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| Titel |
Isoprene emissions in Africa inferred from OMI observations of formaldehyde columns |
| VerfasserIn |
E. A. Marais, D. J. Jacob, T. P. Kurosu, K. Chance, J. G. Murphy, C. Reeves, G. Mills, S. Casadio, D. B. Millet, M. P. Barkley, F. Paulot, J. Mao |
| 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 ; 12, no. 14 ; Nr. 12, no. 14 (2012-07-18), S.6219-6235 |
| Datensatznummer |
250011324
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| Publikation (Nr.) |
 copernicus.org/acp-12-6219-2012.pdf |
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| Zusammenfassung |
| We use 2005–2009 satellite observations of formaldehyde (HCHO) columns from
the OMI instrument to infer biogenic isoprene emissions at monthly
1 × 1° resolution over the African continent. Our work
includes new approaches to remove biomass burning influences using OMI
absorbing aerosol optical depth data (to account for transport of fire
plumes) and anthropogenic influences using AATSR satellite data for
persistent small-flame fires (gas flaring). The resulting biogenic HCHO
columns (ΩHCHO) from OMI follow closely the distribution of
vegetation patterns in Africa. We infer isoprene emission (EISOP)
from the local sensitivity S = ΔΩHCHO / ΔEISOP derived with the GEOS-Chem chemical transport model using two
alternate isoprene oxidation mechanisms, and verify the validity of this
approach using AMMA aircraft observations over West Africa and a longitudinal
transect across central Africa. Displacement error (smearing) is diagnosed by
anomalously high values of S and the corresponding data are removed. We
find significant sensitivity of S to NOx under low-NOx
conditions that we fit to a linear function of tropospheric column NO2.
We estimate a 40% error in our inferred isoprene emissions under
high-NOx conditions and 40–90% under low-NOx
conditions. Our results suggest that isoprene emission from the central
African rainforest is much lower than estimated by the state-of-the-science
MEGAN inventory. |
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