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| Titel |
Comparison of continuous in situ CO2 observations at Jungfraujoch using two different measurement techniques |
| VerfasserIn |
M. F. Schibig, M. Steinbacher, B. Buchmann, I. T. van der Laan-Luijkx, S. van der Laan, S. Ranjan, M. C. Leuenberger |
| 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. 1 ; Nr. 8, no. 1 (2015-01-06), S.57-68 |
| Datensatznummer |
250116038
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| Publikation (Nr.) |
 copernicus.org/amt-8-57-2015.pdf |
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| Zusammenfassung |
Since 2004, atmospheric carbon dioxide (CO2) is being measured at the High
Altitude Research Station Jungfraujoch by the division of Climate and
Environmental Physics at the University of Bern (KUP) using a nondispersive
infrared gas analyzer (NDIR) in combination with a paramagnetic O2
analyzer. In January 2010, CO2 measurements based on cavity ring-down
spectroscopy (CRDS) as part of the Swiss National Air Pollution Monitoring
Network were added by the Swiss Federal Laboratories for Materials
Science and Technology (Empa). To ensure a smooth transition – a
prerequisite when merging two data sets, e.g., for trend determinations – the
two measurement systems run in parallel for several years. Such a long-term
intercomparison also allows the identification of potential offsets between the two
data sets and the collection of information about the compatibility of the two systems
on different time scales.
A good agreement of the seasonality, short-term variations and, to a lesser extent mainly due to the
short common period, trend calculations is observed. However, the comparison reveals some issues related to
the stability of the calibration gases of the KUP system and their assigned
CO2 mole fraction. It is possible to adapt an improved calibration
strategy based on standard gas determinations, which leads to better
agreement between the two data sets. By excluding periods with technical
problems and bad calibration gas cylinders, the average hourly difference
(CRDS – NDIR) of the two systems is −0.03 ppm ± 0.25 ppm. Although
the difference of the two data sets is in line with the compatibility goal of
±0.1 ppm of the World Meteorological Organization (WMO), the standard
deviation is still too high. A significant part of this uncertainty
originates from the necessity to switch the KUP system frequently (every 12 min) for 6 min from ambient air to a working gas in order to correct
short-term variations of the O2 measurement system. Allowing additional
time for signal stabilization after switching the sample, an effective data
coverage of only one-sixth for the KUP system is achieved while the Empa system
has a nearly complete data coverage. Additionally, different internal
volumes and flow rates may affect observed differences. |
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