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New Features of the 2003 Release of the CMAQ Model

New Features of the 2003 Release of the CMAQ Model. Jonathan Pleim 1 , Gerald Gipson 2 , Shawn Roselle 1 , and Jeffrey Young 1 1 ASMD, ARL, NOAA, RTP, NC 2 AMD, NERL, USEPA, RTP, NC. What’s new in CMAQ 2003. Updates to science Updates to Nitrate aerosol and Nitric acid

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New Features of the 2003 Release of the CMAQ Model

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  1. New Features of the 2003 Release of the CMAQ Model Jonathan Pleim1, Gerald Gipson2, Shawn Roselle1, and Jeffrey Young1 1 ASMD, ARL, NOAA, RTP, NC 2 AMD, NERL, USEPA, RTP, NC

  2. What’s new in CMAQ 2003 • Updates to science • Updates to Nitrate aerosol and Nitric acid • Updates to Secondary Organic Aerosols • Efficiency improvements • Faster chemistry solver • Modified model time stepping • Other updates and corrections • Air Quality Forecasting

  3. Nitrate Previous release (2002) shows large overprediction of Nitrate aerosol and Nitric acid

  4. Dry Deposition (winter) Added explicit resistance to snow and ice with dependence on temperature (melting) Modified cuticle resistance for NH3 as function of relative humidity Added wet ground similarly to wet canopy Revised model produces much greater Vd for NH3 thus reducing ammonium nitrate aerosol concentrations Heterogeneous and Gas-Phase Reactions Gas-phase nitric acid also greatly overpredicted Identified key pathway: N2O5 + H2O --> 2HNO3 Revised the heterogeneous reaction rate Turned off gas phase reaction Nitrate related changes

  5. Heterogeneous N2O5 Reaction • 2002 release • Reaction probability γ = 0.1 recommended by Dentener and Crutzen (JGR 1993) • Makes a lot of HNO3 at night • Recent studies show wide range of γ values • Dependence on humidity, temperature, chemical composition - sulfate, nitrate, and organic content • Updated version • Reaction probabilityγ= 0.002 - 0.02 depending on NO3/(SO4+NO3) according to Riemer et al. (JGR 2003) based on lab measurements of Mentel et al (PCCP 1999)

  6. 2003 release vs 2002 release Aerosol Nitrate Gas Phase Nitric Acid January 4 – 20, 2002

  7. CMAQ02 vs CMAQ03 - Nitrate Nitrate Aerosol CMAQ03 Nitrate Aerosol CMAQ02 Nitrate Aerosol diff Total Nitrate diff Average concentrations January 4 – 20, 2002

  8. Secondary Organic Aerosols • Corrections to Gas-Particle partitioning to allow reversibility • Lowers SOA concentrations by 60-70% • SOA precursor factors for SAPRC99 • 57% of ALK5 (longer chain alkanes) • 93% of ARO1 (less reactive aromatics) • Eliminated SOA from olefins • SOA production in CB4 unchanged • No production from alkanes or olefins • 100% of aromatics

  9. Organic Carbon Aerosol June 15 – 29, 1999 Jan. 4 - 20, 2002

  10. CMAQ02 vs CMAQ03 - SOA Total SOA CMAQ03 Total SOA CMAQ02 Total SOA Ratio: 03/02 Total SOA diff Averageconcentrations June 15 – 29, 1999

  11. Changes for improved efficiency • Euler Backward Iterative (EBI) solver • EBI uses analytical solution for two chemical groups rather than numerical solution used in MEBI • EBI about twice as fast as MEBI • Currently for CB4 only • Eliminated transport for radical species • Layer dependent advection time steps • Synchronization time step set by Courant condition in lower layers (up to sigma=0.7) • Multiple advection steps allowed in upper layers • Maximum sync time step changed to 12 min and minimum to 1 min for improved accuracy

  12. Other Updates • Cloud processes and aqueous chemistry • Updated equilibrium constants • Corrected vertical diffusion of aerosols (density -> mixing ratio) • Reordered operators • Vertical diffusion with emissions • Advection (x,y,z) • Horizontal diffusion • Clouds • Gas chem • Aerosols

  13. Updates to other system components • Latest MCIP - version 2.2 • Major corrections to layer interpolation of winds and vertical velocity (v2.1) • Updated dry deposition for both M3dry and RADMdry • Emission modeling (George’s Presentation)

  14. AQF System • NWS Eta model forecasts • Interpolated to 22 layer CMAQ grid • Hourly output with additional variables • AQF version of CMAQ • Optimized for massive parallel system • New version of MCIP called Premaq • Testing this past summer (2003): • 48 hr forecasts starting at 12z • 30 hr forecasts starting at 6z • 6 hourly cycling

  15. AQF Ozone – Aug 14, 2003

  16. Future Work • EBI for SAPRC99 • New mass conservation technique • New PBL models • CB4-2002 • New advection schemes • WRF connections • Source apportionment for primary aerosols • Coarse aerosol improvements • Sectional aerosol models • Continued performance improvements

  17. Further information • EPA’s CMAQ website: www.epa.gov/asmdnerl/models3/cmaq.html • Click on Model changes for more detailed description of changes for the 2003 release • Click on Announcements and then on Performance Evaluation for the August 2003 Release of CMAQ for a powerpoint presentation

  18. Related ASMD Presentations • Brian Eder: Evaluation results • 2003 release of CMAQ • AQF CMAQ • George Pouliot: latest developments in emission modeling • Jason Ching: Air toxic modeling • Shaocai Yu: • Diagnostic analysis of CMAQ SOA • Poster: Primary and secondary SOA • Poster: Thermodynamic aerosol models • Jeff Arnold: CMAQ Sensitivity to vertical mixing • Jeff Young: Parallel CMAQ

  19. AQF Ozone – Aug 15, 2003

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