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| Titel |
Origin, variability and age of biomass burning plumes intercepted during BORTAS-B |
| VerfasserIn |
D. P. Finch, P. I. Palmer, M. Parrington |
| 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 ; 14, no. 24 ; Nr. 14, no. 24 (2014-12-23), S.13789-13800 |
| Datensatznummer |
250119266
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| Publikation (Nr.) |
 copernicus.org/acp-14-13789-2014.pdf |
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| Zusammenfassung |
| We use the GEOS-Chem atmospheric chemistry transport model to interpret
aircraft measurements of carbon monoxide (CO) in biomass burning outflow
taken during the 2011 BORTAS-B campaign over eastern Canada. The model has
some skill reproducing the observed variability, with a Spearman's rank
correlation rs = 0.65, but has a positive negative bias
for observations <100 ppb and a negative bias for observations
> 300 ppb. We find that observed CO variations are largely due to fires
over Ontario, as expected, with smaller and less variable contributions from
fossil fuel combustion from eastern Asia and NE North America. To help
interpret observed variations of CO we develop a Eulerian effective physical
age of emissions (A) metric, accounting for mixing and chemical
decay, which we apply to pyrogenic emissions of CO. We find that during
BORTAS-B the age of emissions intercepted over Halifax, Nova Scotia is
typically 4–11 days, and on occasion as young as two days. We show that
A is typically 1–5 days older than the associated photochemical ages
inferred from co-located measurements of different hydrocarbons. We find that
the frequency distribution of differences between the age measures
(Δτ) in plumes (defined by CH3CN > 150 ppt) peaks at
3 days. This corresponds to a chemical retardation of 50%. We find a
strong relationship in biomass burning plumes between A and
Δτ (r2 = 0.80), which is not present outwith these plumes
(r2 = 0.28). We argue that these observed relationships, together with
a robust observed relationship between CO and black carbon aerosol during
BORTAS-B (r2 > 0.7), form the basis of indirect evidence that aerosols
co-emitted with gases during pyrolysis markedly slowed down the plume
photochemistry during BORTAS-B with respect to photochemistry at the same
latitude and altitude in clear skies. |
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