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| Titel |
Accounting for non-linear chemistry of ship plumes in the GEOS-Chem global chemistry transport model |
| VerfasserIn |
G. C. M. Vinken, K. F. Boersma, D. J. Jacob, E. W. Meijer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 22 ; Nr. 11, no. 22 (2011-11-23), S.11707-11722 |
| Datensatznummer |
250010215
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| Publikation (Nr.) |
 copernicus.org/acp-11-11707-2011.pdf |
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| Zusammenfassung |
| We present a computationally efficient approach to account for the non-linear
chemistry occurring during the dispersion of ship exhaust plumes in a global
3-D model of atmospheric chemistry (GEOS-Chem). We use a plume-in-grid
formulation where ship emissions age chemically for 5 h before being
released in the global model grid. Besides reducing the original ship
NOx emissions in GEOS-Chem, our approach also releases the secondary
compounds ozone and HNO3, produced during the 5 h after the original
emissions, into the model. We applied our improved method and also the widely
used "instant dilution" approach to a 1-yr GEOS-Chem simulation of global
tropospheric ozone-NOx-VOC-aerosol chemistry. We also ran simulations
with the standard model (emitting 10 molecules O3 and 1 molecule HNO3
per ship NOx molecule), and a model without any ship emissions at all.
The model without any ship emissions simulates up to 0.1 ppbv (or 50%) lower
NOx concentrations over the North Atlantic in July than our improved
GEOS-Chem model. "Instant dilution" overestimates NOx concentrations
by 0.1 ppbv (50%) and ozone by 3–5 ppbv (10–25%), compared to our improved
model over this region. These conclusions are supported by comparing simulated
and observed NOx and ozone concentrations in the lower troposphere over the
Pacific Ocean. The comparisons show that the improved GEOS-Chem model
simulates NOx concentrations in between the instant dilution model
and the model without ship emissions, which results in lower O3
concentrations than the instant dilution model. The relative differences in
simulated NOx and ozone between our improved approach and instant
dilution are smallest over strongly polluted seas (e.g. North Sea),
suggesting that accounting for in-plume chemistry is most relevant for
pristine marine areas. |
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