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

  7. 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

  8. 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

  9. 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

  10. 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

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

  12. Mechanism of Low-Level Jets: General Principles Great Plains Low-Level Jet (GPLLJ) Nocturnal Low-Level Jet (LLJ) Coastal Jet (CJ)

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

  14. Fp L H Pressure Gradient

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

  16. V Fc L H Fp Pressure Gradient

  17. Geostrophic Balance Vg Fp Fc L H

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

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

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

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

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

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

  24. Bermuda High creates flow from the south in summer over the central US, which is accelerated at night by a terrain-induced pressure gradient H

  25. Wind speed as a function of height during the LLJ peak on March 24, 2009 at 1000 LST from the Lamont, OK wind profiler (Adam Deppe MS thesis, ISU, 2011)

  26. Height above ground Great Plains Low-Level Jet Maximum (~1,000 m above ground) ~1 km Horizontal wind speed

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

  28. Low Press High Press High Temp Low Temp

  29. V Vg Fc Fp L H

  30. Height above ground Nocturnal Low-Level Jet Maximum (~400 m above ground) ~400 m Horizontal wind speed

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

  32. Low Press High Press Low Temp High Temp

  33. Coastal Mountains Low Press High Press Low Temp High Temp

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

  35. Height above ground Coastal Jet Maximum (~50-400 m above ocean) ~50-400 m Horizontal wind speed

  36. Note high winds at mountain ridges

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