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Feasibility study of using a “travelling” CO2 and CH4 instrument to validate continuous in-situ measurement stations
Hammer, S.; Konrad, G.; Vermeulen, A.T.; Laurent, O.; Delmotte, M.; Jordan, A.; Hazan, L.; Conil, S.; Levin, I.
Published by: Publication date:
ECN Environment & Energy Engineering 24-9-2012
ECN report number: Document type:
ECN-W--12-040 Article (scientific)
Number of pages:

Published in: Atmospheric Measurement Techniques (Copernicus GmbH ), , 2012, Vol.5, p.7141-7185.

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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