Transcript Wind and the Ocean - Bowie Aquatic Science

WIND AND THE OCEAN
Wind
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Currents of air
Develop when two adjacent bodies of air have
different densities.
Denser air sinks, pushing less dense air upward.
Convection current is produced.
Density of air is affected by temperature and water
vapor.
Water vapor in an air mass decreases its density
because water vapor is about half as dense as air.
Air Pressure
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Force of the air mass on earth
High pressure: dry, dense air
Low pressure: moist, less dense air.
Ocean Wind
Sea breeze: cooler, denser air above the ocean or
lake sweeps over the shore as air warmed by the
land rises.
-beach areas are usually cooler in the summer than
inland
 Land breeze: at night, breezes blow off land as the
warmer air over the ocean rises.
 Ocean winds tend to keep nearby coastal lands
relatively warm in the winter and cool in the summer.
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http://www.free-online-private-pilot-ground-school.com/images/sea-landbreeze.gif
Global Winds
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Heat is not distributed evenly on the earth.
The equator receives about 60 times more
sunlight than the poles.
Hot (and usually humid) equatorial air masses
are less dense
Cold (and usually dry) polar air is more dense.
Global Winds cont.
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At the poles cold, dense air sinks then flows toward
the equator.
Polar air warms as it moves toward the equator
At the equator, hot, moist and less dense air rises
and moves toward the poles.
Equatorial air cools as it moves toward the poles.
Convection cells are formed.
Earth’s Rotation and the Effect on Wind
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Rotates from west to east
Spherical so therefore the equator rotates faster than the
poles
Cold air from the north pole can’t keep up with the land
beneath it
Three types of global winds
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Polar easterlies
Prevailing westerlies
Trade winds
Earth’s Rotation and the Effect on Wind
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Polar easterlies:
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Prevailing westerlies:
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Blow from northeast
Poles to 60° N.
Blow from the southwest
30°N to 60°N
dominant winds in US
Trade winds (NE and SE):
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Blow from the northeast
30°N to equator.
Global Wind Patterns
Winds cont.
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Doldrums: light
shifty winds at
the equator
(named for lack
of wind)
Horse latitudes:
light variable
winds at 30°N
Winds and Surface Currents
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Winds can produce currents if they blow from the
same direction for long periods.
When wind pushes constantly on the ocean surface,
water particles at the surface begin to move but not
in the direction of the wind.
The rotation of the earth causes water to form a
current at a 90° angle to the wind (Ekman spiral).
Currents will move right in the northern
hemisphere and left in the southern hemisphere.
Gyres
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Circular current
Formed by:
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prevailing winds
the rotation of the Earth
land masses that block the movements of water currents
Due to the Coriolis Effect:
rotate clockwise in the northern hemisphere
 Rotate counterclockwise in the southern hemisphere.
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Important because they move the drifting plankton
thousands of km across the ocean.
Distributes heat on Earth
Main Ocean Gyres (5)
Upwellings
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Wind blowing along western coasts of continents
towards the equator create an effect call the
Ekman Spiral
The wind pushes water at a right angle from the
wind flow and away from land
The outgoing surface water is replaced by cold,
nutrient rich bottom water (upwelling).
Brings nutrients from deeper parts of ocean
Support large populations of plankton, fish, and
fish-eating animals
Upwelling
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http://disc.gsfc.nasa.gov/oceancolor/images/Bengu
ela_upwelling.gif