Ozone Production Efficiency in the Baltimore/Washington Urban Plume

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 13th Annual CMAS Conference October 28th, 2014

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

Motivation • Elevated levels of tropospheric ozone have a negative impact on human health and crops • Comparison of measured and modeled surface O3 is where we begin and end, but accurate representation of surface O3 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

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

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

O3 CMAQ-BEIS vs. P3-B J. Stehr CMAQ-BEIS over estimates O3 in the mixed layer

O3 CMAQ-MEGAN vs. P3-B J. Stehr CMAQ-MEGAN over estimates O3 in the mixed layer

Ozone Production Efficiency (OPE) • OPE: Number of O3 molecules produced per molecule of NOx, before NOx is further oxidized and converted to reservoirs • Slope of Ox (O3+NO2) vs NOz(NOy−NOx) is empirical measure of OPE in an air pollution plume (Kleinman et al., 2002) • OPE often plotted as function of maximum NOx in plume OPE: 8.77 R2: 0.71

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

NOx/NOy BEIS v. 3.14 MEGAN v. 2.10 J. Stehr Observation Observation Model Model

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 OMI July 2011

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 CMAQ July 2011 OMI July 2011

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

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

Constraining HO2 and RO2 NO + HO2 → NO₂ + OH (1) NO + RO2 → NO₂ + RO (2) NO₂ + hv → NO + O (3) NO + O₃ → NO₂ + O₂ (4) O + O₂ + M → O₃ + M (5) Assume O3 and O to be in Steady State: Rearrange equation: inROx ∑ROx

Inferred peroxy radicals inROx BEIS v. 3.14 MEGAN v. 2.10 J. Stehr Observation Observation Model Model

Summary • NOx/NOy ratio is under-predicted in CMAQ: model places NOx 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 • HO2 & RO2 inferred from D-AQ are ~factor of 2 higher than HO2 & RO2 in CMAQ • Most importantly: empirical OPE is nearly a factor of 2 higher than in CMAQ, suggesting surface O3 may be more responsive to NOx controls than indicated by CMAQ

Work in Progress • Assess model performance with a 50% reduction of mobile NOx 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

Questions?

Backup

NOx/NOyCMAQ-BEIS vs. P3-B CMAQ over estimates NOx /NOy in the mixed layer J. Stehr

NOx /NOyCMAQ-MEGAN vs. P3-B CMAQ over estimates NOy J. Stehr

NOy CMAQ-BEIS vs. P3-B CMAQ over estimates NOy J. Stehr

Ozone Production Efficiency in the Baltimore/Washington Urban Plume