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| Titel |
Improved model of isoprene emissions in Africa using Ozone Monitoring Instrument (OMI) satellite observations of formaldehyde: implications for oxidants and particulate matter |
| VerfasserIn |
E. A. Marais, D. J. Jacob, A. Guenther, K. Chance, T. P. Kurosu, J. G. Murphy, C. E. Reeves, H. O. T. Pye |
| 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. 15 ; Nr. 14, no. 15 (2014-08-01), S.7693-7703 |
| Datensatznummer |
250118916
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| Publikation (Nr.) |
 copernicus.org/acp-14-7693-2014.pdf |
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| Zusammenfassung |
| We use a 2005–2009 record of isoprene emissions over Africa derived from Ozone Monitoring Instrument
(OMI) satellite observations of formaldehyde (HCHO) to better understand the
factors controlling isoprene emission in the continent and evaluate the
impact on atmospheric composition. OMI-derived isoprene emissions show large
seasonality over savannas driven by temperature and leaf area index (LAI),
and much weaker seasonality over equatorial forests driven by temperature.
The commonly used MEGAN (Model of Emissions of Gases and Aerosols from Nature, version 2.1) global isoprene emission model
reproduces this seasonality but is biased high, particularly for equatorial
forests, when compared to OMI and relaxed-eddy accumulation measurements.
Isoprene emissions in MEGAN are computed as the product of an emission
factor Eo, LAI, and activity factors dependent on environmental
variables. We use the OMI-derived emissions to provide improved estimates of
Eo that are in good agreement with direct leaf measurements from field
campaigns (r = 0.55, bias = −19%). The largest downward corrections to
MEGAN Eo values are for equatorial forests and semi-arid environments,
and this is consistent with latitudinal transects of isoprene over western
Africa from the African Monsoon Multidisciplinary Analysis (AMMA) aircraft campaign. Total emission of isoprene in Africa
is estimated to be 77 Tg C a−1, compared to 104 Tg C a−1 in MEGAN.
Simulations with the GEOS-Chem oxidant–aerosol model suggest that isoprene
emissions increase mean surface ozone in western Africa by up to 8 ppbv, and
particulate matter by up to 1.5 μg m−3, due to coupling with
anthropogenic influences. |
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