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A Study of Great Lakes Effects on Synoptic Processes by Using WRF Comparison Experiments

The Great Lakes Operational Meteorology Workshop 2014. A Study of Great Lakes Effects on Synoptic Processes by Using WRF Comparison Experiments. Chuliang Xiao 1 and Brent Lofgren 2 1 CILER , University of Michigan 2 NOAA GLERL. Ann Arbor, MI. Outline. Synoptic Overviews Data and Model

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A Study of Great Lakes Effects on Synoptic Processes by Using WRF Comparison Experiments

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  1. The Great Lakes Operational Meteorology Workshop 2014 A Study of Great Lakes Effects on Synoptic Processes by Using WRF Comparison Experiments Chuliang Xiao1 and Brent Lofgren2 1CILER , University of Michigan 2NOAA GLERL Ann Arbor, MI

  2. Outline • Synoptic Overviews • Data and Model • Results from Model Comparisons • Conclusions

  3. Outline • Synoptic Overviews • Low Patterns • Low Tracks • Data and Model • Results from Model Comparisons • Conclusions

  4. Synoptic Map (Deep Low) 17Nov2013 18Nov2013 Midwest Tornados outbreak Courtesy http://www.hpc.ncep.noaa.gov/dailywxmap/

  5. Synoptic Map (Shallow Low) 14Dec2013 15Dec2013 East-coast Snowstorm outbreak Courtesy http://www.hpc.ncep.noaa.gov/dailywxmap/

  6. Outlines and Centers 992 hPa 1012 hPa

  7. Outline • Synoptic Overviews • Data and Model • Datasets (NCEP Eta, FNL, SST, Station) • Model description • Experimental designs • Results from Model Comparisons • Conclusions

  8. Datasets • NCEP Eta (6 hourly, 40 km, North America) • NCEP FNL (6 hourly, ~100 km, Global) (for comparison with NCEP Eta) • NCEP RTG SST (Daily, HR, ~ 8 Km, Global) • MODIS (20-cat. Land Use; 16-cat. Soil; Collected in 2001) • Gauged Precipitation (Great Lake area)

  9. Datasets (Cont.)

  10. WRF (Version 3.5.1) Domain

  11. WRF Domain (Cont.) Lakes-mean: Only lake grids Area-mean: Red rectangle area Domain-mean: ALL model grids

  12. Experiment Comparison

  13. Landuse Modification CONTROL NOLakes

  14. Modification (Cont.)

  15. Modification (Cont.) • The land use, vegetation and soil categories were specified differently between Lake Superior and the other four lakes. • This allows small surface fluxes of heat and moisture to develop, but prevents any mechanical effects from discontinuities in surface roughness. The lake surface and substrate temperature were also altered in Sousounis and Fritsch (1994).

  16. Outline • Synoptic Overviews • Data and Model • Results from Model Comparisons • Validation (Precipitation) • Storm Evolutions (SLP) • Surface process (Temperature, Moisture, Heat flux) • Vertical extent (local circulation) • Local circulation <-> background flow • Conclusions

  17. Model Validation (Precipitation) Deep Low Shallow Low NCEP Eta 40km NCEP FNL 100km CONTROL 15km Observation

  18. Storm Evolutions (Area-mean SLP) Black: CONTRL RED: NOLakes Blue: SSTLakes Deep Low The bottom bars are the differences Shallow Low local time (EST)

  19. Surface process (Temperature) Black: CONTROL RED: NOLakes Blue: SSTLakes Lakes-Mean Surface Temp (TSK)  ColdLakes Lake temperature is not changed in the initial time, but got quick equilibrium in WRF-Noah Area-Mean Air Temp at 2 m (T2) Lakes-Mean TSK-T2 local time (EST)

  20. Surface process (Humidity) Vector: (qu, qv) Shading: ∇(qu, qv) q: mix ratio CONTROL CONTROL-NOLakes CONTROL-SSTLakes

  21. Surface process (Sensible Heat)

  22. Cross Sections 992 hPa Dashed: Southwest-Northeast 1012 hPa Dot: Northwest-Southeast

  23. Cross-sections Shading: Temperature; Contour: Geopotential Height NW-SE SW-NE

  24. Circulation Configuration Vector: U, V at 10 m Shading: T850 Contour: Z500 CONTROL CONTROL-NOLakes CONTROL-SSTLakes

  25. Conclusions • WRF performs well in simulating both the deep low and shallow low. • Lake-air temperature gradient induces vertical heat flux; lake-land roughness contrast contributes to moisture convergence. • The Great Lakes’ effect generally strengthens the low system near the surface but is sensitive to the background flow. • This effect becomes much more significant for the development of the shallow low and extends to a higher level, tilting downwind. • The remote influence of the Great Lakes tends to be subtle in both cases.

  26. Thank YOU

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