Evidence for an increasing geographic region of influence on ozone air pollution in the eastern United States

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Meredith Riley
5 years ago
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Candidate Co-authors: Tim Canty, Tim Vinciguerra,

1 Evidence for an increasing geographic region of influence on ozone air pollution in the eastern United States Presentation by: Dan Goldberg, Ph.D. Candidate Co-authors: Tim Canty, Tim Vinciguerra, Ross Salawitch & Russ Dickerson Presented at the AQAST 9 th Semiannual Meeting Wednesday June 3 rd,

2 Motivation for this study The state of Maryland is very interested in the role of the interstate transport of ozone. Science objectives: How much ozone is generated locally vs. transported from upwind regions? What are the future trends in surface ozone? Is ozone being simulated for the right reasons? 1

3 Ozone Source Apportionment Examples MD The CAMx software can attribute ozone to different source regions. Surface ozone, once formed, can be transported 100 s km downwind from the original source. OH PA 2

Ozone from the model boundary Ozone attributed to areas beyond the model domain, i.e., Texas, Cal, Asia Ozone from the boundary is uniformly greater than 15 ppbv.

4 Ozone from the model boundary Ozone attributed to areas beyond the model domain, i.e., Texas, Cal, Asia Ozone from the boundary is uniformly greater than 15 ppbv. Some locations, especially close to the boundaries, are higher. 3

5 Summer 2011 & 2018: Ozone Source Attribution The attribution of ozone in all states decreases % over 7 years. The only portion to increase is the ozone attributed to the model boundary. Baltimore, MD BC=boundary conditions 4

Trends in the Apportionment of Surface Ozone Mean 8-hr max in Baltimore, MD Boundary and meteorology are initialized identically in each simulation.

6 Trends in the Apportionment of Surface Ozone Mean 8-hr max in Baltimore, MD Boundary and meteorology are initialized identically in each simulation. Total surface ozone has decreased and is projected to further decrease. Sources inside the model domain will decrease. If the sources outside the model domain remain the same, ozone attributed to these sources will increase. 5

Trends in the Apportionment of Surface Ozone Mean July percentage of ozone (%) attributed to the boundary Metropolitan Area 2002 2011 2018 New York, NY 37.0% 41.6% 45.

7 Trends in the Apportionment of Surface Ozone Mean July percentage of ozone (%) attributed to the boundary Metropolitan Area New York, NY 37.0% 41.6% 45.3% Philadelphia, What is PA causing 38.1% this increase??? 42.7% 47.6% Baltimore, MD 34.5% 38.8% 43.6% Washington, Ironically, DC we think 35.9% it s 41.0% related 46.5% to Mean July! concentration reductions of ozone in NO (ppbv) x and attributed VOCs to the boundary Metropolitan Area New York, NY Philadelphia, PA Baltimore, MD Washington, DC ! An increasing role of the boundary is seen in all metropolitan areas in the eastern United States. 6

As HNO 3 deposition decreases, the lifetime of ozone will

8 Change in O 3 lifetime due to less NO x Assuming 1 mol of O 3 is removed for every 1 mol of HNO 3 deposited. As HNO 3 deposition decreases, the lifetime of ozone will increase July 2002 July 2018 τ O3 = 29.0 days τ O3 = 36.8 days 7

9 HO 2 Chemistry in the eastern United States Mean July 2011 daytime (7 AM 7 PM EDT) HO 2 concentrations The HO 2 + O 3 reaction can be an important sink of O x (O 3 +NO 2 + ) when HO 2 >15 pptv. 8

10 Change in daytime HO 2 concentrations between July 2002 and 2018 Surface 1 km 2 km 5 km Daytime HO 2 concentrations are decreasing in most areas. This is increasing the lifetime of ozone when reaction with HO 2 is important. Ozone lifetime with respect to reaction with HO 2 increases from 9.0 to 9.5 days. 9

11 Change in daytime HO 2 concentrations between July 2002 and July 2018 (with VOC reductions ONLY) Surface 1 km 2 km 5 km Anthropogenic VOC reductions are partially (but not fully) responsible for the decrease in HO 2 concentrations. 10

Curtain plots of Ozone at the Boundary during July 2011

especially at the western boundary (which is the

12 Curtain plots of Ozone at the Boundary during July 2011 MOZART is marginally higher in the lower layers at all boundaries, except the Southeast. GEOS Chem has higher ozone in the mid troposphere, especially at the western boundary (which is the boundary that most often influences ozone in the eastern United States). Modeling domain 11

13 Prediction of O 3 precursors: Using DISCOVER-AQ data The comparison with data from the P3-B aircraft during DISCOVER-AQ MD shows a significant over prediction of NO y and a significant under prediction of HCHO. We ve made three changes to update the model, Beta : CB6r2 gas-phase chemistry (Old: CB05) MEGAN v2.1 biogenic emissions (Old: BEISv3.14) Reduce emissions from mobile sources by 50% (Anderson et al., 2014) 12

14 Prediction of O 3 : Using DISCOVER-AQ data Prediction of ozone is similar in each case, but how the ozone produced is much different. 13

the daytime of July 7, 2011 Baseline Beta The model

15 Policy Implications of the model updates Percentage of O 3 formed in a VOC-limited environment during the daytime of July 7, 2011 Baseline Beta The model will be more responsive to NO x emission changes. 14

16 Conclusions Boundary conditions play a critical role: Ozone from the boundary is larger by percentage and by concentration in future years. Nonlinearities associated with NO x and VOC emission reductions are responsible for an increase in the ozone lifetime. This is an unintended consequence of the policies to reduce these emissions. There are large differences between MOZART & GEOS- Chem aloft. Updates to the model to give a better prediction of NO y and HCHO. The model will respond better to reductions in NO x emissions, which is a better representation of what is happening in reality. 15

Recent Ozone Modeling Results

Recent Ozone Modeling Results Presentation by: Dan Goldberg, Ph.D. Candidate Co-authors: Tim Canty, Tim Vinciguerra, Ross Salawitch & Russ Dickerson Presented at the MARAMA Science Meeting Wednesday July