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Class #6: Wednesday, July 14 Small scale and local winds

Class #6: Wednesday, July 14 Small scale and local winds. Chapter 9. Wind: small scale and local systems. Chapter 9. Small-scale winds interacting with the environment. Scales of motion Micro, meso, synoptic Friction and Turbulence in Boundary Layer Laminar flow

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Class #6: Wednesday, July 14 Small scale and local winds

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  1. Class #6: Wednesday, July 14 Small scale and local winds Chapter 9 Class #6, Wednesday, July 14, 2010

  2. Wind: small scale and local systems Chapter 9 Class #6, Wednesday, July 14, 2010

  3. Small-scale winds interacting with the environment • Scales of motion • Micro, meso, synoptic • Friction and Turbulence in Boundary Layer • Laminar flow • Irregular turbulent motion • Planetary boundary layer (PBL) • Depth of PBL Class #6, Wednesday, July 14, 2010

  4. Class #6, Wednesday, July 14, 2010

  5. Class #6, Wednesday, July 14, 2010

  6. Class #6, Wednesday, July 14, 2010

  7. Class #6, Wednesday, July 14, 2010

  8. Class #6, Wednesday, July 14, 2010

  9. Class #6, Wednesday, July 14, 2010

  10. Small-scale winds interacting with the environment • Observations: Eddies & Air Pockets • Eddies on leeward side of solid object • Roll eddies, mountain wave eddy (clear air turbulence) • Increase wind speed/shear deforms layer into wave and air pocket. • Force of the Wind • Bridges and hills or rises can modify wind, increasing the force at specific locations. Class #6, Wednesday, July 14, 2010

  11. Small-scale winds interacting with the environment • Microscale winds blowing over the Earth’s surface • Wind erosion, desert pavements, sand ripples • Snow ripples, snow dunes, snow rollers, snow fences • Windbreak, shelter belt Class #6, Wednesday, July 14, 2010

  12. Class #6, Wednesday, July 14, 2010

  13. Class #6, Wednesday, July 14, 2010

  14. Class #6, Wednesday, July 14, 2010

  15. Determining wind speed and direction • Wind characterized by direction, speed, and gustiness • Wind direction describes the direction from which it is blowing • Topic: Pedaling in the Wind • As wind blows against an object it exerts force (V2 or P x A) Class #6, Wednesday, July 14, 2010

  16. Class #6, Wednesday, July 14, 2010

  17. Class #6, Wednesday, July 14, 2010

  18. Determining wind speed and direction • Influence of Prevailing Winds • Prevailing most frequently observed direction during a given time period • Impact human and natural landscape • Wind rose • Topic: Wind Power • Turbines need moderate, steady winds • Only a few percent of nation’s total energy needs generated by wind power in the first half of the century Class #6, Wednesday, July 14, 2010

  19. Determining wind speed and direction • Wind Measurements • Wind vane • Pressure plate anemometer • Cup anemometer • Aerovane • Rawinsonde • Wind soundings • Observations: Winds from space • QuickScat: scatterometer Class #6, Wednesday, July 14, 2010

  20. Local Winds • Thermal circulation • Heating and cooling of the atmosphere above the ground create cold, core high and warm, core low pressure cells. • Wind travels from high to low and rises until it cools and begins to sink. Class #6, Wednesday, July 14, 2010

  21. Local Winds • Sea and Land Breeze • Uneven heating of land and water • Day: land hot, water cold = sea breeze • Night: water hot, land cold = land breeze • Sea breeze front, sea breeze convergence • Local Winds and Water • Local winds will change speed and direction as they cross a large body of water due to less friction, greater speed and greater Coriolis effect Class #6, Wednesday, July 14, 2010

  22. Class #6, Wednesday, July 14, 2010 Fig. 9-22, p. 239

  23. Class #6, Wednesday, July 14, 2010 Fig. 9-23, p. 239

  24. Class #6, Wednesday, July 14, 2010

  25. Class #6, Wednesday, July 14, 2010

  26. Stepped Art Class #6, Wednesday, July 14, 2010 Fig. 9-25, p. 241

  27. Class #6, Wednesday, July 14, 2010

  28. Class #6, Wednesday, July 14, 2010

  29. Class #6, Wednesday, July 14, 2010

  30. Local Winds • Seasonally Changing Winds: The Monsoon • Arabic for seasonal • Winds change direction seasonably causing extreme dry and wet season • Eastern and southern Asia, North America Class #6, Wednesday, July 14, 2010

  31. Class #6, Wednesday, July 14, 2010

  32. Class #6, Wednesday, July 14, 2010

  33. Local Winds • Mountain and Valley Breeze • On mountain slopes, warm air rises during the day creating a valley breeze; during night nocturnal drainage of cool air creating a mountain breeze • Associated with cumulus clouds in the afternoon • Katabatic winds • Cold wind rushes down elevated slopes, usually 10 kts or less but can reach hurricane strength Class #6, Wednesday, July 14, 2010

  34. Class #6, Wednesday, July 14, 2010

  35. Class #6, Wednesday, July 14, 2010

  36. Local Winds • Chinook/Foehn Winds • Dry warm descending on the leeward side of a orographic barrier • Eastern slope of Rockies (chinook), Europe (foehn), Argentina (zonda) • Focus: Snow Eaters • Thirsty wind on east side of Rockies that eat or melt snow due to rapid change in temperature Class #6, Wednesday, July 14, 2010

  37. Class #6, Wednesday, July 14, 2010

  38. Local Winds • Santa Anna Winds • Warm dry that blows from east or northeast don canyons into S. California • Very fast, desiccates vegetation, providing fuel for fires • Desert winds • Dust storms, sand storms, dust devil, haboob Class #6, Wednesday, July 14, 2010

  39. Class #6, Wednesday, July 14, 2010

  40. Class #6, Wednesday, July 14, 2010

  41. Class #6, Wednesday, July 14, 2010

  42. Wind: small scale and local systems Chapter 9 Class #6, Wednesday, July 14, 2010

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