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| Titel |
Estimating sources of elemental and organic carbon and their temporal emission patterns using a least squares inverse model and hourly measurements from the St. Louis–Midwest supersite |
| VerfasserIn |
B. Foy, Y. Y. Cui, J. J. Schauer, M. Janssen, J. R. Turner, C. Wiedinmyer |
| 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 ; 15, no. 5 ; Nr. 15, no. 5 (2015-03-05), S.2405-2427 |
| Datensatznummer |
250119490
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| Publikation (Nr.) |
 copernicus.org/acp-15-2405-2015.pdf |
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| Zusammenfassung |
| Emission inventories of elemental carbon (EC) and organic carbon (OC)
contain large uncertainties both in their spatial and temporal
distributions for different source types. An inverse model was used to evaluate EC and OC emissions based on 1 year of
hourly measurements from the St. Louis–Midwest supersite. The
input to the model consisted of continuous measurements of EC and OC
obtained for 2002 using two semicontinuous analyzers. High
resolution meteorological simulations were performed for the entire
time period using the Weather Research and Forecasting Model (WRF). These were used to simulate hourly back trajectories at the
measurement site using a Lagrangian model (FLEXPART-WRF). In
combination, an Eulerian model (CAMx: The Comprehensive Air Quality Model with Extensions ) was used to simulate the
impacts at the measurement site using known emissions inventories
for point and area sources from the Lake Michigan Directors Consortium (LADCO)
as well as for open burning from the Fire Inventory from NCAR (FINN). By considering only passive transport of pollutants, the Bayesian inversion
simplifies to a single least squares inversion. The inverse model
combines forward Eulerian simulations with backward Lagrangian
simulations to yield estimates of emissions from sources in current
inventories as well as from emissions that might be missing in
the inventories. The CAMx impacts were disaggregated into separate
time chunks in order to determine improved diurnal, weekday and
monthly temporal patterns of emissions. Because EC is a primary
species, the inverse model estimates can be interpreted directly as
emissions. In contrast, OC is both a primary and a secondary
species. As the inverse model does not differentiate between direct
emissions and formation in the plume of those direct emissions, the
estimates need to be interpreted as contributions to measured
concentrations. Emissions of EC and OC in the St. Louis region from on-road,
non-road, marine/aircraft/railroad (MAR), "other" and point
sources were revised slightly downwards on average. In particular,
both MAR and point sources had a more pronounced diurnal variation
than in the inventory. The winter peak in "other" emissions was not
corroborated by the inverse model. On-road emissions have a larger
difference between weekday and weekends in the inverse estimates
than in the inventory, and appear to be poorly simulated or
characterized in the winter months. The model suggests that open
burning emissions are significantly underestimated in the inventory. Finally, contributions of unknown sources seems to be from areas to
the south of St. Louis and from afternoon and nighttime emissions. |
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