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Measured and modelled ozone photochemical production in the Baltimore-Washington airshed
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2019
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Source: Atmospheric Environment: X, 2, 100017
[PDF-3.43 MB]
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Journal Title:Atmospheric Environment: X
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Description:Ozone production efficiency (OPE) represents the number of ozone (O3) molecules produced per molecule of NOx (NO2+NO), before NOx is converted to a sink or reservoir species. Observations from NASA's July 2011 DISCOVER-AQ (D-AQ) campaign in the Baltimore-Washington region are used to quantify OPE, which is compared to output from the Community Multiscale Air Quality (CMAQ) model. The baseline model run of CMAQ (CB05-TUCL mechanism; mobile NOx emissions from the National Emissions Inventory; biogenic emissions from BEIS model v3.61) underestimates observed OPE by 34 ± 20%. The payload of D-AQ lacked direct observations of HO2 and RO2, so we infer the rate at which these peroxy radicals react with NO (termed inROx) from observations of NO, NO2, O3, and j(NO2). The baseline run of CMAQ underestimates inROx by 35 ± 19%. A modified run of CMAQ with a factor of 10 reduction in the lifetime of organic nitrates, a factor of 2 reduction in mobile NOx emissions, an update to the thermal dissociation rate of PAN and PANX to the IUPAC 2014 value, and a correction for the rate constant for OH + PANX results in better overall model performance based on a number of comparisons to data that include column NO2 measured by the Ozone Monitoring Instrument, a value of OPE that is 21 ± 13% less than observed, and inROx that is low by 30 ± 19%. Sensitivity analysis indicates that the peroxy radical discrepancy involves either emission of VOCs other than isoprene or HCHO, or a problem with the model production of HO2 and RO2. Our analysis suggests surface O3 may exhibit stronger declines to further reductions of NOx than is indicated by baseline runs of CMAQ.
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Source:Atmospheric Environment: X, 2, 100017
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ISSN:2590-1621
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Rights Information:CC BY-NC-ND
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