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Development and Application of a State-of-the-Science Plume-in-Grid Model CMAQ-APT

Development and Application of a State-of-the-Science Plume-in-Grid Model CMAQ-APT. Prakash Karamchandani, Christian Seigneur, Krish Vijayaraghavan and Shiang-Yuh Wu, AER, San Ramon, CA Alan Hansen and Naresh Kumar EPRI, Palo Alto, CA CMAQ Workshop, October 2002. Plume-in-Grid Modeling.

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Development and Application of a State-of-the-Science Plume-in-Grid Model CMAQ-APT

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  1. Development and Application of aState-of-the-Science Plume-in-Grid ModelCMAQ-APT Prakash Karamchandani, Christian Seigneur, Krish Vijayaraghavan and Shiang-Yuh Wu, AER, San Ramon, CA Alan Hansen and Naresh Kumar EPRI, Palo Alto, CA CMAQ Workshop, October 2002

  2. Plume-in-Grid Modeling • 3-D air quality models create an artificial dilution of stack emissions • lower concentrations of plume material • unrealistic concentrations upwind of stack • incorrect chemical reaction rates • incorrect representation of transport • Subgrid-scale representation of plumes can remove some or all of these major limitations

  3. Previous PiG Models • Previous Plume-in-Grid (PiG) models include PARIS, URM, UAM-V, CAMx and CMAQ • All these PiG representations had limitations due to a simplified treatment of plume dispersion (empirical or first-order diffusion), simplified chemical mechanism in some cases and no effect of turbulence on plume chemistry

  4. CMAQ-APT • Development of a new PiG model that uses the state-of-the-science for the host model (CMAQ) and the plume model (SCICHEM) • SCICHEM includes advanced treatments for plume dispersion (second-order diffusion) and chemistry (multistage mechanism, effect of turbulence) • CMAQ with Advanced Plume Treatment (APT)

  5. Plume Dispersion • SCICHEM uses the SCIPUFF framework to simulate plume dispersion • A myriad of puffs is released from the source to represent the plume • Puffs are split when they become too large so that the effect of wind shear and turbulence on plume dispersion are properly characterized • Puffs that overlap are merged

  6. Plume Chemistry • Plume chemistry is simulated with a chemical kinetic mechanism that evolves through three stages as the plume becomes dispersed into the background air (Karamchandani et al., 2000) • Effect of turbulence on plume chemistry can be simulated • Crosswind plume resolution can be improved by using more puffs • SCICHEM has been evaluated with plume data from SOS 95 and SOS 99

  7. Evolution of Plume Chemistry 3 2 Long-range Plume Dispersion Early Plume Dispersion Mid-range Plume Dispersion 1 Reduced VOC/NOx/O3 chemistry — acid formation from OH and NO3/N2O5 chemistry NO/NO2/O3 chemistry Full VOC/NOx/O3 chemistry — acid and O3 formation

  8. SCICHEM/CMAQ Interface Domain, grid information Geophysical data Meteorological data Deposition velocities Emissions, IC/BC I/O API I/O API chemical concentrations Models-3 CMAQ SCICHEM Point source emissions I/O API I/O API Output concentrations and deposition Dump puffs Output puff information chemical concentrations

  9. Plume Dumping Criteria • Chemical criterion: the plume has become chemically mature as determined by reaching the third stage of plume chemistry and a given threshold for the plume concentration ratio of O3 / (O3 + NO2) • Physical criterion: the plume width must exceed the host model grid size

  10. CMAQ-APT Application • Eastern United States with two nested grid domains (12 and 4 km resolution) • Episode of 11 to 15 July 1995 • MM5 simulation of Seaman and Michelson (2000) • Thirty largest NOx point sources simulated with APT • Simulation with CMAQ and CMAQ-APT • CMAQ-APT is about 1.6 times slower than CMAQ for this simulation

  11. CMAQ Surface O3 Concentrations13 July 1995, 3 p.m. 12 km domain

  12. Effect of APT PiG Treatment onSurface O3 Concentrations13 July 1995, 3 p.m. CMAQ-APT - CMAQ 12 km domain

  13. Effect of Point Source NOx Emissionson Surface O3 Concentrationswithout PiG Treatment CMAQ - Background 12 km domain

  14. Effect of Point Source NOx Emissionson Surface O3 Concentrationswith APT PiG Treatment CMAQ-APT - Background 12 km domain

  15. CMAQ Surface HNO3 Concentrations13 July 1995, 3 p.m. 12 km domain

  16. Effect of APT PiG Treatment onSurface HNO3 Concentrations13 July 1995, 3 p.m. CMAQ-APT - CMAQ 12 km domain

  17. Effect of Point Source NOx Emissionson Surface HNO3 Concentrationswithout PiG Treatment CMAQ - Background 12 km domain

  18. Effect of Point Source NOx Emissionson Surface HNO3 Concentrationswith APT PiG Treatment CMAQ-APT - Background 12 km domain

  19. Conclusions • CMAQ-APT provides an improved representation of the impact of large point sources • For isolated point sources, CMAQ-APT predicts less impact on O3 formation (up to 80 ppb less) and less impact on HNO3 formation (up to 24 ppb less) • CMAQ-APT has been subjected to a comprehensive beta-testing by three organizations • It will be applied to the California San Joaquin Valley for several CCOS episodes

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