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WRF-CMAQ 2-way Coupled System: Part II

Explore feedback effects of aerosols on shortwave radiation in a 2-way coupled WRF-CMAQ system for climate and air quality research. The study compares aerosol characteristics and their impacts in two scenarios, showcasing the system's development and testing. Initial findings show varying effects on air quality metrics and meteorological parameters, highlighting the importance of direct feedback in high-polluted regions and during extreme events like wildfires. Future steps include assessing aerosol optical effects, tropospheric ozone impacts, and indirect feedback on cloud microphysics. Plan to expand the model globally for comprehensive climate-aq studies.

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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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