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WRF-CMAQ 2-way Coupled System: Part II

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. WRF/CMAQ development work group. Jonathan Pleim David Wong Rohit Mathur Robert Gilliam

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WRF-CMAQ 2-way Coupled System: Part II

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  1. 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. WRF/CMAQ development work group • Jonathan Pleim • David Wong • Rohit Mathur • Robert Gilliam • Shawn Roselle • Jeff Young • Tanya Otte • Jerry Herwehe • George Pouliot

  3. 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. 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. 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. Scattering coefficient Mie approximation Extinction coefficient Asymmetry Factor

  7. 2-way test #1 (Eastern US) • WRF-CMAQ • Dx = 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. 2-Way Coupled WRF-CMAQ SystemDirect Effects Test; August 6, 2008 : 22Z Aerosol Optical Depth Surface PM2.5

  9. SW radiation at sfc: feedback-no feedback filtered for PM2.5 > 5mg/m3 unfiltered

  10. 2-m Temperature: feedback-no feedback filtered for PM2.5 > 5mg/m3 unfiltered

  11. PBL ht: feedback-no feedback filtered for PM2.5 > 5mg/m3 unfiltered

  12. Direct Feedback effects on AQfeedback – no feedback Slight increases in O3 in the aerosol impact area PM2.5 changes both ways

  13. Direct effect on surface SW radiation compared to CAM default and Bondville SURFRAD measurements

  14. 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. WRF-CMAQ w/feedbackminusWRF-CMAQ w/o feedback

  16. SW radiation compared to measurements in CA

  17. Temperature verification at selected sites in CA

  18. 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 mg/m3) during typical summer conditions in the EUS compared to CAM defaults • California Fire case shows much larger impacts on SW, T2m, PBL hts, O3 and PM2.5 • Preliminary evaluation shows better meteorological performance for T2m and SW • Direct feedbacks seem to be important only in higher polluted regions

  19. 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. 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. Thank You Disclaimer: Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

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