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The Atmosphere has Wind Patterns.

The Atmosphere has Wind Patterns. Wind. Wind is the motion of air . It is caused by the uneven heating of Earth’s surface. Air moves from areas of high density to areas of low density. Density can be measured through atmospheric pressure .

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The Atmosphere has Wind Patterns.

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  1. The Atmosphere has Wind Patterns.

  2. Wind • Wind is the motion of air. • It is caused by the uneven heating of Earth’s surface. • Air moves from areas of high density to areas of low density. • Density can be measured through atmospheric pressure. • Wind direction is measured with a wind vane and wind speed is measured with an anemometer.

  3. There are 3 forces that affect the way wind blowsThe Pressure Gradient Force • The pressure gradient force tries to equalize the pressure differences. This causes high pressures to push air toward low pressures. • If wind was under the effect of the pressure gradient force only, it would flow directly from high pressure regions to low pressure regions.

  4. The Coriolis Effect • The Coriolis Force is caused by Earth’s Rotation. • Global winds curve as Earth turns beneath them. • Winds in the Northern Hemisphere turn away from the equator in a clockwise direction. • Winds in the Southern Hemisphere turn away from the equator in a counter-clockwise direction.

  5. Friction • The rough surface of Earth slows down the wind. • Question: Where would you expect stronger winds, The Tri-Cities or Seattle?

  6. How Does Earth’s Rotation Affect Wind? • Blow up a Balloon. • Have a partner slowly rotate the balloon to the right. Draw a line straight down from the top of the balloon to the center of the balloon as it rotates. • Now draw a straight line up from the bottom of the balloon straight up to the center as the balloon rotates.

  7. What do You Think? • How did the rotation affect the lines? • How does this activity demonstrate the Coriolis Effect? • How might changing the speed of the balloon’s rotation affect your results? • Test your prediction.

  8. Pressure Gradient Force On the diagram use arrows to indicate the direction of air flow due to the pressure gradient force.

  9. PGF + Coriolis Force (Effect) On the diagram use arrows to indicate the direction of air flow due to the Pressure Gradient force and the Coriolis force.

  10. PGF + Coriolis Force + Friction Now combine the three forces to indicate wind direction.

  11. Low Pressure Center • Winds converge (come together) in low pressure regions as air is pushed away from high pressure regions. • The air in the center must go somewhere, so when air converges near a low, it is forced upward. • As the air cools, it cannot hold water vapor. This vapor condenses, which forms clouds and precipitation. • Rain, sleet, hail, and snow often take place near low pressure areas.

  12. High Pressure Center • When air diverges (moves away from) high pressure areas, the air above sinks to fill the empty space. • The sinking air warms. • As the air warms, it can hold more water vapor. • The clouds will evaporate. • Due to this, high pressure areas are usually dry.

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