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| Titel |
SCIAMACHY WFM-DOAS XCO2: reduction of scattering related errors |
| VerfasserIn |
J. Heymann, H. Bovensmann, M. Buchwitz, J. P. Burrows, N. M. Deutscher, J. Notholt, M. Rettinger, M. Reuter, O. Schneising, R. Sussmann, T. Warneke |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 5, no. 10 ; Nr. 5, no. 10 (2012-10-09), S.2375-2390 |
| Datensatznummer |
250003120
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| Publikation (Nr.) |
 copernicus.org/amt-5-2375-2012.pdf |
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| Zusammenfassung |
Global observations of column-averaged dry air mole fractions
of carbon dioxide (CO2), denoted by XCO2 ,
retrieved from SCIAMACHY on-board ENVISAT can
provide important and missing global information on the
distribution and magnitude of regional CO2 surface fluxes.
This application has challenging precision and
accuracy requirements.
In a previous publication (Heymann et al., 2012),
it has been shown by analysing seven years of SCIAMACHY
WFM-DOAS XCO2 (WFMDv2.1) that unaccounted thin cirrus
clouds can result in significant errors.
In order to enhance the quality of the SCIAMACHY XCO2
data product, we have developed a new version of the retrieval
algorithm (WFMDv2.2), which is described in this
manuscript. It is based on an improved cloud filtering and
correction method using the 1.4 μm strong water
vapour absorption and 0.76 μm
O2-A bands. The new algorithm has been used to
generate a SCIAMACHY XCO2 data set covering the years
2003–2009.
The new XCO2 data set has been validated using
ground-based observations from the Total Carbon Column
Observing Network (TCCON). The validation shows a significant
improvement of the new product (v2.2) in comparison to the
previous product (v2.1). For example, the standard deviation
of the difference to TCCON at Darwin, Australia, has been
reduced from 4 ppm to 2 ppm. The monthly
regional-scale scatter of the data (defined as the mean
intra-monthly standard deviation of all quality filtered
XCO2 retrievals within a radius of 350 km
around various locations) has also been reduced, typically by
a factor of about 1.5. Overall, the validation of the new
WFMDv2.2 XCO2 data product can be summarised by
a single measurement precision of 3.8 ppm, an
estimated regional-scale (radius of 500 km) precision
of monthly averages of 1.6 ppm and an estimated
regional-scale relative accuracy of 0.8 ppm.
In addition to the comparison with the limited number of TCCON
sites, we also present a comparison with NOAA's global
CO2 modelling and assimilation system
CarbonTracker. This comparison also shows significant
improvements especially over the Southern Hemisphere. |
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