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CMAQ Model Development: Current Model Configuration and Future Plans

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  1. Shawn J. Roselle NOAA Atmospheric Science Modeling Division In partnership with the U.S. Environmental Protection Agency Research Triangle Park, NC CMAQ Model Development: Current Model Configuration and Future Plans ACCENT-CMAS Training Workshop on Air Quality Modeling, Sofia, Bulgaria August 6, 2006

  2. Summary • Background on modeling • Current model features • New developments on the horizon

  3. Background

  4. Role of Models in the Air Quality Planning Process • Air quality modeling is a major part of the United States’ implementation of the National Ambient Air Quality Standards (NAAQS) for ozone and PM2.5 • State-of-science models are needed in the State Implementation Plan (SIP) process

  5. Models are Central to the Air Quality Planning Process (cont.) • Multi-pollutant capabilities • O3, PM, acid/nutrient deposition, regional haze, air toxics, Hg • Multi-scale capabilities • Synthesize scale interactions between continental/ regional/ urban • Models are the only predictive tools to estimate emissions growth/change and the impacts of potential emissions control strategies on future-year air quality

  6. Categories of Air Quality Models • Dispersion models (traditional) • Steady-state Gaussian models • Receptor-oriented models • Diagnostic; not predictive • Provide data to indicate primary source categories affecting a receptor • Source-oriented models • Predictive, as well as diagnostic • Lagrangian or Eulerian frames of reference

  7. grid cell

  8. CMAQ Modeling System Fifth Generation Mesoscale Model (MM5) or Weather Research and Forecast Model (WRF) NOAA Weather Observations EPA Emissions Inventory Met-Chem Interface Processor (MCIP) Met. data prep SMOKE Anthro and Biogenic Emissions processing grid cell CMAQ AQ Model- Chemical-Transport Computations Hourly 3-D Gridded Chemical Concentrations

  9. Domains for Annual Simulations 36-km MM5 165 x 129 x 34 36-km CMAQ 148 x 112 x 14 12-km MM5 202 x 208 x 34 12-km CMAQ 199 x 205 x 14

  10. Meteorology • Penn State/NCAR Mesoscale Model-Gen. 5 (MM5) – community meteorology model • Principally used as a weather forecast model • MM5 is widely used in air quality community • Emphasis on processes important for air quality • Four-dimensional data assimilation (FDDA) • Resulting fields: model+observations • Weather Research and Forecast (WRF) is the successor model to MM5

  11. 12 UTC 22 July 1998 120-h simulation “Daily Weather Map” courtesy of NOAA Sample MM5 Output(36-km grids) MM5 Winds and Precipitation

  12. Meteorology (cont.) • ASMD meteorological model research • Land-surface modeling (Pleim-Xiu model) • Planetary Boundary Layer (PBL) processes • Linkage between meteorology/chemistry models (MCIP) • Four-dimensional data assimilation (FDDA in MM5) • NOAA’s Weather Research and Forecast (WRF) model testing and adaptation to CMAQ model system

  13. Emissions • Sparse Matrix Operator Kernel Emissions (SMOKE) system • Includes emissions from point, area, mobile, and natural sources • R&D for meteorologically-dependent emissions • VOCs from vegetation and NOx from soils (BEIS3) • Sea salt via wind/wave action • Wildland fires and prescribed burns • Blowing dust / agricultural sources of NH3

  14. Community Multiscale Air Quality (CMAQ) Model • Solves atmospheric transport-diffusion equations, with chemistry, aerosols, and other relevant processes • Time-splitting of science processes where i = chemical species x,y,z = 3-D space coordinates t = time p = processes

  15. Vertical transport and diffusion Horizontal transport and diffusion Chemistry, Aerosols Plume-in-grid Clouds Emissions

  16. CMAQ Response to Emissions Changes CMAQ Response to Emissions Changes

  17. CMAQ Model (cont.) • Current Research • Vertical diffusion • Boundary layer turbulence • Asymmetric Convective Model v2 • Deposition • Surface fluxes; land-surface modeling • Evaluation with flux field measurements • Plume-in-Grid • Sub-grid plume descriptions • Numerical algorithms • High performance computing

  18. CMAQ Model (cont.) • Gas-phase Chemistry • Chemical kinetic mechanisms • Carbon Bond (CB) series • Statewide Air Pollution Research Center (SAPRC) series • Mechanism adaptation and development of efficient numerical solvers

  19. Aitken Coarse Accumulation CMAQ Model (cont.) • Aerosols • Modal Approach • Thermodynamic gas/aerosol partitioning • Nucleation, condensation, coagulation • Heterogeneous chemistry • Secondary organic aerosol production • Inorganic aerosol chemistry

  20. Trimodal size distribution • Aitken (0-0.1 µm), Accumulation(0.1-2.5 µm), and Coarse • Gas/particle interactions treated for fine modes only – ISORROPIA instantaneous equilibrium • Fine-modes coagulate • Coarse mode, fine EC (black) & other fine PM (brown) are inert Binkowski and Roselle, JGR, 2002 HNO3 EC NO3- NH4+ SO4= Na+ Cl- H2O NH3 POA SOAa SOAb H2SO4 SVOCs Aromatics Other Monoterpenes HCl Na+, Cl-, SO42- Soil, Other H2O COARSE MODE 2 FINE MODES CMAQ Model (cont.)

