Design and Development of MAQM, an Air Quality Model Architecture with Process-Level Modularity Weimin Jiang, Helmut Roth, Qiangliang Li, Steven C. Smyth, Fuquan Yang

CMAS Conference, Chapel Hill2Oct 1-3, 2007 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

CMAS Conference, Chapel Hill3Oct 1-3, 2007 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

CMAS Conference, Chapel Hill4 Oct 1-3, 2007 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. What did we do ?

The conceptual MAQM architecture

CMAS Conference, Chapel Hill6Oct 1-3, 2007 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.

CMAS Conference, Chapel Hill7Oct 1-3, 2007 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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Meteorology... Emission... Gas_chem... Advection

Meteorology... Emission... Gas_chem... Advection

11 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

12 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, D g,  g ) PMx_[yyyyddd]:total and speciated PM 0.01, PM 0.1, PM 1, PM 2.5, PM 5, PM 10 ; size cut-offs can be changed by users. –Conventional or SI units: user selected.

13 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

CMAS Conference, Chapel Hill14Oct 1-3, 2007 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.

CMAS Conference, Chapel Hill15Oct 16-18, 2006