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| Titel |
Ground-based FTIR and MAX-DOAS observations of formaldehyde at Réunion Island and comparisons with satellite and model data |
| VerfasserIn |
C. Vigouroux, F. Hendrick, T. Stavrakou, B. Dils, I. Smedt, C. Hermans, A. Merlaud, F. Scolas, C. Senten, G. Vanhaelewyn, S. Fally, M. Carleer, J.-M. Metzger, J.-F. Müller, M. Roozendael, M. Mazière |
| 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 ; 9, no. 24 ; Nr. 9, no. 24 (2009-12-17), S.9523-9544 |
| Datensatznummer |
250007805
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| Publikation (Nr.) |
 copernicus.org/acp-9-9523-2009.pdf |
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| Zusammenfassung |
Formaldehyde (HCHO) columns have been retrieved from ground-based
Fourier transform infrared (FTIR) campaign measurements in 2004 and
2007 and from UV-Visible MAX-DOAS measurements in 2004–2005 at the
NDACC site of Réunion Island (21° S, 55° E). The
FTIR and MAX-DOAS daily mean formaldehyde total columns are
intercompared in their common measurement period, from August to
October 2004. The ground-based data are also compared to correlative
SCIAMACHY data. The comparisons account for the vertical sensitivity
differences of the data sets, by including their respective averaging
kernels. Complete error budgets are also presented.
The FTIR and MAX-DOAS daily mean total columns agree very well: no
significant bias is observed and the standard deviation of the
comparisons is only 8%. Both FTIR and MAX-DOAS HCHO total
columns are in good agreement with SCIAMACHY values in the 2004–2005
period, with standard deviations of 21% and 31%, respectively. The
same seasonal cycle is observed by the different instruments, with
a minimum in austral winter and a maximum in February–March.
The FTIR and MAX-DOAS data are confronted with HCHO columns calculated
by a global CTM, the IMAGES model. The model underestimates the HCHO
columns by 23–29% in comparison with FTIR, and by 15% in
comparison with DOAS. This bias might have multiple causes, including
an underestimation of OH concentrations in the model (as indicated by
a sensitivity study using prescribed OH fields) and/or an
underestimated contribution of large-scale transport of HCHO
precursors from Madagascar. The latter hypothesis is comforted by the
large observed day-to-day variability of HCHO columns, and by the
observation that the peak values of FTIR columns can often be
associated with free tropospheric transport patterns from source
regions over Madagascar to Réunion Island, according to simulations
performed with the Lagrangian particle dispersion model FLEXPART. |
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