  21. Chemical Species VOCs GasesParticles NO2 CO PAN NH3 ASO4I AECJ NO FORM ROR UMHP ASO4J A25I O3 ALD2 NTR ANH4I A25J O OLE FACD ANH4J ACORS NO3 ETH AACD ANO3I ASEAS O1D TOL CRES ANO3J ASOIL OH XYL TO2 AORGPAI NUMATKN HO2 ISOP OPEN AORGPAJ NUMACC N2O5 PAR CRO AORGBI NUMCOR HNO3 C2O3 MGLY AORGBJ AH2OI HONO XO2 ISPD AORGAI AH2OJ H2O2 XO2N SO2 AORGAJ DCV_Mie PNA PACD SULF AECI EXT_Mie PM2.5

  22. Recent chemical additions • Air toxics – 20 species in gas phase • Adding more toxics, including metals, semivolatiles, other Hazardous Air Pollutants (HAPs) • Atmospheric mercury • Modifications include new cloud/aqueous phase chemistry and gas phase reactions • CMAQ-Hg: first public release - March 2006

  23. Two CMAQ Development Tracks • Community version • Annual public releases (via CMAS) • Designed for retrospective modeling for policy and research • Multiple configurations • Air Quality Forecasting • Operational Ozone and PM forecasts • Integrated with NCEP forecast systems • Single optimized configuration

  24. Synergistic Development Community releaseAQF system Faster gas-phase chemical solver (EBI) Aerosol model upgrades And efficiency improvements Mass conservation scheme Modified minimum Kz Modified cloud cover and convective cloud transport New online photolysis model (work in progress) CB05 Chemical Mechanism

  25. Recent CMAQ Public Releases • September 2000: CMAQv4.0 • February 2001: CMAQv4.1 • June 2002: CMAQv4.2.1 • May 2003: CMAQv4.2.2 • September 2003: CMAQv4.3 • October 2004: CMAQv4.4 • September 2005: CMAQv4.5 • March 2006: CMAQv4.5.1

  26. CMAQv4.5 & v4.5.1 Highlights • Aerosols • Added sea salt (fine equilibrium; non-interactive coarse mode) • Updated ISORROPIA to v1.5 • Also recomputed tabulated binary activity coefficients • Updated aerosol dry deposition algorithm • Chemistry • Added CB4/chlorine chemistry and associated EBI solver • Added CB4/air toxics and SAPRC99/air toxics chemistry and associated EBI solvers • Beta-version of CB05 • Added degradation algorithm to the generalized solvers • Mercury • Added mercury modeling capability

  27. Chemical Mechanisms: CMAQv4.5.1

  28. CMAQv4.5 & v4.5.1 Highlights (continued) • Advection • New mass conservation scheme using vertical velocities derived from mass continuity • PBL modeling • New minimum Kz based on % urban land-use • Clouds • New sub-grid cloud mixing algorithm: vertical mixing algorithm based on Asymmetric Convective Model (ACM) • Aqueous Chemistry • Discontinued aerosol species lumping--separated elemental carbon from primary aerosol; split organic aerosols into primary, secondary biogenic, and secondary anthropogenic • Plume-in-Grid • Capability for more frequent plume releases

  29. CMAQv4.5 & v4.5.1 Highlights (continued) • Dynamic allocation of vertical layers • Enables same executable to be used for different vertical grid configurations • Parallel I/O • Added worker and I/O processors partition scheme • Diagnostic Tools • Sulfate and primary carbon tracking • Process Analysis • Updated for latest version of model processes • MCIP • Add capability for WRF-ARW • Dry dep. velocities for chlorine and mercury

  30. Diagnostic Tools – Carbon Tracking Fine Carbon from Diesel Exhaust Fine Carbon from Gasoline Exhaust Notes: • TCDiesel≈ 5 × TCGasoline • Both source categories track population density

  31. Diagnostic Tools – Carbon Tracking TC2.5 from Biomass Combustion TC2.5 from Food Cooking Notes: • TCBiomass is dominated by wildfires • TCFoodtracks population density

