1. 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

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

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

4. Nitrate related changes Dry Deposition (winter) Dry Deposition (winter) Added explicit resistance to snow and ice with dependence on temperature (melting)Added explicit resistance to snow and ice with dependence on temperature (melting) Modified cuticle resistance for NH 3 as function of relative humidityModified cuticle resistance for NH 3 as function of relative humidity Added wet ground similarly to wet canopyAdded wet ground similarly to wet canopy Revised model produces much greater V d for NH 3 thus reducing ammonium nitrate aerosol concentrationsRevised model produces much greater V d for NH 3 thus reducing ammonium nitrate aerosol concentrations Heterogeneous and Gas-Phase Reactions Heterogeneous and Gas-Phase Reactions Gas-phase nitric acid also greatly overpredictedGas-phase nitric acid also greatly overpredicted Identified key pathway: N 2 O 5 + H 2 O --> 2HNO 3Identified key pathway: N 2 O 5 + H 2 O --> 2HNO 3 Revised the heterogeneous reaction rateRevised the heterogeneous reaction rate Turned off gas phase reactionTurned off gas phase reaction

5. Heterogeneous N 2 O 5 Reaction 2002 release 2002 release Reaction probability γ = 0.1 recommended by Dentener and Crutzen (JGR 1993)Reaction probability γ = 0.1 recommended by Dentener and Crutzen (JGR 1993) Makes a lot of HNO 3 at nightMakes a lot of HNO 3 at night Recent studies show wide range of γ values Recent studies show wide range of γ values Dependence on humidity, temperature, chemical composition - sulfate, nitrate, and organic contentDependence on humidity, temperature, chemical composition - sulfate, nitrate, and organic content Updated version Updated version Reaction probability γ = 0.002 - 0.02 depending on NO 3 /(SO 4 +NO 3 ) according to Riemer et al. (JGR 2003) based on lab measurements of Mentel et al (PCCP 1999)Reaction probability γ = 0.002 - 0.02 depending on NO 3 /(SO 4 +NO 3 ) according to Riemer et al. (JGR 2003) based on lab measurements of Mentel et al (PCCP 1999)

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

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

8. Secondary Organic Aerosols Corrections to Gas-Particle partitioning to allow reversibility Corrections to Gas-Particle partitioning to allow reversibility Lowers SOA concentrations by 60-70%Lowers SOA concentrations by 60-70% SOA precursor factors for SAPRC99 SOA precursor factors for SAPRC99 57% of ALK5 (longer chain alkanes)57% of ALK5 (longer chain alkanes) 93% of ARO1 (less reactive aromatics)93% of ARO1 (less reactive aromatics) Eliminated SOA from olefinsEliminated SOA from olefins SOA production in CB4 unchanged SOA production in CB4 unchanged No production from alkanes or olefinsNo production from alkanes or olefins 100% of aromatics100% of aromatics

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

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

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

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

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

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

15. AQF Ozone – Aug 14, 2003

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

17. Further information EPA’s CMAQ website: EPA’s CMAQ website: www.epa.gov/asmdnerl/models3/cmaq.html Click on Model changes for more detailed description of changes for the 2003 releaseClick 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 presentationClick 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 Brian Eder: Evaluation results 2003 release of CMAQ2003 release of CMAQ AQF CMAQAQF CMAQ George Pouliot: latest developments in emission modeling George Pouliot: latest developments in emission modeling Jason Ching: Air toxic modeling Jason Ching: Air toxic modeling Shaocai Yu: Shaocai Yu: Diagnostic analysis of CMAQ SOADiagnostic analysis of CMAQ SOA Poster: Primary and secondary SOAPoster: Primary and secondary SOA Poster: Thermodynamic aerosol modelsPoster: Thermodynamic aerosol models Jeff Arnold: CMAQ Sensitivity to vertical mixing Jeff Arnold: CMAQ Sensitivity to vertical mixing Jeff Young: Parallel CMAQ Jeff Young: Parallel CMAQ

19. AQF Ozone – Aug 15, 2003