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

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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

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CMAQ-BEIS v.3.14July 2011; 10am – 7pm

J. Hains

86%

2%

6%

6%

4

CMAQ-MEGAN v.2.10July 2011; 10am – 7pm

J. Hains

85%

2%

5%

8%

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O3 CMAQ-BEIS vs. P3-B

CMAQ-BEIS over estimates O3 in the mixed layer

J. Stehr

6

O3 CMAQ-MEGAN vs. P3-B

CMAQ-MEGAN over estimates O3 in the mixed layer

J. Stehr

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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+NO

2) vs NO

z

(NOy−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

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OPE: 8.77R2: 0.71

Ozone Production Efficiency (OPE)

BEIS v. 3.14: Model MEGAN v. 2.10: Model

P3-B: Observation

J. Stehr

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MEAN: 4.23 ±0.66 MEAN: 5.08 ±0.43

NOx/NOy

BEIS v. 3.14 MEGAN v. 2.10J. Stehr

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Observation Observation

Model

Model

OMI HCHO CMAQ-BEIS

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

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OMI July 2011

OMI HCHO CMAQ-MEGAN

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

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OMI July 2011 CMAQ July 2011

Formaldehyde

BEIS v. 3.14 MEGAN v. 2.10J. Stehr

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Observation Observation

Model

Model

Isoprene

BEIS v. 3.14 MEGAN v. 2.10J. Stehr

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Observation Observation

Model

Model

Constraining HO2 and RO2

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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:

][][][][

][2221342

2 ROkHOkOkJNO

NONO

inROx ∑ROx

Inferred peroxy radicals inROx

BEIS v. 3.14 MEGAN v. 2.10J. Stehr

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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

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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

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Questions?

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Backup

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NOx /NOy CMAQ-BEIS vs. P3-B

J. Stehr

CMAQ over estimates NOx /NOy in the mixed layer

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NOx /NOy CMAQ-MEGAN vs. P3-B

J. Stehr

CMAQ over estimates NOy

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NOy CMAQ-BEIS vs. P3-B

J. Stehr

CMAQ over estimates NOy

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NOy CMAQ-BEIS vs. P3-B

J. Stehr

CMAQ over estimates NOy

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