CMAQ Chemical Transport Modeling System CCTM

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CMAQ Chemical Transport Modeling System (CCTM)

• Gail Tonnesen, Zion Wang
• UCR Regional Modeling Center Training
• January 17, 2002

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CCTM Overview

• CMAQ is a one atmosphere model
• Simulates O3, PM, Haze, acid deposition.
• Chemical Tracer Model (CCTM) simulates the
  following processes
• Advection, diffusion, and deposition,
• Gas phase chemistry,
• Particle dynamics, chemistry, and visibility,
• Plume-in-grid (PinG) modeling,
• Cloud processes,
• Photolysis rates, and
• Analysis tools.

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CCTM - Coming Attractions

• Additional major extensions are planned
• A version of the SAPRC-97 gas phase mechanism
• A new emissions processor called the Sparse
  Matrix Operator Kernel Emissions modeling system
  (SMOKE)
• an advanced surface-PBL linked system
• optional meteorological processors such as the
  Regional Atmospheric Modeling System (RAMS)
• an advanced 4-D photolysis rates processor

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CCTM Governing Equations

• Chemistry N coupled PDEs
• ?Cj ??t v.?Cj ? D?2Cj P ?LCj Ej ?Dj , j1,N
• Operator Splitting
• ?Cj ??t ? v.?Cj
• ?Cj ??t ??2Cj Ej ? Dj
• dCj ?dt P ? L Cj j1,N
• Gear solver is the gold standard for stiff ODEs

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• Advective Transport ?Cj ??t ? v.?Cj
• ?Cj ??t ?vx ?Cj ??x
• ?Cj ??t ?vy ?Cj ??y
• ?Cj ??t ?vz ?Cj ??z
• Horizontal Diffusion ?Cj ??t ??2Cj
• ?Cj ??t ?x ?2Cj ??x2
• ?Cj ??t ? y ?2Cj ??y2

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Operator Splitting (cont.)

• Vertical Dispersion with emissions
• ?Cj ??t ?z ?2Cj ??z2 Ej ? Dj
• Chemistry with emissions
• dCj ?dt P ? L Cj Emisj j1,N
• Example of loss frequency (L) for XYL
• L kOHXYL OH
• Loss Rate LXYL

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Symmetrical Operator Splitting

• Attempt to Minimize operator splitting errors by
  using a symmetrical solution.
• For a Ten Minute Simulation Period
• Solve Transport and Dispersion terms for
  beginning 5 minutes.
• Solve Chemistry for 10 minutes.
• Solve Transport and Dispersion terms for ending
  5 minutes.

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CCTM Modules

• Currently, nine science modules are included
• DRIVER controls model data flows and synchronizes
  fractional time steps
• HADV computes the effects of horizontal
  advection
• VADV computes the effects of vertical advection
• ADJCON adjusts mixing ratio conservation property
  of advection processes
• HDIFF computes the effects of horizontal
  diffusion
• VDIFF computes the effects of vertical diffusion
  and deposition

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CCTM Science Modules (cont.)

• CHEM computes the effects of gas-phase chemical
  reactions
• CLOUD computes the effects of aqueous-phase
  reactions and cloud mixing
• AERO computes aerosol dynamics and size
  distributions and
• PING computes the effects of plume chemistry.

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CCTM Science Module Choices
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CCTM Science Module Choices (cont.)
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CCTM Science Module Choices (cont.)
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CCTM Driver Module and Science Processor Call
Sequence
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CCTM - Nesting

• At present, CCTM allows only static grid nesting
• finer grids (FGs) are placed (i.e., nested)
  inside coarser grids (CGs)
• The resolution and the extent of each grid is
  determined a priori and remain fixed throughout
  the CTM simulation
• Static grid nesting conserves mass and preserves
  transport characteristics at the interfaces of
  grids with different resolutions
• It allows for effective interaction between
  different scales with efficient use of computing
  resources.

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CCTM Nesting

• One-way nesting versus two-way nesting.

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CCTM Multi-level Nesting
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How to run CCTM?

• Verify that the CMAQ distribution tar file is
  downloaded from the RMC website
  httpwww.cert.ucr.edu/rmc/download
• Gunzip and untar the tar file.
• Go to the CCTM run scripts directory, modify and
  execute the bldit and run job scripts.
• bldit script users choose the compilation
  options and compiling the code.
• run script users modify the run-time options
  and executing the CCTM processor

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How to run CCTM (cont.)

• Check the log file for possible compile and
  runtime errors.
• Sample error messages and solutions are included
  in the Users Guide under Why didnt CCTM work
  section.

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Practice Session