  32. Diagnostic Tools – Sulfate Tracking All scales represent the fraction of total aerosol sulfate.

  33. CMAQv4.6 Features

  34. Model Upgrades for 2006 • Aerosols • Updated ISORROPIA to v1.7 • Includes correction in activity coefficients for temperatures other than 298 K • Ammonium nitrate aerosol concentrations increase somewhat • Revised to use T, RH-dependent “gamma” (heterogeneous N2O5 reaction probability) from Evans & Jacob (2005) • Net production of nitrate decreases in the winter and increases slightly in the summer • Upper limit set for the RH input to ISORROPIA (95%) • Sets limits on the aerosol water concentrations • Previous versions of CMAQ could have water concentrations as high as 1000 ug/m3 • Updated parameters in the aerosol diagnostic file

  35. CMAQv4.6 Upgrades (cont.) • Chemistry • New Carbon Bond (CB05) mechanism and associated EBI solver • Summer ozone concentrations are about 8% higher compared with the CB4 mechanism • Include the gas-phase reactions involving N2O5 and H2O • Increases aerosol nitrate concentrations • Removed obsolete mechanism combinations (e.g. gas+aerosols w/o aqueous) • Carbon Apportionment and Sulfate Tracking • Added capability for CB05 (and AE4) mechanisms

  36. Chemical Mechanisms: CMAQv4.6

  37. CMAQv4.6 Upgrades (cont.) • PBL modeling • New ACM2: combined non-local and local closure scheme • Produces different vertical profiles of pollutants in the convective boundary layer (CBL) • Effective CBL mixing layer is shallower than for EDDY • Ground-level O3 concentrations slightly higher, especially in the late afternoon • Precursors emitted at ground level tend to have lower concentrations with more well mixed profiles in the CBL • Little effect on ground-level aerosol concentrations • Plume-in-Grid • Capability for AE4 mechanisms

  38. CMAQv4.6 Upgrades (cont.) • Circular buffer CGRID state file • Write restart file • Permits flexibility in the “CONC” file (write subset of species and layers) • Parallel I/O • Various updates (new version required for CMAQv4.6 compilation)

  39. Release Schedule • CMAS will release CMAQv4.6 to the public in September/October 2006 • Science description of new features • Will include a model evaluation report • Test datasets

  40. Future Work

  41. Work in progress • Develop on-line coupling capability for WRF-CMAQ • Allow aerosol feedback to radiation model • Closer temporal coupling between meteorology and chemistry • Integrated resolved-scale microphysics and aqueous chemistry • Aerosol effects on microphysics

  42. Work in progress (cont.) • Aerosols • Gas-phase interactions with coarse-mode sea salt • Incorporate a new SOA module for oxidation of aromatic, isoprene, and monoterpene mixtures • Photolysis • New in-line photolysis model for CMAQ • Hybrid of TUV (Madronich) and Fast-J (Prather) • 7 wavelength bands in UV and visible • Updated absorption cross-sections and quantum yields • Includes extinction and scattering by CMAQ aerosols • Effects of clouds will be added to on-line calculations

  43. Work in progress (cont.) • Cloud modeling • Collaboration with NOAA to adapt WRF/CHEM convective cloud model for CMAQ • CMAQ aqueous chemistry module • Wet deposition • Generalized aqueous chemistry solver • Develop operational satellite assimilation for • Surface insolation • Photolysis rates • Skin temperature nudging for soil moisture • Cloud dynamics

  44. CMAQ Model Limitations • Errors/uncertainties in input data • Initial and boundary conditions • Meteorology • Emissions • Gaps or incomplete understanding in process details or mathematical representations (e.g. VOC chemistry modeled using a lumped mechanism)

  45. CMAQ Model Limitations (cont.) • Issues of horizontal scale • Regional through urban modeling domains • Typical grid cell sizes: 1-40 km • Scale-dependent process parameterizations • For grid cell sizes >40 km: • Grid averaging can significantly affect results • Misrepresentation of emissions/chemistry at this scale • For grid cell sizes <1 km: • Resolving explicit atmospheric turbulence • Model parameterizations break down • Requires different modeling approaches(e.g. LES, CFD)

  46. Concluding Remarks • CMAQ and similar models are required tools for air quality planning • Such air quality models represent a complex atmospheric system, with uncertainties in each system component • Research is conducted using the models as “numerical laboratories”, in conjunction with laboratory and field data, to reduce the component uncertainties

  47. Concluding Remarks (cont.) • Modeling applications • Regulatory assessments of O3, PM2.5, air toxics, mercury • Acid/nutrient deposition • AQ/climate interactions