1. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory WRF-CMAQ 2-way coupled system: Part I David Wong, Jonathan Pleim, Rohit Mathur, Robert Gilliam, Tanya Otte, Jeffery Young NERL/AMD Frank Binkowski and Aijun Xiu Institute for the Environment, UNC CMAS 08 October 6-8, 2008

2. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Outline  Current operation scheme  Motivation  Coupling issues  Design and features  Overall coupled structure  Preliminary results

3. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Current operation scheme

4. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Motivation  Shortcomings of the current way of running met model- MCIP-CMAQ 32-bit data storage in files excessive data interpolation lack of feedback (direct and indirect effect) from CMAQ to the met model

5. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Coupling Issues  Compatibility of met model and CMAQ model physical aspects computational aspects  Coupling tool

6. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Coupling Issues: compatibility  Model physical aspects map projection coordinate system and grid format layer structure time step size etc

7. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Coupling Issues: compatibility (cont’d)  Computational aspects domain decomposition processor and subdomain mapping

8. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Coupling Issues: compatibility (cont’d)  Runtime System Library, RSL  RSL (MM5 and WRF), RSL-Lite (WRF)  RSL-Lite is slightly faster than RSL

9. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory

10. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory

11. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Coupling Issues: Tools  Earth System Modeling Framework (ESMF)  Other choices: OpenMI (UK), Model Coupling Toolkit (MCT) (ANL)  M3IO IOAPI Buffered file

12. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Design Strategy  Maintain integrity of WRF and CMAQ models  Minimal code changes: Keeping the same IOAPI calls Easy to incorporate new version of WRF  Efficiency: Low coupling overhead buffered file for data transfer (forward and backward) buffered file always holds two time steps of data allowing interpolation  Flexibility: easy to add feedback parameters and outputs

13. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory

14. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Features  Flexible time stepping CMAQ can be called every WRF timestep or at any user defined multiple  Simple run time switch of feedback  Subdomain tracking  Switch back to disk I/O file for uncoupled mode

15. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory WRF-CMAQ system overview WRFCMAQ Solve.F physics drivers dynamics aq_prep CMAQ (time,  t) aerosol data radiation microphysics emission data vdiff biogenic emis plume rise surface flux hadv zadv hdiff cldproc chem aero feedback initial conditions boundary conditions met data

16. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Example of a call frequency ratio of 4 time line

17. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Preliminary results Offline – 4:1 O3PM25

18. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Preliminary results (cont’d) 4:1 – 1:1 O3PM25

19. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Run Exec. Time Met Only MCIP Offline CMAQ Inline Model 4:1 Inline Model 1:1 Execution time 4:45:02 2:15:23 0:04:21 2:25:18 4:52:07 9:02:52

20. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Preliminary results (cont’d) 4:1 w/o – w/ feedback O3PM25

21. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Preliminary results (cont’d) w/ feedback 4:1 – 1:1 O3PM25

22. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Preliminary results (cont’d) w/ feedback 4x8 – 2x4 O3PM25

23. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Execution time (cont’d) Exec. time w/o feedbackw/ feedbackcase 2x4 1:1 4:1 4x4 4x8 16:36:04 8:18:00 9:34:28 5:20:56 5:55:10 3:34:47 9:26:11 5:13:50

24. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory To be continued …