Design and Development of MAQM, an Air Quality Model Architecture with ProcessLevel Modularity

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Design and Development of MAQM, an Air Quality
Model Architecturewith Process-Level Modularity

• Weimin Jiang, Helmut Roth, Qiangliang Li,
• Steven C. Smyth, Fuquan Yang

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Outline

• Why is process-level (PL) modularity crucial for
  AQ models ?
• What did we do in initiating a new generation of
  AQ model with PL modularity?
• The conceptual MAQM architecture and its
  implementation in FORTRAN
• The MAQM/CMAQ model
• Possible future work
• Acknowledgements

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Why PL modularity ?

• Complicated atmos. processes rapidly evolving
  AQ science
• Air quality model with process-level modularity
• Simple transparent structure
• Transferable code
• Well structured model science algorithms
• Localised errors bugs
• Flexible process analysis capability.
• Broad community participation in model
  development and improvement
• Complete and robust model science

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What did we do ?

• MAQM a new software architecture for air quality
  models
• MAQM Modular Air Quality Model
• Treats processes as individual blocks
• Blocks can be added, removed, replaced, modified,
  reorganized.
• MAQM/CMAQ a 3-D air quality model based on the
  MAQM architecture and mostly on the CMAQ science
• Developed new pre-processors, MAQM data modules,
  the MAQM driver, and some MAQM process modules
• Extracted CMAQ algorithms/code and converted them
  into MAQM process modules
• Integrated all the pre-processors, MAQM data
  modules and MAQM process modules into a complete
  model.

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The conceptual MAQM architecture
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MAQM components design principles

• 2 types of structural components
• Status
• Process.
• 6 design principals
• Uniqueness of shared status information global
  status data repository
• Self-contained process modules
• Structural separation of process modules
• Structural separation and linkages of status and
  processes
• Simple MAQM driver and its interface with process
  modules
• Minimized usage of hardcoding and repetitive code.

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MAQM implementation in FORTRAN

• MAQM global status data repository a set of
  FORTRAN data modules
• MAQM process modules FORTRAN modules, sets
  of self-contained FORTRAN subroutines and/or
  functions
• Process modules access data module components via
  the USE statements and the ONLY option at any
  levels
• Simple MAQM driver calls to process modules one
  way passing of time stamp and time step only
• Example software structure of MAQM/CMAQ ? next
  slide

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MAQM/CMAQ details (1)

• saprc99_ae4_aq_SVOC mechanism
• Modified from saprac99_ae4_aq
• Processed through PROCCHEM chemical mechanism
  processor.
• Generalized CMAQ modal PM approach
• 5 global data modules grid, gas, aero, met,
  const
• 20 process modules optional and replaceable
• grid init_met int_gas
  init_aero
• BConc_gas BConc_aero emission
  gas_chem
• nucleation condensation inor_aero
  SOA
• coagulation advection diffusion
  cloud
• ddep_gas ddep_part meteorology
  output

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MAQM/CMAQ details (2)

• Inputs optional depending on the process
  modules used.
• IC and BC ASCII files allowing different
  concentrations in different grid cells
• Meteorology, emissions, photolysis same as
  CMAQ.
• Outputs
• Three output files in I/O API format for each
  day
• GasConc_yyyyddd gas concentrations
• Aero_Conc_yyyyddd modal aero quantities
  (conc, Dg, sg)
• PMx_yyyyddd total and speciated PM0.01,
  PM0.1, PM1, PM2.5, PM5, PM10
• size cut-offs can be changed by users.
• Conventional or SI units user selected.

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Possible future work

• Almost endless possibilities by the community,
  e.g.
• New/restructured models using the MAQM
  architecture
• Module-by-module science investigation and
  improvement
• New and alternative process modules
• Revised meteorology and emission modules to use
  input files from alternative sources
• On-line meteorology and/or emission modules
• Possibilities air quality
  meteorology
• 
  emission
• Time- and location-varying boundary conditions
• Process impact/sensitivity analysis

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Acknowledgements

• US EPA
• The CMAQ model
• Early ideas of AQM modularity
• Community modelling concept.
• All the organizations that contributed to the
  CMAQ code that we adapted/adopted.
• CMAS
• Distributing and supporting CMAQ and other
  relevant modelling tools
• Organizing and facilitating community-wide
  discussions.
• Dr. Jack Chen of our group comments and
  suggestions.

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