Photo of the instrument in the Jungfraujoch laboratory showing the Agilent 6890N with the thermally insulated box housing the loops and the 2-position valves at the right, the periphery box in the middle and the H₂ generator at the left.

The periphery box houses the power supplies, the actuators and the control panels of the valves, the mass flow controller and its control panel, the gas selector valve, the pump for ambient air measurements and the Nafion drier.

Photo showing the installation of the 2-position valves and the loops that are usually covered by an insulated housing.

Each ambient air sample is bracketed with calibration runs using real-air standards (working standards) with concentrations representative for Northern Hemisphere tropospheric concentrations. The real-air standards are analysed for CH₄ and CO by the World Calibration Centre (WCC) for Surface Ozone, Carbon Monoxide and Methane based on CMDL certified gas cylinders. A comparison with AGAGE standards showed an agreement well within the precision of the measurement. N₂O and SF₆ concentrations in the working standards were determined by cross-calibration with AGAGE standards.

Typical chromatogram of the FID channel (working standard with 1834.6 ppb CH₄ and 300.9 ppb CO).

Typical chromatogram of the ECD channel (working standard with 323.3 ppb N₂O and 5.85 ppt SF₆).

The four panels illustrate the whole available dataset for CH₄, CO, N₂O, and SF₆ from February 2005 to February 2007 (preliminary data). No distinct seasonal cycle and no positive trend were observed for CH₄. Also no significant trend was observed for CO. The seasonal variation in both OH concentrations and CO emissions resulted in a slight seasonal cycle with enhanced CO levels in winter. A small seasonal cycle and a positive trend were observed for N₂O in agreement with reported datasets due to annual variability in natural emissions and large-scale transport as well as human activities, respectively. SF₆ exhibits a small positive trend on a low concentration level.