Atmospheric CO₂, δ(O₂/N₂) and δ¹³CO₂ measurements at Jungfraujoch, Switzerland: results from a flask sampling intercomparison program

Abstract. We present results from an intercomparison program of CO₂, δ(O₂/N₂) and δ¹³CO₂ measurements from atmospheric flask samples. Flask samples are collected on a bi-weekly basis at the High Altitude Research Station Jungfraujoch in Switzerland for three European laboratories: the University of Bern, Switzerland, the University of Groningen, the Netherlands and the Max Planck Institute for Biogeochemistry in Jena, Germany. Almost 4 years of measurements of CO₂, δ(O₂/N₂) and δ¹³CO₂ are compared in this paper to assess the measurement compatibility of the three laboratories. While the average difference for the CO₂ measurements between the laboratories in Bern and Jena meets the required compatibility goal as defined by the World Meteorological Organization, the standard deviation of the average differences between all laboratories is not within the required goal. However, the obtained annual trend and seasonalities are the same within their estimated uncertainties. For δ(O₂/N₂) significant differences are observed between the three laboratories. The comparison for δ¹³CO₂ yields the least compatible results and the required goals are not met between the three laboratories. Our study shows the importance of regular intercomparison exercises to identify potential biases between laboratories and the need to improve the quality of atmospheric measurements.