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| Titel |
Inferring isoprene emissions from Africa using OMI observations of formaldehyde columns |
| VerfasserIn |
E. Marais, D. J. Jacob, D. Millet, J. Murphy, C. Reeves, M. Barkley, S. Casadio, T. Kurosu, K. Chance, G. Mills, J. Mao, F. Paulot |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063739
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| Zusammenfassung |
| We use 2005-2009 observations of formaldehyde (HCHO) columns from OMI to infer
biogenic isoprene emissions at monthly 1Ë Ã1Ë Â 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), as well as
anthropogenic influences using AATSR satellite data for small-flame fires (gas flaring). The
resulting biogenic HCHO columns (ΩHCHO) follow closely the distribution of
vegetation patterns in Africa. We infer isoprene emission (EISOP)Â 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 and
fit it to a linear function of tropospheric column NO2Â from OMI. We estimate a
40% error in our inferred isoprene emissions for the high-NOx regime (16% of
area in Africa retained after filtering), and 40-90% for the low-NOx regime with
the error increasing with decreasing NOx. Most of the error is due to smearing.
Comparison to the state-of-science MEGAN inventory indicates large overestimates in that
inventory for the central African rainforest and adjacent deciduous broadleaf trees. |
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