Download Global Winds

Global Winds
What is Weather?
• It is the condition of earth’s atmosphere at a
particular time and place.
Why Air Moves
• The Movement of air caused by differences in Air
Pressure this is called wind.
• Wind: air that moves horizontally, or parallel to the
ground, caused by differences in air pressure
• The greater the pressure difference, the faster the
wind moves.
What is Wind?
http://www.youtube.com/watch?v=xCLw
bqmacck
Causes of Pressure Difference
• Generally caused by the unequal heating of
the earth.
– The equator receives more direct solar energy than
other latitudes, so at the equator it is warmer.
– Therefore the air is less dense-Rises
– This creates low pressure
– REMEMBER: Temperature and Pressure are
opposite of each other. So as Temperature
increases, pressure will decrease.
Cold Air
• Cold air is more dense and sinks- This creates
high pressure
• The highest pressure is found along the Poles.
– What do you think is happening around the
equator is the air sinking or rising?
– Convection Currents Demo:
http://www.youtube.com/watch?v=Ci5P5yy0xlg
Circular Patterns
• Circulation Cells- a giant loop of moving air
that includes a wind belt and the calm regions
that border it
• Convection Cells are separated by Pressure
Belts.
• Pressure Belts are found every 30 degrees of
latitude.
– Ex. At about 30̊north and 30̊ south air cools and
starts to sink (Horse latitudes and Doldrum)
Coriolis Effect
• Coriolis Effect- the influence of Earth's
rotation of objects that move over Earth's
surface, such as wind
• Northern Hemisphere winds traveling north
curve to the east and winds traveling south
curve to the west.
http://www.youtube.com/watc
h?v=i2mec3vgeaI
Global Winds
• Polar Easterlies-the wind belts that extend
from the poles to 60̊ and 90̊ latitude in both
hemispheres
• Westerlies-prevailing winds that blow from
west to east between 30̊ and 60̊ latitude in
both hemispheres.
• Trade Winds-Prevailing winds that blow
northeast from 30 ̊south and 30̊ north latitude
to the equator.
The Doldrums
• Doldrums- The trade winds of the Northern
and Southern Hemispheres meet in an area
around the equator
– Very little wind because the warm rising air
creates low pressure
– Means sluggish or dull
Horse Latitudes
• At about 30 ̊North and 30 ̊South Latitude, sinking air
creates an area of high pressure. These areas are
called horse latitudes.
– Given when ships were struck in this windless area, horses
where sometimes thrown overboard to save drinking
water for the sailors.
– Sinking air is very dry and clear
– Deserts are located in the horse latitudes
Global Winds Circulation
Animation
https://www.youtube.com/watch?v=qh0
11eAYjAA&list=PLgTRudKVovrwgfk5QGukODGY5bgvab9z&index=1
Jet Streams
• Jet Streams are a narrow belt of strong winds
blowing through the upper troposphere
• They can reach a speed of 400 km/hr.
• They affect the movement of storms
• Do not follow regular path
• Jet Stream Animation:
https://www.youtube.com/watch?v=FNnIrIuNbeA
Monsoons – winds that change
direction with the seasons.
Meteorologist – a person
who studies and predicts
the weather.
• They blow from the east, moving from the
horse latitudes toward the equator.
• Very Strong Winds