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Wind Science 101: I. Overview of Wind Patterns

Wind Science 101: I. Overview of Wind Patterns. Eugene S. Takle Professor Department of Agronomy Department of Geological and Atmospheric Science Director, Climate Science Program Iowa State University Ames, IA 50011. WESEP REU Short Course Iowa State University Spring 2011. Outline.

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Wind Science 101: I. Overview of Wind Patterns

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  1. Wind Science 101:I.Overview of Wind Patterns Eugene S. Takle Professor Department of Agronomy Department of Geological and Atmospheric Science Director, Climate Science Program Iowa State University Ames, IA 50011 WESEP REU Short Course Iowa State University Spring 2011

  2. Outline • Global scale • 3-D global circulation patterns and wind energy • Surface and upper-air tropical and mid-latitude weather systems, including prevailing westerlies • Mesoscale • Great Plains Low-Level Jet and nocturnal LLJs • Sea-breeze • Monsoon circulation • Off-shore resources • US wind resource maps • Forecasting wind resources • Atmospheric boundary layer • Structure and diurnal/seasonal evolution • Impact of static and dynamic stability on horizontal wind speeds and vertical profiles • Turbulent flows and interactive wakes

  3. http://eesc.columbia.edu/courses/ees/climate/lectures/gen_circ/index.htmlhttp://eesc.columbia.edu/courses/ees/climate/lectures/gen_circ/index.html

  4. Non-rotating Earth heated at its Equator Not to scale! Mean radius of the earth: 6371 km Height of the troposphere: 0-7 km at poles 20 km at Equator 90% of atmosphere is in the lowest 15 miles (24 km) 99% in lowest 30 miles (48 km)

  5. Global Precipitation Patterns

  6. To bring air from outside an airplane flying at 35,000 ft into the cabin, the compression to sea-level pressure would raise the air temperature to 430oC or 806oF

  7. NOAA NCEP-NCAR CDAS-1 MONTHLY 300 mb [ u , v ] climatology January Wind speed at 12 km

  8. NOAA NCEP-NCAR CDAS-1 MONTHLY 300 mb [ u , v ] climatology July Wind speed at 12 km http://eesc.columbia.edu/courses/ees/climate/lectures/gen_circ/300mbWinds.html

  9. NOAA NCEP-NCAR CDAS-1 MONTHLY Diagnostic above_ground [ u , v ] climatology (m/s) January Wind speed near surface http://eesc.columbia.edu/courses/ees/climate/lectures/gen_circ/300mbWinds.html

  10. NOAA NCEP-NCAR CDAS-1 MONTHLY Diagnostic above_ground [ u , v ] climatology (m/s) July Wind speed near surface http://eesc.columbia.edu/courses/ees/climate/lectures/gen_circ/300mbWinds.html

  11. NOAA NCEP-NCAR CDAS-1 DAILY 300 mb height (m) and winds (m/s) 1 Apr 1997 http://eesc.columbia.edu/courses/ees/climate/lectures/gen_circ/300mbWinds.html

  12. Continental and Regional influences • Continental scale circulation, jet streams • Great Plains Low-Level Jet • Coastal Jets • Sea breezes • Mountain-valley flows • Mountain compression of stream lines • Monsoons • Off-shore wind

  13. Mechanism of the Nocturnal Low-Level Jet: Great Plains Low-Level Jet (GPLLJ) Nocturnal Low-Level Jet (LLJ) Coastal Jet (CJ)

  14. Mechanism of the Nocturnal Low-Level Jet: Great Plains Low-Level Jet (GPLLJ) Nocturnal Low-Level Jet (LLJ) Coastal Jet (CJ)

  15. Fp L H Pressure Gradient

  16. Coriolis Force Fc = -2ΩxV Fc V L H Fp Pressure Gradient

  17. V Fc L H Fp Pressure Gradient

  18. Geostrophic Balance Vg Fp Fc L H

  19. V Fc Fp L H Ff Frictional Force Ff = -CdvV

  20. V Fc Fp L H At night, friction is eliminated, flow is accelerated, V increases

  21. V Fc Fp L H Coriolis force increase, wind vector rotates and speed continues to increase

  22. V Vg Fc Fp L H Wind vector rotates and speed continues to increase and exceeds geostrophic wind

  23. Rocky Mountains High Press Low Press High Temp Low Temp Missouri River

  24. Simulation of the Great Plains Low-Level Jet. Adam Deppe thesis, Iowa State University, 2010

  25. Mechanism of the Nocturnal Low-Level Jet: Great Plains Low-Level Jet (GPLLJ) Nocturnal Low-Level Jet (LLJ) Coastal Jet (CJ)

  26. Low Press High Press High Temp Low Temp

  27. Height above ground Nocturnal Jet Maximum (~200 m above ground) Horizontal wind speed

  28. Mechanism of the Nocturnal Low-Level Jet: Great Plains Low-Level Jet (GPLLJ) Nocturnal Low-Level Jet (LLJ) Coastal Jet (CJ)

  29. Low Press High Press Low Temp High Temp

  30. Coastal Mountains Low Press High Press Low Temp High Temp

  31. V Mountains produce an additional pressure force Fc Fp L H Ff Frictional Force Ff = -CdvV

  32. Take Home Messages • Winds are created by horizontal temperature difference (which create density differences and hence pressure difference) • Rotation of the Earth creates bands of high winds (prevailing westerlies) at mid-latitudes • Interactions with the day-night heating and cooling of the earth’s surface create changes in the vertical structure of the horizontal wind • Orographic feature (coastal regions, mountains, etc) create local circulations that enhance or decrease wind speeds

  33. Wind Science 101:Part II Eugene S. Takle Professor Department of Agronomy Department of Geological and Atmospheric Science Director, Climate Science Program Iowa State University Ames, IA 50011 Honors Wind Seminar Iowa State University Spring 2011

  34. Continental and Regional influences • Continental scale circulation, jet streams • Great Plains Low-Level Jet • Coastal Jets • Sea breezes • Mountain-valley flows • Mountain compression of stream lines • Monsoons • Off-shore wind

  35. H

  36. 100 km

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