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| Titel |
Comparisons of continuous atmospheric CH4, CO2 and N2O measurements – results from a travelling instrument campaign at Mace Head |
| VerfasserIn |
S. N. Vardag, S. Hammer, S. O'Doherty, T. G. Spain, B. Wastine, A. Jordan, I. Levin |
| 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. 16 ; Nr. 14, no. 16 (2014-08-21), S.8403-8418 |
| Datensatznummer |
250118962
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| Publikation (Nr.) |
 copernicus.org/acp-14-8403-2014.pdf |
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| Zusammenfassung |
| A 2-month measurement campaign with a Fourier transform infrared analyser as
a travelling comparison instrument (TCI) was performed at the Advanced Global
Atmospheric Gases Experiment (AGAGE) and World Meteorological Organization
(WMO) Global Atmosphere Watch (GAW) station at Mace Head, Ireland. The aim
was to evaluate the compatibility of atmospheric methane (CH4), carbon
dioxide (CO2) and nitrous oxide (N2O) measurements of the routine
station instrumentation, consisting of a gas chromatograph (GC) for CH4
and N2O as well as a cavity ring-down spectroscopy (CRDS) system for
CH4 and CO2. The advantage of a TCI approach for quality control is
that the comparison covers the entire ambient air measurement system,
including the sample intake system and the data evaluation process. For
initial quality and performance control, the TCI was run in parallel with the
Heidelberg GC before and after the measurement campaign at Mace Head. Median
differences between the Heidelberg GC and the TCI were well within the WMO
inter-laboratory compatibility target for all three greenhouse gases. At Mace
Head, the median difference between the station GC and the TCI were
−0.04 nmol mol−1 for CH4 and −0.37 nmol mol−1 for
N2O (GC-TCI). For N2O, a similar difference
(−0.40 nmol mol−1) was found when measuring surveillance or working
gas cylinders with both instruments. This suggests that the difference
observed in ambient air originates from a calibration offset that could
partly be due to a difference between the WMO N2O X2006a reference scale
used for the TCI and the Scripps Institution of Oceanography (SIO-1998) scale
used at Mace Head and in the whole AGAGE network. Median differences between
the CRDS G1301 and the TCI at Mace Head were 0.12 nmol mol−1 for
CH4 and 0.14 μmol mol−1 for CO2 (CRDS G1301 –
TCI). The difference between both instruments for CO2 could not be
explained, as direct measurements of calibration gases show no such
difference. The CH4 differences between the TCI, the GC and the CRDS
G1301 at Mace Head are much smaller than the WMO inter-laboratory
compatibility target, while this is not the case for CO2 and N2O. |
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