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22.3 Atmospheric Circulation

22.3 Atmospheric Circulation. H. L. WIND. The atmosphere is a mixture of gases Wind is the movement of these gases Named for the direction they come from Gases move from areas of higher pressure to areas of lower pressure. Pressure Centers and Winds.

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22.3 Atmospheric Circulation

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  1. 22.3 Atmospheric Circulation

  2. H L WIND • The atmosphere is a mixture of gases • Wind is the movement of these gases • Named for the direction they come from • Gases move from areas of higher pressure to areas of lower pressure

  3. Pressure Centers and Winds • Low pressure centers are also called Cyclones (counter-clockwise*) • High pressure centers are also called Anticyclones (clockwise*) *Rotation direction in Northern Hemisphere

  4. Pressure Differences • LOW Pressure causes air to rise & generally takes water vapor up= • Clouds and storms • HIGH Pressure causes air to sink & generally keeps moisture out of the atmosphere= • Clear skies & nice weather Winds ALWAYS move from HIGH pressure areas to LOW pressure areas!!!!!!!

  5. CONVECTION Air is warmed at the surface Warm air rises Air is cooler higher in the troposphere Cold air sinks

  6. Local Winds • Local winds are caused either by • topographic effects (mountains and land) OR • variations in surface composition (near water)

  7. Land & Sea Breezes • Coastal Areas • During the day, land heats up quicker than the water • The heated air above the land expands and rises=LOW pressure • Colder air over the water is denser= HIGH pressure • Pushes into land= SEA BREEZE

  8. Land & Sea Breezes • Coastal Areas • Land cools faster than water • The air above the water is warmer = LOW pressure • Air above the land is cooler= HIGH pressure. • Making a… LAND BREEZE

  9. Land or Sea Breeze?

  10. http://www.classzone.com/books/earth_science/terc/content/visualizations/es1903/es1903page01.cfm?chapter_no=visualizationhttp://www.classzone.com/books/earth_science/terc/content/visualizations/es1903/es1903page01.cfm?chapter_no=visualization

  11. Mountain & Valley Breezes Valley Breeze • During the day, the valley floor heats up and air above it does too • Warm air rises up the mountain • Air cools as it goes up in elevation & clouds may form

  12. Mountain & Valley Breezes Mountain Breeze • After sunset the pattern reverses • As slopes cool, nearby air cools and sinks down the mountain.

  13. Mountain & Valley Breezes

  14. Global Winds!

  15. Global Winds • Unequal heating and cooling of the atmosphere from continents and oceans creates high and low air pressures • Add in the rotation of the Earth and global wind patterns emerge

  16. Non-Rotating Earth Model • On a hypotheticalnon-rotating planet with a smooth surface of either all land or all water, two large thermally produced cells would form.

  17. Circulation on a Non-Rotating Earth Air would warm and rise at the equator and cool and sink at the poles.

  18. Coriolis Effect • Click on image to watch video

  19. The Coriolis Effect The Coriolis Effect describes the apparent deflection of an object based on the rotation of the Earth below it.

  20. The Coriolis Effect Objects appear to deflect to the right in the northern hemisphere and to the left in the southern hemisphere http://nsidc.org/cryosphere/arctic-meteorology/images/coriolis.gif

  21. Rotating Earth Model • When the effect of rotation is added to the global circulation model, thetwo-cell convection system breaks down into many smaller cells. http://sparce.evac.ou.edu/q_and_a/images/bc07.gif

  22. Rotating Earth Model •These cells lead to the formation of the global wind belts.

  23. Circulation on a Rotating Earth

  24. Wind Belts

  25. WIND BELTS • Trade windsare two belts of winds that blow almost constantly from easterly directions • From 0o to 30olatititude • Warm, moist, rising air (low pressure)

  26. WIND BELTS • Westerliesare the prevailing winds that blow west-to-east in the middle latitudes • From 30o to 60olatititude

  27. Wind Direction • ThePREVAILING WIND is the wind that blows more often from one direction than from any other. • In the United States, the WESTERLIESconsistently move weather from west to east across the continent.

  28. WIND BELTS • Polar easterlieswinds that blow from the polar high toward the subpolarlow. • From 60o to 90olatitudes. • Cold and dry air masses

  29. WIND-LESS BELTS • Doldrumsconverging trade winds at the equator (O latitude) creating calm areas • Horse latitudesdiverging westerlies and trade winds (easterlies) create calm at approximately 30 latitude

  30. The Jet Stream • Jet streams form at boundaries between convection cells; • High speed winds • Blow in upper troposphere and lower stratosphere

  31. Identify the Wind Belts Click on the link below to see the wind belts in action and answer some questions! http://meted.ucar.edu/hurrican/strike/orig/htc5_1.htm

  32. Global Winds Influenced by Continents • The only truly continuous pressure belt is the subpolar low in the Southern Hemisphere. • In the Northern Hemisphere, where land masses break up the ocean surface, large seasonal temperature differences disrupt the pressure pattern.

  33. Energy from Wind

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