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| Titel |
Biogenic nitrogen oxide emissions from soils: impact on NOx and ozone over west Africa during AMMA (African Monsoon Multidisciplinary Analysis): observational study |
| VerfasserIn |
D. J. Stewart, C. M. Taylor, C. E. Reeves, J. B. McQuaid |
| 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 ; 8, no. 8 ; Nr. 8, no. 8 (2008-04-29), S.2285-2297 |
| Datensatznummer |
250006066
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| Publikation (Nr.) |
 copernicus.org/acp-8-2285-2008.pdf |
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| Zusammenfassung |
Chemical and meteorological parameters measured on board the Facility for
Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research
Aircraft during the African Monsoon Multidisciplinary Analysis (AMMA)
campaign are presented to show the impact of NOx emissions from recently
wetted soils in West Africa. NO emissions from soils have been previously
observed in many geographical areas with different types of soil/vegetation cover during small scale studies and have been inferred at large
scales from satellite measurements of NOx. This study is the first dedicated
to showing the emissions of NOx at an intermediate scale between local
surface sites and continental satellite measurements. The measurements
reveal pronounced mesoscale variations in NOx concentrations closely
linked to spatial patterns of antecedent rainfall. Fluxes required to
maintain the NOx concentrations observed by the BAe-146 in a number of cases
studies and for a range of assumed OH concentrations (1×106 to
1×107 molecules cm−3) are calculated to be in the range 8.4 to
36.1 ng N m−2 s−1. These values are comparable to the range of
fluxes from 0.5 to 28 ng N m−2 s−1 reported from small scale field
studies in a variety of non-nutrient rich tropical and sub-tropical
locations reported in the review of Davidson and Kingerlee (1997). The
fluxes calculated in the present study have been scaled up to cover the area
of the Sahel bounded by 10 to 20 N and 10 E to 20 W giving an estimated
emission of 0.03 to 0.30 Tg N from this area for July and August 2006. The
observed chemical data also suggest that the NOx emitted from soils is
taking part in ozone formation as ozone concentrations exhibit similar fine
scale structure to the NOx, with enhancements over the wet soils. Such
variability can not be explained on the basis of transport from other areas.
Delon et al. (2008) is a companion paper to this one which models the impact
of soil NOx emissions on the NOx and ozone concentration over West
Africa during AMMA. It employs an artificial neural network to define the
emissions of NOx from soils, integrated into a coupled
chemistry-dynamics model. The results are compared to the observed data
presented in this paper. Here we compare fluxes deduced from the observed
data with the model-derived values from Delon et al. (2008). |
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