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Sensitivity Testing of CMAQ for Air Quality Modeling in the Eastern United States

This presentation discusses the CMAQ sensitivity testing and MM5 modifications to improve meteorological predictions in the Eastern U.S. Conducted at the University of Maryland, it highlights the challenges faced with the MM5 model, including boundary layer schemes and their impact on surface winds and temperatures. Key findings focus on aerosol and ozone measurements from flight campaigns in July 1997 and contrast model results against actual observations. Future work aims to refine boundary layer schemes to enhance simulation accuracy.

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Sensitivity Testing of CMAQ for Air Quality Modeling in the Eastern United States

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  1. CMAQ Sensitivity Testing for the Eastern United States Jeffrey W. Stehr Department of Meteorology University of Maryland October 22, 2002 Durham, NC, Models-3 Users’ Workshop

  2. Meteorology THE SIMULATION: Meteorology: • MM5 using Gayno-Seaman planetary boundary layer scheme • 24 vertical levels, 12 km (202 x 199) nest inside a 36 km domain • Analysis nudging to NCEP (Eta) reanalysis • There are problems with MM5!!!

  3. Meteorology: Modifying MM5 • University of Maryland (Zhang & Zheng) has modified the Blackadar boundary layer scheme to achieve better surface winds and temperatures • Other PBL schemes do a very poor job of it • These are thunderstorm, hurricane, and frontal models—who cares about a still, stagnant day? 

  4. Meteorology: Winds • Observations • Modified Blackadar • Winds from other PBL schemes have essentially nothing to do with reality • Comparisons by NYDEC

  5. Meteorology: Temperature(modified Blackadar) Temperature (K) Wind Speed (m/s) Data comparisons By NYDEC

  6. Photochemistry Emissions: • MEPPS with 1995 National Emissions Trends Inventory • NOT extrapolated to 1997 CMAQ: • 23 vertical levels, 110 x 80 (East-West x North-South) 12 km horizontal resolution • 72 hours of spinup before July 13 • CB4 chemical mechanism, MEBI solver

  7. Measurements THE AIRCRAFT: Instrumented Cessna-172* Chemistry: Ozone, Carbon Monoxide Meteorology: Relative humidity, Temperature, Pressure altitude *Currently, we fly a twin-engine Aztec with CO, O3, SO2, PSAP, T, RH, Palt, nephelometer, Met One counter, streaker—B. Doddridge, L. Marufu, B. Taubman

  8. The domain

  9. Measurement sites W05 WAY W42 HOL GAI W29

  10. Measurements • Examine: July 13-14, 1997 • Four measurement flights • Ozone data only (CO malfunctioned) • First show everything, then go back • Used the old MM5 data!

  11. KEY: CMAQ Aircraft Gaithersburg, MD

  12. Gettysburg, PA

  13. Holbrook, Southwestern PA

  14. Waynesburg, Southwestern PA

  15. Gettysburg, PA

  16. Fallston, MD (NE of Baltimore)

  17. Bay Bridge Airport Eastern Shore, July 14

  18. Waynesburg, Southwestern PA

  19. Waynesburg, Southwestern PA

  20. Gettysburg, PA

  21. Fallston, MD (NE of Baltimore)

  22. Measurements • July 13, Gettysburg PA—structure in both AM and PM flights, but not quite enough ozone. • July 13, Fallston MD—may be just outside the Baltimore plume. • July 14, Bay Bridge Airport—obviously, 12 km resolution just isn’t enough to get the Bay Breeze effects right. Our Met modelers suggest that maybe 2 km resolution will do it, probably 1 km resolution. AM PM

  23. Future • Compare CMAQ simulation results for this run and for a run with the new-and-improved MM5 PBL scheme. • This should help identify the role played by the boundary layer scheme in these simulations.

  24. Acknowledgements • Da-Lin Zhang & Weizhong Zheng, UMD MM5 modeling • Bruce Doddridge, Lackson Marufu, Brett Taubman, UMD aircraft measurements • Gopal Sistla, NYDEC, comparisons between MM5 and measurements • Fiscal Support: Maryland Department of the Environment

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