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Orographic influences in a Great Salt Lake-effect snowstorm

Orographic influences in a Great Salt Lake-effect snowstorm. Trevor Alcott, Jim Steenburgh 19 th U.S./Canada Great Lakes Operational Meteorology Workshop Ithaca, NY - 22 Mar 2011. Project Objectives. Identify and quantify various orographic effects on Great Salt Lake-effect precipitation

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Orographic influences in a Great Salt Lake-effect snowstorm

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  1. Orographic influences in a Great Salt Lake-effect snowstorm Trevor Alcott, Jim Steenburgh 19th U.S./Canada Great Lakes Operational Meteorology Workshop Ithaca, NY - 22 Mar 2011

  2. Project Objectives • Identify and quantify various orographic effects on Great Salt Lake-effect precipitation • Generalize results for other lake-orographic scenarios • 4 project components • Updated (1997-2010) event climatology • Real case simulations / sensitivity studies • Idealized model simulations • Field program Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 1/20

  3. You call that a lake? • Main body of GSL is 120 x 25 km • 5-20 LE events per year, mean 13 • Late fall, early spring peaks 15 SEP 15 NOV 15 JAN 15 MAR 15 MAY Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 2/20

  4. GSL Area Snake River Plain Raft River Mtns Wasatch Mtns Great Salt Lake Cedar Mtns Stansbury Mtns Oquirrh Mtns m Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 3/20

  5. Expected Orographic Effects • Upstream drying • Upstream wake • Flow channeling • Canyon flows • Direct orographic enhancement • Downstream drying Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 4/20

  6. Expected Orographic Effects • Upstream drying • Upstream wake • Flow channeling • Canyon flows • Direct orographic enhancement • Downstream drying Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 4/20

  7. Expected Orographic Effects • Upstream drying • Upstream wake • Flow channeling • Canyon flows • Direct orographic enhancement • Downstream drying Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 4/20

  8. Expected Orographic Effects • Upstream drying • Upstream wake • Flow channeling • Canyon flows • Direct orographic enhancement • Downstream drying Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 4/20

  9. Expected Orographic Effects • Upstream drying • Upstream wake • Flow channeling • Canyon flows • Direct orographic enhancement • Downstream drying Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 4/20

  10. Expected Orographic Effects • Upstream drying • Upstream wake • Flow channeling • Canyon flows • Direct orographic enhancement • Downstream drying Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 4/20

  11. Anatomy of a Utah winter storm L L H WARM, DRY, WINDY +36 h 0 -6 h +18 h -9 h -12 h -18 h Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 5/20

  12. Anatomy of a Utah winter storm L L H WARM, DRY, WINDY DUST STORM +36 h 0 -6 h +18 h -9 h -12 h -18 h Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 5/20

  13. Anatomy of a Utah winter storm L L H WARM, DRY, WINDY SEVERE WINDS DUST STORM +36 h 0 -6 h +18 h -9 h -12 h -18 h Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 5/20

  14. Anatomy of a Utah winter storm L L H WIDESPREAD RAIN WARM, DRY, WINDY SEVERE WINDS DUST STORM +36 h 0 -6 h +18 h -9 h -12 h -18 h Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 5/20

  15. Anatomy of a Utah winter storm L L H WIDESPREAD RAIN WARM, DRY, WINDY SEVERE WINDS WIDESPEAD SNOW DUST STORM +36 h 0 -6 h +18 h -9 h -12 h -18 h Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 5/20

  16. Anatomy of a Utah winter storm L L H WIDESPREAD RAIN WARM, DRY, WINDY SEVERE WINDS WIDESPEAD SNOW LAKE-EFFECT DUST STORM +36 h 0 -6 h +18 h -9 h -12 h -18 h Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 5/20

  17. Anatomy of a Utah winter storm L L H WIDESPREAD RAIN WARM, DRY, WINDY SEVERE WINDS WIDESPEAD SNOW CLEAR AND COLD LAKE-EFFECT DUST STORM +36 h 0 -6 h +18 h -9 h -12 h -18 h Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 5/20

  18. Anatomy of a Utah winter storm L L H SHALLOW COLD POOL BAD AIR QUALITY WIDESPREAD RAIN WARM, DRY, WINDY SEVERE WINDS WIDESPEAD SNOW CLEAR AND COLD LAKE-EFFECT DUST STORM +36 h 0 -6 h +18 h -9 h -12 h -18 h Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 5/20

  19. Transitions can be abrupt… 17 Feb 2011 Example 999 956 53 33 * 2 27 30 00:53 UTC 01:40 UTC Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 6/20

  20. 5 Nov 2008 Event 300 mb 500 mb 06 UTC 4 Nov 700 mb SFC Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 7/20

  21. 5 Nov 2008 Event 300 mb 500 mb 18 UTC 4 Nov 700 mb SFC Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 7/20

  22. 5 Nov 2008 Event 300 mb 500 mb 06 UTC 5 Nov 700 mb SFC Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 7/20

  23. 5 Nov 2008 Event 300 mb 500 mb 18 UTC 5 Nov 700 mb SFC Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 7/20

  24. 5 Nov 2008 Event 09 UTC 21UTC 12 UTC 15 UTC Alta-Collins Snow Study Plot (Elev. 2945 m) 23 in snow in 16 h Rates up to 5 in h-1 2008-09 total: 696 in Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 8/20

  25. 12 km 1.33 km 5 Nov 2008 Simulations WRF-ARW version 3.1.1 Kain-Fritch Cu (12,4), Lin et al. MP, YSU PBL, NOAH LSM, Simple diffusion 4 km CONTROL NO-UP-TERRAIN NO-DOWN-TERRAIN Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 9/20

  26. Upstream Drying hPa Ɵ, RELATIVE HUMIDITY X 500 600 Y 700 800 900 0 50 100 150 200 km Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 10/20

  27. Upstream Wake m/s WIND SPEED CONVERGENCE 20 10 0 Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 11/20

  28. Upstream Wake Observations hPa 18Z 25 Oct 2010 °C hPa 03 Z 9 Nov 2010 °C Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 12/20

  29. Orographic Parcel Modification A B 600 mb A 700 mb 800 mb 900 mb B 600 mb 700 mb 800 mb 900 mb Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 13/20

  30. Removal of Upstream Terrain CONTROL NO UPSTREAM TERRAIN TOTAL PRECIPITATION 0 10 20 30 40 50 60 mm Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 14/20

  31. No Upstream Orography hPa RELATIVE HUMIDITY (NO-UP-TERRAIN MINUS CONTROL) 500 600 700 800 900 0 50 100 150 200 km Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 15/20

  32. Flow Channeling Complications CONTROL NO UPSTREAM TERRAIN CONVERGENCE Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 16/20

  33. Canyon/Downslope Flows Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 17/20

  34. Removal of Downstream Terrain CONTROL NO DOWNSTREAM TERRAIN TOTAL PRECIPITATION 0 10 20 30 40 50 60 mm Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 18/20

  35. Removal of Downstream Terrain CONTROL NO DOWNSTREAM TERRAIN CONVERGENCE Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 19/20

  36. Conclusions • Upstream topography: • considerable drying at low levels prior to interaction with the Great Salt Lake (GSL) • removal yields 40-80% more precipitation • Downstream topography • Yields orographic ratios of 3:1 to 5:1 • Orography directly enhances LE band and modifies position/intensity of convergence zones • Removal yields 60-90% reduction in precipitation Alcott/Steenburgh Orographic Influences in a Great Salt Lake-effect snowstorm 20/20

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