1. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory WRF-CMAQ 2-way Coupled System: Part II Jonathan Pleim, David Wong, Rohit Mathur, Robert Gilliam, Tanya Otte, Jeffery Young NERL/AMD Frank Binkowski and Aijun Xiu Institute for the Environment, UNC

2. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory WRF/CMAQ development work group Jonathan Pleim David Wong Rohit Mathur Robert Gilliam Shawn Roselle Jeff Young Tanya Otte Jerry Herwehe George Pouliot

3. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Outline Part 1 (David Wong’s Presentation) Direct feedback of aerosols on SW radiation Testing of 2-way coupled system w/ direct feedback –Eastern US domain –California fires Conclusions

4. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Direct Feedback The aerosol species passed from CMAQ to WRF are combined for each mode as: –Water soluble = sulfate + ammonium + nitrate –Insoluble = POA + SOA_anthropogenic + SOA_biogenic + Other Primary –Elemental Carbon (EC) –Seasalt –Water Diameters and standard deviations are also passed from CMAQ to WRF

5. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Aerosol optics Volume weighted internally-mixed modal refractive indices for the 19 wavelength intervals. For volume fractions of EC > 60%, an external mixture is assumed with special treatment for the EC. A highly efficient Mie approximation is used to calculate extinction and scattering coefficients and asymmetry factors for each mode.

6. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Mie approximation Asymmetry Factor Scattering coefficient Extinction coefficient

7. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory 2-way test #1 (Eastern US) WRF-CMAQ –  x = 12km, 34 layers – 4:1 CMAQ/WRF timestep ratio –Eastern US –August 2-10, 2006 Direct feedback of aerosol effects on CAM SW radiation –Compare the optical effects of CMAQ’s aerosol characteristics to CAM default aerosol characteristics

8. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory 2-Way Coupled WRF-CMAQ System Direct Effects Test; August 6, 2008 : 22Z Aerosol Optical Depth Surface PM 2.5

9. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory SW radiation at sfc: feedback-no feedback unfiltered filtered for PM2.5 > 5  g/m 3

10. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory 2-m Temperature: feedback-no feedback unfiltered filtered for PM2.5 > 5  g/m 3

11. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory PBL ht: feedback-no feedback unfiltered filtered for PM2.5 > 5  g/m 3

12. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Slight increases in O 3 in the aerosol impact area PM2.5 changes both ways Direct Feedback effects on AQ feedback – no feedback

13. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Direct effect on surface SW radiation compared to CAM default and Bondville SURFRAD measurements

14. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory 2-way test #2 (California Fires) WRF-CMAQ run on small 12 km domain over CA with wild fire emissions June 20-30, 2008 –Sensitivity of met and AQ with and without direct feedback –Verification against SW radiation measurements and T-2m

15. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory WRF-CMAQ w/feedback minus WRF-CMAQ w/o feedback

16. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory SW radiation compared to measurements in CA

17. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Temperature verification at selected sites in CA

18. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Conclusions The WRF-CMAQ coupled system with direct feedback of aerosols on SW radiation has been successfully developed and tested Initial tests show small effects in areas of high PM2.5 concentration (>5  g/m 3 ) during typical summer conditions in the EUS compared to CAM defaults California Fire case shows much larger impacts on SW, T 2m, PBL hts, O 3 and PM2.5 –Preliminary evaluation shows better meteorological performance for T 2m and SW Direct feedbacks seem to be important only in higher polluted regions

19. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Next steps Further tests with aerosol optical effects on photolysis Test effects of tropospheric ozone on LW radiation Implement effects of aerosols on LW radiation Add indirect feedback: effects of aerosols on CCN and on resolved cloud microphysics Verification of meteorological and AQ results for longer simulations

20. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Application to Climate-AQ research Extend WRF-CMAQ to hemispheric or global coverage with nesting to regional scales –Hemispheric WRF-CMAQ would be forced by global climate simulations through: Global Climate Model sea surface temperatures GCM landuse-vegetation characteristics GHG radiative forcing consistent w/ GCM Newtonian nudging of WRF-CMAQ using GCM meteorological fields –Consistent global and regional chemistry –Contrast global GHG forcing with regional aerosol forcing

21. Office of Research and Development Atmospheric Modeling Division, National Exposure Research Laboratory Thank You Disclaimer: Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.