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Title:
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Feasibility study of using a “travelling” CO2 and CH4 instrument to validate continuous in-situ measurement stations
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Author(s):
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Hammer, S.; Konrad, G.; Vermeulen, A.T.; Laurent, O.; Delmotte, M.; Jordan, A.; Hazan, L.; Conil, S.; Levin, I.
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Published by:
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Publication date:
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ECN
Environment & Energy Engineering
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24-9-2012
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ECN report number:
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Document type:
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ECN-W--12-040
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Article (scientific)
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Number of pages:
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23
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Published in: Atmospheric Measurement Techniques (Copernicus GmbH ), , 2012, Vol.5, p.7141-7185.
Abstract:
In the course of the ICOS (Integrated Carbon Observation System)Demo Experiment
a feasibility study on the usefulness of a Travelling Comparison Instrument (TCI) was
conducted in order to evaluate continuous atmospheric CO2 and CH4 measurements
5 at two European stations. The aim of the TCI is to independently measure ambient
air in parallel to the standard station instrumentation, thus providing a comprehensive
comparison that includes the sample intake system, the instrument itself as well as its
calibration and data evaluation. Observed differences between the TCI and the Heidelberg
gas chromatographic system, which acted as a reference for the TCI, were
10 -0.02±0.08 µmolmol-1 for CO2 and -0.3±2.3 nmolmol-1 for CH4. Over a period of
two weeks each, the continuous CO2 and CH4 measurements at two ICOS field stations,
Cabauw and OPE, were compared to co-located TCI measurements. At Cabauw
mean differences of 0.21±0.06 µmol mol-1 for CO2 and 0.41±0.50 nmol mol-1 for CH4
were found. For OPE the mean differences were 0.13±0.07 µmol mol-1 for CO2 and
15 0.44±0.36 nmolmol-1 for CH4. Potential causes of these observed differences are
leakages or contaminations in the intake lines and/or there flushing pumps. At Cabauw
station an additional error contribution originates from insufficient flushing of standard
gases. Offsets arising from differences in the working standard calibrations or leakages/
contaminations in the drying systems are too small to explain the observed dif20
ferences. Finally a comprehensive quality management strategy for atmospheric monitoring
networks is proposed.
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