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| Titel |
Airborne observations of trace gases over boreal Canada during BORTAS: campaign climatology, air mass analysis and enhancement ratios |
| VerfasserIn |
S. J. O'Shea, G. Allen, M. W. Gallagher, S. J.-B. Bauguitte, S. M. Illingworth, M. Le Breton, J. B. A. Muller, C. J. Percival, A. T. Archibald, D. E. Oram, M. Parrington, P. I. Palmer, A. C. Lewis |
| 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 ; 13, no. 24 ; Nr. 13, no. 24 (2013-12-19), S.12451-12467 |
| Datensatznummer |
250085895
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| Publikation (Nr.) |
 copernicus.org/acp-13-12451-2013.pdf |
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| Zusammenfassung |
In situ airborne measurements were made over eastern Canada in summer 2011
as part of the BORTAS experiment (Quantifying the impact of BOReal forest
fires on Tropospheric oxidants over the Atlantic using Aircraft
and Satellites). In this paper we present observations of greenhouse gases
(CO2 and CH4) and other biomass burning tracers (CO, HCN and
CH3CN), both climatologically and through case studies, as recorded on
board the FAAM BAe-146 research aircraft.
Vertical profiles of CO2 were generally characterised by depleted
boundary layer concentrations relative to the free troposphere, consistent
with terrestrial biospheric uptake. In contrast, CH4 concentrations
were found to rise with decreasing altitude due to strong local and regional
surface sources. BORTAS observations were found to be broadly comparable
with both previous measurements in the region during the regional burning
season and with reanalysed composition fields from the EU Monitoring
Atmospheric Composition and Change (MACC) project. We use coincident
tracer–tracer correlations and a Lagrangian trajectory model to characterise
and differentiate air mass history of intercepted plumes. In particular, CO,
HCN and CH3CN were used to identify air masses that have been recently
influenced by biomass burning.
Examining individual cases we were able to quantify emissions from biomass
burning. Using both near-field (< 1 day) and far-field (> 1 day)
sampling, boreal forest fire plumes were identified throughout the
troposphere. Fresh plumes from fires in northwestern Ontario yield emission
factors for CH4 and CO2 of 8.5 ± 0.9 g (kg dry matter)−1
and 1512 ± 185 g (kg dry matter)−1, respectively. We have
also investigated the efficacy of calculating emission factors from
far-field sampling, in which there might be expected to be limited mixing
with background and other characteristic air masses, and we provide guidance
on best practice and limitations in such analysis. We have found that for
measurements within plumes that originated from fires in northwestern Ontario
2–4 days upwind, emission factors can be calculated that range between 1618 ± 216 and 1702 ± 173 g (kg dry matter)−1 for CO2 and
1.8 ± 0.2 and 6.1 ± 1 g (kg dry matter)−1 for CH4. |
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