1. CRC NARSTO-Northeast Modeling Study
Ralph E. Morris, Edward Tai, and Greg Yarwood
ENVIRON International Corporation
101 Rowland Way
Novato, California 94945
Models-3 User’s Workshop hosted by CMAS
October 21-23, 2002
Research Triangle Park, North Carolina
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2. Acknowledgements
Coordinating Research Council (CRC) Atmospheric Impacts Committee (Brent Bailey, Coordinator)
Work performed with Alpine Geophysics, STI, and PSU
NARSTO acknowledged for data collection and analysis activities and comments
MM5 data provided by Nelson Seaman at PSU
NARSTO Data Analysis Study directed by Till Stoekenius at ENVIRON
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3. Purpose
Investigate sensitivity of photochemical grid models to inputs and options using the extensive July 1995 NARSTO-Northeast database:
Photochemical Grid Model (CMAQ vs CAMx)
Meteorological Model (MM5 vs RAMS)
Level of FDDA in MM5
VOC and/or NOx Emission Reductions
Grid Resolution (12-km vs 4-km)
Chemical Mechanism (CB-IV vs SAPRC97)
Advection Solver (Bott vs PPM vs Smolarkiewicz)
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4. Overview of Approach Minimize any interpolation of met data
LCP grid for MM5 met; PSP grid for RAMS met
MM5 run with 3 levels of FDDA
Analysis Nudging (AN) only
AN and Observation Nudging (ON)
AN, ON, and VAD nudging (FOBS)
CMAQ and CAMx sensitivity runs
36-km, 12-km, and 4-km nests
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5. G:\crca24\CMAS_workshop\CMAS_CRC_NARSTO.ppt

6. Emissions Processed by EMS95
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7. Difficulties Encountered/Lessons Learned
Emissions: Numerous delays were encountered waiting for the latest emissions that were not substantially different from the draft values.
CMAQ QSSA Chemistry Solver: QSSA chemistry solver is slow, inaccurate, and may go unstable so should not be used.
MAQSIP Modeling System: STI had difficulties getting MAQSIP to work which was believed to be due to not using the MAQSIP version of MM5.
Layer 1 Vertical Diffusivities: Both CMAQ (MCIP) and CAMx (MM5CAMx) modeling systems were updated during then study with a minimum layer 1 KV.
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8. Ozone Hourly Time Series in NYC Subdomain CAMx/MM5, CAMx/RAMS, CMAQ/MM5
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9. Daily Maximum Ozone -- July 14, 1995 CAMx/MM5 CMAQ/MM5 CAMx/RAMS
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10. Daily Maximum Ozone -- July 15, 1995 CAMx/MM5 CAMx/RAMS CMAQ/MM5
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11. 12-km vs 4-km Grids-- CMAQ July 14, 1995
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12. 12-km vs 4-km Grids -- CAMx July 14, 1995
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13. 12-km vs 4-km Grids -- CMAQ July 15, 1995
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14. 12-km vs 4-km -- CAMx July 15, 1995
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15. Comments on Grid Resolution Sensitivity
July CMAQ and CAMx 4-km ozone estimates more like each other than their 12-km parent
4-km ozone estimates generally lower than 12-km
CMAQ 4-km ozone smoother due to KH inversely proportional to grid spacing
July 15, 1995 very different response to 4-km grid:
MM5 4-km grid explicitly resolves convective activity with downdrafts etc.
Many other desirable features in MM5 4-km fields
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16. MM5 12-km vs 4-km Wind Field 07/15/95
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17. Emission Reduction Sensitivity Tests
Investigate sensitivity of ozone responses to 50% NOx and/or 50% VOC anthropogenic emission reductions:
Photochemical model: CMAQ vs. CAMx
Grid resolution: 12-km vs. 4-km (NOx only)
Chemical mechanism: CB-IV vs SAPRC97
Advection Solver: Bott vs Smolarkiewicz
Low-level vs Elevated NOx
Design Value Scaling for Four NE Sites
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18. 50% Anthropogenic VOC Reduction
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19. 50% Anthropogenic NOx Reduction
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20. Emission Reduction Sensitivity Conclusions
NOx reductions result in wide-spread decreases in ozone except in urban cores where increases sometimes occur
VOC reductions result in ozone reductions in urban cores but little change elsewhere
CAMx/MM5 is more VOC sensitive than either CMAQ/MM5 or CAMx/RAMS
SPARC97 chemistry is more VOC sensitive than CB-IV
Use of a 4-km grid increases the NOx disbenefits in CAMx/MM5 but has less effects in CMAQ/MM5
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21. Overall Conclusions
QSSA chemistry solver is slow and inaccurate and should not be used
Smolarkiewicz advection solver is overly diffusive and should not be used
CMAQ horizontal diffusion coefficient parameterization that is inversely proportional to grid resolution negates many of the benefits of high resolution grids
Meteorological modeling of convective activity should be studied for air pollution modeling
Ozone Design Value scaling can be very different using different models
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