CMAQ Chemical Transport Modeling System (CCTM)

1. CMAQ Chemical Transport Modeling System (CCTM) Gail Tonnesen, Zion Wang UCR Regional Modeling Center Training January 17, 2002

2. 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. CCTM Overview

3. 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 CCTM - Coming Attractions

4. CCTM Governing Equations • Chemistry: N coupled PDEs • Cj t + v.Cj  D2Cj +P LCj +Ej Dj , j=1,N • Operator Splitting: • Cj t = v.Cj • Cj t = 2Cj + Ej  Dj • dCj dt = P  L Cj j=1,N • Gear solver is the gold standard for stiff ODEs

5. 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

6. Operator Splitting (cont.) • Vertical Dispersion with emissions: • Cj t = z 2Cj z2 + Ej  Dj • Chemistry with emissions: • dCj dt = P  L Cj + Emisjj=1,N • Example of loss frequency (L) for XYL: • L = kOH+XYL [OH] • Loss Rate = L[XYL]

7. 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. Symmetrical Operator Splitting

8. 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; CCTM Modules

9. 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. CCTM – Science Modules (cont.)

10. CCTM – Science Module Choices

11. CCTM – Science Module Choices (cont.)

12. CCTM – Science Module Choices (cont.)

13. CCTM – Driver Module and Science Processor Call Sequence

14. 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. CCTM - Nesting

15. One-way nesting versus two-way nesting. CCTM – Nesting

16. CCTM – Multi-level Nesting

17. Verify that the CMAQ distribution tar file is downloaded from the RMC website: http:www.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 How to run CCTM?

18. Check the log file for possible compile and runtime errors. Sample error messages and solutions are included in the User’s Guide under “Why didn’t CCTM work” section. How to run CCTM (cont.)

19. Practice Session