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Winds
Chapter 16 Section 3
Pages 536-544
What is Wind?
• Wind- The horizontal movement of air
from an area of high pressure to an
area of lower pressure.
What causes winds?:
• Winds are caused by differences in air
pressure.
• The pressure differences are caused by
unequal heating of the Earth’s
atmosphere.
What causes winds?:
• More Dense air
sinks
• Less Dense air
rises-
– (Air Has High
Pressure)
– (Air Has Low
Pressure)
How is wind measured?
• Weather Vane- an instrument used to
determine the direction of the wind.
• Anemometer- An instrument used to
measure wind speed.
Anemometer
• Cups blow in the wind and measure the
speed of the wind.
Weather Vane
• Tells the direction the wind is blowing
from.
• If it is pointing to the south- wind is
blowing from the south to the north.
Wind Chill
• Wind Chill Factor- Wind blows over
your body and removes body heat
away from your body.
– The stronger the wind, the more heat
removed, the colder you feel.
Wind Chill
• What happens to
the temperature
as wind speed
increases?
• What is the wind
chill if the temp is
5˚C and the wind
is blowing at
25mph?
Local Winds
• Are winds that blow over short
distances.
• Caused by unequal heating of Earth’s
surface with in a small area.
– Land heats faster than water.
– Water cools slower than land.
Local Winds
• Sea Breeze- The flow of air
from a body of water to land.
– Land is warmer – less dense air rises.
– Water is cooler- more dense air sinks.
Local Winds
• Land Breeze- The flow of air from
land to a body of water.
– Water is warmer – less dense air rises.
– Land is cooler- more dense air sinks.
Monsoons
• A large sea and land breeze over a
large region that changes direction with
the seasons.
– Winds blow steadily from the land to the
ocean, or the ocean to the land depending
on the season.
Monsoons (Summer)
• The land is warmer
than the water.
• Less dense air rises
• The water is cooler
than the land.
• More dense air sinks
• Wind blows from the
water to the land.
• Carries water vapor,
making the air humid
which causes heavy
rain.
Monsoons (Winter)
• The water is warmer
than the land.
• Less dense air rises
• The land is cooler
than the water.
• More dense air sinks
• Wind blows from the
land to the water.
• Causes a dry
season in India.
Reading Wind Maps
Cloud
Cover
• The line points into the weather station from
the direction the wind came from.
• This example shows that the wind is
coming from the east.
Reading Wind Maps
Cloud
Cover
• To determine wind speed. Read the flag on
the end of the wind direction line.
• Use the chart to determine the wind
speeds in knots and mph.
• Example above: 8-12 knots (9-14mph)