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| Titel |
Origins and seasonality of greenhouse gases over the South Atlantic Ocean |
| VerfasserIn |
Sabrina G. Arnold, Dietrich G. Feist, Zhiting Wang |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133560
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| Publikation (Nr.) |
 EGU/EGU2016-14184.pdf |
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| Zusammenfassung |
| The Total Carbon Column Observing Network (TCCON) has become the reference network
for all total-column observations of greenhouse gases (GHGs) like CO2, CH4, CO, N2O and
others. Within TCCON, the Max Planck Institute for Biogeochemistry (MPI-BGC) has been
operating a Fourier-Transform Spectrometer (FTS) on Ascension Island (8∘S, 14∘W)
since May 2012. This is currently the only TCCON station covering the South
Atlantic Ocean. So far, the measurements span more than two complete seasonal
cycles.
Due to its location in the southern trade wind zone, the station is downwind from Africa most
of the time. A detailed trajectory analysis shows that different parts of the total atmospheric
column typically have different origins. Air in the Planetary Boundary Layer (PBL)
typically comes from the deep southern Atlantic Ocean and had only little GHG
exchange with land surfaces. However, air in the free troposphere above the PBL
usually comes from tropical and southern Africa and sometimes also from South
America.
A detailed analysis allowed us to separate the total column of CH4 into a tropospheric and
stratospheric part. Together with independent flask measurements from the surface,
the effects of the different origins of air parcels can be seen in the PBL, the free
troposphere and the stratosphere. For example, there are striking differences in
seasonality for CH4 between the PBL and the free troposphere. Unlike over typical
land stations, trace gas concentrations in the free troposphere above Ascension
Island seem to be generally much higher than near the surface. Above the PBL,
there is a whole layer of GHGs transported from Africa which shows land seasonal
effects and biomass burning signals. This layer remains undetectable for surface
observations. |
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