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| Titel |
The French-German Climate Monitoring Initiative on global observations of atmospheric CH4 |
| VerfasserIn |
Gerhard Ehret, Pierre Flamant, Axel Amediek, Philippe Ciais, Fabien Gibert, Andreas Fix, Christoph Kiemle, Mathieu Quatrevalet, Martin Wirth |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042613
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| Zusammenfassung |
| We report on a new French-German Climate Monitoring Initiative targeting on global
measurements of atmospheric methane (CH4). Among the greenhouse gases banned by the
Kyoto protocol, CH4 contributes most to global warming after CO2. Questions arise whether
global warming in Arctic regions might foster the melting of permafrost soils which contain
significant amounts of carbon in organic form which under anaerobic conditions might be
converted to CH4 and partially released to the atmosphere. Also the development of natural
wetlands which are the biggest methane source, play an important role in climate
prediction. Up to now, there is very little knowledge about CH4 sources and sinks in
connection with changes in the agro-industrial era of predominant human influence or the
very large deposits of CH4 as gas hydrates on ocean shelves that are vulnerable to
ocean warming. The objective of this initiative is to improve our knowledge on
regional to synoptic scale methane sources, globally. This will be obtained by the
measurement of the column-weighted dry-air mixing ratio of CH4, commonly referred to
XCH4 which can be used as input for flux inversion models. As a novel feature, the
observational instrument will have its own light source emitting pulsed narrow-line laser
radiation, not relying on sunlight. The XCH4 values will be provided by a lidar
technique with no bias due to particles scattering in the light path, which can have
strong regional variability. Using a range-gated receiver for detection of the signals
scattered from the Earth surface, the lidar can distinguish surface from cloud or aerosol
backscatter, permitting high-precision retrievals of XCH4 in the presence of thin
cirrus or aerosol layers. The proposed measurement approach is also capable of
providing measurements in partially cloudy conditions. The emitted laser pulses can
reach the surface when gaps between clouds occur due to the near-nadir view and
the small lidar footprint. The instrument will also provide XCH4 measurements
above dense stratiform clouds to be used as reflective target instead of the surface.
Using this observational method an unique dataset with sampling twice daily and
with all-season and all-latitude coverage will be provided. In our presentation we
focus on the measurement concept of XCH4 using an active optical instrument
and discuss the expected performance in connection to the needs of flux inversion
experiments. Finally, we will give an overview on supporting activities related to lidar
measurements of greenhouse gas concentrations from ground-based and airborne platforms. |
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