1. Ozone Production Efficiency in the Baltimore/Washington Urban Plume Presentation by Linda Hembeck Co-Authors: Christopher Loughner, Timothy Vinziguerra, Timothy Canty, Russell Dickerson, and Ross Salawitch 13 th Annual CMAS Conference October 28 th, 2014

2. Content Motivation Background Ozone Production Efficiency (OPE) in CMAQ and DISCOVER-AQ 2011 Maryland data using BEIS or MEGAN for biogenic emissions Comparisons of trace gas species between model output and data Summary 2

3. Motivation Elevated levels of tropospheric ozone have a negative impact on human health and crops Comparison of measured and modeled surface O 3 is where we begin and end, but accurate representation of surface O 3 precursors is vitally important, especially for meaningful guide to policy Ozone production efficiency (OPE) provides a mechanism for quantitatively assessing air quality representation of key components of the photochemical evolution of urban plumes 3

4. CMAQ-BEIS v.3.14 July 2011; 10am – 7pm J. Hains 86% 2% 6% 4

5. CMAQ-MEGAN v.2.10 July 2011; 10am – 7pm J. Hains 85% 2% 5% 8% 5

6. O 3 CMAQ-BEIS vs. P3-B CMAQ-BEIS over estimates O 3 in the mixed layer J. Stehr 6

7. O 3 CMAQ-MEGAN vs. P3-B CMAQ-MEGAN over estimates O 3 in the mixed layer J. Stehr 7

8. Ozone Production Efficiency (OPE) OPE: Number of O 3 molecules produced per molecule of NO x, before NO x is further oxidized and converted to reservoirs Slope of O x (O 3 +NO 2 ) vs NO z (NO y −NO x ) is empirical measure of OPE in an air pollution plume (Kleinman et al., 2002) OPE often plotted as function of maximum NO x in plume 8 OPE: 8.77 R 2 : 0.71

9. Ozone Production Efficiency (OPE) BEIS v. 3.14: Model MEGAN v. 2.10: Model P3-B: Observation J. Stehr 9 MEAN: 4.23 ±0.66MEAN: 5.08 ±0.43

10. NO x /NO y BEIS v. 3.14MEGAN v. 2.10 J. Stehr 10 Observation Model

11. OMI HCHO CMAQ-BEIS Slide in progress….will show comparison of OMI HCHO to CMAQ-BEIS and CMAQ-MEGAN This slide will support the findings from CMAQ comparisons to D-AQ data 11 OMI July 2011

12. OMI HCHO CMAQ-MEGAN Slide in progress….will show comparison of OMI HCHO to CMAQ-BEIS and CMAQ-MEGAN This slide will support the findings from CMAQ comparisons to D-AQ data 12 OMI July 2011 CMAQ July 2011

13. Formaldehyde BEIS v. 3.14MEGAN v. 2.10 J. Stehr 13 Observation Model

14. Isoprene BEIS v. 3.14MEGAN v. 2.10 J. Stehr 14 Observation Model

15. Constraining HO 2 and RO 2 15 NO + HO 2 → NO ₂ + OH(1) NO + RO 2 → NO ₂ + RO(2) NO ₂ + hv → NO + O(3) NO + O ₃ → NO ₂ + O ₂ (4) O + O ₂ + M → O ₃ + M(5) Assume O 3 and O to be in Steady State: Rearrange equation: inRO x ∑RO x

16. Inferred peroxy radicals inRO x BEIS v. 3.14MEGAN v. 2.10 J. Stehr 16 Observation Model

17. Summary NO x /NO y ratio is under-predicted in CMAQ: model places NO x into reservoirs more efficiently than occurs in the atmosphere Observed isoprene and HCHO are underestimated using BEIS 3.14 VOC emissions in CMAQ and overestimated using MEGAN 2.10 VOC emissions: i.e., it seems truth lies in between these two emission scenarios HO 2 & RO 2 inferred from D-AQ are ~factor of 2 higher than HO 2 & RO 2 in CMAQ Most importantly: empirical OPE is nearly a factor of 2 higher than in CMAQ, suggesting surface O 3 may be more responsive to NO x controls than indicated by CMAQ 17

18. Work in Progress Assess model performance with a 50% reduction of mobile NO x emissions (Anderson et al. 2014): preliminary results show however most of the problems persist Use a more explicit chemical mechanism for NTR such as introduced by Donna Schwede on Monday Implement the new BEIS mentioned during this conference into CMAQ Assess differences between this work, based on CB05, and CMAQ runs based on CB06 18

19. Questions? 19

20. Backup 20

21. NO x /NO y CMAQ-BEIS vs. P3-B J. Stehr CMAQ over estimates NO x /NO y in the mixed layer 21

22. NO x /NO y CMAQ-MEGAN vs. P3-B J. Stehr CMAQ over estimates NO y 22

23. NO y CMAQ-BEIS vs. P3-B J. Stehr CMAQ over estimates NO y 23

24. NO y CMAQ-BEIS vs. P3-B J. Stehr CMAQ over estimates NO y 24

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