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| Titel |
Aircraft-based methane flux estimates for an agriculturally dominated valley in Switzerland |
| VerfasserIn |
Rebecca Hiller, Bruno Neininger, Dominik Brunner, Nina Buchmann, Werner Eugster |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250051845
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| Zusammenfassung |
| Today’s greenhouse gas inventories are typically based on bottom-up estimates, but
comparisons to atmospheric measurements are scarce and can disagree by factors of two or
more (Nisbet and Weiss, 2010). Therefore, top-down assessments to verify the
commonly used emission factors are needed. In Switzerland, 83% of the anthropogenic
methane emissions are attributed to the agricultural sector (FOEN, 2010). To validate
emission inventory estimates from this most relevant source in Switzerland, we
performed aircraft measurements along part of the Reuss Valley, a pre-alpine valley
dominated by agriculture. Flight legs were chosen to be along mostly constant
heights between 50–400 m above ground surface. These transects show distinct
patterns in CH4 concentrations depending on local changes in CH4 source strengths in
combination with dynamic changes of atmospheric conditions. During periods with a
steady valley wind system, a methane concentration gradient was observed along the
valley axis with increasing concentrations along the direction of the prevailing wind.
During these conditions, it was possible to use a simple box model approach to
calculate regional-scale fluxes. The ratios between the trace gases CH4, CO2, CO,
NOx as well as aerosols measured by the aircraft provide additional insight into
emission and atmospheric mixing processes and allowed us to distinguish between
different sources of methane, e.g. agriculture vs. combustion. In order to obtain a
better understanding of the spatial distribution of flux source areas, footprints for
individual points along the flight track were calculated by the Lagrangian Dispersion
Model COSMO-FLEXPART. A new CH4 cadastre of Switzerland produced for this
project allows us to compare our aircraft-based regional scale flux estimates with
the default emission factors used for the Swiss national inventory report (FOEN,
2010).
References:
FOEN (2010) Switzerland’s Greenhouse Gas Inventory 1990–2008. National Inventory
Report 2010 including reporting elements under the Kyoto Protocol. Submission of 15 April
2010 under the United Nations Framework Convention on Climate Change and under the Kyoto
Protocol. http://www.bafu.admin.ch/climatereporting/00545/10195/index.html?lang=en
Nisbet E, Weiss R (2010) Top-Down Versus Bottom-Up. Science, 328, 1241-1243. |
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