Polar Easterlies
 The wind belts that extend
from the poles toward 60° N
and S latitude.
 They are formed when cold,
sinking air (high pressure)
 Polar Easterlies can carry
cold, arctic air over the US,
producing snow and
freezing weather
Westerlies
 The wind belts found
between 30° and 60°
latitude.
 They flow toward the
poles from west to east.
 Can carry moist air,
producing rain or snow
(low pressure)
 Responsible for our
weather
Trade Winds
 Winds that blow from 30
degrees latitude almost to the
equator are the trade winds.
 Named after their ability to
quickly propel ships across the
ocean
 They are warm, steady breezes
that blow almost
continuously(11-13 mph) (low
pressure).
 The Coriolis Effect makes the
trade winds appear to be
curving to the west in the
Northern Hemisphere
The Doldrums
 The trade winds of the N
and S hemispheres meet in
an area around the equator
called the doldrums.
 There is very little wind and
the area is calm because the
warm rising air creates an
area of low pressure.
 Doldrums means “dull” or
“sluggish”
Coriolis Effect
 The Earth’s rotation causes wind and surface currents
to move in curved paths rather than in straight lines.
 The apparent curving of moving objects from a
straight path due to the Earth’s rotation is called the
Coriolis effect.
The Horse Latitudes
http://www.purposegames.com/game/global-winds-game
 At about 30 degrees N and S
latitude between the trade
winds and prevailing westerlies
 The winds at these locations
are weak.
 Most of the world’s largest
deserts are located here
because the sinking air is very
dry
 Weather is usually calm
 Term from sailing ships that were stuck
due to calm winds for long periods of
time
 due to shortages of food and water
horses would die and be thrown
overboard
Jets Streams
 Jet streams are narrow belts
of high-speed winds that
blow in the upper
troposphere and lower
stratosphere.
 They can blow as fast as 400
km/hr
 They do not follow regular
paths around the earth.
 They help pilots and
meteorologists
Local Winds
 Local winds generally move short distances and can
blow from any direction.
 Local geographic features, such as a shoreline or a
mountain can produce temperature differences that
can cause local winds
Mountain and Valley Breezes
Sea Breezes
http://www.youtube.com/watch?v=gM0d3fGew-0&feature=related