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Lab5

Lab5. 10/09/2013. Pressure Levels. 3 forces that control wind direction? PGF or HGF, Coriolis , Friction What is geostrophic wind? PGF = Coriolis Wind blows parallel to isobars and height lines Is friction greatest at low or high elevations? Low, because of the earth’s surface!

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Lab5

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  1. Lab5 10/09/2013

  2. Pressure Levels • 3 forces that control wind direction? • PGF or HGF, Coriolis, Friction • What is geostrophic wind? • PGF = Coriolis • Wind blows parallel to isobars and height lines • Is friction greatest at low or high elevations? • Low, because of the earth’s surface! • Friction slows the wind and reduces the effect of the coriolis force

  3. Friction • Air in motion near the earth’s surface is slowed by contact with the ground • The magnitude of friction is dependent on the “roughness” of the surface • Where is friction greater? Over land or over water?

  4. Friction

  5. Pressure and Boiling Water ScienceBlogs

  6. Pressure and Boiling Water:Higher Pressure (Lower Elevation) Boiling Water at high pressure Water vapor molecules Boiling Water

  7. Pressure and Boiling Water:Lower Pressure (Higher Elevation) Water vapor molecules Boiling Water

  8. Pressure Levels

  9. Pressure Levels and Friction • Surface Pressure • What is the height of the “surface” pressure? • Wind crosses isobars at a rather large angle

  10. Pressure Levels and Friction • 850mb-heights • Wind crosses height lines at a small angle

  11. Pressure Levels and Friction • 500mb-heights • Wind blows parallel to height lines

  12. Buys-Ballot’s Law • If you stand with the wind at your back on a constant pressure surface, lower heights (lower pressure) will be on your left in the Northern Hemisphere

  13. Jet Stream! • Vertical profile of winds measured at Caribou, ME • Mandatory Pressure Levels – pressure levels which radiosondes always take measurements

  14. Jet Stream • The jet stream is caused by differences in temperature between the tropics and the polar regions • The greater the temperature difference, the faster the jet stream • Remember: Pressure decreases faster in cold air than in warm air!!!!!!!!

  15. L H PGF

  16. North Pole North Pole 9800m 9950m 9950m 11000m 11000m Tropics Tropics Winter Summer

  17. *Jet Streaks Do you think it is faster to fly from Seattle to Boston, or from Boston to Seattle?

  18. Temperature and Altitude

  19. Buoyancy and Vertical Ascent • Less dense air rises • More dense air sinks • Think about a hot air balloon…why does it rise?

  20. Lab 5 Problems: • 6.13 • 6.18 a, b, c • 7.1 a, b, c • 7.2 b, c • 7.8 a, b, c • 7.10 a, b • 8.6 a, b

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