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| Titel |
Validation of SCIAMACHY HDO/H2O measurements using the TCCON and NDACC-MUSICA networks |
| VerfasserIn |
R. A. Scheepmaker, C. Frankenberg, N. M. Deutscher, M. Schneider, S. Barthlott, T. Blumenstock, O. E. García, F. Hase, N. Jones, E. Mahieu, J. Notholt, V. Velazco, J. Landgraf, I. Aben |
| 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 ; 8, no. 4 ; Nr. 8, no. 4 (2015-04-21), S.1799-1818 |
| Datensatznummer |
250116301
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| Publikation (Nr.) |
 copernicus.org/amt-8-1799-2015.pdf |
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| Zusammenfassung |
| Measurements of the atmospheric HDO/H2O ratio help us to better understand
the hydrological cycle and improve models to correctly simulate tropospheric
humidity and therefore climate change. We present an updated version of the
column-averaged HDO/H2O ratio data set from the SCanning
Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY).
The data set is extended with 2 additional years, now covering 2003–2007, and
is validated against co-located ground-based total column δD
measurements from Fourier transform spectrometers (FTS) of the Total Carbon
Column Observing Network (TCCON) and the Network for the Detection of
Atmospheric Composition Change (NDACC, produced within the framework of
the MUSICA project). Even though the time overlap
among the available data is not yet ideal, we determined a mean negative bias
in SCIAMACHY δD of −35 ± 30‰ compared to TCCON and
−69 ± 15‰ compared to MUSICA (the uncertainty indicating
the station-to-station standard deviation). The bias shows a latitudinal
dependency, being largest (∼ −60 to −80‰) at the highest latitudes
and smallest (∼ −20 to −30‰) at the lowest latitudes. We have tested
the impact of an offset correction to the SCIAMACHY HDO and H2O columns.
This correction leads to a humidity- and latitude-dependent shift in δD
and an improvement of the bias by 27‰, although it does not lead to an
improved correlation with the FTS measurements nor to a strong reduction of the
latitudinal dependency of the bias. The correction might be an improvement for
dry, high-altitude areas, such as the Tibetan Plateau and the Andes region.
For these areas, however, validation is currently impossible due to a lack of
ground stations. The mean standard deviation of single-sounding
SCIAMACHY–FTS differences is ∼ 115‰, which is reduced by a factor
∼ 2 when we consider monthly means. When we relax the strict matching of
individual measurements and focus on the mean seasonalities using all available
FTS data, we find that the correlation coefficients between SCIAMACHY and the
FTS networks improve from 0.2 to 0.7–0.8. Certain ground stations show a clear
asymmetry in δD during the transition from the dry to the wet season
and back, which is also detected by SCIAMACHY. This asymmetry points to a
transition in the source region temperature or location of the water vapour and
shows the added information that HDO/H2O measurements provide when used in
combination with variations in humidity. |
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