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| Titel |
Optimized approach to retrieve information on the tropospheric and stratospheric carbonyl sulfide (OCS) vertical distributions above Jungfraujoch from high-resolution FTIR solar spectra. |
| VerfasserIn |
Bernard Lejeune, Emmanuel Mahieu, Christian Servais, Pierre Duchatelet, Philippe Demoulin |
| 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 |
250034552
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| Zusammenfassung |
| Carbonyl sulfide (OCS), which is produced in the troposphere from both biogenic and
anthropogenic sources, is the most abundant gaseous sulfur species in the unpolluted
atmosphere. Due to its low chemical reactivity and water solubility, a significant fraction of
OCS is able to reach the stratosphere where it is converted to SO2 and ultimately to H2SO4
aerosols (Junge layer). These aerosols have the potential to amplify stratospheric
ozone destruction on a global scale and may influence Earth’s radiation budget and
climate through increasing solar scattering. The transport of OCS from troposphere to
stratosphere is thought to be the primary mechanism by which the Junge layer is sustained
during nonvolcanic periods. Because of this, long-term trends in atmospheric OCS
concentration, not only in the troposphere but also in the stratosphere, are of great
interest.
A new approach has been developed and optimized to retrieve atmospheric abundance of
OCS from high-resolution ground-based infrared solar spectra by using the SFIT-2 (v3.91)
algorithm, including a new model for solar lines simulation (solar lines often produce
significant interferences in the OCS microwindows). The strongest lines of the ν3
fundamental band of OCS at 2062 cm-1 have been systematically evaluated with objective
criteria to select a new set of microwindows, assuming the HITRAN 2004 spectroscopic
parameters with an increase in the OCS line intensities of the ν3band main isotopologue
16O12C32S by 15.79% as compared to HITRAN 2000 (Rothman et al., 2008, and references
therein). Two regularization schemes have further been compared (deducted from
ATMOS and ACE-FTS measurements or based on a Tikhonov approach), in order to
select the one which optimizes the information content while minimizing the error
budget.
The selected approach has allowed us to determine updated OCS long-term trend from
1988 to 2009 in both the troposphere and the stratosphere, using spectra recorded on a regular
basis with Fourier Transform Infrared spectrometers (FTIRs), under clear-sky conditions, at
the NDACC site (Network for the Detection of Atmospheric Composition Change, visit
http://www.ndacc.org) of the International Scientific Station of the Jungfraujoch (Swiss Alps,
46.5Ë N, 8.0Ë E, 3580m asl). Trends and seasonal cycles deduced from our results
will be compared to values published in the literature and critically discussed. In
particular, we will confirm the recent change in the OCS total column trend, which
has become positive since 2002 before undergoing a slowing down over the last
years.
References
Brasseur, G.P., J.J. Orlando and G.S. Tyndall (Eds.), Atmospheric Chemistry and Global
Change, 654 pp., Oxford University Press, New York, 1999.
Mahieu E., R. Zander, P. Demoulin, P. Duchatelet, C. Servais, C.P. Rinsland and M. De
Mazière, Recent evolution of atmospheric OCS above the Jungfraujoch station : implications
for the stratospheric aerosol layer. In: Proceedings of atmospheric spectroscopic applications,
ASA Reims 2005, September 6-8, 2005.
Rinsland, C.P., L. Chiou, E. Mahieu, R. Zander, C.D. Boone, and P.F. Bernath,
Measurements of long-term changes in atmospheric OCS (carbonyl sulfide) from infrared
solar observations, Journal of Quantitative Spectroscopy & Radiative Transfer, 109,
2679-2686, 2008.
Rothman, L.S., I.E. Gordon, A. Barbe and al., The HITRAN 2008 molecular
spectroscopic database, Journal of Quantitative Spectroscopy & Radiative Transfer, 110,
533-572, 2008.
SPARC Assessment of Stratospheric Aerosol Properties, L. Thomason and
Th. Peter (Eds.), WCRP 124, WMO/TD- No. 1295, SPARC Report No. 4, 2006. |
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