1. Template Reducing Vertical Transport Over Complex Terrain in Photochemical Grid Models Chris Emery, Ed Tai, Ralph Morris, Greg Yarwood ENVIRON International Corporation Novato, California 8 th Annual CMAS Conference Chapel Hill, NC October 20, 2009

2. Template 2 Introduction Regional photochemical models over predict springtime ozone throughout the inter-mountain western U.S. –CMAQ: 2002 WRAP –CAMx: 2005 FCAQTF –Typically ~20 ppb higher than remote measurements Results from stratospheric ozone levels in top model layer –Enters CMAQ/CAMx via lateral boundary conditions (BCs)  Derived from output of GEOS-CHEM global chemistry model Stratospheric ozone is too efficiently transported to surface over complex/high terrain –Rockies, Sierras, Cascades

3. Template 3 Introduction 2002 CMAQ Annual Max Daily 8-hour Ozone

4. Template 4 Introduction WRAP CMAQ and FCAQTF CAMx runs use 19 layers –Top layer spans 8-15 km –3 to 5 layers above PBL –MM5 run for 34 layers WRAP CMAQ and FCAQTF CAMx runs use 2002 BCs –Ozone in layer 19 range 100-300 ppb

5. Template 5 Introduction Contributors to high ozone over the Rockies: –High surface altitudes (2-3 km MSL)  Surface is closer to stratosphere –Deep PBL mixing and convection (through 4-6 km MSL)  Couple surface to mid-troposphere –Vigorous resolved vertical circulations (through 4-8 km MSL)  Transport layer 19 ozone downward Solutions we’ve identified in this study: –Coarse vertical grid structure (more aloft layers help) –GEOS-CHEM BC interface (improved interpolation helps) –Vertical advection technique (alternative approach helps)

6. Template 6 Approach Test bed: CAMx 2005 FCAQTF application –Inert, ozone only, no sources/sinks –Single 12-km regional grid covering western U.S. –Track ozone IC/BC over April 2005  Original IC/BC from 2002 GEOS-CHEM extraction (WRAP)  New IC/BC from 2005 GEOS-CHEM extraction Test and evaluate several ideas: –Modify input wind fields (smoothers, filters, etc.) –Improve treatment of CAMx top boundary condition –Test alternative vertical grid structures/resolution –Improve GEOS-CHEM interface technique –Modify CAMx vertical advection solver

7. Template 7 Modify Input Winds Original Rationale –Vertical velocity derived from input horizontal winds  CAMx and CMAQ “yamo” approaches are similar –Filter strong divergences in input winds to calm vertical velocity –Apply aggressively to upper layers only –Test on 19-layer structure and compare to un-modified case Three approaches were investigated –Smoother-desmoother approach of Yang and Chen (2008) –Divergence minimization from CALMET (Scire et al., 2000) –Mass filter of Rotman et al. (2004)

8. Template 8 Modify Input Winds Results –Minor (~10 ppb) reductions in peak April ozone –Troubling effects on vertical velocity profiles in upper layers –CAMx surface ozone reductions not caused by improved vertical advection  Instead by artificial dilution of top layer ozone  Caused by CAMx arbitrary top boundary condition (70 ppb) CAMx was revised to use “zero-gradient” top boundary conditions for all subsequent tests –Top BC assigned from top layer concentration (a la CMAQ) –Removes artificial dilution of top layer –BUT increases surface ozone

9. Template 9 More Model Layers Reprocess input meteorology, no smoothers/filters –Zero-gradient top boundary condition –Full 34 MM5 layer structure  Runs ~2x slower than 19 layers, 10-15 ppb ozone reduction –Intermediate 22 layers to improve resolution aloft  Runs ~1.1x slower than 19 layers, ~10 ppb ozone reduction 19-layer 22-layer 34-layer

10. Template 10 2005 Day-Specific BCs New 2005 GEOS-CHEM BCs recently became available –Zero-gradient top boundary condition –Much higher stratospheric ozone (occasionally ~1000 ppb)  Higher surface ozone, different spatial patterns –NOTE CHANGES TO COLOR SCALE! 19-layer 22-layer 34-layer

11. Template 11 2005 Day-Specific BCs Issues found in GEOS-CHEM interface program –High ozone bias in topmost layers for coarse vertical layer structures We improved the vertical layer-weighting technique –Figure below shows new ozone profiles

12. Template 12 Improved 2005 BCs Improved vertical weighting technique –Zero-gradient top boundary condition –Lower stratospheric ozone, lower surface ozone –Ozone still higher than with 2002 BCs –NOTE CHANGES TO COLOR SCALE! 19-layer 22-layer 34-layer

13. Template 13 Revised Vertical Advection Revised vertical velocity calculation to remove downward bias Revised vertical solver to be consistent –Zero-gradient top BC, improved lateral BC –40-70 ppb reduction in April maximum ozone 19-layer BASE MODIFIED ADVECTION

14. Template 14 Revised Vertical Advection Comparison of 19, 22, and 34-layer configurations –NOTE CHANGES TO COLOR SCALE! 19-layer 22-layer 34-layer

15. Template 15 Full Photochemical Run Run CAMx on 36/12/4-km FCAQTF grids for April and July 2005 Compare 3 runs: –Original 19-layer, 2002 BCs*, original vertical advection –New 22-layer, 2005 BCs, original vertical advection –New 22-layer, 2005 BCs, revised vertical advection Look at monthly maximum 8-hour ozone fields on 12 and 4 km grids *2002 BCs: stratospheric ozone levels removed in layer 19

16. Template 16 Full Photochemical Run April 2005, 4-km Grid 19-layer 22-layer 22-layer 2002 BCs 2005 BCs 2005 BCs Orig CAMx Orig CAMx Revised CAMx

17. Template 17 Full Photochemical Run April 2005, 12-km Grid 19-layer 22-layer 22-layer 2002 BCs 2005 BCs 2005 BCs Orig CAMx Orig CAMx Revised CAMx

18. Template 18 Full Photochemical Run July 2005, 4-km Grid 19-layer 22-layer 22-layer 2002 BCs 2005 BCs 2005 BCs Orig CAMx Orig CAMx Revised CAMx

19. Template 19 Full Photochemical Run July 2005, 12-km Grid 19-layer 22-layer 22-layer 2002 BCs 2005 BCs 2005 BCs Orig CAMx Orig CAMx Revised CAMx

20. Template 20 On-Going Work Additional testing of modified CAMx for full photochemical/PM applications –Complete 2005 FCAQTF Application; evaluate ozone and PM –O&G projects in Rocky Mountains –Denver SIP modeling CMAQ exhibits similar problems –EPA/ORD is working on a vertical advection modification  See Young, Pleim, Mathur poster –Interact with ORD and OAQPS –Test improvements using a western U.S. CMAQ database

21. Template 21 Acknowledgement The authors acknowledge funding support from the American Petroleum Institute (API) Questions…