1. Wind and the Ocean

2. Wind
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.

3. Air Pressure Force of the air mass on earth
High pressure: dry, dense air
Low pressure: moist, less dense air.

4. 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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6. Global Winds 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.

7. Global Winds cont.
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.

8. Earth’s Rotation and the Effect on Wind
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
Polar easterlies
Prevailing westerlies
Trade winds

9. Earth’s Rotation and the Effect on Wind
Polar easterlies:
Blow from northeast
Poles to 60° N.
Prevailing westerlies:
Blow from the southwest
30°N to 60°N
dominant winds in US
Trade winds (NE and SE):
Blow from the northeast
30°N to equator.

11. Global Wind Patterns

12. Winds cont.
Doldrums: light shifty winds at the equator (named for lack of wind)
Horse latitudes: light variable winds at 30°N

13. Winds and Surface Currents
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.

15. Gyres Circular current Formed by: Due to the Coriolis Effect:
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.
Important because they move the drifting plankton thousands of km across the ocean.
Distributes heat on Earth

16. Main Ocean Gyres (5)

17. Upwellings
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

18. Upwelling
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