Wind Notes
• Wind is the horizontal
movement of air that moves
from areas of high pressure to
areas of low pressure.
• Wind is described by its direction and its
speed.
• Winds are named by the direction they blow
from. (for example, a prevailing westerly
blows from the west)
• Wind speed is measured by an
anemometer.
What causes the wind to blow?
As the sun warms the Earth's surface,
the atmosphere warms too.
Some parts of the Earth receive direct rays from the sun
all year and are always warm.
Other places receive indirect rays, so the climate is colder.
Warm air, which weighs less than cold air, rises.
Then cool air moves in and replaces the rising warm air.
This movement of air is what makes the wind blow.
All winds are caused by differences in air pressure.
Winds are created when….
warm air rises creating low pressure.
• Cool, more dense air comes in to
replace the warm air creating high
pressure.
• As air goes from areas of high to low
pressure, winds form.
Winds are caused by convection
currents, just like deep ocean currents
and convection in the mantle.
2 types of winds:
1. local winds
2. global winds
1. local winds
•cover short distances
• blow from any direction
• 2 types of local winds:
– sea breezes- blow from sea to land
– land breezes – blow from land to sea
*Both are created because the land heats
up and cools off faster than the sea.
animation of sea and land breezes
• http://www.classzone.com/books/earth_sci
ence/terc/content/visualizations/es1903/es1
903page01.cfm?chapter_no=visualization
sea breeze
land breeze
global winds
•caused by differences in density
•blow over long distances
• curve because of the Coriolis Effect.
(Coriolis Effect – rotation of the
Earth causing moving air and water
to curve)
•Northern Hemisphere -winds
curve to the right
•Southern Hemisphere- winds
curve to the left.
types of global winds:
-calm winds:
doldrums
horse latitudes
– strong winds:
trade winds
prevailing westerlies
polar easterlies
*Remember: winds are named by the
direction they come from.
global winds animations
• http://www3.interscience.wiley.com:8100/l
egacy/college/strahler/0471238007/animat
ions/ch07_animations/animation3.html
• http://www.mhhe.com/biosci/genbio/tlw3/e
Bridge/Chp29/animations/ch29/global_win
d_circulation.swf
• http://www.phschool.com/webcodes10/ind
ex.cfm?wcprefix=cfp&wcsuffix=4023&fuse
action=home.gotoWebCode&x=0&y=0.
This one has a game you can play at home!
doldrums
•at the equator, surface winds are calm
and weak.
horse latitudes
• found at 30 degrees North and 30 degrees
South latitude (of the equator)
• calm winds called this because sailors had
to throw horses overboard when they got
caught in these winds (or lack of winds)
trade winds
• 30 degrees N & S of equator and blow
towards the equator.
• steady winds that enabled sailors to
carry cargo from Europe to the West
Indies and South America.
prevailing westerlies
•strong winds
•located in the belt from 30-60 degrees
latitude in both hemispheres.
•has an impact on the US weather
polar easterlies
• near the north and south poles
• US weather is influenced by these
• cooling takes place between the 50-60
degree latitude as it approaches the
poles
jet stream
• discovered in 1940’s
• can be found in the upper troposphere
10 km above Earth
• strong high speed and high pressure
• moves west to east across the US,
moving storms
brainpop movie on wind
• http://www.brainpop.com/science/weather/
wind/