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| Titel |
A multi-year methane inversion using SCIAMACHY, accounting for systematic errors using TCCON measurements |
| VerfasserIn |
S. Houweling, M. Krol, P. Bergamaschi, C. Frankenberg, E. J. Dlugokencky, I. Morino, J. Notholt, V. Sherlock, D. Wunch, V. Beck, C. Gerbig, H. Chen, E. A. Kort, T. Röckmann, I. Aben |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 8 ; Nr. 14, no. 8 (2014-04-22), S.3991-4012 |
| Datensatznummer |
250118630
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| Publikation (Nr.) |
 copernicus.org/acp-14-3991-2014.pdf |
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| Zusammenfassung |
| This study investigates the use of total column CH4 (XCH4) retrievals
from the SCIAMACHY satellite instrument for quantifying large-scale emissions
of methane. A unique data set from SCIAMACHY is available spanning almost a
decade of measurements, covering a period when the global CH4 growth rate
showed a marked transition from stable to increasing mixing ratios. The TM5
4DVAR inverse modelling system has been used to infer CH4 emissions from a
combination of satellite and surface measurements for the period 2003–2010.
In contrast to earlier inverse modelling studies, the SCIAMACHY retrievals
have been corrected for systematic errors using the TCCON network of ground-based Fourier transform spectrometers. The aim is to further investigate the
role of bias correction of satellite data in inversions. Methods for bias
correction are discussed, and the sensitivity of the optimized emissions to
alternative bias correction functions is quantified. It is found that the use
of SCIAMACHY retrievals in TM5 4DVAR increases the estimated inter-annual
variability of large-scale fluxes by 22% compared with the use of only
surface observations. The difference in global methane emissions between 2-year periods before and after July 2006 is estimated at 27–35 Tg yr−1. The use
of SCIAMACHY retrievals causes a shift in the emissions from the
extra-tropics to the tropics of 50 ± 25 Tg yr−1. The large uncertainty in
this value arises from the uncertainty in the bias correction functions.
Using measurements from the HIPPO and BARCA aircraft campaigns, we show that
systematic errors in the SCIAMACHY measurements are a main factor limiting
the performance of the inversions. To further constrain tropical emissions of
methane using current and future satellite missions, extended validation
capabilities in the tropics are of critical importance. |
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