1. No category

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.3.14
July 2011; 10am – 7pm
J. Hains
6%
2%
86%
6%
4
CMAQ-MEGAN v.2.10
July 2011; 10am – 7pm
J. Hains
8%
2%
85%
5%
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O3 CMAQ-BEIS vs. P3-B
J. Stehr
CMAQ-BEIS over estimates O3 in the mixed layer
6
O3 CMAQ-MEGAN vs. P3-B
J. Stehr
CMAQ-MEGAN over estimates O3 in the mixed layer
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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+NO2) vs NOz
(NOy−NOx)
is
empirical
measure of OPE in an air
pollution plume (Kleinman et
al., 2002)
• OPE often plotted as function
OPE: 8.77
R2: 0.71
of maximum NOx in plume
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Ozone Production Efficiency (OPE)
P3-B: Observation
J. Stehr
BEIS v. 3.14: Model
MEAN: 4.23 ±0.66
MEGAN v. 2.10: Model
MEAN: 5.08 ±0.43
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NOx/NOy
BEIS v. 3.14
MEGAN v. 2.10
J. Stehr
Observation
Observation
Model
Model
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OMI HCHO
CMAQ-BEIS
Slide in progress….will show comparison of OMI HCHO to CMAQ-BEIS and
CMAQ-MEGAN
OMI
July 2011
This slide will support the findings from CMAQ comparisons to D-AQ data
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OMI HCHO
CMAQ-MEGAN
Slide in progress….will show comparison of OMI HCHO to CMAQ-BEIS and
CMAQ-MEGAN
CMAQ July 2011
OMI
July 2011
This slide will support the findings from CMAQ comparisons to D-AQ data
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Formaldehyde
BEIS v. 3.14
MEGAN v. 2.10
J. Stehr
Observation
Observation
Model
Model
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Isoprene
BEIS v. 3.14
MEGAN v. 2.10
J. Stehr
Observation
Observation
Model
Model
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Constraining HO2 and RO2
NO + HO2
NO + RO2
NO₂ + hv
NO + O₃
O + O₂ + M
→
→
→
→
→
NO₂ + OH
NO₂ + RO
NO + O
NO₂ + O₂
O₃ + M
(1)
(2)
(3)
(4)
(5)
Assume O3 and O to be in Steady State:
[O3 ]SS =
j3[NO2 ]
k4 [NO]
Rearrange equation:
[NO2 ] k4 [O3 ]
=
[NO]
j3
[ NO2 ]
 J NO 2  k 4  [O3 ]  k1  [ HO2 ]  k 2  [ RO2 ]
[ NO]
inROx
∑ROx
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Inferred peroxy radicals inROx
BEIS v. 3.14
MEGAN v. 2.10
J. Stehr
Observation
Observation
Model
Model
16
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
CMAQ over estimates NOx /NOy in
the mixed layer
J. Stehr
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NOx /NOy CMAQ-MEGAN vs. P3-B
CMAQ over estimates NOy
J. Stehr
22
NOy CMAQ-BEIS vs. P3-B
CMAQ over estimates NOy
J. Stehr
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NOy CMAQ-BEIS vs. P3-B
CMAQ over estimates NOy
J. Stehr
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