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| Titel |
Improved ACE-FTS observations of carbon tetrachloride (CCl4) |
| VerfasserIn |
Jeremy Harrison, Martyn Chipperfield, Chris Boone, Peter Bernath |
| 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 |
250135373
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| Publikation (Nr.) |
 EGU/EGU2016-16228.pdf |
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| Zusammenfassung |
| The Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS), on
board the SCISAT satellite, has been recording solar occultation spectra through the Earth’s
atmosphere since 2004 and continues to take measurements with only minor loss in
performance. ACE-FTS time series are available for a range of chlorine ‘source’ gases,
including CCl3F (CFC-11), CCl2F2 (CFC-12), CHF2Cl (HCFC-22), CH3Cl and
CCl4.
Recently there has been much community interest in carbon tetrachloride (CCl4),
a substance regulated by the Montreal Protocol because it leads to the catalytic
destruction of stratospheric ozone. Estimated sources and sinks of CCl4 remain
inconsistent with observations of its abundance. Satellite observations of CCl4 in
the stratosphere are particularly useful in validating stratospheric loss (photolysis)
rates; in fact the atmospheric loss of CCl4 is essentially all due to photolysis in the
stratosphere. However, the latest ACE-FTS v3.5 CCl4 retrieval is biased high by ∼
20–30%.
A new ACE-FTS retrieval scheme utilising new laboratory spectroscopic measurements
of CCl4 and improved microwindow selection has recently been developed. This
improves upon the v3.5 retrieval and resolves the issue of the high bias; this new
scheme will form the basis for the upcoming v4 processing version of ACE-FTS
data. This presentation will outline the improvements made in the retrieval, and a
subset of data will be compared with modelled CCl4 distributions from SLIMCAT, a
state-of-the-art three-dimensional chemical transport model. The use of ACE-FTS data to
evaluate the modelled stratospheric loss rate of CCl4 will also be discussed. The
evaluated model, which also includes a treatment of surface soil and ocean sinks,
will then be used to quantify current uncertainties in the global budget of CCl4. |
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