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 Hill 2Oct 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 Hill 3Oct 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 Hill 4Oct 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

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aer o s o ls ,m eteo r o lo g y ,

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CMAS Conference, Chapel Hill 6Oct 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 Hill 7Oct 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

...

...

...

Meteorology

...

Emission

...

Gas_chemGas_chem

......

AdvectionAdvection

..................

Meteorology

...Emission

...

Gas_chemGas_chem

......

AdvectionAdvection

......

............

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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, g)

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

CMAS Conference, Chapel Hill 14Oct 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 Hill 15Oct 16-18, 2006